Ecological niche models for the assessment of site suitability of sea cucumbers and sea urchins in China.

In the present study, the maximum entropy model (MaxEnt) based on the data of sea surface temperature (SST) and published information was used to assess the site suitability for the aquaculture expansion of the sea cucumber Apostichopus japonicus and the sea urchin Strongylocentrotus intermedius in China. According to the current assessment, the coastal areas of Hebei province and Tianjin have great prospects for A. japonicus aquaculture, while is currently being underutilized. In the south, more than 94% of the coastal areas in Zhejiang, Fujian, and Guangdong provinces are suitable for the growth of A. japonicus for six months, especially the coastal areas of Lianjiang, Changle, Fuqing and Putian in Fujian province. The water temperatures in more than 94% of China's coastal areas are higher than 25 °C in July and August, which probably results in the mortality of S. intermedius in aquaculture. This clearly indicates that high water temperature is the bottleneck of S. intermedius aquaculture and well explains the limited expansion of this commercially important exotic species since the introduction in 1989. We suggest a new aquaculture model of S. intermedius that extends the seed production to November to avoid the mass mortality in summer. In the south, 64% of coastal areas in Zhejiang and Fujian provinces are suitable for the transplantation of S. intermedius to the south. The present study suggests the ecological niche model MaxEnt based on the data of SST and published information as a new tool for the assessment of the site suitability of sea cucumbers and sea urchins in China. This provides new insights into the aquaculture expansion of native and exotic species.