Maturity of Hairtail Varies with Latitude and Environment in the East China Sea

Abstract

Early maturity of economically important fish has become a global issue, which might affect the reproductive potential of fish stocks. We used the samples that were collected in a fisheries‐independent survey in the East China Sea annually around the end of August from 2002 to 2017 to investigate the maturation progress of female Hairtail Trichiurus japonicus in response to (1) spatial variation, (2) environmental variation, and (3) CPUE. The preliminary analysis indicated that the gonads of Hairtail in the southern area and the northern area began to develop at similar anal length (around 140–150 mm), but the development was faster in the southern area than in the northern area. The proportion of matured fish was significantly higher in the southern area than in the northern area in the group of fish with 170–210 mm anal length. Based on generalized additive models, we found that temperature and CPUE could affect the maturation schedules of female Hairtail in the East China Sea. The relationship between sea surface temperature and the probability of maturity was close to an s‐curve, while the stock density had an approximately negative effect on the degree of precocious puberty.