Descriptive Ecology of Two South American Eledonids (Cephalopoda: Octopodidae)
Abstract:Eledone massyae and Eledone gaucha are small octopods that coexist along the continental shelf and slope of southern Brazil. A comparative study of the population structure, distribution and diet of these species was carried out based on bottom trawl material from fishing surveys off Rio Grande do Sui State (Brazil), between 30°43′S and 33°45′S and the isobaths of 10 and 110 m. The two species occurred throughout the year in trawls deeper than 40 m, on both sandy and muddy bottoms of the outer continental shelf and upper slope. E. massyae and E. gaucha were found at bottom temperatures ranging from 10 to 22°C in tropical, subtropical and subantarctic waters. Young E. massyae appear on the continental shelf in late summer and feed predominantly on small crustaceans such as amphipods. A single cohort of maturing animals remains on the shelf during winter and spring, switching their diet to larger prey, such as portunid crabs and polychaetes. In late summer, males and females migrate to spawning grounds outside the study area. Juveniles of E. gaucha occur on the shelf mainly during summer and autumn. Males and females seem to mature on the shelf throughout the year, although no true cohorts could be defined. In all size classes, small benthic crustaceans, such as amphipods and isopods are the predominant food items. There is no evidence of habitat segregation between these two eledonids, but as adults, they seem to exploit different food resources.
Document Type: Research Article
Publication date: May 1, 1995
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