Abstract
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 = a1Lb1 ∙ (1 + eRsc ∙ (L-SCP))-1 + a2Lb2 ∙ [1 - (1 + eRsc ∙ (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, Rsc 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 Lmat (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.
Highlights
Froese et al (2014) made a recent revision on this subject, including data from 1821 species with available information. These authors found a general pattern concerning fish weight-length relationship (WLR): (1) as a general average, fish present positive allometric growth factor (b > 3); (2) the allometric factor depends on the fish body shape, ranging from 3.12 for elongated fish to 3.01 for short and deep fish
We aimed to estimate the length at first maturity (L50) according to the Gonadossomatic Index (GSI) using a mathematical approach (Marques et al, 2007; Fontoura et al, 2009) and identify if a polyphasic growth pattern is present for C. paleatus, verifying a possible relationship between the stanza changing length and aspects of the fish biology, as the attainment of sexual maturity
Samples of C. paleatus were taken in November – December 2009 and March – April 2010, by means of a beach seine net (50 m long, 3 m high, and 5 mm mesh size) in the Pinguela Lagoon (20°46’57”S; 50°11’16”W; southern Brazil)
Summary
Crescimento polifásico em peixes: estudo de caso com Corydoras paleatus (Siluriformes, Callichthyidae). The parameters of the WLR, as the proportionality coefficient (a) and the allometric coefficient (b) could inform several aspects of the fish biology, as the general growth pattern or seasonal changes in the fish condition (Froese, 2006). Froese et al (2014) made a recent revision on this subject, including data from 1821 species with available information These authors found a general pattern concerning fish WLR: (1) as a general average, fish present positive allometric growth factor (b > 3); (2) the allometric factor depends on the fish body shape, ranging from 3.12 for elongated fish to 3.01 for short and deep fish. As identified by Bervian et al (2006) and Fontoura et al (2010), the growth pattern of fish could be too complex to be described by a simple power function, as food source and quality is not constant in nature, and adaptation to several aspects of the fish life cycle, as habitat shift, migration, ontogenetic shift of feeding habitats and reproductive strategies can change the energetic budget, Iheringia, Série Zoologia, 106: e2016017
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