Aging and growth parameter from the Piaractus mesopotamicus (pacu) from the Cuiabá river, Mato Grosso, Brazil

Abstract

ABSTRACT. This study has aims to determine the age and to estimate the growth parameters using scales of the species. Individuals of Piaractus mesopotamicus (Holmberg, 1887) used in this study were captured in the commercial fishery conducted in the region, along the year 2006. The model selected to express the growth of the species was the von Bertalanffy Sl= Sl∞* [1-exp -k(t-to) ]. To determine if scales are suitable for studying the growth of pacu, we analyzed the relation between standard length (Sl) and the radius of the scales through linear regression. The period of annuli formation was determined analyzing the variations in the marginal increment and evaluating the consistency of the readings through the analysis of the coefficient of variations (CVs) for the average standard lengths of each age (number of rings) observed in the scales. The relationship between Ls of the fish and the radius of the scales showed that scales can be used to study the age and growth of P. mesopotamicus (R= 0.79). CVs were always below 20%, demonstrating the consistency of the readings. Annuli formation occurred in February, probably related to trophic migration that occurs in this month in the region. Equations that represents the growth in length obtained for P. mesopotamicus are Sl=50.00* [1-exp -0.18(t-(-3.00) ] for males and Sl=59.23*[1-exp -0.14(t- (-3.36) ] for females. The growth parameters obtained in this study were lower compared to other studies previously conducted for the same species and can related to overexploitation that species is submitted by fishing in the region. These values show also that females of pacu attain greater asymptotic length than males that growth faster. KEYWORDS.Growth rings, scales, von Bertalanffy model, Ford-Walford. -k(t-to) ]. Para saber se as escamas são apropriadas para estudos de crescimento do pacu, nós analisamos a relação entre o comprimento padrão (Cp) e o raio das através de regressão linear. O período de formação dos anéis foi determinado analisando as variações no incremento marginal e a consistência das leituras foi avaliada através da análise do coeficiente de variação (CVs) do comprimento padrão médio para cada idade (número de anéis) observado nas escamas. A correlação entre o Ls do peixe e o raio das escamas mostrou que as escamas podem ser utilizadas para estudos de crescimento do P. mesopotamicus (R= 0.79). Os CVs foram sempre abaixo de 20% demonstrando consistência nas leituras. A formação dos anéis ocorreu em fevereiro provavelmente relacionada com a migração trófica que ocorre neste mês na região. As equações que representa o crescimento em comprimento obtidas para o P. mesopotamicus são: Cp=50.00* [1-exp -0.18(t-(-3.00) ] para machos e Cp=59.23*[1-exp -0.14(t- (-3.36) ] para fêmeas. Os parâmetros de crescimento encontrados neste estudo foram mais baixos quando comparados com outros estudos para a mesma espécie realizados anteriormente e pode estar relacionado com "overexplotation" pela pesca que a espécie é submetida na área. Esses valores...

Individual, spatial and inter-sex variation in somatic growth: a study of Piaractus mesopotamicus (Characiformes: Serrasalmidae), a long-distance freshwater Neotropical migratory fish

“…The maximum age of individual P. mesopotamicus was 5 years. Vaz (2001) found a similar age structure (5 years) based in scales readers, and Ambrósio et al (2014) observed the maximum of seven growth rings in the scales. Based on this study and previous (Vaz, 2001;Ambrósio et al, 2014) the estimative from maximum age indicates a short life cycle for P. Mesopotamicus.…”

“…The best model showed individual and sex effect on growth parameters. The sex effect in fish species, with females being larger than males or vice versa (Rljnsdorp, Ibelings, 1989;Imsland et al, 1997;Ambrósio et al, 2014) is not rare to detect. The difference in body length between males and females is related to variation in growth parameters (Morita et al, 2015).…”

“…Consequently, seasonal growth variation was inferred from the relative widths of the two seasonal increments on the otoliths (Duponchelle et al, 2007). Ambrósio et al (2014) evaluated the deposition frequency of P. mesopotamicus growth rings in the Cuiabá River headwaters, and found that increment deposition was annual. Studies in seasonally-flooded environments suggest that the timing of ring formation in calcified and mineralized structures is annual and occurs during the dry season Duponchelle et al, 2007).…”

“…Consideration of the influence of differences in behaviour and differential investment in reproduction and growth between the sexes has permitted a better understanding of autoecology and dynamics of fish stocks (Araújo, Haimovici, 2000). Studies investigating the role of sex as a factor in growth models and methods for back-calculating size have shown that much of the variation between individuals is related to sex (Kielbassa et al, 2011;Ambrósio et al, 2014).…”

“…Growth rates for P. mesopotamicus developed in the Cuiabá River, Mato Grosso, and using scales, found variation between sex k=0.14 year -1 and L ∞ 50 cm for females and k=0.18 year -1 and L ∞ 59.23 cm for males. The maximum age at capture was eight years (Ambrósio et al, 2014). However, stocks in the Cuiabá River system are overexploited (Vaz, 2001;.…”