POPULATION STRUCTURE AND BIOMETRIC RELATIONSHIPS OF Callinectes amnicola FROM THE CROSS RIVER ESTUARY, NIGERIA

Abstract

The population structure, carapace length-weight, carapace width- weight, carapace length-width parameters and
condition indices of 262 specimens of Callinectes amnicola from the Cross River Estuary, Nigeria, were estimated
for males, females and combined sexes. The results indicate that sex ratio was in favour of females (1:3.05, 
2 =
67.26, 1df). Females were significantly heavier than males (
2 = 12.15, 1 df, P < 0.05) but not significantly longer.
Weight was found to be isometric with carapace length (b = 2.37) while carapace width-weight was negatively
allometric (b = 2.17), indicating that the crabs get thinner with increase in width. The carapace length - width
relationship showed b is < 3.0, indicating negative allometric growth pattern. Mean values of condition factors
were higher in males than females suggesting males had a better condition during the study period. Average growth
rate of C. amnicola in the estuary was estimated as 3.0 - 7.5 mm CL/month (smaller crabs grew faster).