Decline and Recovery of Atlantic Cod (Gadus morhua) Stocks throughout the North Atlantic

Lilly, George R.; Wieland, Kai; Rothschild, Brian J.; Sundby, Svein; Drinkwater, Ken; Brander, Keith; Ottersen, Geir; Carscadden, James E.; Stenson, Garry B.; Chouinard, Ghislain A.; Swain, Douglas P.; Daan, N.; Enberg, Katja; Hammill, Michael O.; Rosing‐Asvid, Aqqalu; Svedäng, Henrik; Vázquez, Antonio

doi:10.4027/rgsfcc.2008.03

Cited by 46 publications

(41 citation statements)

References 76 publications

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“…Undoubtedly these factors are related. The much improved condition of older fish in May-June in particular supports predictions first made in the early 1990s that environmental factors played an important role in the suppression of productivity in this stock and would delay rebuilding until conditions improved (deYoung and Rose 1993), a view consistent with considerable research over the past two decades (Rice 2006;Rothschild 2007;Greene and Pershing 2007;Lilly et al 2008;Hilborn and Litzinger 2009). Late winter to spring is the time of poorest condition in cod and when condition-related mortality is expected to be highest (Dutil and Lambert 2000;.…”

Section: Discussionsupporting

confidence: 81%

Northern cod comeback

Rose

Rowe

2015

Can. J. Fish. Aquat. Sci.

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Abstract:The great "northern" cod (Gadus morhua) stock, formerly among the world's largest and the icon for depletion and supposed nonrecovery of marine fishes, is making a major comeback after nearly two decades of attrition and fishery moratorium. Using acoustic-trawl surveys of the main prespawning and spawning components of the stock, we show that biomass has increased from tens of thousands of tonnes to >200 thousand tonnes within the last decade. The increase was signalled by massive schooling behaviour in late winter first observed in 2008 in the southern range of the stock (Bonavista Corridor) after an absence for 15 years, perhaps spurred by immigration. Increases in size composition and fish condition and apparent declines in mortality followed, leading to growth rates approaching 30% per annum. In the spring of 2015, large increases in cod abundance and size composition were observed for the first time since the moratorium in the more northerly spawning groups of this stock complex. The cod rebound has paralleled increases in the abundance of capelin (Mallotus villosus), whose abundance declined rapidly in the cold early 1990s but has recently increased during a period of warm ocean temperatures. With continued growth in the capelin stock and frugal management (low fishing mortality), this stock could rebuild, perhaps within less than a decade, to historical levels of sustainable yield. More generally, if this stock can recover, the potential exists for recovery of many other depleted stocks worldwide.Résumé : Le grand stock de morues (Gadus morhua) du Nord, qui figurait parmi les plus importants du monde et constitue l'exemple type de l'effondrement et du non-rétablissement présumé de poissons marins, fait un grand retour après presque deux décennies d'attrition et de moratoire sur la pêche. À partir de relevés acoustiques et au chalut des principaux composants pré-reproducteurs et reproducteurs du stock, nous démontrons que la biomasse a augmenté de quelques dizaines de milliers de tonnes à >200 000 tonnes durant la dernière décennie. Cette augmentation a été signalée par le comportement de rassemblement massif en bancs à la fin de l'hiver, d'abord observé en 2008 dans la partie sud de l'aire de répartition du stock (corridor de Bonavista) après une absence de 15 ans, qui a peut-être été favorisé par l'immigration. Des augmentations de la taille et de l'embonpoint des poissons et des diminutions apparentes de la mortalité ont suivi, menant à des taux de croissance annuels approchant les 30 %. Au printemps de 2015, de fortes augmentations de l'abondance et de la taille des morues ont été observées pour la première fois depuis le moratoire dans les groupes reproducteurs plus septentrionaux de ce complexe de stocks. Ce rebond de la morue a accompagné des augmentations de l'abondance du capelan (Mallotus villosus), qui avait diminué rapidement durant la période froide du début des années 1990, mais qui a récemment augmenté pendant une période de températures océaniques plus chaudes. La croissance contin...

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Section: Discussionsupporting

confidence: 81%

Northern cod comeback

Rose

Rowe

2015

Can. J. Fish. Aquat. Sci.

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“…The mechanisms through which fishing affects the dynamics of northern cod have been studied extensively (Hutchings & Myers 1994, Hutchings 1996, Myers et al 1996, Myers et al 1997, Rose 2004, Shelton et al 2006, Lilly et al 2008, Hilborn & Litzinger 2009). Our study reinforces the notion that fisheries harvest was an important factor in the collapse of Atlantic cod off Newfoundland during the early 1990s.…”

Section: Fisheries Harvest As a Drivermentioning

confidence: 99%

The role of harp seals, fisheries and food availability in driving the dynamics of northern cod

Buren¹,

Koen‐Alonso²,

Stenson³

2014

Mar. Ecol. Prog. Ser.

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The Atlantic cod Gadus morhua population off Newfoundland collapsed in the early 1990s due to over-exploitation, and despite marked reduction in fishing effort the stock remains depressed. Harp seal Pagophilus groenlandicus predation has been repeatedly proposed as an explanation for this lack of recovery, but other hypotheses include reduced prey availability and/or food quality (i.e. lack of capelin Mallotus villosus), as well as fisheries catches and environmental effects. Using a bioenergetics−allometric model, we gauged the relative contributions of these drivers on the lack of recovery and dynamics of the northern cod stock. Biomass dynamics were best explained by a combination of fisheries removals and capelin availability, whereas seal consumption was found not to be an important driver of the northern cod stock. Prey availability was linked to reduced somatic condition during the 1990s and 2000s. We discuss evidence that suggests that cod may be experiencing depensatory dynamics, but not related to a 'predator pit effect'. Our study suggests that trophic control is bottom-up, and that a depressed capelin stock could be a serious impediment for cod rebuilding.

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“…It is, therefore, possible that the time period during which two indispensable conditions hold jointly in the three studied populations-that we have adequate quantitative observations and that fisheries-induced selection was strong-has been too short (up to 20 years, and less for analyses including stock biomass) to cause detectable evolutionary change. Moreover, since the exploitation of the studied cod populations had already intensified in the 1950s (Lilly et al 2008), it is possible that adaptations to high mortality rates occurred before the time period covered in this study. Yet, we argue that adaptation to fishing is unlikely to have halted just a few decades after the industrialization of the Newfoundland cod fishery.…”

Section: Interpretation Of Temporal Trends In Gonad Weightmentioning

confidence: 99%

Reproductive investment in Atlantic cod populations off Newfoundland: Contrasting trends between males and females

Baulier

Morgan

Lilly

et al. 2017

FACETS

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Life history theory predicts selection for higher reproductive investment in response to increased mortality among mature individuals. We tested this prediction over the period from 1978 to 2013 for three populations of Atlantic cod (Gadus morhua) off Newfoundland. These populations were heavily fished for a long period. We considered changes in standardized gonad weight as a proxy for changes in gonadal investment. We accounted for the allometry between gonad and body weight, individual body condition, water temperature, and potential spatial and density-dependent effects. Males display significant temporal trends in gonadal investment in all populations; in agreement with theoretical predictions, these trends show increased gonadal investments during the earlier part of the time series when mortality was high, with the trends leveling off or reversing after the later imposition of fishing moratoria. In contrast, females display patterns that are less consistent and expected; significant trends are detected only when accounting for density-dependent effects, with females in two populations unexpectedly showing a long-term decline in gonadal investment. Our results support the hypothesis that fisheries-induced evolution has occurred in gonadal investment in males, but not in females, and suggest that gonadal investment is more important for male reproductive success than expected in this lekking species.

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Decline and Recovery of Atlantic Cod (Gadus morhua) Stocks throughout the North Atlantic

Cited by 46 publications

References 76 publications

Northern cod comeback

Northern cod comeback

The role of harp seals, fisheries and food availability in driving the dynamics of northern cod

Reproductive investment in Atlantic cod populations off Newfoundland: Contrasting trends between males and females

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