Cage culture in shallow lakes from Argentina: Towards the development of an ecological aquaculture for a native zooplanktivorous fish

GARCIA DE SOUZA JAVIER RICARDO

Neuglobsow (Brandenburg)

Seminario; Seminarios Institucionales IGB LakeLab (Alemania); 2016

LakeLab (IGB-Berlin)

In South America, the aquaculture of the native zooplanktivorous fish Odontesthes bonariensis has some constraints that could be overcome by applying an ecological point of view. Floating cages were designed, built and installed in shallow lakes (Pampean Region of Argentina), and rearing experiments were carried out in order to analyze how the natural food supply affects the growth and survival of the species and to identify and evaluate the variables that most influence over the efficiency of O. bonariensies extensive cage culture. Zooplankton dynamics, seasonal changes and stocking densities emerged as key variables. A direct relationship between the zooplankton of the lakes and the growth of the fish cultured in cages was found. Bigger fish were obtained in spring, when zooplankton biomass was maximum in the lake with greater representation of large cladocerans. The contribution of the different sizes of zooplankton to the gut contents was related to availability and to fish size, and the access to bigger zooplankton - copepods and cladocerans larger than 0.7 mm- appeared to be a critical factor to promote better growth performance. Food selectivity decreased when the availability did and when the stocking density was high (high intra-specific competition), generating an expansion of the trophic breadth of the fish. This tendency to diversification of the diet and to change the mean prey size depending on fish length and stocking density, show the ?plasticity? of O. bonariensis feeding habits, and their possibility to adapt to changing environments. Spring was found as the better season to start the cultures taking advantage of zooplankton dynamics, and stocking density has been found as a variable that can be handled in a dynamic way, considering the zooplankton and fish diet features. Thus, Pampean lakes emerge as suitable environments where to develop an ecological aquaculture for the species. Taking into account the lack of habit of conducting these kind aquaculture systems in Argentina, the results support the assumption that ecological extensive cage culture in shallow lakes could be incorporated to the production cycle of the species overcoming some of the current limitations exhibited by the traditional intensive methods.