The striped bass, Morone saxatilis, is an emerging new aquaculture species in the U.S. due in large part to its rapid growth rate and ability to be grown to 1.3 – 2.3 kg (3-5 pounds) within a 24-month production cycle in salinities ranging from freshwater to full-strength seawater. The successful culture of this species has been advanced by successive generations of selective breeding and domestication that has improved growth characteristics by around 8% per generation. Our previous work in the omnivorous tilapia demonstrates that feeding on alternate days improves feed efficiency by 50% relative to fish fed daily with little impact on growth or yields in ponds supplemented with fertilizers to enhance natural foods. It is unclear however whether reducing the frequency of feeding might provide benefits to feed efficiency or labor costs in the growout of the carnivorous striped bass. To this end we evaluated the production characteristics of fifth generation selectively bred striped bass fed either 3x/week or every other day on Mon., Wed., and Fri., versus those fed 5x/week or everyday (Mon – Fri). Fish (60 g) were stocked in 1080-L tanks at 30 fish/tank with 5 replicates per group and grown for 5 months and then transferred to larger 2125-L tanks (4 replicates per group) and grown out for an additional 7 months. Both groups of fish were fed to satiation on their respective days of feeding and weights and lengths of fish was assessed periodically (every 2-3 months) throughout the study.
Within 2-months of initiation of the growth trial, mean weight of fish fed 5x/week was significantly higher (121 g) than fish fed 3x/week (109 g). This growth difference persisted throughout the course of the study. By12 months at the termination of the study, fish on a 5x/week feeding schedule attained an average final body weight of 1298 g while those fed 3x/week had an average body weight of 1094 g (P < 0.05). Fish fed 5x/week had a marginally better, 2.7% improved overall feed conversion ratio (FCR), relative to fish fed 3x per week (FCR: 1.485 versus 1.525). However, the FCR changed with fish age. Fish fed 5x/week initially had lower mean FCR (1.397 versus 1.487) over the first 6- months, a similar FCR (1.563) at around 9 months, and a higher FCR (1.667 versus 1.586) between 9-12 months of the growth trial relative to fish fed 3x/week. A plot of the FCR indicated the shift in FCR with age occurs at around 475 g body weight.
Results indicate that shifting from daily to alternate-day feeding after fish reach 475 g may reduce feed costs by 13% and labor costs by 19%, respectively, while maximizing growth and feed efficiency of domesticated striped bass grown in recirculating aquaculture systems.
This work was supported by the USDA and NOAA-National Sea Grant (StriperHub).