Aggregate fish biomass and yield on Georges Bank, 1960-1987

Abstract

Declines in overall production can be attributed largely to the collapse of the herring Clupea harengus population by 1976-1977 under heavy exploitation. Recent increases in biomass of elasmobranchs and principal pelagic species (herring and mackerel Scomber scombrus) have resulted in further shifts in system structure. The biomass of piscivores is currently high and this shift may act synergistically with increasing exploitation rates to cause further declines in biomass of commercially desirable species. -from Authors