Scotian shelf (Eastern) - Exploitation

Exploitation of the fisheries of the Scotian Shelf started in about 1560. By 1709 Nova Scotia was exporting about 10,000 t of cod and 4,000 t of mackerel and herring. By 1806 this had increased to about 40,000 t, and to over 100,000 t by the 1880s. In 1973 total landings of fish from the Scotian Shelf exceeded 750,000 t. In the early 1990s many of the east coast cod fisheries, including that of the eastern Scotian shelf, collapsed and were closed. For demersal fish species only the halibut longline fishery and some flatfish fisheries are currently operating on the Eastern Scotian Shelf. In addition to the overall reduction of biomass of commercially exploited fishes, the overall size structure and condition of the demersal fish communities has declined. Reduced numbers of larger fish can have significant negative impacts on long-term recruitment success; smaller fish produce fewer eggs that are less viable. This combination of effects may seriously impair the populations’ ability to sustain or rebuild itself or a fishery. Since the collapse of the groundfish fishery, the fishery on the eastern Scotian Shelf has switched to lower trophic level invertebrates such as lobster, sea scallop, snow crab and shrimp. These species have increased in abundance since the collapse of groundfish, likely due to a combination of predator release and cooler water temperatures, and have created a very lucrative fishery for some.
Fisheries have many, and variable, ecosystem impacts including bycatch, which is the catch of non-target organisms during actual fishing operations. The overall impact of the trawl fisheries on the Scotian Shelf is not restricted to the commercially important species but includes in excess of 50 to 400 additional species. We estimate that they exert exploitation rates ranging from less than 1% of estimated biomass per annum to values in excess of 50% of estimated biomass. Impacts on fish communities include changes in community dominance, size spectra, and trophic structure. Ecosystem impacts of fisheries also include physical impacts on the habitat.
While there may be debate about the extent and long-term implications of the impacts of fishing, there is no doubt that the use of hydraulic clam dredges, otter trawls, scallop dredges and bottom-tending longlines is affecting (has affected) benthic habitat and communities within the ESSIM area.

Adapted from : Zwanenburg, K.C.T., A. Bundy, P. Strain, W.D. Bowen, H. Breeze, S.E. Campana, C. Hannah, E. Head, and D. Gordon. 2006. Implications of ecosystem dynamics for the integrated management of the Eastern Scotian Shelf. Can. Tech. Rep. Fish. Aquat. Sci. 2652: xiii + 91 p.