Allometry and condition index in green mussel Perna viridis (L.) from St Mary's Island off Malpe, near Udupi, India

The morphometry, length-weight and condition index of green mussel P. viridis (L.) from St Mary's Island, off Malpe, near Udupi, were examined from December 2004 to December 2005. The calculated regression equations between length and breadth and length and width for the entire study period were L=0.5071+ 0.3921B and L=0.0179 + 0.3225W respectively. The monthly b values of length-breadth and length-width relationships varied from 0.3636 (March 2005) to 0.4374 (December 2004) and from 0.3022 (December 2005) to 0.3466 (August 2005) respectively. The data on length-total weight (W=0.0986L(2.9495)), length-wet tissue weight (W=0.031L(2.7173)), length-dry weight (W=0.005L(2.9337)) and length-shell weight (W=0.0351L(3.061)) showed a nonlinear pattern. The coefficient of allometry (b) values ranged from 2.7949 (April 2005) to 3.0999 (September 2005) for length-total weight relationship and from 1.5203 (August 2005) to 3.328 (March 2005) for length-dry weight relationship. The monthly mean values of the condition index varied from 5.17 (December 2004) to 7.76 (November 2005). The variation in condition index followed the breeding period and seasons. The maximum condition index (22-24) was recoded in May 2005. Based on the data on condition, it is suggested that the ideal period for commercial exploitation of Perna viridis from the Island is from March to August, when the meat yield is the highest. The hierarchical cluster analysis using complete linkage showed three major groups of biological parameters of mussels. The PCA showed a total of five components, which together accounted for 89.31% of total variance. The first component accounted for 44.08% of variance, followed by second component for 18.02% and the third component for 11.66% of variance. The remaining fourth and fifth components together accounted for 15.55% of variance.