The Availability and Information Content of Fisheries Data
The availability of catch, age/size composition, effort, tagging, and survey data of various sorts is summarized according to the state of development and economic importance of the fishery. Fairly complete catch weight data are usually a prerequisite for any meaningful assessment or management. Data of all these types are available only in very rare cases, and even then the assessment of the stock may be ambiguous.
The information content of each type of data is reviewed. This is most often of a relative nature (e.g., current stock size relative to previous values). Absolute values can usually only be obtained by relatively complex analysis of several sorts of data simultaneously. Current absolute stock size in particular requires expensive data to be collected, and even then is difficult to determine.
The need for such information is, however, dependent on the type of management envisaged. Short-term status quo management can be carried out quite successfully, even without knowing absolute stock size at all accurately. Determination of appropriate long-term management strategies, however, requires much more information (especially of absolute stock sizes and the factors determining recruitment) which is difficult to obtain. Attempts to determine rational long-term management strategies in detail are therefore likely to be worthwhile only for stocks of major economic significance.
KeywordsNatural Mortality Fishing Mortality Catch Rate Target Strength Stock Size
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