1Kyoto Institute of Oceanic and Fishery Science, Miyazu, Kyoto 626-0052, 2Graduate School of Agriculture, Kinki University, Nakamachi 3327-204, Nara 631-8505, Japan
In order to estimate the mortality coefficients of flathead flounder Hippoglossoides dubius in the western Sea of Japan, a total of 2,928 tagged ones were released in the waters off Kyoto Prefecture in April 1994, 1995, 1996 and 1997. Using the maximum likelihood method with the recoveries every 1-fishing year term after released in each tagged group, total mortality coefficient was estimated to be 0.596 year-1 for 1994, 1996 tagged groups, and 0.455, 0.835 year-1 for 1995, 1997 tagged groups. Assuming appropriate values of survival rate just after release and rate of reporting of tag recoveries, ranges of fishing coefficient (Ft) and natural mortality coefficient (Xt) for tagged groups were estimated to be 0.159-0.393 year-1 and 0.236-0.449 year-1, respectively. It was suggested that high values of dispersion diminishing coefficient are contained in Xt.