The Age and Growth of Callinectes amicola (De Rochebrune, 1883) from Okpoka Creek, Niger Delta, Nigeria.

The Age and growth of Callinectes amicola from Okpoka Creek in the Niger Delta area of Nigeria was studied for a period of one year (January - December 2007). The size classes 30- 39.9mm and 40- 49.9mm constituted the highest with 31.0% and 31.5% respectively. Very small size class below 10mm was completely absent and largest size group (70-79.9mm) were very few (0.2%). The results of the modal length-at-age revealed that all the sexes of Callinectes belonged to the age groups 1 to 3 years. Four year classes with modal classes ranging from 6.7 - 68.3 mm for males; 5.0-78.3mm for female and 5.8-75.8mm for combined sex. The annual carapace length increment was highest in year class 1+ and declined with time for both sexes and combined. The absolute increment was: male (17.5mm for 1-2y, 14.1 mm for 2-3y and 20.53mm annual mean); female (18.3 for 1-2y, 10.8 for 2-3y and 24.43 annual mean) and combined (18.3mm for 1-2y, 12.5mm for 2- 3y and 24.43mm annual mean). Relative increment was male (47.7% for 1 - 2y, 26.0% for 2- 3y and 36.85% annual mean); female (37.2% for 1 - 2y, 16.0% for 2- 3y and 26.60% annual mean) and combined (40.7% for 1-2y, 19.7% for 2-3y and 30.20% annual mean). Instantaneous rate of increase was male (0.390 for 1-2y, 0.231 for 2- 3y and 0.311 annual mean); female (0.316 for 1-2y, 0.148 for 2- 3y and 0.232 annual mean) and combined (0.341 for 1 - 2y, 0.180 for 2- 3y and 0.261 annual mean). Powell-Wetherall plot was L„ (61.80mm), K (0.995 y~l) and Z/K (1.694). The length at age data was L„ (61.80mm), K (2.10/ʹ), to (1.220), $ (3.90) and Rn(0.122) ELEFAN 1 scans routine was L„ (61.80), R (2.10), $ (3.90) and Rn (0.121). The non-seasoned version of the Von Bertalanffy Growth Function (VBGF) was L„ (87.305mm), K (0.636 y ʹ), t0 (0.889) and $ (3.685). The longevity or maximum age (Tmax) was 4.7 years. The overall growth parameters obtained were: L„ = 61.80, K= 1.244y_1, t„= 1.0545, Z/K = 1.694, R = 0.995, $ =3.825 and Rn =0.121.