The reliable production of marine finfish is contingent on the quality of the eggs available from the broodstock populations . Inconsistent egg production or poor egg quality will negatively impact the production of juvenile fish available for grow out . Proper broodstock nutrition is critical for maintaining a supply of good quality eggs. Here we have compared a commercial broodstock diet (Vitalis) to fresh sardines and squid diet, when fed to California yellowtail (CYT; Seriola dorsalis), to determine the dietary impact on egg production and quality.
The first diet (Diet 1) was a commercial diet (Vitalis Prima, Skretting) and was fed in a 6 mm pellet form. The control diet (Diet 2) was a combination of frozen sardines and squid supplemented with a vitamin premix. Each diet was fed twice over 6 week periods throughout the spawning season (March through September) of a single broodstock population. Diet 1 was fed from weeks 0 to 6 and from 14 to 21; Diet 2 was fed from weeks 7 to 13 and from 22 to 28 to the same fish population . There were nine CYT F1 brood fish (three females; six males) that were 7 years old and averaging 13.2 kg each . The fish were held in a 30 m3 tank under ambient water temperature and photoperiod conditions.
Diet 1 feeding perio ds yielded 19 spawn events totaling 10.8 million eggs, with an average viability of 86.2% . When the f ish were fed Diet 2, they spawned 28 times for a total of 20.4 million eggs, with an average viability of 84.3%. Egg quality measurement s ( egg diameter, oil diameter, percent oil volume, notochord length at hatch, hatch rates, and survival to first feeding) were not statistically different between treatments . Proximate composition and fatty acid analysis have yet to be completed. Results from this trial demonstrate that this commercial diet is comparable to the standard fish and squid feeding regime when looking at egg quality. However, the reduced egg output from the fish on the commercial diet needs to be explored.