The Atlantic cod (Gadus morhua) has historically supported one of the largest marine fisheries, however, as with many commercially exploited species; it has undergone a significant reduction in recent years, which has resulted in the complete closure of some major fishing grounds [1].
Geographical Distribution of the Atlantic Cod
The distribution of the Atlantic cod extends from eastern North America across the north Atlantic to western Europe. Both inshore and offshore stocks are known. Cod gather in large breeding congregations in spring. These areas are known to fisherman and some have been fished for centuries [1].
History of the Atlantic Cod Fisheries
The newly discovered fisheries off the coast of Newfoundland in the 1500s were being fished by the French, English, Portuguese and Spanish fisherman who used single baited hooks. The fish were harvested exclusively from inshore waters, until the French developed a Canadian off-shore fishery, quickly followed by other European countries [1].
Stock Trends of the Atlantic Cod
In the 1950s and 1960s additional off shore fishing grounds east of Newfoundland were discovered, which increased annual landings [1]. In 1910, with gradual improvements of technology catches reached about 300,000 tons. By 1968, over 800,000 tons were reported accounting for 40% of global fish landings. In 1971, an armada of 900 large factory trawlers were at the fishing grounds and annual harvests during this time period often removed 60% of adult cod [2].
Fishing-induced Changes in Life-History Characteristics of Atlantic Cod
Changes to life history traits in species, often coexist with prolonged periods of exploitation, exacerbating negative impacts on population growth resulting from ecosystem-level alterations to interspecific competition and predation In the Atlantic cod, 30 to 40 year declines of more than 90% of the population have been associated with significant reductions in age and length at maturity, explained as genetic responses to fishing [1].
Fishing-induced Evolutionary Changes in the Atlantic Cod
It is suggested that the impact of commercial fishing is so great that it is affecting the evolution of some fish species, and that changes may be occurring in only decades that under normal circumstances would take millennia [1].
Trophic Cascades and Atlantic Cod Practices
The decline of one species can have impacts that reverberate throughout the ecosystem in a domino-like fashion, represented in a trophic cascade [1].
Habitat Alteration from Atlantic Cod Fishing Practices
Certain types of fishing gear can damage the physical structure of marine habitats as they pass over the ocean floor. Bottom trawls used to capture demersal fish species and dredges used to capture scallops have been shown to be particularly damaging to sensitive [1].
Management of the Atlantic Cod
Early attempts to protect Atlantic cod stock included (1) establishing a minimum mesh size for trawl nets in an attempt to allow small, undersized fish to escape (2) a reduction in total allowable catch (TAC) and (3) the establishment of a 200-mile fishing limit by the U.S. and Canada [1].
The Recovery of the Atlantic Cod
Reasons for slow recovery are not completely understood. However the flowing suggestions have been offered by fisheries scientists; fishing continues to have an impact, non-directed fishing and by-catch, altered biological systems, the removal of a top predator such as cod can alter relationships among species in a community, and changes to life history; the effects truncate age distributions, loss of genetic variability and adaptability [1].