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Robert Hackett,1 Richard Gearry,2,3 Christine Ho,4 Andrew McCombie,3 Megan Mackay,1 Karen Murdoch,5 Kirsten Rosser,2 Nideen Visesio,6 Stephen Inns1,3 1Department of Gastroenterology, Hutt Valley District Health Board, Lower Hutt, New Zealand; 2Department of Gastroenterology, Canterbury District Health Board, Christchurch, New Zealand; 3Department of Medicine, University of Otago, Dunedin, New Zealand; 4Department of Gastroenterology, Southern District Health Board, Dunedin, New Zealand; 5Department of Gastroenterology, Hawkes Bay District Health Board, Hastings, New Zealand; 6Department of Gastroenterology, Waitemata District Health Board, Auckland, New ZealandCorrespondence: Robert HackettDepartment of Gastroenterology, Hutt Valley District Health Board, Lower Hutt, New ZealandTel +64 4 566 6999Correspondence Email rob_hackett@hotmail.co.ukAim: This study audits the delivery and standards of New Zealand (NZ) inflammatory bowel disease (IBD) care against international standards, with emphasis on the IBD nursing role.Methods: Utilising international standards in IBD care, a 3 phase national multicentre survey study was performed between 2015 and 2019. We 1) evaluated the current role and practices of IBD nurses, 2) evaluated IBD service provision and identified areas for improvement, and 3) audited key aspects of IBD patient care, directly comparing nurse-led and doctor-led outpatient clinics.Results: The median duration spent in an IBD nursing role was 21 months (range 2 to 120 months) with the majority (12/15) performing two or more nursing roles. The median IBD nurse full-time equivalent (FTE) was 0.8 (range 0.2 to 1.25). The average number of hours spent undertaking IBD nursing tasks was 22.2 – a 6.8-hour shortfall compared to rostered hours. No service had a per capita IBD multidisciplinary team (MDT) FTE which met international standards. Just under two-thirds (62.5%) of departments held a regular MDT meeting. All responding services could be contacted directly by IBD patients and respond within 48 hours of contact. During 492 doctor-led and 196 nurse-led scheduled outpatient clinic visits, nurses were significantly more likely to document weight, smoking status and organise appropriate colonoscopic surveillance than doctors.Conclusion: Multiple nursing job roles resulted in rostered hours being insufficient to complete IBD specific tasks. IBD FTE did not meet international standards. The IBD care was patient-centred, encouraging direct contact from patients with prompt response. IBD nurses in NZ provide high-quality outpatient care when measured against auditable standards. As the IBD nursing role continues to develop, following the implementation of an educational framework and education programme, an increase in numbers is required in order to achieve the recommended minimum FTE per 250 000 population.Keywords: inflammatory bowel disease, standards, specialist nursing, New Zealand

There exist few recommendations for managing stocks with spasmodic recruitment, despite such stocks being not uncommon. Management procedures (MPs), developed for two species of redfish (Sebastes mentella and Sebastesfasciatus) in eastern Canada, are recommended for setting catch limits during periods of high and low abundance. A well-designed fishery-independent trawl survey is essential to provide advance warning of strong recruitment events and project future recruitment. Under an 'inventory management' strategy, a more appropriate aim in spasmodic stocks may be to maximize the number of years with 'good catches,' instead of maximizing total catches, as is traditionally considered in management strategy evaluation (MSE). Following a spasmodic recruitment event, an empirical harvest control rule based on larger fish delays the harvest of large cohorts by a few years, targets more commercially valuable fish sizes, and reduces the risk of growth overfishing. Capped MPs produced longer periods of large catches than uncapped MPs. MPs allowed for low harvests during periods of low abundance, thus avoiding unnecessary hardship in the industry. MPs evaluated here could be good candidates for other stocks with similar or less extreme recruitment variability. Il existe peu de recommandations pour la gestion des stocks a recrutement spasmodique, malgre le fait que ces stocks ne soient pas rares. Des procedures de gestion (PG) elaborees pour deux especes de sebastes (Sebastes mentella et Sebastesfasciatus) dans l'est du Canada sont recommandees pour l'etablissement des limites de prises en periodes de forte et de faible abondance. Une evaluation au chalut independante de la peche bien concue est necessaire pour pouvoir prevoir en temps opportun les episodes de fort recrutement et etablir des projections de recrutement futur. Dans une strategie de <>, un objectif plus pertinent pour les stocks spasmodiques pourrait consister a maximiser le nombre d'annees de <>, plutot que les prises totales, comme c'est traditionnellement les cas dans les evaluations des strategies de gestion (ESG). A la suite d'un episode de recrutement spasmodique, une regie de controle des prises empirique basee sur les plus gros poissons retarde la peche de grandes cohortes de quelques annees, cible les tailles de poisson de plus grande valeur commerciale et reduit le risque de surpeche du potentiel de croissance. Des PG plafonnees produisent de plus longues periodes de prises importantes que des PG non plafonnees. Les PG permettent des prises plus faibles en periodes de faible abondance, evitant ainsi des moments difficiles pour l'industrie. Les PG evaluees dans l'etude pourraient constituer de bonnes options pour d'autres stocks dont la variability du recrutement est semblable ou moins extreme. [Traduit par la Redaction], Introduction Developing an understanding of population dynamics and identifying management approaches consistent with this understanding have been among the chief aims of fisheries management science. To facilitate the achievement of [...]

Predation risk and competition among conspecifics significantly affect survival of juvenile salmon, but are rarely incorporated into models that predict recruitment in salmon populations. Using densities of harbour seals (Phoca vitulina) and numbers of hatchery-released Chinook salmon (Oncorhynchus tshawytscha) smolts as covariates in spatially structured Bayesian hierarchical stock-recruitment models, we found significant negative correlations between seal densities and productivity of Chinook salmon for 14 of 20 wild Chinook populations in the Pacific Northwest. Changes in numbers of seals since the 1970s were associated with a 74% decrease (95% CI: -85%, -64%) in maximum sustainable yield in Chinook stocks. In contrast, hatchery releases were significantly correlated with Chinook productivity in only one of 20 populations. Our findings are consistent with recent research on predator diets and bioenergetics modeling that suggest there is a relationship between harbour seal predation on juvenile Chinook and reduced marine survival in parts of the eastern Pacific. Forecasting, assessment, and recovery efforts for salmon populations of high conservation concern should thus consider including biotic factors, particularly predatorprey interactions. Le risque de predation et la concurrence entre individus d'une meme espece ont une incidence significative sur la survie des saumons juveniles, mais sont rarement integres dans les modeles qui predisent le recrutement dans les populations de saumons. En utilisant la densite de phoques communs (Phoca vitulina) et le nombre de saumoneaux relaches d'ecloseries comme covariables dans des modeles bayesiens hierarchiques spatialement structures de recrutement au stock, nous avons constate la presence de correlations negatives significatives entre la densite de phoques et la productivite de saumons quinnats (Oncorhynchus tshawytscha) pour 14 des 20 populations de saumons quinnats sauvages dans le Pacific Northwest. Des variations des nombres de phoques depuis les annees 1970 sont associees a une baisse de 74 % (IC a 95 % : -85 %, -64 %) du rendement equilibre maximal dans les stocks de saumons quinnats. En revanche, le nombre de saumoneaux relaches d'ecloseries n'est significativement correle a la productivite des saumons quinnats que dans 1 des 20 populations. Nos constatations concordent avec celles de travaux recents sur les regimes alimentaires de predateurs et la modelisation bioenergetique qui donnent a penser qu'il existe une relation entre la predation de saumons quinnats juveniles par les phoques communs et une survie en mer reduite dans certaines parties de l'est de l'ocean Pacifique. La prediction, l'evaluation et les efforts de retablissement de populations de saumons dont la conservation est tres preoccupante devraient donc integrer des facteurs biotiques, en particulier les interactions predateurs-proies. [Traduit par la Redaction], Introduction The abundance of predators and intensity of competition within a spatial arena give rise to risks associated with foraging activities that may ultimately affect the survival rates of juvenile [...]

Most stocks of Atlantic cod (Gadus morhua) in the Northwest Atlantic collapsed in the early 1990s, with little sign of recovery since then. In the southern Gulf of St. Lawrence (sGSL), the failed recovery is due to severe increases in the natural mortality of adult Atlantic cod. We examined the role of predation by grey seals (Halichoerus grypus) in this failed recovery by directly incorporating grey seal predation in the population model for Atlantic cod via a functional response. Estimated predation mortality of adult Atlantic cod increased sharply during the cod collapse and has continued to increase, comprising the majority of mortality since the late 1990s. While predation by grey seals appeared to play a minor role in the collapse of Atlantic cod, we found it to be the main factor preventing recovery. Our results are consistent with the hypothesis that failed recovery is due to predation-driven Allee effects, a demographic effect due to the decline in cod abundance and an emergent effect resulting from increasing grey seal abundance. Under current conditions, extirpation of sGSL Atlantic cod appears likely unless there is a large decline in the abundance of grey seals.La plupart des stocks de morue (Gadus morhua) dans le nord-ouest de l'ocean Atlantique se sont effondres au debut des annees 1990, montrant peu d'indices de retablissement depuis. Dans la partie sud du golfe du Saint-Laurent (sGSL), cette absence de retablissement est due a d'importantes augmentations de la mortalite naturelle des morues adultes. Nous examinons le role de la predation par les phoques gris (Halichoerus grypus) dans ce processus en incorporant directement cette predation dans le modele demographique pour la morue sous la forme d'une reaction fonctionnelle. La mortalite par predation estimee des morues adultes a connu une augmentation marquee durant l'effondrement des stocks de morue et continue d'augmenter, expliquant la majorite de la mortalite depuis la fin des annees 1990. Si la predation par les phoques gris semble avoir joue un role limite dans l'effondrement de la morue, nous constatons qu'il s'agit du principal facteur empechant son retablissement. Nos resultats concordent avec l'hypothese voulant que l'absence de retablissement soit due a des effets d'Allee induits par la predation, un effet demographique decoulant de la baisse d'abondance des morues et un effet emergent decoulant de l'abondance croissante des phoques gris. Dans les conditions actuelles, la disparition de la morue du sGSL semple probable a moins d'une importante diminution de l'abondance des phoques gris. [Traduit par la Redaction], IntroductionMost stocks of Atlantic cod (Gadus morhua) in the Northwest Atlantic collapsed to very low levels of abundance in the late 1980s and early 1990s. Since then, abundance of these [...]

We introduce a Lagrangian movement model that can be used to characterize cyclic migrations of iteroparous fish populations. We demonstrate how movement parameters can be estimated using conventionally available catch-at-age data and provide a description of the potential bias that may arise from model misspecification, data aggregation, and nonstandardized sampling effort. The model can be extended to incorporate covariates representing biological and environmental forces that alter the distribution and migration range of exploited populations. We expect that this movement model will be a useful tool to model fish migration, to illustrate how fisheries dynamics are affected by fish migration, and to be used as an operating model in closed loop simulations to test the robustness of management frameworks to spatial structure and connectivity. Nous presentons un modele de deplacement lagrangien qui peut etre utilise pour caracteriser les migrations cycliques de populations de poissons iteropares. Nous montrons comment des parametres de deplacement peuvent etre estimes en utilisant des donnees generalement disponibles de capture selon l'age et presentons une description du biais potentiel qui peut decouler de la mauvaise definition de parametres du modele, du regroupement de donnees et d'un effort d'echantillonnage non normalise. Le modele peut etre elargi pour y inclure des covariables representant des forces biologiques et environnementales qui modifient la repartition et l'aire de migration de populations exploitees. Nous nous attendons a ce que ce modele de deplacement soit utile pour modeliser la migration de poissons et illustrer l'incidence de cette migration sur la dynamique des peches et qu'il pourrait etre utilise comme modele operatoire dans des simulations en boucle fermee pour evaluer la robustesse de cadres de gestion quand il y a presence de structure ou de connectivite spatiale. [Traduit par la Redaction], Introduction Two of the main drivers of cyclic migration in marine fish species are seasonal availability of food and spawning behavior (Walters and Martell 2004). In many iteroparous species, these [...]

Lethal control is widely employed to suppress the numbers of target wildlife species within restricted management areas. The success of such measures is expected to vary with local circumstances affecting rates of removal and replacement. There is a need both to evaluate success in individual cases and to understand variability and its causes. In Britain, red fox (Vulpes vulpes) populations are culled within the confines of shooting estates to benefit game and wildlife prey species. We developed a Bayesian state-space model for within-year fox population dynamics within such restricted areas and fitted it to data on culling effort and success obtained from gamekeepers on 22 shooting estates of 2 to 36 km2. We used informative priors for key population processes-immigration, cub recruitment and non-culling mortality-that could not be quantified in the field. Using simulated datasets we showed that the model reliably estimated fox density and demographic parameters, and we showed that conclusions drawn from real data were robust to alternative model assumptions. All estates achieved suppression of the fox population, with pre-breeding fox density on average 47% (range 20%-90%) of estimated carrying capacity. As expected, the number of foxes killed was a poor indicator of effectiveness. Estimated rates of immigration were variable among estates, but in most cases indicated rapid replacement of culled foxes so that intensive culling efforts were required to maintain low fox densities. Due to this short-term impact, control effort focussed on the spring and summer period may be essential to achieve management goals for prey species. During the critical March-July breeding period, mean fox densities on all estates were suppressed below carrying capacity, and some maintained consistently low fox densities throughout this period. A similar model will be useful in other situations to quantify the effectiveness of lethal control on restricted areas.

Uraniurn(3+) doped single crystals of RbY2Cl7 with a uranium concentration of 0.05% and 0.2% were grown by the Bridgman-Stockbarger method using RbU2Cl7 as the doping substance. Polished plates of ca. 5 mm in diameter were used for measurements of luminescence and excitation spectra. Since the U3+ ions occupy two somewhat different site symmetries, a splitting of all observed f-f bands was observed. The analysis of the spectra enabled definitively an assignment of 22 crystal field bands for both site symmetries as well as the total crystal field splitting of the ground level, equal to 473 cm-1 and 567 cm-1 for the first and second site symmetry, respectively.

Uraniurn(3+) doped single crystals of RbY2Cl7 with a uranium concentration of 0.05% and 0.2% were grown by the Bridgman-Stockbarger method using RbU2Cl7 as the doping substance. Polished plates of ca. 5 mm in diameter were used for measurements of luminescence and excitation spectra. Since the U3+ ions occupy two somewhat different site symmetries, a splitting of all observed f-f bands was observed. The analysis of the spectra enabled definitively an assignment of 22 crystal field bands for both site symmetries as well as the total crystal field splitting of the ground level, equal to 473 cm-1 and 567 cm-1 for the first and second site symmetry, respectively.

Pinniped populations around the world increased rapidly after hunting and culling during the nineteenth and twentieth centuries ended. Some believe that pinnipeds are now preventing the recovery of certain fish populations, and that controlling pinniped population abundance using lethal measures such as harvesting or by non‐lethal means like contraception could recover fish populations. It is unclear, however, how effective and how long it would take for such methods of population control to bring numbers of pinnipeds down to target levels. We used sex‐ and age‐structured population models to estimate how quickly harbor seal (Phoca vitulina) abundance in British Columbia, Canada, could be reduced by 50%, through combinations of lethal removals and sterilization of adult females. Models were fit to seal abundance, demographic, and harvest data collected between 1879 and 2014. Simulation modeling suggests reliance on contraception exclusively is unlikely to reduce the current harbor seal population (numbering ~100,000) by 50% within 25 years, and would result in more variable outcomes, compared to lethal removals. Contraception could be combined with harvesting to maintain a target abundance of harbor seals (although captive studies with harbor seals are needed to confirm the efficacy of contraception). Our simulation modeling approach provides a useful framework to assess how non‐lethal measures could be integrated into policies that promote active population control of harbor seal numbers. [ABSTRACT FROM AUTHOR]

Ecosystem models are thought to offer advantages over single-species models in terms of management policy analysis. This hypothesis has proven difficult to test because of underlying system complexities, coupled with short time series and minimal contrast in environmental conditions or management policies. This paper presents a Bayesian statistical catch-at-age model to compare ecosystem models and test hypotheses about the management of a recreational fishery based on a predatorprey system using a relatively simple and data-rich ecosystem in a large lake, Kootenay Lake, British Columbia, where kokanee (Oncorhynchus nerka) are the prey and piscivorous rainbow trout (Oncorhynchus mykiss) are the predator. A model that explicitly incorporates the predator-prey interaction explained long-term data of field and fishery surveys much better than single-species models without any interactions. Minimally realistic multispecies models that treated predation identically but differed in their representation of the effects of prey abundance on predator mortality produced quite different results. Management reference points, for example, differed considerably between the models. Our study thus emphasizes that the choice of a management approach for this type of fishery will depend strongly on the model form and should take into consideration results from empirically based models that include species interactions. Les modeles ecosystemiques presenteraient des avantages par rapport aux modeles a espece unique en ce qui concerne l'analyse de politiques de gestion. Cette hypothese s'est averee difficile a verifier en raison de complexites systemiques sousjacentes, jumelees a de courtes series chronologiques et au peu de difference entre les differentes conditions environnementales et politiques de gestion. L'article presente un modele statistique bayesien de prises selon l'age pour comparer les modeles ecosystemiques et verifier des hypotheses concernant la gestion d'une peche recreative reposant sur un systeme predateurproie, qui utilise un systeme relativement simple et riche en donnees dans un grand lac, le lac Kootenay (Colombie-Britannique), dans lequel le kokani (Oncorhynchus nerka) est la proie et la truite arc-en-ciel (Oncorhynchus mykiss) piscivore, le predateur. Un modele qui incorpore explicitement les interactions predateurs-proies explique beaucoup mieux les donnees a long terme tirees d'etudes de terrain et d'etudes sur les peches que les modeles a espece unique sans aucune interaction. Des modeles multiespeces minimalement realistes qui traitent la predation de maniere identique, mais different sur la maniere de representer les effets de l'abondance des proies sur la mortalite des predateurs ont produit des resultats assez differents. Les points de reference pour la gestion, par exemple, varient considerablement selon le modele. Notre etude souligne donc le fait que le choix de l'approche de gestion pour ce type de peche dependra fortement de la forme du modele et devrait tenir compte des resultats de modeles reposant sur des donnees empiriques qui integrent les interactions d'especes. [Traduit par la Redaction], Introduction Ecosystem models that explicitly include multispecies interactions and effects of physical environmental conditions have been advocated for ecosystem-based management of fisheries (Plaganyi 2007; Hewett and Johnson 1992; Christensen and [...]

We develop and test spatial population dynamics models that estimate age-dependent offshore movement of fish populations from spatial fishery data. Spatially aggregated population dynamics models produced biased estimates of maximum sustainable yield (MSY) reference points when spatial dynamics were simulated. Spatial population dynamics models provided relatively unbiased estimates of MSY reference points regardless of whether spatial dynamics were simulated. We demonstrate that by using conventional fishery data that are disaggregated spatially, it is possible to estimate movement with age and obtain more accurate estimates of management reference points. The new spatial models were fitted to data for Gulf of Mexico red grouper (Epinephelus morio) and gag grouper (Mycteroperca microlepis) to estimate spatial distribution and offshore movement with age. Offshore ontogeny was estimated to be stronger for gag grouper than red grouper and predicted a larger fraction of older gag grouper in deeper waters. Nous avons elabore et mis a l'essai des modeles spatiaux de dynamique des populations qui estiment les deplacements au large dependants de l'age de populations de poissons a partir de donnees de peche spatiales. Les modeles de dynamique des populations agreges dans l'espace produisaient des estimations biaisees des points de references pour le rendement equilibre maximum (MSY) quand la dynamique spatiale etait simulee. Les modeles spatiaux de dynamique des populations fournissaient des estimations relativement non biaisees des points de references pour le MSY, peu importe si la dynamique spatiale etait simulee. Nous demontrons qu'en utilisant des donnees de peche conventionnelles spatialement desagregees, il est possible d'estimer les deplacements selon l'age et d'obtenir des estimations plus exactes des points de reference utilises pour la gestion. Les nouveaux modeles spatiaux ont ete cales sur des donnees sur le merou rouge (Epinephelus morio) et la badeche baillou (Mycteroperca microlepis) du golfe du Mexique afin d'estimer la repartition spatiale et les deplacements au large selon l'age. Il a ete estime que l'ontogenese au large etait plus forte pour la badeche baillou que pour le merou rouge, et elle predisait une plus grande fraction de badeches baillous plus agees en eaux profondes. [Traduit par la Redaction], Introduction A number of marine fish species occupy different habitats as they grow (ontogenetic habitat shifts). The principal evolutionary benefits of this life history strategy relate to the trade-off between [...]

Species at risk with secretive breeding behaviours, low densities, and wide geographic range pose a significant challenge to conservation actions because population trends are difficult to detect. Such is the case with the Marbled Murrelet (Brachyramphus marmoratus), a seabird listed as 'Threatened' by the Species at Risk Act in Canada largely due to the loss of its old growth forest nesting habitat. We report the first estimates of population trend of Marbled Murrelets in Canada derived from a monitoring program that uses marine radar to detect birds as they enter forest watersheds during 923 dawn surveys at 58 radar monitoring stations within the six Marbled Murrelet Conservation Regions on coastal British Columbia, Canada, 1996-2013. Temporal trends in radar counts were analyzed with a hierarchical Bayesian multivariate modeling approach that controlled for variation in tilt of the radar unit and day of year, included year-specific deviations from the overall trend ('year effects'), and allowed for trends to be estimated at three spatial scales. A negative overall trend of -1.6%/yr (95% credibility interval: -3.2%, 0.01%) indicated moderate evidence for a coast-wide decline, although trends varied strongly among the six conservation regions. Negative annual trends were detected in East Vancouver Island (-9%/yr) and South Mainland Coast (-3%/yr) Conservation Regions. Over a quarter of the year effects were significantly different from zero, and the estimated standard deviation in common-shared year effects between sites within each region was about 50% per year. This large common-shared interannual variation in counts may have been caused by regional movements of birds related to changes in marine conditions that affect the availability of prey.

We applied a spatially and seasonally structured stock reduction analysis (SRA) model to white sturgeon (Acipenser transmontanus) in the lower Fraser River, British Columbia, to estimate trends in abundance since the 1800s and evaluate the current status of the population. We used a sequential Bayesian state-space estimation approach to incorporate prior information from other analyses and evaluate the updating of prior knowledge within the SRA model. The estimated ratio of the abundance of spawning fish in 2004 to relative to unfished conditions was slightly higher than estimates from other studies; on average, 27% of the posterior probability was associated with a 2004 spawning stock abundance of 50% or less of the unfished abundance. Estimates of the current abundance of fish vulnerable to the lower Fraser River recreational fishery were higher than those obtained in other recent SRAs that ignored spatial structure. We also performed the analysis using a spatially aggregated version of the SRA model and obtained lower estimates of unfished biomass and depletion and higher estimates of fishing mortality rates compared with the spatially structured model. We evaluated two structural hypotheses about age-specific vulnerabilities in the historical commercial fishery; assumed vulnerabilities had a marked impact on estimated fishing mortality rates. Nous avons applique un modele d'analyse de reduction du stock (SRA) structuree spatialement et selon les saisons a l'esturgeon blanc (Acipenser transmontanus) dans le cours inferieur du fleuve Fraser, en Colombie-Britannique, afin d'estimer les tendances en matiere d'abondance depuis les annees 1800 et evaluer l'etat actuel de[[bar.L].sub.A]population. Nous avons fait appel a une approche d'estimation bayesienne sequentielle a espace d'etats pour incorporer de l'information a priori tiree d'autres analyses et evaluer[[bar.L].sub.A]mise a jour des connaissances a priori dans le modele SRA. Le rapport estime de l'abondance des poissons reproducteurs en 2004 a l' abondance dans des conditions de non- exploitation etait legerement superieur aux estimations issues d'autres etudes; en moyenne, 27 % de[[bar.L].sub.A]probabilite a posteriori etait associee a une abondance du stock reproducteur de 2004 equivalant a 50 % ou moins de l' abondance non exploitee. Les estimations de l' abondance actuelle de poissons vulnerables a[[bar.L].sub.A]peche recreative dans le bas Fraser etaient superieures a celles issues d'autres SRA recentes qui ne tenaient pas compte de[[bar.L].sub.A]structure spatiale. Nous avons egalement effectue l'analyse en utilisant une version spatialement agregee du modele SRA, qui a donne des estimations plus faibles de[[bar.L].sub.A]biomasse non exploitee et de l'epuisement et des valeurs estimees plus elevees des taux de mortalite par peche que le modele spatialement structure. Nous avons evalue deux hypotheses structurales concernant les vulnerabilites associees a l'age dans[[bar.L].sub.A]peche commerciale historique. Les vulnerabilites presumees avaient une incidence marquee sur les taux estimes de mortalite par peche. [Traduit par[[bar.L].sub.A]Redaction], Introduction The specification of stock rebuilding and fishery management reference points for fish populations of conservation concern often involves the estimation of unfished abundance and depletion (Clark 1991; Chale-Matsau et [...]

Hierarchical Bayesian meta-analysis can be a useful method for improving estimation of key parameters for harvested fish populations. In hierarchical models, data from multiple populations are used simultaneously to obtain estimates of parameters for individual populations and characterize the variability among populations. Many populations of Pacific rockfishes (Sebastes spp.) have declined off the US West Coast since the 1980s, and there is also concern for their conservation in Canada. We develop a hierarchical Bayesian meta-analysis to improve estimates of stock--recruit parameters, characterize management-related parameters (e.g., optimal harvest rate), and address uncertainties in the structural form of the stock--recruit function for Pacific rockfishes. We estimate steepness and optimal harvest rates for 14 populations of Pacific rockfishes under alternative assumptions about the underlying stock--recruit function (Beverton--Holt and Ricker). We provide a posterior predictive distribution of steepness for rockfishes that can be used as a prior in future assessments for similar populations. We also evaluate whether [F.sub.40%] is an appropriate proxy for [F.sub.MSY] for Pacific rockfishes and show that uncertainty in the natural mortality rate can have a significant effect on management advice derived from meta-analyses of stock--recruit data. Resume: Une meta-analyse hierarchique bayesienne peut etre une methode utile pour ameliorer l'estimation des parametres importants des populations de poissons exploitees. Dans les modeles hierarchiques, on utilise simultanement des donnees provenant de plusieurs populations pour obtenir des estimations des parametres pour les populations individuelles et caracteriser la variabilite entre les populations. Plusieurs populations de sebastes (Sebastes spp.) du Pacifique connaissent un declin depuis les annees 1980 sur la cote occidentale des E.-U. et il y a aussi des inquietudes au sujet de leur conservation au Canada. Nous avons mis au point une meta-analyse hierarchique bayesienne pour ameliorer l'estimation des parametres de stock-recrutement, pour caracteriser les parametres relies a la gestion (par ex., le taux optimal de recolte) et pour tenir compte de certaines incertitudes concernant la forme structurelle de la fonction stock-recrutement chez les sebastes du Pacifique. Nous estimons l'inclinaison et les taux optimaux de recolte de 14 populations de sebastes du Pacifique sous diverses presuppositions de rechange concernant les fonctions sous-jacentes de stock-recrutement (Beverton--Holt et Ricker). Nous fournissons une distribution predictive a posteriori de l'inclinaison pour les sebastes qui peut servir de distribution a priori dans des evaluations futures de populations semblables. Nous verifions aussi si [F.sub.40%] peut servir de valeur de remplacement de [F.sub.MSY] chez les sebastes du Pacifique et nous demontrons que l'incertitude dans le taux de mortalite naturelle peut avoir un effet significatif sur les recommandations de gestion tirees des meta-analyses des donnees de stock-recrutement. [Traduit par la Redaction], Introduction More than 70 species of Pacific rockfishes (Sebastes spp.) occur along the western coast of North America from the Gulf of California to the Bering Sea (Love et al. [...]

: Relative abundance indices derived from nominal catch-per-unit-effort (CPUE) data are a principle source of information for the majority of stock assessments. A particular problem with formulating such abundance indices for pelagic species such as tuna is the interpretation of CPUE data from fleets that have changed distribution over time. In this research, spatial population dynamics are simulated to test the historical pattern of fishing effort as a basis for making inferences about relative abundance. A number of age-structured, spatially disaggregated population dynamics models are described for both Atlantic yellowfin tuna (Thunnus albacares) and bigeye tuna (Thunnus obesus) to account for uncertainty in spatial distribution and movement. These models are used to evaluate the reliability of standardization methods and a commonly applied model selection criterion, Akaike's information criterion (AIC). The simulations demonstrate the pitfalls of aggregating CPUE data over spatial areas and highlight the need for data imputation. Simulations support simpler models than those selected using AIC for extracting reliable indices of relative abundance. Resume: Les indices d'abondance relative derives des donnees de prises nominales par unite d'effort (CPUE) sont une source principale d'information dans la majorite des evaluations de stocks. Un probleme particulier dans la formulation de tels indices d'abondance pour les especes pelagiques, telles que le thon, est l'interpretation des donnees de CPUE provenant des flottes qui ont change de repartition dans le temps. Nous simulons dans notre recherche des dynamiques de populations spatiales afin d'evaluer les patrons d'efforts de peche du passe comme base pour deduire l'abondance relative. Nous decrivons un certain nombre de modeles de dynamique de population structures d'apres l'age et spatialement desagre ges pour a la fois l'albacore a nageoires jaunes (Thunnus albacares) et le thon ventru (Thunnus obesus) pour tenir compte de l'incertitude dans la repartition spatiale et les deplacements. Ces modeles servent a evaluer la fiabilite des methodes de standardisation et du critere d'information d'Akaike (AIC), un critere d'emploi courant de selection des modeles. Les simulations demontrent les pieges relies a l'integration des donnees de CPUE sur des etendues spatiales et soulignent la necessite de l'imputation des donnees. Les simulations appuient l'utilisation de modeles plus simples que ceux retenus par l'AIC pour extraire des indices fiables d'abondance relative. [Traduit par la Redaction], Introduction Relative abundance indices derived from fisheries catch rate data (catch-per-unit-effort (CPUE) data) remain a principle source of information for the majority of stock assessments despite many associated problems (e.g., [...]

Abstract--The time series of abundance indices for many groundfish populations, as determined from trawl surveys, are often imprecise and short, causing stock assessment estimates of abundance to be imprecise. To [...]

This paper presents a Bayesian methodology to estimate fishing mortality rates and transoceanic migration rates of highly migratory pelagic fishes that integrates multiple sources of tagging data and auxiliary information from prior knowledge. Exploitation rates and movement rates for Atlantic bluefin tuna (Thunnus thynnus) are estimated by fitting a spatially structured model to three types of data obtained from pop-up satellite, archival, and conventional tags for the period 1990-2006 in the western North Atlantic. A sequential Bayesian statistical approach is applied in which the key components of the model are separated and fitted sequentially to data sets pertinent to each component with the posterior probability density function (pdf) of parameters from one analysis serving as the prior pdf for the next. The approach sequentially updates the estimates of age-specific fishing mortality rates (F) and transoceanic movement rates (T). Estimates of recent F are higher than the estimated rate of natural mortality and higher in the east than in the west. Estimates of annual T from the west to the east are higher for larger fish (6% for ages 0-3 to 16% for ages 9+). These estimates are also higher than those obtained from tagging studies before the 1990s and could be associated with changes in stock composition. Notre travail presente une methode bayesienne pour estimer les taux de mortalite dus a la peche et les taux de migration transoceanique de poissons pelagiques fortement migrateurs qui integre de multiples sources de donnees de marquage et des informations auxiliaires provenant de connaissances anterieures. Nous estimons les taux d'exploitation et de deplacement des thons rouges (Thunnus thynnus) en ajustant un modele a structure spatiale a trois types de donnees provenant d'etiquettes satellites detachables, d'etiquettes enregistreuses et d'etiquettes ordinaires durant la periode 1990-2006 dans l'ouest de l'Atlantique Nord. Nous utilisons une approche statistique bayesienne sequentielle dans laquelle les composantes essentielles du modele sont separees et ajustees sequentiellement a des ensembles de donnees pertinentes a chaque composante et dans laquelle la fonction de densite de probabilite (pdf) a posteriori des parametres d'une analyse servent de pdf a priori pour l'analyse suivante. Cette approche remet a jour sequentiellement les estimations des taux de mortalite dus a la peche en fonction de l'age (F) et les taux de deplacements trans-oceaniques (T). Les estimations des F recents sont superieures aux taux estimes de mortalite naturelle et plus elevees dans l'est que dans l'ouest. Les estimations du T annuel de l'ouest vers l'est sont superieures pour les poissons plus grands (6 % aux ages 0-3 a 16 % aux ages 9+). Ces estimations sont aussi superieures a celles faites a partir des etudes de marquage anterieures aux annees 1990 et pourraient etre reliees a des changements de composition de stocks. [Traduit par la Redaction], Introduction Mark-recapture data sets enable estimation of movement and exploitation rates if tagged fish are representative of the target population, if all recaptured tags are reported or the reporting rate [...]

Abstract: This paper presents a sequential Bayesian framework for quantitative fisheries stock assessment that relies on a wide range of fisheries-dependent and -independent data and information. The presented methodology combines [...]

Atlantic bluefin tuna (Thunnus thynnus) is considered to be overfished, but the status of its populations has been debated, partly because of uncertainties regarding the effects of mixing on fishing grounds. A better understanding of spatial structure and mixing may help fisheries managers to successfully rebuild populations to sustainable levels while maximizing catches. We formulate a new seasonally and spatially explicit fisheries model that is fitted to conventional and electronic tag data, historic catch-at-age reconstructions, and otolith microchemistry stock-composition data to improve the capacity to assess past, current, and future population sizes of Atlantic bluefin tuna. We apply the model to estimate spatial and temporal mixing of the eastern (Mediterranean) and western (Gulf of Mexico) populations, and to reconstruct abundances from 1950 to 2008. We show that western and eastern populations have been reduced to 17% and 33%, respectively, of 1950 spawning stock biomass levels. Overfishing to below the biomass that produces maximum sustainable yield occurred in the 1960s and the late 1990s for western and eastern populations, respectively. The model predicts that mixing depends on season, ontogeny, and location, and is highest in the western Atlantic. Assuming that future catches are zero, western and eastern populations are predicted to recover to levels at maximum sustainable yield by 2025 and 2015, respectively. However, the western population will not recover with catches of 1750 and 12,900 tonnes (the "rebuilding quotas") in the western and eastern Atlantic, respectively, with or without closures in the Gulf of Mexico. If future catches are double the rebuilding quotas, then rebuilding of both populations will be compromised. If fishing were to continue in the eastern Atlantic at the unregulated levels of 2007, both stocks would continue to decline. Since populations mix on North Atlantic foraging grounds, successful rebuilding policies will benefit from trans-Atlantic cooperation.

Abstract: A Bayesian state--space mark--recapture model is developed to estimate the exploitation rates of fish stocks caught in mixed-stock fisheries. Expert knowledge and published results on biological parameters, reporting rates [...]