Habitat simplification affects nuclear-follower foraging association among stream fishes

Abstract

Nuclear-follower interaction is a particular kind of interspecific foraging association that includes a nuclear species, which dig in or inspect the bottom, and follower species, which access the food items made available by the nuclear. In this study we examined the effect of habitat structure on nuclear-follower relationship in a stream of Bodoquena Plateau, Central-West Brazil. Foraging associations were registered while snorkeling in 24 observation sessions, totaling six hours in unaltered and altered sites. Overall, 272 nuclear-follower associations were registered, having four species acting as nuclear and seven as followers. The dominant nuclear species were different in each site. Prochilodus lineatus was the main nuclear species in the altered site and Leporinus macrocephalus in the unaltered site. The richness of follower species was similar between sites, however, follower species abundance per interaction were significantly higher in the unaltered site than in the altered site. These differences seem to be a consequence of the alterations in assemblage composition and feeding behavior of the nuclear species that presumably are affected by different substrate composition and food availability between the structurally distinct areas.A interação nuclear-seguidor é um tipo particular de associação alimentar interespecífica que envolve uma espécie nuclear, que revolve ou vasculha o substrato, e espécies seguidoras, que acessam os itens alimentares disponibilizados pela atividade do nuclear. Neste estudo investigamos o efeito da estrutura do habitat sobre essa interação em um riacho no Planalto da Bodoquena, Centro-Oeste do Brasil. Foram registradas 272 interações durante 24 sessões de observação subaquática em áreas estruturalmente inalteradas e alteradas. A espécie nuclear dominante diferiu entre as áreas. Prochilodus lineatus foi a espécie nuclear dominante das áreas alteradas, enquanto que Leporinus macrocephalus foi a espécie nuclear dominante nas áreas inalteradas. A riqueza de espécies seguidoras por interação não diferiu entre as áreas, entretanto a abundância de seguidores foi maior nas áreas inalteradas do que nas alteradas. Essas diferenças parecem ser consequência das modificações na composição da comunidade e no comportamento alimentar das espécies nucleares que são, por sua vez, decorrentes das diferenças na composição do substrato e disponibilidade de alimento entre as áreas estruturalmente distintas.

Predictive factors of species composition of follower fishes in nuclear-follower feeding associations: a snapshot study

“…Although such interactions are commonly recorded in marine environments (Strand, 1988;Lukoschek & McCormick, 2000;Sazima et al, 2006;Sazima et al, 2007), there are studies on such interactions in tropical freshwater environments as well, mostly in tropical waters (e.g., Baker & Foster, 1994;Leitão et al, 2007;Ott, 2007;Teresa & Carvalho, 2008;Garrone-Neto & Sazima, 2009;Teresa et al, 2011). Despite efforts to describe this type of association, knowledge of its modulating factors is still incipient (see Sazima et al, 2005;Krajewski, 2009).…”

“…Thus, the features directly or indirectly associated with sediment suspension would be important for the occurrence and variation in the composition of followers. Recently, Teresa et al (2011) showed that different substrata types may interfere in the profile of this association type, influencing the composition of nuclear and follower species. For example, stream stretches with unconsolidated substrate (sand, mud) and with apparently greater availability of organic matter would show a high sediment suspension capacity during the feeding activity of benthivorous fishes, thereby attracting larger groups of followers (Teresa et al, 2011).…”

“…Most records of feeding associations in freshwater were made in Neotropical headwater streams (Leitão et al, 2007;Teresa & Carvalho, 2008;Teresa et al, 2011, but see Ott, 2007. These environments feature a mosaic of environmental conditions (Frissel et al, 1986) and many of them have high variability in microhabitats, heterogeneous bottom composition, high water transparency and species diversity, conditions that favor the study of the modulating factors of such associations.…”

“…The streams of the Serra da Bodoquena, in particular, situated in the Central-West region of Brazil, share the above-mentioned characteristics (Casatti et al, 2010). Moreover, recent studies show that significant part of the species living there participate in feeding associations (e.g., Teresa et al, 2011). In this context, we conducted a snapshot study in a stream of the Bodoquena region as a model to evaluate the factors that may influence the composition of follower species in the nuclear-follower associations.…”

Activity and habitat use of two species of stingrays (Myliobatiformes: Potamotrygonidae) in the upper Paraná River basin, Southeastern Brazil

“…In Brazil, research into the behavior of fish in the natural environment is recent but has been steadily growing from year to year, normally focusing on species of teleostean fish (Sazima, 1986;Casatti & Castro, 1998;Sabino, 1999;Teresa et al, 2011). Information of this kind is scarce when dealing with elasmobranchs, particularly with stingrays of the family Potamotrygonidae (Castex, 1963;Achenbach & Achenbach, 1976;Rosa, 1985).…”