Studies of striped bass in three Chesapeake Bay spawning habitats

Abstract

Comparisons were made of in situ striped bass prolarval and yearling studies conducted in the Nanticoke River in 1984, Chesapeake and Delaware Canal (C&D Canal) in 1985 and Potomac River in 1986. Experiments with striped bass prolarvae were performed in all three years; yearling experiments were conducted in 1985 and 1986. Water quality parameters, inorganic contaminants and organic contaminants were evaluated daily from 24 h composite samples taken during each study. Percent cumulative survival of striped bass prolarvae in the Nanticoke River was less than 10% after 96 h exposure at three field locations during two experiments. Acidic conditions, aluminium and soft freshwater (low buffering capacity) were suspected in causing the poor prolarval survival. Percent cumulative survival of striped bass prolarvae tested in the C&D Canal was 42–59.5% after 96 h of exposure at three field stations during two experiments. Mortality was not attributed to acute contaminant and water quality effects. All yearling striped bass exposed to habitat water for 10 d at the three field stations survived. However, histological effects (lamellar dilations) were reported. Percent cumulative survival of striped bass prolarvae exposed to Potomac River water ranged from 4.5–22.5% during three 96 h experiments at three field stations. Poor survival of prolarvae was attributed to various inorganic contaminants (monomeric aluminium, cadmium, and copper) and sudden decreases in water temperature. Yearling survival in the in situ Potomac River studies ranged from 0–77.5% at the three field locations during two 7 d experiments. High pH conditions and inorganic contaminants were suspected in causing mortality of this life stage. Histological changes in the kidney were also observed in yearlings exposed to Potomac River water. Striped bass prolarval and yearling survival from in situ tests was compared with a juvenile index used by the state of Maryland to assess striped bass production. Only at one site (Nanticoke River, 1984) did the prolarval survival data from the in situ tests predict the quality of Maryland's junvenile index. Reasons why these two parameters do not and should not always correlate are discussed.