Zooplankton Selectivity by Black Buffalo in Fertilized Ponds

Abstract

Populations of the Black Buffalo Ictiobus niger, a catostomid species, are in decline. Recovery plans for catostomids frequently include artificial propagation and rearing in ponds until fish grow beyond sizes that are considered vulnerable to predation. Managing ponds for specific zooplankton taxa should increase survival and growth of larval fish; however, zooplankton selectivity experiments conducted for catostomids in aquaculture are rare. We conducted two experiments to evaluate zooplankton selectivity by larval and juvenile Black Buffalo in aquaculture ponds. Fry were stocked into tanks or ponds and were allowed to forage on natural zooplankton populations. Fish and zooplankton were sampled after 3 h in tanks and weekly for 4 weeks in ponds. Proportions of zooplankton taxa consumed were compared to the proportions of taxa available in tanks or ponds. Results indicate that Black Buffalo fry do not readily consume zooplankton at first feeding. However, Black Buffalo at 11 d posthatch (1 week poststocking) selected for cladocerans, and they continued selecting for cladocerans through the first 32 d posthatch (4 weeks poststocking). Therefore, rearing ponds for larval and juvenile Black Buffalo should be managed to promote cladoceran populations where possible.