Fishing has become a major conservation threat to marine fishes. Effective conservation of threatened species requires timely identification of vulnerable species. However, evaluation of extinction risk using conventional methods is difficult for the majority of fish species because the population data normally required by such methods are unavailable. This paper presents a fuzzy expert system that integrates life history and ecological characteristics of marine fishes to estimate their intrinsic vulnerability to fishing. We extract heuristic rules (expressed in IF–THEN clauses) from published literature describing known relationships between biological characteristics and vulnerability. Input and output variables are defined by fuzzy sets which deal explicitly with the uncertainty associated with qualitative knowledge. Conclusions from different lines of evidence are combined through fuzzy inference and defuzzification processes. Our fuzzy system provides vulnerability estimates that correlate with observed declines more closely than previous methods, and has advantages in flexibility of input data requirements, in the explicit representation of uncertainty, and in the ease of incorporating new knowledge. This fuzzy expert system can be used as a decision support tool in fishery management and marine conservation planning.
Increasing evidence indicates that marine species may be placed under threat of local, and ultimately global, extinction by the direct or indirect effects of fishing (Pitcher, 1998; Roberts and Hawkins, 1999; Wolff, 2000; Reynolds et al., 2001; Dulvy et al., 2003). Commercially important species can be fished down to a vulnerable level because of their economic value, e.g., Chinese Bahaba (Bahaba taipingensis, Sciaenidae) (Sadovy and Cheung, 2003), Southern Bluefin tuna (Thunnus maccoyii, Scombridae) (Hayes, 1997). However, species with little or no commercial value are also not safe from the threats of fishing. Non-targeted species may be threatened through bycatch (e.g., common skate, Raja batis, Rajiidae, Brander, 1981; barndoor skate, Raja laevis, Rajiidae, Casey and Myers, 1998), or by fishing activities that create large disturbance and damages to benthic habitats (Jennings et al., 2001; Kaiser et al., 2002, 2003). Declines and extinctions can be associated with the loss of essential habitat critical to complete the life cycle of the species (McDowall, 1992; Watling and Norse, 1998). Given the overexploited status of most fishery resources in the world (Jackson et al., 2001; Pitcher, 2001a; Pauly et al., 2002; Hilborn et al., 2003), timely identification of species or populations that are vulnerable to local extinction (=extirpation) is urgently needed so that appropriate counter-measures can be formulated and implemented (Jennings et al., 1999a; Dulvy et al., 2004)
Publisher : ELSEVIER
By : William W.L. Cheung , Tony J. Pitcher, Daniel Pauly
File Information: English Language/ 15 Page / size: 202 KB
سال : 2005
ناشر : ELSEVIER
کاری از : William W.L. Cheung , Tony J. Pitcher, Daniel Pauly
اطلاعات فایل : زبان انگلیسی / 15 صفحه / حجم : KB 202
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