Assessment of the shery, growth and mortality characteristics of the cassava croaker, Pseudotolithus senegalensis (Sciaenidae) from coastal waters of Ghana

Abstract

This paper reports on the shery 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 shing method in the area with the shing season spanning July to March. Catch per unit effort (CPUE), determined as catch per net haul per day was 9.5 kg per haul in July 2012, 110 kg per haul in January-February 2013 and 47 kg per haul in March 2013. The species was absent from the shery from April 2013 to June 2013. Monthly catches varied from 2,295 kg to 31,500 kg, and specimens of the sh measured 7.5 cm TL to 105.4 cm TL and weighed 2.9 g to 7,634 g. The length-weight relationship of the population was described by the equation: BW = 0.005TL 3.04 ( r = 0.99), and grouping the sh 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 coecient (K) of 0.2 yr -1 , and total (Z), natural (M) and shing (F) mortality coecients of 0.68yr -1 , 0.42 yr -1 , and 0.26 yr -1 respectively, for the population. Longevity of the sh 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.