Environmental Requirements for effective fish farming

Environmental Requirements for effective fish farming

Generally speaking, any person seeking to establish a fish farm will require as the case may be, a number of separate approvals from different government agencies, such as an aquaculture licence from the Department of Fisheries, possibly a water use permit from a local or central authority to abstract water, structures (for materials, etc.) approval from the District Officer, a planning consent from the Ministry of Interior or any other authorized Officer, an borehole/well licence to obtain underground water for the farm and possibly a consent from the Council of Ministers for occupation of the foreshore area. In other words, any fish farming industry faces the prospect of getting a runaround from 3 to 6 – and this figure is likely to increase with the implementation of the legislation on control of pollution – different consenting agencies, each of which seeks to impose its own, often conflicting, and ad hoc requirements on fish farmers. Under this process, obtaining approvals may not be easy in the future, especially as old and new issues, such as public interest, environmental effects and structures are covered in a interdisciplinary permit approval process. It is likely to involve greater costs as applicants are likely to have to pay for or provide independent environmental impact assessments prepared by professional environmental consultants.

Environmental Requirements for effective fish farming

a) Optimal Temperature:

Various species and strains of tilapia differ in tolerance to low temperatures, but growth is poor at water temperatures below 16 degrees C and death occurs from temperatures below 12 degrees C . Most will not feed or grow at water temperatures below 15 degrees C and will not spawn below 20 degrees C. The normal water temperature should be between 20 to 30 degrees C . Higher temperatures will result to fish death.

b) Optimal Dissolved Oxygen (DO):

Tilapias are able to tolerate low levels of dissolved oxygen. Usually, well fertilized ponds will have low levels of oxygen early in the morning. Night activities are dominated by respiration and decomposition which reduce DO. Larger fish are less tolerant than juveniles. This could be due to the difference in their metabolic demand. The optimal DO for tilapia culture is 4 mg/litre (50%) and should not go below 2.3 mg/litre.

c) Salinity

All tilapia are tolerant of brackish water. The Nile tilapia is the least saline tolerant of the commercially important species but grows well at salinities of up to 15 ppt. The Blue tilapia grows well in brackish water up to 20 ppt salinity, and the Mozambique tilapia grows well at salinities near or at full strength seawater.

d) pH

pH refers to hydrogen ion concentration levels. Tilapia can survive in pH ranging from 5 to 10 but do best in a pH range of 6 to 9.e) AmmoniaMassive tilapia mortality will occur within a few days when the fish are suddenly exposed to water with unionized ammonia concentrations greater than 2 mg/L. Prolonged exposure (several weeks) to un-ionized ammonia concentration greater than 1 mg/L causes deaths, especially among fry and juveniles in water with low DO concentration.

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