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Summary Sturgeons were cultured at the Solombalsky cellulose and paper plant (CPP) in Arkhangelsk over a 3 year period. The warm-water effluents of the biological treatment unit were utilized to rear the Siberian sturgeon (Acipenser baerii) and its hybrids with the sterlet (Acipenser ruthenus). Another culture trial included the Russian sturgeon (Acipenser gueldenstadtii) and its hybrids with the beluga (Huso huso). The most profitable culture (in terms of growth rates) was with the Siberian sturgeon and its hybrids with the sterlet. After the second year of culture, Siberian sturgeon and its hybrid averaged about 2.3 kg in wet weight while Russian sturgeons gained less (1.5 kg). One- and two-year old sturgeons grown at the Solombalsky CPP met practically all requirements needed for a successful culture.

A field experiment with rain-fed winter wheat investigated the nutritional aspects of paper-mill sludge as a mulch and incorporated into the topsoil. Treatments with chemical fertilizers were also used as controls. Paper-mill sludge used as mulch with high rate (100 MG ha−1) and also the combined N and K mineral fertilizer treatments increased yield when a low potassium otherwise caused potassium deficiency in wheat with high specific surface soil. High soil Ca : K molar ratio by incorporation lowered potassium uptake and yield, with visual symptoms of potassium deficiency. A very high Gapon selectivity coefficient (KG) for K exchange against Ca + Mg (16.58 (L/mole)0.5) produced a nonlinear normalized exchange isotherm in favor of potassium with these soils containing high illite. Ca and K which are released by sludge decomposition are diverged in soil when mobilized by rain infiltration, lowering Ca : K molar ratio. Low soil Ca : K molar ratio may be expected by surface sludge application relative to incorporation, due to greater rain infiltration through upper soil layers and their effluent pore volumes per unit depth. Ca from triple superphosphate by the P, N, and K mineral fertilizers combined also reduced potassium uptake and yield relative to N and K combined.

Schizopygopsis younghusbandi is an endemic fish of Tibet characterized by slow growth. Artificial stock enhancement was applied to rebuild the natural population of S. younghusbandi in recent years. However, the optimal growth temperature and thermal tolerance of S. younghusbandi has not been studied, which restricts the production of S. younghusbandi fingerling for stock enhancement. The purpose of this paper is to determine the growth, critical thermal maximum (CTMax), lethal thermal maximum (LTMax) and acclimation response ratio (ARR) of S. younghusbandi juveniles (body weight 5.7 ± 1.2 g) at three acclimation temperature levels (10, 15, 20°C). The results showed that acclimation temperature significantly affected the growth, CTMax, LTMax and ARR of the experimental fish. Largest final weight (7.5 ± 2.3 g) was recorded in 15°C group. At a heating rate of 1°C/30 min, CTMax ranged from 30.98 to 32.01°C and LTMax ranged from 31.76 to 32.31°C in the three acclimation temperatures. Schizopygopsis younghusbandi had lower ARR value (0.097) than most other fish species. Low ARR value indicates that S. younghusbandi may have narrower thermal tolerance range and weaker acclimation ability to global warming. For successful aquaculture of S. younghusbandi juveniles, temperature should be maintained around 15°C.

In this paper, the effects of temperature on the production performance values, as well as on sex differentiation and gonad development, of juvenile sterlet were investigated. For this purpose, fry were reared in the recirculating aquaculture system at three different temperatures (15, 20, and 25°C) in four replicate groups each for 140 days (10–150 dph). Fish were fed mainly with commercial diet. The growth rate in this period was significantly affected by temperature. The best performance values in terms of daily growth rate, thermal growth coefficient, and yield were registered at 20°C, indicating that this value to be near, or close to, the optimal for juvenile sterlet. Gonad samples were taken for histological analysis which revealed that the increased temperature did not cause significant differences in the sex ratio between treatments, but at 25°C resulted in significant deviation from the theoretically expected 1:1 gender ratio to favouring males. We have also found that increased temperature at 25°C accelerated germ cell development. These results indicate that rearing of sterlet juveniles at about 20°C temperature could be considered optimal both from aquaculture, as well as from species conservation viewpoints.

This paper aimed to define the reproductive period and population parameters of Serrasalmus marginatus relative to local environmental features, such as day length, rainfall and mean river level. The study site was a floodplain in the Negro river, Pantanal, Brazil, and samples were collected bimonthly using gill nets and cast nets with meshes from 1.5 to 8 cm between adjacent knots. The reproduction period, as determined by gonadosomatic index (GSI) and percentage of gonad stages, varied significantly along the year (F₄,₁₁₆ = 77.5; p

Objective. This paper aimed to analyze thein vitroindustrialized fruit juices effect plus soy to establish the erosive potential of these solutions.Materials and Methods. Seventy bovine incisors were selected after being evaluated under stereomicroscope. Their crowns were prepared and randomly divided into 7 groups, using microhardness with allocation criteria. The crowns were submitted to the fruit juice plus soy during 15 days, twice a day. The pH values, acid titration, and Knoop microhardness were recorded and the specimens were evaluated using X-ray microfluorescence (µXRF).Results. The pH average for all juices and after 3 days was significantly below the critical value for dental erosion. In average, the pH value decreases 14% comparing initial time and pH after 3 days. Comparing before and after, there was a 49% microhardness decrease measured in groups (p<0.05). Groups G1, G2, G5, and G6 are above this average. The analysis byμXRF showed a decrease of approximately 7% Ca and 4% P on bovine crowns surface. Florida (FL) statistical analysis showed a statistically significant 1 difference between groups. Thus, a tooth chance to suffer demineralization due to industrialized fruit juices plus soy is real.

Summary This paper provides the length-weight relationship (LWR) and other biological information of a threatened plateau freshwater fish species Ptychobarbus chungtienensis in the subfamily Schizothoracinae of the family Cyprinidae, from the Bita Lake of Shangri-la, in Yunnan, China. The LWR was BW = 0.00954 TL2.95 for a total of 392 individuals, where the coefficient b was close to 3.0, suggesting a near-isometric growth in this species. The total length: standard length relationship was TL = 0.399 + 1.151 SL. Fitting a von Bertalanffy growth function to the observed length-at-age data resulted in L(t) = 53.1 (1-e−0.08(t−0.2)). The natural mortality rate (M) was 0.20 year−1. Length at first maturity (Lm) was 20.57 cm, and 6.3 years the theoretical estimated age at first maturity (Am). Ptychobarbus chungtienensis mature gradually beginning in May, reaching a reproduction peak around August, with most individuals completing reproduction by October. The gonadosomatic index (GSI) was highest in August (GSI = 0.1351) and lowest in October (GSI = 0.0467). The male index (GSI = 0.0866) was lower than in females (GSI = 0.1466) (P

Dry beans (Phaseolus vulgarisL.) contain high levels of folates, yet the level of folate may vary among different genotypes. Folates are essential vitamins and folate deficiencies may lead to a number of health problems. Among the different forms of folates, 5-methyltetrahydrofolate (5MTHF) comprises more than 80% of the total folate in dry beans. The objectives of this paper were to compare selected genotypes of dry beans for the folate content of the dry seeds and to identify quantitative trait loci (QTL) associated with the folate content in a population derived from an inter-gene-pool cross of dry beans. The folate content was examined in three large-seeded (AC Elk, Redhawk, and Taylor) and one medium-seeded (Othello) dry bean genotypes, their six F1(i.e., one-way diallel crosses), and the F2of Othello/Redhawk that were evaluated in the field in 2009. Total folate and 5MTHF contents were measured twice with one-hour time interval. The significant variation (P<0.05) in the folate content was observed among the parental genotypes, their F1progeny, and members of the F2population, ranging from 147 to 345 μg/100 g. There was a reduction in the 5MTHF and total folate contents in the second compared to the first measurement. Dark red kidney variety Redhawk consistently had the highest and pinto Othello had the lowest total folate and 5MTHF contents in both measurements. A single marker QTL analysis identified three QTL for total folate and 5MTHF contents in the first measurement and one marker for the total folate in the second measurement in the F2. These QTL had significant dominance effects and individually accounted for 7.7% to 10.5% of the total phenotypic variance. The total phenotypic variance explained by the four QTL was 18% for 5MTHF and 19% for total folate in the first measurement, but only 8% for total folate in the second measurement.

Galaxias maculatus is an osmeriform native ¢sh of the Southern Hemisphere, in which the crystalline larvae is considered as a luxury delicacy, for this reason, it has been commercially exploited in Chile, Argentina and New Zealand. However, the ¢sheries have been rapidly decreasing due to the overexploitation and the predation of introduced species. Because of these events, there is a need to determine a carrying capacity for an intensive ¢sh culture. In order to optimize stocking densities for ¢sh culture, this paper proposes objectives to determine oxygen consumption (OC) rates, dissolved oxygen concentrations that produce signs of hypoxia and the average time elapsed between food intake and peak OC in G. maculatus. In the oxygen experiments under routine metabolism conditions, we found that G. maculatus adults and whitebait showed signs of asphyxia at dissolved oxygen concentrations between 1.3 and 2.2 mg L � 1 and that adults tolerated dissolved oxygen levels as low as1.3 mg L � 1 . The results showed that G. maculatus individuals with an average weight of 0.04 g consumed 0.048 mg O2 h � 1 , whereas individuals with an average weight of 1.4 g consumed 0.345 mg O2 h � 1 . Galaxias maculatus increased the OC rate by 31%, from 0.39 to 0.51mg O2 h � 1 g � 1 , occurring 14 min after food intake. The carrying capacities for industrial cultures of G. maculatus, were estimated using an allometric equation (OC 50.2363 � W 0.612 ), a water £ow rate of 1m 3 h � 1 and an input oxygen concentration of 10 mg L � 1 at 12 1C. The density culture of whitebait (4 g) can be allowed to reach 8^11kg m � 3 ; therefore, these stocking densities reduce the risk of hypoxia and mortality, ensuring the appropriate growth and feed conversion rates.

The effects of aquarium background colour and feed colour on survival, growth rates and feed utilization efficiency of thinlip mullet (Liza ramada) larvae (0.035 g) were investigated in two experiments. In the aquarium background colour trial, 50 larvae were stocked in duplicates in 120 L glass aquaria filled with dechlorinated tap water. The outside walls and bottoms of each pair of the aquaria were covered with coloured paper sheets to achieve one of six colours (white, black, red, green, yellow and blue), while noncoloured aquaria served as a control. The fish were fed an experimental diet (35% crude protein) at a daily rate of 5% of their body weight (BW), twice a day for 8 weeks. The best growth rates, feed efficiency and survival were achieved in larvae reared in light-coloured aquaria (white, noncoloured and yellow). Fish performance was significantly retarded in larvae reared in dark-coloured aquaria (red, green, black and blue). Body composition was not significantly affected by aquarium colour. In a feed colour trial, duplicate groups of larvae (0.035 g) were stocked at 50 fish per 120 L aquarium and fed a test diet (35% crude protein) with six different colours [dark blue, red, yellow, light brown (control), light green and dark brown] at a daily rate of 5% BW, twice a day for 8 weeks. The best performance and survival were achieved in fish fed on dark-coloured diets (red, dark blue and dark brown). Light-coloured diets (yellow, light green and light brown) resulted in inferior performance. Body composition was not significantly affected by feed colour. These results suggest that light-coloured tanks should be used for rearing thinlip mullet, L. ramada larvae, while dark-coloured diets are more preferable to light-coloured diets.

Summary The objective of this study was to develop a cryopreservation method in Probarbus jullieni sperm, an endangered riverine fish species in Southeast Asia, including the optimization of an extender solution (14 extender formulations were tested) and selecting a cryoprotectant (five types of agents and methanol were used at concentrations (v/v) of 5, 7.5, 9, 10, 12, 15 and 20%). The semen to diluent ratios tested were as follow: 1 : 1, 1 : 2, 1 : 3, 1 : 4, 1 : 5, 1 : 7, 1 : 9, 1 : 14, 1 : 19, 1 : 24 and 1 : 49. Vapour exposure duration was set at 5, 10, 15 and 20 min while the distance between sample and liquid nitrogen (LN2) during the vapour exposure was designed at 3, 3.5, 4, 5 and 6 cm. Further, the time frame for thawing was set at 6, 7, 8, 10, 20 and 30 s. The optimum protocol was by using CF-HBSS (pH 7.5, osmolality 285 ± 10 mOsmol kg−1) in combination with methanol at 9% (v/v); sperm to diluents ratio between 1 : 3 to 1 : 5; vapour exposure for 5 min or 10 min, with samples placed at 3.5 cm or 4 cm above LN2 and thawing at 40°C for 7 s. The mean of pre-frozen and post-thaw sperm motility was 80.1 ± 13.6% (n = 43) and 49.6 ± 16.4% (n = 43) respectively. The reproductive characteristics of P. jullieni during its spawning season were addressed in present work. Cryopreserved sperm was found to have lower fertilization ability (4.2 ± 2.5%, n = 1050) and hatching rate (1.6 ± 1.2%, n = 1050) compared with fresh sperm (fertilization 77.7 ± 6.2%, n = 1050; hatching 64.7 ± 7.7%, n = 1050). The resulted problems and constraints encountered in the process of sperm cryopreservation of the species studied were also reported in this paper.

Summary Ex situ conservation of Malaysian Mahseer (Tor tambroides and T. douronensis), the ecologically threatened freshwater fish species in Malaysia via semen cryo-banking was started in 2008 with the mature Tor species from four different locations in Peninsular Malaysia. At current stage, a total of 150 ml semen sample was collected from male fish of 73 T. tambroides and 15 T. douronensis and kept cryo-storage in liquid nitrogen (LN2) in the semen cryo-bank at Freshwater Fisheries Research Centre (FFRC). Sperm motility after cryo-preservation was found to be reduced by an average of 15 and 30% for T. douronensis and T. tambroides respectively; i.e. with pre-frozen motility 87.8 ± 7.9% (n = 73) and 88.8 ± 6.7% (n = 15), and post-thaw motility 54.9 ± 14.3% (n = 73) and 74.0 ± 11.2% (n = 15) for T. tambroides and T. douronensis respectively. The mean fertilization and hatching rates by using cryo-preserved semen in T. tambroides were 36.4 ± 10.5% (n = 360) and 34.5 ± 11% (n = 360) respectively; whereas were 89.8 ± 10.2% (n = 360) and 80.2 ± 16.6% (n = 360) respectively for fresh semen. Meanwhile, the survival rate of fry produced from cryo-preserved sperm (97.6 ± 3.1%, n = 360) was equally good (P > 0.05) when compared to the use of fresh sperm (99.7 ± 0.5%, n = 360). Sperm motility (%) during milt collection, before freezing and after thawing of each cryo-preserved semen samples was recorded. These tests were done with sperm from all semen samples and kept up to date into the Fishery Information Network System (INFOFins). The subsequent fertilization capacity and hatching rates of eggs fertilized with sperm from selected cryo-preserved semen sample were also quantified and recorded into INFOFins. Future prospects of the semen cryo-banking of Malaysian Mahseer is also reported and discussed in the present paper.

The objective of this paper is to characterize some of the sperm motility parameters in European hake (Merluccius merluccius), which is considered to be a species with aquaculture potential. The total ATP, ADP and AMP concentrations were determined using high-performance liquid chromatography on hake sperm samples collected during the winter-early spring in the Bay of Biscay (France) (n = 22) and on hake sperm samples collected during the summer-early autumn in waters off Western Norway (n = 5). The Adenylate Energy Charge (AEC) was deduced from these data. Computer Assisted Sperm Analysis (CASA) was used to measure a series of parameters characterizing the motility and the sperm swimming performances. Changes in salinity of the swimming medium affected all the measured motility parameters. The sperm velocity and the straightness of the movement were at maximum when sperm was activated with 100% filtrated sea water (100 SW) but decreased sharply later. When sperm was activated in filtrated sea water (50% diluted with distilled water: 50 SW) the values of these parameters increased (with a lower percentage of active cells) during the first 2.5 min and thereafter decreased slowly. In 50 SW, the initial velocity was lowered but the swimming period lasting 4.5 times longer than in 100 SW (but with a lower percentage of actively swimming cells). Initial sperm motility (percentage of swimming cells) in 100 SW was affected by sperm storage duration. Undiluted sperm could be stored at 4°C for 5 days and still show 13 ± 7% motility; the velocity and straightness of the movement were at maximum at the earliest period of measurement (0.5–1 day of storage) and then decreased gradually to reach their minima after 4 days of storage. Further, both the AEC and ATP content decreased with storage time, with the AEC decreasing from 0.78 ± 0.07 (mean ± SD) at stripping time to 0.20 ± 0.09 after 2 days of storage. Over the same period ATP content decreased from 85 ± 80 to 5 ± 4 nanomoles 10

This paper compares and discusses the accumulation of eight heavy metals (Cd, Co, Cr, Cu, Pb, Fe, Mn and Zn) and total phosphorus (TP) in surface sediments from five intensive farms of tilapia Oreochromis niloticus×Oreochromis aureu, Asian seabass Lates calcarifer and white shrimp Litopenaeus vannamei (n=75). Results indicate that the sediments were significantly contaminated by Cd, Co, Cr, Cu, Pb, Fe, Mn and Zn as well as P. The mean concentrations of Cd (0.47 mg kg−1), Co (2.25 mg kg−1), Cu (31.56 mg kg−1), Pb (23.45 mg kg−1), Fe (1.15%), Mn (145.5 mg kg−1), Zn (41.5 mg kg−1) and TP (750.69 mg kg−1) in tilapia farm surface sediments were significantly lower than the levels observed in Asian seabass and white shrimp farm surface sediments, where the concentrations were, respectively, Cd – 2.69 and 2.35 mg kg−1, Co – 17.66 and 15.22 mg kg−1, Cu – 116.84 and 110.03 mg kg−1, Pb – 38.5 and 33.26 mg kg−1, Fe – 3.4% and 3.31%, Mn – 853.61 and 728.5 mg kg−1, Zn – 105.21 and 83.92 mg kg−1 and TP – 1445.63 and 1069.8 mg kg−1. The heavy metal content of the sediments follow the order: Asian sea bass>white shrimp>tilapia. Cadmium and Cu in Asian seabass and white shrimp farm sediments would pose a major potential risk. Further, the sediment is highly enriched by Fe, P, Mn and Co.

Red porgy, Pagrus pagrus L., is a potential candidate for marine finfish diversification on commercial Mediterranean and Atlantic coastal aquaculture. This paper described the development of a suitable larval rearing protocol for commercial application. Red porgy eggs were reared under Intensive and Semi-intensive systems until 50 days after hatching. In addition, two different weaning protocols were tested for each rearing system. The effects of these treatments were evaluated on the growth, survival and whole-body biochemical and fatty acid composition of red porgy larvae. Significant differences in growth but not in survival at 50 days after hatching were detected in trial A for the semi-intensive and intensive rearing system (23.5 ± 2.7-18.9 ± 3.4 mm; 4.4-4.9%); however, modifications in initial prey density and illumination conditions, implemented in trials B (29.5 ± 3.0-25.2 ± 1.9 mm; 21.8-5.3%) and C (26.2 ± 2.6-24.6 ± 2.6 mm; 22.7-3.8%), significantly improved survival and growth rates in the semi-intensive rearing system. Furthermore, the results in trial C confirmed the feasibility of a partial reduction in Artemia use and the significant improvement in survival rates with the new weaning protocol applied (26.4 ± 2.3-24.1 ± 3.9 mm; 28.7-12.5%) in the intensive systems. The results of this study concluded that the best larval rearing protocol for commercial production of red porgy fingerlings should include the use of semi-intensive systems.

Photoperiod enhancement of growth is becoming an area of increasing interest as a means of enhancing rainbow trout production efficiency in commercial practice. This paper examines the possible implications of shortening periods of constant light (LL) exposure on rainbow trout growth during autumn–spring grow-out under ambient water temperatures in freshwater to portion size. Triplicate groups of juvenile all-female rainbow trout were permanently exposed to LL in October, November, December or January. Growth was monitored and compared with those maintained under a simulated natural photoperiod (SNP) until the following May. Permanent exposure to LL (all treatments) resulted in significantly greater weight gain of rainbow trout than those under SNP. Furthermore, greatest growth was achieved when fish were left permanently exposed to LL from October. These findings suggest there may be implications for fish farmers if the period of photoperiod exposure is reduced, or timing of application is not considered with regards to ambient water temperatures.

This paper describes the relationship between the egg vitamin concentrations and the egg quality in the Japanese eel Anguilla japonica. No notable relation was found between any vitamin and the fertilization rate. Hatching and survival rates of larvae, however, significantly increased with an elevated level of egg vitamin C (VC). In contrast to VC, the relation between vitamins E (VE) and A (VA) concentrations and survival rate showed a clear peak, with a reduced survival rate at both higher and lower vitamin concentrations. The ratio of VE to lipid or highly unsaturated fatty acid (HUFA) in eggs positively correlated with hatching and survival rates of larvae. High-quality (HQ) eggs were determined as eggs that produced larvae having a survival rate higher than 80% at 8 days post hatch, and low-quality (LQ) eggs were determined as eggs that did not hatch. The level of VC of HQ was significantly higher than LQ. The results of this study suggest that HQ eggs, which produce larvae having a high survival rate, must have high levels of VC and VE/HUFA ratio and contain optimum levels of VA and VE in Japanese eel.

We tested the effects of monochromatic light on the specific growth rate (SGR), feed intake and feed efficiency (FE) of juvenile pikeperch, Sander lucioperca (L.). Pikeperch were reared individually for 42 days in aquaria covered with blue, green, yellow or red gelatin filters or white paper (control; n=5). Linear regression analysis indicated a significant positive effect of longer wavelengths of light on the condition factor (CF), FE and SGR. The final weight, SGR and CF were significantly higher in fish reared under red than under white light, and FE was better under green, yellow and red light than under white light (Dunnett's post hoc test, P

Haematopoiesis and blood cells' functions can be influenced by dietary concentration of nutrients. This paper studied the effects of dietary protein:energy ratio on the growth and haematology of pacu, Piaractus mesopotamicus. Fingerling pacu (15.5±0.4 g) were fed twice a day for 10 weeks until apparent saciety with diets containing 220, 260, 300, 340 or 380 g kg−1 crude protein (CP) and 10.88, 11.72, 12.55, 13.39, 14.22 MJ kg−1 digestible energy (DE) in a totally randomized experimental design, 5 × 5 factorial scheme (n=3). Weight gain and specific growth rate were affected (P

Summary The objective of the study was to describe the biometry of Mediterranean bluefin tuna, Thunnus thynnus, the biology of which is not yet well understood. A total of 504 specimens was collected from 1998 to 2005 in the central part of the Mediterranean basin. They were sexed and measured; fork lengths (FL) ranged from 51.0 to 255.0 cm while body weights (W) ranged from 2.6 to 247.0 kg. The first spiniform ray (spine) of the first dorsal fin was removed and cross-sectioned near the condyle base in order to count annuli for age estimation. The regression coefficient (b) of the female FL–W relationship was significantly higher than that of the male, and both sexes displayed a negatively allometric growth (b < 3); male regression equation: ln W = )2.942 + 2.730 ln FL; female regression equation: ln W = )3.660 + 2.878 ln FL. Based on counts of the translucent zones in the sections of the first ray of the first dorsal fin, estimated ages ranged from 1 to 15 years for males and 1 to 14 years for females. The correlation between the spine ray (R) and FL fit the allometric model best; the R–FL regression equations of the two sexes did not differ significantly and the overall equation was: ln FL = 3.721 + 0.851 ln R. Due to the R–FL allometric correlation, estimates of fork lengths at previous ages, FLi, were back-calculated with a body proportional hypothesis. Von Bertalanffy growth equations were derived from both observed and back-calculated FLs-at-age, which did not differ significantly. Moreover, no significant difference was found between the growth equations of the two sexes; the overall equation was FLt = 373.08 [1)e )0.07(t + 1.76) ]. Weight-at-age values were derived from the von Bertalanffy predicted FLs-atage by the FL–W correlation equations for males and females. The paper represents the first comprehensive study on the biometry, including age and growth, of bluefin tuna captured in the Mediterranean Sea.

The metabolic physiological response to body mass, temperature (12-28 °C) and salinity (20-36 g L⁻¹) was examined in this paper. Oxygen consumption rate, which is dependent on environmental conditions, was exponentially related to body mass and varied from 0.045 to 1.11 mg h⁻¹ g⁻¹. Oxygen consumption rate increased as salinity increased from 20 to 36 g L⁻¹, and increased with increasing temperature. The effect of temperature gradient between experimental treatments on oxygen consumption rate was evaluated by calculating Q₁₀ (the Arrehenius relationship for increase with temperature). The Q₁₀ value within the temperature range from 12 to 16 °C was much higher than the value within the temperature range from 16 to 20 °C, 20 to 24 °C and 24 to 28 °C, indicating a reduced temperature dependence of ascidian metabolism at a high temperature.

This paper reports on experiments conducted to examine the combined effects of salinity and potassium concentration on survival and growth of juvenile mulloway (Argyrosomus japonicus, Temminck and Schlegel) in inland saline groundwater. Three separate experiments were conducted in 20 (±1)°C water. In the first experiment, mulloway were held in 60 L aquaria (triplicate) with salinities of 5, 15, 25 or 35 g L−1 and potassium concentrations of 20%, 40%, 60% or 80% of the concentration present in oceanic water of the equivalent salinity in a 4 × 4 factorial combination for 7 days. Response surface contour diagrams were generated from survival data to estimate optimal conditions. The results showed that maximum survival of juvenile mulloway occurred at salinities of >14 g L−1 and potassium concentrations of >38%. Survival was lowest at salinities of 33 g L−1 and potassium concentrations of

The tongue sole Cynoglossus semilaevis, an inshore fish in China, has showed great potential in aquaculture recently. However, poor survival was recorded during the period of weaning from live Artemia to artificial diets. In this paper, the influence of co-feeding larvae with live and inert diet on weaning performance was described. The C. semilaevis larvae were reared at 21 ± 1 °C and fed four different feeding regimes from 6 days post-hatching (dph): A, Artemia (10 individuals mL−1); B, Artemia (5 individuals mL−1); C, mixed diet (10 Artemia individuals mL−1 and 12 mg L−1 inert diet); and D, mixed diet (5 Artemia individuals mL−1 and 12 mg L−1 inert diet). Rotifers were also supplied in all cases during the first days of feeding. Mixed diets of commercial formulated feed and live prey (rotifers and Artemia) allowed larvae to complete metamorphosis, achieving similar specific growth rate (SGR) (18.5 ± 1.4% and 18.7 ± 1.6%) and survival (40 ± 7.6% and 48.5 ± 6.8%) compared with larvae fed on live feed alone (SGR of 18.3 ± 1.2%, 19.3 ± 1.9% and survival of 41.2 ± 11.3%, 38 ± 4.9%). However, in metamorphosed fish, when live feed was withdrawn on 31 dph, there was significant difference (P

Summary The paper presents the results of investigations on the feeding of bream larvae reared in illuminated cages in a mesotrophic lake. The same species of zooplankton were found in both the lake and the fish cages. Copepoda predominated in abundance and biomass. During the mixed feeding the bream larvae diet consisted of rotifers (45.8%), small cladocerans (41.6%) and phytoplankton (13.6%). According to Ivlev's selectivity indices (E), the most important food species were: Keratella cochlearis (E = +9.94), Kellicotia longispina (E = +0.93), K. quadrata (E = +0.92), Bosmina longirostris (E = +0.92), Trichocerca sp. (E = +0.89), and Chydorus sphaericus (E = +0.88). The total length (TL) of bream larvae consuming their first nauplii and copepodites of Copepoda was 8.9 mm. As bream larvae grew, cladocerans were more often selected than rotifers. Copepods usually made up an insignificant component of the diet. Bream larvae in illuminated cages generally fed at night; their alimentary tracts were filled to the maximum in the period from sunset to sunrise. Indices thereof reached 755.6 at night and 278.0 ? in the daytime.

To investigate the effects of body size and water temperature on feeding and growth in the sea cucumber Apostichopus japonicus (Selenka), the maximum rate of food consumption in terms of energy (C-maxe; J day(-1)) and the specific growth rate in terms of energy (SGRe; % day(-1)) in animals of three body sizes (mean +/- SE) - large (134.0 +/- 3.5 g), medium (73.6 +/- 2.2 g) and small (36.5 +/- 1.2 g) - were determined at water temperatures of 10, 15, 20, 25 and 30 degrees C. Maximum rate of food consumption in terms of energy increased and SGRe decreased with increasing body weight at 10, 15 and 20 degrees C. This trend, however, was not apparent at 25 and 30 degrees C, which could be influenced by aestivation. High water temperatures (above 20 degrees C) were disadvantageous to feeding and growth of this animal; SGRe of A. japonicus during aestivation was negative. The optimum temperatures for food consumption and for growth were similar and were between 14 and 15 degrees C, and body size seemed to have a slight effect on the optimal temperature for food consumption or growth. Because aestivation of A. japonicus was temperature dependent, the present paper also documented the threshold temperatures to aestivation as indicated by feeding cessation. Deduced from daily food consumption of individuals, the threshold temperature to aestivation for large and medium animals (73.3-139.3 g) was 24.5-25.5 degrees C, while that for small animals (28.9-40.7 g) was between 25.5 and 30.5 degrees C. These values are higher than previous reports; differences in sign of aestivation, experimental condition and dwelling district of test animals could be the reasons.

The present paper represents a part of a major scientific effort aiming to reveal possible effects, nutritional or health related, of genetically modified (GM) feed ingredients for Atlantic salmon. For 3 months groups of post-smolt Atlantic salmon were treated with diets holding 130 g kg1 of the protein as soybean, one which contained 800 g kg(-1) GM type RR (Roundup Ready), and compared with a standard counterpart (commercial hybrid, not isogenic line) analysed to be non-GM (nGM), and again compared with a standard fishmeal diet without soybean protein. All diets were composed to be within the category 'compositional equivalent' and held exactly the same proximate compositions, starch and sugar levels, above requirements for methionine and lysine, equal fatty acid profiles, vitamin, mineral and pigment contents. There was, however, a slight difference in levels of anti-nutrients between the three diets. The various dietary treatments resulted in more than tripling of fish weight in all groups. In addition no significant differences in feed utilization, whole body, liver and muscle proximate compositions, and no significant differences in muscle fatty acid profiles were measured. The diet without soybean of either type resulted in greater retention of lipid, but equal retention of protein (protein productive value). The relative sizes of liver, kidney, head-kidney and brain were the same in all dietary groups, while the relative size of the spleen showed significant differences between fish fed the genetically modified soy diet compared with fish fed the nGM soybeans. Fish fed the soy diets of either type also showed a somewhat reduced mean erythrocyte cell volume. All other haematological values were equal between diet groups. The detoxification system, measured as glutathione peroxidase (GPx) and lysozyme activities, showed equal values for all groups when measured in plasma and liver or head-kidney. The distal part of the intestine showed reduced sizes as an effect of soybean additions, without any differences between the GM and nGM type. Our results showed high growth, no mortality, haematological values within normal ranges, and efficient and equal responses in the detoxification system. This was a first indication that up to 130 g kg(-1) RR-soybean protein can safely be used in diets for Atlantic salmon. However, there is still a need to elucidate higher inclusion levels of GM feed ingredients, and why spleen index was reduced, and if this was a long- or short-term effect.

Peneid shrimp are commonly reared in clear-water aquaria or tanks for short-term studies of 4-6 weeks during controlled experiments, such as nutrition studies to estimate dietary nutrient requirements. Recently, in line with the genetic program at Centre Oceanologique du Pacifique (COP), experimental clear-water facilities were tested for the first time over a longer rearing period. Environmental conditions used to maintain animal growth in clear-water system using a well-balanced diet were defined. After 100 days, shrimp growth rates tended to decrease and only by adjusting the diet could shrimp complete their life cycle and reach maturation size of around 40 g. This paper presents information on stocking density, diet quality and husbandry linked to reproduction that must be considered to successfully rear animals from PL's to breeder size in clear water. By following these protocols a minimum amount of breeders can be used to meet production goals. Moreover, by isolating a small group of individuals, genetic diversity can be preserved, thereby allowing specific crosses for selective breeding purposes. Length of trials, amount of feed, composition of feed, growth performances and maturation success are reported and should encourage further studies to optimize rearing conditions in clear-water rearing.

The present paper assesses the fertilization and hatching rates of an artificial fertilization series (n=1153) using fresh and cryopreserved sperm from 49 specimens of turbot Scophthalmus maximus (L.), carried out to confirm the results of a previous study, with the ultimate aim of transferring these cryo-preservation techniques to commercial hatcheries. No significant differences were found between the fertilization rates of the two groups (fresh and cryopreserved sperm) when their respective fertility rates were >69.2%, which was the case in 75% of all fertilizations. Likewise, no significant differences in hatching rates were found. In order to use the cryopreserved sperm more efficiently, a key concern for commercial use of this technique, we also experimented with a lower sperm:diluent ratio (1:1) than used previously at our centre. We also compared the traditional 0.5-mL straws with 2-mL cryotubes able to contain a higher volume of sperm, finding no significant differences in the resulting fertilization and hatching rates. In conclusion, the use of cryopreservation for turbot sperm presents major advantages for broodstock management in commercial hatcheries.

Summary Effective pond production of tench [Tinca tinca (L.)] requires the use of formulated diets. However, insufficient information is available regarding the nutrition of this species. Therefore, for the first time, the digestibility of macronutrients by tench was investigated using a sieving method of faeces collection and chromic oxide. A pelleted experimental diet rich in untreated wheat starch revealed the following mean apparent digestibility coefficients (ADCs): dry matter 77.2%, crude protein 89.4%, crude fat 94.3%, ash 30.5%, nitrogen-free extracts 78.2%, organic matter 83.3% and energy 85.1%. Generally, these ADCs indicate that the ability of tench to digest the macronutrients from pelleted feed correlates with reports of other fish species. However, the tench is more able to digest untreated wheat starch than are carnivorous and coldwater fish species. Compared with carp (Cyprinus carpio L.), the digestibility of untreated wheat starch is less in tench. The faeces sieving method as described in this paper is a useful procedure for further digestibility trials with tench. However, compared with the approach presented here, several adaptations are recommended, e.g. long adaptation times to the rearing facility, high stocking densities, usage of more waterproof food pellets and the addition of formalin to the collection pans.

Because European sea bass (Dicentrarchus labrax L.) has strictly carnivorous feeding habits, protein and fat are the most important dietary components. In this paper we study the effect of restricted availability of protein and fat on the feeding behaviour and macronutrient selection. To this end, five groups of 20 sea bass with a body weight of 100.0 ± 20.1 g (mean ± SD) were raised in five circular 450-L tanks. Each group could choose among three self-feeders (experiment 1 and 2), each containing a different, incomplete, diet: P + CH (55.4% protein, 18.5% carbohydrate, DM diet), P + F (55.4% protein, 18.5% fat) or F + CH (36.9% fat, 36.9% carbohydrate) or between two self-feeders (experiment 3), each containing protein (100%) or carbohydrate–fat (52.7% and 47.3% respectively). In experiments 1 and 2, sea bass selected a diet consisting of 65.3% digestible energy (DE) protein, 26.2% DE fat and 8.4% DE carbohydrate. The composition of the self-selected diet did not differ when sea bass selected between the two diets in experiment 3. When fish were deprived of protein for two weeks, or deprived of fat for three weeks, they were unable to sustain their previous energy intake. This phenomenon was particularly evident during protein fasting, with the intake of fat and carbohydrate being negligible. During the first 2–3 days, after each fasting period, sea bass showed hyperphagic behaviour, but restricted availability of specific nutrients did not trigger any subsequent increased intake of these specific macronutrients. In conclusion, although sea bass were able to self-compose a nutritionally balanced diet from three or two incomplete diets, no specific hunger was elicited after two weeks of protein fasting or three weeks of fat fasting.

A total of 200 milk samples from cattle ( 𝑛 = 8 6 ) and buffalo ( 𝑛 = 1 1 4 ) were evaluated using milk ring test (MRT) and indirect enzyme-linked immunosorbent assay (i-ELISA). The overall prevalence was found to be 3% and 8.5% in cattle and buffaloes using MRT and i-ELISA, respectively. The prevalence was 4.6% and 1.7% in cattle and buffalo using MRT, respectively, while i-ELISA exhibited 20% and 0% in cattle and buffalo, respectively. The prevalence was higher in government dairy farm, compared to privately owned dairy farm. This paper points out an alarming situation in the target area with respect to the public health significance.

Background. Cancer is a significant disease burden in the world. Many studies showed that heavy metals or their compounds had connection with cancer. But the data conflicting about the relationship of manganese (Mn) to cancer are not enough. In this paper, the relationship was discussed between Mn concentrations in drinking water for rural residents and incidence and mortality caused by malignant tumors in Huai’an city.Methods. A total of 158 water samples from 28 villages of 14 towns were, respectively, collected during periods of high flow and low flow in 3 counties of Huai’an city, along Chinese Huai’he River. The samples of deep groundwater, shallow groundwater, and surface water were simultaneously collected in all selected villages. Mn concentrations in all water samples were determined by inductively coupled plasma-mass spectrometry (ICP-MS 7500a). The correlation analysis was used to study the relationship between the Mn concentration and cancer incidence and mortality.Results. Mn concentrations detectable rate was 100% in all water samples. The mean concentration was 452.32 μg/L ± 507.76 μg/L. There was significant difference between the high flow period and low flow period (t=-5.23,P<0.05) and also among deep groundwater, shallow groundwater, and surface water (F=5.02,P<0.05). The ratio of superscale of Mn was 75.32%. There was significant difference of Mn level between samples in the high flow period and low flow period (χ2=45.62, P<0.05) and also among deep groundwater, shallow groundwater, and surface water (χ2=10.66,P<0.05). And also we found that, during the low flow period, Mn concentration has positive correlation with cancer incidence and mortality; for a 1 μg/L increase in Mn concentration, there was a corresponding increase of 0.45/100000 new cancer cases and 0.35/100000 cancer deaths (P<0.05).Conclusions. In Huai’an city, the mean concentration of Mn in drinking water was very high. Mn concentration correlated with cancer incidence and mortality.

The present paper assesses the fertilization and hatching rates, as well as the growth, of larvae obtained from four artificial fertilizations (AF) using fresh and cryopreserved sperm of the turbot Scophthalmus maximus (L.). Larvae growth in both sperm groups, measured in terms of length and weight at culture days 0, 7, 14 and 31, are compared, as well as their growth rates. The two groups' fertilization and hatching rates were not significantly different. Likewise, no significant differences in length and wet weight of 7- and 14-day-old larvae were found using fresh and cryopreserved sperm; however, significant differences were found in 31-day-old larvae, which were more attributable to the variability inherent in larval turbot culture, and to variability in the reproductive specimens used in our study, than to the type of sperm employed. These results indicate that the type of sperm used in artificial fertilization, i.e. fresh or cryopreserved, is not a determining factor, either for fertilization and hatching, or for subsequent larval development. Our results also confirm once again the high quality of cryopreserved turbot sperm, and its usefulness in commercial hatcheries.

This paper reports on two factorial design experiments conducted to examine the combined effects of algal ration and larval density on growth and survival of black lip pearl oyster Pinctada margaritifera (L.) larvae. In the first experiment, 1-day-old larvae were cultured for 7 days at densities of 1, 2 and 5 mL−1 and fed algal rations of 0, 2.5, 5 or 12.5 × 103 cells mL−1. In the second experiment, 13-day-old larvae were cultured for 7 days at the above densities and fed algal rations of 0, 7.5, 15 and 37.5 × 103 cells mL−1. Algal rations in both experiments were composed of a 1:1 mixture of the flagellates Isochrysis aff. galbana clone T.ISO and Pavlova salina. Response surface contour diagrams were generated from growth and survival data to estimate optimal culture conditions. Results showed that, within a suitable larval density range, growth of P. margaritifera larvae was significantly (P

The present paper describes sex reversal in dusky grouper, Epinephelus marginatus (Lowe). Over a 4-month feeding period, 5 mg kg−1 of the male hormone 17-α methyltestosterone was combined with frozen fish as feed. After 2.5 months of treatment, the gonads of all six fish treated in the experiment presented tissues with oocytes and spermatogonia, and after 3 months, there were only a few remnants of oogonial tissue left in the gonads. All fish in the experiment gave sperm of varying quality after 4 months of the trial. The quantity of the hormone administered to the fish over these 4 months was 89-113 mg kg−1. Spermatozoid motility varied from 95% to 40%, and lasted for about one hour in sea water. Using the combined sperm of three males, fertilization ranged from 50% to 95%. Fertilized eggs and hatched larvae continued to develop normally.

In the present paper, the results of a study on changes in the proximate and amino acid composition of the eggs and larvae of two Australian native Percichthyid fish, Macquarie perch, Macquaria australasica Cuvier, and trout cod, Maccullochella macquarensis (Cuvier), are presented. The stages of development studied were unfertilized and fertilized eggs, newly hatched larvae, and post-yolk-sac larvae (in Macquarie perch only). In Macquarie perch, significant changes in moisture content occurred throughout development, but this was not so in trout cod. The protein content (per cent dry weight) in Macquarie perch larvae only decreased significantly after hatching (P < 0.05). On the other hand, the total lipid (by dry weight) increased significantly during this transformation (P < 0.05), and decreased significantly in yolk-sac-resorbed larvae. In trout cod, the protein and lipid content did not change significantly up to hatching. The ash content increased significantly in newly hatched and yolk-sac-resorbed larvae of both species. The total amino acid contents of unfertilized eggs, fertilized eggs, newly hatched larvae and yolk-sac-resorbed larvae of Macquarie perch and trout cod were 5752, 4652, 3696 and 2723 μmol g−1 (dry weight), and 4688. 3448 and 2329 μmol g−1, respectively. In the amino acid pool in Macquarie perch, the essential amino acids (EAAs) leucine, isoleucine and valine, and the non-essential amino acids (NEAAs) alanine, aspargine and glutamate occurred in the greatest quantities in non-fertilized eggs, and the cysteine content was the smallest. In Macquarie perch, five out of nine EAAs (i.e. isoleucine, leucine, lysine, threonine and valine) and six out of eight NEAAs (i.e. alanine, asparagine, glutamate, glycine, proline and serine) decreased significantly (P < 0.05) from one developmental stage to the other. In trout cod, all the EAAs, barring lysine and all the NEAAs decreased significantly with development.

The processing of 232 common carp Cyprinus carpio made it possible to study the correlation between gonad maturation and filleting yield. The study was undertaken between April and August 1992 and was carried out on 4-year-old carp cultured in extensive ponds. Morphological parameters were recorded and relations between total weight and length, biomass of fillet, and biomass of gonad were determined. The histology of male and female gonads was examined in relation to the gonadosomatic index (GSI: up to 16% for females and less than 11% for males) and condition indices (total K or somatic K1). Filleting yields (32–36% of the total weight) decreased for females just prior to spawning and corresponded to a decline of K1. A rematuration phenomenon was observed, although females weighing less than 1200g were still immature. We suggest avoiding the filleting of large females before spawning and suggest estimating the date of appearance of this stage by referring to the positive correlation established in this paper between the number of degree-days and total fish weight.

Microtagging is an adequate method of ensuring correct recapture estimates in enhancement of natural lobster, Homarus gammarus (L.), stocks through releases of cultured juveniles. This paper compares three lobster size categories (8-10, 12-14 and 16-18 mm), two tag lengths (0.5 and 1.0 mm), and two methods of holding the animal during marking with respect to tag retention and survival. A total of 1721 individuals were used in the experiment. The results did not reveal any obvious trends in tag retention related to either different tag lengths or different lobster sizes. Lobster held laterally during tagging showed higher tag retention (94-99%) than lobsters held with the ventral side uppermost (74-97%). Examination, using X-ray, of 81 juveniles which had tested negative for the presence of tag by the magnetic sensing device, showed that four of these in fact had tags. This suggests that the true tag retention figure could be higher than shown in the results. The cumulative mortality ranged from 0 to 4.7% after 3 days, but only for the smallest animals marked with 1 -mm tags laterally: this was significantly higher than in the control group. After 20 days, the cumulative mortality ranged from 0 to 5.7%. but there were no significant differences between experimental and control groups.

The expansion of freshwater cage culture in Scotland during the 1980s led to concern with respect to the impact of nutrient, particularly phosphorus (P), discharges on water quality in lakes. The primary route by which P enters the aquatic environment from cage farms is through the feed administered to the fish. In recent years, there have been considerable technological advances in feed manufacturing and improved feeding practices at farm level. This paper investigates how P inputs to freshwater lakes from cage farms may be reduced through changes in diets and improved food conversion ratios. The results demonstrate that there has been a significant improvement in the P content of freshwater trout diets in recent years and that it is possible to reduce waste P loadings from cage sites through the use of better-quality diets and improved feed management. In Scotland, production levels in freshwater cages are commonly set by the regulatory authority assuming a soluble waste P loading of 10 kg P tonne−1 of fish produced. This study suggests that actual soluble waste P loadings are likely to be far lower than this and that, as a result, increases in water column total P levels may be overestimated.

Atlantic salmon, Salmo salar L., were fed nine experimental diets containing from 0 to 200 mg astaxanthin per kg−1 for six time periods, ranging from 3 to 21 months, in sea cages at Matre Aquaculture Research Station, Matredal, Norway. The sampled fish had an initial mean weight of 115 g and reached a weight of 3.2 kg at the termination of the experiment. Every third month, 10 fish from each dose and time group were sampled and the astaxanthin concentration in the flesh determined. The amount of astaxanthin in the flesh ranged from 0.7 to 8.9 mg kg−1 at the termination of the experiment. This paper discusses deposition of astaxanthin in the flesh of Atlantic salmon in relation to dietary carotenoid levels in the 0–200 mg kg−1 range and feeding times of 3–21 months. Under the conditions of this experiment, no significant effect on astaxanthin deposition rate could be achieved by increasing the astaxanthin level above 60 mg kg dry feed−1. Atlantic salmon should be fed astaxanthin-supplemented diets during the whole seawater stage in order to obtain maximal astaxanthin level in the flesh.

The relative weight of fish eggs increases during water hardening; this increase is significantly correlated with egg viability in rainbow trout when determined after 120 min, providing an assay test for egg quality control. In the present paper, additional investigations on egg water uptake at different time intervals during the hardening process were performed to correlate these with egg viability and to improve the sensitivity of the assay while also reducing the handling time. Eggs of high quality had a significantly higher rate of water uptake than low quality eggs, with the highest rate occurring during the first 30 min of hardening. Bivariate correlation coefficients and regression models revealed that in addition to egg weight increase after 120 min of water hardening, the increases in weight after 30 min and 60 min were also significantly related to egg viability (P

In mammals, lipemic blood from sampling too soon after an animal feeds can have substantial effects on biochemical values. Plasma biochemical values in reptiles may be affected by species, age, season, and nutritional state. However, fasting status is not routinely considered when sampling reptile blood. In this paper, we evaluated 2-hour postprandial blood collection in two sea turtle species to investigate the effects of feeding on hematological and plasma biochemical values. Feeding had no significant effects on hematological values in either species, nor did it have an effect on plasma biochemistry values in Kemp's ridley sea turtles. In postprandial green turtles, total protein, albumin, ALP, AST, ALT, amylase, and cholesterol increased significantly, and chloride decreased significantly. Although statistically significant changes were observed, the median percent differences between pre- and postprandial values did not exceed 10% for any of these analytes and would not likely alter the clinical interpretation.

The common sole, Solea solea (L.), readily spawns naturally in captivity. This paper reviews the conditions and procedures used to obtain natural spawning from captive broodstocks and describes the characteristics of egg production. Spawning has been obtained under a wide range of conditions. The time of year has varied, even at the same location, but analysis of published data shows the temperature at which it commenced was related directly to the minimum temperature of the previous winter. Annual relative fecundity has varied from 11 to 141 eggs/g of female with a tendency, although not statistically significant, for the higher values to have occurred following winter temperatures of less than about 12°C. Variations in egg size and fertilization rate have not correlated with larval viability which has been consistently high.

The paper presents the results of a prolonged research in a lead-polluted area. Extensive systematic studies of lead concentrations in topsoil, forage, blood, liver, and kidney in cows on farms within 1–10 km around the lead mine and smelter were carried out. After installation of a filter in 1978, lead concentrations began to decrease. However, when toxic levels of lead were within normal reference values, the authorities stopped to finance the project. In 2002, the research was concluded. A review of studies showed that the protective filter was effective; during the period 1975–2002 mean lead in forage dropped from 584.0 ± 324.0 to 5.5 ± 2.9 mg/kg, and the mean blood lead levels dropped from 1.251 ± 0.580 to 0.069 ± 0.041 mg/kg. Three years after the filter was installed the amount of lead in the liver and kidneys had normalized. Closely related to our research was also a case of cow lead poisoning.

This paper reports a series of trials on the cryopreservation of Oreochromis niloticus (L.) spermatozoa, using methanol as the cryoprotectant. Immotile milt samples pooled from four males were diluted with two diluents, each being subjected to equilibration periods of 15, 30, 45, 60 and 90 min. In addition, samples of fresh pooled milt were kept for 0, 2, 4, 6 and 8 days at 4°C prior to cryopreservation. Diluted samples were stored in 250-μl plastic straws and cooled to -50°C at 5°C/min and held under liquid nitrogen for between 1 and 3 weeks. Viability of post-thawed spermatozoa was estimated from video recordings of samples activated under a microscope and from fertilization rates of eggs. The type of diluent and its interaction with equilibration time significantly (P< 0.05) influenced the post-thaw motility of spermatozoa. Spermatozoa stored for up to 6 days prior to cryopreservation were as fertile as freshly frozen spermatozoa and yielded 60.6 (±SE, 8.4) developing embryos.

Tilapia, probably Africa's best candidate for aquaculture, is faced by the problems of small size due to overpopulation in culture systems. This paper reports the effect of high salinity on the reproduction of Oreochromis niloticus (L.) while testing the effect of a 20% protein supplemental feed on the growth and survival of this species in brackishwater ponds. The trial was run for 120 days in six 100-m2 ponds with fingerlings having an initial average weight of 2·80g. Salinity in the ponds rose from 25 ppt. to 50 ppt. during the culture period. Sampling for reproduction check was conducted every 2 weeks and 20% of the fish population were weighed to monitor growth changes and adjust quantity of feed fed. A 20% protein feed was fed at the rate of 5% and 3% of the total fish biomass during the first and second, and third and fourth months of the trial respectively. After 120 days the fish in each replicate were counted and weighed in bulk to obtain total weight while 50 females from each replicate were dissected and gonads examined. Results showed that growth was significantly different (P 0·05). 95% of the females were gravid but did not spawn. This suggests that gonadal development and onset of reproduction can be delayed by high salinities, which may be another practical method of population control in the culture of O. niloticus.