Shark Research in South Australia

A new research project on sharks has been developed at SARDI Aquatic Sciences and Flinders University in South Australia over the past three years. As part of this project, scientists are now using innovative satellite tagging technologies to map the spatial distributions, key habitats, migration pathways, oceanographic associations and ecological interactions of oceanic and coastal pelagic sharks. The project is also studying the diet, reproductive biology and genetic population structure of these iconic marine predators.

The scientists are collecting diet and DNA samples from sharks from the south-east of South Australia, off the Bonney coast to the western region of the Great Australian Bight and beyond. To date, shortfin mako and blue sharks up to 2 m in length have been captured and satellite tags have been attached to their dorsal fins. These tags indicate the shark’s location at the surface, the depths they dive to, and the water temperatures they are experiencing. This has been done with the valuable assistance of commercial fishers who have kindly donated their time and allowed the scientists to ‘tag along’ on their fishing trips. This allows for a better understanding of things like places where they go, stay and live, the other animals they interact with and types of currents and water temperatures that they like. Game-fishing clubs and their members have also been very helpful during competitions. They have provided the scientists with stomachs from makos for dietary analysis and flesh for DNA, which will provide valuable information on the mixing of populations between oceans'.

Other SARDI scientists, those from CSIRO and Primary Industries Victoria also conduct research on white, gulper, gummy, school and Port Jackson shark populations that inhabit the coastal, shelf and shelf slope waters of South Australia.

Sharks are 'top' predators

Sharks are among the top predators in marine ecosystems. While many of us are familiar with white sharks (Carcharodon carcharias) due to their high profile and attacks on humans, unfortunately there is limited information available for other species of pelagic sharks found in Australian waters. These other species include shortfin mako (Isurus oxyrinchus), blue (Prionace glauca), common thresher (Alopias vulpinus), bronze whaler (Carcharhinus brachyurus), and smooth hammerhead shark (Sphryna zygaena), which inhabit our coastal, shelf and oceanic waters.

Some sharks have global ranges and move over significant distances and therefore mortality at local scales has the potential to affect populations at oceanic scales. It is broadly accepted among scientists that sharks are generally slow growing, slow to mature, and have relatively few young each year and are therefore susceptible to any additional mortality.

Shortfin mako shark

Shortfin mako sharks are an iconic marine predator and a member of the family Lamnidae that also includes the white shark. Lamnids are particularly interesting as they maintain body temperatures above those of their surrounding environment, which may allow them to make feeding excursions into cold water to take advantage of food aggregations (Bernal et al. 2005, pdf). Makos mostly feed on fish and squids whose suckers leave circular scars on the skin of the sharks as they are devoured. Shortfin makos are a highly revered gamefish and they sometimes make spectacular jumps, both when hooked and when free-swimming among schools of fish. This tenacious, fearsome and unpredictable reputation leads to them being targeted during game fishing tournaments.