Relationships between environmental factors and biological parameters of Asian wedge clam, Donax scortum, morphometric analysis, length-weight relationship and condition index: a first report in Asia

Abstract

Wedge clam, Donax scortum occurrence was studied from February 2009 to January 2010 in Padukere sandy beach, Karnataka (India). The following biological parameters were measured in 2367 individuals of the wedge clam, Donax scortum: length, breadth, width, total weight, shell weight, wet meat weight, dry meat weight and number of clams. The calculated linear equation of length-breadth and length-width relationships were B = 3.5968 + 0.5421L and W = 0.8191 + 0.4345L respectively. The length-total weight, length-wet meat weight, length-dry meat weight and length-shell weight relationships were 0.0001414L3.0224, W = 0.0000037L3.5204, W = 0.0000011L3.4513 and 0.0000852L2.9912 respectively. The values of correlation coefficient for different shell dimensional relationships were very close to unity. It was clear from the study that the most ideal period for clam harvest was April, June and December, especially when condition index was maximum. Length showed a strong correlation with silt and clay. Dry meat weight was negatively correlated with air temperature. Shell weight showed positive correlation with length, breadth, width and dry meat weight, and abiotic parameters, silt and clay. Condition index was positively correlated with electrical conductivity, whereas it was negatively correlated with dissolved oxygen. It showed a strong positive correlation with salinity. Seasonal fluctuation of condition index in D. scortum was probably related to reproductive activity. The harvesting of wedge clam could be carried out considering the maximum sustainable yield without over-exploitation