The role of apex predators in coastal ecosystems: A case study examining the Broadnose Sevengill Shark Notorynchus Cepedianus

Large apex predators are believed to play key roles in ecosystem structure and dynamics. However, for the vast majority of large predators their ecological roles have not been defined or quantified. In particular, there is a lack of information on large mobile marine species. The ecology of the Broadnose sevengill shark, Notorynchus cepedianus was examined to determine their role in coastal systems of Tasmania. This was addressed by conducting studies on the different aspects of N. cepedianus ecology in two coastal areas of south-east Tasmania; the Derwent Estuary and Norfolk Bay. Both these areas are designated shark protected areas. Seasonal longline sampling showed that adult and sub-adult N. cepedianus (size 105-295cm) are highly abundant in summer declining to near absence in winter. The absence of smaller size classes (