Simpatria entre duas espécies de peixes invertívoras de Bertioga (SP)
Abstract
The objective of this work was to verify the feeding overlap between two caracids
fishes, Hollandichthys multifasciatus and Mimagoniates microlepis, in 11 coastal
streams in Bertioga (SP), as well as to describe the diet of both species and verify the
occurrence of seasonal and spatial variation over a year. The sampling sites are located
in the municipality of Bertioga (SP). The samplings were monthly done from may/2016
to april/2017 with the aid of electric fishing. The specimens collected were anesthetized
and dissected, in which the stomachs were removed and stored in ependorf for future
analysis. The food items were divided into 17 categories according to their origin:
allochthonous, autochthonous and unknown. The frequency of occurrence and volume
of each item ingested was combined to form the food index. Bray-Curtis similarity,
followed by clustering, was used to identify spatial-temporal variations in fish diet. A
redundancy analysis was used to verify the influence of environmental data on the items
consumed. The Morisita index was calculated to identify the degree of food overlap
between the two species. Both species demonstrated an invertivore feeding habit with
tendency to terrestrial invertivory. The sazonal variation observed for H. multifasciatus
and M. microlepis occurred in the volume of adult terrestrial insects ingested. Also, a
diet shift was observed among streams, the fishes category became the most consumed
by H. multifasciatus in streams 5 and Decapoda in streams 7 and 11, and M. microlepis
fed large quantities of immature aquatics insects in strems 5 and 9. The RDA showed
that environmental variables that best explained the axes and influencied the most in the
diet composition were gravel and litter. The food overlap, in gerenal, was moderate
between periods, streams and stretches, except strems 3, 4 and 10 which presented high
overlap.