This thesis focuses on the implications of exploitation pattern (population selectivity) and population resilience for fisheries sustainability in the NE Atlantic. Novel metrics of exploitation pattern and resilience are introduced and the effects of juvenile protection and resilience erosion on stock size, structure and yields are investigated. Analysis of both empirical and simulated data suggested that high selection of juveniles negatively affects both stock size and yield. A meta-analysis of empirical data for 38 fish stocks showed that fishing mortality of juveniles exceeding half that of mature fish leads to overfishing. Simulation-based analysis illustrated that a mean age-at-capture more than two years higher than mean age-at-maturity secures high yields at low levels of stock depletion. The effects of exploitation pattern on stock status are weaker than those of exploitation rate when empirical data are considered, both at an individual-stock and a cross-stock scale. However, simulation-based analysis revealed that for higher levels of juvenile protection than the ones observed in most empirical stocks, exploitation pattern would be more influential than exploitation rate. These findings suggest that there is a high unfulfilled potential to promote sustainability by protecting juveniles. Besides exploitation pattern, population resilience is another factor whose role in fish population dynamics was examined here. A resilience assessment of Barents Sea cod was carried out using a novel integrated approach combining multivariate analysis and bifurcation theory. This way, the occurrence of a population state shift in 1981, associated with climatic and exploitation effects, was identified. The approach implemented in this resilience assessment is reproducible to any other data-rich population and can be also used at the community- and ecosystem-levels to explain and predict state shifts. As Europe is currently moving towards a more holistic approach in fisheries management through the reform of the Common Fisheries Policy, such quantification and investigation of stock/exploitation attributes beyond stock size and exploitation rate is of great importance.

Thesis (Ph.D.)--University of Tasmania, 2004. / For consultation only. No copying permitted until 13-3-2006. Includes bibliographical references.

Thesis (Ph.D.) -- Australian National University, 2007.

Thesis (Ph.D.)--Memorial University of Newfoundland, 2004. / Bibliography: leaves 194-207.

Coral trout, Plectropomus Ieopardus, is a high-volume, high-priced species in the international live reef food fish trade. Each year more than 8,000 tonnes of fish, worth over a billion Hong Kong dollars, are exported from the Philippines, Indonesia, Malaysia and Australia for consumption in Hong Kong and Mainland China. Its wild populations are believed to be declining in all major source countries with the exception of Australia which manages its fisheries. Concerns over the sustainability of coral trout fisheries, which are major livelihood for some coastal communities, have been raised. To assess whether the fisheries are biologically sustainable, this study developed two different stock assessments synthesizing the best available scientific knowledge and fisheries data of coral trout or grouper stocks for two major sources of production. For the coral trout fishery in the Municipality of Taytay in the Province of Palawan, Philippines, only stock life-history was available in literature, while for Indonesia only catch and effort data were provided for 11 major fishing grounds for groupers including coral trout, by a major live fish trader. Given the nature of the data available, two types of fisheries models were developed for the assessments. For Taytay, a per-recruit model was constructed to simulate catch and stock response to a range of fishing levels based on life-history processes. With the current fishing level estimated from sampled catch, the model indicated that the fishery was unsustainable in Taytay because the spawning stock was overexploited. Right-based catch control, export quota, minimum size, spawning season and aggregation closures were proposed for the recovery of spawning and the spawning stock. Studying stock abundance, sex change and uses of the fish other than export, for example domestic use and mortality levels, will improve the assessment rigour. For Indonesia, a mult-grouper species per-area-based Fox model was fitted to recent catch and effort data. The assessment determined catch and trade quotas for management and highlighted the need for rights-based adaptive management. The assessment found on fishing ground where the groupers including coral trout were fished much beyond sustainable levels and suggested immediate reduction of catch and number of fishers. Monitoring catch, effort and stock abundance and understanding larval dispersal and recruitment can help verify model assumptions and improve their accuracy. For the great many data-poor, unassessed grouper fisheries, similar assessments can be carried out gather data and evaluate fisheries sustainability, while management measures derived from the two assessments here could be used to inform management until more data and assessments become available. Data gaps for improvement of models were identified in the study. Both assessments in this study viewed community-based management as essential to resolve the weak enforcement capacity of Southeast Asian states in fisheries management. For management in and by communities lacking expertise and resource, a greater synergy between various parties is critical, which includes institutional legitimacy of community’s property rights, outreach and capacity building by NGOs, compliance of traders with regulations, sustainable trade practices as well as financial support from consumer’s choices and philanthropy. / published_or_final_version / Biological Sciences / Master / Master of Philosophy

By dealing with aspects of coastal aquaculture and resources management, an analysis is herein presented at the macro-scale using GIS techniques for the coastal zone of Tabasco state, and at the micro-scale with the description of the characteristics of a coastal community located in the Mecoacan estuary. Transfer of appropriate aquaculture technologies and introduction of sustainable farming systems are major challenges. The total area identified for aquaculture development through the GIS modelling accounted for 23 462 ha, 80% of which were located in the Centla Biosphere Reserve (Centla and Macuspana). The suitable area identified through the multi-criteria evaluation provided a structure in which requirements for aquaculture development could be met. An analysis of the fanning systems in the Mecoacan estuary was carried out to understand local attitudes, capabilities and processes and evaluate whether the potential identified by the GIS modelling can be realised. The results from participatory assessments showed that conditions within Mecoacan cooperatives have deteriorated and increasing interest in restructuring the organisations is regarded as a means of integrating employment and income generation alternatives such as aquaculture practices, to support and improve current levels of fisheries production, and to achieve gains in market development. The analysis of the economics of Mecoacan fishermen suggests that rural problems have not yet been engaged in progressive policies. It seems that previous forms of governance have been maintained to shore up power instead of laying the groundwork for viable rural production, as it is clear that some fishermen are competitive while others are not, regardless of whether or not they are associated in cooperatives. The large-scale exploitation of resources, degradation of the environment and increased conflict over resources in coastal communities suggest the need of an integrated multi-sectoral approach. A strategy towards an integrated coastal management for Tabasco coastal zone is discussed, including those related to aquaculture development.

Thesis (M.M.S.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 62-65.

Thesis (M.Sc.) - University of Queensland, 2002. / Includes bibliographical references.

Thesis (M.A.)--Ohio University, June, 2008. / Title from PDF t.p. Includes bibliographical references.

Thesis (Ph. D.)--University of Tasmania, 2003. / Title from PDF title page (viewed on June 11, 2005). Includes bibliographical references (p. 373-393).