Synchronous fluctuation of marine benthic resources in Ise-Mikawa and Tokyo Bays, two major enclosed bays in central Japan

Abstract

We compared the long-term fluctuations in fisheries catch of benthic marine resources between two typical enclosed bays, Ise-Mikawa and Tokyo Bays, which face the Pacific Ocean in central Japan. The catch of the Manila clam Ruditapes philippinarum has decreased since the 1970s, when artificial reclamation was massively conducted in both bays. However, the Manila clam catch in Mikawa Bay has increased since the 2000s with improvement in reproductive network due to transplant release of juvenile clams by local fisherman. The fluctuation in the catch of five of eight major species of small bottom trawl fisheries target positively correlated between Ise and Tokyo Bays despite the considerable distance separating the bays. The catches of flounder (Pleuronctidae), Japanese tiger prawn, Marsupenaeus japonicus, and mantis shrimp, Oratosquilla oratoria, have decreased, whereas those of Japanese temperate bass, Lateolabrax japonicus, and cuttle squid, Sepia esculenta, increased in synchrony. Fluctuations in major water quality parameters such as temperature, nutrients, and dissolved oxygen concentration were similar in both bays. These changes in the environment of both bays and climate will affect the drastic and synchronous fluctuations in benthic marine resources among these two separate enclosed bays.