Population dynamics of the freshwater mussel Parreysia cylindrica Annandale and Prashad, 1919 from the Western Ghats, India

Abstract

Morphometric and length-weight relationships, condition index, age and growth, mortality, exploitation and lifespan of freshwater mussel Parreysia cylindrica Annandale and Prashad, 1919 inhabiting the Malthi River, a tributary of the river Tunga, in Thirthahalli Taluk were studied. The calculated linear equations of length-breadth and length-width of mussels wereL = 1.6869 + 0.4688 B and L = - 2.9198 + 0.4687 W and respectively. The estimated b valuesof length-breadth relationship ranged between 0.4285 and 0.4991 whereas for length-width relationship the values fluctuated between 0.4006 and 0.4776. The estimated equations of length-total weight, length-wet weight, length-shell weight and length-dry weight wereW = 0.000046L3.279, W = 0.000046L3.194, W = 0.00005L3.461 and W = 0.000021L3.332, respectively. Monthly average values of condition index varied from 5.07 to 11.97. High values of condition were noticed during March to May and low values from October to February. The estimated asymptotic length was 56.97 mm and maximum length recorded in the field was 50.2 mm.The growth coefficient and theoretical time at zero length were 0.53 y-1 and -0.0376 y,respectively. The growth performance index was 3.236. The total, natural and fishingmortality rates were 2.00, 0.99 and 1.01 y-1 respectively and exploitation rate was 0.505. The lifespan was estimated to be 5 years and 8 months. Keywords: Age and growth, Allometry, Bivalve mollusc, Condition index, Karnataka, Life-history variables