GROWTH CURVES OF LARVAE AND POSTLARVAE OF PINK SHRIMP, FARFANTEPENAEUS PAULENSIS

R. Soares, F. D'Incao, S. Peixoto, T. Silva

Abstract:

The Von Bertalanffy (1938) model has been widely used to describe penaeids shrimp growth. However, initial development phases (nauplii, protozoea, mysis and postlarvae) seem to follow a different growth model. The objective of this study was to compare different growth models to determinate which one represents the best adjust to initial life phases of F. paulensis. The growth curves were built using measures of carapace length (CL) of captive shrimps of 1 to 57 days of life. In the nauplii phase the total length was measured. Shrimps were obtained by random sampling from a larviculture conduced in experimental boxes (180 liters), temperature 24 – 2?C, salinity 28 - 31 and feeding with Artemia nauplii. A total of 284 measures were recorded using a biological microscope Olympus BX-50.

Von Bertalanffy Þ L_t = L_¥{1-e^-K(t-t0)}

Logística Þ L_t = L_¥/1+c₀ e^(-Kt)

Gomprtz Þ L_t = L_¥ exp (-c₀ e^-Kt)

t = age, L_t = length in age t;

K = growth coefficient;

L_¥ = maximum length (assymptotic);

t₀ = hypothetical age in which the animal has size equal to zero;

c₀ = mathematical adjustment coefficient;

r = correlation coefficient

Growth curves were calculated using the Microsoft Excel Solver tool v. 7.0. The Von Bertalanffy and Gompertz’s presented the best adjustment (r>0.95) to CL observed. However in the Gompertz’s model we observed that the initial inflection point provides better adjustment than Bertalanffy’s growth model. The asymptotic length estimated by Gompertz’s model (L_¥ ? = 42.9 mm), was similar to the one calculated for F. paulensis adult population. However the growth coefficient (k=5.8) was considered overestimated, probably due high growth rate characteristic of the initial penaeid life stages. Although Von Bertalanffy’s model has been used with success for F. paulensis juvenile and adult, Gompertz’s model is more effective to early stages. These results suggest that one single mathematical model could not be applied to describe shrimp growth from hatching to adult size.

(Laboratorio de Crustáceos Decapodos, Departamento de Oceanografia, Fundaçao  Universidade do rio Grande – FURG, CP 474, Rio Grande, Brasil, e-mail: Roberta@mikrus.com.br)

home