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A limit reference point (LRP) is defined as a level of biomass to be avoided with high probability, which should be selected to protect fish stocks from 'serious harm'. We present an evidence-based approach for diagnosing serious harm and apply it to the selection of LRPs for five Pacific herring (Clupeapallasii) stocks in British Columbia (BC). Natural mortality (M) is estimated to be time varying and has increased more than it declined over the past three decades, which presents a challenge for estimation of equilibrium reference points based on maximum sustainable yield. We present a semi-empirical approach for developing LRPs, which examines surplus production in relation to spawning biomass to determine whether there is evidence for low productivity, low biomass (LP-LB) states consistent with serious harm. Three stocks showed evidence of persistent LP-LB states that resulted in periods of fishery closures. Based on these results, an LRP of 30% of unfished spawning biomass (0.3[B.sub.0]) was recommended and adopted for management of all five major stocks of BC Pacific herring. Key words: Pacific herring, Clupea pallasii, limit reference point, biological reference points, surplus production, fisheries management, precautionary approach, 1. Introduction In 2015, the Department of Fisheries and Oceans Canada (DFO) initiated a review of the management approach for Pacific herring (Clupea pallasii) fisheries in British Columbia (BC) (DFO [...]

Data-limited methods (DLMs) in stock assessment may provide potential critical information for data-limited stock management. However, the sensitivity of those methods to life-history parameters is largely unknown, resulting in extra uncertainty and consequent risks. In the present study, we designed six parallel workflows (WFs) to incorporate classic and state-of-the-art methods of estimating life-history parameters and examined their influences on the assessment of small yellow croaker (Larimichthys polyactis) in Haizhou Bay, China. The sensitivity was evaluated with three objectives: (i) the evaluation of stock status with the spawning potential ratio following different assumptions; (ii) the length-based harvest control rules derived from three management procedures; and (iii) the management performance of these harvest control rules with simulation of management strategy evaluation. The results showed considerable sensitivity regarding the three objectives to the estimations with different WFs, indicating the previous practice of credulously accepting empirical values and indiscriminately selecting references are inadvisable. We also identified the most appropriate WFs used for different purposes with limited data, aiming to provide more reliable inputs for effective fisheries management. Les methodes de traitement de donnees limitees (MDL) utilisees dans revaluation de stocks peuvent fournir de l'information potentiellement cle pour la gestion de stocks pour lesquels les donnees sont limitees. La sensibilite de ces methodes aux parametres du cycle biologique est generalement inconnue, ce qui se traduit par une incertitude accrue et les risques qui en decoulent. Nous avons concu six flux de travail (FT) paralleles pour incorporer des methodes classiques et de pointe d'estimation de parametres du cycle biologique et examine leur influence sur l'evaluation de la courbine jaune (Larimichthys polyactis) dans la baie de Haizhou (Chine). L'evaluation de la sensibilite avait trois objectifs, soit (i) revaluation de l'etat du stock par l'estimation du rapport du potentiel de frai pour differentes hypotheses; (ii) les regles de controle des prises basees sur la longueur decoulant de trois procedures de gestion; et (iii) le rendement de la gestion de ces regles de controle des prisesavec simulation de l'evaluation de strategies de gestion. Les resultats revelent une sensibilite considerable concernant ces trois objectifs aux estimations avec differents flux de travail, qui indique que la pratique passee de tenir pour acquises les valeurs empiriques et de choisir des references sans discrimination n'est pas recommandable. Nous avons egalement cerne les flux de travail les mieux adaptes pour differentes fins en presence de donnees limitees, dans le but de fournir des donnees d'entree plus fiables pour une gestion efficace des peches. [Traduit par la Redaction], Introduction Over 90% of the fish stocks in the world are managed without formal stock assessment, including the majority of fisheries in the developing countries (Costello et al. 2012). The [...]

Salmonid juvenile stocking programs are often poorly monitored due to the lack of identification between stocked and wild fish. In this study, a hierarchical Bayesian model is developed to take advantage of spatiotemporal variations of stocking and wild recruitment for estimating these two components despite the absence of identification data. It is first tested by means of simulated data and then applied to the 37 year abundance data set of the Atlantic salmon (Salmo salar) population of the Allier catchment (France). Despite the absence of identification data, juvenile densities could be estimated and split into wild and stocked components. We found that the stocked juveniles contributed significantly to the total juvenile production, while the wild reproduction continued to provide an important contribution. This approach is encouraging and promising from a management advice perspective. It is flexible enough to accommodate for case study specificities and shows that long-term monitoring abundances can be useful to assess the impact of stocking programs even in the absence of direct means of identifying stocked versus wild fish. Le suivi de programmes de repeuplement de populations de salmonides est souvent deficiente en raison notamment de l'absence de marquage permettant de distinguer les individus sauvages des individus issus du repeuplement. Nous utilisons la modelisation hierarchique bayesienne pour tirer parti des variations spatiotemporelles du repeuplement et du recrutement naturel et ainsi estimer ces deux composantes en l'absence de donnees d'identification. Le modele est d'abord teste avec des donnees simulees, puis applique a un ensemble de donnees d'abondance sur 37 ans pour la population de saumon atlantique (Salmo salar) du bassin de l'Allier (France). Malgre l'absence de donnees d'identification, les densites de juveniles ont pu etre estimees et divisees en des composantes sauvage et issue du repeuplement. Nous avons constate une contribution significative des juveniles issus du repeuplement a la population totale de juveniles, la reproduction des individus sauvages continuant aussi d'en constituer une importante proportion. Cette approche est encourageante et prometteuse du point de vue de la gestion. Elle est en outre suffisamment souple pour permettre l'integration d'aspects propres a des etudes de cas et demontre que les suivis abondance a long terme peuvent etre utile pour evaluer l'incidence de programmes de repeuplement en l'absence de moyens directs pour distinguer les poissons issus du repeuplement des poissons sauvages. [Traduit par la Redaction], Introduction Over the past century, many exploited fish populations have declined significantly due to environmental changes, overexploitation, and human activities (Hilborn and Walters 1992; Blankenship and Leber 1995; Frank and [...]

Stock-recruitment (S-R) relationships are the centrepiece of fisheries management aimed at achieving maximum sustainable yield. Here we consider the possibility that the density dependence evident in S-R relations is controlled by feeding interactions alone. We simulate a food-web model with dynamic representations of intra- and inter-specific size structure and a linear relation between food intake and hatchling production of adults. Population sizes of individual stocks are modified by imposing additional mortality. The predominant functional forms and the steepness of resulting S-R relationships agree well with observations. We conclude that recruitment is plausibly regulated by feeding interactions alone. Les relations stock-recrutement (S-R) constituent l'element central de la gestion des peches axee sur l'atteinte du rendement maximum durable. Nous examinons la possibilite que la dependance a la densite evidente dans les relations S-R soit controlee uniquement par des interactions associees a l'alimentation. Nous simulons un modele de reseau trophique integrant des representations dynamiques de la structure de tailles intraspecifique et interspecifique et une relation lineaire entre l'apport de nourriture et la production d'alevins vesicules des adultes. Les tailles des populations de differents stocks sont modifiees en imposant une mortalite supplementaire. Les formes fonctionnelles predominantes et les parametres de pente des relations S-R obtenues concordent bien avec les observations. Nous concluons qu'il est plausible que le recrutement soit controle uniquement par des interactions associees a l'alimentation. [Traduit par la Redaction], Introduction Empirical stock-recruitment (S-R) relationships exhibit clear evidence of density dependence. Since the early works of Ricker (1954), Schaefer (1954), Beverton and Holt (1957), and others who characterized and interpreted [...]

Estimation of fish stock size distributions from survey data requires knowledge about gear selectivity. However, selectivity models rest on assumptions that seldom are analyzed. Departures from these can lead to misinterpretations and biased management recommendations. Here, we use survey data on great Arctic char (Salvelinus umbla) to analyze how correcting for entanglement of fish and nonisometric growth might improve estimates of selectivity curves, and subsequently estimates of size distribution and age-specific mortality. Initial selectivity curves, using the entire data set, were wide and asymmetric, with poor model fits. Removing potentially nonmeshed fish had the greatest positive effect on model fit, resulting in much narrower and less asymmetric selection curves, while attempting to take nonisometric growth into account, by using girth rather than length, improved model fit but not as much. Using simulations we show that correcting for both entanglement and size selectivity produces accurate estimates of mortality rates, while correcting for size selectivity only does not. Our study demonstrates an approach that increases the accuracy of estimates of fish size distributions and mortality rates from survey data. L'estimation de la distribution des tailles au sein de stocks de poissons a partir de donnees tirees devaluations necessite une connaissance de la selectivite des engins. Les modeles de selectivite reposent toutefois sur des hypotheses qui sont rarement analysees. Des ecarts par rapport a ces dernieres peuvent se traduire par des interpretations erronees et des recommandations de gestion biaisees. Nous avons utilise des donnees devaluations relatives a l'omble chevalier (Salvelinus umbla) pour analyser comment des correctifs visant a tenir compte de l'enchevetrement de poissons et de la croissance non isometrique pourraient ameliorer les estimations de courbes de selectivite et, ainsi, les estimations de la distribution des tailles et de la mortalite selon l'age. Les courbes de selectivite initiales obtenues en utilisant l'integralite des donnees etaient larges et asymetriques, et l'ajustement du modele n'etait pas bon. Le retrait des poissons potentiellement non enchevetres a eu le plus grand effet positif sur l'ajustement du modele aux donnees, produisant des courbes de selection beaucoup moins larges et asymetriques, alors que la prise en compte de la croissance non isometrique en utilisant le tour du corps plutot que la longueur a ameliore l'ajustement du modele, mais dans une moindre mesure. Nous demontrons, a l'aide de simulations, que le fait de corriger pour l'enchevetrement et la selectivite des tailles produit des estimations exactes du taux de mortalite, contrairement au fait de corriger seulement pour la selectivite des tailles. L'etude demontre qu'une telle approche accroit l'exactitude des estimations de la distribution des tailles et du taux de mortalite des poissons basees sur des donnees devaluations. [Traduit par la Redaction], Introduction In freshwater systems several standardized methods exist to estimate community species composition, as well as abundance, biomass, and size distribution of fish stocks, including electrofishing, hydroacoustics, and gillnet surveys. [...]

Brown trout (Salmo trutta) is a salmonid species with a high socio-economic value related with recreational fishing. Because of that, stocking programs have been developed in many populations, although they have focused on resident populations. To explore which factors promote migratory behaviour when implementing stocking actions, 28 brown trout artificial crosses were carried out in a noncommercial hatchery, and the returning success of their offspring was further evaluated. Return rate was examined according to male phenotype (anadromous versus resident), mean egg size, parents' similarity at major histocompatibility complex (MHC) class II β-gene, and stocking procedure. At the end of the experiment, 35 of the captured returning adults (9.4%) belonged to 14 of those crosses. Return success shows a significant effect (p = 0.0016) by parental MHC similarities, stocking procedure, and male phenotype. Our results indicate that planting fertilized eggs in nursery areas of the river, together with the selection of anadromous males as brood stock and mate pairs with higher similarity at the MHC locus, can be an appropriate option to increase the migratory part of trout populations. In addition, nursery areas can allow an important decrease in the cost per stocked individual, being 32 times less expensive than the cost per hatchery-reared individual. La truite de mer (Salmo trutta) est une espece de salmonides a grande valeur socioeconomique associee a la peche sportive. Pour cette raison, des programmes d'empoissonnement ont ete developpes pour de nombreuses populations, bien que ces programmes aient mis l'accent sur les populations residentes. Afin d'examiner les facteurs qui favorisent le comportement migrateur dans un contexte d'empoissonnement, 28 croisements artificiels de truites de mer ont ete effectues dans une aleviniere non commerciale, et le succes de retour de leur progeniture a ete evalue. Le taux de retour a ete examine en ce qui concerne le phenotype male (anadromes par rapport a residents), la taille moyenne des ceufs, la similitude des parents au gene a de classe II du complexe majeur d'histocompatibilite (CMH) et la procedure d'empoissonnement. A la fin de l'experience, 35 des adultes remontes ayant ete captures (9,4 %) provenaient de 14 de ces croisements. La similitude des CMH parentaux, la procedure d'empoissonnement et le phenotype male ont eu une incidence significative (p = 0.0016) sur le succes du retour. Nos resultats indiquent que l'ensemencement de zones d'alevinage du cours d'eau avec des ceufs fecondes jumele a la selection d'un stock geniteur de males anadromes et de couples presentant une grande similitude au locus du CMH peuvent s'averer une option efficace pour accroitre la portion migratrice des populations de truites. En outre, comme le recours aux zones d'alevinage de cours d'eau entrame un cout par individu 32 fois plus faible que celui de l'elevage en aleviniere, cette approche peut permettre une diminution importante du cout par individu empoissonne. [Traduit par la Redaction], Introduction Conservation of native populations is an important challenge for managers (Waples and Hendry 2008). For instance, many salmonid populations have declined dramatically during the last century because of overexploitation [...]

Abstract--Most assessments of fish stocks use some measure of the reproductive potential of a population, such as spawning biomass. However, the correlation between spawning biomass and reproductive potential is not [...]

Cobia (Rachycentron canadum) is a migratory, euryhaline benthopelagic species distributed worldwide in tropic, subtropic, and warm temperate waters, except in the eastern Pacific (Briggs, 1960). In the United States, cobia [...]

The rule of thumb that fishing mortality to achieve maximum sustainable yield ([F.sub.MSY]) equals natural mortality (M) has been both criticised and supported by theoretical arguments. However, the relationship has been rarely investigated using empirical data. We carried out a meta-analysis on 245 fish species worldwide and linked three types of reference points ([F.sub.BRP]: [F.sub.MSY], [F.sub.proxy], and [F.sup.0.5r]) to M and other life history parameters (LHP). We used Bayesian hierarchical errors-invariables models to investigate the relationships and included the effect of taxonomic class and order. We compared various models and found that natural mortality is the most important LHP affecting [F.sub.BRP]. Other covariates, such as von Bertalanffy growth coefficient, asymptotic length, maximum age, and habitat types, add little to the relationship, partially because of correlation and large measurement and process errors. The best model results in [F.sub.MSY] = 0.87 M (standard deviation (SD) = 0.05) for teleosts and [F.sub.MSY] = 0.41 M (SD = 0.09) for chondrichthyans. [F.sub.proxy] based on per-recruit analysis is about 15% smaller than [F.sub.MSY]. Results could be used to estimate [F.sub.BRP] from LHP in data-poor situations. Des arguments theoriques ont ete utilises tant pour critiquer que pour appuyer la regle generalement evoquee voulant que la mortalite du poisson necessaire a l'atteinte du rendement equilibre maximum ([F.sub.MSY]) soit egale a la mortalite naturelle (Mi). Cependant, cette relation a rarement ete examinee a la lumiere de donnees empiriques. Nous avons effectue une meta-analyse de 245 especes de poissons a l'echelle planetaire et relie trois types de points de reference ([F.sub.BRP] : [F.sub.MSY], [F.sub.proxy], et Fx5r)a M ainsi qu'ad'autres parametres du cycle biologique (LHP). Nous avons utilise des modeles hierarchiques bayesiens d' erreurs sur les variables pour etudier ces relations et y avons integre l' effet de la classe et de l'ordre taxinomiques. Nous avons compare divers modeles et determine que la mortalite naturelle est le LHP ayant la plus grande incidence sur les [F.sub.BRP]. D'autres covariables, telles que le coefficient de croissance de von Bertalanffy, la longueur asymptotique, l'age maximum et les types d'habitat, n'ont que peu d'incidence sur la relation, en raison notamment de la correlation et d'importantes erreurs de mesure et de traitement. Le meilleur modele donne une valeur de [F.sub.MSY] = 0,87 M (ecart-type (SD) = 0,05) pour les teleosteens et de [F.sub.MSY] = 0,41 M (SD = 0,09) pour les chondrichthyens. La valeur de [F.sub.proxy] basee sur l'analyse du rendement par recrue est d'environ 15 % inferieure a [F.sub.MSY]. Les resultats pourraient etre utilises pour l'estimation de [F.sub.BRP] a partir de LHP dans les cas ou peu de donnees sont disponibles. [Traduit par la Redaction], Introduction Biological reference points (BRPs) are used both as targets and limits in stock status assessment, harvest control rules, and tactical fisheries management. Generally, BRPs may be based either on [...]

The relationship between stock size and recruitment is an essential element in the understanding of the productivity of a population. However, predicting the number of recruits produced by a population has proven to be a difficult challenge. This may in part be a result of poor estimation of reproductive potential (RP). We determined if including increased information on reproductive biology in indices of RP results in better predictions of recruitment. We investigated some of the conditions that lead to better (or worse) recruitment prediction when more biologically complex indices of RP are used. Data from four populations in the Northwest Atlantic were examined: southern Grand Bank (NAFO Division 3NO) cod (Gadus morhua), Flemish Cap (NAFO Division 3M) cod, Newfoundland (NAFO Division 3LNO) American plaice (Hippoglossoides platessoides), and Greenland halibut (Reinhardtius hippoglossoides) (NAFO Subarea 2 + Division 3KLMNO). Stock-recruit models paired with complex indices of RP gave a better estimate of recruitment in slightly more than half of the tests conducted. When there were larger trends in the reproductive biology (maturity at age, sex ratio and egg production), more complex indices of RP were more likely to provide a better estimate of recruitment. La relation entre la taille d'un stock et le recrutement est un element essentiel pour la comprehension de la productivite d'une population. Cependant, la prediction du nombre de recrues produites par la population s'est averee etre un defi difficile. Ce peut en partie etre le resultat d'une mauvaise estimation du potentiel reproductif (RP). Nous avons determine si l'addition d'information supplementaire sur la biologie de la reproduction dans les indices de RP produit de meilleures predictions du recrutement. Nous avons etudie certaines des conditions qui entrainent une meilleure (ou moins bonne) prediction du recrutement lorsque des indices plus biologiquement complexes de RP sont utilises. Nous avons examine les donnees provenant de quatre populations du nord-ouest de l'Atlantique, les morues (Gadus morhua) du Grand Banc sud (NAFO Division 3NO), les morues de Flemish Cap (NAFO Division 3M), les plies canadiennes (Hippoglossoides platessoides) de Terre-Neuve (NAFO Division 3LNO) et les fletans du Groenland (Reinhardtius hippoglossoides) (NAFO sous-region 2 + Division 3KLMNO). Les modeles stocks-recrues apparies a des indices complexes de PR donnent une meilleure estimation du recrutement dans un peu plus de la moitie des tests. Lorsqu'il y a des tendances plus marquees dans la biologie de la reproduction (maturite en fonction de l'age, proportion des sexes, production des oeufs), les indices plus complexes de PR sont plus susceptibles de fournir une meilleure estimation du recrutement. [Traduit par la Redaction], Introduction Predicting the number of recruits produced by a population has proven to be a difficult challenge in fisheries science. Yet the relationship between stock size and recruitment is an [...]

The dynamics of the northern and western Sea of Japan sailfin sandfish (Arctoscopus japonicus) stocks (NSJ and WSJ, respectively) varied simultaneously until the mid-1970s but differently thereafter. To identify the mechanisms underlying these dynamics, we evaluated the impact of environment and harvesting on NSJ by developing a recruitment model and simulating NSJ dynamics. The model was constructed based on egg production, density effect, and water temperatures in winter and spring, which correlated significantly and positively with the estimated surface mixed-layer depth. Winter water temperatures and egg production were variables common to the two stocks. Our results suggest that simultaneous dynamics resulted from similarities in variations in winter water temperatures for each stock and the difference in dynamics resulted from NSJ depletion caused by overfishing. We suggest management strategies to prevent NSJ depletion caused by unfavorable environmental conditions and overfishing, as well as to allow improved biomass recovery while taking advantage of favorable environmental conditions, and avoid further exploitation of previously depleted NSJ. Les dynamiques des stocks du toroumoque japonais (Arctoscopus japonicus) du nord et de l'ouest de la mer du Japon (respectivement NSJ et WSJ) ont varie de concert jusqu'au milieu des anneees 1970 pour diffeerer par la suite. Afin d'identifier les mecanismes sous-jacents a ces dynamiques, nous avons eevalue l'impact de l'environnement et de la recolte sur le stock NSJ en mettant au point un modele de recrutement et en simulant la dynamique du stock NSJ. Le modele est construit sur la base de la production d'oeufs, de l'effet de la densite, et des temperatures de l'eau en hiver et au printemps, qui sont en correlation significative et positive avec la profondeur estimee de la couche de melange de surface. Les temperatures de l'eau en hiver et la production d'oeufs sont des variables qui s'appliquent aux deux stocks. Nos resultats indiquent que la dynamique simultaneeresulte de ressemblances dans les variations dans les temperatures d'hiver pour les deux stocks et que les differences de dynamique s'expliquent par un declin du stock NSJ a cause de la surpeche. Nous proposons des strategies de gestion pour empecher le declin du stock NSJ cause; par les conditions environnementales deefavorables et la surpeche, ainsi que pour permettre une meilleure recuperation de la biomasse en profitant des conditions environnementales favorables et pour eviter une exploitation supplementaire du stock NSJ deja reduit. [Traduit par la Redaction], Introduction Understanding fish stock dynamics is important for the prevention of stock depletion and for rebuilding depleted stocks. Several fisheries stocks have already been severely depleted (Pauly et al. 2002), [...]

ABSTRACT The effect of stocking density on growth performance of Thai abalone, Haliotis asinina, Linnaeus 1758, was investigated over an 8-mo period (July 2008 to March 2009). A semiclosed recirculating [...]

Abstract--Assessing the vulnerability of stocks to fishing practices in U.S. federal waters was recently highlighted by the National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration, as an important [...]

We present a mathematical model of artificial pelagic multisite fisheries. The model is a stock--effort dynamical model of a fishery subdivided into artificial fishing sites such as fish-aggregating devices (FADs) or artificial habitats (AHs). The objective of the work is to investigate the effects of the number of sites on the global activity of the fishery. We consider a linear chain of fishing sites in which fish are harvested by fishing vessels and a free stock that is unattached to the sites and not exploited. Fish movements between the sites and the free stock, as well as vessel displacements between the sites, are assumed to take place at a faster time scale than the variation of the stock and the change of the fleet size. We take advantage of these two time scales to derive a reduced model governing the dynamics of the total fish stock and the total fishing effort. We show that there exists an optimal number of fishing sites that maximizes the total catch at equilibrium. We finally extend the model to the situation in which both fish attached to the sites and fish in the free stock are exploited. Resume: Nous presentons un modele mathematique d'une peche pelagique artificielle a sites multiples. Le modele est un modele dynamique stock--effort subdivise en sites artificiels de peche, tels que des dispositifs de concentration des poissons (FAD) ou des habitats artificiels (AH). L'objectif de notre travail est de determiner les effets du nombre de sites sur l'activite totale de la peche. Nous examinons une chaine lineaire de sites de peche dans laquelle les poissons sont recoltes par des navires de peche et un stock libre qui n'est pas relie aux sites et qui n'est pas exploite. Nous assumons que les deplacements des poissons entre les sites et le stock libre, de meme que les deplacements des navires entre les sites, se produisent sur une echelle temporelle plus courte que la variation du stock et le changement de taille de la flotte. Ces deux echelles temporelles nous permettent de deriver une modele reduit de controle de la dynamique du stock total de poissons et de l'effort total de la peche. Nous demontrons qu'il existe un nombre optimal de sites de peche qui maximise la capture totale a l'equilibre. Nous elargissons enfin le modele a la situation dans laquelle il y a exploitation tant des poissons associe s aux sites que des poissons du stock libre. [Traduit par la Redaction], Introduction Artificial pelagic multisite fisheries, e.g., fisheries on fish aggregating devices (FADs) or on artificial habitats (AHs), pose a certain number of specific questions due, in particular, to the spatial [...]

An important management challenge is to maintain productive populations of Pacific salmon (Oncorhynchus spp.), despite highly variable environments and our weak understanding of future climatic conditions and mechanisms that link them to salmon. This understanding could be improved by including environmental covariates in salmon population models and applying advanced 'meta-analyses' to large data sets to better estimate underlying functional relationships. However, the performance of such models needs to be determined in the context of an overall system. We therefore simulated a 15-population salmon fishery system and compared the performance (in terms of catch and an index of conservation concern) of 10 forecasting and stock assessment models, ranging from simple to complex, by stochastically simulating components of a salmon fishery using a 'closed-loop simulation' (or 'management strategy evaluation') under a variety of plausible future climatic scenarios. We found that complex models perform better in some situations. However, their incremental benefits are small and are swamped by the large variability in outcomes of management actions caused by 'outcome uncertainty', which reflects noncompliance of fishing vessels with regulations as well as variation in catchability. Reduction of this outcome uncertainty should therefore be a top priority, as should evaluations of more complex stock assessment models before adopting them. Resume: C'est un defi important de gestion que de maintenir des populations tres productives de saumons du Pacifique (Oncorhynchus spp.) malgre les environnements tres variables et une faible comprehension des conditions climatiques futures et des mecanismes qui les relient aux saumons. Cette comprehension pourrait etre amelioree si on ajoutait des covariables environnementales dans les modeles demographiques de saumons et si on faisait des [much less than] meta-analyses [much greater than] des grands ensembles de donnees afin de mieux estimer les relations fonctionnelles sous-jacentes. Cependant, la performance de tels modeles doit etre determinee dans le contexte d'un systeme global. Nous avons donc simule un systeme de peche de saumons comprenant 15 populations et compare la performance (en ce qui a trait a la capture et a un indice de preoccupation pour la conservation) de 10 modeles de prevision et d'evaluation des stocks, allant de simples a complexes. Nous simulons de facon stochastique les composantes d'une peche a saumons a l'aide d'une [much less than] simulation en boucle fermee [much greater than] (ou d'une [much less than] evaluation des strategies de gestion [much greater than]) dans une variete de scenarios climatiques plausibles dans le futur. Les modeles complexes fonctionnent mieux dans certaines circonstances. Cependant, leur benefice additionnel est petit et masque par l'importante variabilite des resultats des actions de gestion causee par [much less than] l'incertitude des resultats [much greater than] qui reflete le fait que les navires de peche ne se conforment pas aux reglementations et que la capturabilite est variable. On devrait donc donner une forte priorite a la reduction de cette [much less than] incertitude des resultats [much greater than]; il en va de meme des evaluations des modeles plus complexes d'estimation des stocks avant leur adoption. [Traduit par la Redaction], Introduction Scientists and fisheries managers who work on Pacific salmon (Oncorhynchus spp.) face major challenges. They seek to maintain abundant and productive populations in spite of large uncertainties in four [...]

Climate variability affects marine ecosystems. The mechanisms relating low-frequency environmental fluctuations (regime shifts) and their impacts on marine populations are not well established for most species, but there is an expectation that the accuracy of scientific advice provided to fisheries management would be improved if management strategies incorporated the effects of regime shifts on stocks. Management strategy evaluation is used to examine the impact of regime shifts in average recruitment on the performance of management strategies for the fishery for walleye pollock, Theragra chalcogramma, in the Gulf of Alaska. The current and four alternative management strategies are evaluated. The alternatives include management strategies with different definitions of the average recruitment used when calculating management reference points, e.g., a 25-year sliding-window method and a 'dynamic [B.sub.0]' method. The current management strategy, which ignores the possibility of future regime shifts, kept the spawning biomass higher relative to the target level than the other management strategies and had the lowest risk of fishing mortality exceeding the overfishing limit. The sliding-window management strategy achieved the highest catches and the lowest interannual variation in catch, although at the cost of a higher risk of the fishing mortality exceeding the overfishing limit. Resume: La variabilite du climat affecte les ecosystemes marins. Les mecanismes qui relient les fluctuations environnementales de basse frequence (changements de regime) et leurs impacts sur les populations marines ne sont pas bien etablis chez la plupart des especes; on s'attend, cependant, a ce qu'il ait une amelioration des recommandations scientifiques pour la gestion des peches si les strategies de gestion tenaient compte des effets des changements de regime sur les stocks. Nous utilisons l'evaluation des strategies de gestion pour examiner l'impact des changements de regime dans le recrutement moyen sur la performance des strategies de gestion dans les peches de goberges de l'Alaska, Theragra chalcogramma, dans le golfe de l'Alaska. Nous evaluons la strategie de gestion actuelle et quatre strategies de rechange. Parmi les strategies de gestion de rechange, il y a des definitions differentes du recrutement moyen utilisees dans le calcul des points de reference de gestion, par ex., une methode de fenetrage dynamique sur 25 ans et une methode [much less than] [B.sub.0] dynamique [much greater than]. La methode actuelle de gestion, qui ne tient pas compte des changements futurs de regime, maintient la biomasse des reproducteurs plus elevee par rapport au niveau cible que les autres strategies de gestion et presente le risque le moins eleve que la mortalite due a la peche depasse la limite de la surpeche. La strategie de gestion de fenetrage dynamique permet les captures les plus elevees et la variation interannuelle entre les captures la plus faible, cependant c'est au cout d'un risque plus grand que la mortalite due a la peche depasse la limite de la surpeche. [Traduit par la Redaction], Introduction Climate variability, as it impacts marine ecosystems, occurs on multiple spatial and temporal scales. For example, in the North Pacific, climate variability is interannual (El Nino-Southern Oscillation), decadal (Pacific [...]

Estimation of fish abundance from acoustic surveys requires the estimation of total acoustic backscatter of the target species in the sampled region. Although the arithmetic mean of acoustic backscatter is an unbiased estimator of the mean backscatter for regular or random sampling designs, under the presence of spatial structure, its use leads to a loss of information and the estimation of its variance is not trivial. Here, we tackle these shortcomings by building a spatial model of acoustic backscatter using spline-based generalized additive models (GAMs). GAMs were used to provide local and global estimates of acoustic backscatter, and their precision was calculated by statistical simulations of the models' parameters. For a series of surveys performed off the western and southern Iberian Peninsula, GAM estimates were unbiased and more precise than the arithmetic mean estimates. Simulations of the acoustic backscatter fields were combined with resampling of the trawls to provide confidence intervals for fish numbers and biomass. The relative standard errors of the estimates were within 13% and 46% (average 22%) for numbers and within 12% and 35% (average 19%) for biomass. Acoustic sampling error was the major contributor to the overall variance. Resume: Afin d'estimer l'abondance des poissons a partir des inventaires acoustiques, il est necessaire d'obtenir une estimation de la retrodiffusion acoustique totale de l'espece cible dans la region echantillonne. La moyenne arithmetique de la retrodiffusion acoustique est un estimateur sans distorsion de la retrodiffusion moyenne pour les plans d'echantillonnage reguliers ou aleatoires; cependant, en presence de structure spatiale, son utilisation mene a une perte d'information et l'estimation de la variance est difficile. Nous abordons ici ces lacunes en construisant un modele spatial de la retrodiffusion acoustique a l'aide de modeles additifs generalises (GAM) bases sur les splines. Les GAM ont servi a fournir des estimations locales et globales de la retrodiffusion acoustique et leur precision a ete calculee par des simulations statistiques des parametres du modele. Dans une serie d'inventaires realises au large de l'ouest et du sud de la peninsule iberique, les estimations par GAM ne montrent aucune distorsion et elles sont plus precises que les estimations arithmetiques moyennes. Les simulations des champs de retrodiffusion acoustique ont ete combinees a des re-echantillonnages des donnees de chalutage afin d'obtenir des intervalles de confiance pour la densite et la biomasse des poissons. Les erreurs types relatives des estimations varient de 13 a 46 % (en moyenne 22 %) pour la densite et de 12 a 35 % (en moyenne 19 %) pour la biomasse. L'erreur de l'echantillonnage acoustique est la source principale de la variance globale. [Traduit par la Redaction], Introduction Acoustic surveys are commonly used to estimate indices of abundance at age for many stocks of pelagic fish worldwide (Simmonds and MacLennan 2005). As in every estimation procedure, estimates [...]

Multispecies fish recruitment patterns within Chesapeake Bay were investigated in four fishery-independent survey data sets (one primary and three ancillary data sets) that together span the years 1968-2004. These independently conducted surveys record interannual recruitment variability for 15 ecologically and economically important fish species of the Northeast US Continental Shelf Large Marine Ecosystem. Principal component analyses revealed that the strongest multispecies recruitment pattern (first principal component) present in each data set describes a negative recruitment relationship between anadromous and coastal shelf-spawning species. Among the data sets, the first principal component accounted for 31%-42% of multispecies variance. Locally weighted regression modeling revealed that the decadal-scale variability accounted for 62% of the variance in the primary data set's first principal component's (annual) scores, whereas interannual variability accounted for only 38%. Despite strong differences in sampling methods, sampled habitats, and sampling locations, this pattern of antagonistic recruitment between Chesapeake Bay anadromous and shelf-spawning (CBASS) species was synchronously correlated among data sets at both decadal and interannual scales. The CBASS pattern has tended to persist in one mode for periods lasting longer than a decade and tends to reverse sign rather within only 2-3 years. A statistically significant regime shift occurred in 1992, when recruitment in anadromous fishes became favored at the expense of recruitment of shelf-spawning estuarine-dependant fishes. Nous avons etudie les patrons de recrutement multispecifiques des poisons de la baie de Chesapeake dans quatre ensembles de donnees d'inventaire independants des peches commerciales (un ensemble de donnees primaire et trois ensembles accessoires) qui conjointement couvrent les annees 1968-2004. Ces inventaires menes de facon independante recensent la variabilite du recrutement chez 15 especes de poisons d'importance ecologique et economique du grand ecosysteme marin de la plate-forme continentale du nord-est des E.-U. Les analyses en composantes principales indiquent que le patron le plus evident de recrutement multispecifique (premiere composante principale) present dans chaque ensemble de donnees decrit une relation negative de recrutement entre les poisons anadromes et ceux qui fraient sur la plateforme continentale. Dans ces ensembles de donnees, la premiere composante principale explique 31-42% de la variance multispecifique. Une modelisation loess de la premiere composante principale de l'ensemble de donnees primaire montre que la variabilite a l'echelle de la decennie explique 62 % de la variance des cotes (annuelles) de PC1, alors que la variabilite interannuelle explique le 38% qui reste. Malgre d'importantes differences dans les methodes d'echantillonnage, les habitats inventories et les sites echantillonnees, ce patron des poisons anadromes ou frayant sur la plate-forme de la baie de Chesapeake (CBASS) est correle en synchronie dans les ensembles de donnees, tant a l'echelle de la decennie qu'a l'echelle interannuelle. Le patron CBASS a eu tendance a persister dans un meme mode durant des periodes de plus dune decennie et il tend a changer de signe plutot sur une periode de 2-3 ans. Un changement statistiquement significatif de regime s'est produit en 1992, lorsque le recrutement des poisons anadromes a ete favorise au depends du recrutement des poisons qui fraient sur la plateforme et qui sont dependants des estuaires. [Traduit par la Redaction], Introduction Understanding mechanisms responsible for the high variability observed in annual fish recruitment is essential for the development and implementation of multispecies and ecosystem-based fisheries management. Potentially important causal mechanisms [...]

Multiple linear regressions (MLRs), generalized additive models (GAMs), and artificial neural networks (ANNs) were compared as methods to forecast recruitment of Gulf of Alaska walleye pollock (Theragra chalcogramma). Each model, based on a conceptual model, was applied to a 41-year time series of recruitment, spawner biomass, and environmental covariates. A subset of the available time series, an in-sample data set consisting of 35 of the 41 data points, was used to fit an environment-dependent recruitment model. Influential covariates were identified through statistical variable selection methods to build the best explanatory recruitment model. An out-of-sample set of six data points was retained for model validation. We tested each model's ability to forecast recruitment by applying them to an out-of-sample data set. For a more robust evaluation of forecast accuracy, models were tested with Monte Carlo resampling trials. The ANNs outperformed the other techniques during the model fitting process. For forecasting, the ANNs were not statistically different from MLRs or GAMS. The results indicated that more complex models tend to be more susceptible to an overparameterization problem. The procedures described in this study show promise for building and testing recruitment forecasting models for other fish species. Nous avons compare les regressions lineaires multiples (MLRs), les modeles additifs generalises (GAMS) et les modeles statistiques de reseaux de neurones artificiels (ANNs) comme methodes pour predire le recrutement de la goberge de (Alaska (Theragra chalcogramma) dans le golfe de (Alaska. Nous avons applique chaque modele, base sur un modele conceptual, a une serie chronologique de 41 annees de donnees sur le recrutement, la biomasse des reproducteurs et les covariables de l'environnement. Un sous-ensemble de la serie chronologique disponible, soft un ensemble de donnees provenant de fechantillon consistant en 35 des 41 points de donnees, a servi a ajuster un modele de recrutement dependent de fenvironnement. Des methodes statistiques de selection des variables ont permis d'identifier les covariables les plus influentes afro de batir le meilleur modele explicatif du recrutement. Un ensemble de six points de donnees hors de fechantillon a ete garde pour la validation des modeles. Nous avons teste la capacite de chaque modele a predire le recrutement en appliquant le modele a un ensemble de donnees hors de l'echantillon. Pour une evaluation plus robuste de la justesse de la prediction, nous avons teste les modeles avec des essais de reechantillonnage de Monte Carlo. Les ANNs surpassent les autres techniques durant le processus d'ajustement des modeles. Pour ce qui est de la prediction, les ANNs ne sont pas statistiquement differents des MLRs et des GAMS. Les resultats indiquent que les modeles plus complexes ont plus tendance a souffrir de problemes de surparametrisation. Les procedures que nous decrivons sont prometteuses pour l'elaboration et fajustement des modeles de prediction du recrutement chez d'autres especes de poisons. [Traduit par la Redaction], Introduction Society is challenged to steward the exploitation of marine resources effectively for the health of the planet. Forecasting recruitment is a commonly recognized, but elusive, goal for the sustainable [...]

As far back as 3 to 5 million years ago, a unique-looking fish with an abrupt, sharp-edged hump behind its head swam the Colorado River and its tributaries. Once widespread [...]

The landings of Atlantic cod (Gadus morhua) in the eastern Baltic Sea in the early decades of the 20th century were below 50 thousand tonnes and therefore lower than in recent years at very low stock size. These low landings have largely contributed to a perception that the stock size was also low before the 1950s. In this investigation, we demonstrate that cod spawning stock biomass in the years 1925-1944 fluctuated in a similar range as in the periods from the 1950s to the mid-1970s and from the late 1980s onwards and was in most of these years at least twice as high as at present. Fishing mortality before the 1940s was below 0.2, but reached moderate levels during the Second World War. The stock size before the war may be considered as a reference level of biomass at low fishing impact, providing important information for the management of fisheries and the Baltic ecosystem. Les debarquements de morues (Gadus morhua) de l'est de la Baltique des premieres decennies du 20e siecle etaient inferieurs a 50 mille tonnes et donc plus faibles que ceux des annees recentes caracterisees par une taille du stock tres reduite. Ces faibles debarquements ont en grande partie contribue a la perception que la taille du stock aussi etait basse avant les annees 1950. Dans notre travail, nous demontrons que la biomasse du stock reproducteur de la morue dans les annees 1925-1944 fluctuait dans la meme gamme de valeurs que durant les periodes des annees 1950 au milieu des annees 1970 et des annees qui ont suivi la fin des annees 1980; le stock etait pour la plupart de ces annees au moins le double du stock actuel. La mortalite due a la peche avant les annees 1940 etait inferieure a 0,2, mais elle a atteint des valeurs moyennes au cours de la Seconde Guerre mondiale. La taille du stock avant la guerre peut ainsi representer une valeur de biomasse de reference lorsque l'impact de la peche etait faible, ce qui fournit des donnees importantes pour la gestion des peches et de l'ecosysteme de la Baltique. [Traduit par la Redaction], Introduction Most of the regular fish stock assessments in the North Atlantic Ocean cover only the recent three--four decades, and the available time series of stock developments begin after the [...]

Abstract--For many fish stocks, resource management cannot be based on stock assessment because data are insufficient--a situation that requires alternative approaches to management. One possible approach is to manage data-limited [...]

Reestablishment rates of two native fish species, lake trout and smallmouth bass, are compared in stocking experiments at lakes in Ontario, Canada's Killarney Park. Lake trout were found to recover at significantly slower rates than smallmouth bass; implications for cold-water and warm-water fish species management are discussed.

Study of chemical properties of free amino acids in Hake during bulk storage, and while packing under combined atmospheric system is presented.

Better-managed fisheries could yield billions of extra dollars in profit and extract millions more tonnes of fish from the oceans. Many fish stocks are overexploited and poorly managed. Christopher Costello [...]

Oregon chub (Oregonichthys crameri) are small minnows endemic to the Willamette Valley of western Oregon. They were formerly common and distributed throughout the valley in off-channel habitat, such as beaver [...]

Showcasing most types of the Pacific Northwest's natural wonders, the Warm Springs Indian Reservation in Oregon encompasses alpine lakes, pristine rivers, deep canyons, and vistas of high desert and volcanic [...]