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Environmental impacts on fishery resources

The growing awareness of the linkages between sustainable fishery development and sustainable environment in the region has been reflected by the emergence of various environmental measures such as the introduction of environmental impact assessment (EIA), development of criteria for water quality standards, fish product standards, etc., to mitigate the problems. For example, increased awareness of the impact of shrimp culture on the aquatic environment in some countries has stimulated the authorities to discourage further destruction of mangroves for shrimp culture and limiting the number of farms was also being considered. Legal measures have been introduced in many countries in the region. However, lack of effective monitoring and enforcement of these laws and regulations remain a common problem.

Both fishing and natural environmental variability can affect the abundance of fish and the long-term sustainable yield. Climate effects often interact with effects of fishing such that in times of poor environmental conditions the probability of collapse of fish stocks are greater because they have been fished down to levels too low to be able to buffer the environmental effects. Separating the effects of climate from the effects of fishing still remains one of the major challenges of modern fisheries science.

Natural changes in the environment are often cyclical in nature and can occur on short time scales (such as one or two years in a penaeid shrimp fishery), or on longer decadal time scales, as has been observed for many small pelagic fish stocks. Even longer time scales involving response to global warming and other long-term climatic phenomena are occurring but are difficult to detect. In order to understand the impact of fishing on fish stocks, this underlying variability also has to be understood and considered in making management decisions.

There is considerable uncertainty and debate on the extent of climate change over the long-term and the changes in sea level rise, rainfall patterns, temperature and water current changes resulting from it. It is, therefore, difficult to make a detailed quantitative regional synopsis on its impact. It is possible, however, to make qualitative predictions of the likely direction of these changes and their impacts on critical habitats (e.g. mangroves, reefs) and the consequent impacts on fishery productivity.

There is tremendous uncertainty in the effects and risks that climate change poses to fisheries. This results from having a limited information base, limited monitoring networks, and insufficient information exchange and analysis at both the national and regional levels. Emphasis should be placed on improving instrumentation and monitoring as well as reducing the human causative factors driving the climate change.

On the other hand, the impacts of fishing may be viewed in terms of effects on the resources (both on targeted and non-targeted species) and the effects on the aquatic environment which sustains them (including but not exclusive to coral reefs, seagrass/algal beds). The key impacts of fishing in the region are: (1) overfishing in coastal areas; (2) bycatch/discards; (3) habitat degradation; (4) use of destructive fishing methods; (5) impact on “protected” species; and (6) “ghost” fishing.

Several activities other than fishing were identified as impacting the marine and coastal environment. These activities include mining, agriculture, shipping, tourism, industrial development, forestry, urban development, waste dumping, reclamation and dam construction. These activities result in several forms of habitat degradation including damage to coral reefs and seagrass beds through sedimentation, pollution and waste disposal, and degradation of water quality.

The promotion of healthy aquatic ecosystems is fundamental for sustainable fisheries and aquaculture development. The setting of goals and standards for defining a healthy ecosystem, promoting awareness of the issues through participation and coordination of the various areas and users that impact on the marine and coastal environment and ensuring that appropriate monitoring is in place, to determine trends in the state of the environment are all important components in addressing the issues.

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