Age and growth of the Blackthroat seaperch, Doederleinia berycoides (Hilgendorf, 1879) in the Southern Sea of Korea

Abstract

The age and growth of the blackthroat seaperch were estimated using otolith analysis. Monthly samples were collected from January to December, 2014 by using large and middle single trawl nets from the Southern Sea of Korea. The monthly changes in gonadosomatic index (GSI) revealed that spawning occurred between July to September with a peak spawning period in August. The monthly catch data from 2012-2017 showed that monthly fishing density increased in spawning season. The length-weight relationship (LWR) for both sexes were significant (p<0.05) with the coefficient of determination (r2) 0.95 (female) and 0.89 (male). The relative growth co-efficient (b) was positive allometric, where 3.1909 for female and 3.0714 for male which revealed that growth in weight was faster than growth in length for both sexes. The marginal increment index (MI) was the lowest in September which indicated that otolith growth ring was formed in September in each year. Fish age was estimated from otolith growth rings analysis and this study estimated the maximum age for females were 6 years, where males were 5 years. The relationship between otolith radius (R) and total length (L) was expressed as L = -10.325+11.881R for females and L = -6.541+9.9049R for males. From this relationship, total length were back-calculated for both sexes. The von Bertalanffy growth functions were expressed in the form of equation Lt = 39.8848(1-e-0.2024(t+0.8726)) for female, Lt = 29.2984(1-e-0.3245(t+0.7804)) for male and Lt = 41.6011(1-e-0.1878(t+0.9910)) for both sexes, where Lt is the length at age t.