Fish distributions are changing. What's the new 'normal'?
If you watched the movie 'Finding Nemo' you'd be well aware of the marine transport corridor known as the East Australian Current. This warm water current flows and eddies its way down the east coast of Australia, bringing with it tropical species that are 'normally' found further north.
In the warmer months of the year, tropical fish species are commonly seen around Sydney and indeed some even make their way down to the southern coast of New South Wales. The 2011 blog posts 'Batfish in Sydney Harbour' and 'Whale Shark in Botany Bay' are cases in point. Recently however we have had some really odd tropical surprises on our own 'doorstep'.
John Sear, who manages a website on the Fishes of Cabbage Tree Bay Aquatic Reserve in Sydney, has sent images of a number of surprising sightings from the area. Perhaps the strangest is the Burgundy Shrimpgoby, Amblyeleotris wheeleri (see image above) and its burrow-mate the snapping shrimp, probably Alpheus ochrostriatus. These two animals have not been previously recorded in New South Wales waters - Queensland is well over 600 km to the north!
Another recent surprise was the Clown Triggerfish (image above right), which was speared off 'The Gap', Sydney, in May. Derrick Cruz brought the fish to the museum where it is now registered in the ichthyology collection (AMS I.46442-001). This specimen provides verifible evidence of the species occurring in Sydney waters in May 2014.
One of the great strengths of museum collections is the fact that they provide a 'snapshot in time'. Museum collections are used extensively to determine the distributions of species. What is really challenging is determining the 'official' distribution of a species. Locality records of juveniles of tropical species are often not included in the 'recognised distribution' of a species, but how do we handle real outliers like Derek's Clown Triggerfish and John's Burgundy Shrimp?
Distribution patterns may also be changing. Early historical records provide evidence of the presence of the Eastern Blue Groper, Achoerodus viridis (which incidentally is the New South Wales fish emblem), occuring in Tasmania (Last, et al., 2011). In more recent times the species was not sighted in Tasmanian waters and the 'official' southern distribution limit of the species was Wilsons Promontory in Victoria. According to Redmap, sightings of Blue Gropers have been made in Bass Strait and off the east coast of Tasmania. Last, et al., 2011, lists the Eastern Blue Groper and several other species as a 'recovering species' in Tasmanian waters. They state that "The recent rediscovery of juveniles of A.viridis, a major predator of urchins, in the north and north-east [of Tasmania], may have important ecological implications in the future. This large wrasse was once considered to be a ‘common species around the rocky section of the coast’ (Lord & Scott, 1924), but was later excluded from the Tasmanian fish fauna (Last et al.,1983) as it had not been seen for more than 50 years and was considered to be extinct locally."
Museum specimens are vital to validate these occurences. One of the strangest 'Are you lost moment' of all was the Patagonian toothfish, normally a resident of Antactica that was caught off Greenland, which begged the question "How on earth did it get there?"
Potato cod, (Epinephelus tukula) in the Gold Coast Seaway (Facebook link)
Tags fishes, ichthyology, fish distributions, tropicalisation, Clown Triggerfish, Amblyeleotris wheeleri, Balistoides conspicillum, Eastern Blue Groper, Burgundy Shrimpgoby, Achoerodus viridis, distributions, changes, climate change, Whale Shark,