Search

Three consecutive 3-week trials were conducted to assess the growth, productivity, and nutrient removal rates of sea lettuce (Ulva lactuca) cultured in effluents from white seabass (Atractoscion nobilis) raceways. All U. lactuca cultivation trials were conducted in 175 L tanks with a surface area of 0.89 m2 run in triplicate, with water quality and growth measurements taken weekly. For the shading trial, U. lactuca was stocked at 0.56 kg/m2 with either 0%, 30%, or 60% shade and seawater supplied at 63 tank volumes per day (vol./day) water exchange (7.6 L/min) for each tank. The removal rate of total ammonia nitrogen (TAN) decreased with increasing shade levels, and the peak exceeded 80% removal at 0% shading. Growth rate and productivity of U. lactuca under 0% shading was 12.09 ± 3.13%/d and 13.28 ± 4.66 g DW/m2/d, which were both significantly higher than other shading levels. For the stocking density and water exchange rate trial, the stocking density of U. lactuca was 0.56 or 1.12 kg/m2, and seawater exchange rates were 4, 12, or 63 vol./day in a 2-factor design. In this trial, TAN removal rates were 100% across all treatment combinations. Growth rate of U. lactuca was highest (20.36 ± 2.36%/d) at 0.56 kg/m2 under the exchange rate of 63 vol./day, and the productivity reached up to 30.89 ± 6.53 g DW/m2/d, which was not different than that of U. lactuca stocked with 1.12 kg/m2 at the same exchange rate (p = 0.47). In a trial comparing sand-filtered seawater (RAW seawater) with seawater effluent from a raceway containing A. nobilis (FISH seawater), TAN removal rate by U. lactuca was consistently nearly 100% when supplied with FISH seawater with a TAN concentration ranging from 0.11 to 0.18 mg/L. Growth rate and productivity of U. lactuca supplied with FISH seawater were 21.36 ± 2.25%/d and 33.83 ± 7.29 g DW/m2/d, respectively, which was not different than that for U. lactuca supplied with RAW seawater. However, the protein content of U. lactuca cultured with FISH seawater was significantly higher and C/N ratio significantly lower than those cultured with RAW seawater (p < 0.01), which indicated that U. lactuca was in a nitrogen-limited situation when cultured with RAW seawater. In light of the better understanding of U. lactuca performance achieved in our study, the optimum U. lactuca and A. nobilis density combinations will be confirmed in future studies based on nitrogen balance to maximize the nutrient removal rates and diversity of seafood production. • An IMTA was established for integrating Atractoscion nobilis and Ulva lactuca. • Optimum shading level, stocking density and seawater exchange rate were determined. • Nutritional quality of U. lactuca was improved by total ammonia nitrogen from A. nobilis raceway. [ABSTRACT FROM AUTHOR]

Aspects of swimming and metabolic physiology were measured in aquaculture-reared California Yellowtail ( Seriola dorsalis ) in comparison to wild-caught individuals in order to examine potential differences in health and fitness associated with captive rearing, and to help identify areas for targeted improvement in Seriola aquaculture. Incremental swimming velocity trials using a swim tunnel respirometer on small yellowtail (mean body length = 18.9 cm, mass = 80.1 g) showed that aquaculture-reared fish had a significantly slower mean maximum sustainable swimming speed ( U crit ) (4.16 ± 0.62 BL s −1 ) in comparison to that of wild-caught fish (4.80 ± 0.52 BL s −1 ). In addition, oxygen consumption ( Ṁ O 2 ) measurements at varying swimming speeds allowed for estimation of standard metabolic rate, which was significantly higher in aquaculture-reared yellowtail (7.31 ± 2.32 vs. 3.94 ± 1.60 mg O 2 kg −1 min −1 at 18 °C). Aquaculture fish also had a lower aerobic scope (9.20 ± 3.44 mg O 2 kg −1 min −1 ) in comparison to wild-caught yellowtail (15.80 ± 5.78 mg O 2 kg −1 min −1 ), which likely contributed to their reduced capacity for fast sustainable swimming. Reduced physical fitness is commonplace in aquaculture-reared fishes, and the examination of wild-caught yellowtail in this study provides baseline metrics that can be used to gauge the health and fitness of future S . dorsalis production. In particular, the lower standard metabolic rate and higher aerobic scope of wild-caught fish represent desirable metabolic characteristics that if achievable in aquaculture through better-rearing practices could allow for increased feed conversion efficiencies and potentially faster growth. At a minimum, a 35–40% reduction in metabolic costs at low swimming speeds (to those observed for wild-caught yellowtail) should result in substantial cost savings for feed in aquaculture operations. [ABSTRACT FROM AUTHOR]

A captive population of California yellowtail ( Seriola lalandi) was used to document spawning patterns, including measures of egg production, population fecundity and egg and larval quality from 2007 to 2010. Spawned eggs were also used to document larval development and to develop rearing techniques for aquaculture in the region. Broodstock growth and condition factor were best when feeding rations were maintained at 10-15% body weight week−1 during the warm summer months. A winter ration based on satiation feeding was typically 4% body weight week−1. During the 4-year study period, the only broodstock health issue was an infestation by the parasitic gill fluke Zeuxapta seriolae, which was readily treated. Spawning occurred naturally in the 140 m3 tank when the ambient water temperature reached 16°C and ended when the temperature exceeded 22°C. Egg production reached a maximum in 2010 when 43 spawn events were recorded from a pool of nine females yielding 36.8 million eggs in total. The average female size at this time was 20 kg, which equated to a total annual population fecundity of approximately 226 000 eggs kg−1 female year−1. Larval rearing trials yielded survival rates as high as 5.8% from egg to 50 days post-hatch (dph). Successful larval culture methods included the addition of algae paste for green water culture, rotifers (20 rotifers mL−1) at 2 dph and Artemia (5 Artemia mL−1) at 6 dph. Larvae were transferred from the incubation tank at 10 dph to a shallower tank with 33% greater surface area to accommodate the larvae's strong orientation to surface waters. This research represents the first documentation of successful spawning and larval rearing for S. lalandi in the eastern Pacific. [ABSTRACT FROM AUTHOR]

Abstract: Light can have significant impacts on larval growth and survival of many marine fish species. Here, we study the effect of photoperiod on larvae from captive populations of two marine finfish species, California yellowtail (CYT; Seriola lalandi) and white seabass (WSB; Atractoscion nobilis). Two photoperiod treatments were tested: 12h light and 12h dark (12-L), and 24h light and 0h dark (24-L). CYT larvae were significantly heavier (240±16μg dry weight) in the 24-L treatment group than the 12-L group (155±25μg dry weight) at 10dph. Similarly, WSB were significantly heavier (685±77μg dry weight) in the 24-L treatment group than the 12-L group (455±44μg dry weight) at 18dph. CYT larvae also had significantly greater survival (16.6±6.2%) in the 24-L treatment over the 12-L conditions (7.6±4.9%). In contrast, WSB larvae showed no significant difference in survival between treatments. Food consumption was significantly greater in the 24-L treatment for both species up until 6dph, after which time no difference was observed. Swim bladder inflation rates were not significantly affected by the photoperiod treatments. These results indicate that photoperiod is a significant factor in early larval performance for both CYT and WSB, although it is unknown if continuous light becomes detrimental as larvae develop. [Copyright &y& Elsevier]

Abstract: Environmental parameters, such as light intensity and turbidity, have been shown to significantly influence the growth and survival of cultured larval finfish. Here, we study three light intensities (low: 360lx; medium: 1675lx; and high: 14,850lx) and two turbidity conditions (with and without green water) to determine optimum growth and survival for California yellowtail (Seriola lalandi) larvae. The study lasted from 2 thru 16days post hatch (dph). The high light intensity, green water treatment produced the largest larvae (865±165μg dry weight; 7.01±0.07mm notochord length), had the highest survival rate (9.2±3.1%), and had the highest incidence of swimbladder inflation (68.8±3.1%) among all treatments in this study. The low and medium light intensity, clear water treatments produced the smallest larvae (183±60μg dry weight; 5.58±0.07mm notochord length) and the lowest survival rate (0–0.10%). These results indicate that light intensity and turbidity are significant factors that affect growth and survival of Seriola lalandi larvae up to 16dph. [Copyright &y& Elsevier]

California yellowtail (CYT), Seriola dorsalis, is a promising candidate for aquaculture due to its rapid growth and high-quality flesh, particularly in markets like Japan, Australia, China, and the United States. Soy protein has shown success as a replacement for marine protein sources in CYT diets, reducing fishmeal levels, though concerns about potential intestinal inflammation persist with the inclusion of solvent-extracted soybean meal. To address this, processing strategies like fractionation, enzymatic treatment, heat treatment, and microbial fermentation have been employed to mitigate the negative impacts of soybean meal on fish nutrition and immune systems. This study focuses on optimizing soybean meal inclusion levels by incorporating advanced soy variants into CYT diets. The eight-week feeding trial, conducted in a recirculation system, featured six diets with sequential inclusion levels (0, 50, 100%) of high protein low oligosaccharide soybean meal (Bright Day, Benson Hill, St Louis, MO) and enzyme-treated soybean meal (HP 300, Hamlet Protein Inc., Findlay, OH), replacing solvent-extracted soybean. The study compares these formulations against a soy-free animal protein-based diet. At the end of the trial, fish were sampled for growth performance, body proximate composition, intestinal morphology, and immune response from gut samples. Results showed consistent FCR (P = 0.775), weight gain (P = 0.242), and high survival rate (99.4 ± 0.5%) among dietary treatments (P>0.05). Histological evaluations revealed no gut inflammation and gene expression analysis demonstrated no significant variations in immune, physiological, and digestive markers apn (P = 0.687), mga (P = 0.397), gpx1 (P = 0.279), atpase (P = 0.590), il1β (P = 0.659). The study concludes that incorporating advanced soybean meal products, replacing up to 20% of fishmeal does not negatively affect CYT's growth and intestinal health. This suggests that all three soy sources, contributing 35% of total protein (15.4 g 100 g-1 diet), can be included in practical diets without compromising CYT's intestinal integrity or growth. These findings have positive implications for the commercial production of CYT and future research on the incorporation of plant-based proteins in aquaculture diets. [ABSTRACT FROM AUTHOR]

California halibut (Paralichthys californicus) is a candidate species for aquaculture and stock enhancement. These applications rely on sex control, either to maximize the production of faster growing females or to match sex ratios in the wild. Other paralichthids exhibit temperature‐dependent sex determination (TSD), but the presence and pattern of TSD is not well defined in California halibut. Juvenile California halibut were cultured at three distinct temperatures (15°C, 19°C, and 23°C) through the developmental period presumed to be thermosensitive based on findings from congeners. Sex ratios were quantified in each treatment using phenotypic sex identification techniques applied early (molecular biomarkers; 51–100 mm total length [TL]) and late (visual examination of the gonads; ≥100 mm TL) in the juvenile phase. Both techniques indicated similar sex determination trends at each temperature, with overall sex ratios assessed as 49.9% male at 15°C, 74.5% male at 19°C, and 98.2% male at 23°C. Growth rates were highest at 23°C and lowest at 15°C, with intrinsically fast‐ and slow‐growing individuals at all temperatures. At 15°C and 19°C, females comprised a higher proportion among the fast growers than they did among the slow growers. These data show that California halibut exhibit TSD, with temperatures of 19°C and 23°C masculinizing fish while 15°C appears to produce a 1:1 sex ratio. This study will help optimize sex ratios and growth in hatcheries through thermal manipulation. Furthermore, the developed biomolecular tools and identified temperature thresholds will be important in future work to understand the influence of global warming on wild population demographics. [ABSTRACT FROM AUTHOR]

Diet-to-tissue transfer of long-chain polyunsaturated fatty acids (LC-PUFAs) is more efficient when diets contain saturated fatty acid (SFA) or monounsaturated fatty acid (MUFA)-rich alternative lipids. This mechanism, the omega-3 or LC-PUFA “sparing effect”, encourages more efficient metabolism of the limited LC-PUFAs available in terms of their important physiological functions and tissue retention, and the likelihood of successful fish oil sparing (i.e. complete fish oil replacement maintaining growth and tissue fatty acid profile). However, it is still unclear whether dietary SFAs and MUFAs are equivalent or interact synergistically or antagonistically in this context. Accordingly, we compared production performance and tissue fatty acid composition of California Yellowtail fed diets containing fish oil (rich in LC-PUFAs) or soybean oil (rich in C 18 PUFAs), partially hydrogenated soybean oil (rich in MUFAs), fully hydrogenated soybean oil (rich in SFAs), or blends of these soybean oils. After 10 weeks, production performance was not affected by dietary lipid source or fatty acid composition, and tissue fatty acid profiles generally mimicked dietary fatty acid composition. However, tissues of fish fed SFA-rich lipids exhibited the greatest similarity to those fed fish oil, and fillets of fish fed fully hydrogenated soybean oil had significantly higher levels of LC-PUFAs (43.9 g LC-PUFA /100 g fatty acid methyl esters; FAMEs) than those fed any of the other diets (22.5–36.9 g LC-PUFA /100 g FAMEs), including the LC-PUFA-rich fish oil-based feed (39.8 g LC-PUFA /100 g FAMEs). Power regression analyses demonstrated a stronger positive relationship between dietary SFAs with fillet LC-PUFA deposition ( r 2  = 0.73) than dietary MUFAs ( r 2  = 0.09), whereas dietary C 18 PUFAs were observed to have a negative relationship with fillet LC-PUFA content ( r 2  = 0.85). These trends were also observed in liver and eye tissues, and to a lesser extent in brain tissue. Multiple linear regression analyses demonstrated a stronger relationship between dietary levels of PUFAs and SFAs and tissue fatty acid profile composition, including LC-PUFA content, than dietary levels of PUFAs and MUFAs. Fillet lipid content varied significantly, with the FISH and C 18 PUFA SOY diets displaying the highest levels. The same pattern was observed for liver lipid content, but not significantly. Our findings suggest that SFAs are the primary drivers of LC-PUFA sparing, whereas MUFAs exert a weaker independent sparing effect and appear to diminish the sparing effect of dietary SFAs when MUFAs were also present. [ABSTRACT FROM AUTHOR]

Malpigmentation is a common phenomenon in flatfish culture. We describe a stepwise series of three experiments aimed at reducing pseudoalbinism and ambicoloration in cultured California halibut (Paralichthys californicus). Pigmentation was assessed between 49 and 56 days post hatch when reared at 18–19 °C. Manipulation of rotifer enrichments was tested initially to reduce malpigmentation, with up to 10.8 ± 3.8% of fish being normally pigmented. Dietary timing was subsequently examined, with late introduction of Artemia yielding the highest rate of normal pigmentation (40.6 ± 8.6%) and eliminating ambicoloration. Rearing temperature was further shown to influence malpigmentation, with the most normally-pigmented fish occurring at 15 °C (46.3 ± 2.7%) and the fewest at 23 °C (5.7 ± 1.0%). Continued efforts to eliminate malpigmentation, in particular pseudoalbinism, during intensive larviculture of California halibut will focus on additional modifications of key nutritional and environmental parameters. • Abnormal pigmentation can occur in cultured flatfish. • Larval experiments were undertaken to reduce malpigmentation in California halibut. • Malpigmentation rate was reduced through stepwise modifications to rearing diet and temperature. [ABSTRACT FROM AUTHOR]

The larval rearing performance of California yellowtail ( Seriola lalandi) and white seabass ( Atractoscion nobilis) was compared between larvae fed taurine-supplemented rotifers ( Brachionus plicatilis) and Artemia ( Artemia franciscana) and control groups fed live feeds with no taurine enhancement. Results from the S. lalandi trial demonstrated that when fed taurine-supplemented rotifers, survival was significantly higher than the control group (20.1% vs. 9.1%, P < 0.01) as was notochord length (5.43 mm vs. 5.13 mm, P < 0.005). No larval performance differences were detected between experimental and control treatments of A. nobilis. Biochemical analyses demonstrated that taurine concentrations were significantly elevated in both S. lalandi (23.7 vs. 2.7 mg g−1, P < 0.001) and A. nobilis (33.0 vs. 21.0 mg g−1, P < 0.005) when live feeds were supplemented with taurine. Results suggest that taurine is a limiting nutrient in the larviculture of S. lalandi but may not be for A. nobilis. [ABSTRACT FROM AUTHOR]

This study focused on methods to reduce bacterial loads in the larval culture tanks of California yellowtail ( Seriola lalandi). We conducted two trials to evaluate methods to minimize bacterial loads in the larval rearing water. The first trial examined the use of bentonite clay as a turbidity agent to replace algae in a green water-type environment. This trial consisted of three treatments: (1) clay with continuous feeding ( CCO), (2) clay with batch feedings ( CBA) and (3) algae paste with batch feedings ( ALG). The results showed that both clay treatments had significantly fewer Vibrio colonies in the water column ( CBA - 180 ± 78; CCO - 377 ± 120 CFU mL−1) than the ALG treatment (5692 ± 2396 CFU mL−1) after 14 days of culture. Survival was significantly higher in the CCO treatment (14.1 ± 2.6%) than either the CBA (2.3 ± 0.5%) or ALG treatments (2.8 ± 1.5%). The second trial attempted to limit bacterial loading in the larval culture tank by passively transferring the larvae into an adjacent, clean tank at 1, 5 and 9 days post hatch during the first 2 weeks of culture. The results from this trial showed that after 12 days of culture, water in the transfertank had fewer Vibrio colonies (1025 ± 541 CFU mL−1) than the water in the control tanks (1962 ± 1415 CFU mL−1). Also, survival was significantly higher among larvae that were transferred (43.9 ± 13.5%) than in the control tanks (23.1 ± 6.3%). [ABSTRACT FROM AUTHOR]

A modular land-based integrated multi-tropic recirculating aquaculture system (IMTRAS) for fish, sea cucumbers, mussels and macroalgae was established to optimize resource utilization, while reducing water requirements and nutrient discharge levels. The first module included California yellowtail (Seriola dorsalis) as the primary "fed" species and Ulva lactuca functioned as biofilters. Effluent from the fish tank was passed through a drum filter for solids removal, and then the filtered seawater entered a sump. Seawater was pumped from the sump into U. lactuca tumble culture tanks and then back to the fish tank. The second module housed Mediterranean mussels (Mytilus galloprovincialis) and warty sea cucumbers (Apostichopus parvimensis) in separate serial units. Backwashes of the drum filter occurred automatically and effluent flowed by gravity to M. galloprovincialis culture tanks, and then to A. parvimensis culture troughs. Two trials of two weeks each were conducted – one at an initial fish stocking density of 5.2 kg m−3 (Trial 1), and another at 20.9 kg m−3 (Trial 2). The seawater flow rates and aeration levels were determined based on earlier pilot studies. Yellowtail grew on average 0.36 and 0.64% d−1 with a food conversion ratio of 1.73 and 1.47, in Trial 1 and Trial 2, respectively. Ulva lactuca showed productivity of 24.39 ± 2.00 and 15.57 ± 2.47 g DW m−2 d−1 with a protein content of 15.13 ± 3.11 and 30.36 ± 1.41% DW in each trial, respectively, which resulted in nitrogen uptake rates of 0.58 ± 0.08 and 0.75 ± 0.12 g m−2 d−1. Mussels and sea cucumbers removed 16.1 to 18.9% and 16.4 to 20.4% of the total solid wastes produced daily, respectively. The condition index of mussels and sea cucumbers showed no difference between the beginning and end of trial. After calculating the nitrogen balance in this IMTRAS, the largest proportion of nitrogen was in the form of dissolved inorganic nitrogen that accumulated inside the system (31.46%), followed by the yield of S. dorsalis (24.64%) and then the harvest production of U. lactuca (14.91%). All other measured nitrogen components were <7 % combined. Nitrogen that was not directly measured (i.e. "black box" nitrogen) including nitrogen accumulated inside plumbing components and lost with the effluent discharge totaled 22.48%. Based on these results, the proper ratio of co-cultured species in this system was estimated as 20.9 kg m−3 of S. dorsalis , six tanks of U. lactuca , three tanks of M. galloprovincialis and six troughs of A. parvimensis with the same volumes and stocking densities reported in this study. Future long-term trials need to be conducted to refine the operation of this IMTRAS. • An IMTRAS was established for the culture of fish, sea cucumbers, mussels and macroalgae. • All trophic levels showed good performance with little daily seawater addition. • Considerable waste removal occurred by macroalgae and solids feeders. • More macroalgae and solids feeders were needed at high fish stocking density. [ABSTRACT FROM AUTHOR]

Abstract: Reproductive exhaustion can be defined as a decline in reproductive potential or output over time. We studied seasonal maternal reproductive exhaustion in a large, freely mating captive population of white seabass (Atractoscion nobilis), a marine finfish cultured in southern California for conservation. Using genetic parentage data, we identified 34 single-maternity spawns produced during the 2008 spawning season and quantified four physical egg characteristics for each spawn, including egg volume (EV), oil volume (OV), percent oil volume (POV), and the number of oil globules (NOG). The mean batch egg measures decreased between the beginning and end of the spawning season by 19%, 45%, 33%, and 12%, respectively. OV and POV declined linearly, whereas the trend in NOG was parabolic and negatively correlated to water temperature and light duration, which reach apices mid-season. EV displayed a similar, though not significant, trend. We also evaluated the egg measures within and among six dames that solo-spawned two or more times. The seasonal trends were similar to those observed at the population-level, but the relative measures varied significantly among dames, indicating factors other than the common broodstock diet and holding conditions may influence egg production in individual A. nobilis females. In terms of species conservation, assessing these egg characteristics, some of which may be associated with larval quality in A. nobilis, in conjunction with estimating genetic diversity for each spawn is important when choosing spawns to rear for stock supplementation, but more research into their relationship with subsequent offspring quality is warranted. [Copyright &y& Elsevier]

Abstract: The development of the digestive system and digestive enzyme activity in white seabass larvae, Atractoscion nobilis, were analyzed from hatching until 40days post hatch (dph) using histological and biochemical approaches. The development of the digestive system in A. nobilis larvae was similar to that reported for other marine fish species. Larvae at 3dph (0.55±0.001mg wet weight and 3.6±0.02mm total length), cultured at 18°C in seawater, presented all the structures (i.e. differentiation of the alimentary canal into the buccopharynx, esophagus, anterior and posterior intestines, pancreas with zymogen granules, liver, gall bladder and open mouth) necessary for the digestion and absorption of nutrients such as proteins and lipids (primarily). At this time, the larvae had fully-developed digestive systems that allowed them to digest inert feed and to absorb nutrients throughout the intestine walls. On the other hand, most digestive enzyme activities were detected at the moment of hatching. Trypsin activity was 0.80±0.16mU/mg protein at 1dph (0.51±0.001mg wet weight larvae), and increased gradually during the following days, but most notably after the initial exogenous feeding at 4dph. The specific activity of chymotrypsin was 7.21±1.29mU×10−4/mg protein at 1dph and reached peak level (15.9±1.02 mU×10−4/mg protein) at 18dph (6.6±0.003mg wet weight larvae). The specific activity of leucine aminopeptidase increased continuously from 1.31±0.05mU×10−3/mg protein at 1dph to 15.91±0.40mU×10−3/mg protein at 18dph. The activity of α-amylase at 1dph was 1.35±0.09U/mg protein, increasing to 8.07±0.98U/mg protein at 16dph. The activity of pepsin was detected at a very low level (0.71±0.53U/mg protein) at 10dph, and a stepwise increase in activity was observed between 16 and 20dph, reaching maximum level (13.92±0.09U/mg protein) at 40dph. These results indicate that the digestive tract develops rapidly in this species and that the stomach becomes functional between 16 and 18dph. It should, therefore, be possible to start weaning the fish at this young age. [Copyright &y& Elsevier]

Surface disinfection trials were performed on eggs from three marine finfish species: California yellowtail (CYT; Seriola lalandi), white seabass (WSB; Atractoscion nobilis) and California halibut (HA; Paralichthys californicus). All three species were spawned from captive populations maintained at the Hubbs-SeaWorld Research Institute (HSWRI). Five disinfection treatments were used for each species; Treatment 1 included 100 mg L−1 of formalin (F100) for 60 min (current HSWRI treatment), Treatment 2 included 1000 mg L−1 of formalin for 15 min (F1000), Treatment 3 included povidone-iodine of 50 mg L−1 for 15 min (PI50), Treatment 4 included povidone-iodine of 100 mg L−1 for 10 min (PI100) and Treatment 5 involved a control with no chemical treatment (CONT). For each treatment, the per cent egg hatching rate, per cent survival to first feeding and notochord length at the time of hatching to the nearest 0.1 mm were recorded. Bacteria were also cultured from eggs after treatment to determine the effectiveness of each treatment in reducing the bacterial counts (CFU mL−1). Treatments F100, F1000 and CONT yielded the highest hatch rates for each species (70-80%), whereas treatments PI50 and PI100 yielded the lowest hatch rates (0-2%). There were no significant differences in survival to first feeding or notochord length, which suggests that the disinfection treatments did not have a negative effect on the yolk sac larvae. The PI50 and PI100 treatments had the lowest bacterial colony counts, showing almost zero bacterial growth. The highest bacterial growth occurred in the F100, F1000 and CONT treatments. Based on the results from this study, the F100 treatment provided the best balance of disinfection and larval health for CYT, WSB and HA. [ABSTRACT FROM AUTHOR]

The article presents the findings of a study on the measurements of total scattering spectra from bocaccio. The total scattering cross section was found to be equivalent to the one expected for a rigid sphere of diameter 90 millimeters in water. The total scattering cross-sectional areas was the same in each three frequency bands. The transfer of fish from Rayleigh domain to geometric regimes occurred at frequencies of 15 kilohertz.

In pelagic fish species, studying reproductive behaviour and spawning dynamics is challenging. In culture scenarios, these parameters are difficult to investigate for broadcast spawners such as Seriola. Hubbs‐SeaWorld Research Institute has been culturing California yellowtail (S. dorsalis) since 2003 and now it is poised to become one of the first commercial offshore aquaculture marine finfish species in Southern California. Brood fish are typically kept in large tanks and spawn volitionally throughout the spawning season. This method is successful in yielding a consistent supply of eggs; however, it limits the understanding of spawning group dynamics or individual brood fish contribution, information that will be important to scaling production to commercial levels. In this study, genetic‐based offspring parentage analyses were used to evaluate captive spawning dynamics in S. dorsalis over two consecutive spawning seasons. The analyses determined that typically one female released eggs during a spawning event, compared with an average of six males who released milt during these same spawning events. Notably, the analyses revealed that a single female dominated spawning output in both years, participating in 63 spawning events and producing 49.7 million eggs. The largest single spawn contribution by a female was 2.5 million eggs, corresponding to a batch fecundity estimate of 110,000 eggs kg−1. The spawning interval for the most productive females was 5–6 days. Using genetic tools to characterize spawning events will help to improve breeding programme designs for S. dorsalis, and this information can serve as a proxy for estimating spawning capacities of this species in the wild. [ABSTRACT FROM AUTHOR]

California yellowtail (CYT) Seriola dorsalis is a top candidate for aquaculture in southern California. CYT is fed commercial diets whose nutrient profile and ingredient composition rely heavily on fish meal and fish oil. We evaluated the complete replacement of fish oil and fish meal with a Schizochytrium‐derived algal oil as an essential fatty acid source and poultry by‐product meal and spirulina as primary protein sources, in the diet of juvenile CYT (average initial weight—19.95 ± 0.09 g). The treatment diets for this study included the following: FMF‐FO—fish meal free, fish oil; FMF‐AO—fish meal free, algal oil; FMF‐SO—fish meal free, soybean oil; FMC‐FO—fish meal control, fish oil. Each treatment diet was formulated to contain 45% protein and 15% lipid, and the trial lasted 64 days. At the conclusion of the trial, fish from FMC‐FO group had performed significantly better in three key performance metrics: final body weight of 185.96 ± 8.98 g, per cent weight gain of 832.7 ± 47.2% and lowest FCR of 1.16 ± 0.04. Replacing fish meal with poultry by‐product meal and spirulina resulted in 20% less weight gain. Replacing fish oil with algal oil, in a fish meal free diet, resulted in equal weight gain, and the fish had higher tissue essential fatty acid content. Based on the results from this trial, we have shown that in CYT juvenile diets, fish oil can be replaced with algal oil with no effect on growth or survival and fish meal can be replaced with no effect on survival and a 20% decrease in weight gain. [ABSTRACT FROM AUTHOR]

One of the key limitations in the use of artificial microdiets for the culture of marine fish larvae and post-larvae is their poor acceptability. The chemosensory systems of adult and juvenile fish are known to serve important roles in the detection and selection of food items; however, the relative importance and functionality of chemosensory detection and responses are less well understood for the larval stages. Many chemical compounds previously found to promote feeding in fish are low molecular weight, water-soluble compounds that are prone to rapid leaching from artificial microdiets. Particle taste, which requires retention of these low molecular weight water-soluble compounds, is difficult to manipulate in currently available larval diets. In the present study, we used liposomes embedded in alginate particles (alginate complex particles), that showed high retention of low-molecular weight water-soluble compounds, as a tool to evaluate the impacts of several water-soluble organic compounds on the feeding of California yellowtail (Seriola dorsalis) and white seabass (Atractoscion nobilis). We also compared the relative importance of including (and retaining) these compounds within the particles (enhanced taste) as opposed to dissolving these compounds in the culture water (enhanced smell). The results of this study showed that alginate complex particles retained >50% of sodium fluorescein and >70% of amino acids after 1 h suspension in seawater. Moreover, we found that feed consumption rates (feeding incidence and fullness) were greatest when a mixture of glycine, betaine and alanine were included in the complex particles suggesting that particle taste was an important factor for influencing the feeding of white seabass and California yellowtail post-larvae. • Alginate complex particles show high retention of liposome-encapsulated, water-soluble substances. • Feeding indices were highest when fish were fed on a mixture of glycine, betaine and alanine encapsulated within alginate complex particles. • Encapsulated substances had a greater impact on fish feeding than those that were dissolved in the water. • These results may inform the formulation of microparticulate artificial diets to improve their acceptability by marine fish larvae. [ABSTRACT FROM AUTHOR]

As marine finfish aquaculture expands, there is an increasing interest in the ability to ship early life stages from breeding centers to hatcheries. Here we conducted a 24 h air shipping simulation with eggs of white seabass (WSB; Atractoscion nobilis ). We examined the effects of a pH buffer on water quality, post-shipping egg survival, and subsequent hatching success, at egg densities of 1000, 5000, 10,000, and 15,000 eggs/L. The pH buffer, 8.3 Trizma®, was tested at varying concentrations of zero (NT = 0.00 g/L), low (LT = 0.75 g/L), medium (MT = 1.5 g/L) and high (HT = 3.0 g/L). Shipping densities up to 5000 eggs/L consistently yielded >70% survival immediately after simulated shipment, hatching success >70%, and >45% survival 48 h after the simulations, when Trizma concentrations were under 1.5 g/L. At those densities, pH was maintained at ~8.0 when buffered at a minimum Trizma level of 0.75 g/L. The highest densities of 10,000 and 15,000 eggs/L yielded lower survival 0–6% after 24 h, regardless of pH buffer concentration. Based on the results from these air-shipping simulations, we recommend WSB eggs be shipped in seawater with a maximum of 0.75 g/L Trizma® at densities no >5000 eggs/L. We believe this represents an important step in improving long distance transport protocols and provides useful guidance in air transport of other economically and ecologically important marine species. [ABSTRACT FROM AUTHOR]

Two eight-week feeding trials were conducted to evaluate the effect of dietary carbohydrate to lipid ratios on growth performance on juvenile California yellowtail Seriola dorsalis. In Trial 1, groups of twenty California yellowtail (ca. 6.8 g) were fed five iso‑nitrogenous diets that were formulated to contain decreasing levels of crude lipid from 21% to 6% by replacing menhaden fish oil with corn starch on a weight basis In Trial 2, groups of twenty fish (ca. 5.2 g) were fed five iso‑nitrogenous diets that were formulated using a similar matrix, corn starch 0–24% was used to replace lipids (11.3 to 1.3%) at approximately 2:1 ratio to maintain the diets with similar energy content and the nitrogen free extract (carbohydrates) from 10% to 30% of the diet Fish were fed 5–11% body weight per day over the course of both trials. Growth performance metrics including thermal-unit growth coefficients and protein retention efficiencies were measured and compared using a quadratic regression model. Fish that were fed diets containing high levels of dietary lipids (15% or higher) exhibited decreased growth performance in Trial 1. In Trial 2, fish that received diets containing the highest level of carbohydrates exhibited improved feed efficiency and overall performance. The results from both trials demonstrate that juvenile California yellowtail with a starting size of 5–7 g have an energy fraction preference and display increased growth when fed diets containing a carbohydrate to lipid ratio of up to 5.8. • California yellowtail juveniles fed diets containing up to 30% dietary carbohydrate exhibited improved feed efficiency and overall growth. • 15% lipid diets overburdened fish, with carbohydrate replacement of lipids improving overall growth performance. • Carbohydrate to crude lipid ratios as a fraction of dietary energy is important for California yellowtail feed formulations. • California yellowtail have an energy fraction preference. [ABSTRACT FROM AUTHOR]

It is likely that Seriola spp. have nutritional requirements for long-chain polyunsaturated fatty acids (LC-PUFAs) and are unable to meet physiological demand for these nutrients via biotransformation of C 18 polyunsaturated fatty acids (C 18 PUFAs). However, it is unclear whether 20:4n-6 (arachidonic acid, ARA), 20:5n-3 (eicosapentaenoic acid, EPA), and 22:6n-3 (docosahexaenoic acid, DHA) are each required or, as in other fish, EPA is comparatively unimportant in maintaining performance of Seriola spp. Accordingly, we assessed growth performance and tissue fatty acid composition of juvenile California Yellowtail Seriola dorsalis (formerly Seriola lalandi ) fed a fish oil-based positive control diet (FISH), a soybean oil-based negative control diet (SOY), or experimental diets based on soybean oil supplemented with ARA, EPA, DHA, ARA and DHA, or all three of these fatty acids combined to achieve 50% or 100% of the concentrations typically observed in fish oil (SOY + 50% ARA, SOY + 100% ARA, SOY + 50% EPA, SOY + 100% EPA, SOY + 50% DHA, SOY + 100% DHA, SOY + 50% ARA and DHA, SOY + 100% ARA and DHA, SOY + 50% ALL, SOY + 100% ALL). As expected, fish fed the SOY diet exhibited significantly reduced growth relative to those fed the FISH diet. Supplementing with ARA alone had no effect on growth performance, and independent supplementation with EPA or DHA did not yield predictably positive effects on growth. However, fish fed the SOY + 100% ARA and DHA feed grew as well as those fed the FISH diet, and those raised on the SOY + 50% ALL and SOY + 100% ALL diets outperformed all others. Fatty acid composition of the fillet, liver, eye, and brain tissues was significantly affected by dietary treatment. As expected peripheral tissues were more modified than central tissues, and tissues of fish fed the soybean oil-based feeds exhibited higher levels of 18:2n-6 and lower levels of LC-PUFAs than those fed the rest of the experimental feeds. This effect was less overt among feeds supplemented with ARA and DHA or all three fatty acids. Results indicate that soybean oil can completely replace fish oil in California Yellowtail diets, assuming adequate levels of DHA and ARA are provided. Furthermore results illustrate the value of supplementing fish oil-free feeds with ARA, EPA, and DHA, but suggest that ARA and DHA are the primary drivers of LC-PUFA essentiality in this species. Statement of relevance The current manuscript provides valuable insights for fish nutritionists, for the aquafeed and aquaculture industries regarding fatty acid essentiality for marine carnivorous finfish. Our study supports the hypothesis that some LC-PUFAs are more physiologically important than others, with DHA and ARA being the primary drivers of fatty acid essentiality for juvenile California Yellowtail. [ABSTRACT FROM AUTHOR]

There is interest in stock enhancement to support fisheries for California halibut Paralichthys californicus , a regionally important yet depleted species in the Southern California Bight (SCB), U.S. A quantitative model was developed to assess the cost of increasing harvestable California halibut in the SCB via releases of cultured juveniles. Reduced post-release survival of cultured juveniles was incorporated into the model, as was sex-specific lifetime survival, growth, and maturity. Simulations examined how adult California halibut population metrics were influenced by key release-strategy variables (i.e., size, number, survival, and sex ratio of released juveniles). A target increase in abundance of harvestable (≥ 559 mm total length; TL) California halibut by 5% in the entire SCB could likely be achieved by releasing large numbers (0.1–1.6 million per year) of larger-sized juveniles (40–200 mm TL). However, this was strongly mediated by their survival and sex ratio; fewer and smaller juveniles were required when releases comprised better surviving and / or more female individuals. Depending on the survival and sex ratio of released juveniles, increasing harvestable abundance in the SCB to achieve this 5% target was estimated to cost US$ 0.2–2.9 million annually, or US$ 14–219 per additional harvestable California halibut in the wild. This exploratory modeling study demonstrates that releasing juvenile California halibut could be a feasible management tool in the SCB, and provides a theoretical basis for field experiments. More broadly, it suggests that the allocation of resources to the production of larger and / or better surviving juveniles, in addition to optimizing release sex ratios, should be explored in stock enhancement programs. • Stock enhancement of California halibut was simulated by quantitative modeling. • Pre-defined target was achieved by releasing 0.1–1.6 million larger-sized (40–200 mm) juveniles. • Outcomes were strongly mediated by survival and sex ratio of released fish. • Annual costs to achieve the target were US$ 0.2–2.9 million. • Provides guidance for the allocation of resources in stock enhancement programs. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of increasing the carbohydrate to lipid ratio in diets supplemented with Bacillus subtilis in white seabass ( Atractoscion nobilis) juveniles on digestibility, growth performance, feed utilization efficiency and tissue composition. Four experimental isoenergetic and isoproteic diets supplemented with B. subtilis were formulated with increasing starch to lipid ratios (g/g) of 10:19; 14:17; 18:15 and 22:13 (diets PD10, PD14, PD18 and PD22 respectively). A negative control diet for B. subtilis supplementation was also formulated to be similar to diet PD10 (diet CD10). Each experimental diet was fed to triplicate groups of 20 fish per tank ( IBW: 9.5 g), three times a day, to apparent satiation, for 60 days. Supplementation with B. subtilis, of the low starch-high lipid diet (10:19), significantly enhanced the overall growth performance, digestibility and feed efficiency. Moreover, the increase in starch to lipid ratio, in supplemented probiotic diets, significantly increased growth performance, feed intake, feed utilization efficiency and protein and energy digestibility, being maximum for the highest dietary starch to lipid level. Lipid content of whole body, muscle and liver and hepatosomatic index significantly increased with the increase in starch to lipid ratio. The results of this study indicate that B. subtilis supplementation significantly enhanced growth performance, digestibility and feed utilization of low starch-high lipid diet. However, further improvement of growth performance and feed utilization efficiency may be achieved combining B. subtilis supplementation with increased dietary starch to lipid ratio to 22:13. [ABSTRACT FROM AUTHOR]

Like other carnivorous species, White Seabass typically demand a nutrient-dense feed. Research is ongoing to develop formulations that contain minimal amounts of marine-origin protein and lipid, i.e., fish meal and fish oil, as a mean of reducing production costs and pressure on reduction fisheries. Previous research has shown that a greater level of fish oil-sparing is possible with saturated fatty acid-rich, hydrogenated soybean oil than with C 18 polyunsaturated fatty acid-rich standard soybean oil. To confirm this observation and to assess whether docosahexaenoic acid (DHA) is a limiting factor in fish oil sparing with soy-derived lipids, we evaluated the performance and tissue fatty composition of juvenile White Seabass fed diets containing fish oil, or standard or hydrogenated soybean oil with or without the addition of an algal DHA supplement. In addition, a low temperature stress challenge was done after the feeding trial. Fish fed the hydrogenated soybean oil feeds exhibited growth performance equivalent to those fed the fish oil feed, regardless of DHA supplementation. Growth performance was impaired among fish fed the standard soybean oil feed compared to those fed the fish oil control feed, but the addition of DHA corrected this effect. Dietary treatments significantly affected fatty acid composition of fillet, liver, eye, and brain tissues. In terms of long-chain polyunsaturated fatty acids and n-3 fatty acids, the tissues of fish fed the hydrogenated soybean oil feeds were equivalent to those of fish fed the fish oil feed. Tissues of fish fed the standard soybean oil feeds exhibited significantly lower levels of these beneficial fatty acids; however, this effect was corrected by dietary DHA supplementation. The low temperature stress challenge induced elevated plasma cortisol, and reduced glucose, osmolality and hematocrit; though dietary inclusion of soybean oils did not appear to negatively affect stress tolerance. Results suggest that fish oil sparing in White Seabass feeds is limited by DHA, and that DHA bioavailability may be greater in the presence of hydrogenated soybean oil than standard soybean oil. [ABSTRACT FROM AUTHOR]

As marine finfish aquaculture expands, there is an increasing interest in the ability to ship early life stages from breeding centres to hatcheries so that each hatchery does not have to maintain its own broodstock. Here, we conducted 24 h air-shipping simulations with yolk-sac larvae of California yellowtail (CYT; Seriola lalandi) and white seabass (WSB; Atractoscion nobilis) to help fill in the informational gaps for shipping marine fish larvae. We examined the effects of a pH buffer on water quality, post-shipping larval survival and subsequent survival to first feeding at larval densities of 1000, 3000, 6000 and 9000 larvae L−1. The pH buffer, 8.3 Trizma®, was tested at varying concentrations of zero (NT = 0.00 g L−1), low (LT = 0.75 g L−1), medium (MT = 1.5 g L−1) and high (HT = 3.0 g L−1). Trials were conducted using replicate 2 L aquarium bags filled with 500 mL of seawater and held in a water bath at 19-20°C. Results showed an interspecific difference in survival at the highest shipping densities under these experimental conditions. Shipping densities up to 6750 CYT larvae L−1 or 3000 WSB larvae L−1 consistently yielded >90% survival immediately after simulated shipment and >85% survival 48 h after the simulations. Furthermore, at these densities, pH was maintained at ~8.0 when buffered at 1.5 g L−1. The highest tested densities of 9580 CYT larvae L−1 and 9940 WSB larvae L−1, yielded lower survival 69-79% and 0.0-1.3% respectively after 24 h. Final pH in the high density CYT trials were unsatisfactory (below 7.0), regardless of the buffer concentration; however pH in the WSB high density trials improved with increasing buffer concentration. On the basis of the results from these air-shipping simulations, we recommend CYT and WSB larvae be shipped in seawater with 1.5 g L−1 Trizma® at densities not greater than 6750 larvae L−1 for CYT and 3000 larvae L−1 for WSB. We believe this represents an important step in improving long distance transport protocols for these species and provides useful guidance in air transport of other economically and ecologically important marine species. Additional research is warranted to compare these simulation results with those from actual air shipments, as we did not account for factors that may vary in flight like temperature and pressure variations, and physical agitation. [ABSTRACT FROM AUTHOR]

A study was undertaken to examine the potential of two non-genetically modified (non-GM) soy products, differentially processed, as fishmeal (FM) replacements. Dietary protein (DP) was replaced at 50, 60 and 70% using the 3011 meal or 40, 50 and 60% with the 3032 meal. Ingredient 3011 was a cooked and solvent-extracted meal from a high protein and low oligosaccharide soy cultivar; whereas, ingredient 3032 was a cold-pressed, low fat cake ground to a meal that originated from a medium protein, low oligosaccharide, low protease inhibitor soy cultivar. Experimental diets were isonitrogenous (45% crude protein, CP), isolipidic (13% lipid), isocaloric (12.6 kJ energy kg − 1 of diet) and were balanced for lysine (3.2%) and methionine + cysteine (2%). Taurine was supplemented at 1.5% in all diets. A commercial control diet (52% CP and 13% lipid) was included for a total of eight test diets. Twenty four round tanks (330 L) were each stocked with 20, 4 g yellowtail ( Seriola lalandi ). Tanks were supplied with recirculated seawater and each diet was randomly assigned to three replicate tanks. After a 10-week feeding trial, growth, survival, feed conversion ratio, protein efficiency ratio, protein retention, condition factor and carcass proximate composition were contrasted among dietary treatments. Results indicate that juvenile yellowtail fed diets in which the 3032 meal provided 50 and 60% of DP grew significantly ( P < 0.001) better than those fed all other diets, including the FM-based (menhaden FM) and commercial control diets. Fish fed with the 3011 meal providing 50% of DP and those fed with the 3032 meal providing 40% of DP had similar growth performance which was slightly greater than the fish fed the FM reference diet. Minor intestinal histology differences were found among fish fed the 8 diets. Taken together these data indicates that the improved non-GM soybean meals supported better performance of juvenile yellowtail than fish fed the FM reference diet. No enteritis was detected even at high dietary inclusion levels. [ABSTRACT FROM AUTHOR]

Abstract: Two growth trials were designed to evaluate varying levels of taurine in diets for white seabass (WSB), Atractoscion nobilis. All diets were formulated to contain 40% protein and 10% lipid with a fixed level of fish meal (FM) and soybean meal (SBM). Trial A tested a series of six practical diets with 0.0, 0.1, 0.2, 0.3, 0.4, 0.5% taurine supplementation at the expense of glutamic acid, and a seventh diet with 0.5% cystine supplementation instead of taurine. Trial B was designed to test higher inclusion levels (0.2–1.6%) of taurine over six diets, while a seventh diet contained 1.6% taurine but no methionine supplement. In Trial A, the increased inclusion of taurine resulted in significantly improved final weight ranging from 14.6 to 26.6g, TGC ranging from 0.074 to 0.120, and feed efficiency from 68.2 to 111.9%. The supplementation of cystine to the diet did not result in an improvement in growth, indicating the synthesis of taurine from cysteine decarboxylation is inadequate in WSB. Similarly, in Trial B significant improvements in performance were observed with increasing taurine supplements, albeit variation in the data was higher. Final weight ranged from 23.6 to 29.7g, TGC ranging from 0.111 to 0.130 and feed efficiency from 75.6 to 81.4%. The diet with taurine supplement but without methionine showed a decrease in growth, suggesting that methionine was then limiting. Datasets from both trials were combined, and a saturation kinetics model was used to determine a dietary requirement of 0.99% of the diet (R2 =0.8770). Based on these results, white seabass have a dietary requirement for taurine presumably due to a limited ability to synthesize it. [Copyright &y& Elsevier]

Abstract: The present study aims to identify the limiting amino acids in low fish meal, soy-based diets in juvenile white seabass. Two 8-week trials were conducted. The first trial evaluated three diets containing 36, 18 and 9% fish meal in the diet (FM36, FM18, FM9, respectively), with the last two diets being supplemented with methionine and taurine. In the second trial, seven diets were formulated, including a high (36%) fish meal diet (HFM, similar to FM36) and five diets with medium (18%) fishmeal levels. These included an unsupplemented diet (MFM) and four with increasing levels of methionine (+M, +2M) and taurine (+2MT and +2M2T) supplementation. An additional diet was formulated with soy protein and poultry by-product meal to completely replace fish meal (PM). In trial 1, fish fed the FM18 diet grew significantly faster than fish fed the FM36 and FM9 diets. In trial 2, fish fed the +2M2T diet grew better than fish fed any other diets, and feed efficiency was highest in fish fed the +2M2T and PM diets. Fish fed the unsupplemented MFM diet had the lowest growth and feed efficiency. Methionine supplementation (+M and +2M) had a limited but significant effect on growth performance compared to MFM-fed fish. Fish fed the PM diet showed similar growth as those fed the +2MT and commercial diets, but was lower than +2M2T diet. Across both trials, growth rate was highly correlated with dietary taurine, except in diets containing less than 18% fish meal, i.e., diets PM and FM9. Both of these diets had equivalent or superior dietary taurine levels compared to diets +2M2T and FM18, but resulted in significantly poorer growth. This suggests that taurine is the first-limiting nutrient in feeds containing at least 18% fish meal while methionine was marginally deficient. In diets containing lower levels of fish meal however, methionine and taurine supplementation is ineffective; hence another (undetermined) nutrient became first-limiting. Additional research is necessary to identify this limiting nutrient, as well as determine the specific taurine requirement of WSB. [Copyright &y& Elsevier]

Abstract: We evaluate post-release dispersal, growth and survival of hatchery-reared white seabass (Atractoscion nobilis) released as part of an experimental stock enhancement program in California. Releases of hatchery white seabass have been carried out since 1986, year round either directly from the hatchery or after acclimation in net pens. All released fish are implanted with coded wire tags. Post-release monitoring is carried out through a research gillnet fishery for juveniles, and tag returns from the commercial and recreational fisheries. Fish dispersed from the release sites at a diffusion rate D 795km2 year−1, such that 50% of fish remained within 47km and 95% within 135km of the release site at the end their third year at large. The von Bertalanffy growth parameters for released hatchery fish were estimated at L ∞ =975mm SL and K =0.21year−1. A set of alternative survival models accounting for dispersal and size- and time-dependent natural and fishing mortality patterns was confronted with the mark-recapture data using model selection based on the Akaike Information Criterion (AIC). The model that fit the data best accounted for short-term post-release mortality dependent on season and release method in addition to a long-term size-dependent mortality. Survival of released hatchery fish was highest in Spring, moderately lower in Summer and Autumn, but much lower in Winter releases. Acclimatisation in net pens had a substantial, positive effect on survival relative to direct releases. Survival of hatchery fish to legal minimum length (600mm SL) in the fishery was estimated at 1.5% for a release size of 200mm, rising to 13.8% for a release size of 400mm, under optimal conditions (Spring releases with net pen acclimatisation). Mortality rates of hatchery white seabass under optimal release conditions were substantially below average for other hatchery fish released into the wild, but remained above those expected for wild fish in both, the short-term and long-term components. [Copyright &y& Elsevier]

Abstract: The California halibut (Paralichthys californicus) is a good candidate for aquaculture due to its good growth, survival and high commercial value. Several farms in the Western coast of North America are currently evaluating the potential of this species under commercial conditions. However, one of the main problems in the production of juveniles for commercial purposes is the high percentage of malpigmented fish obtained after metamorphosis (up to 80%). This problem seems to be related, among other things, to nutritional deficiencies during the larval period, in particular to the quantities and proportions of highly unsaturated fatty acids (HUFAs) in the diet. As a first approach to reduce malpigmentation, improve growth and determine the requirement for DHA in California halibut late larvae, we evaluated the effect of four levels of dietary DHA (0, 1, 2, and 4% of total fatty acids in the diet) on growth, survival, weaning success and pigmentation. DHA was administered to the larvae through enriched Artemia metanauplii. Larvae standard length and wet weight were taken during the initial stage of Artemia metanauplii supplementation (18days post hatch, dph); at the beginning of the weaning period (50dph); and at the end of the experiment (75dph). We quantified the amounts of total fatty acids in 18 and 50dph larvae. No significant differences on growth, survival and pigmentation as a result of increasing dietary DHA levels were found in 50dph recently settled juveniles. However, larvae fed the highest DHA level resulted in the highest growth and survival at the end of the experiment (75dph). Additionally, highest weaning success was achieved with this treatment. Significantly higher numbers of normally pigmented fish (ca., 33%) were obtained with the highest DHA level at 75dph compared to the low DHA levels (0 and 5%). However, since this treatment resulted in the highest survival, part of the population had abnormal pigmentation (ca., 30% of the population). Based on a second order polynomial regression, the recommended DHA level in the diet for pre-metamorphic larvae to attain adequate growth and survival as estimated here for recently settled California halibut at 50dph was 1.21% DHA of total fatty acids (TFA). However, for post-metamorphosis fish (75dph) highest pigmentation rates, growth and survival are obtained with 2.40% DHA of TFA in the diet during the Artemia feeding period. [Copyright &y& Elsevier]

Abstract: The objective of this study was to determine the optimum dietary lipid level of white seabass, Atractoscion nobilis, which is one of the most important species in California and Baja California for sport and commercial fisheries. Triplicate groups of fish were fed for 50 days with isonitrogenous experimental diets formulated with increasing lipid levels (2.6, 7.4, 11.6, 15.3 and 19.4% lipid) using menhaden oil as the lipid source. A commercial diet (CD, 49.9% crude protein, 14.7% lipid) was also fed to triplicate groups of fish. Survival throughout the growth trial ranged from 89 to 100% but the survival of fish fed the 2.6% lipid and the commercial diet was significantly less than the rest of the diets. Final mean body weight, feed conversion ratio (FCR), and nitrogen retention efficiency (NRE: N gain/N intake) were significantly greater for diets 15.3 L and 19.4 L compared to the rest of the treatments. Daily feed intake (DFI) was variable (3.5±0.08 to 8.6±0.03) and significantly affected by dietary treatment. Lipid content of whole body, muscle and liver increased with increasing dietary lipid levels. Muscle and liver fatty acid (FA) composition reflected dietary FA profiles. Tissue n−3 and n−6 highly unsaturated fatty acids (HUFAs) content increased in direct proportion to dietary lipid levels. [Copyright &y& Elsevier]

Abstract: A study was carried out to examine the effect of lipid level on growth and feed utilization of white seabass. Fingerling white seabass (27 days old, 0.65±0.05 g, 32±3.2 mm) were fed four formulated diets with four levels of lipid (15.5%, 18%, 19.5% and 21.5% of dry matter) at one level of protein (61% crude protein, dry matter (DM) basis) for six weeks. Survival exceeded 90% for all treatments. Weight gain (g) and specific growth rate (SGR, % day−1) values indicated that fish fed diets with 15.5% and 18% lipid exhibited higher growth performance. Lowest growth was recorded for fish fed diets with 19.5% and 21.5% lipid. Feed intake (FI, g fish−1) was also significantly (P <0.001) affected by dietary lipid levels and tended to decrease with increasing lipid levels. However, the fish that showed the highest FI were those that were fed the 15.5% and 18% lipid diets. Feed conversion ratio (FCR) values indicated that diets containing 19.5% and 21.5% lipid were more efficiently utilized. No significant differences in muscle composition were observed among fish fed the different diets. However, there was a strong linear relationship (P <0.05) between dietary lipid level and liver lipid. Hepatosomatic index (HSI) increased with dietary lipid level. Results indicated that fish performed best with the diets containing 15.5% and 18% lipid when protein concentration was 61.45±0.07%. And, reduced growth and increased body fat were evident when dietary energy increased from 24.2 to 24.9 kJ g−1. More work is needed to determine the precise dietary protein and carbohydrate requirements for this profitable aquaculture species. [Copyright &y& Elsevier]

Five cohorts of cultured California Yellowtail (Seriola dorsalis) were used in exercise training experiments to assess the duration of exercise necessary to induce a positive growth and fitness response, quantify the variability and replicability of this response between cohorts, and track the longevity (persistence) of exercise-induced benefits following removal from the exercise stimulus. Custom-designed raceways were used to continuously exercise juvenile yellowtail at their optimal swimming speed for two, three, or four weeks following which several fitness metrics including measures of somatic growth, white muscle fiber area, metabolic rate, and feed conversion were tracked for up to 20 weeks post exercise in comparison to non-exercised controls. Within a cohort, the longest duration of exercise (4 weeks) generally had the largest and longest-lasting impact on growth, followed by the 3-week, and then the 2-week exercise regimes. However, all exercise treatments showed substantial variability in the magnitude and longevity of the response between cohorts. For example, the positive growth response (increase in mass above that of controls) of the 4-week swimming group ranged from 9.8% to 37.8% between cohorts. This variability in the exercise response between cohorts is similar in magnitude to that associated with other experimentally manipulated variables in the exercise regimes of previous studies, and thus highlights the need for additional species-specific experiments to quantify replicability of positive exercise results. In addition, the longevity of exercise-induced benefits was highly variable between cohorts and generally not retained for prolonged periods post exercise. Most notably, the exercise-induced growth response which may result from muscle hypertrophy (increase in white muscle fiber size) during exercise, subsided within weeks. Taken together, these results indicate that exercise can play an important role in the growth and fitness of S. dorsalis and other species, however the duration of the exercise, as well as the timing of exercise in the rearing process likely have important implications for optimizing exercise training for aquaculture enhancement. • Increased exercise duration leads to increased growth and physiological benefits. • The magnitude of the growth response to exercise is highly variable between cohorts. • Exercise-induced physiological benefits diminish quickly post-exercise. [ABSTRACT FROM AUTHOR]

A 70-day trial was conducted to evaluate the effect of dietary protein matrix (soybean meal or poultry byproduct meal-PBM) on taurine efficacy and retention in juvenile white seabass Atractoscion nobilis. Diets were formulated to contain 40% protein and 12% lipids with taurine supplementation ranging from 0 to 1.37% taurine. Fish were fed 4–8% body weight/day over the course of the trial. Growth performance metrics and taurine retention in fish were measured and compared using a linear regression model with diet type as covariates (growth parameters) or a quadratic model with diet type as covariates (taurine retention and deposition). Fish fed diets with soy proteins had lower percent gain, survival, feed fed/fish, and thermal-unit growth coefficients (TGC) at similar levels of taurine inclusion when compared to diets with primarily PBM as the protein source. Taurine level was positively correlated with mean final weight, weight gain, percent gain, TGC of fish regardless of diet, and negatively correlated with FCR regardless of the diet. A taurine requirement based on whole-body deposition was calculated to be 1.18%, 1.21%, and 1.03% for all diets, PBM diets, and soy diets, respectively. These results demonstrate that the protein source did not influence the taurine requirement and suggest that taurine deficiencies are not the driver of lower TGC or survival in white seabass fed diets with soy, and that other factors warrant investigation. • White sea bass (WSB) were grown with varied taurine levels • The taurine requirement was lower in soy diets than poultry meal diets • There was no evidence of a conditional taurine requirement in WSB fed soy proteins [ABSTRACT FROM AUTHOR]

The lack of knowledge in what optimizes egg and larval quality is an important limiting factor in developing culture techniques for any species. Inconsistent or poor egg quality significantly affects the production of larval and juvenile fish. Egg quality is a known predictor of subsequent larval viability, quality, and stress resistance. Without high quality eggs, it is not possible to optimize husbandry practices. Here we tracked egg quality in a population of California yellowtail (Seriola dorsalis), CYT. We used spawn events from three consecutive years and monitored basic egg quality metrics such as: spawn viability, egg diameter, oil diameter, hatch rates, larval size at hatch, and larval survival to first feeding. Along with these metrics we also ran proximate composition and fatty acid analysis of these spawn events on the viable portion of the eggs collected. During this study we demonstrated that egg diameters for S. dorsalis decreased as the spawning season progressed and water temperature increased. We showed that larger eggs lead to higher quality hatched larvae, and that using eggs earlier in the season would lead to better overall larval and juvenile production. Our fatty acid analyses suggest that both arachidonic acid (ARA) and linoleic acid (LA) were limiting fatty acids in eggs produced, and there is potential to improve the quality of cultured CYT eggs with the addition of these fatty acids to the broodstock diet. • This study showed that egg diameters of S. dorsalis decrease as water temperatures increase. • Larger eggs lead to higher quality hatched larvae for S. dorsalis. • Arachidonic acid and linoleic acid were limiting fatty acids for S. dorsalis and should optimized for high egg quality. • This research adds important information on egg quality to help optimize culture of this important aquaculture species. [ABSTRACT FROM AUTHOR]