Survey sampling for fisheries monitoring in Brazil: implementation and analysis

Informações sobre as descargas pesqueiras realizadas em 2011 ao longo da costa de São Paulo foram utilizadas com o objetivo de avaliar e comparar os métodos de amostragem em campanhas voltadas para o monitoramento pesqueiro. Espera-se com isto um conjunto de dados consistentes, além de uma importante redução de custos. As estimativas da captura total para o estado de São Paulo e por municípios foram relativamente acuradas (alta precisão e baixo viés). A captura estimada por mês, por categoria de pescado e por ambos (domínios não considerados no desenho amostral) demonstraram que quanto maior é o nível de detalhamento menos precisas e mais enviesadas tornam-se as estimativas de captura. Quando comparada com as capturas reais para 2011, a ordem de importância das categorias de pescado baseada nas capturas estimadas alterou-se ligeiramente em algumas posições após o quinto lugar. Houve uma pequena redução de custos devido à amostragem em comparação com a metodologia censitária atualmente em uso no estado de São Paulo (máxima de 15,4%). Os resultados demonstraram que os custos do monitoramento pesqueiro são diretamente proporcionais ao nível de detalhamento e à qualidade dos dados requeridos.Census of fishing data about the landings carried out along the São Paulo coast during 2011 was used to evaluate and compare the survey sampling for fisheries monitoring, expecting reliable results along with an important cost reduction. Estimates of total catch for the São Paulo State as a whole and by municipality were relatively accurate (high precision and low bias). Estimated catch by month, by fish categories and both (factors not considered in the sampling design) demonstrated that, as the level of required detail increased, the catch estimates became more biased and less precise. However, when comparing to the 2011 true catches, the order of importance of fish categories based on estimated catches changed slightly in some positions after the fifth place. There was a minor cost reduction due to the sampling in comparison with the census methodology currently in use (15.4% at most). The results demonstrated that fisheries monitoring costs are directly proportional to the required level of details and data quality

Modelos bayesianos espacio-temporales con datos múltiples de CPUE: el caso de una pesquería de lebranche

We propose a novel Bayesian hierarchical structure of state-space surplus production models that accommodate multiple catch per unit effort (CPUE) data of various fisheries exploiting the same stock. The advantage of this approach in data-limited stock assessment is the possibility of borrowing strength among different data sources to estimate reference points useful for management decisions. The model is applied to thirteen years of data from seven fisheries of the lebranche mullet (Mugil liza) southern population, distributed along the southern and southeastern shelf regions of Brazil. The results indicate that this modelling strategy is useful and has room for extensions. There are reasons for concern about the sustainability of the mullet stock, although the wide posterior credibility intervals for key reference points preclude conclusive statistical evidence at this timeProponemos una nueva estructura jerárquica bayesiana para modelos de producción excedente espacio-temporales que permite incorporar datos de captura por unidad de esfuerzo (CPUE) de diversas fuentes para varias pesquerías que explotan el mismo stock. La ventaja de este enfoque en la evaluación de stocks con datos limitados es la posibilidad de reforzar las estimaciones a partir de diferentes fuentes de datos para estimar puntos de referencia útiles para las decisiones de gestión. El modelo se aplica a trece años de datos de siete pesquerías de la población meridional de lebranche (Mugil liza), distribuidas a lo largo de las regiones sur y sudeste de Brasil. Los resultados indican que esta estrategia de modelado es útil y puede formar la base de futuras extensiones. En cuanto a la sostenibilidad del efectivo de lebranche, hay razones para preocuparse, aunque los amplios intervalos de credibilidad posterior en los puntos clave de referencia excluyen evidencia estadística concluyente en este momento

Changes in the population structure, growth and mortality of striped weakfish Cynoscion guatucupa (Sciaenidae, Teleostei) of southern Brazil between 1976 and 2002

Changes in the population structure, growth, and mortality of the striped weakfish Cynoscion guatucupa of southern Brazil were studied based on data collected from commercial landings in Rio Grande between 1976 and 2002. Mean length in the trawl fishery decreased abruptly while mean ages decreased steadily in recent years. Most abundant age classes in recent landings were 2 and 3 years old in the paired-trawl catches, one to three for otter and double rig trawls, and 5 and 6 years old in the gill net catches. Oldest fishes caught were aged 18 years and no fish over 14 years old was caught since 1985. The growth rate tended to increase over the course of the study, especially in the last analysed period (1999–2002). The total mortality instantaneous coefficient Z calculated from the paired trawls data catch curves increased from 0.36 in 1976 up to 0.92 in 2002 and the exploitation rate E increased from 0.31 up to 0.73 if a natural mortality coefficient M of 0.25 is assumed. The changes were attributed to the increase of the fishing on the striped weakfish stock, shared by Brazil, Uruguay and Argentina and are suggestive of overfishing

Calculating the natural mortality rate for Netuma barba (Lacépède, 1803) (Actinopterygii, Siluriformes, Ariidae)

Submitted by Eliane Silva ([email protected]) on 2015-12-14T19:24:32Z No. of bitstreams: 1 Cálculo da taxa instantânea de mortalidade natural para Netuma barba (Lacépède, 1803) (Actinopterygii, Siluriformes, Ariidae).pdf: 343520 bytes, checksum: 400c591ece48c63cc6885f7952ddc760 (MD5)Approved for entry into archive by Lilian M. Silva ([email protected]) on 2015-12-16T17:01:48Z (GMT) No. of bitstreams: 1 Cálculo da taxa instantânea de mortalidade natural para Netuma barba (Lacépède, 1803) (Actinopterygii, Siluriformes, Ariidae).pdf: 343520 bytes, checksum: 400c591ece48c63cc6885f7952ddc760 (MD5)Made available in DSpace on 2015-12-16T17:01:48Z (GMT). No. of bitstreams: 1 Cálculo da taxa instantânea de mortalidade natural para Netuma barba (Lacépède, 1803) (Actinopterygii, Siluriformes, Ariidae).pdf: 343520 bytes, checksum: 400c591ece48c63cc6885f7952ddc760 (MD5) Previous issue date: 2003The natural mortality instantaneous rate is one of the essential populational parameters in fish population dynamics and fisheries management. The probem when calculating such parameter is to have at least one realistic value. In the present paper, the natural mortality instantaneous rate is estimated for the marine catfish Netuma barba using the TAYLOR, RIKHTER & EFANOV, PAULY and ALAGARAJA methods and the result are discussed. For this species the values 0.12-0.13 were chosen considering them appropriate for the species in the Rio Grande do Sul region.A taxa instantânea de mortalidade natural (M) é fundamental nos modelos de dinâmica populacional dos recursos pesqueiros. Todo o problema de cálculo desta taxa se resume na necessidade de ter pelo menos uma estimativa a mais realista possível deste parâmetro para a população. Neste trabalho foram calculados diferentes valores para o bagre marinho Netuma barba pelos métodos de TAYLOR, RIKHTER & EFANOV, PAULY e de ALAGARAJA e discutidos os resultados. Optou-se por escolher os valores o,12-0,13 como mais apropriados para esta espécie na região do Rio Grande do Sul

Cálculo da taxa instantânea de mortalidade natural para Netuma barba (Lacépède, 1803) (Actinopterygii, Siluriformes, Ariidae)

The natural mortality instantaneous rate is one of the essential populational parameters in fish population dynamics and fisheries management. The probem when calculating such parameter is to have at least one realistic value. In the present paper, the natural mortality instantaneous rate is estimated for the marine catfish Netuma barba using the TAYLOR, RIKHTER & EFANOV, PAULY and ALAGARAJA methods and the result are discussed. For this species the values 0.12-0.13 were chosen considering them appropriate for the species in the Rio Grande do Sul region.A taxa instantânea de mortalidade natural (M) é fundamental nos modelos de dinâmica populacional dos recursos pesqueiros. Todo o problema de cálculo desta taxa se resume na necessidade de ter pelo menos uma estimativa a mais realista possível deste parâmetro para a população. Neste trabalho foram calculados diferentes valores para o bagre marinho Netuma barba pelos métodos de TAYLOR, RIKHTER & EFANOV, PAULY e de ALAGARAJA e discutidos os resultados. Optou-se por escolher os valores o,12-0,13 como mais apropriados para esta espécie na região do Rio Grande do Sul

Diagnóstico do estoque e orientações para o ordenamento da pesca de Umbrina canosai (Berg, 1895)

A castanha é uma espécie demersal de hábitos alimentares epi-bentônicos, crescimento lento, que matura sexualmente com dois anos e 200 mm de comprimento e que atinge uma longevidade superior aos 20 anos. Intensamente explorada na plataforma continental do sul do Brasil vem sendo submetida a taxas de exploração superiores às sustentáveis desde a década de 1970, de acordo a todos os modelos de avaliação aplicados. Como resultado, a biomassa atual provavelmente é inferior a 25% da anterior à pesca industrial. Ao longo dos anos observou-se um aumento no crescimento individual que atenuou a queda da biomassa, mas a manutenção de altos níveis de esforço pode levar a continuação da redução do estoque a ponto de afetar o recrutamento e levar ao colapso da pescaria

Survey sampling for fisheries monitoring in Brazil: implementation and analysis

Abstract Census of fishing data about the landings carried out along the São Paulo coast during 2011 was used to evaluate and compare the survey sampling for fisheries monitoring, expecting reliable results along with an important cost reduction. Estimates of total catch for the São Paulo State as a whole and by municipality were relatively accurate (high precision and low bias). Estimated catch by month, by fish categories and both (factors not considered in the sampling design) demonstrated that, as the level of required detail increased, the catch estimates became more biased and less precise. However, when comparing to the 2011 true catches, the order of importance of fish categories based on estimated catches changed slightly in some positions after the fifth place. There was a minor cost reduction due to the sampling in comparison with the census methodology currently in use (15.4% at most). The results demonstrated that fisheries monitoring costs are directly proportional to the required level of details and data quality

Survey sampling for fisheries monitoring in Brazil: implementation and analysis

Abstract Census of fishing data about the landings carried out along the São Paulo coast during 2011 was used to evaluate and compare the survey sampling for fisheries monitoring, expecting reliable results along with an important cost reduction. Estimates of total catch for the São Paulo State as a whole and by municipality were relatively accurate (high precision and low bias). Estimated catch by month, by fish categories and both (factors not considered in the sampling design) demonstrated that, as the level of required detail increased, the catch estimates became more biased and less precise. However, when comparing to the 2011 true catches, the order of importance of fish categories based on estimated catches changed slightly in some positions after the fifth place. There was a minor cost reduction due to the sampling in comparison with the census methodology currently in use (15.4% at most). The results demonstrated that fisheries monitoring costs are directly proportional to the required level of details and data quality