Morphometry, length-weight relationships and condition index of Parreysia favidens (Benson, 1862) (Bivalvia: Unionidae) from river Seeta in the Western Ghats, India

Abstract

Allometry and condition index of the freshwater mussel Parreysia favidens (Benson, 1862) inhabiting the west flowing river Seeta at Seetanadi in the Western Ghats, India was studied between April 2005 and May 2006. Monthly sampling was carried out and a total of 2728 bivalves were collected for the study. The length-breadth and length-width relationships for the entire study period were L = 1.540 + 0.6742B and L = -0.0873 + 0.4561W respectively. The length-total weight, length-wet weight, length-shell weight and length-dry weight relationships were W = 0.0003805L3.066, W = 0.0000255L3.054, W = 0.0000705L3.139 and W = 0.0000042L3.110 respectively. The values of b indicated the relative growth in body weight and superior physiological condition of the mussels. The monthly mean data on condition index showed fluctuation. The maximum (16.36) condition was noticed during August 2005 and the minimum (4.16) in December 2005. The condition of mussels was fairly high from during May to September. The best period for harvest of P. favidens in river Seeta could be between May and September. The hierarchical cluster analysis showed three major groups of biological variables and sample size alone formed a separate group.