Ticket to spawn: Combining economic and genetic data to evaluate the effect of climate and demographic structure on spawning distribution in Atlantic cod. (30th October 2018)

• Record Type: Journal Article
• Authors: Langangen, Øystein; Färber, Leonie; Stige, Leif C.; Diekert, Florian K.; Barth, Julia M. I.; Matschiner, Michael; Berg, Paul R.; Star, Bastiaan; Stenseth, Nils Chr.; Jentoft, Sissel; Durant, Joël M.
• Is Part Of: Global change biology. Volume 25:Number 1(2019)
• Page Start: 134
• Page End: 143
• Publication Date: 2018-10-30
• Subjects: climate change -- demography -- economic data -- genetic data -- size truncation -- spawning distribution; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.14474
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Climate warming and harvesting affect the dynamics of species across the globe through a multitude of mechanisms, including distribution changes. In fish, migrations to and distribution on spawning grounds are likely influenced by both climate warming and harvesting. The Northeast Arctic (NEA) cod ( Gadus morhua ) performs seasonal migrations from its feeding grounds in the Barents Sea to spawning grounds along the Norwegian coast. The distribution of cod between the spawning grounds has historically changed at decadal scales, mainly due to variable use of the northern and southern margins of the spawning area. Based on historical landing records, two major hypotheses have been put forward to explain these changes: climate and harvesting. Climate could affect the distribution through, for example, spatial habitat shifts. Harvesting could affect the distribution through impacting the demographic structure. If demographic structure is important, theory predicts increasing spawner size with migration distance. Here, we evaluate these hypotheses with modern data from a period (2000–2016) of increasing temperature and recovering stock structure. We first analyze economic data from the Norwegian fisheries to investigate geographical differences in size of spawning fish among spawning grounds, as well as interannual differences in mean latitude of spawning in relation to changes in temperature and demographic parameters. Second, we analyze genetically determined fish sampled at the spawning grounds to unambiguously separate between migratory NEA cod and potentially smaller sized coastal cod of local origin. Our results indicate smaller spawners farther away from the feeding grounds, hence not supporting the hypothesis that harvesting is a main driver for the contemporary spawning ground distribution. We find a positive correlation between annual mean spawning latitude and temperature. In conclusion, based on contemporary data, there is more support for climate compared to harvesting in shaping spawning ground distribution in this major fish stock in the North Atlantic Ocean. Abstract : Climate warming and harvesting affect the dynamics of species across the globe through a multitude of mechanisms, including distribution changes of spawning fish. For the Northeast Arctic cod, two major hypotheses have been put forward to explain these changes: climate and harvesting. Here, we evaluate these hypotheses by combining two sources of modern data: economic data from the Norwegian fisheries and genetically determined individual fish sampled at the spawning grounds. Our results indicate that demographic size truncation due to harvesting is currently not the dominating factor in shaping spawning ground distribution, but our results provide support for the climate hypothesis.