Occurrence and Morphometric Analysis of Horseshoe Crabs Along Bhadrak Coast of Odisha, India

As a marine arthropod, horseshoe crab has persisted for more than 200 million years and is still enjoying its life on earth without much morphological modifications. Out of the four extant species, two species, namely Tachypleus gigas (Müller 1785) and Carcinoscorpius rotundicauda (Latreille 1802), are found along the northeast coast of Bay of Bengal, India. The occurrence, distribution, morphometric characteristics including total body length (TBL), length of telson (TEL), prosoma width (PW) and opisthosoma width (OW), and breeding grounds of T. gigas and C. rotundicauda were studied along the Bhadrak coast of Odisha using standard procedures. A total of 152 individuals of T. gigas and 117 individuals of C. rotundicauda were collected from four sites at Chandanipal Creek, Dosinga Creek, Udabali Island and Chudamani Ghat along the Bhadrak coast of Odisha every fortnight from February to August 2017. Of all these specimens, dead individuals accounted for 80.3%. The average body length of female and male T. gigas was 36.5 ± 3.5 cm and 30.2 ± 3.3 cm respectively, whereas the average body length of female C. rotundicauda was 34.6 ± 4.6 cm and that of the male was 29.4 ± 2.1 cm. A positive correlation (p < 0.05) was observed between TBL with TEL, PW, and OW for both sexes of these two species. The co-existence of T. gigas and C. rotundicauda is a unique feature of this region. Threats from fishing nets, motorboats, and trawlers might be the important factors responsible for the population decline of horseshoe crabs. As horseshoe crabs have ecological, commercial, and biomedical importance, necessary steps are highly warranted for their conservation.