Multivariate Analysis of Growth in Juvenile Tilapia Oreochromis aureus

A multiple regression analysis of growth in juvenile tilapia Oreochromis niloticus and 0. aureus (Cichlidac) is presented based on experiments conducted from 1984 to 1987 in recirculating systems a t the Tilapia Genetics Laboratory of the University College of Swansea. Wales, UK. One regression model was derived for 0. niloticus, one for 0. aureua and one for both species jointly. Overall fit, although not high, was significant (R2 = 0.500, 0.493 and 0.423, respectively for n = 2,446, 3,631 and 6,077, respectively). A surprisingly high number of variables were found to correlate with growth rate; of 19 hypothesized variables (17 of which were dummies, coded 0 or 1). only 4 were not signilicant in the 0. niloticus model, 2 in the 0. aureus model and 4 in the joint modcl (a = 1%). The discussion emphasizes the usefulness of dummy variables for decomposing into primary factors the impacts on fish growth of complexly integrated brecding experiments and rearing systems.