Research Journal of Environmental and Earth Sciences 4(11): 945-952, 2012 ISSN: 2041-0492 © Maxwell Scientific Organization, 2012 Submitted: July 07, 2012 Accepted: August 28, 2012 Published: November 20, 2012 Corresponding Author: J.F.N. Abowei, Department of Biological Sciences, Faculty of Science, Niger Delta University, Wilberforce Island, Nigeria 945 Effects of Water Pollution on the Condition Factor, Mortality, Exploitation Ratio and Catch per Unit Effort of Lagocephalus laevigatus in Koluama Area, Niger Delta Area, Nigeria E.N. Ogamba and J.F.N. Abowei Department of Biological Sciences, Faculty of Science, Niger Delta University, Wilberforce Island, Nigeria Abstract: Effects of water pollution on the condition factor, mortality, exploitation ratio and catch per unit effort of Lagocephalus laevigatus in Koluama Area, Niger Delta Area, Nigeria was investigated from April 2012 to May 2012; following an oil blow out in the area. To show the impact of the spill on the environment, catch rates are seasonally dependent and vary between 15-120 kg/day. About 120 wooden canoes were sighted in the communities studied. The canoes are basically in two categories namely, small sized boats of less than 5 m length and medium- sized ones ranging between 5 and 7 m long. There was no temporal variation in the condition of the fish with condition index value ranging from 0.86-1.00 and condition factor value of 0.98. The K value of 0.98 estimated from this study shows that Lagocephalus laevigatus from the study area was in extremely poor condition. Total mortality (Z) value was 1.5 yrG1. Natural Mortality (M) value was 0.97; Fishing mortality (F) value was 0.52. Value for the rate of exploitation was 0.35 with corresponding percentage value of 35%. The result shows that Lagocephalus laevigatus with an exploitation rate of 0.35 is below the optimal value for sustainable yield, for the exploitation of the fishery. These populations therefore stand the risk of under exploitation if urgent measures are not taken to develop the fishery. Keywords: Koluama area, Lagocephalus laevigatus, Niger delta, Nigeria, population parameters, water pollution effects INTRODUCTION Population parameters evaluate the effect of fishing on a fishery as a basis for fishery management decisions (Sissenwine et al., 1979). The fundamental models used are based on four parameters: Growth, recruitment, natural and fishing mortality (Ricker, 1975). Age and growth are particularly important for describing the status of a fish population and for predicting the potential yield of the fishery. It also facilitates the assessment of production, stock size, recruitment to adult stock and mortalities (Lowe- McConnel, 1987). Fish mortality is caused by several factors, which include, age (King, 1991); fish predation (Otobo, 1993) environmental stress (Chapman and Van Well, 1978); parasites and diseases (Landau, 1979) and fishing activity (King, 1991). The exploitation rate is an index, which estimates the level of utilization of a fishery. The value of exploitation rate is based on the fact that sustainable yield is optimized when the fishing mortality coefficient is equal to natural mortality (Pauly, 1983). Significant contributions on growth studies have been made by Schaefer (1954), Beverton and Holt (1957), Ricker (1975) and Gulland (1969) among many other scientists, but the studies were concerned primarily with temperate stocks. On the other hand, studies on the population dynamics of tropical fish stock have been limited by the difficulty of ageing tropical fish species, which from the ecological perspective inhabit ‘steady state environment’. The length-weight relationship of fish is an important fishery management tool. Its importance is pronounced in estimating the average weight at a given length group (Beyer, 1987) and in assessing the relative well being of a fish population (Bolger and Connoly, 1989). Consequently length-weight studies on fish are extensive. Notable among these are the reports of Shenouda et al. (1994) for Chrysichthys spp from the southernmost part of the River Nile (Egypt); Alfred- Ockiya and Njock (1995) for mullet in New Calabar River, Ahmed and Saha (1996) for carps in lake kapitel, Bangladesh; King (1996) for Nigeria fresh water fishes; Hart (1997) for Mugil cephalous in Bonny Estuary and Diri (2002) for Tilapia Guinness in Elechi creek. Following the adoption of Peterson length frequency distribution method for ageing tropical fishes. There have been notable contributions by Longhurst (1964), Gulland (1969) and Pauly (1980) in this area of