Research identifies snag in shark conservation

A case of mistaken identity for sharks found in Northern Territory waters could be preventing the conservation of some species from environmental change.

Research by a Charles Darwin University postgraduate student has revealed the growing trend of pooling similar species in conservation strategies as insufficient to protect coastal sharks from environmental change.

In a research paper, entitled “Never Judge a Book by its Cover – comparative life history traits of two morphologically similar carcharhinid sharks in northern Australia”, Bree Tillett compared ecological similarity between pigeye and bull sharks.

“Like many coastal sharks, these high order predators are threatened by over-fishing and predicted climate change,” Ms Tillett said.

“The species historically have been misidentified due to their similar appearance and shared habitats.”

Ms Tillett compared the pigeye and bull sharks’ age and growth dynamics as an indication of resilience to environmental changes, as well as genetic structure and habitat use to understand how each species interacts with their environment.

“Although they’re almost identical in appearance, and are similarly long-lived and late to mature, pigeye and bull sharks are genetically very different and interact with their environments in very different ways,” Ms Tillett said.

“Pigeye sharks are greatly influenced by changes in sea level such as predicted under climate change, which effects how widely the populations are dispersed.

“Bull sharks are much more mobile and occupy a greater variety of habitats at different life stages, including man-made canal systems in south-east Queensland.

“These differences in habitat use make this species more adaptable to changing environments.”

Ms Tillett said major developments underway in northern Australian waters and the region’s predicted population growth would put more pressure on the sharks’ habitats.

“Considering the ecological diversity within and between pigeye and bull sharks, a one-size-fits-all conservation plan is not appropriate,” Ms Tillett said.

“A unique opportunity exists in northern Australia to have effective conservation efforts firmly in place before these species experience further pressures associated with future environmental changes, whether natural or man-made.”

Ms Tillett will graduate at CDU’s mid-year ceremony.