Overview of cod stocks, biology, and environment in the Northwest Atlantic region of Newfoundland, with emphasis on northern cod

Total landings of cod in the Newfoundland region (NAFO Divisions 2GHJ, 3KLMNO, and Subdivision 3Ps) increased from ~1 x 105 metric tonnes (t) in 1800 to ~4 x 1051 in 1950. Landings then increased to >1 x 1061 in 1968 and then declined to <2 x 105 1 by 1978. Landings again increased to 3.5 x 1051 in the 1980s and after 1988 dropped to <1 x 10s t. By 1993 the cod fishery throughout the majority of the region was closed. Northern cod (2J+3KL) spawner population estimates follow a temporal pattern similar to landings; current levels are at a record minimum of <1 x 10 and have been paralleled by a collapse in the size and age structure of the stock. Under the prevailing levels of fishing mortality, recruitment per spawner was below replacement from 1983 onwards, paralleling the stock decline. Recruitment determination is consistent with a parent stock-recruitment relationship. Widespread distributions of age 5+ cod, typically seen in the 1980s, became more aggregated toward the offshore, culminating in very few major aggregations along the shelf break in 1992. Winter- spring spawning throughout the region is protracted (3-4 months) and may be more frequent in inshore regions and on banks than has been previously perceived. The overall physiological condition of northern cod in more northerly regions has been decreasing since 1988, and only in the most recent years have capelin been virtually absent from the stomachs of cod in northerly regions. Lengths at 50% maturity have been declining since the early 1980s, particularly in northerly regions. Fishing mortality for northern cod was consistently >0.4 in the mid-1970s. The reduction of F to <0.4 during 1977 to 1980 was paralleled and followed by increases in the abundance of the spawner population. Slowly increasing fishing mortalities after 1980 accelerated after 1987. The combined effects of fishing mortality on spawning population size and reduction in length and age reduced fecundity contributions of older individuals. A recent examination of a salinity-recruitment relationship shows that with the addition of spawning-stock biomass estimates, recruitment estimates can be well modelled. A series of years characterized by better than average environmental conditions will likely be required to provide the good recruitment necessary to rebuild the stock size and length/age structure.

Article from Marine Science Symposia Vol. 198 - "Cod and climate change". Symposium held in Reykjavik, 23-27 August 1993. To access the remaining articles please click on the keyword "MSS Vol. 198".