Limits...
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.

Show MeSH

Related in: MedlinePlus

Probabilities-at-year for the SSB to exceed the limit of recruitment overfishing .Alternative fishing management strategies, levels of seal reduction, and environmental conditions are considered. (a) Current environmental conditions (CIL = 0.25°C) for 30% (a–1) and 50% (a–2) seal reduction. (b) Warming environmental conditions (CIL = 0.75°C) for 30% (b–2) and 50% (b–3) seal reduction. Plain and dashed lines indicate the effects of reduced catch and cod fishery moratorium, respectively. Mean and 95% confidence intervals of the probabilities are displayed.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3921123&req=5

pone-0082836-g007: Probabilities-at-year for the SSB to exceed the limit of recruitment overfishing .Alternative fishing management strategies, levels of seal reduction, and environmental conditions are considered. (a) Current environmental conditions (CIL = 0.25°C) for 30% (a–1) and 50% (a–2) seal reduction. (b) Warming environmental conditions (CIL = 0.75°C) for 30% (b–2) and 50% (b–3) seal reduction. Plain and dashed lines indicate the effects of reduced catch and cod fishery moratorium, respectively. Mean and 95% confidence intervals of the probabilities are displayed.

Mentions: The time span required for cod recovery was strongly dependent on water temperature conditions. Applying more conservative management approaches and further reducing the seal population favoured more rapid recovery (Figure 7). For all scenarios leading to partial stock recovery, the reduced catch management rule and moratorium did not yield any difference in recovery times before 2020 as shown by the mutual coverage of the confidence intervals around the probabilities of recovery (Figure 7). After 2020, a statistically-significant separation appeared between the confidence intervals. The moratorium approach reduced the time for recovery, while the reopening of fishing through the reduced catch approach would have the effect of reducing the SSB during the following 10 years.


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)

Probabilities-at-year for the SSB to exceed the limit of recruitment overfishing .Alternative fishing management strategies, levels of seal reduction, and environmental conditions are considered. (a) Current environmental conditions (CIL = 0.25°C) for 30% (a–1) and 50% (a–2) seal reduction. (b) Warming environmental conditions (CIL = 0.75°C) for 30% (b–2) and 50% (b–3) seal reduction. Plain and dashed lines indicate the effects of reduced catch and cod fishery moratorium, respectively. Mean and 95% confidence intervals of the probabilities are displayed.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0082836-g007: Probabilities-at-year for the SSB to exceed the limit of recruitment overfishing .Alternative fishing management strategies, levels of seal reduction, and environmental conditions are considered. (a) Current environmental conditions (CIL = 0.25°C) for 30% (a–1) and 50% (a–2) seal reduction. (b) Warming environmental conditions (CIL = 0.75°C) for 30% (b–2) and 50% (b–3) seal reduction. Plain and dashed lines indicate the effects of reduced catch and cod fishery moratorium, respectively. Mean and 95% confidence intervals of the probabilities are displayed.
Mentions: The time span required for cod recovery was strongly dependent on water temperature conditions. Applying more conservative management approaches and further reducing the seal population favoured more rapid recovery (Figure 7). For all scenarios leading to partial stock recovery, the reduced catch management rule and moratorium did not yield any difference in recovery times before 2020 as shown by the mutual coverage of the confidence intervals around the probabilities of recovery (Figure 7). After 2020, a statistically-significant separation appeared between the confidence intervals. The moratorium approach reduced the time for recovery, while the reopening of fishing through the reduced catch approach would have the effect of reducing the SSB during the following 10 years.

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