M. van Keulen

Dietary partitioning by five sympatric species of stingray (Dasyatidae) on coral reefs

Dietary characteristics and the degree of dietary partitioning by five species of sympatric stingray were assessed using stomach content and sediment analyses within a coral reef lagoon at Ningaloo Reef, Western Australia (the cowtail Pastinachus atrus, blue-spotted fantail Taeniura lymma, blue-spotted mask Neotrygon kuhlii, porcupine Urogymnus asperrimus rays and the reticulate whipray Himantura uarnak). A total of 2804 items were recovered from the stomachs of 170 rays and 3215 individual taxa from the environment, which were used in selectivity analyses. Twenty-four prey taxa were identified from stomach contents and pooled into 10 taxonomic categories for analysis, of which annelids, prawns, brachyurans and bivalves were the most abundant, together accounting for 96% of the diet. Himantura uarnak had the greatest interspecific dissimilarity in diet, consuming a larger proportion of crustaceans, notably penaeids (41% of total diet) than the other four species of rays, all of which had diets dominated by annelids (71-82% of total diet). Crustacean specialization by H. uarnak may exist to maximize resources and reduce competition among sympatric species. The remaining species may partition resources on the basis of space, rather than diet.

Manta ray tourism management, precautionary strategies for a growing industry: a case study from the Ningaloo Marine Park, Western Australia

Localised population declines and increased pressure from fisheries have prompted the promotion of manta ray interaction tourism as a non-consumptive, yet economically attractive, alternative to the unsustainable harvesting of these animals. Unfortunately, however, wildlife tourism activities have the potential to adversely impact focal species. In order to be sustainable, operations must be managed to mitigate negative impacts. A preliminary assessment of reef manta ray, Manta alfredi, behaviour identified short-term behavioural responses during a third of tourism interactions in the Ningaloo Marine Park, Western Australia. Although it remains unknown whether these responses translate to biologically significant impacts on the population as a whole, it is proposed that the precautionary principle be used to guide management intervention in the absence of conclusive evidence of the magnitude of tourism impacts. The principle supports the implementation of precautionary strategies to protect species and their environment from harm, even when the extent of the harm is yet to be confirmed. An increase in the level of industry management is recommended, including the implementation of a licensing system and adherence of all operators to a mandatory code of conduct during manta ray interactions. Considering the well designed and precautionary-driven management program of the Ningaloo whale shark tourism industry operating within the same marine park, a management program with the same underlying principles and objectives is deemed to be an ideal framework to build a comprehensive management plan for the manta ray interaction industry.