Bayesian statistics for fishery stock assessment and management

This work is about the use of Bayesian statistics in fishery stock assessment and management. Multidimensional posterior distributions replace classical parameter estimation in surplus-production and delay-difference models. The maximization of expected utilities replaces the estimation of optimal policies. Adaptive importance sampling is used to obtain approximations for posterior distributions. The importance function is given as a finite mixture of heavy-tailed Student distributions. The performance of the method is tested in five case-studies, two of which use data simulation. Real data refer to Skeena river salmon (Oncorhynchus nerka), Orange Roughy (Hoplostethus atlanticus) and Pacific cod (Gadus macrocephalus). The results show that the technique successfully approximates posterior distributions in higher dimensions even if such distributions are multimodal. When comparing models in terms of their performance as management tools, simpler and less realistic models can do better than more sophisticated alternatives. The Bayesian approach also sheds new light on the controversy about the Orange Roughy fishery.Science, Faculty ofStatistics, Department ofGraduat

Bayesian age and growth analysis of the shortfin mako shark Isurus oxyrinchus in the Western South Atlantic Ocean using a flexible model

Age and growth estimates of shortfin mako sharks Isurus oxyrinchus from the western South Atlantic Ocean were obtained through the analysis of vertebral sections of 245 specimens (126 females, 116 males and 3 with undetermined sex), ranging in size from 78 to 330 cm fork length (FL), using a flexible growth model (Schnute model) and a Bayesian approach. A significant linear relationship was found between FL and vertebral radius for sexes combined. Marginal increment analyses were inconclusive about periodicity of growth band deposition and an annual periodicity was assumed to make age estimations. Specimens were estimated to be between 0 and 28 years of age. The Schnute model provided a good description of the individual growth for both sexes up to 15 years of age. Shortfin mako growth during the first year of life was 33.9 cm (ICr95% = 19.9-40.8) for females and 30.5 cm (ICr95% = 25.6-35.4) for males. Until approximately 15 years of age, both sexes showed similar growth and reached similar to 217 cm FL. Sigmoid shaped growth curves obtained for both sexes indicated a change in the growth pattern close to 7 years of age. Inconclusive results about periodicity of growth band deposition in the study area make necessary the application of more robust validation techniques in the future. Meanwhile, a precautionary approach that assumes an annual deposition pattern in the western South Atlantic can be used for the assessment and management of stocks of this species, characterized by low fecundity and late maturity.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Abundance of bottlenose dolphins, Tursiops truncatus (Cetacea: Delphinidae), inhabiting the Patos Lagoon estuary, southern Brazil: implications for conservation

A new mark-recapture abundance estimate and a photographic census were carried out to investigate the possible decline in the abundance of the bottlenose dolphins, Tursiops truncatus (Montagu, 1821), in the Patos Lagoon estuary due to the high levels of bycatch mortality which occurred between 2002 and 2006 in oceanic coastal areas close to the estuary. Fourteen systematic boat surveys were conducted between August and early December 2005 to photo-identify the bottlenose dolphins. The estimated number of animals, with long-lasting marks, in the population obtained from Chapman's and Mth models were 51 (95% CI = 49-53) and 52 (95% CI = 51-60), respectively. Taking into account the proportion of dolphins with long-lasting marks in the population, the total estimated population size ranged between 84 (95% CI = 76-93) and 86 (95% CI = 78-95) individuals, respectively, which was very similar to the 84 individuals revealed by the population census. Our results did not differ from the abundance estimate carried out in 1998, prior to the high fishing-related mortality event, suggesting that the population is stable. Plausible argument to explain the stability of the population is that some carcasses found on the oceanic coastal beaches near Patos Lagoon estuary come from animals that do not belong to the estuary community. Future studies should investigate fine-scale habitat partition between estuarine and adjacent coastal dolphins. If the existence of different communities living in close proximity (estuarine and coastal areas near to the estuary) is confirmed, a new abundance estimate is needed to access the conservation status of bottlenose dolphins in this region

Guidelines to merge stranding databases: the case of franciscana (Pontoporia blainvillei) in the extreme South of Brazil

Strandings of several species of marine mammals have been monitored over the years off the south coast of Rio Grande do Sul State, southern Brazil. A long time series of records implies extensive databases on strandings. In the region, these databases are maintained by two institutions: (i) Núcleo de Educação e Monitoramento Ambiental (NEMA) [Environmental Education and Monitoring Nucleus] and (ii) Laboratório de Ecologia e Conservação da Megafauna Marinha (ECOMEGA) [Ecology and Conservation of Marine Mefagauna Laboratory] at the Federal University of Rio Grande – FURG. In order to make the time series as complete as possible and to make it a reliable source for research related to a particular species and region, the present work proposes a methodology for unifying both databases for franciscana (Pontoporia blainvillei) for the period 2000 - 2020 (NEMA, n = 3,029; FURG, n = 4,629). To build the unified database, specific metrics were outlined for the species and region, in order to confirm a ‘match’ of a record. The ‘match’ variable is a subjective value that classifies the resighting of a stranded animal as excellent (1), good (2), or regular (3). With the implementation of guidelines to merge stranding databases 1,812 ‘excellent’ and 97 ‘good’ combinations were recorded. Sixty records classified as 30 ‘regular’ matches were kept in the database, as they are possibly not recounts due to large differences in our primary and secondary metrics. To characterize a reliable match between distinct databases, the general guidelines outlined here need to be adapted according to the species of interest and the specificities of each monitoring program. The methodology developed to unify the databases had as its main objective the identification of matches

Sexual development, size at maturity, size at maternity and fecundity of the blue shark Prionace glauca (Linnaeus, 1758) in the Southwest Atlantic

Size at maternity and size at maturity of the blue shark Prionace glauca were studied from samples collected during ten commercial longline fishing cruises off southern Brazil and in adjacent international waters. The sharp increase of the amplitude of the values of reproductive variables at a given fork length (FL) was evidence that from that FL reproduction occurred. Thus, we calculated the proportion of mature sharks in FL classes to estimate the median size at maturity. The accelerated growth of the claspers started before the beginning of the testis maturation and semen production, whereas the accelerated development of the ovary and the oviducal glands started simultaneously. Although most females with mating marks were mature, few had sperm stored in the oviducal glands. The population parameter of size at 50% of maturity was estimated at 171.2 cm FL for females and 180.2 cm FL for males. The median size at maternity was estimated in 193.9 cm FL and half of the females with five to six years old were recruited for reproductive phase of life. As most shark species, P. glauca in the Southwest Atlantic reach maturity at about three-fourths of its maximum size and half of its maximum age. Median litter size was 33 embryos. A positive not significant linear relationship between the uterine fecundity and the size of the pregnant female was observed. (C) 2014 Elsevier B.V. All rights reserved.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Modelling the distribution of marine fishery resources: Where are we?

Ecological niche models (ENMs) and species distribution models (SDMs) have been widely applied to various studies relevant to biogeography, conservation biology, and ecology. These modelling techniques seek to develop spatial maps for projecting, among others past, current, and future species distributions. Born in the field of terrestrial ecology, only in recent years have these models been applied to marine environmental issues, especially to improve the forecasting of the distribution of occurrences and capturing of fishery resources. This study aimed to present through bibliometric analysis the characteristics of articles related to the use of ENMs and SDMs in marine fishery resources considering three main points: (1) state of the art: number of articles over the years, journals, countries, collaborations, and focus of research; (2) characteristics linked to fishery resources: marine biogeographic realms, taxonomic groups, life phases, oceanographic zones, and behaviours; (3) characteristics linked to methods: type of method, type of biological and, environmental data. We provide a list of 378 articles (derived from 930 screened ones), the results, and a discussion of our findings, which represent a baseline for the current status (strengths, limits, and gaps) of the interface between ENMs/SDMs and fishery resources.We would like to thank the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – CAPES for scholarships assigned to LdSR and EK and access to Portal de Periódicos da CAPES for articles survey. MGP thanks the IMPRESS project (RTI2018-099868-B-I00), ERDF, Ministry of Science, Innovation and Universities - State Research Agency. DC would also like to thank the Spanish Ministerio de Ciencia e Innovación-Agencia Estatal de Investigación for grant PID2019-106341GB-I00 (jointly financed by the European Regional Development Fund, FEDER)

Photo-identification of humpback whales, Megaptera novaeangliae, off the Antarctic Peninsula: 1997/98 to 1999/2000

Volume: 47Start Page: 555End Page: 56