Abstract
Catches and exports of skate Rioraja agassizii place this species as "vulnerable to extinction" on the IUCN Red List; therefore, biological and ecological knowledge becomes an important instrument for its conservation control. This study described and quantified the diet composition of R. agassizii by means of stomach analysis contents in the periods 2005-2006 and 2012-2013. We analyzed and quantified stomach contents in terms of abundance (%N), weight (%M), frequency of occurrence (% FO), and index of relative importance (IRI). The results showed differences in the food rates between the periods. However, the groups of food items were the same: Teleostei fish, decapods, and mollusks. In 2005-2006, the diet consisted mainly of shrimp, however, in 2012-2013 it consisted of fish, followed by decapods, especially shrimps. The differences in diets may be attributed to shrimp abundance, which do not characterize a change in the eating habits in 2012-2013, because, in addition to fish, shrimps were also important food sources. The presence of a certain prey is more related to its availability rather than the feeding preference of skate. The amount of ingested items is associated to biological and environmental factors, so that further studies relating diet with capture area, seasonality, depth, and other factors should be conducted.
Highlights
Elasmobranchs present slow growth rate, late maturation, and low fecundity (Frisk, 2010)
This study described and quantified the diet composition of R. agassizii using stomach contents of specimens captured during 2005-2006 and 2012-2013 in southern Brazil
We analyzed stomach contents in 351 specimens of R. agassizii from March 2005 to April 2006 captured by fishing pair trawling, at depths ranging from 10 to 146 m
Summary
Elasmobranchs present slow growth rate, late maturation, and low fecundity (Frisk, 2010). These factors, along with bycatch, can lead these organisms to a population decline, and the family Rajidae is one of the most vulnerable to exploitation (Dulvy and Reynolds, 2002). The scenario of overfishing, lack of biological information, and catches led to overexploitation of various demersal elasmobranchs in Southeast Atlantic or South Occidental. Gaichas et al (2005) claim for a proper management to protect the Rajidae family against locally depletion, especially when little is known about habits and structure of the population. According to Ellis et al (2010), research shows that some species of Rajidae feature very unequal distributions, which may make them locally prone to depletion.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
