COMPARING GROWTH CURVES

COMPARING GROWTH CURVES - Computer Application for assistance in comparing growth curves of fish stocks *

Ana Isabel Borges, ESTG IPP, aib@estgf.ipp.pt

Maria de Fátima Carvalho, FCUP, mpcarval@fc.up.pt

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In order to guide marine researchers while comparing fish growth curves, a user-friendly interface was created in Microsoft Excel environment, written in VBA Language. Nominated "Comparison of Growth Curves", it consists of the following three parts:

(I) "Adjust to growth models", which, from the length-at-age data, makes adjustments to three of the most well-known growth models - Von Bertalanffy, Logistic and Gompertz - taking advantage from the nonlinear least square method;

(II) "Likelihood ratio test", useful to compare statistically, two apparently similar growth curves, applying the likelihood ratio test;

(III) "Punctual comparison", helpful to compare absolute and relative growth rates, average rate of change or even simple length-at-age or age-at-length functions. Meanwhile one has the opportunity to output enlightening graphics along the whole process. The existence of dialog boxes that clarify both the mathematical procedure supporting the study and the interpretation of the results turns the interface into a valuable, and easy to handle, tool. The interface was tested in a few samples and the results suggest that the innovative implementation of a previous careful selection of features will improve the program's potential

*This software should be referred as:
BORGES, A., M. CARVALHO & P. SANTOS (2010). Computer Application for assistance in comparing growth curves of fish stocks. International Statistical Ecology Conference 2010, Univ. Kent, UK.