Reproduction, growth, mortality and yield of Tilapia mariae Boulenger 1899 (Cichlidae) in a Nigerian rainforest wetland stream

Abstract

The biology and fisheries of Tilapia mariae, the only tilapiine cichlid fish in the Iba Oku (Uyo, Nigeria) wetland stream was studied. There were more females than males in the population. The smallest sexually mature female fish was 11.0 cm total length (TL) while the size at 50% maturity was 17.1 cm TL. Absolute fecundity (F e ) ranged from 953 to 3200 eggs and was positively correlated with TL. The fish bred year-round with peaks in November, March-April and July-September. The seasonalized von Bertalanffy growth function (VBGF) was fitted to the 12 consecutive months length-frequency data (n ¼ 2439) to obtain a VBGF with the following parameters: L1 (asymptotic length) ¼ 30.4 cm TL, K (growth coefficient) ¼ 0.4 year )1 , C (amplitude of growth oscillation) ¼ 0.4, and WP (winter point) ¼ 0.9. The seasonalized lengthconverted catch curve method gave Z (instantaneous total mortality coefficient) as 1.75 year )1 , M (instantaneous natural mortality coefficient) was 0.99 year )1 while F (instantaneous fishing mortality coefficient) was 0.76 year )1 and E ( ¼ F/Z the current exploitation rate) was 0.43. Length at first capture (Lc) was 17.7 cm TL. The fish was recruited to the fishery yearround with two pulses. From the Beverton and Holt relative yield per recruit analysis via the selection ogive procedure, E max (predicted maximum exploitation rate) was 0.54. The stock was not overexploited, since E < E max . This study also showed that the fish is an r-selected species with a few K-selected traits.

Biological Aspects and Fisheries Management of Tilapia Fish Oreochromis niloticus (Linnaeus, 1758) in El-Bahr El-Faraouny Canal, Al-Minufiya Province, Egypt

“…The sex ratio of most fish species in the wild tends to be 1:1 but deviations can occur and seasonal variations are common (Helfman et al, 2009). The sex ratio is influenced by several factors, including mortality, longevity and growth rate; these in turn lead to differences in the catch rate (King and Etim, 2004;Novaes and Carvalho, 2012). The values of sex ratio in the present study are in accordance with that estimated by some authors for studied species and differ from others.…”

Management Indicators and Growth Performance Index of Tilapia Zillii in a Tropical Coastal Estuary

“…According to Sparre and Venema (1992), longevity is more closely related to mortality than growth curvature, asymptotic length or ambient temperature. Maximum age of 7 years was estimated for T. mariae (King & Etim, 2004). This difference could be attributed to K-values of the two species T. mariae had a lower growth curvature parameter, K, (0.4/year) than T. zillii in this study (K=0.81/year).…”

Population dynamics of Sardinella aurita (Val., 1847) within Ghana’s coastal waters

“…From the present study, the calculated Z/K ratio was greater than 1, suggesting that the stock is mortality dominated. King and Etim (2004) highlighted that for a mortality dominated stock, Z/K ratio ≈ 2 denotes a lightly-exploited stock while values greater than 2 shows heavy exploitation. With the estimated Z/K ratio highly greater than 2, it showed that Sardinella aurita stock in Ghana's coastal waters is heavily exploited.…”