Polyphasic growth in fish: a case study with Corydoras paleatus (Siluriformes, Callichthyidae)

Crescimento polifásico em peixes: estudo de caso com Corydoras paleatus (Siluriformes, Callichthyidae)

ABSTRACT

A weight-length relationship was established for Corydoras paleatus (Jenyns, 1842) (Siluriformes, Callichthyidae) (n=596) from samples taken in November-December 2009 and March-April 2010, in Pinguela Lagoon (29°46'57"S; 50°11'16"W), Rio Grande do Sul, Brazil. The species showed a polyphasic allometric growth pattern, each stanza described by an independent power equation controlled by a switch function: W = a₁L^b1 ∙ (1 + e^Rsc ∙ ^(L-SCP))-1 + a₂L^b2 ∙ [1 - (1 + e^Rsc ∙ ^(L-SCP))-1] ; where W is the expected weight for a specific length L, a₁ and a₂ are the proportionality coefficients for stanzas 1 and 2, b₁ and b₂ are the allometric coefficients for stanzas 1 and 2, R_sc is the stanza changing rate for the switch function and SCP is the stanza changing point for the switch function. The stanza changing point was estimated as 5.28 cm, corresponding with the length at first maturity for this species L_mat (5.29 cm). Our data suggest that a complex growth pattern can be in nature, and perhaps not often identified because trends are obscured by natural variability.

KEYWORDS
Allometric growth; length at first maturity; reproduction; sexual maturity; length-weight relationship