The ecology of the leopard shark Stegostoma fasciatum, with emphasis on a seasonal aggregation in southeast Queensland.
A PhD project undertaken by Christine Dudgeon at the University of Queensland, Brisbane, and supervised by Janet Lanyon
The leopard shark Stegostoma fasciatum (also known commonly as the zebra shark) is an egg-laying carpet shark that forms temporary aggregations and is distributed within shallow, coastal, subtropical and tropical waters of the Indo-West Pacific (IWP) region. The IWP region encompasses various densities of human habitation leading to differences in the levels of exploitation of sharks and rays, which are targeted for local consumption and export. This is reflected in two current regional IUCN Red List Classifications for leopard sharks: these are ‘Least Concern’ within Australian waters, and ‘Vulnerable’, throughout the rest of their range. Despite the conservation concerns for this species, as well as their importance within the ecotourism industry and collection for aquarium trade, little is known about leopard sharks in the wild. This project comprised the first intensive examination of the population ecology of wild leopard sharks and addressed three primary objectives: (i) to describe the population structure and demography of a relatively unexploited aggregation of leopard sharks in southern Queensland, Australia; (ii) to investigate the environmental parameters associated with the formation of the aggregation in southern Queensland and (iii) to investigate the genetic continuity between leopard shark populations from locations with differing levels of exploitation.
This project has demonstrated that leopard sharks form a large, predictable, shallow coastal aggregation comprised entirely of mature adults, as well as display high genetic subdivision in the Indo-West Pacific region with little to no recruitment into over-exploited populations from healthy populations. These findings indicate that if similar aggregations occur in regions of high fishing pressure then, without sufficient protection and management, localised depletion and extirpation will enventuate for leopard sharks populations in heavily fished areas.
Dudgeon CL, Feldheim K, Schick M, Ovenden JR (2006) Polymorphic microsatellite loci for the zebra shark Stegostoma fasciatum. Molecular Ecology Notes, 6, 1086-1088.
Dudgeon CL, Noad MJ, Lanyon JM (2008) Abundance and demography of a seasonal aggregation of zebra sharks Stegostoma fasciatum. Marine Ecology Progress Series, 368, 269-281.
Dudgeon CL, Broderick D, Ovenden JR (2009) IUCN classification zones concord with, but underestimate, the population genetic structure of the zebra shark Stegostoma fasciatum in the Indo-West Pacific. Molecular Ecology 18, 248-261.
Dudgeon, CL, Lanyon, JM and Semmons, JM (2012), Seasonality and site fidelity of the zebra shark, Stegostoma fasciatum, in southeast Queensland, Australia. Animal Behaviour http://dx.doi.org/10.1016/j.anbehav.2012.12.013
Figure 1: Map showing the location of the primary study site off North Stradbroke Island.
Figure 2: Leopard sharks aggregating off North Stradbroke Island.
Figure 3: Summer residents: leopard shark and manta ray.
Figure 4: Leopard shark with dart tag.
Figure 5: Taking a tissue sample from the tail of a wild leopard shark.
Figure 6: Ultrasonic data logger deployed off North Stradbroke Island.
Figure 7: Taking measurements of a leopard shark brought to the surface.