Stock Structure Analysis of Declining Shovel Nosed Lobster Thenus Unimaculatus (Burton and Davie, 2007)for Effective Management and Conservation Along the Indian Coast

Abstract Thenusunimaculatus (Burton and Davie 2007)is one of the most important commercially exploited lobster species in India distributed throughout the coast. The declining trends and collapse of the sand lobster fishery has been reported from the northwest coast of India. A number of hypotheses have been proposed to explain the decline, but a lack of basic information on population demographics inhibits hypothesis testing. In this study, morphometric stock structure analysis of Thenusunimaculatus was attempted to discriminate the spawning population collected from five locations (673 specimens) during 2017-2019 along the Indian coast. Data was subjected to allometric transformation to remove size effect. The transformed data was subjected to multivariate analysis, such as Principal Component Analysis (PCA) followed by linear discriminant analysis (LDA) using R software. The first eight PCs cumulatively explained 73.97% of the total variance,wherein the first two PCs together explained 45.50% of the total variance. The accuracy (ACC) and misclassification rate (MR) of the linear discriminant analysis (LDA) model performed to optimize separation among different sampling locations were 0.70 and 0.30, respectively, which indicates clear overlapping of the stocks among different sampling locations.The accuracy (ACC) and misclassification rate (MR) of the linear LDA model developed to discriminatebetween the coasts were 0.74 and 0.26,respectively, indicating no apparent differentiation in the samples between the coasts. The results of this study revealed the presence of asingle spawning stock of shovel nosed lobster, T. unimaculatus along the Indian coast.The information will aid in the development of better holistic management strategy for the conservation of this declining resource.