489 



Abstract — Feeding habits and feed- 

 ing strategy of red rockfish iScbastes 

 capensisi were studied from fish cap- 

 tured along most of the range of this 

 species in coastal waters of South 

 America. Stomach contents of 613 

 individuals, collected during 2003, 

 were analyzed. Fish were obtained 

 from six locations along the Chil- 

 ean (23°S to 46''S) and Argentinian 

 (43°S) coasts. The main prey items 

 were Mysidacea (75. 06*5 IRI), Osteich- 

 thyes (6.29% IRI ),and Rhynchocinetes 

 typus (6.03% IRI I. Predator sex and 

 size did not significantly affect the 

 diet, but significant differences were 

 found between locations. Four geo- 

 graphical areas, discriminated by 

 prey occurrence and frequencies, 

 were determined: three on the Pacific 

 coast and one on the Atlantic coast. 

 These areas correspond roughly with 

 biogeographic zones described for the 

 Chilean and southern Argentinian 

 coasts. The feeding strategy index 

 (FSI) indicated a specialized feed- 

 ing strategy for S. capensis for most 

 of its range. However, the FSI does 

 not include the behaviour of a preda- 

 tor, and the FSI must be interpreted 

 carefully for fishes like S. capensis 

 that are passive ambush feeders. 

 The abundance and availability of 

 different prey may explain both the 

 geographic differences in dietary com- 

 position and the specialized feeding 

 strategy of S. capensis. 



Manuscript submitted 18 November 2004 

 to the Scientific Editor's Office. 



Manuscript approved for publication 



1 November 200.5 by the Scientific Editor. 



Fish. Bull. 104:489-497 (2006). 



Geographical differences in the feeding patterns 

 of red rockfish iSebastes capensis) 

 along South American coasts 



Claudio A. Barrientos 



M. Teresa Gonzalez (contact author) 



Carlos A. Moreno 



Institute de Ecologia y Evolucion 

 Universidad Austral de Chile 

 Isia Teja s/n, Casilla 567 

 Valdivia. Chile 

 Present address for M T Gonzalez: 



Instiluto de Investigaciones Oceanologlcas 

 Universidad de Antofagasta, Casilla 170 

 Antofagasta, Chile 



Email address for M. T, Gonzalez: mtgonzalezis'uantof.cl 



The feeding habits of a species, deter- 

 mine(i by its physiological, and behav- 

 ioral adaptations, form a basic aspect 

 of its biology; they provide a way to 

 understand the trophic interactions 

 between predators and their prey 

 (Herran'). Throughout the evolution 

 of behavior and morphological adapta- 

 tion there have been strong selective 

 pressures toward those characteristics 

 that allow a species to capture its prey 

 and to escape from predators (Hixon 

 and Beets, 1993; Reznick et al., 1997; 

 Abrams, 2000). 



Most trophic studies in fishes are 

 carried out only on a local scale (e.g., 

 Moreno and Zamorano, 1980; Ojeda 

 and Fariiia, 1996), and rarely consid- 

 er the predator's entire distributional 

 range. Thus, conclusions about the 

 species" trophic patterns can reflect 

 local conditions rather than a gener- 

 alized feeding habit. In the Southern 

 Hemisphere, red rockfish (Sebastes 

 capensis (Gmelin, 1788)) is the only 

 known species within this genus. It 

 is distributed from the Pacific coast 

 (the coast of Peru and Chile), to east 

 of the Falkland Islands, to east of 

 Tristan da Cunha, and as far as the 

 southwestern coast of South Africa 

 (Chen, 1971; Kong, 1985). Sebastes 

 capensis is an ovoviviparous species 

 that inhabits the waters over the con- 

 tinental shelf between 20 and 200 m 

 in depth (Pequeho, 2000). Despite the 

 economic importance of this species 

 along the north and central coast of 



Chile, where it is exploited by local 

 fisherman, there is little information 

 about its biology and ecology. Cur- 

 rently, there is only one known study 

 describing the diet of this species 

 from the central Chilean coast (Ojeda 

 and Fariiia, 1996). 



In our study, the feeding habits 

 of S. capensis are described and its 

 feeding strategy is analyzed along its 

 geographic range in South America 

 in order to understand whether the 

 feeding pattern and the trophic be- 

 havior of this species are maintained 

 at the regional scale. Moreover, the 

 ability of the feeding strategy index 

 of Amundsen et al. (1996) is evalu- 

 ated for a predator like S. capensis 

 that is a passive ambush feeder. 



Materials and methods 



Sampling 



The area of study included most of 

 the distributional range for S. capen- 

 sis (Fig. 1) along the Chilean coast — 

 Antofagasta (23°11'S; 70°29'W), 

 Coquimbo (29°58'S;71°19'W ), Val- 



1 Herran, R. A. 1988. Stomach con- 

 tents in fishes: bibliographic revision 

 of objectives and methods. Technical 

 report of the Instituto Oceanografico 

 Espafiol, number 63, 74 p. Muelle de 

 Poniente s/n; Apartado 291; 07015 Palma 

 de Mallorca; Islas Baleares; Spain. [In 

 Spanish.] 



