Effect of seasonality on the reproduction of Characiformes fish in a Neotropical river

ABSTRACT

Effect of seasonality on the reproduction of Characiformes fish in a Neotropical river. The knowledge of reproductive tactics is essential to understand the strategies of the fish life cycle, as well as to guide management and conservation measures. Thus, the present study aimed to verify the aspects related to the reproduction of seven species of the Sorocaba River, the largest tributary of the left bank of the Tietê River, and very important for the maintenance of fish species in the middle section of that river. Monthly collections were carried out from September 2010 to September 2012 at two points located in the middle and lower Sorocaba. The species studied were: Astyanax lacustris (Lütken, 1875), Psalidodon cf. fasciatus (Cuvier 1819), Megaleporinus obtusidens (Valenciennes 1837), Parodon nasus Kner, 1859, Prochilodus lineatus (Valenciennes, 1837), Salminus hilarii Valenciennes, 1850 and Triportheus nematurus (Kner, 1858). There was a significant correlation between species capture and temperature (Spearman r = 0.79, p = 0.0001) and rainfall rate (Spearman r = 0.60, p = 0.00014). There was also a significant correlation between the maturing and mature stages, temperature and rainfall rate, showing the importance of these factors in regulating the reproductive cycle of the species in the studied places. A pattern of reproductive seasonality was evidenced, which was confirmed by the medians of the Gonadosomatic Index (IGS) over the months. The migratory species P. lineatus and S. hilarii, had their peak of reproduction at the time of the riverʼs flood. In the months from November to March, the highest reproductive activity was registered, resulting from the interaction between biotic and abiotic factors (temperature and rainfall rate), since these factors act in the maturation of the gonads.

KEYWORDS
Rheophilic fish; spawning; gonad maturation; Sorocaba river