Kelp forests occur in cold, nutrient-rich waters and provide a new kind of marine habitat and spawning ground for several sea creatures. Growing up to 30 meters off the sea bed and forming large canopies at the surface they offer nutrients shelter and protection to both hundreds of marine inhabitants as well as the coastline. Some of the best Giant Kelp forests grow in dense beds along the reefs of south-east South Australia, Victoria and Tasmania.
Over the last few decades, however an invasive species, the long spined sea Urchin (Centrostephanus rodgersii) have established themselves in Tasmanian waters, and owing to the rising sea temperatures making the colder waters more favorable to live in, coupled by the lack of any natural predators in these waters, the Urchin has been systematically destroying hectares of Kelp beds by overgrazing.
The long-spined sea urchin, while important to the marine ecology in small numbers, tends to have devastating effects when their numbers increase, since they graze on algae, sea weed and kelp. The reason they are so destructive is that they chew off the anchors of the giant kelp plants uprooting the entire kelp destroying the whole plant and causing a “kelp barren” wherever they go. The kelp forests of Tasmania are home to several fish and sea creatures including the rare ‘weedy sea dragon’ and arealso a favouite atrraction for Scuba Divers.
Enter the Rock Lobster. Tasmanian rock lobster fishing industry (TAFI) and the Tasmanian Government’s fisheries in an attempt to rid themselves of the Urchin menace have turned to its principal predator, the Tasmanian Rock Lobster. These lobsters are being purchased in large numbers from local fisheries or being donated by fisherman to be released and re-introduced into the Urchin affected areas such as Elephant Rock , North Bay, Sloop Rock, St Helens Island, Fortescue Bay, and Cape Paul Lemanon. All released lobsters are clearly tagged using blue T-bar tags printed on it that this lobster is illegal to take, and fishermen have been advised that capture of tagged lobsters is illegal, and if caught should be released back into the area it was caught. Additionally these lobster are specially marked with two separate holes of at least 5mm in diameter in the tail fan and two lines of blue and/or yellow coloured dye in the muscle tissue on the underside of the rock lobster’s tail.
Researchers believe that the large rock lobsters that prey on urchins will help control the kelp forest destruction. Observations so far indicate a small downward trend in urchin numbers which is promisiong news. While the program of re-introduction only recently began in 2009 there is still time to assess the success or failure of this method to control the sea urchin population.
photo from flickr by Royston Rascals
