Sombreiro Nehri'ndeki (Nijer Deltası, Nijerya) Sardinella maderensis'in (Lowe, 1838) Bazı Popülasyon Parametreleri

Abstract

A study was conducted to estimate the growth and stock characteristics of the Sardinella maderensis (Lowe, 1838) from Sombreiro River of Niger Delta, Nigeria. Results obtained revealed that mean total length and the mean weight of S. maderensis ranged between 4.1cm to 18.5 cm and 5g to 55.5g respectively. The b value of the length-weight relationship was 2.58 thus, the species could be categorized as displaying allometric negative growth and condition factor was very high, it ranged from 3.04 to 4.43. The estimated von Bertalanffy growth parameters (VBGP) of L∞, growth coefficient (k) and age at zero length (t0) were 23.31cm, 0.54 and -0.03/year respectively. The species showed year round recruitment patterns having two peak periods during April and July. The total mortality (Z) was 2.74 year-¹., the natural mortality rate (M) and fishing mortality (F) were 1.32 and 1.42 respectively. The estimated fishing mortality (Z-M=F) stood at 0.518. The lengthbased index of growth performance (Ø'– phi prime) for S. maderensis was estimated at 2.46. The length at first capture L50 was 27.31 cm. The exploitation rate (Emax) was 0.421 whereas (E0.1) was observed to be 0.355 indicating that that the level of exploitation is already high and to obtain the maximum sustainable yield, the present level of fishing effort should be reduced through appropriate fishing regulation techniques..