Cage culture of tilapia (Oreochromis niloticus) in large reservoirs is an emergent aquaculture practice in
Brazil. Due to the availability of large amounts of suitable quality waters in hydroelectric dams, there is a
large but still undetermined potential for cage aquaculture in the upper Paraná River basin. Sustainable
aquaculture production should consider assessment of ecological carrying capacity for rational use of
natural resources such as water bodies. The present survey estimates the ecological carrying capacity
for tilapia cage culture in several sites on a large reservoir of “Ilha Solteira” upper Paraná River basin,
Southeastern Brazil. Ecological carrying capacity was estimated based on the Dillon and Rigler (1975)
mass balance model, considering limnological and farming field data to evaluate area-specific Phosphorus
loads that can be assimilated in these environments. Using average farming data of feed composition,
tilapia (O. niloticus) whole body composition and Feed Conversion Rate (FCR), the estimated emission of
Phosphorus per ton of fish produced was 14.8 kg P ton−1. Modeling provided evidence for the importance
of feed Phosphorus content and availability for determination of total allowable production, as well
as the relevance of proper inputs of limnological field data. When field data was collected, only two
sites (Ponte Pensa and Dourados) had aquaculture activities; as aquaculture is expanding, limnological
information provided in the present study is a registry of conditions found before the massive aquaculture
development. Production estimated to the reservoir as a whole (156,000 ton) is more than fivefold the
pooled production (30,000 ton) of the fifteen selected sites; if production estimated to the reservoir as a
whole cluster around a few best sites,than effects on water quality is expected to be evenmore drastic. The
limit of 1% occupancy by aquaculture posed by Brazilian government is not an effective safeguard against
excessive eutrophication, and detailed limnological studies are demanded for each inlet assigned for
cage aquaculture. The impact of cage fish farming on the aquatic environment by the release of nutrients
that affect water quality can not only bring about conflict with multiple users, but also primarily exert a
negative feedback effect in the cage operations themselves.
© 2015 Elsevier B.V.