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Forecasting the major influences of predation and environment on cod recovery in the northern Gulf of St. Lawrence.

Bousquet N, Chassot E, Duplisea DE, Hammill MO - PLoS ONE (2014)

Bottom Line: This sensitivity study shows that water temperature is key in the rebuilding of the NGSL cod stock.Model projections suggest that maintaining the current management practice under cooler water temperatures is likely to maintain the species in an endangered status.In the medium-term, a management strategy that reduces catch could be favoured over a complete moratorium so as to minimize socio-economic impacts on the industry.

View Article: PubMed Central - PubMed

Affiliation: Institut de Mathématiques de Toulouse, UMR 5219 CNRS, Université Paul Sabatier, Toulouse, France.

ABSTRACT
The northern Gulf of St. Lawrence (NGSL) stock of Atlantic cod (Gadus morhua), historically the second largest cod population in the Western Atlantic, has known a severe collapse during the early 1990 s and is currently considered as endangered by the Committee on the Status of Endangered Wildlife in Canada. As for many fish populations over the world which are currently being heavily exploited or overfished, urgent management actions in the form of recovery plans are needed for restoring this stock to sustainable levels. Stochastic projections based on a statistical population model incorporating predation were conducted over a period of 30 years (2010-2040) to assess the expected outcomes of alternative fishing strategies on the stock recovery under different scenarios of harp seal (Pagophilus groenlandicus) abundance and environmental conditions. This sensitivity study shows that water temperature is key in the rebuilding of the NGSL cod stock. Model projections suggest that maintaining the current management practice under cooler water temperatures is likely to maintain the species in an endangered status. Under current or warmer conditions in the Gulf of St. Lawrence, partial recovery might only be achieved by significant reductions in both fishing and predation pressure. In the medium-term, a management strategy that reduces catch could be favoured over a complete moratorium so as to minimize socio-economic impacts on the industry.

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Linear regression of cod condition .The adjusted Pearson's coefficient , with value .
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pone-0082836-g002: Linear regression of cod condition .The adjusted Pearson's coefficient , with value .

Mentions: Temperature is an essential environmental factor that does not only directly affect fish population dynamics, i.e. survival, growth, feeding rates, and movements, but also acts as a useful proxy for other physical and oceanographic processes regulating their prey and predator distribution, as well as metabolic kinetics in aquatic food webs [62], [63]. The CIL is characterized by strong inter-annual changes in temperature (cf. Figure 9 in File SIM) that have been shown to affect the early life stages of cod in the NGSL [64], [65]. In addition, the low water temperatures of the NGSL observed during the mid-1990 s have been hypothesised to negatively affect cod reproduction, growth, condition, and natural mortality [21], [46], [66]. The mean annual temperature of the GSL was therefore used as an indicator of environmental conditions in the NGSL. Following an approach proposed by [20], we established a linear relationship between cod condition in year and the GSL temperature at 250 m deep in year so as to link the environment to cod biology in our model projections (Figure 2). Water temperatures were derived from a large dataset of temperature profiles collected in the GSL and expressed as anomalies, i.e. deviations from their long-term mean calculated for the 1971–2000 reference period [67] (Figure 10 in File SIM). The fit was made using an usual least square method. Predicting the NGSL environmental conditions over the next decades remains however challenging regarding the peculiarities of the Gulf topography and water circulation, and the complex intricate effects that climate change could have on sea ice extent, light attenuation, freshwater runoff, and nutrient supply which all drive ecosystem productivity [68]–[70]. To cover a large range of environmental conditions in the Gulf of St. Lawrence, three temperature regimes based on the historical time series of the CIL during 1984–2009 [60] were simulated to represent mean and extreme scenarios, as usual in sensitivity analysis [71]. The CIL temperature anomaly averaged over 1984–2009 was considered as the base case scenario while the temperature averaged over the 5 hottest and coldest years observed in the time series were considered for the warming and cooling scenarios, respectively.


Forecasting the major influences of predation and environment on cod recovery in the northern Gulf of St. Lawrence.

Bousquet N, Chassot E, Duplisea DE, Hammill MO - PLoS ONE (2014)

Linear regression of cod condition .The adjusted Pearson's coefficient , with value .
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3921123&req=5

pone-0082836-g002: Linear regression of cod condition .The adjusted Pearson's coefficient , with value .
Mentions: Temperature is an essential environmental factor that does not only directly affect fish population dynamics, i.e. survival, growth, feeding rates, and movements, but also acts as a useful proxy for other physical and oceanographic processes regulating their prey and predator distribution, as well as metabolic kinetics in aquatic food webs [62], [63]. The CIL is characterized by strong inter-annual changes in temperature (cf. Figure 9 in File SIM) that have been shown to affect the early life stages of cod in the NGSL [64], [65]. In addition, the low water temperatures of the NGSL observed during the mid-1990 s have been hypothesised to negatively affect cod reproduction, growth, condition, and natural mortality [21], [46], [66]. The mean annual temperature of the GSL was therefore used as an indicator of environmental conditions in the NGSL. Following an approach proposed by [20], we established a linear relationship between cod condition in year and the GSL temperature at 250 m deep in year so as to link the environment to cod biology in our model projections (Figure 2). Water temperatures were derived from a large dataset of temperature profiles collected in the GSL and expressed as anomalies, i.e. deviations from their long-term mean calculated for the 1971–2000 reference period [67] (Figure 10 in File SIM). The fit was made using an usual least square method. Predicting the NGSL environmental conditions over the next decades remains however challenging regarding the peculiarities of the Gulf topography and water circulation, and the complex intricate effects that climate change could have on sea ice extent, light attenuation, freshwater runoff, and nutrient supply which all drive ecosystem productivity [68]–[70]. To cover a large range of environmental conditions in the Gulf of St. Lawrence, three temperature regimes based on the historical time series of the CIL during 1984–2009 [60] were simulated to represent mean and extreme scenarios, as usual in sensitivity analysis [71]. The CIL temperature anomaly averaged over 1984–2009 was considered as the base case scenario while the temperature averaged over the 5 hottest and coldest years observed in the time series were considered for the warming and cooling scenarios, respectively.

Bottom Line: This sensitivity study shows that water temperature is key in the rebuilding of the NGSL cod stock.Model projections suggest that maintaining the current management practice under cooler water temperatures is likely to maintain the species in an endangered status.In the medium-term, a management strategy that reduces catch could be favoured over a complete moratorium so as to minimize socio-economic impacts on the industry.

View Article: PubMed Central - PubMed

Affiliation: Institut de Mathématiques de Toulouse, UMR 5219 CNRS, Université Paul Sabatier, Toulouse, France.

ABSTRACT
The northern Gulf of St. Lawrence (NGSL) stock of Atlantic cod (Gadus morhua), historically the second largest cod population in the Western Atlantic, has known a severe collapse during the early 1990 s and is currently considered as endangered by the Committee on the Status of Endangered Wildlife in Canada. As for many fish populations over the world which are currently being heavily exploited or overfished, urgent management actions in the form of recovery plans are needed for restoring this stock to sustainable levels. Stochastic projections based on a statistical population model incorporating predation were conducted over a period of 30 years (2010-2040) to assess the expected outcomes of alternative fishing strategies on the stock recovery under different scenarios of harp seal (Pagophilus groenlandicus) abundance and environmental conditions. This sensitivity study shows that water temperature is key in the rebuilding of the NGSL cod stock. Model projections suggest that maintaining the current management practice under cooler water temperatures is likely to maintain the species in an endangered status. Under current or warmer conditions in the Gulf of St. Lawrence, partial recovery might only be achieved by significant reductions in both fishing and predation pressure. In the medium-term, a management strategy that reduces catch could be favoured over a complete moratorium so as to minimize socio-economic impacts on the industry.

Show MeSH
Related in: MedlinePlus