LAUSR

To better understand the ecology and biology of the curimba in the Paraná River and to provide basic information for fisheries stock assessment, this study address the following questions: Do age estimates derived from otoliths and scale agree for Prochilodus lineatus? What is the growth trajectory for curimba in the upper Paraná River? What is the age structure of the population in the upper Paraná River? Is there any evidence of spatial stratification in population age structure or growth? Fish were sampled in the Paraná, Ivinhema and Baia Rivers and in the Itaipu reservoir from 2012 to 2013. The otoliths showed one to eight annuli and the scales had one to six circuli. The agreement between the otoliths was higher (about 80%) than between the scales (about 70%). The agreement between otolith and scale readings was significantly low (about 40%). Using a von Bertallanfy growth function, the asymptotic standard length (L∞) for the whole population was estimated to be 68.84 cm, the growth coefficient (K) was estimated to be 0.15 year−1 and t0 was assumed to be 0 year. There was substantial variation in length-at-age in most but the youngest ages, in the intermediate ages there was a mix of individuals from various locations with markedly different growth rates. Our data also suggest a recruitment failure in 2012 and 2013, due to the lack to flooding, which also caused lack of habitat connectivity.