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Increasing Stress In High Levels

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two main effects. Water quality is reduced and there are social effects associated with the high densities. Some species are more tolerant than others and the less tolerant ones are prone to more stress. As a result of overcrowding for instance, stress in fish is caused by the elevated levels of nitrogenous products such as ammonia, nitrate and nitrite. These products in high levels can cause severe stress while slightly elevated levels can contribute to chronic stress (Ferner, 2001). Overcrowding also causes Social hierarchies to form within the fish. This leads to harassment, aggressive interactions, lack of hiding places, inadequate tank size and too few fish for schooling. As stated by Ugwemorubong and Ojo (2011) harassment from other …show more content…

Low levels of oxygen, that is, oxygen levels that are below the recommended levels mean that the fish puts more energy into respiration. The fish therefore has to breathe faster than the optimum level and this can cause chronic stress in the fish. Very low levels can lead to severe short-term stress and eventually death. Uneaten feed, faeces etc in the water or fish tanks all lead to biological oxygen demand (Ugwemorubong and Ojo, 2011). In addition to oxygen, other gases can build up and cause problems for the fish. Hydro dams, improperly sealed pipes, oxygenating water under high pressure; can all lead to super-saturation which can stress fish in a number of ways.
Stress in fish is also caused by improper pH levels or their abrupt changes. These have the potential to cause acute stress while continually elevated or lowered pH levels cause chronic stress. PH changes of 1.5 points below or above the recommended levels can have a negative effect on the fish over time and should never be considered acceptable. Many fish adapt to long-term changes, but there are still limits to how many changes the fish can take (Foster and …show more content…

Improper salinity levels mean more energy expended by the fish to maintain osmotic homeostasis. Atlantic salmon lives within very specific salinity levels in their saltwater phase. According to Foster and Smith, their bodies work hard to maintain the osmotic gradient between themselves and the environment in which they are occurring. If their environmental salinity is not specific to their needs and is not held at a steady level, they have to work harder to maintain their osmotic gradient, which generates chronic stress. Salinity is closely connected with other biological Factors. For instance, during the parr–smolt transformation there is an increased production of cortisol which helps the fish in the transition. This is an important hormone in the smoltification process, but it also affects the immune response. Spawning fish are also in the throes of major hormonal changes and these make fish less resistant to the effects

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