Limits...
Historical Arctic Logbooks Provide Insights into Past Diets and Climatic Responses of Cod.

Townhill BL, Maxwell D, Engelhard GH, Simpson SD, Pinnegar JK - PLoS ONE (2015)

Bottom Line: Gadus morhua (Atlantic cod) stocks in the Barents Sea are currently at levels not seen since the 1950s.These new analyses support existing knowledge about how the ecology of the region is controlled by climatic variability.When viewed in combination with more recent data, these historical relationships will be valuable in forecasting the future of Barents Sea fisheries, and in understanding how environments and ecosystems may respond.

View Article: PubMed Central - PubMed

Affiliation: Centre for Environment, Fisheries & Aquaculture Science (Cefas), Lowestoft, Suffolk, United Kingdom.

ABSTRACT
Gadus morhua (Atlantic cod) stocks in the Barents Sea are currently at levels not seen since the 1950s. Causes for the population increase last century, and understanding of whether such large numbers will be maintained in the future, are unclear. To explore this, we digitised and interrogated historical cod catch and diet datasets from the Barents Sea. Seventeen years of catch data and 12 years of prey data spanning 1930-1959 cover unexplored spatial and temporal ranges, and importantly capture the end of a previous warm period, when temperatures were similar to those currently being experienced. This study aimed to evaluate cod catch per unit effort and prey frequency in relation to spatial, temporal and environmental variables. There was substantial spatio-temporal heterogeneity in catches through the time series. The highest catches were generally in the 1930s and 1940s, although at some localities more cod were recorded late in the 1950s. Generalized Additive Models showed that environmental, spatial and temporal variables are all valuable descriptors of cod catches, with the highest occurring from 15-45°E longitude and 73-77°N latitude, at bottom temperatures between 2 and 4°C and at depths between 150 and 250 m. Cod diets were highly variable during the study period, with frequent changes in the relative frequencies of different prey species, particularly Mallotus villosus (capelin). Environmental variables were particularly good at describing the importance of capelin and Clupea harengus (herring) in the diet. These new analyses support existing knowledge about how the ecology of the region is controlled by climatic variability. When viewed in combination with more recent data, these historical relationships will be valuable in forecasting the future of Barents Sea fisheries, and in understanding how environments and ecosystems may respond.

No MeSH data available.


Related in: MedlinePlus

Total cod total stock biomass (blue) in the Barents/Norwegian Sea (ICES sub-areas I and II) from 1916–2013 (1916–1945 from Kjell Nedreaas, IMR, Bergen pers. comm., [40]; 1946–2013 from [13]), compared with a Climate Index (green) for the Barents Sea (1900–2009) [39].
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4557987&req=5

pone.0135418.g001: Total cod total stock biomass (blue) in the Barents/Norwegian Sea (ICES sub-areas I and II) from 1916–2013 (1916–1945 from Kjell Nedreaas, IMR, Bergen pers. comm., [40]; 1946–2013 from [13]), compared with a Climate Index (green) for the Barents Sea (1900–2009) [39].

Mentions: Atlantic cod has become emblematic of climate influences in fish and fisheries [30], and Barents Sea cod are of particular interest, being at the northernmost boundary of the species range at some of the lowest temperatures experienced by the species [31–32]. Temperature directly relates to population size, with a period of warmer temperatures in the Kola section of the south-eastern Barents Sea from 1930–1960 corresponding with high cod catches and biomass, and a cooler period from 1960–2000 corresponding with lower catches and biomass [17, 33]. Barents Sea cod tend to produce stronger year classes in warmer years [34], and there is evidence of a 50% increase in growth rates from the pre-1920s to the 1960s [15, 35]. When warm copepod and euphausiid-rich Atlantic water is brought in from the Norwegian Sea, the warmer temperatures may increase the habitable area for plankton and associated fish stocks, increasing local abundance of cod prey such as capelin Mallotus villosus and herring Clupea harengus [36]. Following cod spawning, spatial distribution depends on annual ocean currents that carry the larvae and juveniles from spawning grounds along the coast of northern Norway, north and east into the Barents Sea. Current-driven spatial distributions of juvenile cod determine the depths and temperatures experienced later through to the immature stages, thus affecting growth rates and ultimately adult size [37]. In cold years, the size of feeding areas appears to be reduced, with effects on year class strength [38]. Since the 1990s, Kola section annual mean temperatures have increased to ~5°C, and spawning stock biomass (SSB) and total biomass have rapidly risen to levels even higher than the previous warm period. The environmental conditions in the Barents Sea, as illustrated by a Climate Index in Fig 1 based on air temperature, Atlantic water temperature and ice cover [39], correlate closely with these trends in cod biomass [13, 40].


Historical Arctic Logbooks Provide Insights into Past Diets and Climatic Responses of Cod.

Townhill BL, Maxwell D, Engelhard GH, Simpson SD, Pinnegar JK - PLoS ONE (2015)

Total cod total stock biomass (blue) in the Barents/Norwegian Sea (ICES sub-areas I and II) from 1916–2013 (1916–1945 from Kjell Nedreaas, IMR, Bergen pers. comm., [40]; 1946–2013 from [13]), compared with a Climate Index (green) for the Barents Sea (1900–2009) [39].
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4557987&req=5

pone.0135418.g001: Total cod total stock biomass (blue) in the Barents/Norwegian Sea (ICES sub-areas I and II) from 1916–2013 (1916–1945 from Kjell Nedreaas, IMR, Bergen pers. comm., [40]; 1946–2013 from [13]), compared with a Climate Index (green) for the Barents Sea (1900–2009) [39].
Mentions: Atlantic cod has become emblematic of climate influences in fish and fisheries [30], and Barents Sea cod are of particular interest, being at the northernmost boundary of the species range at some of the lowest temperatures experienced by the species [31–32]. Temperature directly relates to population size, with a period of warmer temperatures in the Kola section of the south-eastern Barents Sea from 1930–1960 corresponding with high cod catches and biomass, and a cooler period from 1960–2000 corresponding with lower catches and biomass [17, 33]. Barents Sea cod tend to produce stronger year classes in warmer years [34], and there is evidence of a 50% increase in growth rates from the pre-1920s to the 1960s [15, 35]. When warm copepod and euphausiid-rich Atlantic water is brought in from the Norwegian Sea, the warmer temperatures may increase the habitable area for plankton and associated fish stocks, increasing local abundance of cod prey such as capelin Mallotus villosus and herring Clupea harengus [36]. Following cod spawning, spatial distribution depends on annual ocean currents that carry the larvae and juveniles from spawning grounds along the coast of northern Norway, north and east into the Barents Sea. Current-driven spatial distributions of juvenile cod determine the depths and temperatures experienced later through to the immature stages, thus affecting growth rates and ultimately adult size [37]. In cold years, the size of feeding areas appears to be reduced, with effects on year class strength [38]. Since the 1990s, Kola section annual mean temperatures have increased to ~5°C, and spawning stock biomass (SSB) and total biomass have rapidly risen to levels even higher than the previous warm period. The environmental conditions in the Barents Sea, as illustrated by a Climate Index in Fig 1 based on air temperature, Atlantic water temperature and ice cover [39], correlate closely with these trends in cod biomass [13, 40].

Bottom Line: Gadus morhua (Atlantic cod) stocks in the Barents Sea are currently at levels not seen since the 1950s.These new analyses support existing knowledge about how the ecology of the region is controlled by climatic variability.When viewed in combination with more recent data, these historical relationships will be valuable in forecasting the future of Barents Sea fisheries, and in understanding how environments and ecosystems may respond.

View Article: PubMed Central - PubMed

Affiliation: Centre for Environment, Fisheries & Aquaculture Science (Cefas), Lowestoft, Suffolk, United Kingdom.

ABSTRACT
Gadus morhua (Atlantic cod) stocks in the Barents Sea are currently at levels not seen since the 1950s. Causes for the population increase last century, and understanding of whether such large numbers will be maintained in the future, are unclear. To explore this, we digitised and interrogated historical cod catch and diet datasets from the Barents Sea. Seventeen years of catch data and 12 years of prey data spanning 1930-1959 cover unexplored spatial and temporal ranges, and importantly capture the end of a previous warm period, when temperatures were similar to those currently being experienced. This study aimed to evaluate cod catch per unit effort and prey frequency in relation to spatial, temporal and environmental variables. There was substantial spatio-temporal heterogeneity in catches through the time series. The highest catches were generally in the 1930s and 1940s, although at some localities more cod were recorded late in the 1950s. Generalized Additive Models showed that environmental, spatial and temporal variables are all valuable descriptors of cod catches, with the highest occurring from 15-45°E longitude and 73-77°N latitude, at bottom temperatures between 2 and 4°C and at depths between 150 and 250 m. Cod diets were highly variable during the study period, with frequent changes in the relative frequencies of different prey species, particularly Mallotus villosus (capelin). Environmental variables were particularly good at describing the importance of capelin and Clupea harengus (herring) in the diet. These new analyses support existing knowledge about how the ecology of the region is controlled by climatic variability. When viewed in combination with more recent data, these historical relationships will be valuable in forecasting the future of Barents Sea fisheries, and in understanding how environments and ecosystems may respond.

No MeSH data available.


Related in: MedlinePlus