Abstract
This paper reports on the fishery and some population parameters of the cassava croaker (Pseudotolithus senegalensis) at Anlo Beach near Shama (5°01’ N, 1∘37’ W) in the Western Region of Ghana. The study was conducted from July 2012 to June 2013 to contribute to information on the dynamics of demersal stocks in the country. Beach seining was the prime fishing method in the area with the fishing season spanning July to March. Catch per unit effort (CPUE), determined as catch per net haul per day was 9.5 kg in July 2012, 110 kg in January–February 2013 and 47 kg in March 2013. The species was absent from the fishery from April 2013 to June 2013. Monthly catches varied from 2295 kg to 31,500 kg, and specimens of the fish measured 7.5 cm TL to 105.4 cm TL and weighed 2.9 g to 7634 g. The length–weight relationship of the population was described by the equation: BW = 0.005TL3.04 (r=0.99), and grouping the fish at 5 cm class intervals showed modal lengths at 15.0–19.9, 35.0–39.9 and 60.0–64.9 cm TL. Analysis of the length-frequency distribution using the ELEFAN programme indicated an asymptotic length (L∞) of 110.3 cm TL, a growth coefficient (K) of 0.2 yr−1, and total (Z), natural (M) and fishing (F) mortality coefficients of 0.68 yr−1, 0.42 yr−1, and 0.26 yr−1 respectively, for the population. Longevity of the fish was estimated to be 15 years. A low exploitation level of the stock is suggested by the calculated exploitation ratio, E=0.38. These population characteristics are compared with those of other West African P. senegalensis populations.
Highlights
Croakers (Family Sciaenidae) are widely distributed along the west coast of Africa from Morocco to Angola (Paugy et al, 2003), and have been reported from Namibia (Chao and Trewavas, 1990)
This paper reports on the fishery and some population parameters of the cassava croaker (Pseudotolithus senegalensis) at Anlo Beach near Shama (5° 01' N, 1°37' W) in the Western Region of Ghana
Based on these records and other considerations across the West African sub-region, Nunoo (2015) and Nunoo and Nascimento (2015) suggested that P. senegalensis and P. typus be considered as threatened species
Summary
Croakers (Family Sciaenidae) are widely distributed along the west coast of Africa from Morocco to Angola (Paugy et al, 2003), and have been reported from Namibia (Chao and Trewavas, 1990). The cassava croaker Pseudotolithus senegalensis is an economically important demersal fish in Ghana (Koranteng, 1997) as in the fisheries of other West African countries, e.g. Cameroon (Djama and Pitcher, 1989), Nigeria (Anyanwu and Kusemiju, 1990) Benin (Sossoukpe et al, 2013a) and Liberia (Wehye et al, 2017). Stock assessment survey records show that the biomass of the Sciaenidae declined by 37% from 2000 to 2006, and mean body size of species has declined from 50 cm TL in 1989–90 to 25–30 cm TL in recent times (Nunoo and Nascimento, 2015) Based on these records and other considerations across the West African sub-region, Nunoo (2015) and Nunoo and Nascimento (2015) suggested that P. senegalensis and P. typus be considered as threatened species. Considering the high incidence of juvenile cassava croakers in beach seine landings from Cape Coast waters (Ghana), Blay, Awittor and Agbeko (2006) cautioned the likely negative effect of this fishery on recruitment of juveniles into the adult stocks
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