Abstract
Brazilian laws allow the catch of some species as ornamental fish; however, in the absence of biological information, such catch can threaten species conservation. Therefore, this study aimed to offer population and reproductive information about Farlowella hahni in streams of the Ivinhema River Basin, Upper Paraná Basin. To accomplish this, a total of 165 F. hahni individuals were analyzed, including 109 females and 48 males, resulting in an important sex ratio difference from 1:1 (χ 2=19.97; p<0.001), indicating a predominance of females throughout the year. Females reach higher standard length than males. Males presented isometric Length-Weight Relationships, while females have positive allometric growth. Gonadosomatic index presented higher values from October through December. The mean fecundity was 100.3±36.4 of vitellogenic oocytes and was positively correlated with standard length (r=0.51; p=0.01). The data presented herein are the first for this species and suggest a need to carefully manage the F. hahni population, considering its low abundance and fecundity.
Highlights
Armored catfish are a highly diverse group
The sex ratio difference from 1:1 is considered a disadvantage in sexual competition, with the members of the predominant sex transmitting their genes with lower frequency to the generation
The predominance of females has been reported for other small loricariid species in the Neotropical region, e.g., Neoplecostomus microps (Levitan, 2005; Braga et al, 2008), Pareiorhina rudolphi (Braga et al, 2009), Loricariichthys castaneus (Gomes et al, 2011) and Loricarichthys platymetopon (Suzuki et al, 2000)
Summary
Armored catfish are a highly diverse group. Despite a growing number of taxonomic studies on this group in the Neotropical region (Albert and Reis, 2011), few ecological aspects of Neotropical species are known. The higher taxonomic diversity of this group is reflected in its morphology (Lujan et al, 2012) and habitat. Streams are inhabited primarily by small-sized species that present little, or no, commercial. 286 286/293 value and have restricted distribution. They are largely dependent on riparian vegetation (Castro and Menezes, 1998). The Upper Paraná Basin provides primary habitat for this F. hahni, but it is the region with highest human density in Brazil. We see growing deforestation, even in riparian forest (Súarez et al, 2011)
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