Biometric variables and relative growth of the date mussel Lithophaga lithophaga (L., 1758) (Bivalvia: Mytilidae) from the Eastern Mediterranean Sea, Egypt

Abstract

The present study was conducted to determine the biometric features of the Egyptian population of the date mussel Lithophaga lithophaga and the relationships between them. Over the study period, 746 samples were collected from the shallow area of Alexandria coastal line (3-6 m depth) by SCUBA diving from December, 2017 to November, 2018. The length frequency analysis of all the samples collected revealed that the most abundant shell length ranged from 45.0 to 50.0 mm amounting to19.71% of the population. The specimens ranged from 11.9 mm (minimum length) to 83.99 mm (the largest length) and 0.40 g to 40.1 g in weight. The current study is focusing on the relationships between length-width, height and length-weights (length-total wet weight, length-tissue dry weight and lengthshell dry weight). All relations were of negative allometry growth pattern. The relationships between length and height/width were linear, while those between length-weights followed a non-linear pattern. Moreover, the results revealed high correlation coefficients between these shell morphological characters of the present studied population in the Egyptian waters. Moroever, peak values of meat yield (MY) and condition index (CI) were found in July, which is indicative of the nutritive status of L. lithophaga mussel. The mean values were from 23.91±5.61 to 47.32±5.14 and from 24.23±8.69 to 44.0±11.0 for meat yield and condition index, respectively. The results of the current investigation are valuable information about this species in the studied area, however, more research is required for a better understanding of the reproductive characteristics of L. lithophaga and the long term effects of its burrowing behavior on the ecosystem.