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The Pacific cod (Gadus macrocephalus) fishery recently collapsed in the Gulf of Alaska after a series of marine heat-waves that began in 2014. To gauge the likelihood of population recovery following these extreme warming events, we investigate potential thermal stress on age-0 cohorts through a comprehensive analysis of juvenile cod abundance, condition, growth, and survival data collected from 15 years of beach seine surveys. Abundance was strongly negatively related to ocean temperature during the egg and larval phase (winter-spring), but age-0 cod were larger in the early summer following warm winter-spring temperatures. Body condition indices suggest that warm summers may improve energetic reserves prior to the first winter; however, there was no summer temperature effect on post-settlement growth or survival. Spatial differences in abundance, condition, or growth were not detected, and density-dependent effects were either weak or positive. While the positive effects of increased summer temperatures on juvenile condition may benefit overwintering survival, they cannot compensate for high pre-settlement mortality from warming winter-spring temperatures. We conclude the critical thermal bottleneck for juvenile abundance occurs pre-settlement. La peche a la morue du Pacifique (Gadus macrocephalus) s'est recemment effondree dans le golfe d'Alaska apres une serie de vagues de chaleur marines qui ont debute en 2014. Afin d'evaluer la probabilite d'un retablissement de la population apres ces episodes de rechauffement extreme, nous examinons le stress thermique potentiel sur des cohortes de moins de 1 an par une analyse exhaustive de donnees sur l'abondance, l'embonpoint, la croissance et la survie de morues juveniles obtenues de 15 annees de leves a la seine de rivage. L'abondance presente une forte relation negative avec la temperature de l'ocean durant la phase des oeufs et des larves (hiver-printemps), mais les morues de moins de 1 an sont plus grandes au debut d'etes suivant des temperatures hivernales-printanieres elevees. Les indices d'embonpoint indiqueraient que des etes chauds pourraient ameliorer les reserves d'energie avant le premier hiver; aucun effet de la temperature estivale sur la croissance ou la survie apres l'etablissement n'est cependant releve. Aucune variation spatiale de l'abondance, de l'embonpoint ou de la croissance n'est detectee, et les effets dependants de la densite sont faibles ou positifs. Si les effets positifs de temperatures estivales plus elevees sur l'embonpoint des juveniles pourraient ameliorer la survie hiemale, ils ne peuvent pallier la mortalite elevee qui precede l'etablissement, causee par la hausse des temperatures hivernales-printanieres. Nous concluons que le goulot d'etranglement thermique critique pour l'abondance des morues juveniles se produit avant l'etablissement. [Traduit par la Redaction], Introduction The recent collapse of the Pacific cod (Gadus macrocephalus) stock in the Gulf of Alaska has been directly linked to warming ocean temperatures in 2014-2016 (Barbeaux et al. 2020b) [...]

In subarctic Newfoundland, age-0 Atlantic cod (Gadus morhua) settle into coastal habitats in several summerautumn pulses, resulting in broad length-frequency distributions before winter. Low winter temperatures and potential decreases in food availability pose challenges for young-of-year fish. To examine how size variation affects overwintering success under contrasting food scenarios, we conducted 114-day laboratory feeding trials at ambient overwinter sea temperatures, using demersal age-0 cod collected from Newman Sound, Newfoundland. We reared two size classes of juvenile cod under four daily ration levels (starvation, low, medium, high). We used Fulton's K condition factor to interpret effects of food availability and fish size on survival over winter. We showed that small amounts of consumed food (80% until Day 74. Therefore, we expect higher survival of earlier settlers and increased size-selective mortality in age-0 cod during either unproductive or protracted winters, when food abundance is often low. Dans les regions subarctiques de Terre-Neuve, des morues (Gadus morhua) de moins d'un an s'etablissent dans des habitats cotiers en plusieurs vagues durant l'ete et l'automne, ce qui produit des distributions etalees de la frequence des longueurs avant l'hiver. Les basses temperatures hivernales et des diminutions potentielles de la disponibilite de nourriture presentent des defis pour les jeunes de l'annee. Afin d'examiner l'incidence des variations de la taille sur la survie hiemale pour differents scenarios de disponibilite de nourriture, nous avons mene des essais d'alimentation en laboratoire sur 114 jours aux temperatures de la mer hivernales ambiantes, en utilisant des morues demersales de moins d'un an prelevees dans la baie de Newman, a Terre-Neuve. Nous avons eleve des morues juveniles de deux classes de taille en leur donnant l'une ou l'autre de quatre rations quotidiennes differentes (privation, faible, moyenne et grande). Nous avons utilise le facteur d'embonpoint de Fulton, K, pour interpreter les effets de la disponibilite de nourriture et de la taille des poissons sur la survie hiemale. Nous avons demontre que de petites quantites de nourriture consommee (, Introduction Juvenile fish experience high natural mortality in their first year of life (Sogard 1997; Kristiansen et al. 2000). Despite multiple studies of mortality in juvenile Atlantic cod (Gadus morhua) [...]

Warming temperatures in the Gulf of Alaska have been linked to recruitment failure in Pacific cod (Gadus macrocephalus), but the mechanisms and timing of mortality events for juveniles are unclear. To date, limited research has focused on overwintering success, and the knowledge of juvenile ecology and physiology is based entirely on summer observations. Here, we investigate the changes in body condition, diet composition, and tissue-specific fatty acid (FA) storage for age-0 Pacific cod in Kodiak, Alaska, from February to December during 2018 and 2020. We observed protracted nearshore residency from June to December. Cod body condition (K dry) and predicted weight at length were lowest in October, November, and December. Although not different interannually, diet composition varied seasonally, which corresponded to an increase in cod length. A range of condition metrics (HSIwet, FA concentration in liver tissue, and the % of whole body FAs stored in the liver) began to increase in September. Cod prioritized growth during the summer, while in the autumn and pre-winter they allocated more energy into lipid storage. We conclude that seasonal changes in tissue-specific FA storage and pre-winter fish conditions are important factors to consider for understanding overwintering potential of juvenile Pacific cod. [ABSTRACT FROM AUTHOR]

Pacific cod (Gadus macrocephalus) stocks in the Gulf of Alaska experienced steep, unexpected declines following an unprecedented 3-year marine heatwave (i.e., 'warm blob') from 2014 to 2016. We contend that stock reproductive potential was reduced during this period, evidenced by a combination of new laboratory data demonstrating narrow thermal hatch success (3-6 [degrees]C), mechanistic-based models of spawning habitat, and correlations with prerecruit time series. With the exception of single-year El Nino events (1998, 2003), the recent 3-year heatwave (2014-2016) and return to similar conditions in 2019 were potentially the most negative impacts on spawning habitat for Pacific cod in the available time series (1994-2019). Continued warming will likely reduce the duration and spatial extent of Pacific cod spawning in the Gulf of Alaska. Les stocks de morue du Pacifique (Gadus macrocephalus) dans le golfe d'Alaska ont connu des declins abrupts et inattendus a la suite d'une vague de chaleur marine (ou <>) sans precedent d'une duree de 3 ans, de 2014 a 2016. Nous soutenons que le potentiel de reproduction des stocks a diminue durant cette periode, comme en fait foi une combinaison de nouvelles donnees de laboratoire qui demontrent une etroite fourchette de temperatures associee au succes d'eclosion (de 3 a 6 [degrees]C), des modeles mecanistes des habitats de frai et des correlations avec des series chronologiques pre-recrutement. A l'exception d'episodes El Nino d'une seule annee (1998, 2003), la vague de chaleur recente de trois ans (2014-2016) et le retour a des conditions semblables en 2019 constituent possiblement les impacts les plus importants sur les habitats de frai pour la morue du Pacifique dans les series chronologiques disponibles (1994-2019). La poursuite du rechauffement reduira vraisemblablenient la duree et l'etendue spatiale du frai des monies du Pacifique dans le golfe d'Alaska. [Traduit par la Redaction], Introduction From late 2013 to 2016, the Gulf of Alaska (GOA) experienced 3-4 [degrees]C above average sea surface temperature anomalies (relative to 1980-2010) associated with a reduction in winter heat [...]

Coastal seine surveys contain some of the only direct measures of age-0 abundance for Atlantic cod (Gadus morhua) and Pacific cod (Gadus macrocephalus), yet their utility in forecasting future year-class strength has not been evaluated among regions. We analyzed coastal time series from the Gulf of Alaska, Newfoundland, and Norway to test the hypothesis that recruitment signals are stronger when assessed under thermal conditions that provide high juvenile growth potential. Weaker recruitment signals were associated with low growth potential from cold winters (Newfoundland) and recent warmer summers (Norway). We conclude that temperature-dependent growth strongly influences the utility of coastal surveys in recruitment forecasting among regions. Temporal changes in growth potential (e.g., via climate change) will likely affect recruitment signals by way of changes in juvenile mortality or spatial shifts to more favorable thermal habitats. Si les releves cotiers a la senne constituent un des rares moyens d'obtenir des mesures directes de l'abondance de la classe d'age 0 pour la morue franche (Gadus morhua) et la morue du Pacifique (Gadus macrocephalus), leur utilite pour predire la force future des classes d'age n'a pas ete evaluee entre differentes regions. Nous avons analyse des series chronologiques cotieres pour le golfe de l'Alaska, Terre-Neuve et la Norvege afin de verifier l'hypothese selon laquelle les signaux de recrutement sont plus forts quand ils sont evalues pour des conditions thermiques qui assurent aux juveniles un potentiel de croissance eleve. Des signaux de recrutement plus faibles etaient associes a un faible potentiel de croissance decoulant d'hivers froids (Terre-Neuve) et d'etes plus chauds recents (Norvege). Nous en concluons que la croissance dependante de la temperature a une forte incidence sur l'utilite des releves cotiers pour predire le recrutement entre regions. Des variations temporelles du potentiel de croissance (p. ex., decoulant de changements climatiques) auront vraisemblablement une incidence sur les signaux de recrutement, par l'entremise de modifications de la mortalite des juveniles ou de deplacements dans l'espace vers des niches thermiques plus favorables. [Traduit par la Redaction], Introduction Marine teleost fishes of the Family Gadidae comprise some the largest and most valuable wild fisheries in the world (e.g., Atlantic cod, Gadus morhua; walleye pollock, Gadus chalcogrammus) and [...]

Abstract--Northern rock sole (Lepidopsetta polyxystra) is a commercially important flatfish in Alaska and was recently classified as a distinct species from southern rock sole (L. bilineata). Taxonomic and vital rate [...]

The match-mismatch hypothesis (MMH) predicts that marine fish larvae will have their highest rate of growth and survival when they overlap with their prey. However, Pacific cod (Gadus macrocephalus) and other gadids continue to thrive in the Bering Sea despite delayed prey production resulting from warming and loss of sea ice. In this study, we examined how temperature mediates growth and survival of Pacific cod larvae under varying match-mismatch conditions. Cod larvae were reared at two temperatures (3°C and 8°C) and exposed to one of five different food treatments over a 6week period: (i) high food (HF) (match); (ii) low food (LF); (iii) HF then LF (HF-LF); and (IV) LF then HF (LF-HF) (2-4 mismatch); and (v) no food (NF) (complete mismatch). Results showed that cold environments allow Pacific cod larvae to bridge gaps in prey availability (i.e., timing and magnitude), but negatively impact survival over longer periods. Under warmer conditions, mismatches in prey significantly impacted growth and survival. However, both yolk reserves and compensatory growth mechanisms reduced the severity of mismatches occurring in the first 3 weeks of development. Our results demonstrate a clear need to incorporate the direct effects of temperature on fish larvae in food limitation models. L'hypothese de l'appariement-meisappariement (MMH, match-mismatch hypothesis) predit que les larves de poissons marins possedent une croissance et une survie maximales lorsqu'il y un chevauchement entre elles et leurs proies. Cependant, la morue du Pacifique (Gadus macrocephalus) et d'autres gadides continuent de prosperer dans la mer de Beering malgre la production retardeee de proies causee par le rechauffement et la perte de glace de mer. Nous examinons dans notre etude comment la temperature controle la croissance et la survie de la morue du Pacifique sous diverses conditions d'appariement-mesappariement. Nous avons eleve des larves de morue a deux temperatures (3°C et 8°C) et les avons exposees a l'un de cinq traitements alimentaires durant une periode de 6 semaines: (i) nourriture abondante (HF) (appariement), (ii) nourriture restreinte (LF), (iii) HF puis LF (HF-LF), (iv) LF puis HF (LF-HF) (2-4 mesappariements) et (v) absence de nourriture (NF) (meesappariement complet). Nos resultats montrent que les environnements froids permettent aux larves de morues du Pacifique de surmonter des interruptions dans la disponibilite des proies (c'est-a-dire le moment et l'intensite de la penurie); mais cela affecte negativement la survie sur des peeriodes plus longues. Dans des conditions plus chaudes, les mesappariements des proies affectent significativement la croissance et la survie. Cependant, les reserves de vitellus et les mecanismes compensatoires de la croissance reduisent tous deux la seveerite; des mesappariements qui se produisent durant les trois premieres semaines du developpement. Nos resultats demontrent clairement la necessite d'incorporer les effets directs de la temperature sur les larves de poissons dans les modeles de restriction de nourriture. [Traduit par la Redaction], Introduction Climate-driven impacts on ocean environments are changing the seasonal distribution and timing of zooplankton production worldwide (Richardson 2008). Marine fish larvae, which depend on zooplankton for food, are highly [...]

Abstract--Pacific cod (Gadus macrocephalus) is an important component of fisheries and food webs in the North Pacific Ocean and Bering Sea. However, vital rates of early life stages of this [...]

Abstract: The success of marine protected areas (MPAs) as fisheries management tools in tropical latitudes has generated interest in their applicability and potential elsewhere. Here we suggest that dispersal and [...]