Projected changes in the potential habitat distribution of Japanese anchovy (Engraulis japonica) in Korean waters from a maximum entropy model

Abstract

Due to global warming, changes in distributions of marine organisms have been observed, particularly small pelagic fishes known as sensitive to habitat changes, such as Japanese anchovy (Engraulis japonica) – the most important fish commercially and ecologically. To understand future changes in the habitat distribution of the anchovy in Korean waters, we established monthly maximum entropy model (MaxEnt) – a widely-used species distribution model that requires only presence data, by using the catch points and the five environmental variables (temperature, salinity, velocity, and chlorophyll-a concentration at the surface and mixed layer depth) during 2000-2015. We then applied the MaxEnt to project the habitat distribution for next three decades under three different representative concentration pathways (RCP 2.6, RCP 4.5, and RCP 8.5), focusing on seasonal differences in the habitat changes. The MaxEnt showed that temperature and salinity are the most important environmental variables affecting the anchovy distribution in winter, spring, and summer, while chlorophyll-a concentration is the most considerable variable in autumn. The future changes in highly suitable areas increase in winter and spring, while decrease in summer and autumn: area higher than the tenth percentile training presence, as a suitability threshold projected to increase the most 264% in March and decrease the most 11% in July for RCP 8.5 in the 2050s. In summary, summer and autumn when the habitat changes less-suitable include the main spawning periods of the anchovy, so it is expected that it may cause a decrease in the anchovy biomass and catch in Korean waters in the future.