Journal of the Marine Biological Association of India

Length-weight relationships and size at first maturity of four commonly landed elasmobranchs in Malvan, Maharashtra

Volume 65 Issue 2

H. Eswaran, D. Satarkar, S. Kottillil, K. Shanker and T. Gupta

10.6024/jmbai.2023.65.2.2433-09

Abstract

Elasmobranchs are amongst the most threatened faunal groups globally, with fishing being the key contributor to their decline. Given the varied life histories of elasmobranchs, sustainable fisheries management requires detailed investigation with fishery and species-specific strategies. The present study aimed to explore the life-history traits, specifically length-weight (L-W) relationships and size at first maturity (L50), of the commonly landed and commercially important sharks and rays off the coast of Malvan, western India. These included Scoliodon laticaudus, Chiloscyllium griseum, Chiloscyllium arabicum and Brevitrygon walga. The L-W relationship was estimated using linear regression and analysis of covariance (ANCOVA), while Student’s t-test was carried out to test for isometry. L50 was determined by fitting a logistic regression to the proportion of mature individuals and the body length. ANCOVA showed no significant difference between the sexes; therefore, male and female specimens were pooled to obtain a single equation. L-W relationships for S. laticaudus, C. griseum, C. arabicum and B. walga were as follows: 0.003820L2.97, 0.00398L2.95, 0.001713L3.13 and 0.017489DW3.21. The shark species showed isometric growth, whereas B. walga showed positive allometric growth. L50 for males of S. laticaudus, C. arabicum and B. walga were 41.30 cm, 57.15 cm and 21.36 cm, respectively. L50 for females of C. arabicum and B. walga were found to be 58.32 cm and 19.00 cm, respectively. The data generated on the L-W relationship will contribute to our understanding of fish biology and physiology, while information about L50 of the elasmobranch landings can be utilised for tracking the health of the population and estimating minimum legal size (MLS) for developing fisheries-specific interventions in the study region.

Keywords

Chondrichthyans, life-history traits, maturity, threats, reproductive biology

Date : 20-11-2023