Year-Class Strength of the Ocellate Puffer around a Spawning Area in the Inland Sea of Japan

Abstract

This paper describes the characteristics of yearly fluctuations in the landings of the ocellate puffer Takifugu rubripes which migrates from the open sea into a spawning area in the Inland Sea of Japan. The authors analyze landing statistics by three fisheries, namely line, surrounding seine, and setnet fisheries around the spawning ground, and obtain the following results. The abundance of the ocellate puffer around the spawning area corresponds directly to its landing by the setnet fishery there. On the other hand, landings of the ocellate puffer seem to fluctuate mainly according to the fishing effort rather than to its abundance in the line and surrounding seine fisheries. Thus, using landings by setnet fishery as an abundance index, year-class strength is estimated with age compositions of landings by setnet fishery for the ocellate puffer population around the spawning ground. Consequently, the age at full recruitment is found to be 3 years old. The landing of some large year-classes decline at a virtually constant rate with age after full recruitment. This suggests that the same year-classes migrate into the spawning ground in subsequent years. Thus, it follows that good landings result chiefly from dominant year-classes, e.g. the year classes of 1983 and 1986, in the population. © 1993, The Japanese Society of Fisheries Science. All rights reserved.