Effects of rotational fishing on enhancement of fish stocks in mountain streams

Abstract

  Rotational fishing in mountain streams is a potential inland fisheries management practice for the sustainable exploitation of natural stocks. To evaluate the effects of rotational fishing on enhancement of white-spotted charr and masu salmon stocks, we investigated changes in the abundances of these fishes in two streams where this management practice was applied. Generalized linear mixed models showed that the density of catchable-size (>150 mm) of both species increased during two closed years and three closed years in one stream. In another stream, the density of catchable-size charr did not increase during two closed years. The density of new recruits (≤150 mm) of either species did not increase in either stream, probably because of the effects of environmental fluctuations and time lags for population increase. Our data indicate that the effects of rotational fishing in mountain streams on enhancement of fish stocks differ among streams and fish sizes. Because the short-term closures investigated here resulted in only small increases in population (1-2 individuals/100 m²), stocks may decline rapidly under high fishing pressure during open periods. Accordingly, additional harvest regulations may need to be implemented during open years to sustain the increased abundance resulting from rotational fishing.