Fin-Clipping法による養鰻池のウナギ総数の推定について

概要

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The number of eel, Anguilla japonica in a culture pond (about 1 acre) was estimated by PETERSEN mark-and-recapture method, and the estimates which were obtained from the first set of data and that of the first and second sets of data, treated as a whole, were compared with the actual number of eel captured after the draining of the pond. The results indicated that the estimates were fairly greater than the actual number of fish and the source of error was mainly attributable to misjudging some of the marked fish for those that were unmarked, which is caused by the rapid regeneration of the clipped fin in some of the marked fish. The correction equation for p, marked ratio in samples, was derived as follows, p=p'-ε1/1-ε1-ε2 and V( ?? )=(p'-ε2)(1-p'-ε1)/n(1-ε1-ε2)2 where p' is the apparant marked ratio in samples, p is the marked ratio in samples when there is no misjudgement, ε1 is the rate of misjudging the marked as the unmarked, ε2 is the rate of misjudging the unmarked as the marked, which is caused by deformity of the fin, and n is the size of samples. In the present experiment, ε2 was negleted and ε1 was about 0.2. The recalculation, using the above equation, showed the new estimates were both in conformity to the actual mumber of fish.
社団法人日本水産学会の論文