Age, Growth and Mortality of Unio tigridis (Bourguignat, 1852)

Abstract

Unio tigridis has an importance for the biodiversity of freshwater ecosystem of the Turkey. However, there is no available literature in the world on the growth of this species yet. The aim of this study, therefore, was to describe the age, growth and mortality of this species living in Lake Gölbaşı from Hatay providence, Turkey. A total 428 of specimen were collected using by divers with hand dredges in depth of 1 to 6 meters based on annual sampling strategy from June- 2004 to May- 2005. Lengths and weighs of sample were ranged as 2.1 to 9.2 cm (6.79 ± 1.52) and 1.1 to 73.05 g (34.18 ± 15.56), respectively. Weight-Length relationship of all specimens was described as W=0.193L2.63 (R2=0.94). Thus, a negative allometric growth was detected in the sampled population. The age of each individual was determined by counting the external shall annuli-growth interruption lines. The sampled population was composed of 18 age classes. Specimen belong to age class 7 was the most presented with 20.33 percent in the population. The rate of male to female (m:f) was 0.91:1. Seasonalized von Bertalanffy growth model (SVBGM) was used to describe the growth. From these results, it was shown that seasonality in growth does not occur in this lake for this species (L∞ = 8.80 cm (Shell Length), K = 0.271 year-1, t0 = -0.161 year, C = 0.014, ts = 0.100 year with RSS = 23.22). The total mortality rate (Z ± Se) was calculated as 0.401 ± 0.015 year-1 with R-square = 0.99 (CL of Z with 95 % = 0.361 - 0.440 year-1). Although, there is no fishing, no pollution and no predation risk on this species yet, due to growth characteristic, high K and low L∞, this type of species are vulnerable to extinction.