Discuss The Effect Of Temperature On Fish Poikilotherms

Among the various physical influencing the aquatic environment, temperature is of great importance and it plays a critical role in the life of aquatic poikilotherms (Singh et al., 2003). Five major effects of temperature on fish physiological processes include; controlling (setting the pace of development and metabolism), masking (affecting the expression of other environmental factors), limiting (influencing locomotors activity and hence distribution), directing (stimulating an orientation response), and finally, as a lethal agent, i.e., too much or too little can destroy the integrity of fish causing its death. Further, the most dramatic effect of temperature is to act as a lethal agent (Fry, 1947). Every species has an optimal temperature range at which they can be active, grow, reproduce and metabolize (Dodson, 2005). When temperature changes are substantial, fish have been shown to move from areas of warmer water to colder water to avoid thermal stress (Howell et al., 2010). While fish in lake may have cool, deep waters escape increased water temperatures. Fish in shallow

Under extreme temperatures, organisms become stressed at all levels, from the molecular and biochemical to the physiological and behavioural (Mora and Ospina, 2001; Hochachka and Somero, 2002; Dent and Lutterschmidt, 2003). Increased temperatures may be favourable for reproduction and recruitment of some species as thermal constraints that may have limited them in the past are removed (Hellman et al., 2008). Rising water temperatures has resulted in a sharp increase in the rate of egg development, hatching success and survival of swim-up larvae for Northern pike Esox lucius (Cooper et al., 2008). Increased water temperatures have also negatively impact on the survival of juveniles thus affecting the