Studies on Ergasilus labracis Krøyer (Cyclopidea: Ergasilidae) parasitic on striped bass, Morone saxatilis, from the lower Chesapeake Bay. I. Distribution, life cycle, and seasonal abundance.

Abstract

Information on the distribution, life cycle, and seasonal abundance of the copepod Ergasilus labracis Krøyer, parasitic on the gills of lower Chesapeake Bay striped bass, Morone saxatilis (Walbaum), is presented after a 12-month survey. The overall prevalence of E. labracis was 90% in all localities sampled and it was found to be as euryhaline as its host; it has been found in salinities from 0.l‰ to 32.0‰. E. labracis was present and reproductively active throughout the year, suffering only a temporary slowdown in egg production at the beginning of the winter. Peak invasion of striped bass gills by infective larvae occurred during April and May; minor peaks were also recorded during July and October. The free-living stage was estimated to last as long as 6 weeks during early spring. Duration of other developmental stages was also extrapolated. Attempts to rear larvae in the laboratory past the metanauplius stage failed. Larvae could be kept for a maximum of 23 days after hatching if fed nannoplankton and kept at 20 °C in river water of 16–18‰.