Search

Experiments were conducted to determine the efficacy of coffee pulp as a constituent of a feed used in the culture of common carp ( Cyprinus carpio L.) and catfish ( Clarias mossambicus Peters). The carp were fed two commercially prepared pelleted feeds, one with 30% coffee pulp, in an earthen pond. Daily growth increments were reduced from 1.65 g to 0.34 g when fed with coffee pulp. Catfish were tested in an earthen pond, in a floating cage and in concrete tanks under variable densities. In all cases, daily growth increments were reduced by 45% or more.

A supplementary feed containing 30% coffee pulp was evaluated for use in the culture of Tilapia aurea in El Salvador, Central America. A comparison of the coffee pulp feed with a feed containing all of the same ingredients except coffee pulp was made with T. aurea raised in 1.0-m 3 cages suspended in a fertilized earthen pond. Survival was high in all treatments and there was no significant difference in average weight gain between groups of fish receiving the two experimental feeds. Production trials were conducted in 100-m 2 fish pens and in 0.05-ha earthen ponds. Pen-raised fish receiving coffee pulp feed grew faster throughout the experiment, and total production was approximately twice that in control treatments. Highest production in pens was 1.25 kg/m 2 per year. Results of production pond trials using T. aurea at 9 000/ha and stocked with the piscivorous Cichlasoma managuense yielded an estimated 3 392 kg/ha per year in fed treatments and 2 049 kg/ha per year in controls. Low feed conversion (1.92) and low feed cost resulted in an increase in net annual earnings of $251.00/ha.

The implementation of gamete cryobanking in aquaculture may improve hatchery practices such as assisted reproduction and genetic selection of desired strains. This paper preliminarily investigated the technical feasibility of cryobanking semen of the common pandora Pagellus erythrinus, an important fishery resource in the Mediterranean area and a promising species for the diversification of productions. Post-thawing motility was evaluated in common pandora semen samples cryopreserved according to eight previously selected protocols and stored in liquid nitrogen for eight years. In order to mimic the practical use of long-term cryostored semen samples, the proportion of living sperm in which motility could be activated was evaluated, by computer-assisted analysis, on thawing and after 3 h of post-thawing incubation at 18 °C as biomarker of sperm viability. The assessed parameters were percentage of motile spermatozoa (TM), curvilinear velocity (VCL), lateral head displacement (ALH), beat-cross frequency (BCF) and dance (DNC). The cryostored sperm of the common pandora proved to have promising features. In fact, percentages of motile sperm higher than 40% were always obtained on thawing; moreover, the semen retained its activation ability in the times after thawing, showing no or slight alterations in the motility profile also when activated after 3 h of post-thawing incubation. The best post-thawing performances were recorded with the EG5%-based extender under the F1 curve (equilibration at 2 °C; freezing from +2 °C to −70 °C at 3.8 °C/min), that showed the highest percentages of motile cells (80 ± 3) and no significant alterations in any of the evaluated motility parameters, followed by the EG10% based extender under the F2 curve (equilibration/cooling from 20 °C to 2 °C at 1 °C/min; freezing from +2 °C to −150 °C at 23.3 °C/min). Such a post-thawing resistance of long-term cryostored samples, encourages further studies for the inclusion of the semen of the common pandora in cryobanks aimed at use in reproductive biotechnologies for aquaculture applications and as a model in laboratory research. Therefore, the present paper contributes to the implementation of semen cryobanking as a technological tool in support to aquaculture, using as a model a species of potential aquaculture interest. In addition, the creation of germplasm cryobanks for aquatic species comply with the EU ARRIVE (Animal Research: Reporting of in Vivo Experiments) guidelines that promotes a coordinate use and sharing of biological samples from animal models in laboratory research.

In order to understand the effect of low temperature shock to Apostichopus japonicus , we measured the concentration of soluble proteins, soluble sugars and five ions (Ca 2 + , Mg 2 + , Na + , Cl − and NO) derived from different organs to evaluate the adaptive capacities and stress responses to mild temperature decrease (MTD, initial temperature was set at 14 °C and decreased from 8 °C to − 2 °C by step changes of 2 °C, temperature was decreased to each temperature through 24 h) and to rapid temperature decrease (ATD, step changes of 2 °C over 1.5 h) in the laboratory. Two commercial strains of A. japonicus , hybrid Shuiyuan No. 1 sea cucumbers (Ss) and Dalian local sea cucumbers (Ls), were used as test animals. In the MTD treatments, concentrations of soluble proteins and soluble sugars on the whole showed similar trends of an initial increase, a subsequent decrease and then an increase to a level similar to or higher than the initial level. Ca 2 + concentration increased to the maximum level at 4 °C and did not return to the original concentration. The concentrations of Mg 2 + and Cl − increased significantly to a higher level, which was maintained until the end of the experiment. However, the concentrations of Na + and NO showed an opposite trend: an initial decrease in concentration to a low concentration that was maintained until the end of the experiment. In contrast, in the ATD experiment, the concentration of soluble proteins, soluble sugars, Mg 2 + , NO and Na + showed a tendency for fluctuation or decrease. Only Ca 2 + and Cl − concentrations showed a rising trend. Earlier responses and faster homeostatic ability were observed for Ss individuals than for Ls individuals, indicating a greater cold tolerance. Such findings provide the basis for improving aquaculture techniques for A. japonicus , particularly for providing a new stress-resistant sea cucumber variety for A. japonicus culture in farm ponds. Statement of relevance The manuscript titled “Stress responses to mild and acute temperature decrease for two strains of sea cucumber Apostichopus japonicus ” was finished by Junhao Ning, Yaqing Chang, Wei Liu, Jian Song, Weijie Zhang and Jun Ding, we all made contribution to this manuscript and agreed with the authors' sorting order. This paper is first submitted in your journal. Neither the entire paper nor any part of its content has been published or has been accepted elsewhere. It is not being submitted to any other journal. We believe the paper may be of particular interest to the readers of your journal because the study reports that: (1) a preliminary relationship between the changes of soluble proteins, soluble sugars and five biogenic ions in A. japonicus and cold stress is established in the study; (2) the turning point of stress reaction in A. japonicus when suffering low-temperature was found at 0 °C or at 2 °C; and (3) we provide a new stress-resistant sea cucumber variety for A. japonicus culture in farm ponds.

This paper reports the first benchmarking of smallholder tilapia farming practices in rural northern Zambia, measuring fish growth, feed utilization and water quality parameters, using a participatory action research approach. The effects of three different feeding regimes that are currently used in smallholder farming systems in northern Zambia on the growth of the native tilapia, Oreochromis macrochir, were tested with 15 farmers (40% female), each having three ponds (one pond per feed treatment per farmer = 45 in total), over eight months in 2016–2017. The three feed treatments included: (1) formulated feed only comprising maize and soybean; (2) goat manure only; and (3) formulated feed and manure together. Three hundred (300) O. macrochir mixed-sex fingerlings, 0.5 ± 0.1 g average weight, were stocked in each pond. Water quality (pH, dissolved oxygen, and water temperature and transparency) was measured monthly, as was fish growth in each pond by randomly sampling thirty (30) fish and taking individual weights and lengths. Results showed that the water quality parameters were broadly similar in the different feed treatments over the eight-month experiment period, except for the water transparency values that were higher in the feed only treatment when compared to the other two treatments at months four through eight. Means for survival rate, weight gain, specific growth rate, total amount of fish harvested, and yield were all higher for the feed and manure together treatment than the other two feed treatments at the end of the experiment. A linear mixed-effects regression analysis that controlled for several fixed effects and included pond as a random effect found that the feed and manure together treatment increased fish growth by 10.8 ± 3.7 g at month eight compared to the manure only treatment. The analysis also found a negative effect on fish growth (−9.4 ± 3.8 g) in ponds that used the feed only treatment. The pond effect accounted for 10.1% of the total variance in the data at month eight. Future research and development efforts in Zambia should examine more closely the factors that influence fish growth and that make up the pond effect to determine which innovations and better management practices could help smallholder farmers increase the productivity of their ponds.

Despite Japanese flounder ( Paralichthys olivaceus ) is of importance in aquaculture of Northeast Asia, selective breeding programs for growth performance traits remain limited. The aim of this study was to estimate parameters of growth performance traits in this species. The heritabilities, genetic and phenotypic correlations, and breeding values were estimated for body weight (BW), total length (TL), condition factor (K), and average daily gain (ADG). The genetic analyses were performed on a total number of 186 full-sib families (108 sires and 146dams, 16,807 individuals with integrated pedigree information) from 4 year-classes based on three mixed animal models with tank and year-class as fixed effects, mean family trait values at tagging as a covariate, and additive genetic effect as a random effect using the restricted maximum likelihood method. For all growth traits the maternal and sir-dam interaction effects in proportion to phenotypic variance were very low (0.00–0.05). The heritability estimates for growth traits ranged from 0.12 to 0.39, which is in a low to moderate level. These results indicated that there is a considerable additive genetic variation in growth traits, and the ongoing selective breeding project will produce considerable genetic improvement in growth traits of Japanese flounder. The genetic and phenotypic correlations among BW, TL and ADG were high and positive (0.87–0.94, P Statement of relevance This paper offers guidelines to select breeding strategy in Japanese flounder.

When conducting digestibility experiments with fish many researchers encounter problems that result in erroneous digestibility coefficients. Erroneous digestibility coefficients result from variability in the raw data which is amplified by the formulae used to calculate them. Variation can stem from natural differences in the digestibility of the same diet between individuals or groups of fish. It can also creep insidiously into studies due to poor preparation and mixing of ingredients or problems with the collection of faecal material or the veracity of analytical results. Therefore, it is fairly common to expect variability in data collected from digestibility trials with fish. But what can be done about it? In this paper, we present an experiment with yellowtail kingfish (Seriola lalandi) that was done to determine whether the digestibility of extruded wheat (EW) was affected by its inclusion rate (10, 20, 30 or 40% diet− 1). The experiment, based on the indicator–ratio method, was conducted without incident, but the raw data on the nutrient and marker concentration of faecal samples was variable. We dealt with this problem by using linear regression to estimate more reliable analytical values for faecal samples. These values were used to recalculate logical digestibility coefficients for EW. Using this approach, we show that dry matter (≈ 57%–40%), carbohydrate (≈ 48%–27%) and gross energy (57–42%) digestibility of EW decline as its inclusion rate rises, whereas the digestibility of protein (≈ 84%) and the digestibility of fat (≈ 94%), remain reasonably constant. We validated the regression approach applied to yellowtail kingfish by examining published data from a similar digestibility experiment on Australian snapper Pagrus auratus. A regression approach was useful in reducing the variability in our raw data because the design of our experiment approximated a dose-response relationship. Designing digestibility experiments using a dose-response approach may prove useful in overcoming the inherent variability often encountered in these types of experiments.

The total water use (TWU) and consumptive water use index (CWUI) in carp polyculture under varying intensity levels [T 1 : 6000 fingerlings ha − 1 , T 2 : 8000 fingerlings ha − 1 , T 3 : 10,000 fingerlings ha − 1 ] were quantified. Treatment-wise estimated TWU was 3.71 × 10 4 , 3.92 × 10 4 and 4.34 × 10 4 m 3 ha − 1 180 d − 1 while, the CWUI was 6.38, 5.61 and 5.89 m 3 kg − 1 fish production in T 1 , T 2 and T 3 , respectively. The estimated evaporation and seepage loss ranged between 2.1–3.1 and 1.9–2.8 m 3 water kg − 1 fish production respectively and contributed significantly to consumptive water use (CWU). Treatment-wise sediment load ranged between 57.1 and 61.1 m 3 t − 1 fish biomass. Faster growth rate and biomass contribution (%) to yield was maximum by C. catla followed by C. mrigala and L. rohita in all the treatments. In this study, under best management practice (T 2 ), 1 m 3 of water produced 178 g of carp biomass and its economic value per unit of water used (USD m − 3 ) greatly exceeds that of T 1 and T 3 . Among the treatments, minimization of total water use (3.92 × 10 4 m 3 ), CWU (2.03 × 10 4 m 3 ) and water exchange (0.20 × 10 4 m 3 ) at stocking density of 8000 fingerlings ha − 1 (T 2 ), resulted in higher ( P − 1 180 d − 1 ), output value - cost of cultivation ratio (1.88), net consumptive water productivity (USD 0.15 m − 3 ) and lower AFCR (1.74). Further, farming systems with low water exchange, serves to keep the water quality suitable for the fish growth, improves water use efficiency and helps in minimizing the quantity of pollutant outputs. Statement of relevance This paper presents findings and analysis, from a methodologically rigorous investigation and provides insight regarding density-dependent optimum water use, its effect on pond water quality, sedimentation rate, growth performance and water productivity. The knowledge derived from this study may be a basis to optimize pond rearing efforts in carp polyculture and the water management strategies can be tailored to prevent wasteful use of water and enhance water use efficiency and water productivity.

This paper presents a study of controlled reproduction effectiveness of carp from the Hungarian breeding line W, one of the most valuable lines at the Golysz Institute of Ichthyobiology & Aquaculture (Polish Academy of Sciences). Ovulation was induced using: CPH (0.3 + 2.7 mg kg−1BW), CPH + Ovopel (0.3 mg kg−1 + 1 pellet kg−1), Ovopel+CPH (1/5 pellet+2.7 mg kg−1), Ovopel (1 dose: 1 pellet kg−1), Ovopel (2 dose: 1/5 + 1 pellet kg−1), hCG + CPH (1200 IU kg−1 + 1.2 mg kg−1), PMSG (2000 IU kg−1), PMSG+CPH (2000 IU kg−1 + 1.2 mg kg−1), Dagin (1 standard dose kg−1), Ovaprim (0.5 mL kg−1), mGnRH-a + MET (20 μg kg−1 + 10 mg kg−1). The highest percentage of ovulating females was recorded after administering PMSG+CPH (100%), CPH + Ovopel (81.8%) and mGnRH-a + MET (80%), while the lowest was in the case of hCG + CPH and PMSG treatments (62.5%). It was demonstrated the treatment significantly determined the weight of eggs collected (expressed in g and in % of female's body weight), fertilization rate (after 12 h incubation) and the percentage of living embryos (after 24 h and 36 h), as well as the number of eggs and number of living embryos (after 36 h). Eggs of the highest weight were collected from females treated with mGnRH-a + MET (1270 g) or Ovaprim (1230 g) (however, following the Ovaprim treatment, a considerable decrease in egg quality during incubation was recorded), while eggs of the lowest weight were collected after Ovopel (1 dose) (356 g) and after Dagin (431 g) treatments. The highest number of living embryos after 36 h incubation was recorded after administering mGnRH-a + MET, hCG + CPH, CPH and Ovaprim (667,100; 497,800; 473,100; 447,500, respectively), while the lowest was after Dagin (112, 600) and after Ovopel (1 dose) (139,800) treatments. The prediction of the number of living embryos based on the resolved regression equation was the most precise in the case of Ovopel (2 doses), PMSG+CPH, Dagin, mGnRH-a + MET and Ovopel (1 dose) treatments (R2 = 0.99; 0.99; 0.99; 0.98; 0.97, respectively), and the least precise in the case of hCG + CPH and Ovaprim treatments (R2 = 0.72 and 0.72). Based on the sum of ranks calculated for all 11 treatments and assigned to the percentage of ovulating females and the number of living embryos (after 36 h), it was found that the best scores were attained by mGnRH-a + MET, PMSG+CPH, Ovaprim and Ovopel (2 dose) treatments, while the poorest by Dagin and Ovopel (1 dose) treatments.

This study was undertaken to investigate the effects of sustained swimming exercise on the growth performance, muscle cellularity and flesh quality of juvenile qingbo fish (Spinibarbus sinensis). Experimental fish were exercised under four water velocities, nearly still (control, 3 cm s− 1) and 1, 2 and 4 body lengths (bl) s− 1, for eight weeks at 25 °C. Then, growth performance indicated by the specific growth rate (SGR), white muscle cellularity suggested by the diameter and density of white muscle fiber, flesh quality evaluated by some textural mechanical properties (hardness, springiness, chewiness, cohesiveness) and physico-chemical parameters (pH, color, moisture, ash, protein, fat, amino acids, and fatty acids) were measured. Sustained swimming at moderate velocities (1 and 2 bl s− 1) resulted in a significantly higher SGR and similar white fiber diameter and density compared with the controls. However, the fish trained at a water velocity of 4 bl s− 1 displayed a similar SGR, smaller white fiber diameter and higher white fiber density compared with the controls. Sustained swimming resulted in significant increase in the values of pH and all textural traits but showed no significant effect on the color of the flesh for juvenile S. sinensis. Fish swimming under moderate water velocities exhibited higher levels of the protein content of the muscle, total essential amino acids (∑ EAA) (at 2 bl s− 1) and total amino acids (∑ AA) (at 1 and 2 bl s− 1) compared with control fish. However, the lowest levels of total amino acids (∑ AA) and total n-6 poly-unsaturated fatty acids (∑ n-6 PUFA) were observed in fish swimming at water velocity of 4 bl s− 1. These data suggest that (1) moderate swimming exercise (1 or 2 bl s− 1) improved growth performance, which could not be attributed to changes in white muscle cellularity; (2) sustained swimming showed a positive effect on texture characteristics, which was partly due to the higher white fiber density and flesh pH compared with controls; and (3) moderate swimming exercise (1 or 2 bl s− 1) was beneficial for improving the nutritional quality of the flesh, whereas high-intensity swimming (4 bl s− 1) resulted in an impairment of the nutritional quality of the flesh in juvenile S. sinensis. Statement of relevance We declare that the experiments complied with the current laws of the country in which the experiments were performed and that our paper complied with the laws of commercial aquaculture.

In natural aquatic ecosystems, fish often experiences periods of poor food availability or complete starvation. The shortage in the feed for fish may ultimately interfere with pollutants toxicity. Therefore, a study based on a 3 × 2 factorial design was conducted to evaluate if feed availability may interact environmental zinc (Zn) effects on Nile tilapia, Oreochromis niloticus (L.). Fish (25.2 ± 0.88 g) were fed with 0.0, 0.5% body weight, or fed up to satiation with and without exposure to 5.0 mg Zn/L over 6 weeks. No significant differences were observed in water quality variables due to feed rations and/or Zn exposure except unionized ammonia concentrations, which increased as feed ration increased with Zn exposure; its highest value was observed at fish fed up to satiation with Zn exposure. Fish performance was adversely affected by Zn exposure and feed unavailability. The performance was maximized when fish fed up to satiation without Zn exposure, whereas least performance was observed at starved fish with Zn exposure. Additionally, Zn exposure elevated significantly glucose, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and creatinine values, while total protein and total lipids in fish sera were significantly lower with Zn exposure as compared to the control group. All these variables increased significantly with increasing feed ration size. The cortisol value was inversely affected by feed availability and directly proportioned to Zn exposure. It is also noticed that crude protein and total lipids contents in whole-fish body increased significantly with increasing feed ration and decreased significantly with Zn exposure. Total ash content and Zn residuals in whole-fish body were significantly highest in starved fish with Zn exposure. This study concluded that the feed availability adversely affected Zn toxicity where feed availability to appropriate ration could minimize the deleterious effect of Zn toxicity on Nile tilapia performance and health, and vice versa. Statement of relevance This paper presents data on the effect of feed availability on growth performance of Nile tilapia and its susceptibility to waterborne zinc toxicity via evaluating growth performance, whole-body measurements, and the biochemical response of Nile tilapia. Feeding fish up to satiation improved their welfare and reduced the impact of zinc toxicity and its bioaccumulation in whole-fish body and vice versa. Zinc exposure deteriorated the welfare of fasted fish or fish fed inadequate diet.

A feeding trial was conducted to assess effects of seaweed replacement by hydrolyzed soybean meal (HSBM) on growth performance, diet utilization, metabolism and body composition of sea cucumber Apostichopus japonicus . Six iso-energetic (11.39 ± 0.08 kJ/g) and isoprotein (13.62 ± 0.05 g/kg) diets were formulated by replacing 0%, 20%, 40%, 60%, 80% and 100% seaweed protein with graded HSBM levels of 0%, 4.09%, 8.18%, 12.27%, 16.36% and 20.45%. The seventh diet (S12.27%) used 12.27% soybean meal (SBM) instead of 12.27% HSBM. Triplicate tanks (40 sea cucumber per tank) were fed one of seven diets for 45 days. The results showed that growth performance of sea cucumber increased with the increase of HSBM levels from 4.09% to 12.27% while decreased as the HSBM level increased to 20.45% ( P P P P P P P P P P P P Statement of relevance Our paper provided an idea of optimizing the feed formula of sea cucumber by adding hydrolyzed soybean meal in sea cucumber culture. This optimized formula could improve diet utilization and promote growth of sea cucumber. More importantly, replacement of seaweed powder with hydrolyzed soybean meal could reduce the use of seaweed powder due to unstable supply and increased price.

Most farm animals are fasted before slaughter to empty the digestive system but in fish, the appropriate fasting time also depends on the water temperature. To analyze how the physiological and haematological response vary with degree-days (°C days), 180 rainbow trout ( Oncorhynchus mykiss ) were fasted for 1, 2 or 3 days in two different trials with water at 22.7 or 11.1 °C. In general, water temperature had a significant influence on most variables measured, although the number of degree days had a less important effect on trout physiological response, being only important in the depletion of reserves rate. The condition factor decreased at 2 and 3 days of fasting. At warmer temperatures (22.7 °C), relative weight of the gut content, hepatosomatic index and plasma levels of glucose were lower while cortisol, lactate and haematocrit were higher than at colder ones (11.1 °C). Fasting up to 68 °C days did not seem to have a negative effect on stress but a high water temperature above 20 °C was stressful for trout. Statement of relevance This paper present data on the effect of the number of degree days of fasting on body measurements and the haematological response of rainbow trout prior to slaughter. Fasting up to 68 degree days did not have a major effect on their welfare and that their haematological response was solely affected by the water temperature and not by food deprivation

The aim of this study was to test the efficacy of a new marine P ingredient from the bone fraction of herring by-products by evaluating the dietary impacts on growth, mineralization and skeletal development in Atlantic salmon fry. Five experimental diets were produced from a fish meal based diet, only differing in the dietary P source and level; low P control (5.5 g/kg soluble P), intermediate P (6.5 g/kg soluble P) and high P (8.0 g/kg soluble P) from either fish bone hydrolysate (FBH1, FBH2) or from NaH 2 PO 4 (NaP1, NaP2). The diets were given for 168 days from start of feeding (0.17 g fish) until 24 weeks of feeding (33 g). Weight and specific growth rate did not reveal diet dependent differences except in the initial 10 week feeding period where fish fed FBH1 showed lower growth as compared to fish fed the Na–P diets. Mineralization of fish evaluated by whole body and bone ash and mineral contents showed diet dependent differences that were related to dietary P level, but not to P source. Fish fed the low P diet showed clear P deficiency signs with significantly reduced tissue ash and mineral content, reduced whole body Ca:P ratio and morphological deviation from the normal. Histological evaluation of the vertebrae after 19 weeks of feeding (15 g) revealed stagnation in cartilage development, with accumulation of mature chondrocytes in fish fed low P control and FBH1 diet. FTIR showed that fish fed FBH1 had lower mineralization and increased cross binding in the vertebral end plates. Fish fed FBH2 resembled the positive NaP1 control. Real time qPCR analyses confirmed the histological results, by showing up-regulating of col10a1 (a marker for mature cartilage) in fish fed low P diet and FBH1. Osteocalcin (a marker for mineralization) was also activated in fish fed the low P diet and FBH1, possibly indicating a compensatory regulation in response to inadequate P. The dietary impacts on histology, FTIR and qPCR analyses in the FBH1 fed fish disappeared at 24 weeks of feeding (33 g). In conclusion, the results showed that P solubilized from bone fraction of herring can be efficiently utilized for growth, mineralization and bone development in Atlantic salmon fry. However, in the initial weeks of feeding, the FBH was a less efficient P source compared to NaP. Overall, the data suggest that P from fish bone hydrolysate is more suited for fish of minimum 15 g size. Statement of relevance The phosphate (P) rock reserve is a limited resource worldwide. Increased efficiency in the utilization of P and improved recycling of P from waste and manures are examples that could reduce the industry's vulnerability to the limited P supply while also reducing the negative environmental impacts. Recycling of P from fishery offal and development of new available P ingredients to farmed fish will significantly improve the sustainability of the aquaculture industry and reduce the environmental loss. In this paper we show that P hydrolysed from herring bone by-product is as efficient and good for salmon fry as commercially available NaP-salts.

Organisms exposed to sub-zero temperatures are at risk of freezing damage. Fingerling channel catfish, Ictalurus punctatus , hybrid catfish (channel catfish female × blue catfish, Ictalurus furcatus , male), channel catfish transgenic for the goldfish glutamate decarboxylase 65 gene driven by the carp β-actin promoter (βA-GAD65), and channel catfish transgenic for the catfish growth hormone gene driven by the antifreeze protein promoter (AFP-ccGH) were compared for survival at different temperatures (9.0 °C, 6.0 °C, 3.0 °C, 1.0 °C, 0.5 °C, 0 °C, and − 0.5 °C) at different salinities (0 ppt, 2.5 ppt, 5 ppt, and 7.5 ppt). The two transgenes were of interest as growth hormone not only affects growth, but also affects osmoregulation, and GAD65 construct could alter gonadotropin with the potential consequence that GnRH affects growth hormone production. Survival was 98–100% for all genetic groups at all salinities between 0 °C and 9.0 °C. However, large differences were observed at − 0.5 °C. At 0 ppt salinity, 100% of AFP-ccGH transgenic (T) fingerlings survived, but survival of all other genetic groups was 0–2%. Raising salinity to 2.5 ppt at sub-zero temperature had a strong positive impact on survival as survival rates of AFP-ccGH (T), AFP-ccGH control (C), channel catfish, βA-GAD65 (T), βA-GAD65 (C) and hybrid catfish were 100, 100, 98, 76, 100 and 18%, respectively. Increasing salinity further to 5 ppt decreased overall survival, although it was still higher than at 0 ppt. Survival rankings were altered, with means for βA-GAD65 (T), βA-GAD65 (C), AFP-ccGH (T), AFP-ccGH (C), channel catfish and hybrid catfish of 69, 0, 15, 22, 0 and 0%, respectively. Mortality was 100% in all genetic groups at − 0.5 °C and 7.5 ppt demonstrating significant interaction between temperature and salinity. Negative heterosis was observed for the hybrids at low temperature at the respective salinities. Statement of relevance We believe that this topic has not been previously addressed. These pleiotropic effects have never been described in GH transgenic or GAD transgenic fish and have relevance for aquaculture/natural resource management for future climate change as well as management and genetic management today. It is the first paper to evaluate the survival of hybrids under freezing, very important for countries that are suffering from freezing weather.

Inosine and inosine monophosphate (IMP) are the most extensively studied specific nucleotide for feeding stimulation research rather than using as functional nutrients for potential growth and health benefit of aquatic species. Therefore, a 10-week feeding trial was conducted to determine comparative effects of inosine and IMP as functional nutrients on growth performance, immune responses, stress resistance and intestinal morphology of juvenile red sea bream (Pagrus major). Casein based semi-purified basal diet was formulated to contain 54% protein, 11% lipid, without inosine and IMP supplementation (Control). Four levels of inosine nucleoside (0.2, 0.4, 0.6 and 0.8% for diet groups INO-0.2, INO-0.4, INO-0.6 and INO-0.8 respectively) and IMP nucleotide (0.2, 0.4, 0.6 and 0.8% for diet groups IMP-0.2, IMP-0.4, IMP-0.6 and IMP-0.8 respectively) were added to the basal diet. Each diet was randomly allocated to triplicate groups of fish with initial average weight of 6.6 g. The results indicated that dietary inosine and IMP supplementations tended to improve growth performances, in which one of the best ones was found in diet group IMP-0.6, but the values did not significantly differ from those in diet groups IMP-0.4 and INO-0.4, respectively. Superoxide dismutase, peroxidase and bactericidal activity were significantly influenced by dietary supplementation of inosine and IMP. However, the values of these parameters were not significantly different among diet groups INO-0.4, IMP-0.4 and IMP-0.6. Total serum protein, catalase and lysozyme activity were also improved (P > 0.05) by dietary supplementation of inosine and IMP. Supplementations improved both freshwater stress and oxidative stress resistances. Fish fed diet groups INO-0.4 and IMP-0.6 showed the least oxidative stress condition. Inosine and IMP supplementations significantly increased enterocyte height (hE), fold height (hF) of both anterior and posterior intestine and microvillus height (hMV) of posterior intestine compared to those of the control. The highest hF observed in diet group IMP-0.4 and the mean value was not significantly different from those in other IMP diets, INO-0.4 and INO-0.6, respectively. Significantly highest anterior hE and posterior hF, hE and hMV observed in diet group INO-0.4. However, no significant difference of posterior hF observed between INO-0.4 and IMP supplemented diet groups. Fish fed supplemented diets also showed improved survival compared to control (P > 0.05). Considering overall performances, it can be concluded that diet groups INO-0.4 and IMP-0.4 showed relatively better performance among inosine and IMP supplemented diet groups respectively compared to control. Furthermore, diets supplemented with either inosine or IMP at 0.4% are beneficial to promote growth, immune responses, stress resistance and intestinal health condition of juvenile red sea bream. Statement of relevance In this study inosine and inosine monophosphate has been evaluated as potential functional nutrients for marine fish such as red sea bream. Since supplementations of such immunostimulant-like functional nutrients are very important for the development of functional aquafeeds, I hope findings of this paper will help to develop low fishmeal based functional aquafeeds in near future.

In a preliminary investigation, first-year cultured northern quahogs, Mercenaria mercenaria (Linnaeus, 1758), were administered a matrix of dietary highly unsaturated n-3 fatty acids, 20:5n-3 and 22:6n-3 to observe their effect on homeoviscous adaptation to low temperature. The quahogs were subjected to high magnitude thermal fluctuations of the natural, declining temperature regime of a temperate estuary during the approach to winter. Inverse correlations emerged between mortality and dietary abundance of 20:5n-3 during the upper range of the temperature decline (18°–12 °C), and 22:6n-3 during the lower range (12°–6 °C), demonstrating their unique roles in supporting homeoviscous adaptation within each respective phase of thermal decline. High survival of a group whose diet was devoid of these n-3 fatty acids was associated with high molar % increases of endogenic non-methylene-interrupted fatty acids, 22:2Δ7,13 and 22:2Δ7,15. Conversely in the current investigation, similarly grouped juvenile quahogs all experienced reductions in incorporated 22:2Δ7,13 and 22:2Δ7,15 when subjected to a mild temperature decrease of 0.2 °C per day, suggesting that high magnitude thermal fluctuation is a signal for the synthesis of non-methylene-interrupted fatty acids. The unfavorable circumstance of this group of quahogs deprived of dietary 20:5n-3 and 22:6n-3 was exacerbated by diminishing incorporation of these compounds and suffered the earliest and highest overall mortality of all dietary treatments. High early-phase mortality of this same group was associated with high levels of previously incorporated 22:6n-3, considered to be homeoviscously unfavorable at the upper thermal range above 12 °C, and this direct relationship fell neatly within the 95% confidence interval of a linear regression model established in the preliminary study. Statement of relevance Results of this supplemental experiment provide novel correlations among thermal decline, diet and mortality of juvenile northern quahogs, distinct from the preliminary investigation cited in this paper. This work distinguishes the effects of absolute temperature decline and rapid decline on mortality of juvenile northern quahogs. This work also demonstrates the requirement of high magnitude thermal decline to signal the endogenic biosynthesis of EPA, DHA and 22:2 NMIs in juvenile northern quahogs in homeoviscous adaptation to falling temperature. Results of this work can be applied to tailor supplemental diets of northern quahog seed to prepare for forecasts of rapid thermal decline. Such timely dietary supplementation may reduce loss of bivalve seed which might improve the industries annual production and profitability.

A six-week trial was conducted to study the effects of different levels of organic carbon supplementation on biofloc color, structure and density, inorganic nitrogen and phosphorous dynamics, feed utilization and growth performance of Litopenaeus vannamei juveniles in an outdoor tank system under high-density and zero-exchange conditions. Organic carbon in the form of molasses was added daily to provide calculated carbon to nitrogen (C/N) ratios of 12:1 (CN-12), 15:1 (CN-15), and 18:1 (CN-18) based on the carbon–nitrogen content of the feed and the carbon content of the molasses during the entire experiment period No molasses was added in the control group which had a C/N ratio of 9 (CN-9). One additional treatment in which molasses supplementation was based on the actual level of total ammonia nitrogen (TAN) in the culture water (6 g of carbon was added for each 1 g of TAN as measured weekly), was also included and referred to as treatment CN-adjust. Juvenile shrimp (2.21 ± 0.11 g) were stocked into 20 experimental tanks filled with 500 L of biofloc-rich water. Each treatment had four randomly assigned replicate tanks stocked at a density of 300 shrimp m− 3. Shrimp were fed a formulated feed with 36% crude protein and cultured for 6 weeks. One week after the trial initiation, the color of suspended bioflocs began to differentiate, ranging from green to brown corresponding with the increase in C/N ratios. The higher C/N ratios shifted the predominately autotrophic biofloc to heterotrophic, simultaneously displaying higher levels of volatile suspended solids. The concentrations of TAN, nitrite-nitrogen, nitrate‐nitrogen, total inorganic nitrogen, and reactive phosphorus of all treatments fluctuated, showing a decline in total inorganic nitrogen concentration and an increase in reactive phosphorus concentration with the increase in C/N ratios. All five treatments exhibited survival rates above 95.5% with no significant differences between treatments. Better shrimp final weights and growth rates, with significantly higher yields and lower feed conversion ratio values were found for treatments CN-9, CN-adjust, and CN-12 than the CN-15 and CN-18 treatments. Three significant conclusions can be drawn from the results of this study: (1) VSS and turbidity values were superior quantifying parameters for quantitative determination of biofloc than SS or TSS in a biofloc-based system; (2) once a mature biofloc community is established, TAN and NO2−–N concentrations can be effectively controlled by either heterotrophic assimilation or autotrophic nitrification that helps maintain their concentrations at acceptable ranges for shrimp culture even at high stocking densities; and (3) the mixed type of biofloc dominated by both microalgae and autotrophic bacteria is more beneficial for shrimp performance in high density zero-exchange culture systems than systems dominated by heterotrophic bacteria, and also reduces production costs by reducing organic carbon input and oxygen use. Statement of relevance This paper provides useful info concerning the role of organic carbon supplementations in biofloc-dominated tank system operated with no water exchange and the changes in selected water quality indicators and performance of the Pacific white shrimp, Litopenaeus vannamei under these conditions.

The aim of this study was to investigate the effect of live transport of rainbow trout and subsequent live storage in an outlet aquarium on water quality, animal welfare and stress. A total of 40 fish were sampled at the following steps in the process: (1) at the raceway before transport, (2) after transport (arrival at fish outlet), (3) 24 h after fish were transferred to outlet aquarium (market), and finally, (4) after 48 h storage in the aquarium. Blood samples were collected from 10 fish at each stage and the levels of plasma cortisol, electrolytes (Na ⁺, K ⁺, Clˉ), and whole blood lactate were assessed. Twitch ability, initial pH, and temperature were assessed in white muscle. Respiration rate and swimming behavior were also assessed while the fish were kept in the outlet. Water quality (temperature, pH, dissolved oxygen, total ammonium nitrogen, total organic carbon, alkalinity and color) were assessed along with all stress measurements. Compared with fish at the farm, live transport, including effects of loading and unloading, represented the main stressor in our study. Heavy oxygen supersaturation, possibly along with elevated levels of carbon dioxide during transport contributed to this result. Despite sub-optimal water quality and excessive respiration rates, the fish in the aquarium seemed to slowly recover after transport. To reduce the effects of stress and improve animal welfare, it is suggested to minimize air exposure time and to avoid exposing the fish to supersaturated and sub-optimal levels of dissolved oxygen. Statement of relevance In a European context, selling live salmonids in the market is unusual. In this way, the highest possible freshness can be assured. However, live transport in closed systems and the live storage in fish outlets can imply risks related to compromised animal welfare and excessive stress as well as possible mortalities. In the present MS we looked into the how present handling routines and water quality affected the fish (behavior, stress and welfare). Possible improvements of present routines are discussed. We are not familiar with other published papers covering such a value chain for salmonids.

Waterless transport is an alternative method to realize the larger volume and higher survival rate of live aquatic products, this paper aims to investigate the effects of transport multi-stressors on the blood physiology and flesh quality, then optimize the setting of ambient parameters during waterless live transportation. Amur sturgeon, Acipenser schrenckii is selected as research objective because it is a representative fish of Chinese farmed sturgeon species. Fish were divided into three groups, Group I, Group II, and Group III. The fish in group I were cultured in the normal living environment (21 °C, with water), and Group II were transported in a lower temperature but normal living environment (4 °C, with water), but fish in Group III were transported in a waterless environment (4 °C, without water). Blood and muscle for assay were sampled at every 8 h intervals (0 h, 8 h, 16 h, 24 h and 32 h). The results indicate that temperature and oxygen are the critical ambient parameters in waterless live transportation, and significantly influence the fish survivability and blood physiology; blood glucose (GLU) and serum cortisol (COR) could be regarded as the representative indexes to assess the physiological stress level. Furthermore, the fish in waterless condition (Group III) exhibit no significant changes in flesh quality, such as total protein and crude fat after transport. These findings provide the theoretical evidence to understand the effects of multi-transport stressors on live fish and apply waterless transport in actual situation.

Fishmeal replacement with soy protein hydrolysate in diets for juvenile starry flounder (Platichthys stellatus) has been reported recently, but its application is limited due to high price and low yield. Whether it is feasible to replace dietary fishmeal protein (FMP) with cheap soy protein concentrate (SPC) for this fish remains uncertain. A feeding trial was conducted to investigate the effect of diets containing SPC on growth performance, oxidation resistance, health status, feed digestion and nutritional composition of juvenile starry flounder. Six isonitrogenous and isolipidic diets were formulated with SPC to replace 0% (S0, control), 20% (S20), 40% (S40), 60% (S60), 80% (S80) and 100% (S100) of FMP. Each diet was randomly assigned to triplicate tanks with 80 fish (initial weight 12.76 ± 0.2 g) per tank in a circulating water system. Fish were fed twice daily to apparent satiation for 10 weeks. At the end of the feeding trial, weight gain, specific growth rate, daily feed intake and survival rate were lower in fish fed diets S80 and S100 than in the other treatments. Feed efficiency ratio, protein efficiency ratio and condition factor were reduced by total FMP replacement (S100) compared to the control. The maximum FMP replacement for weight gain and protein efficiency ratio was estimated to be 54.86–59.02% using broken-line models. Moreover, serum lysozyme and superoxide dismutase activities decreased in fish fed diets S60, S80 and S100 versus S0, while aspartate aminotransferase, alanine transaminase and gamma-glutamyl transferase activities followed a reverse trend. Lower serum glutathione peroxidase corresponded to higher alkaline phosphatase activity in fish fed diets S80 and S100 versus S0. Serum total protein and albumin contents were reduced by total FMP replacement (S100), whereas cholesterol and low- and high-density lipoprotein cholesterol contents decreased with any diets containing SPC compared to S0. Pepsin and trypsin activities in the stomach, foregut and hindgut increased in fish fed S40 but decreased in fish fed S100. Amylase activity in the foregut was elevated by replacing at least 40% of FMP with SPC, while that in the hindgut increased with any diets containing SPC. Additionally, total FMP replacement reduced protein and fat contents but increased ash content of the whole fish compared to other treatments. These results indicated that SPC could be utilized effectively by juvenile starry flounder. FMP replacement with SPC by less than 40% is recommended for satisfactory fish growth and health. Statement of relevance Our work has proved that soy protein concentrate could be utilized effectively by juvenile starry flounder and less than 40% fishmeal could be replaced by soy protein concentrate with satisfactory fish growth and health. Present paper assesses the feasibility of replacement fishmeal with soy protein concentrate in diet for juvenile starry flounder. These results provided a basis for the formulation of a low-fishmeal diet in flatfish aquaculture.

Pollicipes pollicipes (Crustacea; Pedunculata) is a delicacy on the Iberian Peninsula where, in recent years, stock shortages associated with high market value have increased interest in the aquaculture potential of this species. Though broodstock has been maintained in captivity, detailed culture conditions are lacking. The present study investigated the effects of rearing temperature on reproductive conditioning. During a 4-week period, broodstock were subjected to temperature regimes characteristic of stable spring temperatures (spT), increasing spring to summer temperatures (sp–suT) and increasing spring to summer temperatures with daily fluctuations of 1 °C (sp–suT2). Broodstock were monitored for fecundity, egg lamella development and maturation, larval release rate, nauplius size and survival over 24 h. Cultured broodstock were fecund at smaller sizes (15.94 ± 0.23 mm RC) than wild-collected individuals at the beginning of the experiment (17.71 ± 0.65 mm RC). Fecundity increased significantly in all treatments and development of egg lamellae was highest in treatments in which the temperature increased over the experimental period (average 36% of mature egg lamellae in comparison to an initial 0%). Increasing temperature led to greater maturation of lamellae and more frequent spawning peaks. The number of nauplii released per aquarium (average 110 adult individuals) varied according to treatment and time, averaging 4670 ± 506 nauplii day− 1. Due to the low number of larvae released daily, it is suggested that adults might release larvae gradually, as embryos hatch within the mantle cavity. Average release rates increased towards the end of the conditioning period, with releases on peak days ranging from 10,000 to 30,000 nauplii per aquarium. For spT, peak values were observed in week 3, while sp–suT and sp–suT2 showed peaks of release in weeks 2 and 4, when temperatures averaged 20 and 23 °C, respectively. Temperature oscillations led to shorter intervals between peaks of release. In terms of the larvae released, there were neither differences in numbers between treatments (128,147 ± 13,548 nauplii per aquarium over 28 days) nor in size of nauplii (202.89 ± 0.69 μm GW) or 24-h survival (91.56 ± 0.35%). Notwithstanding the need for further optimization, broodstock reproductive conditioning can be accomplished and a continuous supply of larvae obtained using the protocols described herein. Future studies should focus on the impact of food quality and photoperiod on reproductive conditioning, as well as the optimization of larval release induction protocols. Statements of relevance The stalked barnacles (Pollicipes pollicipes) are considered a high-value food delicacy on the Iberian Peninsula, where interest over the culture of this species has risen in recent years. However, very little is known with regard to culture conditions. The paper addresses the effect of temperature on the reproduction in captivity of this new species to culture and establishes the first working protocol for P. pollicipes reproduction and larval collection in culture.

The main aim of this paper was to report genetic parameters and selection response from a synthetic population of Nile tilapia selected for improved growth performance in brackish water systems in Vietnam. The synthetic base population was formed in 2007 from the best performing individuals for growth produced from a complete diallel cross involving three strains of Nile tilapia, namely GIFT (Genetically Improved Farmed Tilapia), Taiwan and NOVIT4 (GIFT-derived) strains. Selection was practised for increased harvest weight in brackish water (15–20 ppt) over four generations from 2008 to 2011. A total of 12,006 individuals had performance data records. They were offspring of 341 sires and 450 dams (averaging 3000 offspring and 70 sires and 90 dams in each generation). Mixed models fitted to the data included the fixed effects of generation, sex, their two way interaction and a linear covariate of age within sex and generation. The random terms in the model were sire within generation and dam within sire and generation. The estimates of heritability for body traits and survival were moderate to high (0.27 to 0.53). Genetic correlations between harvest weight and body length were high and positive (0.97), whereas those between body traits and survival were low and not significantly different from zero. Genetic gain per generation was measured as estimated breeding values and expressed in actual units (original scale of measurement) and genetic standard deviation unit (σG). The improvement achieved for harvest weight ranged from 1.1 to 1.6 σG after four generations of selection (one year per generation). Selection for increased harvest weight was however accompanied by a non-significant decrease in survival by − 0.24%-units or − 0.16σG. The large genetic variation in both harvest weight and survival, however, suggests that there is a scope for simultaneous improvement of both traits in this population of Nile tilapia. It is concluded that our selective breeding programme has succeeded in developing a productive strain of Nile tilapia under brackish water systems, but the future work should include survival rate in the recording system, selection index and breeding objective.

The effects of water temperature at 23, 27, 31, 33 and 35 °C on growth and bioenergetics of cobia Rachycentron canadum with initial body weights about 10, 30, 70 and 200 g were investigated in this paper. Food consumption, fecal production, nitrogenous excretion, growth rate and metabolic rate of cobia were affected significantly by both water temperature and fish size. However, the relationships between food energy and feces, excretion, growth and metabolism energy exhibited linear curves and seemed independent of water temperature and fish size in the present study. For each fish size growth increased with temperature up to 33 °C and then declined at 35 °C. The optimal temperature for growth (Topt.G) of 10–200 g cobia was 33 °C. For each water temperature growth was negatively correlated to fish size and the model, SGR = a + blnW or SGR = aWb, provided a good fit to the data obtained for 10–200 g cobia. Food conversion efficiency (FCE) was highest at 31 °C and lowest at 35 °C for each size cobia. The optimal temperature for FCE (Topt.FCE) of 10–200 g cobia was 31 °C. An increasing trend of FCE with fish size was seen at each temperature and indicated that larger cobia had a superior capacity of food utilization. Energy budgets of cobia were also influenced significantly by water temperature and fish size. However, energy budgets were relatively constant over the 27-33 °C temperature and 70-200 g size ranges for cobia. Over the whole temperature and size ranges the proportion of food energy lost in feces and excretion for cobia was small (

This paper evaluates the feed cost differences in salmon farming based on two energy dense feed strategies: one resembles the industrial preference of using high-fat diets (LP: low protein-to-lipid ratio) whereas in the other strategy the dietary energy is to a greater degree derived from protein (HP: high protein-to-lipid ratio). Two different economical models are presented based on three different feeding experiments: one commercial large-scale and two small-scale trials. All trials were conducted with year old smolt (S1). Production costs have increased from 2009 to 2016, and the presented data depict a general increase in price of feed proteins and oils. Dietary proteins are more expensive than lipids and in isoenergetic diets, protein denser feeds are higher priced than the lipid dense alternative. HP diets lead to a higher feed deposition in carcass which results in a significantly lower feed conversion rate compared to the preferred isoenergetic LP commercial diets. Because of the improved feed-to-carcass conversion, the HP feed strategy yields a lower feed cost. In addition, the HP feed strategy induces faster growth that enables farmers to reduce the production cycle. A reduced production cycle represents an opportunity of reducing overall production costs. If improved growth is induced by dietary strategy, the reduction of overall costs should be assigned to the feed costs, i.e. a reduction of feed cost. Finally, dietary induced improvements in carcass weight yields more tradeable product which increases income. Thus, the present model system revealed that the traditional high-fat diets preferred in the salmon industry, although they are cheaper than the isoenergetic protein rich diets, are necessarily not precursors for overall lower feed costs.

Mortality is a major concern in larval fish rearing during exogenous feeding. An important cause of mortality of larval yellowtail kingfish (Seriola lalandi) during the rotifer - Artemia weaning period was hypothesised as being due to larval sinking response after satiated feeding prior to dusk. This paper documents the effect of larval body density change under different Artemia feeding regimes and adds to the understanding of the cause of mortality of yellowtail kingfish larvae. The change in body density was used as a tool to determine the time of last feed in a day to ensure larvae were neutrally buoyant at dusk. An adaptive Artemia feeding regime was implemented, in which the amount of feed applied to the larvae was modified based on the body density. Larvae were denser than the seawater in which they were reared when fully satiated with Artemia. The time required to return to pre-feeding density significantly decreased with larval age. At 12days post hatch (dph), the peak in body density of larvae fed Artemia to satiation was 1.0320gcm -3 and they did not return to a pre-feeding body density (1.0260gcm -3), for approximately 10h. By 19dph, larval body density only increased to 1.0275gcm -3 when larvae were fully satiated and they were neutrally buoyant again by 4h. The decrease in larval body density when fully satiated at 16dph demonstrated that overfeeding larvae with Artemia should be avoided prior to dusk before this age to maintain neutral buoyancy. The use of the adaptive regime reduced mortality by 20% compared with the control, from 13 to 17dph, without sacrificing larval growth. Transition to Artemia feeding is a critical stage for yellowtail kingfish larvae and mortalities can be significantly reduced during this period by managing the timing of Artemia feeds throughout the day. The strategy of an adaptive feeding method may be considered a novel management tool to prevent larval sinking and associated mortality during the period of weaning from rotifers to Artemia during larval rearing.

The salmon farming industry has been criticised for being a net consumer of marine resources, in the form of fishmeals (FMs) and fish oils (FOs) used in feeds. Despite the efforts made to replace FM and FO with alternatives, such as vegetable proteins and oils, the balance is still generally negative, with calculated fish in–fish out (FIFO) values often being over 4. This paper reports on a FM and FO replacement study, with maximum 20 and minimum 10% FM inclusion in high-energy, extruded salmon feeds, and in which 50% of the feed oil was of vegetable origin (rapeseed). Further, half of the dietary FO was oil reclaimed from fish processing waste (herring offal silage oil), the other half being pristine FO (blend of herring and anchoveta oils). Growth and feed utilisation were assessed in a 9 month trial, during which fish weight increased from ca. 1.2 kg to ca. 4.6 kg. There were no significant differences between feed treatments with respect to growth, feed utilisation and mortality, and replacement of FM with vegetable proteins did not compromise the bioavailability of feed nutrients. Salmon given the feed with the highest level of fishmeal replacement (FM10) had a net production of fillet protein relative to feed input in the form of protein derived from FM, indicating that FM supply is not a major factor that would impose serious limits on the quantity and efficiency of production. The inclusion of FO as 50% of the feed oils ensured that the salmon fillets contained levels of n-3 highly-unsaturated fatty acids (n-3 HUFAs) that would be considered adequate from a consumer perspective (at least 1.5 g n-3 HUFAs per 100 g fillet) and the ratio of n-6 to n-3 fatty acids (ca. 0.65) was also favourable from a human health point of view. There was net consumption of marine fish resources when assessed as FIFO calculated on the basis of the amounts of fish required to produce all FOs (FIFO 3.03–3.59) and on fish needed to produce pristine FOs included in the feeds (FIFO 1.53–1.83). Calculations based upon nutrient ratios gave positive outcomes, and salmon in all treatments deposited more fillet fat than the amount of pristine FO consumed. It is concluded that supplies of FOs impose greater limitations on the formulation of salmon feeds than do supplies of FMs. The results of the study also indicate that increased use of fish processing by-products has the potential to reduce some of the predicted short-fall in FOs resulting from reductions in the amounts of small, pelagic marine fish species rendered directly for the production of FMs and FOs.

Chronic ulcerative dermatopathy (CUD) is a disfiguring condition affecting Murray cod cultured in untreated groundwater. This study sought to further investigate the possible etiology of the syndrome and determine whether groundwater pre-treatment could suppress the development of CUD in juvenile Murray cod. Electrolyte enrichment or pre-treatment with UV irradiation delayed the onset of CUD. In contrast, pre-conditioning of groundwater either in a vegetated earthen pond or in the presence of artificial macrophytes drastically reduced both the incidence and severity of CUD, with more than 90% of fish exhibiting no visual signs. Haematology and blood parameters were assessed for future diagnostic potential, but no changes in blood parameters were observed, even in advanced CUD-affected fish. This paper identified that the treatment of groundwater via an earthen pond and in the presence of an artificial macrophyte are two highly effective methods of preventing CUD arising in juvenile Murray cod.

Mortality rates of wild spiny lobster seed Panulirus ornatus are typically high, with losses of 40–60% occurring within 30 days of capture. Mortality appears symptomatic of a micro-nutrient deficiency or captivity related stressors. Cholesterol is a micro-nutrient essential for healthy ecdysis, growth and survival in crustaceans. This paper reports a 7-week study examining the growth, survival and tissue cholesterol responses of juvenile P. ornatus lobsters fed a low cholesterol basal diet that was serially supplemented with cholesterol at 0.75 g kg − 1 increments from 1.25 to 4.25 g kg − 1 dry matter (DM). The basal diet contained 45 g kg − 1 phospholipid (from natural ingredients and supplemented soybean lecithin) and this was fed to all lobsters for 2 weeks prior to commencement of the experiment to reduce cholesterol reserves in the lobsters. A sixth diet comprising equal amounts of green-lipped mussel ( Perna canaliculus ) and whiting fillet ( Silago ciliate ) was included in the treatment array as a reference diet. One hundred and fifty lobsters were blocked by initial weight into five groups and then from within these groups they were equally distributed to 30 tanks (n = 5 tanks per treatment). There was no significant difference in survival, daily growth coefficient or tissue dry matter cholesterol content between lobsters fed the lowest and highest cholesterol diets: 55%, 349%, 243 mg 100 g − 1 and 70%, 456%, 253 mg 100 g − 1 respectively. However, there was a trend (P = 0.065) for lobster percentage weight gain to increase linearly with dietary cholesterol. There was a significant relationship between the starting weight of the lobsters and subsequent survival, with only 43% of the smallest lobsters (0.2 to 0.5 g block) surviving compared to 90% for the largest lobsters (2.71 to 3.40 g block). No specific dietary cholesterol requirement for small P. ornatus was determined. Feeds which contain practical marine proteins require no supplementary cholesterol, a significant cost saving in feed formulation. Feeds which contain high levels of plant proteins may require supplementary cholesterol to provide at least 4.0 g kg − 1 DM dietary cholesterol.

36 p., il., y bibliografía, This paper investigates the impact of different thermo- and photo-cycles of distinct wavelengths on Solea senegalensis larvae from day 1 to 30 post-hatching. In experiment 1, larvae were exposed to 12h light:12h dark (12L:12D) cycle and (A) constant temperature (20.7°C), (B) thermocycle of 12h thermophase: 12h cryophase, 22.1°C day: 19.0°C night (referred to as TC) or (C) 12h cryophase: 12h thermophase, 19.2°C day: 22.0°C night (referred to as CT). In experiment 2, larvae were kept under constant temperature (20.8°C) and exposed to (A) continuous light (LL), (B) continuous darkness (DD), and LD 12L:12D cycles of (C) white light (LDW), (D) blue light (LDB) or (E) red light (LDR). The sole larvae achieved the best performance, and showed fastest development and lowest degree of deformity under natural thermocycle conditions (TC) with a deformity percentage of 31.1% and LDB cycles with 27.7% of malformation, conditions which were nearest their natural aquatic environment. Larvae reared under TC started eye migration at 9day post-hatching (DPH), while larvae exposed to CT started eye migration at 11 DPH. In larvae under the LDB treatment the migration of the eye started earlier than in the other treatments (9 DPH), while larvae reared under LL and DD photoperiods died before metamorphosis. These findings highlight the importance of light and temperature cycles during the early development of S. senegalensis larvae, which should be taken into consideration in experimental or rearing protocols., This research was funded by the Spanish Ministry of Science and Innovation (MICINN) by projects “Circasole” AGL2007-66507-C02-02 and AQUAGENOMICS 28502 (Consolider-Ingenio Program), and SENECA by project 05690/PI/07 to Francisco Javier Sánchez Vázquez.

Spider crab ( Maja brachydactyla ) is considered a species of potential interest for intensive aquaculture, although physiological studies are necessary before the optimal conditions for its culture can be established. In this paper we develop equations to explain the oxygen consumption of the species as a function of weight ( W : 15–1414 g), temperature ( T : 13.5–27.9 °C), sex ( S ) and daily light–dark cycle (14L/10D to 10L/14D). The measurements were carried out over three days on single animals receiving one meal of mussels to satiation only on the first day of the measurements. The oxygen consumption values were divided into routine (MO 2routine ), post-prandial (MO 2sda ), maximum peak (MO 2peak ) and daily average between 0–24 h (MO 2; 0–24 h ), 24–48 h (MO 2;24–48 h ) and 48–72 h (MO 2;48–72 h ) post-feeding. Feeding led to an increase in oxygen consumption 1.7–7.3 (2.90 ± 1.25) times the routine value, with maximum peaks between 2 and 16 h post-feeding (7.94 ± 4.12 h) the effect lasting 10–24 h (19.80 ± 3.56 h). The different levels of oxygen consumption were expressed as lnMO 2routine = 0.206 + 0.837ln W + 0.302 T − 0.006 T 2 − 0.153S, lnMO 2sda = 0.294 + 0.736ln W + 1.372ln T − 0.171S, lnMO 2peak = 3.032 + 0.667ln W + 0.083 T − 0.158 S and lnMO 2; 0–24 h = 0.403 + 0.769ln W + 1.305ln T − 0.147 S , all to a statistically significant degree ( P

This study was conducted to evaluate the effects of diets including 0, 5, 10, 15, 25, and 40% alfalfa meals (containing 0, 20, 40, 60, 100, and 160 mg total carotenoids/kg diet, respectively) and 60 mg apo-ester, a synthetic carotenoid/kg diet on skin pigmentation, growth, feed utilization and survival of a red variety of goldfish, Carassius auratus, with average initial weight of 10.3 g, for a rearing period of 60 days. The pigmentation degree in skin of goldfish increased significantly with increasing inclusion of alfalfa up to 25% level in the diet (P < 0.05). However, the alfalfa inclusion over that level did not lead to more total carotenoid accumulation in the skin of fish. The diets including apo-ester and 15% alfalfa, both of which contained 60 mg carotenoid/kg diet, had similar effects on total carotenoid deposition in the skin of fish. Alfalfa addition of 25% or higher in the diet had an adverse effect on growth of fish compared to the control group (P < 0.05). A similar phenomenon was observed in feed conversion ratio but at the 40% alfalfa inclusion level (P < 0.05). However, no significant difference was observed in the survival of the fish. The present results demonstrate that alfalfa can be successfully used as an alternative natural carotenoid source to the synthetic apo-ester in goldfish diets. Our data indicates that 15% is a suitable dietary level of alfalfa to ensure good pigmentation, acceptable growth and feed utilization in goldfish. © 2008 Elsevier B.V. All rights reserved. SÜF 2002 BAP18 The authors would like to thank the Resource Fund of the University of Cukurova, (Turkey) for their financial support (with SÜF 2002 BAP18) of the experiment and Metin Kumlu and Mehmet Yücel for kindly revising the English of this paper.

A sustainable semi-intensive pond aquaculture technology including major carp species (Indian, Chinese and common carp) as cash-crop and small indigenous fish species (SIS) as food for the farmers' families is being optimized in Bangladesh. Silver carp inclusion in the polyculture is now being considered, because this very efficient filter feeder has a strong impact on pond ecology and also on the farmers' family nutrition because it is a cheap fish that the family can afford to eat instead of selling. The present paper is centered on the reduction of silver carp negative effects on other species while keeping the advantages of increased total yield and income due to silver carp stocking. It presents the results of two experiments, one on-station and one on-farm, in which 3–5 silver carp/100 m 2 were added or partially substituted major carp filter feeders. The basic stocking density was 100 carps (rohu, catla and a bottom feeder, either mrigal or common carp, at a 1:1:1 ratio) and 250 SIS (punti and mola) per 100 m 2 . In the on-station experiment silver carp density was 3 and 5 fish/100 m 2 and the large carp bottom feeder was common carp. In the on-farm experiment silver carp density was 5 fish/100 m 2 and the bottom feeder was either common carp or mrigal. Most of the water quality and fish performance parameters tested were not affected by the polyculture composition. Adding 3–5% silver carp or substituting 3–5% of the herbivorous fish species by this highly efficient filter feeder increased grazing pressure on the phytoplankton, which led to a 25–40% reduction of the chlorophyll concentration in the water column. The increased grazing pressure was not enough to affect other water quality parameters and fewer effects on the availability of food for the other fish species occurred than when the silver carp addition was 10% of the polyculture, as reported in a previous work. The strong negative effects of silver carp on the other species of the polyculture and the higher total yields and income recorded in previous experiments with the addition of 10 silver carp/100 m 2 were much weaker and their expression depended on other pond conditions when 3 or 5 silver carp/100 m 2 were added or substituted the same number of rohu or catla, either when the bottom feeder was mrigal or common carp. It was concluded that stocking 3 silver carp/100 m 2 over the usual 100 large carp and 250 SIS /100 m 2 can be considered a ‘no effect’ stocking density in relation to the control without silver carp, while stocking 10 silver carp/100 m 2 should be preferred by farmers to keep the option of selling or consuming the silver carp.

Different assays related to the first feeding of Octopus vulgaris Cuvier, 1797 are compiled in this paper. They include: age at initial feeding age, prey size selection and optimal density, attack timing after feeding, and effect of dose number on the number of captures. Prey capture and ingestion processes were also analysed. Food supplied was cultured Artemia sp. Each assay lasted 15 min. Although paralarvae already start to feed on the hatching day (day 0), it is during day 2 when a greater number of attacks is recorded (81.7 ± 14.7% paralarvae attack). They mainly prefer (significance level α = 0.05) large Artemia , 1.4 ± 0.4 mm (77.0 ± 5.6% of the total attacks) than small Artemia , 0.8 ± 0.1 mm (23.0 ± 5.6%). There is also a slight predilection for the lowest Artemia concentration (33.3 ±12.6% paralarvae attack in a 0.1 Artemia ml − 1 density, opposite 16.7 ± 7.6 and 18.3 ± 7.6% in densities of 0.5 and 1 Artemia ml − 1 respectively). The greatest predatory activity is recorded during the first 5 min after food is supplied (72.2 ± 25.5%). An increase in the predatory activity was also observed when food was distributed in several doses instead of a single dose (75.0 ± 10.0% and 46.7 ± 17.6% respectively). It was proved for the first time that paralarvae completely ingest their preys (including their exoskeletons), in this case Artemia . Time needed for their total ingestion ranges between 4 and 10 min.

An individual growth model for penaeid shrimp is presented. The main physiological processes simulated were: ingestion, assimilation, faeces production, respiration and female reproduction. The model was used to quantify the most important physiological processes involved in growth and also to examine the effect of food availability and water temperature on shrimp final weight. The simulation reproduces the typical pattern of growth of penaeid shrimp, characterised by a rapid weight gain during the early life stages and by the achievement of asymptotic length in adults. The ingestion and respiration rates increased as the animal grew but the weight-specific rates decreased with an increase of shrimp weight. A sensitivity analysis showed that the model does not produce differences at a 10% change in juvenile food availability. On the other hand, a change of water temperature of the same magnitude had an effect on shrimp final weight. The model was developed in the visual simulation software Powersim™. The individual growth model presented in this paper may be integrated into population dynamics models in order to simulate the biomass and density throughout the stages of the shrimp life cycle; such models may be usefully applied both to penaeid aquaculture and to management of wild fisheries.

In this study the genetic response to selection and the effects of inbreeding on harvest weight in two populations (which spawned as even and odd years classes) of Coho salmon are described. Artificial selection was performed using the best linear unbiased prediction (BLUP) of breeding values obtained from an animal model. Both populations were also selected for early spawning date using independent culling levels; these results are presented in a companion paper. The estimation of genetic parameters was based on the phenotypic records of 12,208 animals randomly sampled at harvest time (random group). These fish represented a mean of 64% and 48% of all animals with phenotypic records in the even and odd year classes, respectively. The narrow sense heritability estimated for harvest weight was high and very similar in the two populations, 0.39 ± 0.03 in the even year class and 0.40 ± 0.04 in the odd year class. Due to the mating design, the genetic selection differentials were 2.3 times greater in males than in females. The mean genetic selection response obtained was high in both populations, 383.2 g or + 1.26 σ and 302.4 g or + 1.23 σ per generation in the even and odd year classes, respectively. This is equivalent, on the average, to an increase in weight of 13.9% per generation compared to the base population, or 10.2% per generation with respect to the difference between successive generations. After the 4th generation of selection the mean inbreeding level was 9.5% in the even year class and 4.4% in the odd year class, which are close to preliminary estimates based on the records of the random group plus a group of animals with high harvest weight (Gallardo, J.A., Garcia, X., Lhorente, J.P., Neira, R., 2004b. Effects of nonrandom mating schemes to delay the inbreeding accumulation in cultured populations of Coho salmon ( Oncorhynchus kisutch ). Can. J. Fish. Aqua. Sci. 61, 547–553.). The estimated effects of inbreeding depression on harvest weight were negative, but not significantly different from 0 in either the even year class ( b f = − 7.04 g/Δ F , s.e. = 3.9; Mean = 4118 g; inbreeding depression per 10% of Δ F was − 1.7%; P = 0.06) or the odd year class ( b f = − 4.8 g/Δ F , s.e. = 0.33; Mean = 3243 g; inbreeding depression per 10% of Δ F was − 1.5%; P = 0.33). Other programs in salmon have selected for more than one character, however, there are still no estimates of economic weights published in salmon breeding programs, which are necessary to calculate the total genetic merit for these animals.

The larvae of the Pacific white shrimp Litopenaeus vannamei are fed with microalgae from the stage of protozoea I (PZ I), until they change to mysis I (M I). Most hatcheries use monoalgal diets based on the diatom Chaetoceros muelleri , but there is no information on the advantages of this microalga in comparison to other species used for larval feeding, supplied alone or in mixture. In this paper, the survival rate, rate of development, total length and final weight of protozoea larvae (PZ) of L . vannamei fed with the microalga C . muelleri (CHGRA) are compared to those obtained with the Tahitian clone of Isochrysis sp. (TISO) and with Tetraselmis suecica (TETRA), supplied as monoalgal and mixed diets until the stage of mysis I (M I). With TETRA, mortality was 100% before the change to PZ III, the second lowest survival until M I was with the mixture TISO + TETRA and the highest was with CHGRA as the only food source. After 114 h of culture, the best development was with CHGRA supplied alone or in any mixture (90–95% M I), the lowest was with TISO (13%) and the mixture TISO + TETRA gave an intermediate value. The larvae fed with TISO had also the lowest total length (1.8 mm), compared to the 2.5–2.6 mm found with all diets containing CHGRA. The presence of TETRA improved the food value of TISO for growth, but not for survival, whereas TISO affected the performance of CHGRA. After 114 h of culture, the larvae fed with TISO had the lowest organic weight, those fed with TISO + TETRA and TISO + CHGRA had intermediate weights and the best results were with CHGRA alone, or mixed with TETRA or with the other two species. All rations were different in weight because they were used in equal cell concentrations. In a separate experiment, TISO was supplied as a single and double daily ration because of its low individual weight, and this increased the final weight of the larvae by less than 30%, but it did not improve final survival rate, rate of development or final length. In addition, the weight gain was lower than with the CHGRA diet, showing that TISO is not appropriate for L . vannamei PZ larvae, and that a monoalgal diet based on CHGRA is a convenient option for early larval feeding of this species, possibly because of its high content of the PUFAs, EPA and ARA, and because of a low demand of DHA of these larvae. The absence of this PUFA in TETRA is a possible cause of the total mortality observed when this alga was supplied as a monospecific diet.

This paper investigates the biological responses of Crassostrea gigas under traditional culture conditions on a mudflat in Marennes–Oleron bay. Summer mortality has been regularly observed in recent years in oysters reared using “on bottom” culture conditions. The present study attempts to provide a better understanding of the mortality phenomenon through biological parameters. Classical ‘field parameters’ such as mortality and growth rates, and quality index (dry meat weight / dry shell weight × 1000) were monitored. Additional parameters, as biochemical composition of oyster meat and glucose incorporation capacity, were included as potential new bioindicators. The work highlighted a critical timing (May–June) preceding the summer mortality and characterised by an arrest in lipid synthesis and a decrease in carbohydrate content. During this period, growth (especially gonad maturation) either slowed down significantly or even stopped. The first mortality event occurred during a growth renewal period at the end of June. Short-term analysis (15 days) provided information to identify such responses which may indicate a physiological stress and demonstrating the need for further investigation. The seasonal food availability (estimated from chlorophyll a levels) did not facilitate the mortality understanding which occurred after water temperature went above 18–19 °C. Nevertheless, this study shows carbohydrate anabolism contributed in the physiological stress leading to mortality events.

This paper studied the effects of dietary protein content on growth and protease activity of Eriocheir sinensis larvae . The results suggest that if E. sinensis larvae were fed diets of different protein content, their survival, metamorphic rate and weight gain all changed significantly ( P 3 to Z 4, and the variation in weight gain of each treatment group declined gradually as the larvae developed. During the 20 h post-metamorphosis of every larval stage, the protease activity increased at Z 1 , Z 2 , Z 3 and M, and declined at Z 4 and Z 5 , meanwhile the protease activity of larvae was influenced significantly by the protein content of the diets ( P 1 , Z 2 , Z 3 , Z 4 , Z 5 and M were, respectively, 45%, 45%, 50%, 45%, 45% and 40%.

In 1997, CENIACUA (Centro de Investigaciones para la Acuicultura en Colombia) in collaboration with AKVAFORSK (Institute of Aquaculture Research, Norway) initiated a family-based selection scheme in Penaeus (Litopenaeus) vannamei to improve growth rate and survival in ponds and tanks. This paper reports results from a series of tests in which a total of 430 full-sib families (representing 204 paternal half-sib families) were tested for harvest weight and survival in standard commercial and intensive growing environments. The families originated from two selected lines. The estimates of heritability (h2±S.E.) for harvest weight for the two lines were 0.24±0.05 and 0.17±0.04, and the corresponding estimates for survival in pond/tanks were 0.04±0.02 and 0.10±0.02. Results showed a favorable correlation between the estimated mean full-sib family breeding values for harvest weight and pond/tank survival (0.42 in line 1 and 0.40 in line 2) indicating that selecting for growth will cause a positive correlated response in overall survival. The genetic correlations between body weights and pond/tank survival in different grow-out environments were high, demonstrating low genotype by farm interaction (GXE) for both traits.

This paper describes a simple method for cryopreserving sperm of the Pacific oyster ( Crassostrea gigas Thunberg) in quantities suitable for commercial spat production. Experiments to refine the cryoprotectant mixtures demonstrated the key role of trehalose. Trehalose alone (at 0.45 M final concentration) was an effective cryoprotectant. The addition of 2.5–15% dimethyl sulphoxide (DMSO) in combination with 0.45 M trehalose gave only modest improvement in fertility over trehalose alone ( p =0.056). There was no significant difference in fertility among DMSO concentrations ( p =0.611). Seawater (SW) without cryoprotectant gave very poor results, but yielded some fertilization at very high sperm concentrations (7±1% at 10 7 sperm mL −1 , 21±2% at 3.2×10 7 sperm mL −1 , mean±S.E., n =3). The fertility of unfrozen sperm was 30- to 100-fold higher than that of sperm cryopreserved with DMSO and/or trehalose. For sperm cryopreserved in 4.5-mL cryovials, two simplified freezing methods gave fertilization rates equivalent to sperm cryopreserved by controlled rate freezing ( p =0.386). These methods involved securing the cryovials to aluminium canes and then either placing them into a bath of methanol chilled with dry ice, or holding them on a floating rack 3 cm above liquid nitrogen. A third technique of plunging the cryovials directly into liquid nitrogen gave reduced and variable fertility relative to the methanol/dry ice bath method ( p =0.032). The commercial applicability of the protocols was demonstrated on a batch of 30 million eggs. Fertilization with cryopreserved sperm yielded 81% fertilization, and larval rearing by normal commercial practises yielded 3.7 million settled spat, which was comparable to the 2.5 million spat from a parallel batch fertilized with unfrozen sperm.

In the aquaculture of farmed common carp ( Cyprinus carpio L.) in Central Europe, it is believed that carp overwinter motionless and without feeding at the bottom of the ponds. However, only a few studies have investigated the behaviour of carp in winter, and data on the overwintering of carp in ponds are rare. This paper presents some new data on the activity of overwintering farmed common carp in Central European aquaculture. Altogether, 14 carp were equipped with surgically implanted radio telemetry transmitters and their activity was investigated by positional tracking in a pond (2.2 ha) during the winter seasons of 1999/2000, 2000/2001 and 2001/2002. Low weight loss, WL, and good condition factor, K , suggested that overwintering was successful (WL max.=3.8%, K =1.84–2.33). The carp were found to be relatively active in winter. The mean relative distances between the estimated fish positions on two consecutive tracking sessions ranged from 27.6 to 67.9 m. These activities correlated positively with water temperature in two winter seasons ( p

This paper reports on cryopreservation of sperm from turbot ( Scophthalmus maximus ). The effects of various extenders, cryoprotectants and sperm–egg insemination ratios on motility score and/or fertilization capacity of post-thaw turbot spermatozoa were examined to optimize cryopreservation procedures. Post-thaw motility of frozen sperm obtained with extender TS-2 was higher than those achieved with extenders D-15 and modified plaice Ringer solution (MPRS). The most effective cryoprotectant was determined to be 10% dimethyl sulfoxide (DMSO). Fertilization of small egg batches (2 ml eggs) with frozen sperm resulted in average fertilization rate (FR) (70.1±8.9%) and hatching rates (HR) (46.8±5.2%) similar to the fertilization rates (74.7±8.0%) and hatching rates (47.5±6.8%) of fresh sperm. The minimal density of frozen sperm required to obtain satisfactory fertilization rate was determined to be 2000:1 (sperm/egg). Fertilization of larger egg batches (40 ml eggs) with sperm frozen in 1.8-ml cryovials provided similar fertilization rates (71.6±7.3%) to that of the fresh sperm (76.2±5.7%), whereas the hatching rates (34.7±3.6%) of eggs fertilized with frozen sperm were slightly lower than those of fresh sperm (41.1±3.7%). Our results demonstrated that cryopreservation technique for turbot sperm in 1.8-ml cryovial could be used for hatchery purposes.

As an important step toward development of a formulated diet for hatchery culture of the mud crab, Scylla serrata, this paper reports on laboratory experiments to assess the potential of a microbound diet (MBD) as a replacement for Artemia nauplii fed to megalopal larvae of S. serrata. The effects of different proportions of dietary MBD and Artemia on survival and moulting success of megalopa to the crab stage were investigated. In the first experiment, megalopae were reared communally and fed either 100% MBD, 100% Artemia or different combinations of the two (75%:25%, 50%:50%, 25%:75%). The experiment was terminated when all larvae had either metamorphosed or died. Larvae fed a combination of 25% MBD and 75% Artemia consistently showed the highest survival among all treatments throughout the experiment. Survival of larvae fed 100% MBD was the lowest early in the experiment but improved to become the second highest toward the end of the culture period. Overall survival of larvae fed 100% MBD did not differ significantly from that of larvae fed 100% Artemia. Moulting to the crab stage began on day 7 for larvae in the treatment receiving a 50%:50% combination of MBD and Artemia. On day 8, all larvae in treatments receiving greater than 25% MBD had some first stage crabs. Larvae fed Artemia only were the last to moult to the juvenile crab stage, but moulting occurred simultaneously on day 10. Because of cannibalism observed in the first experiment, a second experiment was conducted where megalopae were reared individually and fed either 100% Artemia or 100% MBD. Ninety percent of larvae from both treatments successfully moulted to the crab stage. Again, megalopae fed MBD began moulting 1 day ahead of those fed Artemia. The results of these studies show that the MBD used contained all necessary nutrients to sustain successful moulting of S. serrata megalopae to the crab stage. The acceptability of MBD by S. serrata larvae suggests significant potential for using the MBD in future experiments to investigate larval nutritional requirements of this commercially important crab species. Indeed, the more rapid moulting of larvae fed MBD in both experiments suggests that the MBD may have contained certain beneficial nutrients that were not provided by Artemia alone. The fact that no significant differences in survival between megalopae fed 100% MBD and those fed 100% Artemia in both communal and individual rearing experiments suggests that total replacement of Artemia with MBD is possible for S. serrata megalopae. This could result in substantial savings in operating costs for S. serrata hatcheries.

In the present paper, we describe the performance of a bite-and-pull feed-demand system adapted to the behavior of European sea bass. The system is activated by the fish biting and pulling on, which generates an electrical signal that triggers the feed distributor. Experiment I was designed to test the sensor under laboratory conditions, using four groups of four naive fish per sensor (non-trained fish, NTF) and eight groups of four fish per sensor (small groups) that had been trained to use the system 1 year earlier (TF). Experiment II compared the bite-and-pull trigger (BPT) with a screened hanging-rod trigger (ST) using 16 groups of 48 sea bass per sensor (medium groups) under laboratory conditions. Experiment III evaluated the performance of the BPT sensor under farming conditions using four groups of 1000 sea bass per sensor (large groups) held in sea cages. Some of the advantages of the BPT sensor over other sensors are: (1) a shorter learning period, 11-12 days in exp. I, 1-2 day in exp. II and 1 day in exp. III; (2) absence of temporal constraints, allowing sea bass to feed at night (60% of nocturnal demands in exp. II; 23% and 47% of nocturnal demands in September and February, respectively, exp. III); (3) prevents accidental activation by fish, wind or waves; (4) low feed waste when reward level is set correctly; and (5) low costs, durability, and easy replacement of its components. All these features make the BPT a useful system for sea bass self feeding in sea cages.

Nile tilapia (Oreochromis niloticus) has rapidly become an important species for aquaculture, although their intensive culture remains constrained by poor spawning synchrony and low fecundity, adding significant cost to hatchery production. Previous research has indicated that spawning synchrony may be improved in some fish species by photoperiod manipulation. There is limited information on the effects of photoperiod manipulation on tilapia. In this paper, the reproductive performance of 32 individually housed Nile tilapia was evaluated under four different photoperiods: short day (6L:18D), normal day (12L:12D), long day (18L:6D), and continuous illumination (24L:0D). Significantly larger eggs (P less than0.05) were produced under normal daylength (12L:12D) compared to other treatment groups. Fish reared under long daylength (18L:6D) exhibited significantly higher (P less than0.05) total fecundity (2408±70 eggs spawn-1) and relative fecundity (7.2±0.2 eggs g-1 body weight) concomitant with a significant reduction in inter-spawn-interval (ISI, 15±1 days) in comparison with the rest of the trials. This investigation shows that long daylength (18L:6D) helps improve some important reproductive traits in Nile tilapia, and suggests that such methodology may be used to alleviate the production problems caused by low fecundity and poor spawning synchrony, and thus play a valuable future role in tilapia culture.

Optimal conditions for heat shock (HS) were used to demonstrate induced thermotolerance (ITT) in larvae of the prawn, Macrobrachium rosenbergii. Larvae from three different broodstock nutritional regimes exhibited comparable degrees of ITT, which remained high for about 4 days. Survival and growth of larvae given the standard HS treatment (37 °C for 30 min) were not statistically different from those of controls, so the cost of mounting a heat shock response was not sufficient to reduce those parameters. However, the percentage of heat-shocked larvae undergoing metamorphosis appeared to be slightly lower than that of controls. Previously heat-shocked larvae withstood hypersalinity exposures much better than control larvae, but showed the same survival level when both were challenged with ammonia toxicity. We suggest that the use of induced thermotolerance might provide a means to improve the performance of larvae during transport and/or initial inoculation into grow-out ponds. The present paper provides the basis upon which that suggestion might be examined.

This paper reports on experiments to determine particle size preference and optimal ration for the various larval stages of the mud crab, Scylla serrata, fed microbound diets (MBD). All experiments used 14 C-labelled rotifers as components of MBD, and ingestion was determined by assessing the 14 C content of S. serrata larvae after feeding on the MBD. Five size ranges of MBD ( S. serrata may be excessive. Little is currently known of the feeding behaviour and nutritional requirements of S. serrata larvae, and the results of this study are a significant development in this field.

This paper compares three different strategies/treatments for determining fertilization rates for producing natural foods in semi-intensive aquaculture ponds. The first strategy used a predetermined, fixed-input rate of nitrogen (N) and phosphorus (P) based on results from previous yield trials. The second strategy was based on algal nutrient concentrations, and used biweekly water quality measurements in combination with a microcomputer-based expert system, PONDCLASS©, to determine fertilization rates. The third approach, the algal bioassay fertilization strategy (ABFS), was based on algal growth responses to nutrient [i.e., N, P, and carbon (C)] enrichment, and used weekly, pond-specific algal bioassays to determine both nutrient requirements and associated rates of nutrient inputs. The three fertilization strategies were applied to Nile tilapia (Oreochromis niloticus) growout ponds over a 120-day period, with five ponds per treatment. All ponds were fertilized weekly with urea, triple superphosphate, agricultural lime, and/or chicken manure in amounts determined by each strategy. Results indicated that net fish yields (NFYs) were not significantly different (P=0.094) between treatments, with the fixed-input treatment giving the highest but most variable yields. Average NFYs±S.E. (standard error) for the 120-day growout period were 2124±276, 1476±151, and 1651±133 kg ha−1 for the fixed-input strategy, PONDCLASS©, and ABFS treatments, respectively. The relatively lower NFYs for PONDCLASS© and ABFS indicate that neither approach maximized fish production. Nitrogen utilization efficiencies of fertilizer inputs were similar for all three strategies. Although the fixed-input approach used approximately 20% more N than the other two approaches, mean algal productivities and NFYs were also proportionally higher with this treatment. This result is consistent with the observation that algal productivities in PONDCLASS© and ABFS ponds were nearly always limited by N availability. However, both P utilization and fertilization cost efficiencies were significantly better with PONDCLASS© and ABFS than with the fixed-input treatment. The fixed-input approach not only used a higher P input rate than necessary, it did not account for ecological differences between ponds within the same treatment (e.g., nutrient and light limitation of algal productivity, inorganic turbidity, etc.), which can affect a pond's response to fertilization. In particular, the fixed-input treatment did not add carbon to compensate for nonuniform losses in alkalinity, which resulted in relatively high soluble P concentrations in treatment ponds where C availability apparently limited algal productivity. Including C fertilization in the fixed-input treatment would have likely reduced NFY variability and improved P utilization efficiency in those ponds. Because both PONDCLASS© and the ABFS adjusted pond-specific fertilization requirements throughout the study, they provided increased fertilization efficiencies and profitability over the fixed-input strategy. However, the ABFS is more practical than PONDCLASS© for rural application because it is far simpler and does not require water chemistry, computers, laboratory equipment, technical expertise, or electricity to implement. Based on this study, the recommended fertilization strategy designed to achieve cost-efficient, consistently high yields is a modified ABFS approach that uses a fixed-input fertilization rate for N, and algal bioassays to determine time-specific and pond-specific fertilization requirements for P and C.

The present paper elucidates how various light regimes influence nutrients utilisation and retention during gonadal maturation in Atlantic cod (Gadus morhua). Details from the same study on population growth, gonadal development and spawning time are published by [Aquaculture 203 (2001) 51.]. During the first year, photoperiod treatments were natural light (LDN), continuous light (LL), natural light from June and continuous light from December until next June (LDN/LL), and continuous light from June and thereafter natural light from December until next June (LL/LDN). All groups were fed the same diet. There were small differences in feed conversion ratio (FCR) between groups during the first 6-month period of the experiment (June to December). In the following 6 months, FCR was highly influenced by the differences in rate and pattern of sexual maturation. The FCR was slightly higher in the LL/LDN than the LL group in this period. However, the LL/LDN group was in the middle of their spawning season when sampled in June and the spawning effect on FCR was therefore only partly realised. The low FCR of the LL group reflects that cod subjected to continuous light did not mature during the experimental period. The sexually maturing groups showed tendencies to anemia, with reduced blood hemoglobine (HB) concentration and reduced red blood cell count (RBC). The investment in gonads resulted in reduced concentrations in plasma cholesterol, triacylglycerols (TAG) and glucose, but it did not affect plasma total protein concentrations. Whole body dry matter was reduced almost linearly as gonads increased, without any correlation towards whole body lipid, but strongly correlated to reduced whole body protein levels. Cod subjected to regimes LL and LL/LDN showed significant postponed spawning. For these groups, no detectable variations in protein retention, blood, plasma or whole body compositions were found.