Ecology and abundance of conger eel Conger myriaster in Shijiki Bay, Hirado Island.

Abstract

In order to clarify the ecology and abundance of conger eel, as a part of the study on the decreasing process for 0-age red sea hream, a sampling survey using pots was carried out in Shijiki Bay (Nagasaki Prefecture)from 1980 to 1983. Using 758 pairs of pots (one-day immersion), 1741 conger eels (TL 250-834mm) were caught. The catch in number reached its peak in June, dropping toward autumn to winter. The conger eels were densely distributed but smaller in length at the inner part of the bay. The sex ratio was 857:9 in total, indicating an overwhelming dominance of the female. The stomach contents of the pot-caught conger eels were composed mainly of sardines used as bait. The average stock number of the conger eel in this bay during June-July in 4 years'survey period was calculated at 17, 500 (11, 600-23, 200). 0-age red sea breams preyed on by the conger eels have been estimated at 2000 (650-7200) per day on average.