Benthic Macrofaunal Production of Browns Bank, Northwest Atlantic

Abstract

Benthic macrofauna of the coarse sediments of Browns Bank, off southwest Nova Scotia, Canada were sampled with a modified 0.5-m2 Van Veen grab; 29 stations from 1983 to 1985. Production was estimated from alcohol-stored biomass by multiplying by the annual turnover ratio, P:B, of each species. The latter was determined from an empirically derived relationship using known or estimated lifespans. Benthic macrofaunal production averaged 64 g wet weight∙m−2∙yr−1 on Browns Bank, markedly lower than the 193 g wet weight∙m−2∙yr−1 in the mixed and finer sediments of the Bay of Fundy. Other community characteristics, such as the number of polychaete and amphipod species for the two areas were similar, which we attribute to the similar geological ages of the sediments. Prey consumed by juvenile age 0 haddock (Melannogrammus aeglefinus) consist mostly of deposit-feeding macroinfauna which produce ~1.8 × 104 t wet biomass per year, representing ~8% of the total production of Browns Bank. Two linked hypotheses are proposed to account for the suitability of Banks as juvenile gadid feeding grounds: rapid rates of suspension of macrofauna by strong tidal currents; and drifting animals are of a suitable size and kind for juvenile haddock feeding.