Abstract

SCHULZ, Uwe Horst  and  LEAL, Mateus Evangelista. Effects of stocking density on dispersal behavior of Brazilian freshwater dourado (Salminus brasiliensis) in a subtropical river headwater. Neotrop. ichthyol. [online]. 2012, vol.10, n.2, pp. 409-415.  Epub May 10, 2012. ISSN 1679-6225.  http://dx.doi.org/10.1590/S1679-62252012005000001.

Juvenile freshwater dourados (Salminus brasiliensis Cuvier) were stocked in two batches of different size (61 and 133 individuals) with a time lag of 41 days in the headwaters of the Sinos River. A subsample of 25 fish was radio-tagged. Released juveniles displayed a density dependent dispersal pattern. During the first ten days mean covered distance of tagged batch 1 individuals (low density) was approximately 24 m d^-1, while batch 2 individuals (high density) moved 296 m d^-1. Activity of batch 1 fish increased after the release of batch 2 and remained high (459 m d^-1) until 90 days. Activity of batch 2 fish during this period was in same range. After this period, activity levels of both batches decreased to about 60 m d^-1. Increased movements in higher density condition are seen as a result of interspecific competition. The mean covered distances per day remained high until stocked individuals become established in their new habitat.

Keywords : Density dependence; Dispersal; Intraspecific competition; Movements.