NIFS announced that it set out research on the changes in habitat environment around Deungryangman Bay and Yeojaman Bay (Jeollanam-do) in order to uncover the causes of continuous reduction in the yield of Scapharca subcrenata, leading to the establishment of stable production bases.

*Annual Scapharca subcrenata yields: 8,995 tons  in 2019, 6,177 tons in 2022, and 4,456 tons in 2024 

The two bays are critical production sites of S. subcrenata, accounting for 85% of national production. Last year, however, Deungryangman Bay struggled to collect the species on account of increasing emergence of Musculista senhousia* larva, which is a major competitor species against S. subcrenata.

* Musculista senhousia is a small mussel with a maximum length of around 30mm. It is a species with rapid growth and high adaptability in various environmental changes, having negative impacts on coastal ecosystem. 

Over the past 15 years from 2010-2024, NIFS had analyzed data on monitoring of fishing ground environment. The result showed the changing habitat environment that annual bottom water temperature in the two bays increased by 1.8℃-2.1℃ in 2024 compared to 2010, and was 2.0℃-2.1℃ higher in 2024 compared to the 15-year average bottom water temperature. The Chemical Oxygen Demand (COD)* also increased 1.6-2.5 fold in 2024 compared to 2010.

*COD helps determine the level of pollution in water by indicating the amount of organic and inorganic substances present. Higher COD indicates greater pollution of severe eutrophication and organic accumulation. 

Under circumstances like this, NIFS is going to draw up measures to reduce competitor species by clarifying habitat change patterns and the reason for M. senhousia to become dominant species. In Yeojaman Bay experiencing the occurrence of M. senhousia mass mortality events, in parallel, NIFS will also conduct research on calculating the optimal capacity of aquaculture farms with a comprehensive study into habitat environment, growth rate and the physiological characteristics of S. subcrenata.