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.

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Harvest control rules (HCRs).They determine the total allowable catch (TAC) of the NGSL cod stock in year t+1 from the spawning stock biomass (SSB) in year t. B and B are the limit and recovery biological reference points, respectively.
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pone-0082836-g003: Harvest control rules (HCRs).They determine the total allowable catch (TAC) of the NGSL cod stock in year t+1 from the spawning stock biomass (SSB) in year t. B and B are the limit and recovery biological reference points, respectively.

Mentions: Three HCRs characterized by increasing levels of conservation were considered to represent alternative ways of managing the cod stock (Figure 3). Here, the HCR determines the total allowable catch (TAC) in year t+1 from the knowledge of spawning stock biomass (SSB) in year t. A status quo HCR was derived from the past values of SSB estimated from sequential population analysis and subsequent allocation of TACs [18]. A reduced catch HCR was also used for the projections, leading to lower TACs than the status quo HCR for a given level of SSB (Figure 3). Finally, an HCR based on a moratorium was used in the projections to simulate the closure of the cod fishery. In these scenarios, the TAC was set to 284 t, which corresponded to the mean annual catch observed during the 1994–1996 moratorium and due to bycatch in other fisheries than the cod fishery. Although the moratorium differs from the adaptive reduced catch approach, it results in quite similar levels of catch removals for low cod abundance, i.e. when spawning stock biomass 116,000 t (Figure 3).


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)

Harvest control rules (HCRs).They determine the total allowable catch (TAC) of the NGSL cod stock in year t+1 from the spawning stock biomass (SSB) in year t. B and B are the limit and recovery biological reference points, respectively.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0082836-g003: Harvest control rules (HCRs).They determine the total allowable catch (TAC) of the NGSL cod stock in year t+1 from the spawning stock biomass (SSB) in year t. B and B are the limit and recovery biological reference points, respectively.
Mentions: Three HCRs characterized by increasing levels of conservation were considered to represent alternative ways of managing the cod stock (Figure 3). Here, the HCR determines the total allowable catch (TAC) in year t+1 from the knowledge of spawning stock biomass (SSB) in year t. A status quo HCR was derived from the past values of SSB estimated from sequential population analysis and subsequent allocation of TACs [18]. A reduced catch HCR was also used for the projections, leading to lower TACs than the status quo HCR for a given level of SSB (Figure 3). Finally, an HCR based on a moratorium was used in the projections to simulate the closure of the cod fishery. In these scenarios, the TAC was set to 284 t, which corresponded to the mean annual catch observed during the 1994–1996 moratorium and due to bycatch in other fisheries than the cod fishery. Although the moratorium differs from the adaptive reduced catch approach, it results in quite similar levels of catch removals for low cod abundance, i.e. when spawning stock biomass 116,000 t (Figure 3).

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