Age, growth, mortality, and yield‐per‐recruit of red spotted grouper Epinephelus akaara in the central Seto Inland Sea, Japan

Abstract

The red spotted grouper Epinephelus akaara is important for commercial and recreational fishing in the coastal waters of East Asia. In Japan, approximately 850,000 juveniles are released annually for stock enhancement, and the catch in several release areas has increased. Life-history traits are important for fisheries management and stocking programmers. The age, growth, and mortality of fish collected from the central Seto Inland Sea from June 2012 to November 2014 were examined using 1022 sectioned sagittal otoliths, and the yield-per-recruit (YPR) was calculated. The opaque zones in the otoliths were confirmed to be annuli, formed mainly between June and July. The oldest fish was 16 years old. The percentage of those between two and five years was approximately 80%, whereas that of more than ten years was only 0.6%.The five parameters von Bertalanffy growth equation was calculated as: TL t = 390 {1 − 0.23[(t − 3.78) 2 + 1] −1 }{1 − exp [−0.34 (t + 0.28)]}, where TL t is the total length (mm) at t (year). The total, natural, and fishing mortality rates were calculated to be 0.80, 0.24-0.31 and 0.49-0.56 year −1 , respectively. The YPR analysis indicated that the current fishing mortality rate (F current ) was higher than F 0.1 and F max , and that increasing the age at first capture is more effective than decreasing F for increasing the YPR. These results provide important information for fisheries management and the stocking of E. akaara.

Annual changes in ovarian development stages of farmed female red‐spotted grouper, Epinephelus akaara, and inducing sexual maturity using photoperiod manipulation

“…These findings indicate that the main spawning season of red‐spotted groupers living on the coast of Korea is from July to September, the summer season. In addition, according to a recent study by Yamamoto and Kobayashi (2017), it was reported that the spawning season of red‐spotted grouper caught in Sato Inland, Japan is from June to August. We conducted experiments using artificially cultured female red‐spotted groupers that were not collected in nature, and we investigated annual changes in the GSI and ovarian developmental phase in a fish farm environment.…”

Estimating fish mortality rates from catch curves: A plea for the abandonment of Ricker (1975)'s linear regression method

“…See, for instance, fig. 6 presented in Yamamoto and Katayama (2022) for an example of a severely righttruncated descending limb in which Z may rather be overestimated from using the LR method. Although Chapman and Robson (1960) have originally suggested such practice, Smith et al (2012) later recommended that no data truncation should be applied.…”

“…(2021), Anderson et al . (2022), Tsai and Huang (2022), Yamamoto and Katayama (2022), Andrade et al . (2023), He et al .…”