Scotian Shelf large marine ecosystem

Source: NOAA

Introduction

caption Map of Scotian Shelf. (Source: NOAA)

The Scotian Shelf Large Marine Ecosystem (LME) surrounds the Canadian province of Nova Scotia, and extends to the shelf break, more than 200 nautical miles (nm) from the coast at some points. To the north it is separated from the Newfoundland Labrador Shelf LME by the Laurentian Channel. To the South it extends to the Fundian Channel (Northeast Channel). The Scotian Shelf LME has a complex topography consisting of numerous offshore shallow banks and deep mid-shelf basins. It tends to be divided into eastern and western systems. The eastern Scotian Shelf includes Emerald Bank. The Nova Scotia Current hugs the coastline in a southwestward direction and enters the Gulf of Maine through the Northeast Channel. For a general summary and comments on this LME, see Zwanenburg, 2002, and Hempel, 2002.

Productivity

The Scotian Shelf LME is considered a Category II ecosystem (moderately high productivity, 150 -300 gC/m2-yr) according to SeaWiFS global primary productivity estimates. Productivity in this LME is influenced by changes in environmental conditions and temperature. A decrease in ambient temperature is noted on the eastern Scotian Shelf. (Zwanenburg et al., 2002). There is a lack of long term data for many of the trophic levels within this system. There is a need for more monitoring and research. The recent changes to research vessel survey protocols broaden the collection of ecosystem monitoring data to include abundance and distribution of phytoplankton, zooplankton, as well as an increased suite of physical oceanographic parameters. A monthly Continuous Plankton Recorder Survey (CPR) is being conducted in collaboration with the Allister Hardy Foundation, Plymouth, England. A recent initiative by Canada and the United States, entitled the East Coast of North America Strategic Assessment Project (ECNASAP, see Brown et al, 1996), is an attempt to gather and synthesize additional physical and biological data for the east coast of North America, from Cape Hatteras to the Labrador Shelf.

Fish and Fisheries

caption Graph of Scotian Shelf. (Source: NOAA)

Systematic fishery surveys of the shelf made between the 1960s and the present are the richest and most consistent source of information available concerning this Large Marine Ecosystem. Changes in distribution patterns and changing growth rates appear to be a response to changes in environmental conditions. There were significant declines in abundance and size for many commercially exploited fish species on both eastern and western subareas of the shelf, indicating that the limits of exploitation had been reached. The decrease in size, related to fishing effort, occurred both on the eastern shelf and on the western shelf. For information on demersal fish communities in response to exploitation, see Pauly et al (2001). The trawlable demersal biomass declined from a maximum of 450,000 metric tons in 1973 to less than 15,000 tons in 1997. However, total finfish biomass has shown an increase since the mid 1980s. The pelagic fish biomass also increased, although it showed fluctuations between 1970 and 1997. There has been an exponential increase in grey seal abundance since the 1960s. Harp, hooded, and harbor seals are found in the Gulf of St. Lawrence domain, and so are Beluga whales.

Fishing effort increased rapidly with the establishment of Canada’s 200-mile Exclusive Economic Zone in 1977. The commercially exploited fish include capelin, turbot, Atlantic halibut, white hake, silver hake, cod, haddock, and pollock. Pelagic species include the Atlantic herring and the Atlantic mackerel. Invertebrates include snow crab, northern shrimp and short fin squid. Both snow crab and northern shrimp prefer cold water and the increased landings for both those species coincide with the cooling of the eastern shelf (for more information on shrimp, see Scotian Shelf Shrimp and its integrated management plan ). There has been a recent increase in landings of less utilized species such as monkfish, cusk, white hake, and skate. A management scheme taking into account species interaction and biomass production is being initiated to address the overexploitation of the LME’s main fisheries (cod, haddock, flounder, and other demersal fish). When the cod fishery collapsed on the Eastern shelf, a cod moratorium was imposed in 1993 and remains in effect. Overfishing led to a number of fishery closures in the early 1990s.

A recent initiative by Canada (DFO) and the United States (NOAA), entitled the East Coast of North America Strategic Assessment Project (ECNASAP, see Brown et al, 1996), gathered and synthesized data on the biological components of the east coast of North America, from Cape Hatteras to the Labrador Shelf. Also review Zwanenburg et al for decadal changes in the Scotial Shelf LME. The University Of British Columbia Fisheries Center have produced information on fish catch statistics for this LME.

Pollution and Ecosystem Health

caption (Source: NOAA)

For information on marine pollution and the protection of this LME’s offshore environment, see Environment Canada (EC) and the Canada-Nova Scotia offshore petroleum board's (CNSOPB) joint project . There is a need to assess the wider ecological costs of over exploitation of the fisheries resource (See Hollingworth, 2000). The effects of the fisheries on the biophysical habitat are not well understood. More research is needed on the local and internal processes and externalities that affect the system, such as El Niño and levels of Greenhouse gas emissions. The International GLOBEC Cod and Climate Change Program (CCC) studies the response of different cod populations to climate changes in various regions of the cod’s North Atlantic range, including the Scotian Shelf. Canada is a key participant in SCOR (Scientific Committee for Ocean Research) and ICES (International Commission for Exploration of the Sea).

Socioeconomics

The Scotian Shelf ecosystem has been exploited for hundreds of years. Exploitation intensified with the arrival of the Europeans in the 15th century. Their arrival saw the commercialization of the cod fishery. Since then, commercialization has intensified with the development of more efficient technologies and the expansion of markets. After World War II, the development of distant water international fleets increased the level of exploitation of the Scotian Shelf fisheries to the point of collapse in the mid 1970s. The Canada-Nova Scotia offshore petroleum board (CNSOPB) is responsible for the regulation of petroleum affairs in the province. The presence of oil raises issues of multiple uses of the marine environment.

Governance

caption (Source: NOAA)

The Scotian Shelf Large Marine Ecosystem falls under the jurisdiction of the Canadian province of Nova Scotia. The fisheries of the Scotian Shelf after 1945 were regulated under ICNAF (International Commission for the Northwest Atlantic Fisheries), consisting of all the industrialized fishing nations of the world operating in that area. ICNAF’s effectiveness, however, was limited by the voluntary nature of compliance to its rules. The limited development of Canada’s domestic fleet prompted Canada to establish a 200-mile Exclusive Economic Zone in 1977. Single species quota management continues. While there is a stated desire to change to an ecosystem level approach (see the web site for the Eastern Scotian Shelf Integrated Management Project), there are no explicit objectives within fisheries management plans for the ecosystem. The results of the activities of the many single-function management agencies would be better served by an integrated approach to management objectives.

References



Disclaimer: This article is taken wholly from, or contains information that was originally published by, the National Oceanic and Atmospheric Administration (NOAA). Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the National Oceanic and Atmospheric Administration (NOAA) should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.

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Citation

(2008). Scotian Shelf large marine ecosystem. Retrieved from http://www.eoearth.org/view/article/51cbeed57896bb431f69a9c3

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