Size-weight relationship and condition factor of tilapia Orecochromis niloticus in five water bodies of Jalisco State, Mexico

Abstract

Variations of size -weight relationships and condition factor of 3,606 individuals of Oreochromis niloticus, collected from January to December 2010, in five water bodies, of Jalisco Mexico, were analyzed. Water bodies include two endorrheic lakes, known as “Laguna: de Zapotlán??? and “Laguna de Cajititlán???, and three artificial reservoirs of similar capacities, known as Calderón, El Salto and Basilio Vadillo dams. Relationships between the mentioned morphometric variables and habitat quality variables, such as temperature, oxygen, pH, oxide reduction potential (ORP) and total dissolved solids (TDS) were also explored. Analysis of the nutritional status of the individuals measured through the condition factor index, indicates that fish that inhabit Zapotlán and Cajititlán lakes are significantly smaller and with a poorer condition than those that live in the Calderón and El Salto dams, with the exception of Basilio Vadillo that presents values similar to lakes. Low values of the condition factor in the lakes are associated with low values of temperature and dissolved oxygen, high values for pH and dissolved solids,and low oxide reduction potential, attributed to the discharge of wastewater from the adjacent urban areas, whose organic load affects the quality of the aquatic habitat and impacts the condition of the individuals. In contrast, greater tilapia sizes, of better weight and condition, were captured in El Salto and Calderón dams, where oxygen levels are higher, pH close to neutral, fewer dissolved solids and a positive oxide reductive potential. It is assumed that size, weight and condition factor (K) of the individuals of Orechromis niloticus, vary depending on the quality of the habitat.