Fish life history strategies Essay

1.5 Justification
Studies on fish life history strategies determine how fish populations respond to environmental changes. Information on life history strategies is lacking for riverine fish species of the Lake Victoria basin for example there is little information for species assemblages in the Kuja-Migori river basin. Currently, there is little exploitation of the riverine species in the Kuja-Migori system. Information to be obtained on life history traits of Kuja-Migori river system can be used to formulate fisheries regulations for managing the riverine fishery. Additional descriptions of life history characteristics are needed to develop adequate conservation strategies and prevent further decline of riverine populations.
CHAPTER TWO
2.0 Literature Review
The riverine ecosystems are to a large extent influenced by human activities, and disturbances due to anthropogenic activities (Livingston et al. 1997 Rose 2000). In the aquatic ecosystem fishes are the most numerous and diverse group of animals. Due to their long evolutionally history the diversity of fish exceeds that seen in terrestrial animals (Volff 2004).
Most of the fishery resources around the world are overexploited. Therefore, studies on life history traits of fish are important in revealing different life history and show population responses to overexploitation due to fishing (Wenjia et al., 2015). Life history strategies of fishes evolve by adapting to the natural changes of environmental parameters (Lytle and Poff, 2004). Studies on life history traits of riverine fishes are important in explaining assemblage structures in different rivers (Goldstein & Meador, 2005). Riverine species are characterized by short life spans early maturation extended spawning period, multiple spawning bouts and high fecundity. Evolution of these traits has allowed species to overcome their unpredictable lives in the changing riverine ecosystems (Winemiller and Rose, 1992). Prolonged reproductive seasons increase the probability that reproduction will occur during favourable environmental conditions in each breeding season. This allows the fish to overcome fluctuations that may increase failure in annual breeding.
Fish life history strategies determine how fish populations respond to environmental changes (Olden and Julian 2010). Fish life history strategies differ in consistent patterns. The patterns are explained and predicted by the theoretical constructs of r and k selection. In case of unpredictable, nonselective, mortality an organism will allocate a greater portion of its energy resources to breeding. Optimal allocation of resources for an organism subjected to a high proportion of predictable, selective mortality will be increasing towards individual fitness, through competitive ability (King and McFarlane 2003).
The dependence of fish life history strategies on environmental parameters of freshwater fish assemblages forms a basis of developing models aimed at conserving indigenous species based on their responses to variation in environmental conditions (Welcomme et al. 2006). Fish life-history strategies include parameters related to offspring survivorship, fecundity and frequency of spawning, which represent adaptive traits that enable a given fish species to encounter changes in abiotic conditions in space and time (Gonalves et al., 2013).
When various fish life-history strategies for example growth, maturation and mortality are compared for a large number of fish, clear patterns are