<b> Influence of cage farming on feeding and reproductive aspects of <i>Pimelodus maculatus</i> Lacépède, 1803 (Siluriformes: Pimelodidae) in the Chavantes reservoir, Brazil </b> - doi: 10.4025/actascibiolsci.v36i1.

Abstract

ABSTRACT. This study evaluated the diet and reproductive aspects of the population of Pimelodus maculatus around net cage fish farming in order to assess the possible impacts of this activity. Monthly collections were performed from March 2008 to February 2009 on two populations: one close to the net cages (NC) and one from an area not influenced by these cages denominated the "reference site" (RS). Results of the Alimentary Index (AI), Gonadosomatic Index (GSI), reproductive potential and histological analysis were obtained for both NC and RS populations. The population from NC used leftover food (ration) that escapes from net cages as the main food item (99.3%). For the RS population, the detritus item was the more important food source (51.7%). The Detrended Correspondence Analysis (DCA) showed that the use of food resources was different between the two sites. The reproductive period of the species (indicated by the GSI) revealed that the population of the NC showed an extended reproductive period compared to RS. The histology of the ovaries indicated that the specimens in the NC were spawning capable. This study indicates that fish farming activities influence the species P. maculatus in the Chavantes reservoir by adding a new resource to the food web.Keywords: fish, biology, neotropical reservoir, Paranapanema river.Influência de uma piscicultura em tanques-rede sobre a alimentação e aspectos reprodutivos de Pimelodus maculatus Lacépède, 1803 (Siluriformes: Pimelodidae) no reservatório Chavantes, Brasil RESUMO. O objetivo deste estudo foi avaliar a dieta e os aspectos reprodutivos da população de Pimelodus maculatus residentes ao redor de tanques-rede. Os peixes foram coletados mensalmente, de março/2008 a fevereiro/2009, a partir de duas populações: uma próxima ao ambiente de tanques-rede (NC) e a outra em uma área não influenciada pelos tanques-rede, denominada área de referência (RS). As análises do Índice Alimentar (AI), Índice Gonadossomático (IG), Potencial Reprodutivo e Histologia das gônadas foram realizadas para as populações das duas áreas amostradas. As populações de NC utilizaram-se de restos de ração que escapam dos tanques-rede, como principal fonte alimentar (99,3%). Para a população do RS, os detritos foram a fonte mais importante (51,7%). A análise de Correspondência Destendenciada (DCA) mostrou diferenças na utilização dos recursos alimentares entre as duas populações. O período reprodutivo das espécies (indicado pelo IG) mostrou que a população do NC apresentou maior período reprodutivo em relação às populações do RS. A histologia dos ovários indicou que os espécimes de NC estavam aptos à desova. Este estudo adverte que as atividades de piscicultura influenciam a referida espécie na represa de Chavantes pela adição de um novo recurso para a cadeia alimentar.

Cage fish farm act as a source of changes in the fish community of a Neotropical reservoir

“…Our results support that the favoring of few species around cage fish farms, contribute to spatial differences in fish community between fish farm and reference sites, as demonstrated by Permanova analysis. This favoring is supported by concomitantly studies performed in the same cage fish farms with the same fishes used in this study showed that opportunistic and omnivore species, like A. affinis, A. lacustris, I. labrosus, P. maculatus and S. insculpta consume the uneaten food released by fish farms, causing alterations in their numeric abundance, condition factor and reproductive period (Brandão et al, 2014;Brandão et al, 2013;Brandão et al, 2012;Ramos et al, 2013).…”

“…Historically, river damming has induced impacts like restructuring of fish communities (Araújo et al, 2013), depletion of rheophilic fishes, proliferation of small and sedentary species (Agostinho et al, 2007;Nobile et al, 2016) and introduction of non-native fish species (Gois et al, 2015). Further, the recent expansion of aquaculture in cage fish farms can act as a new source to impact fish communities in large reservoirs in Neotropical region (Brandão et al, 2014;Brandão et al, 2013;Brandão et al, 2012;Ramos et al, 2013).…”

Cage aquaculture in Neotropical waters promotes attraction and aggregation of fish

“…For the lentic environments, in which cages are usually installed, there are reports of drastic changes in trophic structure and in the balance of phytoplankton (Borges, Train, Dias, & Bonecker, ; Kashindye et al, ), zooplankton (Dias, Takahashi, Santana, & Bonecker, ; Terziyski, Tzavlova, Kalchev, & Iliev, ), benthos (Kashindye et al, ) and fish species (Demétrio, Gomes, Latini, & Agostinho, ; Strictar‐Pereira, Agostinho, & Gomes, ). Specifically, for ichthyofauna, the high availability of artificial food is responsible for the attraction and aggregation of fish in the vicinities of the cages resulting in changes in the structure and functioning of communities (Brandão, Santana, Ramos, & Carvalho, ).…”

“…The aggregation of fish near the cages is already recognized (Brandão et al, ); however, the mechanisms and processes responsible for this aggregation are still unknown, and more studies are needed to determine its degree of impact and its importance to wild populations. Based on this, the present study seeks to evaluate spatial and temporal variations in the fish assemblage associated with tilapia caging in a Brazilian reservoir.…”

Dietary changes and histophysiological responses of a wild fish (Geophagus cf. proximus) under the influence of tilapia cage farm

“…Studies on cage fish farm in freshwater systems have demonstrated changes in wild fish species on reproductive aspects of Pimelodus maculatus (Brandão et al, 2014) and influence parasitological factors in Plagioscion squamosissimus (Ramos et al, 2014). In addition, interference in settlement patterns has also been reported (Agostinho et al, 2007;Mallasen et al, 2012) due to the input of organic matter from cages and the introduction of non-native species (Zanatta et al, 2010), mainly through fish escaping from cultivation (Agostinho et al, 2007).…”