Empirical equations for the estimation of natural mortality in Mediterranean teleosts

Empirical relationships were established linking estimates of the instantaneous rate of natural mortality (M), the von Bertalanffy growth parameters, L sub( infinity ) (or W sub( infinity )) and K, and annual mean water temperature in 56 stocks of Mediterranean teleosts fish. It is suggested that these relationships generate for these fish more reliable estimates of M than the widely-used model of Pauly (1980, J. Cons. CIEM 33(3):175-192), which was based on 175 fish stocks, but included only five stocks from the Mediterranean.

Consumption to biomass (Q/B) ratio and estimates of Q/B-predictor parameters for Caribbean fishes

Estimates of the Q/B ratio and parameters of equations to 'predict' Q/B values for 116 fish stocks in the Gulf of Salamanca, Colombia are presented. A compilation of these estimates available for Caribbean Sea fishes (264 stocks) is also provided for comparison purposes. General trends in the value of Q/B resulting from differences in the equation and parameter values used are briefly discussed.

Breeding and propagation of tilapia (Oreochromis niloticus) in a floating hatchery, Gabon

Based on the encouraging results obtained by earlier workers, the concept for a floating hatchery was developed for producing tilapia for both farming and enhanced fisheries in the freshwater lakes and coastal lagoons of Gabon. The research and development work to test this concept was undertaken with Nile tilapia (Oreochromis niloticus). Two places in Gabon were selected, representing climatic and environmental condition similar to other parts of the country. The study aims to improve fish production in the freshwater lakes of the Lambarene area, and in the numerous coastal lagoons of Gabon, to compensate for the current overexploitation of natural stocks, or the alternative of introducing other species, and to reduce the drift of fishing population away from lakes.

Evaluating mortality using length-frequency data when growth parameters are poorly known

A method is presented through which the total mortality undergone by several fish stocks of the same species can be compared when growth parameters are poorly known or unknown. Whereas the estimate of Z obtained via the length-converted catch curve is highly sensitive to the input parameters K and L sub( infinity ), the ratio of Z estimates obtained for different stocks with the same combination of parameters is almost independent of these inputs, at least when the fit of the linear regression is good. The method is tested on simulated data and an application is presented using real data from the Lesser Antilles. It provides the possibility of qualitatively comparing several stocks in situations of scarce biological knowledge.

Conservation of the Nilgiri rainbow trout in India

Rainbow trout is one of the important exotic species that is well established in the upland waters of India. This paper presents the historical background of its introduction and the present status of the fish in the streams of he Nilgiri peninsula of India. The rainbow trout inhabits natural reservoirs and streams of the region as a self-recruiting population. The growth rate is reported to be relatively low and conflicting views about its taxonomic status have been reported. Successful crossbreeding of the Nilgiri rainbow trout with trout stocks from the Indian State of Himachal Pradesh has indicated the scope for utilizing cryopreserved milt as a mode of introducing new genetic material into the Nilgiri rainbow trout population. This paper outlines the requirement of ecological and genetic data to develop a strategy for management and reintroduction fresh stocks.

Rice field fisheries: a resource for Cambodia

Small-scale fisheries in and around rice fields in the lowland areas of Cambodia are greatly underestimated and undervalued. Their contribution to the protein requirements of the poor rural households is significant. In Svay Rieng province, they could provide 65-75% of the animal protein requirements of these households. The value could well be around 40% of the value of rice production. It is, therefore, important that these natural stocks and the fisheries are managed well and that developmental activities explicitly consider their impact on these fisheries.

African freshwater fisheries: what needs to be managed?

The management of African freshwater fisheries in Southern African Development Coordination (SADC) countries is discussed. Changes in catch and fishing effort in the SADC freshwater fisheries in the past 50 years, the main causes behind the patterns of change in fishing effort, the effects of fishing effort and environment on the regeneration of fish stocks, as well as existing and proposed fisheries management regulations are investigated.

Proposição de um indicador global de funcionalidade operacional para sistemas de processamento primário em instalações marítimas de produção de petróleo: estudo de caso para o sistema de separação e tratamento de óleo

Este texto verificou o tema de monitoramento de processos de produção de petróleo em plataformas no mar de forma a propor indicadores globais para monitoramento da funcionalidade dos equipamentos que envolvem estes processos, permitindo a antecipação da tomada de decisão sobre suas eminentes quedas de disponibilidade. Para tal, buscando conhecer as áreas envolvidas na gestão de uma plataforma de petróleo no mar, foram identificados os principais sistemas relacionados ao processo de produção de petróleo e optou-se pelo Sistema de Separação e Tratamento de Óleo para desenvolvimento e validação dos indicadores propostos. O Indicador Global de Funcionalidade Operacional (IGFO) foi desenvolvido a partir dos dados disponíveis para monitoramento dos processos de produção de petróleo, focado nas visões das principais áreas envolvidas na gestão da plataforma. Este indicador foi elaborado com objetivo de simplificar a análise dos processos, permitindo assim aferir o desempenho das ações de monitoramento de processos em plataformas de petróleo, de modo a atuar de forma antecipativa, contribuindo com a identificação e a disseminação das melhores práticas de manutenção preditiva. Neste aspecto, os indicadores na forma de normalização utilizada permitem comparações em diversos níveis, tanto em relação as plataformas dentro de uma empresa, como plataformas de empresas diferentes. Os indicadores globais propostos obtiveram resultados que permitiram avaliar a queda de funcionalidade dos equipamentos do Sistema de Separação e Tratamento de Óleo durante o período avaliado, servindo de base para identificação das causas das falhas destes equipamentos. Assim sendo, pôde-se perceber que a utilização dos indicadores globais identificados pode responder com sucesso às necessidades propostas

Identification of Sex and Female’s Reproductive Stage in Commercial Fish Species through the Quantification of Ribosomal Transcripts in Gonads

The estimation of maturity and sex of fish stocks in European waters is a requirement of the EU Data Collection Framework as part of the policy to improve fisheries management. On the other hand, research on fish biology is increasingly focused in molecular approaches, researchers needing correct identification of fish sex and reproductive stage without necessarily having in house the histological know-how necessary for the task. Taking advantage of the differential gene transcription occurring during fish sex differentiation and gametogenesis, the utility of 5S ribosomal RNA (5S rRNA) and General transcription factor IIIA (gtf3a) in the molecular identification of sex and gametogenic stage was tested in different economically-relevant fish species from the Bay of Biscay. Gonads of 9 fish species (, Atlantic, Atlantic-chub and horse mackerel, blue whiting, bogue, European anchovy, hake and pilchard and megrim), collected from local commercial fishing vessels were histologically sexed and 5S and 18S rRNA concentrations were quantified by capillary electrophoresis to calculate a 5S/18S rRNA index. Degenerate primers permitted cloning and sequencing of gtf3a fragments in 7 of the studied species. 5S rRNA and gtf3a transcript levels, together with 5S/18S rRNA index, distinguished clearly ovaries from testis in all of the studied species. The values were always higher in females than in males. 5S/18S rRNA index values in females were always highest when fish were captured in early phases of ovary development whilst, in later vitellogenic stages, the values decreased significantly. In megrim and European anchovy, where gonads in different oogenesis stages were obtained, the 5S/18S rRNA index identified clearly gametogenic stage. This approach, to the sexing and the quantitative non-subjective identification of the maturity stage of female fish, could have multiple applications in the study of fish stock dynamics, fish reproduction and fecundity and fish biology in general.

Reviving the Macrobrachium rosenbergii (de Man) fishery in Vembanad Lake, India

In Vembanad Lake and its confluent rivers (Kerala, India), the catches of Macrobrachium rosenbergii (de Man) were reported to have dwindled to a mere 39 t in the 1980s from average landings of 300 t during the 1960s. This decline is due to the impact of a number of human interventions affecting the ecosystem and, hence, the stocks of M. rosenbergii. Monitoring of landings in 1994-1995 and 1995-1996 indicates an improvement in catches. This paper discusses the reasons for the decline and revival in stocks and suggestions for their replenishment.

Assessment of the fishing effort level in the shrimp fisheries of the central and southern Gulf of California

In view of the concern caused by the declining trend in the annual shrimp yield in the Central Gulf of California, an attempt was made to analyze the fishing effort level exerted upon the shrimp stocks of the blue (Farfantepenaeus stylirostris) and the brown shrimp (F. californiensis) from 1980 to 1991. For this purpose, both Schaefer and Fox production models were applied. The results from these analyses revealed an economic overexploitation condition, and suggested an imperative need to implement as a regulatory measure, the reduction of the catch per unit of effort level (CPUE) to keep the fishery within acceptable bioeconomic margins of a maximum sustainable yield (Ys). This can only be achieved through the adjustment of the fleet size from 481 vessels down to 250 or 275.

Marine fisheries of Karnataka State, India

This contribution provides an overview of the marine capture fisheries off the coast of Karnataka State, India. It covers the main fisheries and fishing gears, production trends (by main species /groups and gears), assessment results and fisheries management. Marine fisheries production in the State increased from about 57,000 t/year during the 1950s to a peak of about 250,000 in 1989, declining to about 150,000 t/year by 1995. Substantive changes have been noted in dominant gears and species groups contributing to the catch between 1980-84 and 1990-95. Results of assessments indicate that many commercially important stocks are overfished, thus requiring a reduction in fishing effort.

An approach to the assessment of the finfish fisheries of the Caribbean Community

This paper briefly outlines the implications of making a decision on the most appropriate alternative for carrying out stock assessments and the reasons for previous failures to conserve finfish stocks for sustainable use. The Mathews (1987) approach utilizing Age-Length Catch-Effort Keys (ALCEK) is briefly reviewed, and a suggested overall approach for the assessment of the finfish resources of the Caribbean community is outlined. With recent initiatives towards use of the precautionary approach and reference points, Carribean community countries are advised to revisit the question of the models to be utilized for the assessment of their fish stocks, paying due attention to the quantity, quality and applicability of data now being collected.

Rebuilding coastal fisheries livelihoods after the Tsunami: key lessons from past experience

Fishing communities around the Indian Ocean were severely affected by the December 2004 tsunamis. Programs for rebuilding coastal fisheries livelihoods need to address the pre-tsunami situation that was characterized by overfishing and degraded natural resources. Adopting appropriate strategies to ensure sustainable livelihoods will require community involvement, as well as cross-sectoral, integrated planning and management at ascending government levels. Key recommendations from the WorldFish Center study Sustainable Management of Coastal Fish Stocks in Asia are presented to encourage discussion and debate.

The Marine Stewardship Council: new hope for marine fisheries

To help reverse the downward trends for the world's marine fish stocks, the Worldwide Fund for Nature (WWF) and the Aglo-Dutch Unilever have jointly formed the Marine Stewardship Council (MSC), an independent, non-profit, non-governmental membership body. The rationale and strategies to achieve the goals of the joint effort are discussed.