Retrospective evaluation of datalimited fisheries

Authors: William WL Cheung Yvonne Sadovy

Publish Date: 2005/03/30

Volume: 14, Issue: 2, Pages: 181-206

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Abstract

This study reconstructs the likely historical changes of the datalimited Hong Kong’s inshore fisheries and evaluates their probable effects on the marine ecosystem based on multiple information sources Local knowledge on changes in the fisheries and the marine ecosystem is collected from commercial fishers recreational divers and fishery officials We combine this knowledge with results from simulation modelling and information from published and unpublished literature and reports to generate hypotheses on the historical changes in the fisheries and ecosystem between 1950 and 2000 The analyses suggest that traditionally targeted fishes had already been overexploited by the 1970s following a rapid drop in catch per unit effort in the 1960s This paralleled a dramatic expansion of fishing effort Ecosystem structure shifted as the large predatory species became depleted and small fishes and benthic invertebrates gained dominance High demand for small fishes as fishfeed for aquaculture farms high market price of benthic knowledge from resource users and managers provided an important sometimes the sole source of information to understand the fishery Johannes 1998 Johannes et al 2000 In this study we demonstrated that the use of the best available information obtained from limited landings and effort statistics expert knowledge from resource users and managers andÆresults from simulation modelling provided informative qualitative and to a certain degree quantitative descriptions of fishery development contributing to an understanding of fishery history and identification of management challenges Caution is urged since the approach is based heavily on a number of assumptions that need to be carefully validated We assumed that the interviews provided an unbiased description of the changes in fisheries and the marine ecosystem However psychological studies have suggested that autobiographic memory memory that is specific personal and longlasting and usually of significance to the selfsystem eg Thompson et al 1996 – could be biased as a result of affective association For instance study on university students’ abilities to recall the grades they obtained in various subjects during high schools generally showed that memory was best for experiences that were affectively pleasant intermediate for experiences that are unpleasant and worst for experiences that are neutral Koch 1930 Waters and Leeper 1936 Thompson 1985 Bahrick et al 1996 Moreover the ability to recall autobiographical memory was shown to decline with age particularly when the events occurred in the distant past Pascale et al 2002 The interviewees’ memories on past marine resource abundance were generally autobiographic memory and might have affectively associated the past with the most productive years of their fishing experience Thus the description of the past they provided might be positively biased Information and descriptions from other independent sources help to assess the validity of the interview data and in the present study information from different sources seemed to converge However future studies on autographic memory of fishers’ fishing experience could enhance the validity of the approach The approach described in this paper is useful in retrospective analysis and diagnosis of a fishery in a datasparse condition However more conventional fishery data and analytical tools may be required for finetuning future management and there is little substitute for regular fishery monitoring

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