Northern cod comeback

Abstract

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...

Effects of closing bottom trawling on fisheries, biodiversity, and fishing communities in a boreal marine ecosystem: the Hawke Box off Labrador, Canada

“…Nonetheless, an impact of the Hawke Box on cod should not be dismissed out of hand (Lester et al 2009). The abundance of cod increased postclosure in both surveys, but the fall survey showed increased abundance postclosure but declines in biomass, which is consistent with an increase in younger juveniles (DFO 2015), while the increase in the spring survey represented an increase in the spawning population (Rose and Rowe 2015). The Hawke Box closure could have enhanced the survival of juvenile cod spawned in that region (Anderson and Rose 2001) that would be expected to increase their range as they matured (Anderson and Dalley 1997) and perhaps home back to their natal grounds (Robichaud and Rose 2001).…”

“…In effect, all measures are made against what is essentially a moving background that is independent of closures. In terms of the biological community under study here, it was expected that cod and perhaps other demersal fishes would increase, and crustaceans decline, over the period under study Rose and Rowe 2015), independent of the closure, largely as a result of changing production (e.g., Pastoors et al 2000). Both changes were observed, and against that background we measured significant differences in response between the closed and open areas.…”

“…A secondary objective of the Hawke Box closure was to enhance the survival of juvenile and spawning cod known to utilize this area (Anderson and Rose 2001;Rose 2007). Spring surveys in 2015 in the Hawke Channel region recorded a dramatic increase in cod biomass over the past decade (Rose and Rowe 2015). This biomass increase was slightly greater inside than outside the Hawke Box, but the sparse data and wide-ranging migratory nature of cod in the region (Rose 1993) impose difficulties in determining the impact of the closed area on this increase (Breen et al 2015) and may be insufficient to have impact at the population level (Laurel and Bradbury 2006;Le Quesne and Codling 2009).…”

Towards linking environmental law and science

“…This feedback might not reach an open policy window, but it may contribute to policy when the window subsequently opens. For example, scientific studies on the likelihood of Atlantic cod stock recovery (Neubauer et al 2013;Rose and Rowe 2015) may influence future decisions regarding re-opening the cod commercial fishery, which has been closed since the 1990s.…”

Reply to Le Pape et al.: Management is key to preventing marine extinctions

“…Management interventions have been key to stabilizing many overharvested fish populations, including northern cod (9) and Atlantic bluefin tuna (10), mentioned by Le Pape et al (3). Whereas high fecundity might have eventually saved these populations from complete extinction, there is danger in assuming that certain species are unkillable.…”