Consideration of the equivalent estimation of the fishing pressure on glass eels and adult eels of Japanese eel Anguilla japonica

Abstract

In order to implement the rational stock management of Japanese eel Anguilla japonica, it is important to evaluate the fishing pressure (FP) on Japanese eel stocks by adult eel catch and glass eel catch equally. I accordingly developed a FP evaluation method that compares FP by adult eel catch with that by glass eel catch in the same dimension. I succeeded to clarify the historical changes of the relative relationship of both FPs by using it. According to this method, FP by 1 t of adult eel catch is equivalent to 16.4–120.0 kg of glass eel catch, and FP by adult eel catch continued to be stronger than that by glass eel catch until around the 1970s. However, FP by glass eel catch came to be dominant thereafter. In addition to the above, taking into account the estimation and comparison of both FPs, I considered the historical change of the stock level and the rational management measures for the current status of Japanese eel stocks.