Factors contributing to the outcome of stocking programmes in Cuban reservoirs

In less-developed countries, fisheries enhancement using stocking is a comm on practice to manage reservoirs for biomass production. In many cases, the re appears to be little control over whether the stocking activity is appro priate or necessary. Cuban reservoir fisheries have been usually managed to maximize fish biomass. Blue tilapia have been introduced and supplemented in reservoirs, and Chinese carp are introduced and maintained in reservoirs throughout the entire island. Supplemental stocking with introduced fish s pecies is a usual practice to manage large and medium-sized reservoirs. Sma ll and very small reservoirs have been managed as semi-intensively enhanced fisheries with carp and tilapia stocking. The main purposes of the present paper are to study the factors contributing to the outcome of stocking pro grammes in reservoirs and to test the hypotheses that supplementary stockin g for self-sustained fish populations usually cannot contribute to increase fish yield. Yield and stocking data by groups of fish species were availab le for Cuban reservoirs. Total fish yield was only slightly related to tota l fish stocking density for the complete set of reservoirs. However, this r esult was mainly because of the relationship between total yield and cyprin id stocking for semi-intensively-used reservoirs. Tilapia yield was not sig nificantly related to tilapia stocking for both extensively and semi-intens ively-used reservoirs. However, yield and stocking for cyprinids were highl y related for both reservoir subsets. Therefore, cyprinid stocking-was effe ctive in certain reservoirs, but tilapia stocking was not effective in any reservoir. Moreover, tilapia stocking was a superfluous activity for reserv oirs where tilapia have an adequate natural reproduction cycle.