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

Abstract

Unio tigridis has an importance for the biodiversity of freshwater ecosystem of theTurkey. However, there is no available literature in the world on the growth of thisspecies yet. The aim of this study, therefore, was to describe the age, growth andmortality of this species living in Lake Gölbaşı from Hatay providence, Turkey. A total428 of specimen were collected using by divers with hand dredges in depth of 1 to 6meters based on annual sampling strategy from June- 2004 to May- 2005. Lengths andweighs 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 asW0.193L2.63 (R20.94). Thus, a negative allometric growth was detected in the sampledpopulation. The age of each individual was determined by counting the external shallannuli-growth interruption lines. The sampled population was composed of 18 ageclasses. Specimen belong to age class 7 was the most presented with 20.33 percent in thepopulation. The rate of male to female (m:f) was 0.91:1. Seasonalized von Bertalanffygrowth model (SVBGM) was used to describe the growth. From these results, it wasshown that seasonality in growth does not occur in this lake for this species (L 8.80cm (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 Rsquare 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 Kand low L, this type of species are vulnerable to extinction.