Search

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]

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]

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]