Data/hora: 01/06/2024 18:26:38

Provedor de dados: | 20
País: | Belgium

Título:

Ecología trófica del gatuzo, Mustellus schmitti (Springer 1939), en el Mar Argentino

Trophic ecology of the narrownose smoothhound shark Mustellus schmitti (Springer 1939), in the Argentine Sea

Autores: | Belleggia, M.
Data: | 2013-04-18
Ano: | 2012
Palavras-chave: | Feeding behaviour; Trophic levels; Stomach content; Predator prey interactions; Ontogeny; Shark fisheries; Mustellus schmitti; Polychaeta; Marine environment.
Resumo: | The narrownose smoothhound shark Mustelus schmitti is a benthic shark distributed from Florianópolis (27°S, Brazil) to Deseado River Estuary (47º45´S, Argentina) and occurs from shallow waters to 120m. This Thesis describes the feeding ecology of narrownose smoothhound shark M. schmitti in northern Argentinean Continental Shelf and is structured in four chapters. Chapter 1 contains an introduction and includes purpose, theory and concepts. In Chapter 2, the food habits of M. schmitti were studied based on analysis of stomach contents from specimens collected during the years 2008-2011. Of a total of 959 stomachs sampled during this period, 944 (98,43%) contained food. Prey items were identified to the lowest possible taxonomic level, counted and weighted. The analyses revealed that the species fed mostly on polychaetes according to %F, %N, %IRI and %PSIRI, followed by Brachyura crustaceans, fishes and hermit crabs. Moreover, Generalized Linear Models revealed ontogenetic and spatiotemporal shift in the diet of the narrownose smoothhound shark M. schmitti. The trophic level is the position of an organism within the food web; it was 3,6 during 2008-2011. In Chapter 3 stomach contents data collected from fifteen research cruises carried out by INIDEP from 1986-1994 were analyzed. Of the 1009 stomachs analyzed during the older period, 902 (89,39%) contained prey items. The narrownose smoothhound shark M. schmitti fed mostly on Brachyura crustaceans, followed by polychaetes and fishes. Generalized Linear Models, merging stomach contents data from contemporary and older periods, revealed that the consumption of the main prey groups varied over the last 25 years. The trophic level was 3,85 during 1986-1994. As fishing is a major form of ecological disturbance to marine communities throughout the world, these changes in the trophic relationships are probably consequence of trawl fisheries and the disturbance of bottom trawls through the study period. Chapter 4, explores qualitative and quantitatively the dentition of the narrownose smoothhound shark M. schmitti by sex and ontogenetic development. The values of tooth replacement rates were estimated and a brief discussion of the presumed relationship between dentition and the feeding behavior previously analyzed is included. Chapter 5, includes a brief final conclusion of the whole Thesis that aims to provide a global vision about the feeding ecology of M. schmitti. Finally, an appendix provides an illustrated guide to identify the different species of polychaetes that might be encountered in the stomachs contents of benthic species from the northern Argentinean Continental Shelf (35°S -41°S).
Tipo: | Theses and Dissertations
Idioma: | Espanhol
Identificador: | http://hdl.handle.net/1834/4775

Editor:

UNMdP

Mar del Plata (Argentina)

Formato: | 228 p.
Fonte: | http://www.oceandocs.org/license