Fish as bioindicators of habitat degradation in coastal lagoons of Ghana

Abstract. Eugenia BB, Armah AK, Dankwa HR. 2018. Fish as bioindicators of habitat degradation in coastal lagoons of Ghana. Bonorowo Wetlands 2: 9-26. Lagoons habitat forms an integral part of the marine fishing industry and provides essential spawning and nursery grounds for many fishes. Fish act as biological indicators of water quality and changes by summarizing information regarding their environment. Two lagoons, Laloi and Oyibi in the and Greater Accra and Central Regions of Ghana were studied to determine the ecological status using the Estuarine Fish Community Index (EFCI). Metrics assigned were the species diversity, nursery function, trophic integrity, and species abundance and composition. Water samples were obtained at the riverine, middle, and seaward portions during both high and low tides at each site. Fisherfolks were hired to fish at each of the sites. There are no significant differences between sites as measured by diversity indices. Multivariate analysis showed a considerable similarity between sites regarding species composition. This study identified eighteen species, including both finfish and shellfish. Two most abundant species during the study was the flathead grey mullet (Mugil cephalus) and the black-chinned tilapia (Sarotherodon melanotheron). Mugil cephalus dominated catches in the Laloi lagoon, whereas Sarotherodon melanotheron were dominant in the Oyibi Lagoon. The most dominant species collected for the Laloi lagoon were S. melanotheron, Lutjanus fulgens, and Eucinostomus melanopterus. Caranx hippos, L. fulgens, and M. cephalus constituted a significant part of fishes caught in the Oyibi lagoon. The carangid, Caranx hippos contributed primarily of the biomass of fishes collected for both lagoons. In the rainy season, total fish abundance was higher than the dry season. Chlorophyll-a concentrations and condition factor of S. melanotheron were highest at both lagoons. Total organic carbon was high in the Oyibi lagoon; hence, the high numbers of S. melanotheron recorded. Tides were an essential factor affecting physicochemical parameters. Oyibi displayed a moderate site rating, suggesting that it was under mild stress with some stress factors identified were garbage dumping, defecation, land-use changes, and increased human pressure. Meanwhile, Laloi Lagoon had a poor site rating, suggesting that it was under severe stress. The principal strains identified were overfishing, garbage dumping, mangrove degradation, and increased human settlements along the sides of the lagoon. The multi-metric index described served an effective method which reflects the status of lagoon fish communities and the overall ecosystem conditions.