THE DISTRIBUTION AND ABUNDANCE OF PELAGIC GAMMARID AMPHIPODS ON GEORGES BANK AND NANTUCKET SHOALS

In this study, long-term, broad-scale zooplankton survey data were use d to estimate the temporal and spatial distribution and abundance of g ammarid amphipods present in the water column on Georges Bank. Delta-m ean abundances computed from 10 years of data showed that gammarid amp hipod abundances peaked in summer and again in fall. The amphipods wer e also most numerous in water less than 50 m deep. The statistical tes ts employed revealed no conclusive evidence for diurnal vertical migra tion. Interannual delta-mean abundances fluctuated approximately 5-fol d between 1977 and 1986, ranging from 217 to 1181 amphipods 100 m(-3). Peak amphipod biomass occurred in July and was estimated to be 2.8 kc al m(-2). Using production-to-biomass ratios from the literature, mean annual production of amphipods in these samples was estimated to be b etween 1.6 and 9.8 kcal m(-2). Production in shallow areas was especia lly high, 22 kcal m(-2) year(-1). Copyright (C) 1996 Elsevier Science Ltd.