Comparative histopathology of gladiator swimming crab (Callinectes pallidus) from two coastal areas in Lagos, Nigeria

Callinectes pallidus is an economically important species of crab which inhabits both inshore and estuaries often susceptible to contamination from anthropogenic sources. The present study examined histopathology of the tissues of Callinectes pallidus from two coastal areas in Lagos, Nigeria, as a possible measure of degree of susceptibility to environmental stress.Tissues (hepatopancreas, gill, ovary, intestine and flesh) of samples of 30 crabs from each coastal site were processed for histological examination using standard method. The histopathological results in this study showed no structural alteration in gills, intestine and flesh in crabs from both sites, but there was a great structural degeneration and lesion in the hepatopancreas and ovaries of C. pallidus from Agbara (site 2). The environmental stressors identified in Agbara based on documented literatures includes Brewery effluents- that contains high carbohydrate, nitrogen and washing reagents; high concentration of heavy metals such as Cu, Zn and Fe and pharmaceutical effluents. The present study thereby revealed that hepatopancreas and ovaries of C.pallidus from Agbara (site 2) are more susceptible to these environmental stressors. Thus, it could be concluded that C.pallidus from site 2 are more susceptible to environmental stress than those from site 1.The present study also provide a fundamental information on the well being of C.pallidus from the two sites. Therefore, efforts should be intensified to avert future deleterious effect of the environmental stressors on the studied species in Agbara water body.Keywords: Susceptibility, hepatopancreas, ovary,stress, alteration and cra

Trophic ecology of fishes: consolidating the basic (traditional) methods

Studies of food and feeding ecology are important to investigate trophic interrelationships of fishes in their resident water bodies. These are usually achieved using various important methods. However because no single measure gives an overall representation of the feeding habits of fish, best results are achieved only when methods are used to complement one another. This paper reviews various methods used in studying trophic fish ecology and suggests consolidation of the traditional or basic methods with relevant statistical indices and local ecological knowledge. More advanced methods are also proposed as valuable tools because they compensate for some possible errors that may arise from the use of quantitative methods

The meeting point between fisheries science and traditional ecological knowledge in fisheries

Traditional Ecological Knowledge (TEK) is the sum of data and ideas acquired by a human group on its environment. Over the years, there has been a growing lack of confidence in centralized scientific fisheries management. Traditional ecological knowledge is recognized as a valuable tool for understanding trends of marine resources, ecosystem management and conservation. Some reseachers and policy-makers have called for TEK to play an increased role in fisheries management decisions. TEK helps to develop management practices which allow economic development without the over-exploitation of natural resources. However, the acceptance of TEK in fisheries management has been partly hindered by difficulties in translating local ecological knowledge into a form that can be applied dierectly to conventional top down approach of western fisheries management. For full integration of TEK and scientific knowledge in fisheries management, there must be constant communication, continuous education, mutual trust, collaborative validation of knowledge and respect for a workmg relationship to be sustained

Bio-economic assessment of a purse seining at Orimedu fishing settlement off Lekki, Lagos State

A bio- economic assessment based on the Return On Investment (ROI) of a single purse seiner was done from August 2007 to February 2008 at Orimedu. Catch composition in terms of relative abundance of species and their sizes were also assessed. Total income was derived from the product of average selling price for a basin of fish, average number of fish basins sampled from a purse seiner, number of fishing trips of a purse seiner per month and the total number of months. Total costs were derived from the sum of capital costs, operational costs, depreciation costs, maintenance cost and labor cost which was estimated as 1/3 rd of total income. Fish catch was dominated by mature fish consisting of over 90 % clupeids and measured in heaps of 200 pieces in basins. On the average, there were 17 basins of fish from a purse seiner. Each basin was valued at N8000 and the average number of fishing trips in a month was 9. The calculated ROI was 30.96% indicating that the fishing method was lucrative. The study showed that purse seining is both biologically and economically sustainable with great potentials to alleviate poverty if adopted by the local Nigerian fisherfolks

An overview of the challenges and prospects in developing an aquaculture industry in Lagos State, Nigeria

Macroeconomic growth and the development of sustainable business activities are interrelated. In Lagos State, aquaculture is a marginal economic activity thriving mainly on a semi-intensive level. Notwithstanding the available potentials for the development of successful commercial aquaculture enterprises in the state, the transformation to a full-flagged industry continues to be undetermined by certain critical factors. Feasible development strategies may be sought in increasing all stakeholders' capacity in the formulation of policies, plans and regulations, a complete separation of aquaculture from the capture fisheries in administrative structure and policy; the adoption of precautionary approach; provision of economic incentives to enhance private investments and increase output,respectivel

A prelimnary study of diet in the juvenile gorean snapper, Lutjanus goreensis (Valenciennes, 1830) from Five Cowrie Creek, Lagos, Nigeria

Diet of the juvenile Gorean snapper, Lutjanus goreensis from Five Cowrie Creek was investigated between April 2008 and January 2009. Analyses of 184 specimens by numerical (NO), frequency of occurrence (FO) and geometric index of importance (GII) methods, respectively revealed a moderately high proportion (47.83%) of stomachs with food or prey. Shrimps and crabs constituted more than 80 % of total prey items. Other dietary components included lobsters, stomatopods, whole fish and fish parts. Similarly, analysis of diet composition by size - groups also indicated a predominance of the shrimps and crabs over all other prey items. In conclusion, L. goreensis can be described as a top-level carnivore feeding almost exclusively on epibenthic crustaceans in the juvenile stage