Causes of trends and fluctuations in the Arcto-Norwegian cod stock ...

• Main Author: Nakken, Odd
• Format: Report
• Language: unknown
• Published: ICES Marine Science Symposia (1991–2003) 2024
• Subjects: Ecosystem observation, processes and dynamics; Fisheries and aquaculture; Pressures, impacts, conservation, and management; Norwegian Sea ICES Ecoregion; Norwegian Sea
• Online Access: https://dx.doi.org/10.17895/ices.pub.19271207; https://ices-library.figshare.com/articles/report/Causes_of_trends_and_fluctuations_in_the_Arcto-Norwegian_cod_stock/19271207

Published information is used to review trends and fluctuations in landings and stock characteristics/variables (abundance, growth, maturation, distribution, and mi­grations) in relation to changes in environmental and anthropogenic factors as well as interactions with other species. The stock declined from about 4-5 million tonnes in the 1950s to less than 1 million tonnes in the 1980s owing to exploitation. For more than 30 years the annual fishing mortality rate was well above any calculated safe level, so that the spawning stock was at times reduced to levels at which recruitment was impaired. Age of maturity fell as the stock declined. Recruitment is positively related to temperature. A temperature-regulated mechanism of interaction between cod larvae and their prey, and driven by variations in inflows of Atlantic waters to the area, determines larvae survival and probably also the abundance and size of the 0-group at age 5-6 months. Predation from birds and marine mammals as well as cannibalism are ...