2021 Volume 26 Issue 2 Pages 1-12
Since the 1990s, the harvest of Manila clams Ruditapes philippinarum has decreased in one of the main fisheries areas on the eastern coast of Ise Bay. Furthermore, there were less than 400 tons in 2014, and it has decreased to 1 ton or less after 2016, which is similar to the successive tendency for the decrease harvests nationwide. Various factors have been considered about the nationwide decrease of Manila clams, but the causative factors remain to be verified. Recently in Ise Bay, the analysis using the individual growth model revealed the association of the decrease of Manila clams and a drop in the quantity of phytoplankton. However, the conclusions may have been influenced by the characteristics of the models that were used. Therefore, using three different individual growth models, I examined the reproducibility of the models as an index for the growth and mortality of Manila clam on the Kosugaya tidal flat, eastern coast of Ise Bay. As a result, the Shiba model and DEB model were able to reproduce the growth and mortality in the parameters based on the published papers. On the other hand, the Turushima model was able to reproduce the growth and mortality by resetting the parameter level with values determined from field observations. It was shown that the growth model is an effective tool to analyze the relation between the reduction in stock resource of Manila clam and the food environment in Ise Bay.
