The Tasmanian Giant Freshwater Lobster

Life Cycle
Females breed every two years with mating and spawning occurring between March and April (Autumn). The female carries the eggs under her tail over winter until they hatch in late December-January (Summer). Hatchlings stay attached until late February when they measure about 6 mm CPL(Carapace (Body/Head) Length). The young moult several times a year but this becomes less frequent as they get older.
Juvenile lobsters have been located in shallow faster flowing areas known as riffle zones. It is suspected they migrate into smaller stream zones including semi-permanent creeks. It is in these areas that they are safer from many predators such as larger fish (blackfish, trout) and platypus, which struggle to swim in the very shallow sections. The juveniles find cover amongst the cobble rocks and woody debris and remain in this area until large enough to move into the deeper areas known as runs. Runs are deeper flowing straight sections of a catchment. Many sub adult (<100mm CPL) have been located in these areas. It is suspected that these sub adults are not large enough to enter the domain of the adult lobsters, the deeper pools.
Adults take refuge in still, deep pools, which are sheltered and well shaded beneath submerged and decaying timber. Adults can live in larger numbers (up to 20 individuals) in one large pool. Although sometimes aggressive, lobsters appear to tolerate one another in these pools. Life Span It is estimated that lobsters may live beyond 40 years. Historically lobsters weighing 4 to 6 kg were reported however animals weighing 2 to 3 kg are now considered large.
Female lobsters mature after about 14 years, weighing about 500g with a carapace (head shell) length (CPL) of 120mm. Males mature more quickly at around 300g and approximately 76mm CPL in about 9 years.

Diet and Activity
Lobsters are very cryptic and shy. They are slow growing, slow to colonise new areas and have a low reproductive rate. Their diet is mainly decaying wood but leaves, fish, rotting flesh and detritus are also eaten. While little is known of their dispersal patterns individuals have been recorded moving 500m in 24 hours. Movements over land have been recorded. Lobsters are most active during early autumn and summer when water temperatures are higher.
Lobsters, by nature are shy, secretive animals. Ideal habitat is an intact stream catchment of several stream sizes including rivulets and small headwaters. These should flow and meander through a relatively undisturbed well vegetated catchment containing snags, pools and undercut, but not eroding, banks. Water temperature should seldom exceed 18*C have high oxygen content and be clear of sediment.

Range
The giant freshwater lobster Astacopsis gouldi, is considered to be the largest freshwater invertebrate in the world. Range It is found only in rivers of northern Tasmania. The lobster is found in all rivers that flow into Bass Strait with the exception of the Tamar catchment. It is also found in the Arthur River catchment, which flows into the West Coast. They occurred in river systems below 400m being most numerous in streams below 200m. Interestingly, their range coincided with that of the blackfish Gadopsis marmoratus.

Protected Status
In 1995 the lobster was listed as 'Vulnerable' on the Tasmanian Threatened Species Protection Act and the Commonwealth Endangered Species Protection Act. From 1 January 1998 it was declared a 'Protected Fish' under the Inland Fisheries Act signalling the immediate end of the recreational fishery. MAXIMUM FINE FOR TAKING LOBSTERS IS $10 000 It is illegal and a finable offence to catch or disturb the animal in any way. Disturbance includes kill, injure, catch, damage, destroy or collect the animal, either deliberately or accidentally.
Why so Threatened?
A steady increase in habitat disturbance, combined with a long history of traditional fishing has caused the decline of the lobster. Large individuals have been targeted for eating and trophies and this has had a significant effect on breeding stock, completely removing cohorts from some river systems. The lack of any bag limit until the 1990's allowed overfishing to occur for many years. Continuing Habitat disturbance, including the removal of stream vegetation, bank erosion, desnagging, channelisation, siltation, nutrification and chemical pollution continues to occur at every level from the small private landholder to large scale commercial forestry. Increased roading has led to a significant increase in fishing pressure and access to previously unexploited populations. Land Use Practices The clearing of streamside vegetation, extensive modification of stream channels, access by stock and influx of chemicals and nutrients have all contributed to the decline of lobster populations.

About “The Lobster Man”
Todd Walsh has spent much of his life in the wild rivers and creeks of North West Tasmania. He has been involved in lobster fishing almost all his life and comes from a long line of bushmen, who walked into remote areas searching for the giant lobsters. Todd has been involved in lobster conservation for many years and believes that the lobster is the icon species needed to preserve the world class river systems of North West Tasmania. Todd has an Associate Diploma in Applied Science and has studied Aquatic Ecology and Aquatic Technology at a tertiary level. He is internationally renowned as the world’s leading expert on the Giant Freshwater Lobster, and has given talks in Europe and the United States of America.