Conteúdo gastrointestinal de petréis (Aves: Procellariiformes) no litoral do Rio Grande do Sul, Brasil : análise dos itens alimentares e resíduos poliméricos

• Ano de defesa: 2016
• Autor(a) principal: Perez, Martin Sucunza
• Orientador(a): Fontana, Carla Suertegaray
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Pontifícia Universidade Católica do Rio Grande do Sul
• Programa de Pós-Graduação: Programa de Pós-Graduação em Zoologia
• Departamento: Faculdade de Biociências
• País: Brasil
• Palavras-chave em Português: AVES - RIO GRANDE DO SUL; NUTRIÇÃO ANIMAL; ORNITOLOGIA; ZOOLOGIA
• Área do conhecimento CNPq: CIENCIAS BIOLOGICAS::ZOOLOGIA
• Link de acesso: http://tede2.pucrs.br/tede2/handle/tede/6772

The albatrosses and petrels of the order Procellariiformes play an important role as top predators in marine food webs as they are widespread and usually abundant. In order to analyze the digestive tracts of petrels we conduct beach surveys (n=134) searching for dead birds found between the cities of Torres (29°21’S, 49°44’W) and Mostardas (31°14’S, 50°54’W), Rio Grande do Sul State (RS), southern Brazil, from October 2009 to May 2015. Additionally, specimens that died in the Wildlife and Marine Rehabilitation Center of Federal University of Rio Grande do Sul were included. We analyze the digestive tract of Puffinus gravis (n=21), Procellaria aequinoctialis (n=32), Calonectris borealis (n=34) and Pterodroma incerta (n=61). Specimens of P. incerta were collected after the passage of Catarina Hurricane which hit the coast of Rio Grande do Sul and Santa Catarina states in 2004. Food items of the four species were mainly cephalopod beaks, fish otoliths and eye lenses. In all species, gizzard was the cavity showing the highest percentage of food items reaching 91.8% in P. gravis, 81.3% in P. aequinoctialis, 93.9% in P. incerta and 83.2% in C. borealis. The same cavity showed the highest percentage for frequency of occurrence of polymeric materials attaining 84.4%, 68.7%, 98.3% and 94.2% in P. gravis, P. aequinoctialis, P. incerta and C. borealis, respectively. Among the plastic fragments, high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP) and polyethylene terephtalate (PET) shown the highest percentage of occurrence and numerical frequencies. Among the consumed cephalopods, those belonging to the Oegopsida suborder were the most important cephalopods encountered in the diet. This suborder includes a large number of families, with mostly oceanic species that inhabit great depths. Pelagic cephalopods can be ingested by seabirds through post-spawning die-offs events (when they float), and by eating long-line fisheries discharge (when they catch pelagic and oceanic fishes). We could not identify the fish consumed by P. incerta because the otoliths were worn. In the other petrels studied, all fish consumed and that could be identified are abundant in the coastal and continental shelf platform of RS. Most teleost species present in the stomach contents of these birds are trawling fisheries discards in southern Brazil, as they are incidentally caught or for not having commercial value. Gravimetric tests used to identify the consumed polymers indicated that HDPE, LDPE and PP have low densities and can float on water, reinforcing the hypothesis that Procellariiformes can ingest plastic residues confounding it with prey. The high consumption of manufactured materials highlights the degradation of the oceans and is an important concern for migratory and endangered species conservation.