Growth pattern, condition factor, trace metal studies and ectoparasitic load of the blue crab, Callinectes amnicola from Lagos Lagoon, Badore, Ajah, Lagos, Nigeria

Abstract

Aspects of the biology of an economically important crab, Callinectes amnicola (De Rochebrune, 1883), were studied to determine the growth pattern, condition factor, ectoparasitic load and trace metal (Manganese, Zinc, Lead, Cadmium and Mercury) levels. Water and sediment samples were also collected for trace metal analysis and to determine bioconcentration factor in crab samples. Males recorded significantly longer carapace (p<0.05) and were heavier (p<0.01) compared to female crabs. C. amnicola showed negative allometric growth (p<0.05; b<3) regardless of sex or size using carapace width; however, with carapace length, the crab exhibited isometric growth for male (p>0.05; b=3) and positive allometric growth for female and sex combined (p<0.05; b>3). Males were better conditioned than females and condition increased with size for males. Only male C. amnicola were infected with ectoparasitic barnacles with a prevalence of 13.46%. The ectoparasites select better conditioned crabs for infestation and this colonization subsequently reduces the condition with increased size. Mean trace metal values recorded for C. amnicola, water and sediment were in the order Manganese>Zinc>Lead>Cadmium>Mercury. The gills had the highest mean values for all the trace metals measured and also had the highest bioconcentration factor with lead recording a factor of 42 from water. However, the edible portion such as muscle, chelipeds and carapace bioaccumulated Manganese, Zinc and Cadmium from water by a maximum factor of 4. Carapace length, growth pattern, condition factor and ectoparasitic infestation may be used to discriminate among sexes of C. amnicola. This study shows relatively low concentrations of trace metals compared to the WHO limits and C. amnicola may be used to monitor the bioavailability of trace metals in the Lagos Lagoon.

Pollution and Potential Ecological Risk Evaluation Associated with Toxic Metals in an Impacted Mangrove Swamp in Niger Delta, Nigeria

“…Less privileged people can, however, obtain protein from less expensive animals, such as crabs [ 52 , 53 ]. The swimming blue crab ( Callinectes amnicola ), for example, is recommended for a healthy diet [ 54 , 55 ]. Several health benefits have been associated with seafood fatty acids, including chemopreventive effects on cancer [ 56 , 57 ].…”

Diversity, biology and exploitation of brackish water crabs in West Africa: A review

“…The authors have suggested that knowledge be improved relative to the estimation and exploitation of stocks as well as to the biological understanding necessary for a successful breeding of Callinectes amnicola (Rochebrune, 1883) and Cardisoma armatum (Herklots, 1851). Considering the full breadth of diversity in crab species in West African lagoons (Monod, 1956;Manning and Holthius, 1981) and in view of the scientific knowledge produced on this zoological group so far (Akin-Oriola et al, 2005;d'Almeida et al, 2006;Arimoro and Idoro, 2007;d'Almeida et al, 2007;d'Almeida et al, 2009;d'Almeida et al, 2009;d'Almeida et al, 2010;Udoh and Nlewadim, 2011;Omuvwie and Atobatele, 2013;Olakolu and Fakayode, 2014;Sankare et al, 2014 a;Onyekachi and Edah, 2014;d'Almeida et al, 2014), it appears necessary to have a review in order to establish what the current understanding on this group of crustacean is. We review known lagoon crab species in the Gulf of Guinea, their biology, and exploitation in order to identify relevant research prospects for this zoological group.…”