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.

Mobile fishing gear reduces benthic megafaunal production on Georges Bank

“…Our estimates are likely not representative of the whole of Georges Bank as a result. Our values also bound the mean estimates for both Browns Bank and the Bay of Fundy of 64 and 199 g ww m -2 , respectively (Wildish & Peer 1983, Wildish et al 1989. Estimated scallop biomass at Site 17 in this study increased by approximately 200× (10 g m -2 in 1994 and 2075 g m -2 in 2000), a much higher rate than the 9-to 14-fold increase reported for all 3 of the closed areas on Georges Bank and the Nantucket Lightship combined (Murawski et al 2000).…”

Benthic habitat mapping on the Scotian Shelf based on multibeam bathymetry, surficial geology and sea floor photographs

“…Eighty taxa of megabenthos were distinguished from the bottom photographs and are comparable to the data provided by Thouzeau et al (1991), who described a total of 106 species of epifaunal megabenthos on Georges Bank identified from dredge samples. However, this is only 15% of the total number of macrobenthic taxa identified by Wildish et al (1989Wildish et al ( , 1990) from grab samples. Disregarding infauna may lead to undercounting of bivalves and polychaete species; these are the most diverse group on Georges Bank (Theroux & Wigley 1998).…”

“…Infauna is probably abundant, based on burrows of varying size and on traces of fish-feeding activity (numerous pits and trails on the surface of mud). In general, the deeper eastern part of the bank may be a suitable feeding area for groundfish due to dominance of deposit-feeders (Wildish et al 1989) which are otherwise responsible for a small proportion of total production (8.4%). The 1984-1985 sea floor photographs show that Nothriidae were present on gravel in the shallow part of the bank, in areas where shell hash provides enough material for building tubes.…”

Benthic epifauna assemblages, biomass and respiration in The Gully region on the Scotian Shelf, NW Atlantic Ocean

“…The distribution of benthic fauna on the Scotian Shelf has been documented in relatively few studies (Nesis 1965, Mills & Fournier 1979, Pocklington & Tremblay 1987, Wildish et al 1989, Kostylev et al 2001, Stewart et al 2001). Most studies have been restricted to shallow areas of the Scotian Shelf such as Banquereau, Sable, Emerald, Browns and Western Banks, and are primarily descriptive in nature.…”