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 (OFD; 18 mm pellet) to fresh fishery products (FFP; sardines and squid) and a commercial broodstock diet (Europa, Skretting; 12 mm pellet), when fed to California yellowtail (CYT; Seriola dorsalis). The aim was to determine how egg production, and egg and larval quality would be affected by these diets.
A total of sixteen F2 generation CYT broodstock (2 females; 2 males per tank) were held in four 10 m3 tanks under ambient temperature and photoperiod. In Year 1 we compared the OFD to FFP and in Year 2 we compared the OFD to Europa. During each year we alternated each diet twice over four 6-week periods through the spawning season. In Year 1 the OFD treatment yielded 10 spawn events totaling 5.4 million eggs, with an average viability of 59.9%, compared to the FFP treatment which yielded 15 spawn events for a total of 7.0 million eggs, with an average viability of 45.1% (Table 1). Egg and larval quality measurements (egg diameter, oil diameter, percent oil volume, notochord length at hatch, hatch rates, and survival to first feeding) were not statistically different between treatments. Results from Year 1 demonstrated that the OFD treatment performed similarly to the FFP treatment and lead us to compare the OFD treatment to a commercially available broodstock diet (Europa). In Year 2 the OFD 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%. Both treatments showed no significant differences in egg or larval quality. Based on the results from these trials, the OFD can be used in future experimental work as a tool to determine dietary needs for CYT broodstock.