Preliminary Studies on Impacts of Ocean Acidification on Diversity of Fish Species Landed By Artisanal and Semi-Industrial Fisheries in Ghana

Abstract

Increased absorbance of carbon dioxide from the atmosphere has led to the changing of the chemistry of the oceans. In addition to already existing stressors, the resultant ocean acidification poses multiple threats to marine species biodiversity; and goods, services and livelihoods that depend on them. This study set out to determine possible impacts of globally occurring ocean acidification on the abundance and diversity of fin- and shellfish species and ichthyoplankton in the artisanal and semi-industrial fisheries of Ghana. Physico-chemical parameters of the sites where fishing by artisanal and semi-industrial vessels were carried out were collected in the lean and peak fishing seasons. Fish samples were collected, species identified, counted and diversity indices calculated for each fishery and fishing season. A Canonical Correspondence Analysis (CCA) was used to identify which of the principal factors influenced the fish species. Four ocean acidification parameters (pH, carbonate ion concentration, total alkalinity, Revelle factor) out of six principal components were identified to contribute significantly (RELATE, r = 0.955, P < 0.05) to biological variations observed in the two fisheries. A decreasing trend in ocean acidification indicators was observed for both fisheries and variations observed in species abundance between seasons and fisheries, which provide evidence of the possible occurrence of ocean acidification in Ghanaian waters and likelihood of impacts on fish diversity. Continuous long term monitoring of the studied parameters and inclusion of adaptive and mitigative strategies for impacts of ocean acidification in marine fisheries management plans is recommended.