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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]

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]

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]

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]