Changes in Lipid and Fatty Acid Composition of Wild Freshwater Zooplankton during Enrichment and Subsequent Starvation

Abstract

Concentrated wild zooplankton harvested from freshwater ponds have been used to feed the larvae of hybrid striped bass (female white bass Morone chrysops × male striped bass M. saxatilis) in tanks. However, larval growth and survival have been superior when cultured rotifers and brine shrimp Artemia spp. nauplii have been offered as first feeds. We hypothesized that enrichment with highly unsaturated fatty acids (HUFAs), which is common for cultured zooplankton, would enhance the nutritional value of wild freshwater zooplankton. Wild zooplankton were enriched for 24 h with Super Selco, a formula rich in HUFAs. Lipid and fatty acid composition changes in wild freshwater zooplankton were monitored during the enrichment period and the subsequent 72 h. Total lipids in wild zooplankton increased from a preenrichment level of 38 mg/g dry weight (DW) to 72 mg/g DW after enrichment. Although wild zooplankton were initially deficient in HUFAs, the HUFA level after enrichment was 10.41 mg/g DW, which was above the recommended level for good growth and survival of hybrid striped bass larvae. The nutritional state of wild zooplankton returned to the preenrichment level 24 h after enrichment was terminated. Therefore, enriching wild zooplankton from culture ponds for 24 h after harvesting and concentration offers producers another nutritional option for hybrid striped bass larvae during the early life history stages.