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An obstacle to the larval production of sunshine bass (female White BassMorone chrysops× male Striped BassM. saxatilis) is fungal growth on the eggs caused by the water mold,Saprolegniaspp. Copper sulfate (CuSO4) is commonly used for fungus control in troughs at catfish hatcheries, but the effectiveness in other fish-egg hatching systems is unknown. Because sunshine bass eggs begin hatching after 48 h, CuSO4treatments (0, 10, 20, and 40 mg/L) began the afternoon of spawning with a 10-min, aerated, static bath and were repeated the morning and afternoon of day 2; eggs were not treated after hatching began. An in vitro assay was developed for this treatment regimen that indicated maximum fungal inhibition was achieved with 20 mg/L CuSO4. In the effectiveness experiment in McDonald hatching jars (n= 3), fungus was severe in the untreated controls (27.7% survival), but very little fungus was present in treatments receiving 10 mg/L CuSO4(31.4% survival) or higher. The control was not significantly different from the 10-mg/L treatment. The highest survival was at 40 mg/L CuSO4(50.5% survival); however, the survival from the 20-mg/L CuSO4treatment (45.8%) was not significantly different from that in the 40-mg/L treatment and thus allows for a greater margin of safety. Fungus samples were identified asSaprolegnia feraxthrough genetic sequencing. Toxicity experiments on sunshine bass larvae indicated the 24- and 48-h LC50 values were 5.4 and 3.9 mg/L CuSO4, respectively; the no observed effect concentrations were 0.5 and 0.25 mg/L CuSO4, respectively. This study confirms that CuSO4can be an economical and valuable resource in hatchery management for the control of saprolegniasis on sunshine bass eggs in McDonald jars. Received September 25, 2015; accepted January 20, 2016 Published online June 15, 2016 [ABSTRACT FROM PUBLISHER]

Blue mussels ( Mytilus edulis ) are boreo-temperate, filter-feeding bivalves common to intertidal areas. As filter-feeders they have been employed in open-water, multi-tropic aquaculture systems to reduce organic benthic loading though the exploitation of suspended particulate organic materials. We compared δ 13 C and δ 15 N signatures and the isotopic niches of mussels growing in, and adjacent to, an integrated multi-trophic aquaculture (IMTA) farm in British Columbia, Canada, and using this information evaluated the contribution of aquaculture-derived effluent to their diet. Farm-sampled mussels had the least intraspecific isotopic variation compared to mussels sampled at the reference site. The interaction between time (i.e. sampling dates) and site did not significantly affect the isotopic composition of mussels; however significant variation was detected in δ 15 N values as a function of sampling date and particulate organic matter. A two-source isotopic mixing model indicated that marine particulate organic matter and IMTA farm effluent were approximately equal in importance (~ 46 % and ~ 54 %, respectively) to the diet of IMTA-retrieved mussels. Uptake of IMTA farm waste by M. edulis supports their use as economic extractives while also mitigating farmed sablefish ( Anoplopoma fimbria ) nutrient loading to the aquatic environment. [ABSTRACT FROM AUTHOR]

Pacific LampreysEntosphenus tridentatusare declining in the Columbia River basin as well as in much of their broader range. To mitigate for reductions in abundance, strategies such as hatchery propagation and captive rearing of lamprey larvae are currently being considered. We conducted a series of experiments using captive larval Pacific Lampreys at Eagle Creek National Fish Hatchery to investigate the effect of different food types and different food concentrations on the growth of larvae. In our first experiment, we evaluated the growth of larvae (TL range, 59–145 mm) given four different food types (algae, leaves, yeast–larval fish food, and salmon carcass analogs) and a control group that was not fed. Assimilation of food types was evaluated by tracking unique stable isotope signatures of δ13C and δ15N within larval tissues. Results from experiment 1 indicated that lampreys fed a diet of salmon carcass analog or algae had positive growth (up to 0.16 mm/d and 42% proportional change in length) over approximately 6 months. Isotopic analyses of larval tissues showed unique signatures that matched those of their specific food treatment. Based on the results of experiment 1, we conducted a second experiment to evaluate the growth of larvae fed four different quantities of salmon carcass analog. Results from this experiment indicated larval growth rate increased with increasing rations of food, but positive growth was observed in all feeding treatments. The highest dose of salmon carcass analog resulted in the highest growth (up to 0.15 mm/d and 36% proportional change in length) over 6 months. We successfully reared larval Pacific Lampreys in captivity with minimal mortality and positive growth, which highlights the potential to use captive rearing and propagation as a conservation tool for this ecologically and culturally important species. Received January 20, 2015; accepted April 17, 2015 [ABSTRACT FROM AUTHOR]

Highlights: [•] Important operational maintenance, cleaning and disinfection routines are described. [•] Activities are described for daily, weekly, per cycle and annual frequencies. [•] Control, vigilance, alarm system, and preventive maintenance programs are described. [•] Biosecurity measures are highlighted and discussed. [•] Importance and functions of operation and maintenance personnel are highlighted. [ABSTRACT FROM AUTHOR]

Abstract: A five-phase procedure for tropical marine fish hatchery site evaluation and selection is presented. On phase-1, the main definitions and criteria should be established, followed by a preliminary screening phase-2 to select several potential sites located at the interest region, based on historic records. In phase-3, additional historic information and general information gathered during preliminary visits will possibly allow the reduction of the potential site list, as well as to prepare a sampling program to complete and up-date characterization of the most relevant sites for the assessment of each site potentialities. On phase-4, the evaluation of the pre-selected and monitored sites will allow the selection of the best site available on the target region, based on a point and multiplying factor system adapted to the present purpose. Final phase-5 should be the pilot-scale operations to adapt and make the adjustments required to the specific selected site, before the commercial scale investments are completed. The applied system can be modified according to the planned technologies, as well as particular considerations to be applied. Results of application of this procedure on the Caribbean coast of Nicaragua are presented. Four areas were initially identified and only one was selected to continue the evaluation process, Big Corn Island. Of the five specific sites at Big Corn Island sites that were evaluated, Sandy Fly Point was selected by its highest total score. [Copyright &y& Elsevier]

Relationships between measures of oxidative stress and adaptive antioxidant defenses were studied in red sea bream (Pagrus major, RSB) caged at eight locations along the Fujian coast, China. Oxidative damage in tissues was investigated by measuring concentrations of protein carbonyl (CP) and reactive oxygen species (ROS), lipid peroxidation (LPO), acetyl cholinesterase activity (AChE), concentration of thiol groups and activities of enzymes associated with antioxidant defense. Magnitudes of antioxidant defense parameters were significantly, positively correlated with oxidative stress. Significantly greater ROS, LPO and CP content was observed in most tissues of RSB caged at three locations relative to those at the other locations. RSB caged at one location, Meizhou, exhibited significantly more DNA damage than did RSB caged at other locations. AChE activities in liver, kidney and muscle were statistically different among locations. Multivariate analyses were used to categorize the environmental quality of different locations. The battery of measures of oxidative stress proved to be a useful integrator of oxidative stresses that could be compared among locations. [Copyright &y& Elsevier]

The swimming path of a reared Pacific bluefin tuna, Thunnus orientalis, was measured in a submerged aquaculture net cage to understand how reared fish use the space in such a cage. A bluefin tuna (fork length, FL, 0.51 m) was captured by angling in the cage, and two micro data loggers (PD3GT, Little Leonardo; DST Comp-Tilt, Star-Oddi) were attached to its body. The fish was then released back into the net cage. The PD3GT measured its swimming speed and depth at 1-s intervals and recorded these in flash memory. The DST Comp-Tilt measured the magnetic field strength at 1-s intervals and recorded the heading estimated from the magnetic field strength in flash memory. The fish moved through the water in the cage at speeds of 0.7–0.8 m s-1 and attained a maximum speed of 3.6 m s-1. Burst swims exceeding 2 m s-1 were confirmed only after dark and a significant difference was found between the daytime and night-time swimming speeds (p < 0.001). The fish moved at depths between 2 and 22 m, swimming near the bottom during the day and at 10–15 m at night, with a significant difference in swimming depth between day and night (p < 0.001). The swimming path reconstructed by dead reckoning was visualised using night-time data. For this period, the absolute speed was corrected from 0.75 ± 0.09 m s-1 to 0.71 ± 0.15 m s-1 by removing the accumulated error from the reconstruction vector. This study allowed us to examine the behaviour of a tagged tuna in three dimensions and is the first to monitor the behaviour of a bluefin tuna in a submerged net cage. Although only one fish was analysed, this study provides useful information on the space use of reared fish in aquaculture net cages. Future studies must obtain sufficient data to understand the underlying generalities of tuna behaviour. [ABSTRACT FROM PUBLISHER]

This study describes growth variation within groups of salmonids and the relation to initial fish weights and feeding levels. PIT-tagged rainbow trout (RT) and brook trout (BT) of start weight 120–170 g were reared in separate tanks for 9 weeks. Both species were fed each day either a high ration close to satiation (H) or half of this ration (L). Four experimental groups (RT-H, RT-L, BT-H, BT-L) were studied with regard to their propensity to increase weight in accord with their initial weight. The slope of the regression line between initial weights (g) and weight increases for individuals in each tank in each period was applied as indicator for this propensity (termed “slope”). All calculated slopes in the experiment were positive which indicates the general ability of weighty fish to gain more weight than smaller individuals. The average slope during all 9 weeks was 2–4 times higher for RT-L (5.91) than for all other groups (RT-H: 1.50, P < 0.01; BT-H: 1.76, P < 0.01 and BT-L: 2.88, P < 0.05), indicating the particular propensity of large RT to gain weight when feed was restricted. Overall, ration level had large impact on slopes (H: 1.63, L: 4.39, P < 0.01), while this was not the case for species (RT: 3.71, BT: 2.32, P > 0.05). The magnitude of slopes decreased over time (weeks 0–3:4.27, weeks 3–6:3.02 and weeks 6–9:1.74, P < 0.05). The observed differences in weight gains between experimental groups were reflected in differences in coefficients of variations (CVs) for body growth. RT had larger body weight (BW) CVs compared to BT (0.257 vs. 0.206, P < 0.01) indicating more uneven feed share among RT than among BT in general. RT-L had significantly higher BW CVs than all other groups (0.300 vs. 0.184–0.229, P < 0.01). The observed differences in weight gains enhance size variations in terms of higher CVs, and this may have implications for feeding tactics in aquaculture where large size variations in groups may be disadvantageous to fish farmers. [ABSTRACT FROM AUTHOR]

Previous studies have reported elevated chemical contaminant concentrations in out-migrant juvenile salmon from the lower Columbia River. Hatchery rearing is a potential exposure pathway, as contaminants have been measured in hatchery fish and feed from other regions. In this study, we analyzed for polychlorinated biphenyls (PCBs), organochlorine pesticides including dichloro-diphenyl-trichloroethanes (DDTs), polycyclic aromatic hydrocarbons (PAHs), and polybrominated diphenyl ethers (PBDEs) in juvenile fall Chinook salmon Oncorhynchus tshawytscha and feed from eight hatcheries (Big Creek Hatchery, Oregon Department of Fish and Wildlife; Elochoman, Cowlitz, Washougal, Klickitat, and Priest Rapids hatcheries, Washington Department of Fish and Wildlife; Little White Salmon National Fish Hatchery; and Spring Creek National Fish Hatchery) that release fish into the lower Columbia River. In feed samples, the mean concentrations of summed PCBs, summed DDTs, and summed PAHs were 14, 27, and 370 ng/g wet weight, respectively. In Chinook salmon bodies, mean concentrations of summed PCBs, summed DDTs, and summed PAHs were 17, 9.0, and 30 ng/g wet weight, respectively; metabolites of PAHs were also detected in Chinook salmon bile. Other organochlorine pesticides were detected at low levels (<5 ng/g wet weight) in feed and Chinook salmon from all hatcheries. Concentrations of PBDEs in feed and fish from all hatcheries were low (<3 and < 1 ng/g wet weight, respectively). Contaminant exposure levels in hatchery Chinook salmon were generally below those associated with adverse effects on salmon health and also lower than those in field-collected juvenile fall Chinook salmon of hatchery origin from the lower Columbia River, suggesting that the river is a more important source of contamination than are the hatcheries. [ABSTRACT FROM AUTHOR]

Captive propagation of the federally endangered Rio Grande silvery minnow Hybognathus amarus has been identified as essential for the recovery of the species. A starter diet was initially developed for this cyprinid to support rapid growth through the larval stage. The diet, however, was too costly to support the grower phase of the species. A series of trials was conducted to determine whether a grower diet could be developed that would be cost effective while maintaining fish performance. Quadruplicate lots of Rio Grande silvery minnow (approximately 90 d posthatch, 0.39-0.42 g) were fed a reference diet or one of five experimental diets until just before gonadal maturation at two facilities in New Mexico (New Mexico State University [NMSU] and Dexter National Fish Hatchery and Technology Center [Dexter]). The diets varied in percent composition of ingredients to account for a range in feed costs. Cyclop-eeze (Argent, Redmond, Washington), krill, liver, and fish meals were present in the reference diet and sequentially altered in the remaining test diets to maintain high protein levels in the diets (57.9-64.9% dry matter). Total weight gains at the end of the 16-week trials were lower than expected (140-200%), with no differences among diets at NMSU. Although total weight gain was less at Dexter (105-150%), there were differences among diets. Specific growth rate was greater at both facilities in fish fed the reference diet and a diet lowest in fish meal (1.82% per day). The highest growth rate occurred across all diets within the first 30 d of both feed trials and then diminished by the end of the trials. There were no detectable differences in critical swimming speed or fat scores in fish fed diets with and without expensive feed ingredients or increasing fish meal. The most consistent growth was observed when fish were fed a diet low in fish meal, and our results clearly identified a less-expensive grower formulation for the production of this imperiled cyprinid. [ABSTRACT FROM AUTHOR]

The accumulation of nitrate in closed marine systems presents a problem for both the marine life and the environment. The present study, proposes the application of the ion exchange membrane bioreactor (IEMB) concept for removing nitrate from marine systems, such as aquaculture tanks or marine aquariums. The results obtained demonstrate that the IEMB was able to remove naturally accumulated nitrate from water taken from a public marine aquarium (Oceanário de Lisboa) and bioconvert it, in an isolated compartment (biocompartment), to molecular nitrogen, thus preventing secondary contamination of the treated water by microbial cells, metabolic by-products and excess of carbon source (ethanol). This system allowed for the removal of nitrate at concentrations of 251 and 380mg/l down to below 27mg/l exchanging it for chloride. Under the studied operating conditions, the IEMB proves to be a selective nitrate removing technology preserving the initial water composition with respect to cations, due to the Donnan exclusion effect from the membrane, and minimizing the counter diffusion of anions other than nitrate and chloride, due to the use of water with the same ionic composition in the biocompartment. This is an advantage of the IEMB concept, since the quality of the water produced would allow for the reutilisation of the treated water in the aquarium, thereby reducing both the wastewater volume and the use of fresh water. [Copyright &y& Elsevier]

Abstract: The objective of this paper is to investigate potential design procedures for rigid, closed containment aquaculture systems deployed in the marine environment. In this context, closed containment is a term used to describe a range of aquaculture technologies that attempt to restrict and control interactions between farmed fish and the external aquatic environment, with the goal of minimizing impacts. The containment units are often closely spaced and moored to the seafloor bottom. The geographical area of interest is the Straits of Georgia, British Columbia in Canada. In this study, the design configurations of multiple closed containment systems are investigated. The design procedures include examining: (1) local environmental conditions, (2) drag forces on multiple containment units, (3) wave loading, (4) undamped heave motions, (5) mooring gear components and (6) material stresses on a rigid containment structure. Operational and other design considerations are also discussed. Preliminary findings indicate that wave forces could be substantial. In addition, little is known about how containment units, which are closely spaced, will respond individually or as a farm when subjected to surface waves. [Copyright &y& Elsevier]

The article presents a study concerning the distribution of rotifers in the aquaculture station of El Hamma in Gabes, Tunisia from February 2005 to January 2006. The authors mention that the station is comprised of eight interrelated basins with geothermal waters which are used for the fish tilapia production. They also state that the study found 13 rotifers with the Brachionus urceolaris as the most prominent. Furthermore, they stress that the result of the study implicates that the basins were overall oligo-eutrophic.

Brooders of Surubí ( Pseudoplatystoma fasciatum) were caught in the Ichillo River (Bolivian Amazon) and adapted to captivity conditions for 1 year in the facilities of the experimental aquaculture station of ‘El Prado’ (Santa Cruz de la Sierra) under natural temperature and photoperiod conditions. Induced reproduction was obtained by means of Ovaprim® (Syndel, Canada) injections and artificial fertilization. Sperm and ova were obtained by gentle stripping of male and female brooders. Fertilized eggs were incubated in 60 L Zug jars. A mean hatching rate of 73.7±19.0% was obtained after 24 h at 26.5 °C. For larval rearing, several protocols were tested with different settings of photoperiod, light intensity, food type and period of distribution, and stocking density. The best survival rates were obtained with Artemia nauplii feeding in total darkness. A high level of aggressiveness between larvae and precocious appearance of jumpers was observed, but these can be controlled with appropriate rearing conditions. [ABSTRACT FROM AUTHOR]

To conserve and utilize the genetic pool of gynogenetic gibel carp ( Carassius auratus gibelio), the Fangzheng and Qihe stock hatcheries have been established in China. However, little information is available on the amount of genetic variation within and between these populations. In this study, clonal diversity in 101 fish from these two stock hatcheries and 35 fish from two other hatcheries in Wuhan and Pengze respectively was analysed for variation in serum transferrin. Thirteen clones were found in Fangzheng and Qihe, of which 12 were novel. Six clones were specific to Fangzheng and three specific to Qihe, whereas four were shared among the Fangzheng and Qihe fish. To obtain more knowledge on genetic diversity and genealogical relationships within gibel carp, the complete mitochondrial DNA (mtDNA) control region (∼920 bp) was sequenced in 64 individuals representing all 14 clones identified in the four hatcheries. Differences in the mtDNA sequences varied remarkably among hatcheries, with the Fangzheng and Qihe lines demonstrating high diversity and Wuhan and Pengze showing no variation. The Fangzheng and Qihe lines might represent two distinct matrilineal sources. One of the Qihe samples carried the haplotype shared by a most widely cultivated Fangzheng clone, indicating that a Fangzheng clone escaped from cultivated ponds and moved into the Qihe hatchery. Four Fangzheng samples clustered within the lineage formed mainly by Qihe samples, most likely reflecting historical gene flow from Qihe to Fangzheng. It is suggested that clones in Wuhan originated from Fangzheng, consistent with their introduction history, supporting the hypothesis that gibel carp in Pengze were domesticated from individuals in the Fangzheng hatchery. [ABSTRACT FROM AUTHOR]

The impact of shrimp larvae development, as well as water and food inputs upon the increase of bacterial populations within the bacterial community of hatchery tank biofilms, was studied. For this study, a total of 68 biofilm samples were collected from concrete tanks at three larvae production times in a commercial shrimp hatchery. Seventeen samples were taken at each larval development stage (Zoea I, Mysis I, postlarvae 1 and postlarvae 16), as well as 37 samples from water, shrimp nauplii and food, introduced into the shrimp hatchery tanks. Culturable and direct bacterial counts were performed and 16S-rRNA-targeted oligonucleotide probes were used to quantify the presence of specific bacterial groups. An average of 27–70% of DAPI total cell counts were detected with the EUB338 probe, while the GAM42a probe signal ranged from 1% to 11%. Vibrio-like bacteria (VLB) counts in TCBS agar ranged from <10 to 101 VLB/cm−2, with a tendency to increase at the last postlarvae stage. The most significant external source of bacteria registered with GAM42a probe and TCBS agar were found in live Artemia nauplii, used as food; nevertheless, biofilms remain with low counts of these groups. [ABSTRACT FROM AUTHOR]

The article presents an extensive research work studying the relationship of soluble phosphorus in the tank water of rainbow trout with feeds and oxygen. According to the article, the measurement of phosphorus concentration is a monitoring factor in both fresh water samples and land-based fish farms. The article analyzes the diel excretion pattern for rainbow trout, Oncorhynchus mykiss. The research concentrates toward quantifying the diel fluctuations of soluble phosphorus concentrations in the tank water of rainbow trouts. The research shows that it is more difficult to measure phosphorus than dissolved oxygen.

We examined the biomass-dependent effects of common carp ( Cyprinus carpio) on water quality in 10 ponds at the Eagle Mountain Fish Hatchery, Fort Worth, Texas, USA. Ponds contained 0–465 kg ha−1 of common carp. We measured limnological variables at weekly intervals for four weeks in early summer, after which ponds were drained and the biomass of fish and macrophytes was determined. Common carp biomass was significantly positively correlated with chlorophyll a, total phosphorus, total nitrogen, and Keratella spp. density and negatively correlated to bushy pondweed ( Najas guadalupensis) biomass. In addition, we combined our data with data from comparable studies to develop more robust regression models that predict the biomass-dependent effects of common carp on water quality variables across a wide range of systems. [ABSTRACT FROM AUTHOR]

Experiments were conducted to determine the effects of different water hardness concentrations on colonization of Saprolegnia diclina in an attempt to explain some of the differences in fungal growth and antifungal chemical effectiveness observed at various fish hatcheries. Fungal growth on nonviable seeds of hemp Cannabis sativa was observed significantly sooner in water where hardness was elevated due to the addition of calcium sulfate dihydrate in each of the experiments. Seeds in test tubes containing water with a hardness of 300 mg/L exhibited fungal colonization in approximately one-half the amount of time observed with seeds in water with hardness less than 150 mg/L. In petri dishes containing inoculated corn meal plugs, the growth of S. diclina was observed at only 24 h on seeds in water with a hardness of 450 mg/L, which was significantly quicker than the 31 h from seeds in water hardness of 150 and 300 mg/L. This, in turn, was significantly quicker than the 35 h required for growth in the 0 mg/L hardness control water. Results were similar in a subsequent experiment where the inoculated plugs were removed from the petri dishes prior to seed placement. The relatively minor changes in pH following the addition of water hardness-altering chemicals did not affect the timing of fungal colonization, as a separate experiment indicated no differences in fungal growth in pH ranging from 3 to 10. [ABSTRACT FROM AUTHOR]

This paper presents a study of operating costs in shrimp hatcheries. Size effects are presented for fixed, variable, unitary, and marginal costs. Cost structures by functional production department and by cost-category are discussed for a hypothetical postlarvae/month hatchery in an industrialized country, and compared to those of a hatchery in a developing country. Health management issues, mainly measures commonly used to manage bacterial diseases, and their economic impact are discussed, focusing on the trade off between survival rates and sanitation down-time. Salaries and benefits represent the largest cost-component (37%) for hatcheries in industrialized countries, while feeds and operating supplies constitute the most important costs in developing countries (60%). The need to import hatchery feeds arid other operating supplies into developing countries works against savings from lower labor costs typical of developing countries. Total fixed costs depend on the size of a hatchery and are constant for all possible levels of output. Average fixed cost per unit (thousand postlarvae) can be reduced by producing high postlarval outputs. Hatcheries in areas with seasonal shrimp crops face the challenge of covering fixed costs with revenue from a short production season. Hatcheries with large fixed costs can operate in a cost-efficient manner only by producing high levels of output. Average total cost and average variable cost curves follow a U-shaped curve, in which costs first decline as output increases, then reach a minimum, and finally increase as output increases above a point of diminishing returns. In hatcheries total costs are independent of larval survival, but lower output resulting from low survival increases unit costs. This effect is more pronounced at lower levels of output. Bacterial diseases decrease survival rates and increase unit costs. [ABSTRACT FROM AUTHOR]

Two commercial products (LASE and PhytoMax), which are formulations of organic acids, enzymes, vitamins, and micronutrients intended to stimulate microbial activity in fish production ponds, were evaluated. The effects on water quality of twice-monthly applications of PhytoMax and LASE in a replicated field test conducted in commercial channel catfish, Ictalurus punctatus, ponds in northwest Mississippi were studied. Temperature, pH, ammonia, nitrite, nitrate, reactive phosphorus, total phosphorus, chemical oxygen demand, chlorophyll a, and dissolved oxygen were monitored for 7 months and compared among LASE-treated, PhytoMax-treated, and control ponds. Only pH was statistically different (P < 0.05) among ponds groups-7.6 in controls vs. 7.7 in LASE and PhytoMax ponds-however, this difference was not biologically significant. The results of this study failed to demonstrate a benefit of adding PhytoMax or LASE to commercial channel catfish ponds. Although adding specific micro-nutrients, vitamins, and enzymes to enhance natural microbial activity is a more ecologically sound strategy than adding bacterial suspensions, PhytoMax and LASE did not improve water quality in ponds at the recommended application rates. [ABSTRACT FROM PUBLISHER]

In temperate regions, post-larvae freshwater prawn, Macrobrachium rosenbergii, are grown to more advanced sizes in tanks prior to pond stocking. This intermediate stage of culture is referred to as the nursery period. Little research has been conducted on different management practices on juvenile prawn growth and survival during this 30-60 day period. Survival during the nursery stage has been highly variable and may be related to the cannibalistic behavior of juvenile freshwater prawn when cultured at high densities in the nursery. The objective of this study was to evaluate the effect of stocking density, relative to the provision of artificial substrate (number of prawns/m2 of substrate), on growth, survival, and economic variables for freshwater prawn juveniles during nursery production. Post-larvae (0.01±0.00 g, n = 300) were stocked into nine 1900 L tanks, each provided with 20.5 m2 of artificial substrate in the form of horizontal layers of black plastic mesh (10 mm) spaced 5 cm apart. Tanks were randomly assigned one of three prawn densities (215, 430, or 860 post-larvae/m2 of substrate), which equated to 2.3, 4.6 and 9.2 prawn/L, respectively. Juvenile prawn were fed a commercial trout diet (42% protein) at a percentage of body weight according to a feed rate table. Water quality was maintained using a flow rate of 8 L/min in each tank from a reservoir pond. Temperature was maintained at approximately 28°C using heat pumps. After 56 days there was no significant difference (P > 0.05) in average weight of juvenile prawn stocked at the three densities (0 = 0.58±0.12 g, n = 9). Survival was significantly lower (P < 0.05) for prawn stocked at 860 m2 (62%) than in those stocked at 430/m2 (78%) and 215/m2 (94%), which were not statistically different (P > 0.05). Even with reduced survival, the highest stocking density produced the greatest number of nursed juveniles based on both tank volume (5.5/l) and surface area (530/m2), at the lowest average cost. [ABSTRACT FROM PUBLISHER]

Culture potential of the native pink shrimp, Farfantepenaeus paulensis, and exotic Pacific white shrimp, Litopenaeus vannamei, was analyzed in extreme southern Brazil. The experiment was conducted at the Marine Aquaculture Station, University of Rio Grande, Rio Grande do Sul State. After nursery, pink shrimp (0.16 g) and Pacific white shrimp (0.17 g) juveniles were transferred to a 450 m2 earthen pond internally divided into six circular (21 m2 each) experimental pens. Pens were randomly assigned to a treatment (pink shrimp or Pacific white shrimp) and stocked at 15 shrimp/m2. Shrimp growth was monitored during 102 days in the summer. Feed was composed of a commercial diet and a fresh frozen mixture (fish and crustacean). After 30 days of culture, Pacific white shrimp showed significantly higher increases in mean weight, reaching at-harvest weight of 12.52 g compared to 11.17 g for pink shrimp. Water quality parameters presented optimal growing conditions for both species, except for lower temperatures (19°C) during the last two weeks of culture, which resulted in a drastic decrease in the growth rate of Pacific white shrimp. These results indicated a better tolerance for lower water temperatures on the part of shrimp. Although the lower temperatures resulted in a reduced number of cycles (1 or 2 per year), the estimated yield for pink shrimp (1,451 kg/ha) and Pacific white shrimp (1,790 kg/ha) suggested that the production per cycle in extreme southern Brazil is comparable to that in the other Brazilian States. Despite the more favorable results for Pacific white shrimp, the culture of pink shrimp is also recommended, but further studies are necessary to improve its growth performance under culture. [ABSTRACT FROM PUBLISHER]

Presents information on a study which explored a historical review of homarid lobster fisheries and the development and usage of lobster hatcheries. Environmental factors and landing fluctuations; Development of artificial propagation; Laboratory and field research from hatchery experimentation.

Examines a combined indoor fingerling and outdoor grow-out red drum aquaculture facility using stochastic sensitivity analysis. Chance of survival of the fingerlings; Impact of management capabilities on the economic success of facility; Determination of the rate of return for the investor.

Circular tanks are appropriate for Clarias gariepinus (Burchell) culture. Wide/shallow tanks (with a diameter to depth ration of about 10) are preferable lo narrow/deeper tanks. The optimal flow rate for larvae will be one which provides sufficient oxygen yet does not generate a current velocity fast enough to cause them to swim against it. However, current velocity, for a given type and orientation of inflow, will depend particularly upon tank diameter to depth ratio and flow rate and will be related to position within the tank. Therefore for a given circular tank design a theoretical maximum flow rate and concomitant biomass can be estimated for a given mean fish size. Once airbreathing begins the optimal flow rate for fry is simply that which does not elicit swimming. [ABSTRACT FROM AUTHOR]