Striped bass (Morone saxatilis) is an emerging new cultivar in the U.S. due to its ability to grow rapidly up to 1.3 - 2.3 kg (3 - 5 pounds) within a 24-month production cycle. The feasibility of cultivating this species has increased with successful domestication and many years of selective breeding for improved growth characteristics. Relatively little is known on the growout of this species in Recirculating Aquaculture Systems (RAS), including feeding strategies that might reduce feed and labor costs. Our research suggests that feeding striped bass every other day (3x/week) instead of daily (5x/week) to satiation may improve feed efficiency while having little impact on growth performance, particularly at larger body sizes. Fish grown from 475 to 800 g on alternate day feeding had a similar and at body weights > 850 g an improved FCR relative to fish fed daily. We further tested if feeding fish on alternate day at a reduced feeding rate could improve feed conversion efficiency and the amount of feed required to grow fish to market size relative to daily fed fish. We investigated the effects of feeding daily (7x/week) vs. alternate day (3-4x/week) on striped bass growout. Fish (500 g) were fed daily througout a 253 day period. Fish on the alternate day feeding regime were fed at the following rates relative to fish fed daily to satiation: 50% for 0-89 days and 75% for 90-253 days. Alternate day fish were subsequently shifted to daily feeding at 100% rate to that of the daily fed group until reaching 2 kg body size. The results show that 0.5 kg striped bass fed daily grew very rapidly to 2 kg (6 g/day) over only 253 days. By day 89 fish fed daily had significantly higher weights and lengths then alternate day fed fish that persisted throughout the course of the study. However, fish fed at 75% rate showed a similar specific growth rate and 17% improved FCR during the 90-253 day growth interval relative to daily fed fish suggesting that feeding at this rate on alternate days may improve production efficiency of striped bass in RAS.
To this end, we have undertaken an additional on-going growth trial of domesticated striped bass that will be grown to a final semicommercial density of 0.7 kg/L (0.6 lbs/gallon) at a 2 kg harvest size. Striped bass were raised in RAS from 4.5 g to 890 g on daily satiation feeding in freshwater supplemented with NaCl (3-5 ppt, 21-24C). Fish were then fed on alternate days (3 times/week, MWF) at 78% of the rate of daily fed fish (6 times/week, MTWTFS) for 3 months (N = 4 tanks/group, 84 fish/1900-L tank). Weight of fish fed on alternate day was 6.9% lower (1.352 ± 0.003 kg) than daily fed fish (1.454 ± 0.004 kg, Mean ± SEM), while FCR was similar among groups (1.73 alt day vs 1.72 daily). Mortalities were 1.78% and 0.60% for the alternate and daily fed groups, respectively. Total feed consumption was 22% less for the alternate day group. These results suggest that a significant savings in labor costs is possible with implementation of an alternate day feeding strategy in larger striped bass (> 800 g) grown in RAS with relatively little impact on production. The feed management protocol will be carried out until fish reach 2 kg to further ascertain if production efficiency can be improved. This work was supported by NOAA-National Sea Grant (StriperHub) R/22-AQUA-06.