Original scientific paper
ASSESSING THE SIZE-STRUCTURED STOCK OF THE SWIMMING CRAB Callinectes amnicola (CRUSTACEA: PORTUNIDAE) IN THE CROSS RIVER, NIGERIA
2023, 81 (2) p. 0-0
Samuel Ameh, Muhammed Isah, Elvis Ayim, Honor Ifon
Abstract
An important aspect of size-structured stock is the assumption that individuals grow from one size class to another after a certain period of time. In this study, a total of 2581 monthly samples of the swimming crab (Callinectes amnicola) were obtained for 13 months, from January 2021 to January 2022, from the artisanal crab fishery landings of the Cross River, Nigeria. Since it is difficult to determine the age of crabs due to molting and other physiological barriers, length-frequency data were used instead. The assessment of the swimming crab was based on some basic growth parameters of the von Bertalanffy growth function and the Beverton and Holt growth model. Results revealed that the asymptotic length and growth rate were 16.28 cm and 0.940 per year, respectively. The best growth index was estimated to be 2.40, while longevity and mortality were 3.19 years and 3.46 per year, respectively. The computed exploited rate of 0.41 was lower than the benchmark value of 0.5 and the maximum yield per recruit value of 0.421, confirming an under-fished stock. Sustainable exploitation of the swimming crab of the Cross River was advised.
Keywords
crab fishery, exploitation rate, growth function, length-based models, sustainable yield