Vertical and Horizontal Distribution Patterns of Copepods Near the Shelf Break South of Nova Scotia

Abstract

The shelf water over the outer edge of the Scotian Shelf and the shelf/slope water front at the shelf break south of Nova Scotia have been sampled with a Batfish cycling over a 3- to 110-m-depth range while measuring salinity, temperature, depth, chlorophyll a, and copepods. Plant production and copepod abundance were much higher at the front than in surrounding shelf and slope waters. Convergence at the front is invoked as a possible transport mechanism which results in the accumulation of copepods in a region of high food concentration. Copepods exhibit diel vertical migration in shelf water but not in the front itself, and possible mechanisms are examined. Most Batfish profiles (with ≈1-m-depth resolution) indicated that the copepod maximum was situated ≈10 m above the chlorophyll maximum. A series of vertical profiles consisting of chlorophyll a, estimated production, and copepod abundances indicate a high correlation between the copepod and production profiles and low correlation between either of these and chlorophyll. Possible relationships between copepod layer depths and the depths of high plant production are considered.Key words: copepods, batfish, chlorophyll, production, front, migration