The distribution of copepods in the Shubenacadie River Estuary relative to the diet of larval striped bass (Morone saxatilis)

Abstract

The distribution of both copepods and larval striped bass were quantified in the upper estuary (25-40 river kilometer) from May to August 2016 and 2017. Examining the distributions of larvae and potential prey relative to time of year and salinity was important to test the Match-Mismatch Hypothesis. The abundance of first-feeding stage striped bass (6mm total length, TL) peaked at 463/m3 May 29-June 4th, 2016, and 595/m3 June 12-18th, 2017, in 1-10ppt salinity. Larvae were broadly distributed from tidal freshwater to 25.0ppt. The larvae were ‘gape limited’ and failed to feed until late June due to the absence of prey of suitable size. Once feeding commenced, the initial prey was a small adult harpacticoid (0.8-1.0mm TL) of the family Ectinosomatidae, genera possibly Halectinosoma or Pseudobradya based on DNA and morphological analysis. Daily mean abundance of this copepod was 209-281/m3 in salinities of 1.1-2.0ppt in June 2017. Once larvae started growing, larger prey included copepods (Coullana canadensis and Pseudodiaptomus pelagicus) and mesoplankton (mysids and amphipods).