Aspects of the biology of grey mullet, Mugil cephalus, in Lagos lagoon,Nigeria.
Journal Title: Aquaculture, Aquarium, Conservation & Legislation - International Journal of the Bioflux Society - Year 2010, Vol 3, Issue 3
Abstract
Investigations were conducted in Lagos lagoon, Nigeria between February 2009 and January 2010 on the biological aspects of grey mullet, Mugil cephalus with aim that information obtained from the study will contribute to the baseline data for carrying future studies on its ecology and conservation and development of its fisheries in this water body in particular and the Gulf of Guinea in general. M. cephalus is a commercially valued fish in Nigeria and a member of the Family Mugilidae. It is a catadromous fish species and widely reported in fresh, estuarine and brackish waters. In this study, the occurrence of this fish was both seasonal and salinity dependence with highest occurrence of 29.04% of the total catch when salinity was 20%o. 1+, 2+ and 3+ years’ old age classes were encountered. Fish ranged between 9.0 and 32.0 cmTL and weighed 12 and 345gBW respectively. The length-weight relationships were estimated as LogW= -11.551+ 2.968 Log L (r=0.001) for males and LogW= -11.249 + 2.929 Log L(r=0.993) for females. The estimated growth parameters of the von Bertanlaffy equation L∞ =37.0 (±0.22) cm, K = 0.22.year-1, and to = -1.8 year. The pattern of growth was near isometric with b=2.98 and 2.926 for males and females respectively. The diet composition of this species included nine (9) groups of food items. Occurrences of the diets varied monthly. The most foods were organic detritus and sand grains occurring in 40.60 and 85.66% of the stomachs respectively. The presence of algae in the stomachs was an indication of herbivorous habit of this fish, while occurrence of protozoans, crustaceans, nematodes, chaetognaths, and juveniles of other fish was indication of its carnivorous tendency, however, presence of detritus presumed the fish as an omnivore. The overall sex ratio was 1 male to 1.09 female. A chi-square revealed a significant departure from the theoretical 1:1 sex ratio (X2 =17.662 > X21, 0.05=3.84). Fecundity varied from 620,320 to 1, 082, 200 eggs (801,300 ±2,000 eggs) for fish measuring 20.1 cm TL(60.3gBW) and 32.0cmTL (345gBW) respectively. In this study the biological aspects of grey mullet, M. cephalus in Lagos lagoon were discussed.
Authors and Affiliations
Emmanuel Lawson, Abayomi Jimoh
Keywords
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