title: Trophic ecology and bioindicator potential of the North Atlantic tope shark.
abstract: Sharks are top marine predators vital in maintaining ecosystem health and food web structure. In order to assess tope shark (Galeorhinus galeus) trophic ecology, stable isotope ratios and trace metal concentrations in muscle tissue were determined, according to size and gender, for 124 individuals caught within the Mid-Atlantic region. Data was complemented and analysed according to previous stomach content information and compared with studies performed in the North East Atlantic. Our results revealed that tope sharks fed at a low trophic level and within a more pelagic-based food web when compared with other North Atlantic regions. MixSIR application reflected its piscivorous diet and study area topography, oligotrophic waters and volcanic nature, suggesting the occurrence of a Mid-Atlantic tope shark population. Considering a non-anthropogenic volcanic source for observed metal contents, the results reflect bioaccumulation and suggest biomagnification processes for As and Hg. These metals exceeded legislated maximum limits for some countries with a maximum of 28.98 ± 1.26 and 0.57 ± 0.01 mg kg(-1) wet weight, respectively, increasing significantly with size for both males and females. Conversely, Cr, Rb and Zn were relatively stable while Cd and Pb were not detected. Hg and Se were strongly correlated, suggesting a Se toxicity mitigation role. Given the tope shark travel capacity and the results obtained, the species may be used as a Mid-Atlantic bioindicator of environmental quality.
authors.affiliation: CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Pólo dos Açores - Departamento de Biologia, Universidade dos Açores. Rua Mãe de Deus, 58, 9500-801 Ponta Delgada, Açores, Portugal. Electronic address: biol.paulo@gmail.com.
authors.forename: Paulo
authors.initials: P
authors.lastname: Torres
authors.affiliation: CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Pólo dos Açores - Departamento de Biologia, Universidade dos Açores. Rua Mãe de Deus, 58, 9500-801 Ponta Delgada, Açores, Portugal.
authors.forename: Regina Tristão
authors.initials: RT
authors.lastname: da Cunha
authors.affiliation: CBA, Centro de Biologia Ambiental - SIIAF, Stable Isotopes and Instrumental Analysis Faculdade de Ciências da Universidade de Lisboa - Departamento de Biologia Vegetal, Edifício C2 - Sala 2.1.16. Campo Grande, 1749-016 Lisboa, Portugal.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Maia
authors.affiliation: CVARG, Centro de Vulcanologia e Avaliação de Riscos Geológicos - Departamento de Biologia, Universidade dos Açores, Apartado 1422, 9501-801 Ponta Delgada, Açores, Portugal.
authors.forename: Armindo
authors.initials: A
authors.lastname: Dos Santos Rodrigues
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D004032:Diet / Q000706:statistics & numerical data; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods*; D005260:Female; D020387:Food Chain; D005766:Gastrointestinal Contents; D008297:Male; D008670:Metals / Q000378:metabolism; D009132:Muscles / Q000378:metabolism; D012754:Sharks / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D008670:Metals; D014874:Water Pollutants, Chemical
keywords: Bioaccumulation; Galeorhinus galeus; Mid-Atlantic; Stable isotopes; Trace metals