Age and growth of the white-spotted conger eel, Conger myriaster (Brevoort) in the Southern sea of Korea

Abstract

The present study is to provide a better understanding of the age and growth of the white-spotted conger eel, Conger myriaster in the Southern sea of Korea. This study has been investigated about age, growth and reproductive traits of the white-spotted conger eel. Samples were collected by trap, shrimp trawl and bottom trawl from April 2009 to November 2011 from the Southern areas and the coastal water in Geoje Island. Age validation is observed by UV light and the relative growth is estimated based on the total length, weight and otolith readings. This is a detailed report clarifying the accuracy of the age determination by using a UV light observation. In addition, the age structure is estimated by defining the relationship between otoliths measurements and age. The age of 212 otoliths ranged from 1 to 13 years. The age composition of congers in coastal water of Geoje Island is turned out to be dominant from 1 to 3 years old while that in offshore of southern sea ranged from 3 to 13 years old. Conger eel showed a wide variation of total length in the same age composition. The parameters of von Bertalanffy growth function were estimated from three-methods by non-linear regression: back-calculation method, mean total length at age and otolith weight at age. The results of adjusted coefficient of determination nearly matched with estimated values for the three methods (r2>0.97). The best fitted result was estimated as following VBGF parameters; L∞=127.95 cm, K=0.102, t0=-0.922. Maximum oocyte diameter ranged from 50 to 430 ㎛. Reproductive traits of ovaries showed positive relationship between GSI and MOD in the regression of power function. It is suggested that oogenesis begins to develop from 4 years old at 45cm TL.