Inferring the ecology of north-Pacific albacore tuna from catch-and-effort data

Catch-and-effort data are among the primary sources of information for assessing the status of terrestrial wildlife and fish. In fishery science, elaborate stock-assessment models are fitted to such data in order to estimate fish-population sizes and guide management decisions. Given the importance of catch-and-effort data, we scoured a comprehensive dataset pertaining to albacore tuna (Thunnus alalunga) in the north Pacific ocean for novel ecological information content about this commercially valuable species. Specifically, we used unsupervised learning based on finite mixture modelling to reveal that the north Pacific albacore-tuna stock can be divided into four pseudo-cohorts ranging in age from approximately 3 to 12 years old. We discovered that smaller size pseudo-cohorts inhabit relatively high -- subtropical to temperate -- latitudes, with hotspots off the coast of Japan. Larger size pseudo-cohorts inhabit lower -- tropical to subtropical -- latitudes, with hotspots in the western and central north Pacific. These results offer evidence that albacore tuna prefer different habitats depending on their size and age, and point to long-term migratory routes for the species that the current tagging technology is unlikely to capture in full. We discuss the implications of the results for data-driven modelling of albacore tuna in the north Pacific, as well as the management of the north Pacific albacore-tuna fishery.Comment: 9 pages, 4 figure

Patrones de desove de peces de arrecife comercialmente importantes (Lutjanidae y Serranidae) en el Atlántico tropical suroccidental

Although information on the spawning seasons of commercially important snappers (Lutjanidae) and groupers (Serranidae, subfamily Epinephelinae) is available for the north and central west Atlantic, there is little information for the tropical western South Atlantic (Brazil). As a consequence, there are few fishery regulations in this entire region that take into consideration such information. In this study, we characterized the reproductive cycles of three Epinephelinae serranids (Epinephelus morio, Mycteroperca bonaci and Cephalopholis fulva) and five lutjanids (Lutjanus synagris, L. jocu, L. analis, Ocyurus chrysurus and Rhomboplites aurorubens) that occur in the Abrolhos Bank, Brazil, the largest reef complex in the tropical western South Atlantic. A total of 3528 gonads were collected from May 2005 to October 2007. Temporal variability in spawning patterns was evaluated using the Gonadosomatic Index (GSI) and macroscopic analyses. The peak of reproductive activity for the three grouper species occurred between July and August. Snappers exhibited two peaks of reproductive activity, the more intense of which occurred between September and October. The other peak occurred between February and March, with the exception of the deep-dwelling species R. aurorubens, which only reproduced between February and March. Seasonal patterns were consistent over the two consecutive years that we studied, and these patterns are equivalent to those observed for the Northern Hemisphere, as are the sizes at maturity and at the time of sexual change (for the three protogynous hermaphrodite groupers). Fisheries management in this region could be significantly improved by a combination of catch and effort limitations being imposed during spawning seasons and by overall size limitations, particularly considering that most of the fish caught are generally below size at maturity. The proposed buffer zones for the marine areas that are presently protected in Abrolhos represent an opportunity for implementing both spatial (e.g. setting no-take zones that cover spawning sites) and temporal (e.g. seasonal closures during spawning peaks) management tools, using a participatory approach at the regional scale.A pesar de que se tiene un buen conocimiento sobre la época de freza de los pargos (Lutjanidae) y los meros (Serranidae, subfamilia Epinephelinae) en las zonas norte y central del Atlántico occidental, la información disponible del Atlántico suroccidental es escasa. Como consecuencia, en esta zona aún existen pocas regulaciones pesqueras que tengan en cuenta esta información. En este estudio se caracterizan los ciclos reproductores de tres serránidos Epinephelinae (Epinephelus morio, Mycteroperca bonaci and Cephalopholis fulva) y cinco pargos (Lutjanus synagris, L. jocu, L. analis, Ocyurus chrysurus and Rhomboplites aurorubens) en el Banco de Abrolhos, el mayor complejo de arrecifes del Atlántico suroccidental. Se examinaron un total de 3528 gónadas entre mayo de 2005 y octubre de 2007. La variabilidad temporal de las pautas de puesta se evaluó mediante el Índice Gonadosomático (GSI) y análisis microscópicos. Para los tres meros el máximo en la actividad reproductora se produce entre julio y agosto. Los lutjánidos presentan dos picos de actividad bien diferenciados, siendo el más intenso el que tiene lugar entre septiembre y octubre, mientras que el menor se produce entre febrero y marzo, con la excepción de R. aurorubens, una especie de profundidad, que sólo se reproduce entre febrero y marzo. Las pautas estacionales en la reproducción son consistentes en los dos años consecutivos y, junto a la edad de primera madurez y la edad de inversión sexual (los tres meros son hermafroditas proterogínicos), son equivalentes a las que se producen en el hemisferio septentrional. La gestión pesquera en esta región podría mejorar significativamente mediante una combinación de limitaciones en las capturas y en el esfuerzo durante las épocas de puesta, así como limitando la talla mínima de captura, considerando que la mayoría de individuos capturados actualmente son inmaduros. Las zonas de amortiguación de las áreas marinas actualmente protegidas en Abrolhos representan una buena oportunidad para implementar herramientas de gestión tanto espaciales (e.g. estableciendo zonas de exclusión pesquera en los lugares de freza) como temporales (e.g. prohibiendo la pesca durante la época de reproducción), utilizando una aproximación participativa a una escala regional

Spawning patterns of commercially important reef fish (Lutjanidae and Serranidae) in the tropical western South Atlantic

Although information on the spawning seasons of commercially important snappers (Lutjanidae) and groupers (Serranidae, subfamily Epinephelinae) is available for the north and central west Atlantic, there is little information for the tropical western South Atlantic (Brazil). As a consequence, there are few fishery regulations in this entire region that take into consideration such information. In this study, we characterized the reproductive cycles of three Epinephelinae serranids (Epinephelus morio, Mycteroperca bonaci and Cephalopholis fulva) and five lutjanids (Lutjanus synagris, L. jocu, L. analis, Ocyurus chrysurus and Rhomboplites aurorubens) that occur in the Abrolhos Bank, Brazil, the largest reef complex in the tropical western South Atlantic. A total of 3528 gonads were collected from May 2005 to October 2007. Temporal variability in spawning patterns was evaluated using the Gonadosomatic Index (GSI) and macroscopic analyses. The peak of reproductive activity for the three grouper species occurred between July and August. Snappers exhibited two peaks of reproductive activity, the more intense of which occurred between September and October. The other peak occurred between February and March, with the exception of the deep-dwelling species R. aurorubens, which only reproduced between February and March. Seasonal patterns were consistent over the two consecutive years that we studied, and these patterns are equivalent to those observed for the Northern Hemisphere, as are the sizes at maturity and at the time of sexual change (for the three protogynous hermaphrodite groupers). Fisheries management in this region could be significantly improved by a combination of catch and effort limitations being imposed during spawning seasons and by overall size limitations, particularly considering that most of the fish caught are generally below size at maturity. The proposed buffer zones for the marine areas that are presently protected in Abrolhos represent an opportunity for implementing both spatial (e.g. setting no-take zones that cover spawning sites) and temporal (e.g. seasonal closures during spawning peaks) management tools, using a participatory approach at the regional scale

‘Drivin' with your eyes closed’: Results from an international, blinded simulation experiment to evaluate spatial stock assessments

Spatial models enable understanding potential redistribution of marine resources associated with ecosystem drivers and climate change. Stock assessment platforms can incorporate spatial processes, but have not been widely implemented or simulation tested. To address this research gap, an international simulation experiment was organized. The study design was blinded to replicate uncertainty similar to a real-world stock assessment process, and a data-conditioned, high-resolution operating model (OM) was used to emulate the spatial dynamics and data for Indian Ocean yellowfin tuna (Thunnus albacares). Six analyst groups developed both single-region and spatial stock assessment models using an assessment platform of their choice, and then applied each model to the simulated data. Results indicated that across all spatial structures and platforms, assessments were able to adequately recreate the population trends from the OM. Additionally, spatial models were able to estimate regional population trends that generally reflected the true dynamics from the OM, particularly for the regions with higher biomass and fishing pressure. However, a consistent population biomass scaling pattern emerged, where spatial models estimated higher population scale than single-region models within a given assessment platform. Balancing parsimony and complexity trade-offs were difficult, but adequate complexity in spatial parametrizations (e.g., allowing time- and age-variation in movement and appropriate tag mixing periods) was critical to model performance. We recommend expanded use of high-resolution OMs and blinded studies, given their ability to portray realistic performance of assessment models. Moreover, increased support for international simulation experiments is warranted to facilitate dissemination of methodology across organizations.Peer reviewe

A pesca artesanal no reservatorio Billings (São Paulo)

Orientador: Miguel Petrere JuniorDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de BiologiaResumo: O Reservatório Billings é o maior corpo d'água da Região Metropolitana de São Paulo (RMSP). Sua construção, iniciada em 1925, foi motivada pela demanda de energia elétrica da cidade de São Paulo. Durante muitos anos apresentou baixa qualidade ambiental devido à recepção dos efluentes orgânicos da RMSP através de bombeamento do Rio Pinheiros. Atualmente, é utilizado como sistema regularizador da vazão do Alto Tietê, como manancial de abastecimento, como receptor de efluentes e como área de lazer. Neste reservatório desenvolveu-se uma atividade intensa de pesca artesanal, com 101 pescadores ativos. Este estudo tem como objetivo descrever a atividade de pesca, avaliar a composição da captura em peso, avaliar o esforço de pesca com diferentes artes de pesca e verificar com que fatores está relacionada a captura. Para tal, estabeleceu-se um sistema de coleta diária de dados de desembarque pesqueiro na localidade de Colônia (município de São Paulo), onde se acompanhou a atividade de fevereiro de 1996 a janeiro de 1997. No período de estudo foram desembarcados 147.593 kg de pescado em 3515 viagens de pesca, com rendimento médio de 42 kg/viagem e 572 kg/pescador/mês. As espécies comerciais capturadas são a tilápia do Nilo Oreochromis niloticus (81,4% do desembarque em peso), o lambari Astyanax eigenmanniorum (13,0%), a carpa Cyprinus carpio (2,4%), a traíra Hoplias malabaricus (2,1%), o sagüiru Cyphocarax modestus (1,1%) e o bagre Rhamdia sp (0,1%). As artes de pesca utilizadas são redes de espera, redes de batida e tarrafas. Através do ajuste de um modelo linear de covariância às capturas mensais de tilápia do Nilo constatou-se que a área de pesca é o único fator importante na determinação das capturas descontando o efeito da covariável esforço de pesca. Os fatores mês e arte de pesca não explicam porções significativas da variabilidade. No modelo final, 91,14% da variabilidade total é explicada pelo esforço de pesca e 3,27% pelo fator área de pesca. As áreas de pesca com capturas mais altas são as de Pedreira e Alvarenga, próxima à estação elevatória do rio Pinheiros. Para explicar estes resultados três hipóteses são discutidas: alta capturabilidade, alta produtividade e estratégia dos pescadores. A baixa riqueza e alta dominância das espécies presentes nas capturas é um indicativo de comunidades submetidas a estresse que neste caso são: transformação do ecossistema lótico em lêntico, eutrofização, contaminação e introdução de espécies. A dominância da tilápia do Nllo no reservatório pode ser atribuída a uma combinação de fatores como alta resistência a baixas concentrações de oxigênio dissolvido, tolerância a poluentes, capacidade de aproveitar o zooplâncton dos reservatórios e existência de litoral bem desenvolvido onde pode construir seus ninhosAbstract: Billings reservoir is the largest water body in the Metropolitan Region of São Paulo. Its building started in 1925 in order to supply the city of São Paulo with electricity. During many years it presented low environmental quality due to the reception of organic sewage from the Metropolitan Region. Nowadays, it is used also as an outlet regulatory system from High Tietê Basin, as water source and as leisure area. An intense artisanal fishery activity is developed. with 101 active fishermen. The objectives of this study are to describe the fishery, to evaluate the catch composition in weight, to evaluate the effort with different gears and to examinate the factors that could explain the catches. Landings were recorded daily from February 1996 to January 1997, at Colônia (São Paulo city). During this period 147.593 kg of fish were caught in 3.515 fishing trips by 21.5 fisherman/month in average, with mean yield of 42 kg/trip and 572 kg/fishermen/month. The main commercial species caught were Nile tilapia Oreochromis niloticus (81.4% of landings in weight). "lambari" Astyanax eigenmanniorum (13.0%), common carp Cyprinus carpio (2.4%), "traíra" Hoplias malabaricus (2.1 %), "sagüiru" Cyphocarax modestus (1.1 %) and catfish Rhamdia sp (0.1 %). The fishing gears used were gillnets, cast nets and gillnets used in an active way ("redes de batida"). Nile tilapia are caught with cast nets and gillnets "redes de batida". The other species are caught with gillnets. The fit of a linear covariance model on Nile tilapia catch and effort data showed that the effect of the fishing ground was the only important factor to explain the catches discounting the effect of the covariate fishing effort. Neither the month nor the fishing gear explained a significant portion of the variability. In the final model, effort explained 91.14% of the total variability and fishing ground explained only 3.27 %. The fishing grounds with highest catches were Pedreira and Alvarenga, near Pinheiros river pumping station. To explain this result three hypotheses are discussed: high capturability, high productivity, and fishermen strategies. The low richness and high dominance of few species on landings are indicative of communities under stressing conditions, which in the Billings case are: transformation of a lotic ecosystem in a lentic one, eutrophication, contamination and introduction of exotic species. The dominance of Nile tilapia is attributable to a combination of factors such as high resistance to low dissolved oxygen contents, tolerance to chemical stressors, ability to consume plankton and existence of a developed littoral zone enabling Nile titapia's nestingMestradoEcologiaMestre em Ciências Biológica

Marine Ecology Progress Series

Texto completo: acesso restrito. p. 283-293Our aim was to devise visual sampling protocols to estimate densities in a morphologically and behaviorally diverse assemblage of reef fishes. The focus was on a design that is cost-effective and produces relatively accurate and precise density estimates for the largest number of species. We evaluated the 2 most widely used shapes of sampling units (strip transects and stationary cylinders) of several dimensions on a fringing reef at Fernando de Noronha Archipelago, tropical West Atlantic. Small sampling units produced the best density estimates for small fishes, while large ones produced the best estimates for large fishes, regardless of sampling unit shape. The sampling unit with the lowest cost was the stationary cylinder. We further compared accuracy and precision of density and richness estimates from several combinations of stationary cylinders and fish size. A simple improvement in stationary censuses, i.e. a sampling unit composed of 2 nested cylinders (2 m and 4 m radii, respectively), enhanced the accuracy and precision of estimates. Counts of small fish (≤10 cm) were made in the smaller cylinder and counts of larger fish (>10 cm) were made in the larger. Such nested cylinders reduce the bias towards large and conspicuous species and allow for separate density estimates for adults and juveniles of large species

Padrões de dominância e raridade da assembléia de peixes ao longo de gradientes espaciais no reservatório de Itaipu, Estado do Paraná, Brasil - DOI: 10.4025/actascibiolsci.v25i1.2085

Patterns of dominance and rarity of fish assemblage in the Itaipu Reservoir were evaluated and related to a longitudinal or river-dam gradient (composed of riverine, transitional and lacustrine zones) and to a transversal or upstream-downstream gradients of the tributaries (composed of lotic and lentic stretches of tributaries and reservoir shores). Thirteen sampling stations were sampled quarterly during 2 years. Patterns of species dominance were investigated using Whittaker plots and patterns of rarity using analysis of variance. A total of 85 fish species were caught. In the reservoir shores of riverine zone, the dominant species was the migratory Prochilodontidae curimba Prochilodus lineatus that uses the upstream floodplain as a spawning and nursery area. In the reservoir shores of transitional and lacustrine zones (i.e. close to the dam) the dominant species was the introduced Sciaenidae curvina Plagioscion squamosissimus. Loricarids dominated the tributaries. The proportion of rare species presented significant differences along longitudinal gradient. Lowest proportion of rare species was found close to the dam indicating a loss of ecological integrity in this zonePadrões de dominância e raridade da assembléia de peixes no reservatório de Itaipu foram avaliados e relacionados com os gradientes longitudinal (dividido nas zonas fluvial, intermediária e lacustre) e transversal (dividido em trechos lóticos e lênticos dos tributários e margem do reservatório). As coletas foram realizadas trimestralmente em treze estações durante dois anos. Padrões de dominância e raridade foram investigados utilizando curva de espécie-abundância e análise de variância, respectivamente. Foram capturadas 85 espécies. Na zona fluvial, a espécie dominante na margem do reservatório foi o curimba Prochilodus lineatus, que utiliza a planície de inundação a montante como área de reprodução e crescimento. A curvina Plagioscion squamosissimus, espécie introduzida, foi dominante nas margens do reservatório das zonas intermediária e lacustre. Loricarídeos dominaram nos tributários. A proporção de espécies raras apresentou diferenças significativas ao longo do gradiente longitudinal. Na zona lacustre, próximo à barragem, foi registrada a menor proporção de espécies raras, indicando perda de integridade ecológica nessa zon