There would be few Tasmanian anglers that have not caught at least a few Australian salmon. They are commonly called blackback in Tasmania with the smaller fish being known as cocky salmon. Many anglers target them specifically whilst others are simply caught as a bycatch. There can be no doubting their fighting abilities and they will test light gear to the limit. There have been numerous articles written over the years on this most popular sportsfish describing the correct techniques,tackle and fishing locations. There has not been much written about the life cycle of the fish itself and their general ecology in Australian waters. Shane Flude has done some research on our humble salmon and discovered some interesting facts.
Species and Range
Australian salmon were first recorded by Captain Cook in 1769 in waters near New Zealand. Noting their similarity to the European salmon he named them so however Australian Salmon are not true salmon but in fact belong to the Perch family of fishes. Up until the early 1980s it was believed that all salmon belonged to the same species. Four species are now recognised by the genus Arripis and include the following.
Australian herring (Arripis Georgianus), commonly known as the tommy ruff. They extend from the Gippsland lakes area in Victoria across to Shark Bay in Western Australia.
Northern kahawai (Arripis Xylahion), commonly called Kahawai. This species inhabits the waters around both main islands of New Zealand and also extends to the waters around Lord Howe, Norfolk and the Kermodec Islands.
Western Australian salmon (Arripis Truttaceus). Range between Kalbarri in Western Australia to Eden in NSW. Their general distribution is from Perth, across the southern coastline of the Great Australia Bight to Port Philip Bay in Victoria and Tasmanian waters.
Eastern Australian salmon (Arripis Trutta). Extends from waters near Sydney as far south as southern Tasmania, through Bass Strait and around Cape Otway in Victoria. The occasional individual has been captured in West Australian waters but this is rare.
The majority of fish caught in Tasmanian waters are Eastern Australian salmon, their western cousins are mainly limited to the waters along the north and west coasts. Both species are almost identical in appearance and can only be sorted by counting their gill rakers. Gill rakers as the name suggests are the fine filament like structures that are attached to the gills which assist the fish in sieving small food items from the water. The Eastern Australian salmon has between 33-40, the Western between 25-31. I trust next time you land a specimen you will now take the time to count the rakers to check your species.
Australian salmon have streamlined bodies and a strong forked tail. They generally display gold/brown spots on their upper body although this can vary between individuals. Juveniles or cocky salmon have more distinct golden spots and appear lighter underneath than the adults. All salmon are strongly countershaded, that is their pigmentation is darker dorsally giving rise to their common name of black back. The distribution of light on objects lit from above cause unequal reflection of light on a body of uniform colour. Shadows cast from this body provide predators clues as to the preys shape. Countershading therefore reduces the ease of detection of the prey by the predator by counterbalancing the effects of the shadows. This form of camouflage also assists in background matching. When seen from above the darker dorsal area of the salmon blends in with the darker waters below and when viewed from beneath the lighter ventral area blends into the sunlight from the surface. Salmon are only one of a number of pelagic fish species that utilise this form of camouflage, tuna ,shark and marlin all use countershading to some effect. Pelagic comes from the greek word meaning open sea and the pelagic zone is any water in the sea that is not close to the bottom. Fish that swim in this zone are therefore called pelagic fish. Salmon prefer the upper levels of the water column and are often seen near the surface, often feeding on schools of bait fish. Specimens have been taken in 80 metres of water but this is rare
Eastern Australian Salmon(EAS) can live for up to 26 years and reach 7kg in weight. They grow more slowly than Western Australian salmon(WAS) which live for up to 10 years and reach almost 10 kg. The Australian Angling Association record is a 9.4kg WAS which was captured in South Australian waters in 1973. Although both species can reach up to 90cm in length, fish above 60cm in Tassie waters are rare. A typical 2kg fish measures in at around 55cm to the fork.
Growth rates for WAS have been found to decrease from west to east hence the population in Tasmania and Victoria have the slowest growth. They also reach maturity later in their 4th - 6th year compared to their 4th year in the west. A mature WAS is around 54cm. EAS also mature in their 4th year at around 39cm.
Australian Salmon are serial batch spawners which means they release their eggs in batches over a period of time rather than all at once. They are also known as pelagic spawners as they spawn in the open ocean. Once fertilized the 1mm sized eggs hatch within 40hours and then drift with the zooplankton in the current.
EAS move to waters in northern Bass Strait between Lakes Entrance and Bermagui to spawn between the months of November and February. Once hatched the first year fish drift and migrate south and east from the spawning grounds to waters in Victoria and Tasmania. They are assisted by the south flowing East Australian Current . Juvenile fish up to 6cm will start to appear in Tasmania waters between January and September where they will frequent bays, estuaries and other sheltered coastal waters.
Once maturity is reached WAS move to waters in Western Australia between Brussleton and Albany to spawn. Peak spawning period is from march to may around the many headlands along the coast. The juveniles drift across the Great Australian Bight helped by the east flowing Leewin current. First year WAS appear in South Australian, Victorian and finally Tasmania waters about 6 months later and by this time will be between 5-8cm in length.
Diet and Feeding
Like most pelagic fish salmon are opportunistic feeders and will consume a variety of food items. As such they are fished for on a variety of lures and tackle ranging from tiny shrimp like flies to large 80mm slices. Both eastern and western salmon have distinct dietry preferences. The WAS juveniles begin life on a bottom dwelling diet of prawns and sprats with the adults preferring pilchards, garfish and squid. EAS juveniles prefer zooplankton which can include tiny crustaceans and squid. The adults diet does not differ much and it is for this reason the EAS needs a more efficient method of sieving food items from the ocean, hence the higher number of gill rakers on this species.
In Tasmania waters on calm days you may sometimes see large schools of surface feeding salmon sipping food items from the surface. The closely resemble midging trout, rising constantly every few feet and travelling great distances until they are disturbed. Disturbing the feeding salmon can be as simple as a low flying bird or poorly cast lure which then sends one thousand fish straight to the bottom. Last year on settled days this surface feeding activity was common off Port Sorell. Stomach contents revealed masses of tiny sea scud. Although present in large numbers the salmon were often quite selective when feeding this way. Despite poor fishing results the excitement of watching hundreds of feeding salmon approaching the boat usually meant I remained fishing.
Most anglers would have witnessed the spectacle of salmon feeding on schools of bait fish, a common site around most coastlines and a very common if not daily event on Georges Bay at St Helens. It is this feeding habit that salmon are best known for and attracts fisherman by the droves. They are often identified from some distance by a large number of actively feeding and diving sea birds as the salmon drive their food source to the surface. A relationship such as this is known as a commensal relationship, one that benefits the birds greatly but neither harms nor helps the salmon. It has been suggested that overfishing of salmon could have serious affects on the breeding success of the birds, such is the importance of this relationship.
This brings us to the subject of numbers and future populations. There appears to be two trains of thought on this topic, firstly from the scientific community who believe that numbers have been declining over the years and largely blame the commercial fishing. Commercial fisherman have provided figures that suggest the salmon population is stable if not on the increase and that the fishery could even sustain more pressure. Who ever is correct it is probably a good thing for the salmon that they are not a highly regarded table fish attracting a high price as due to their schooling nature they can be easily targeted. As a recreational angler it appears to me that numbers are high although I am obviously biased in saying this as I now know when and where to best target these fish. A recent trip to Georges Bay revealed the largest school of salmon I have yet seen. With the incoming tide a solid black mass of salmon swam past our anchored boat inside the barway for well over an hour. We estimated that around one thousand fish were passing the boat every minute in the 50 m wide school. The 59980 salmon that made it past our boat were present again the next day. They averaged 2 kgs and provided some fantastic fishing. It would certainly have been a shame to see a large trawler waiting for them on the other side of the barway. Monitoring of salmon populations will no doubt continue into the future and size and number restrictions may be altered to suit. At present however there appears to be healthy numbers and salmon should continue to be a popular sportsfish into the foreseeable future.