The Nature Park manages Seal Rocks, 2km west of Phillip Island.
Seal Rocks holds one of the largest colonies of Australian fur seals.
About 6,000 pups are born there each November-December, one quarter of pups born for the species each year.
Australian fur seals are top-level predators in coastal waters of south-eastern Australia and frequently interact with commercial fisheries.
Seal research investigates seal numbers, range, diet and management issues.
See latest seal tracking - 08 September 2010 Seal numbers In collaboration with other researchers in Victoria and other states, we monitor Australian fur seal populations by recording numbers of pups. Australian fur seals were over-harvested during the 1800s and have taken a long time to recover recovery. During most of the 1900s, less than10,000 pups were born annually. Then during the 1980s and 1990s, numbers started to increase. A species-wide estimate of live pups in 2002 recorded a near-doubling of annual pup production since the 1980s. To determine if pup production increased after 2002, we estimated live pup numbers again in 2007. Pups were recorded at 20 locations: 10 previously known colonies, three newly recognised colonies and seven haul-out sites where pups are occasionally born. Two colonies adjacent to the Victorian coast accounted for 51% of the pups : Seal Rocks (5660 pups, 25.9%) and Lady Julia Percy Island (5574 pups, 25.5%). Although some colonies were up and some were down in pup numbers, the 2007 total of 21 882 ± 187 (s.e.) live pups did not differ significantly from 21 545 ± 184 estimated for 2002, suggesting there was little change to overall population size. However, the colonisation of three new sites between 2002 and 2007 indicated population recovery continued.
To estimate the total population, we need to take into account pups that were born but died before we got to the colonies to count them and then, based on demographic data (survival rates and pupping rates), use a multiplier of pups born to estimate total seals. An average of about 15% of pups that are born can die in the first two months of life and a species-specific multiplier of 4.5 times pup births has been derived to estimate a total population for Australian fur seals. Using these figures, we estimate that the total population of Australian fur seals was in the vicinity of 120,000 individuals in 2007. For more in formation, see Kirkwood et al. (2010) Continued population recovery by Australian fur seals. Marine and Freshwater Research 61, 695-701.
Seal diet At Seal Rocks, we assess Australian fur seal diet by identifying prey remains in bi-monthly scat (poo) collections. So far, we have identified prey from 42 fish taxa, 7 cephalopod taxa no crustacea and no birds. Six fish species represent 80% of the fish prey, in terms of frequency of occurrence, and the arrow squid Nototodarus gouldi represented 70% of the cephalopod prey. Significant annual variability in diet is due to the presence of redbait (Emmelichthyis nitidis) in some years and its near absence in other years, and replacement in by barracouta (Thyrsites atun), red cod (Pseudophycis bachus) and leatherjackets (Fam. Triglidae). The variation is related to mean sea surface temperature changes in western Bass Strait, where the seals forage. Redbait proliferate in cooler years and are less abundant in warmer years. The propensity for diet regimes to exist for several years then change suggests multi-year cyclic fluctuations in the prey and in Bass Strait ecosystems, that have previously not been recognised. Seal diet - [PDF 115 KB]
Seal entanglement We monitor seal entanglement rates at Seal Rocks to find how many seals get entangled and what they get entangled in. When we see an entangled seal, we try to catch it and remove the debris.
In the past 10 years, we have seen over 300 entangled seals and removed debris from over 150 of these. Trawl net (usually green) has been the most common material on the seals entangled in, but its frequency has decreased in recent years. Monofilament (fishing) line is next and has been increasing. Seal entanglement - [PDF 49 KB]
Seal tracking We want to know which areas of ocean are important to Australian fur seals, where they catch most of their fish and where they may encounter human activities such as fishing.
Seals are tracked using satellite technology. Transmitters called a Platform Transmitter Terminals (PTTs from Sirtack New Zealand or Wildlife Computers, US) are glued to the seals' fur. Transmissions are detected by CLS Argos (France) instruments on polar orbiting satellites then relayed to ground stations. We can plot where seals are going, how long they spend in different areas of the ocean and the duration of their feeding trips.
