Evaluation of Phase I Hybrid Striped Bass Culture Techniques Using Stable Isotope Analysis

Using d¹³C and d¹⁵N stable isotopes, we investigated the role of supplemental feeding of phase I hybrid striped bass Morone chrysops × saxatilis in plastic-lined ponds. During the 2010 culture season, d¹³C and d¹⁵N ratios of age-0 hybrid striped bass, zooplankton, and benthic invertebrates were tracked over a 4-week period at Rathbun Fish Hatchery. Within six 0.04-hectare plastic-lined ponds, stable isotope signatures were compared between fed and non-fed treatments. We found no significant differences in final fish total length, final weight, survival, or specific growth between treatments. Prior to the initial day of feeding, there were no significant differences in d¹³C or d¹⁵N between treatments for zooplankton, benthic invertebrates, or hybrid striped bass. By the end of the 31-d culture season, d¹⁵N of all three groups in the fed treatment were significantly higher than in the non-fed treatment (+5.83‰; +3.99‰; +3.92‰ respectively). Using a multiple source mixing model, we estimated the diet of hybrid striped bass in the fed treatment to consist primarily of benthic invertebrates and Silver Cup^TM Trout Diet. Although the feed supplemented the diet of hybrid striped bass, consumption of natural prey (zooplankton and benthic invertebrates) remained substantial during the culture period (~50-70%).