Spawning habitat suitability maps for the conservation of the tri‐spine horseshoe crab Tachypleus tridentatus in Tsuyazaki Cove, Fukuoka, Japan

Abstract

Abstract The suitable spawning habitat of Tachypleus tridentatus was estimated and mapped for the first time using scientific modelling in Tsuyazaki, Fukuoka, Japan. A total of 43 nests were found at five sites from 2018 to 2019. Of these 43 nests, the location information of nine nests at one of the sites was used as ‘Training data’ for constructing the models. A series of procedures was employed to determine the relationship between the biological data and their physical parameters to estimate the suitable spawning habitat. First, the contribution rates of the physical parameters (beach elevation, slope and sediment) to nest locations were evaluated. Second, physical parameters that showed significant contribution rates were chosen to estimate suitable spawning habitats. It was found that the beach elevation was the most significant parameter for estimating suitable spawning habitats. Mean high water neap to mean higher high water was estimated as suitable spawning habitat, and 74% of the nests were fitted in an area assessed as suitable. The result was consistent with previous studies. The area of suitable spawning habitat was estimated to be only 476 m2 out of 1943 m2, comprising 24% of the sandy beach in the study site. Therefore, it was concluded that the conservation and restoration of spawning grounds is a high‐priority and urgent issue at the site. It is proposed that scientific modelling of nest/egg occurrence and beach elevation can effectively determine suitable spawning habitats. Thus, it is possible to quickly establish the habitat most suitable for spawning in coastal environments and help plan conservation strategies for this globally endangered species.