ESTIMATION OF GROWTH AND MORTALITY PARAMETERS OF THE PONTIC SHAD (ALOSA IMMACULATA BENNETT, 1835) IN ROMANIAN SECTION OF THE DANUBE RIVER

Daniela Cristina Ibănescu, Adina Popescu, Aurelia Nica

Abstract
   Features of the growth and mortality parameters were studied during 2009 on a total of 1011 specimens of Pontic shad, vulnerable specie of community interest whose population is in decline. The total length and weight migratory specimens ranged between 24 ÷ 39 cm and 100 ÷ 440 g. Using the ELEFAN program in FiSAT computer package, the calculated von Bertalanffy growth function parameters were L_∞ = 40.43 cm and k = 0.38 yr^-1, to = -0.08 years. The length - weight relationship (L - W) found is: W = 0.0526 * L2.487 (r² = 0,85).
   Total mortality (Z) was calculated using the length converted catch curve analysis method in FiSAT computer software package and has a value Z = 1.54.
   Natural mortality was computed as M = 0.588 yr^-1 at an annual average temperature of 12°C, hence, the fishing mortality was computed as F = Z - M = 0.952 yr^-1.
   The exploitation rate (E) calculated as E = F / Z for the Pontic shad population is 0.618.

Key words: the growth and mortality parameters, von Bertalanffy equation, L - W relationship (LWR)