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Catch curves are widely used to estimate total mortality for exploited marine populations. The usual population dynamics model assumes constant recruitment across years and constant total mortality. We extend this to include annual recruitment and annual total mortality. Recruitment is treated as an uncorrelated random effect, while total mortality is modelled by a random walk. Data requirements are minimal as only proportions-at-age and total catches are needed. We obtain the effective sample size for aggregated proportion-at-age data based on fitting Dirichlet-multinomial distributions to the raw sampling data. Parameter estimation is carried out by approximate likelihood. We use simulations to study parameter estimability and estimation bias of four model versions, including models treating mortality as fixed effects and misspecified models. All model versions were, in general, estimable, though for certain parameter values or replicate runs they were not. Relative estimation bias of final year total mortalities and depletion rates were lower for the proposed random effects model compared with the fixed effects version for total mortality. The model is demonstrated for the case of blue ling (Molva dypterygia) to the west of the British Isles for the period 1988 to 2011. Les courbes des captures sont largement utilisees pour estimer la mortalite totale des populations marines exploitees. Le modele de dynamique de population habituel suppose un recrutement et une mortalite totale constants au cours des annees. Nous developpons ce modele pour y inclure un recrutement et une mortalite totale variables entre annees. Le recrutement est traite comme un effet aleatoire non correle tandis que la mortalite totale est traitee comme une marche aleatoire. Les besoins en donnees sont minimaux car seules les proprotions aux ages et les captures totales sont necessaires. La taille effective de l'echantillon des donnees agregees de proportion aux ages est obtenue en ajustant une distribution Dirichlet-multinomiale aux donnees brutes d'echantillonnage. L'estimation des parametres est realisees par vraisemblance. Des simulations ont ete utilisees pour etudier l'estimabilite des parametres et les biais d'estimation de quatre versions du modele, dont des modeles traitant la mortalite comme des effets fixes et des modeles avec hypotheses fausses. Toutes les versions du modele etaient en general estimables sauf pour certaines valeurs de parametres ou certaines realisations. Les biais relatif de l'estimation de la mortalite totale de la derniere annee et du taux de reduction de la population etaient plus faibles pour le modele a effet aleatoire propose que pour les versions a effets fixes pour la mortalite totale. Une application du modele a la lingue bleue (Molva dypterygia) de l'Ouest des Iles Britanniques pour la periode de 1988 a 2011 est presentee., Introduction Fisheries stock assessments make use of a range of methods to obtain estimates of the status of exploited stocks that match the diversity of information available. Catch curves and [...]

tossm (Testing of Spatial Structure Methods) is a package for testing the performance of genetic analytical methods in a management context. In thetossm package, any method developed to detect population genetic structure can be combined with a mechanism for creating management units (MUs) based on the genetic analysis. The resulting Boundary-Setting Algorithm (BSA) dictates harvest boundaries with a genetic basis. These BSAs can be evaluated with respect to how well the MUs they define meet management objectives. [ABSTRACT FROM AUTHOR]

The article focuses on a study which analyzed and predicted faunal distributions from video and multi-beam sonar data using Markov models. The Markov model used related data on the deep seabed environment acquired from video transects, to other properties remotely sensed by multibeam acoustics. Spatial dependence in one direction only was allowed by the Markov model, which is along the video transects.

The results of a double-marking experiment using natural markings and microsatellite genetic markers to identify humpback whales (Megaptera novaeangliae) confirm that natural markings are a reliable means of identifying individuals on a large scale. Of 1410 instances of double tagging, there were 414 resightings. No false positive and 14 false negative errors were identified. The rate of error increased with decreasing photographic quality; no errors were observed among photographs of the highest quality rating, whereas an error rate of 0.125 was identified in sightings for which only part of the area used for identification was visible. There was also a weaker relationship between error rate and the distinctiveness of markings, which may result from non-independence in coding for image quality and distinctiveness. A correction is developed for the Petersen two-sample abundance estimator to account for false negative errors in identification, and a parametric bootstrap procedure for estimation of variance is also developed. In application to abundance estimates from the North Atlantic, the correction reduces the bias in estimates made using poorer quality photographs to a negligible level while maintaining comparable precision. [ABSTRACT FROM AUTHOR]

tossm (Testing of Spatial Structure Methods) is a package for testing the performance of genetic analytical methods in a management context. In the tossm package, any method developed to detect population genetic structure can be combined with a mechanism for creating management units (MUs) based on the genetic analysis. The resulting Boundary-Setting Algorithm (BSA) dictates harvest boundaries with a genetic basis. These BSAs can be evaluated with respect to how well the MUs they define meet management objectives., (Published 2009. This article is a US Government work and is in the public domain in the USA.)