Abstract The reliable production of marine finfish is contingent on the quantity and quality of the eggs available from the broodstock. Proper broodstock nutrition is critical for maintaining a supply of good quality eggs. Here, we compared an open‐formula reference diet (OFRD; 18 mm pellet) and a commercial broodstock diet (Europa, Skretting; 12 mm pellet) when fed to California yellowtail (CYT; Seriola dorsalis ). The aim was to determine if egg production and quality were impacted by these formulated diets. A total of 16 F2 generation CYT broodstock (2 females; 2 males per tank) were held in four 10 m 3 tanks under ambient temperature and photoperiod. We alternated each diet twice over four 6‐week periods through the spawning season. The OFRD‐fed fish spawned 20 times and produced 16.9 million eggs with an average viability of 53.6%, while the Europa‐fed fish spawned 21 times and produced 18.1 million eggs with an average viability of 53.8%. There were no significant differences in total eggs produced, viability rates, egg morphometrics, hatch rates, or survival to first feeding. There were significant biochemical differences between the diets as well as in notochord length at hatch. Based on the results from these trials, the OFRD can be used in future experimental work as a tool to determine dietary needs for CYT broodstock.

Microbial loading in hatchery-raised white seabass larvae and live feed systems is occasionally monitored through selective, culture-based methods, but comprehensive microbial characterization and tracking using next generation sequencing tools have yet to be performed. In this study, the microbiota of larval white seabass (Atractoscion nobilis) and culture water were assessed under the varying parameters of probiotic treatment, live feed selection, and time. 16S rRNA amplicon sequencing was performed to characterize bacterial microbiota within samples and achieved an average depth of 164,413 reads per sample. The factor that contributed most to larval microbiota variability was time (weighted UniFrac: n = 71, R2 = 0.202, p = 0.001). Secondarily, the larval microbiota differed from their surrounding culture water (weighted UniFrac: n = 60, R2 = 0.063, p = 0.001). Probiotic treatment with INVE Aquaculture’s Sanolife® MIC led to incorporation of the probiotic into the microbial community but did not impact the presence or abundance of other bacterial taxa. The probiotic treatment had no effect on larval growth or survival. Substitution of Artemia with rotifers for the first feeding did not have a significant impact on larval or culture water microbiota. Throughout larval development, the most dominant bacterial phyla in the fish were Pseudomonadota (Proteobacteria) and Bacteroidota (Bacteroidetes). Vibrio spp. peaked in larval fish during the early feeding stages (5–18 dph) and coincided with turbulence in bacterial alpha diversity. Tenacibaculum, a possible opportunistic pathogen of white seabass, was initially overrepresented in the culture water, but did not become present in the larvae until 46 dph. Neither Vibrio nor Tenacibaculum appeared to cause disease or mortality. This study helps to characterize microbial patterns in fish aquaculture, which can identify bacterial species to be monitored in consecutive life stages.

Liposome-enriched rotifers were used to (1) determine the optimal concentrations of dietary taurine and (2) evaluate the effects and interactions of vitamin C and taurine on California yellowtail (Seriola dorsalis) larvae. A 15-day growth study (Trial 1) was conducted whereby Seriola larvae were fed liposome-enriched rotifers with six levels of dietary taurine. At the end of the trial, larval individual dry weights (mg larva−1) and whole-body taurine concentrations were significantly affected by dietary taurine concentrations. Based on the latter, we estimate the dietary taurine requirement for 2–17 days post hatch (dph) S. dorsalis to be 7.5 mg g−1 (95

Existing broodstock research has ascertained that eggs are heavily influenced by broodstock diet, but there is currently sparse information regarding the time it takes for nutrients to transfer into eggs after broodstock feeding. Thus, our study aimed to quantify this duration of broodstock to egg nutrient transfer by feeding two alternating diets. In 2021, nine California yellowtail (Seriola dorsalis) broodstock were fed alternating diets of commercial pellets (Vitalis Prima: Skretting, Norway) and cutbait (70% sardine and 30% squid). These diets were switched every 41 days and then repeated so each diet was provided twice during the study. Biochemical and biometric data from spawns were collected and statistically analyzed by grouping spawns based on diet type and diet duration. Between diet switches, we observed a selective retention of C18:3n-3 (alpha-linolenic acid) and C18:2n-6 (linoleic acid) from the Vitalis diet, and C20:5n-3 (eicosapentaenoic acid), from the cutbait diet. Our results showed overall fatty acids from both diets were incorporated by the eggs after 10 to 19 days of feeding. Knowing this timing of nutritional incorporation from broodstock diet to eggs will help significantly improve feed efficiency by providing producers with a specific timeframe to maximize egg quality through dietary modifications or supplements.

The ability to control egg production and have a consistent supply of high quality eggs is critical to the commercial success of any farmed marine finfish species. Here we describe the first documented controlled spawning of California yellowtail (CYT; Seriola dorsalis). The aim for this study was to shift volitional spawning six months ahead of when natural spawning typically occurs for the species using photothermal manipulation. Over the course of one year we tracked spawning for two sibling groups of F1 generation broodstock and recorded relevant metrics for all spawn events (egg production, viability), eggs (egg and oil diameters, hatch rates), and larvae (notochord length at hatch, yolk sac volume, survival to first feeding). The first group was subjected to natural day length and temperature conditions (Natural) and produced eggs from March through October in 2023. The second group had a shifted day length and temperature regime (Controlled) designed to stimulate spawning from October 2022 through April 2023. Egg production for both groups was similar, with the Natural group producing 37 spawns resulting in 25 million eggs (682,086 f 299,821 eggs spawn-1), and the Controlled group producing 34 spawns resulting in 20 million eggs (604,825 f 315,412 eggs spawn-1). Egg quality was also similar, with only hatch rate being different between the groups (Natural 48.8 f 28.9 %; Controlled 75.1 f 15.5 %). Through the control of temperature and day length, we demonstrated that CYT spawning can occur outside the natural spawning window and that achieving year round egg production is possible. This is an important step forward for commercial production of this high value marine finfish species.

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.

The goal of this study was to test a commercial scale larval rearing tank with a self-cleaning mechanism to improve larval rearing success for marine fish. Four trials were conducted to compare the performance of a self-cleaning tank (SCT) to a control (CON) larval rearing tank. Two trials were conducted using California yellowtail (CYT; Seriola dorsalis) and two were conducted using white seabass (WSB; Atractoscion nobilis). Metrics collected for each trial included, larval growth, survival, bacterial colony counts (Vibrio spp.), total suspended solids concentrations, and labor (time spent siphoning the tanks). There were no differences in growth between tanks for either species. CYT survival in Trial 1 resulted in better survival in the CON tank (56.8%) than in the SCT (32.8%). WSB survival in both Trial 1 and 2 was higher in the SCT than in the CON tank (35.5% versus 26.9% and 15.8% versus 10.1%, respectively). We suspected that the cleaning arm was likely causing early mortality in both species (between 0 and 16 days post hatch; dph), therefore, Trial 2 involved only cycling the arm twice per day for one hour until the larvae were 16 dph. This modification yielded improved survival in the SCT (60.5%) than CON tank (47.1) but only for the CYT. Total suspended solids were higher in the CON tank for both species (up to 8.0 mg/L). Bacteriology results showed higher CFU counts for CYT in the CON tanks from 8 to 24 dph, and at 24 dph counts were higher in SCT. CFU counts were higher for WSB in the CON tank at 9 and 13 dph but otherwise there were no differences over time. Perhaps most notable was that the SCT tanks yielded a fourfold reduction in labor when compared to CON tanks due to more efficient siphoning.

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.

Objective: California Yellowtail (CYT) Seriola dorsalis are continuous spawners and rely entirely on their diet to supply nutrients like fatty acids (FAs) to their eggs to support early development. The objective of this study was to determine whether commercial diets could replace a diet consisting of fresh fishery products (FFP-D) without compromising egg quality and biochemical composition, specifically FAs.Methods: In 2017, one broodstock group (one female and two males) was fed a formulated reference feed (REF-D; Bio-Oregon). This pilot experiment showed that it was possible for a minimum of one female and two male broodfish to spawn repeatedly in a tank, a finding that led to a replicated diet experiment during 2018 in which 18 CYT broodfish were divided into six replicate tanks, with one female and two males per tank. Three tanks were fed the FFP-D as a control, and three tanks were fed a commercial diet (COM-D; Breed-M, INVE). For each spawning event, egg quality metrics were collected, along with samples for FA analysis.Result: The 2017 REF-D treatment produced eggs that met arachidonic acid (ARA) and eicosapentaenoic acid (EPA) requirements and had egg metrics comparable to those obtained from the FFP-D, with higher viability and average batch fecundity. However, the REF-D treatment had insufficient docosahexaenoic acid (DHA) and no tank replicates. The 2018 COM-D treatment produced eggs with large egg and oil diameters and met ARA and EPA requirements but was associated with very poor spawning and hatch success and had insufficient DHA levels. The FFP-D treatment produced below-average viability and batch fecundity rates and was unable to meet most essential FA requirements, but it yielded the greatest number of spawning events.Conclusion: None of the experimental treatments, including the control, was able to fully meet the nutritional requirements of CYT broodstock. These results reveal crucial data about current CYT broodstock diets that can facilitate future research for developing nutritionally complete diets, especially in terms of essential FAs.

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.

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 degrees 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 degrees C (46.3 +/- 2.7%) and the fewest at 23 degrees C (5.7 +/- 1.0%). Continued efforts to eliminate malpigmentation, in particular pseu-doalbinism, during intensive larviculture of California halibut will focus on additional modifications of key nutritional and environmental parameters.

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 ju-venile 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 (CYT)Seriola dorsalisis 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 aSchizochytrium-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.

Correspondence Federico Rotman, Hubbs-SeaWorld Research Institute, 2595 Ingraham Street, San Diego, CA. Email: frotman@hswri.org Abstract California yellowtail (CYT; Seriola dorsalis) is a promising candidate for marine aquaculture in the United States because there is an existing market and cultured Seriola spp. command prices as high as $27.70 per kg for head-on gutted product. Methods for commercial-scale Seriola spp. fingerling production and growout have been refined globally in recent years. Spawning can be accomplished without hormone therapy and adults spawn viable eggs when ambient water temperatures are between 15 and 22 C. Larval culture of CYT includes rotifers and Artemia, with the addition of greenwater. Larval survival to 1 g juveniles (45 days post hatch) is typically high at 30–60%. However, poor swim bladder inflation and skeletal malformations require culling and can reduce this yield substantially. Growout of CYT to market size at Hubbs-SeaWorld Research Institute (HSWRI) has been completed on a very limited basis in flow through tanks where it takes 18–24 months to achieve a market weight of 3.5–4.0 kg. While culture of this species is commercially ready from a technical and business perspective, research is still needed to improve swim bladder inflation, reduce deformities, optimize nutrition across all life stages, and assist with disease diagnosis and control. Most notable among bottlenecks to commercialization in the United Received: 6 January 2021 Revised: 30 April 2021 Accepted: 6 May 2021

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.

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.

California halibut (CH; Paralichthys californicus ) is a highly valued species that supports a commercial and recreational fishery along the Pacific coast of the United States. This species is considered a promising aquaculture candidate in California, with interest for both food production and stock replenish-ment. Culture of CH has been done on a small scale, showing that it is technologically feasible to rear this species commercially. Broodstock maturation and egg production can be accomplished without hormone therapy. Survival from egg to juvenile (~50 dph) can be as high as 30%. Juvenile growout to market size has been done on a limited basis, and it takes 3 years to reach a market size of 1 kg. There is a live market for CH in California and it is currently being supplemented by the importation of Paralichthys olivaceus . The known disease agents affecting CH are ectoparasites (i.e., Trichodina sp ), endoparasites (i.e., Anisakis sp .), and bacterial agents (i.e., Pseudomonas sp .). While culture of this species is technologically feasible, research still needs to be done in certain areas in order to realize commercial readiness. These areas include: nutrition, selective breeding, of all female populations; improved pigmentation; and developing methods for disease prevention and control.

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.

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.

The roles of dietary taurine on fish reproductive output and larval development remain poorly understood. A 2-year experiment was conducted where broodstock where fed a taurine-supplemented (2.67% dry diet) or non-supplemented (0.28% dry diet, control) diet, and larvae were fed taurine-enriched or standard-enriched prey, resulting in a 2 x 2 factorial design. Buoyancy, fertilization rate, and fecundity were the main drivers in characterizing eggs from each broodstock group. All these metrics were improved in the taurine-supplemented treatment. Newly-hatched larvae from the taurine-supplemented broodstock had significantly larger yolk-sac volume and 53% more likely to survive to 1st-feeding than those from the control broodstock. All larvae from the control broodstock and fed the control larval diet died by 15 dph, highlighting the essentiality of taurine in this species. However, 30 dph larvae from the treatment where both broodstock and larvae received supplemental taurine were significantly shorter and lighter than those from the other treatments. In conclusion, these results support the importance of dietary taurine in reproductive performance in yellowtail broodstock. Further research is necessary to better understand the interaction between supplementation in broodstock and larval diets.