Sediment preference of coastal horseshoe crab (Tachypleus gigas) in an artificial spawning ground

Abstract

Context Spawning beaches are important for coastal horseshoe crabs, Tachypleus gigas (Müller, 1785), to sustain their population. Over time, T. gigas natural spawning area has gradually diminished owing to human and natural causes. T. gigas is being artificially bred in captivity to enhance its population. Aims The study aims to determine the T. gigas spawning preference for three different sediment sizes. Methods Spawning experiments were carried out in an indoor concrete tank representing an artificial spawning ground, consisting of three combinations of sediment sizes: coarse, medium and fine. The spawning of 45 pairs of T. gigas samples was observed within 3 h, the nests were marked and excavated on the next day. The number of eggs per nest was counted individually after being cleaned. Key results The 45 pairs of T. gigas produced 27,266–30,859 eggs. Among these, on the basis of the number of nests produced, T. gigas prefers to spawn in medium to coarse sediment with a particle-size range of 0.25–1.00 mm. Conclusions Our findings indicated that medium to coarse sediments are optimal for T. gigas spawning in artificial spawning grounds, because they could produce a high number of nests and eggs, increasing the number of juveniles released. Implications These results could be used as a baseline for the conservation management of T. gigas in captivity.