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The abundance of many Chinook salmon (Oncorhynchus tshawytscha) stocks has declined despite reductions in harvest. We used state-space models parameterized with data from 57 Chinook salmon indicator stocks, ranging from coastal Oregon to southeast Alaska, to quantify long-term (since 1972 release year) changes in juvenile marine survival rate and mean age-at-maturity, as well as identify stock groupings with coherent dynamics. We found that juvenile marine distribution-rather than freshwater life history, run timing, or adult marine distribution--was the best predictor of trends in both survival and age. Only subyearling stocks that enter the Strait of Georgia showed evidence of transitioning to a low juvenile survival period, other groupings exhibited low and stable or cyclical patterns in survival. Conversely, declines in mean age-at- maturity were widespread and do not appear to have stabilized, suggesting that future declines in Chinook salmon population productivity may be influenced by earlier maturation or increased adult mortality, rather than further reductions in juvenile marine survival. Key words: age-at-maturity, dynamic factor analysis, life history, population productivity, population demography, spatial distribution, survival L'abondance de nombreux stocks de saumons chinooks (Oncorhynchus tshawytscha) a diminue malgre des reductions des prises. Nous utilisons des modeles d'espaces d'etats parametres avec des donnees sur 57 stocks indicateurs de saumons chinooks allant du littoral de l'Oregon au sud-est de l'Alaska pour quantifier les changements a long terme (depuis l'annee de lacher 1972) des taux de survie en mer de juveniles et de l'age moyen a la maturite, ainsi que pour cerner des groupes de stocks ayant une dynamique coherente. Nous constatons que la repartition en mer des juveniles, plutot que le cycle biologique en eau douce, le moment de la montaison ou la repartition en mer des adultes, est le meilleur predicteur des tendances tant de la survie que de l'age. Seuls les stocks d'individus de moins d'un an qui entrent dans le detroit de Georgia presentent des signes d'une transition vers une periode de faible survie des juveniles, les autres groupes presentant des motifs de survie faibles et stables ou cycliques. En revanche, des baisses de l'age moyen a la maturite sont repandues et ne semblent pas se stabiliser, ce qui indiquerait que les baisses futures de la productivite de populations de saumons chinooks pourraient etre influencees par une maturation plus precoce ou une mortalite accrue des adultes, plutot que par d'autres baisses de la survie en mer de juveniles. [Traduit par la Redaction] Mots-cles : age a la maturite, analyse factorielle dynamique, cycle biologique, productivite des populations, demographie des populations, repartition spatiale, survie, Introduction The future of many North American Chinook salmon (Oncorhynchus tshawytscha) stocks appears to be increasingly uncertain due to factors including poor marine survival (Ruff et al. 2017; Welch et [...]

The most important nesting site for the green turtle, Chelonia mydas, in the Atlantic basin is Costa Rica's Tortuguero National Park (TNP). An important portion of this population nests on Playa Norte, an adjacent beach located to the north of TNP. Using 10 years (2006-2015) of mark-recapture data, we estimated demographic parameters for green turtles nesting at Playa Norte. During the 10-year study period, 1573 nesting encounters were recorded, representing 1101 distinct individuals. Open-population models estimated an abundance of 6004 (95% CI 5037-6970), representing the contingent of adult females that nested on Playa Norte at least once during the study period. This estimate includes females that died did not use Playa Norte as nesting site or became post-reproductive after the first nesting encounter as well as nesting and non-nesting adult females in a given year. This open-population abundance estimate and related demographic rates are also assumed to be robust against inter-nesting occurrences between Playa Norte and TNP, and between Playa Norte and other unmonitored and minor beaches. The mean annual survival rate was 0.85 (95% CI 0.76-0.91) and the realized annual population growth from 2006 to 2015 was 1.0179 (95% CI 0.7984-1.2978), indicating a positive trend characterized by an average 1.79% annual increase. The results presented here concur with results from studies of nesting females at TNP and highlight the importance of Playa Norte as a nesting ground for Atlantic green turtles. In addition, our study demonstrated that reliable demographic information can be derived from nesting sites at the edge of a main nesting area if proper survey designs and analytical methods are used., Introduction Globally, green turtles (Chelonia mydas, Linnaeus 1758) are classified as endangered by the International Union for the Conservation of Nature (Seminoff 2004). The species is circumtropically distributed (Bowen et [...]

No net loss of productive capacity (PC) of fish habitat has been the central concept guiding Canadian fish habitat management policy since 1986. The purpose of this paper is to describe the concept of PC, to review the history and application of the fish habitat management policy in Canada, and to provide a critical review of the range of potential approaches to estimating PC. The approaches were grouped by their central focus: habitat, individual, population, and community-ecosystem. A set of case studies is used to illustrate the use of some approaches drawn from freshwater and marine contexts. Ten components to assessing no net loss of PC were developed and used in the review of approaches for evaluating potential limitations. The review also highlighted the likely future direction of method development, with increasing emphasis on dynamic models integrating population responses to habitat supply characteristics. More work needs to be done to turn research-based metrics of PC into practical operational management assessment tools and to better quantify the link between habitat structure and function and fisheries productivity. The evolving approaches to measure PC reinforce the ties that fish habitat management has to the emerging practices in ecosystem-based management. La prevention de la perte nette de la capacite de production de l'habitat des poissons constitue le concept central qui regit la politique canadienne de gestion des habitats de poissons depuis 1986. L'objectif de notre travail est de decrire le concept de la capacite de production, de recapituler l'histoire et l'application de la gestion des habitats de poissons au Canada et presenter une revue critique de la gamme des approches potentielles pour estimer la capacite de production. Ces approches ont ete regroupees en fonction de leur cible principale, soit l'habitat, l'individu, la population et la communaute et l'ecosysteme. Nous presentons une serie d'etudes de cas pour illustrer l'utilisation de quelques approches tirees des contextes marins et d'eau douce. Nous mettons au point dix composantes pour evaluer la prevention de la perte nette de la capacite de production et les utilisons dans notre revue des approches pour evaluer les limitations potentielles. Notre revue souligne aussi la direction future vraisemblable de la mise au point de methodes, avec une emphase croissance sur les mode les dynamiques qui integrent les reactions des populations aux caracteristiques des apports des habitats. Il est necessaire de faire plus de travail pour traduire les metriques de la capacite de production basees sur la recherche en outils d'execution pratiques d'evaluation de la gestion et pour mieux mesurer le lien entre la structure et le fonctionnement des habitats et la productivite des peches. Les approches en cours pour mesurer la capacite de production renforcent les liens qui existent entre la gestion des habitats des poissons et les pratiques emergentes dans la gestion basee sur les ecosystemes. [Traduit par la Redaction], Introduction Canada's freshwater and marine fish species and fish habitats have a vital role in the economic prosperity of Canada, the biological diversity of Canada, and the lives of Canadians. [...]

Eleven Designatable Units (DUs) of Chinook Salmon (Oncorhynchus tshawytscha), within the Fraser River were assessed as Threatened or Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 2018, and are currently under consideration for addition to Schedule 1 of the Species at Risk Act (SARA). The first part of the Recovery Potential Assessment (RPA) (Elements 1-11) provided DU descriptions, status updates and an assessment of the threats and factors limiting recovery. This second half provides potential recovery targets, a discussion of mitigation measures, population projections and a recommendation on allowable harm. Survival and recovery targets for each DU were suggested based on Wild Salmon Policy (WSP) benchmarks, with additional requirements about observed percent change in spawners. A projection model was used to assess likely future trajectories and the chances of meeting these targets, however, results are only available for DU2 (LFRHarrison). Despite efforts to produce the required input parameters for the stream-type DUs, significant uncertainties and a considerable lack of data prevented quantitative assessment, and hence these DUs were assessed qualitatively. Results for DU2 (LFR-Harrison) indicate that reaching the survival target under recent conditions is about as likely as not likely (48% chance), while meeting the recovery goal is unlikely (16% chance). Risks imposed by climate change and continued anthropogenic development add additional uncertainty that was only described qualitatively. Based on the quantitative assessment for DU2 (LFR-Harrison) and the qualitative assessment for the remaining DUs, it is recommended that human-induced mortality and other sources of harm identified in the threats assessment should be significantly reduced and in some cases prevented to provide the best chance for these populations to recover. [ABSTRACT FROM AUTHOR]

The most important nesting site for the green turtle, Chelonia mydas, in the Atlantic basin is Costa Rica’s Tortuguero National Park (TNP). An important portion of this population nests on Playa Norte, an adjacent beach located to the north of TNP. Using 10 years (2006-2015) of mark-recapture data, we estimated demographic parameters for green turtles nesting at Playa Norte. During the 10-year study period, 1573 nesting encounters were recorded, representing 1101 distinct individuals. Open-population models estimated an abundance of 6004 (95% CI 5037-6970), representing the contingent of adult females that nested on Playa Norte at least once during the study period. This estimate includes females that died did not use Playa Norte as nesting site or became post-reproductive after the first nesting encounter as well as nesting and non-nesting adult females in a given year. This open-population abundance estimate and related demographic rates are also assumed to be robust against inter-nesting occurrences between Playa Norte and TNP, and between Playa Norte and other unmonitored and minor beaches. The mean annual survival rate was 0.85 (95% CI 0.76-0.91) and the realized annual population growth from 2006 to 2015 was 1.0179 (95% CI 0.7984-1.2978), indicating a positive trend characterized by an average 1.79% annual increase. The results presented here concur with results from studies of nesting females at TNP and highlight the importance of Playa Norte as a nesting ground for Atlantic green turtles. In addition, our study demonstrated that reliable demographic information can be derived from nesting sites at the edge of a main nesting area if proper survey designs and analytical methods are used. [ABSTRACT FROM AUTHOR]