Abstract
As fisheries production in reservoirs of most countries is a secondary use, challenges for improved management of fisheries should be addressed by building partnership between fisheries and other interested groups such as agriculture concerned with water management. Attempts were therefore made to develop empirical fish yield predictive models in ten irrigation reservoirs of Sri Lanka incorporating morphological, edaphic and hydrological parameters together with fishing intensity, with a view to investigating their influence on fish yields. Reservoir fish yield was found to be significantly correlated with two formulations of morpho-edaphic index (i.e., conductivity in μS cm-1/mean depth in m [MEIc] and alkalinity in m. equiv. l-1)/mean depth in m [MEIa]), and a relative reservoir level fluctuation index (RRLF), defined as the mean amplitude of the annual reservoir level fluctuations divided by the mean depth of the reservoir. Both MEIc and MEIa also had significant positive ln-ln relationships with RRWL, indicating that RRWL can be used as an independent variable in reservoir fish yield prediction. Reservoir fish yield was also related to fishing intensity (FI in boat-days ha-1, yr-1) conforming to a ln-linear regression model (p Ln FY = 3.245 + 0.327 Ln MEIa + 0.023 FI (R2 = 0.355; p Ln FY = 3.403 + 0.249 Ln MEIc + 0.019 FI (R2 = 0.369; p Ln FY = 1.330 + 0.650 Ln RRWL + 0.016 FI (R2 = 0.593; p The empirical yield predictive model based on RRWL and FI as independent variables was more robust than those based on MEIa and MEIc, and the former has significant management implications because RRWL can be manipulated by irrigation authorities whereas control of FI is under the jurisdiction of fisheries authorities. Hence, through an effective dialogue between irrigation and fisheries authorities, there is a considerable potential to optimize fish yields in irrigation reservoirs of Sri Lanka.
Highlights
Reservoirs in the tropical world significantly contribute to inland fish production, despite their primary uses are irrigation, hydroelectricity generation and drinking water supply (Fernando and Holičik 1991; Welcomme 2001; Amarasinghe and De Silva 2015)
Both forms of morpho-edaphic index (MEIa and MEIc) had significant positive ln-ln relationships with reservoir fish yield (p
Fish yield was significantly correlated with RRWL according to a positive ln-ln relationship (p
Summary
Reservoirs in the tropical world significantly contribute to inland fish production, despite their primary uses are irrigation, hydroelectricity generation and drinking water supply (Fernando and Holičik 1991; Welcomme 2001; Amarasinghe and De Silva 2015). The challenges for sustaining and ensuring improved management of inland fish production in reservoirs are needed to be addressed by building partnerships between fisheries and other interested groups concerned with water management (Dugan, Sugunan, Welcomme, Bene, Boummett, Beveridge et al 2007). This is important in irrigation reservoirs because those who are engaged in water management for agriculture are keen to increase overall benefits of water productivity to food security and poverty reduction (Dugan et al 2007). Several studies have shown that it would be important to incorporate fishing effort together with the morphometric and edaphic variables to predict fish yields in lakes and reservoirs (Ranta and Lindström 1989; Bayley 1988; Moreau and De Silva 1991)
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