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Elasmobranchs play an important role within the trophic structure of marine ecosystems, but there are relatively few studies published on the feeding ecology of these species. Reported herein is the feeding ecology and trophic resource partitioning of two sympatric batoid species, Urolophus cruciatus and Narcine tasmaniensis from southeast Australia. The diet of males and females of both species was similar, suggesting no sex-specific dietary preferences. Ontogenetic changes in diet were observed from the diets of both species: as the body size increased, the proportion consumed of crustacea to polychaeta decreased. A relatively high degree of niche overlap (70%) was detected between the trophic resources of the two species. The way in which the predators partitioned the resources, however, was significantly different. U. cruciatus fed predominately on small benthic crustaceans (amphipods and decapods), while N. tasmaniensis displayed a preference towards Maldanidae polychaetes. Therefore, although U. cru- ciatus and N. tasmaniensis both feed predominately on benthic invertebrates, they specialise on different taxa. This trophic resource partitioning contributes to the biodiversity of the region by facilitating the coexistence of these sympatric species. The banded stingaree, Urolophus cruciatus and the Tasma- nian numbfish, Narcine tasmaniensis are two sympatric batoids widely distributed around the southeast of mainland Australia from South Australia to New South Wales. Both species are also found in large numbers in the coastal waters of southeast Tasmania, and are regarded as among the most common fish found on soft sediments in the deeper bays of southern Tasmania (Hutchins and Swainston, 1999; Edgar, 2009). They are also commonly caught as by-catch from a range of fisheries throughout their distribution, although incidental mortality rates have not been quantified for either species. Both species share several common traits including: a similar morphology and size as well as co-existing in the same demersal habitat where they remain relatively inactive, lying buried in either sandy or muddy substrate for long periods of time (Edgar, 2009; Last and Stevens, 2009). Given their commonality, we propose that there is a degree of competition for resources between the two species. The objectives of this study were to describe the diet composition of these two species, and assess the level of dietary resource partitioning to determine whether this is a potential mechanism that allows the two species to coexist within the coastal waters of southeast Tasmania.

Item Type:	Refereed Article
Research Division:	Biological Sciences
Research Group:	Ecology
Research Field:	Marine and Estuarine Ecology (incl. Marine Ichthyology)
Objective Division:	Environment
Objective Group:	Ecosystem Assessment and Management
Objective Field:	Ecosystem Assessment and Management of Marine Environments
UTAS Author:	Yick, JL (Mr Jonah Yick)
UTAS Author:	Tracey, SR (Dr Sean Tracey)
UTAS Author:	White, RWG (Professor Rob White)
ID Code:	72947
Year Published:	2011
Web of Science® Times Cited:	12
Deposited By:	Zoology
Deposited On:	2011-09-05
Last Modified:	2017-10-31
Downloads:	4 View Download Statistics