Population, Distribution Structure, and Fishery Potential of the Golden Deep-Sea Crab, Chaceon somaliensis in the Kenyan Coast in East Africa
Richard Mzungu *
School of Science and Informatics, Taita Taveta University, PO Box 635, 80300 Voi, Kenya and Kenya Fisheries Service-PO Box 90423 – 80100, Mombasa, Kenya.
Godfrey Makokha
School of Science and Informatics, Taita Taveta University, PO Box 635, 80300 Voi, Kenya.
Esther Fondo
Kenya Marine and Fisheries Research Institute - PO Box 81651 – 80100 Mombasa, Kenya.
Mika Siljander
Department of Geosciences and Geography, Helsinki Laboratory of Interdisciplinary Conservation Science, University of Helsinki, PO Box 64, 00014 Helsinki, Finland.
Elizabeth Mueni
Kenya Fisheries Service-PO Box 90423 – 80100, Mombasa, Kenya.
Benedict Kiilu
Kenya Fisheries Service-PO Box 90423 – 80100, Mombasa, Kenya and Coastal Oceans Research and Development in the Indian Ocean (CORDIO), Kenya.
*Author to whom correspondence should be addressed.
Abstract
Aim: This study focused on Chaceon somaliensis, a species in the Geryonid family, which is commonly found in the Horn of Africa. The species has global commercial value, yet little is known about it. The study adds to our understanding of the species by identifying its distribution, population structure, and fisheries potential in the Kenyan Coast.
Methodology: Maxent modeling assessed the appropriate environmental variables and predicted potential species distribution and hotspot locations. Regression was used to explain C. somaliensis distribution and some aspects of the population structure.
Study Design: Analytical study.
Results: Stratification by depth was observed with large male crabs (carapace width>150 mm, weight=1100 g) found in shallower depths (depth<501 m), while females, smaller in size (carapace width =92 mm, weight=316 g), seemed to prefer higher depths of >500 m. The Males were dominant (0.94), and females and juveniles comprised only 0.06 of the population. The population was found to be skewed towards males of large size (carapace width > 140 mm, weight 1100 g). Bathymetry and environmental variables associated with feeding and nutrients, such as phytoplankton, iron, and silicate, were the best predictors of species presence. Potential sites and hotspot areas occurred on a ridge at gentle slopes (0.98°– 4.31), with the hotspot areas being spatially about 3,230 km2 of 61,694 km2.
Conclusion: The fishery was considered productive and suitable for maintaining marine biodiversity (catch> 94% adults). The male population should be monitored as it is the key indicator of the status of the fishery.
Keywords: Geryonid, chaceon somaliensis, species distribution, maxent, habitat modelling, Kenya