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Rock lobsters have been a highly prized seafood target for centuries. One tasty specimen appears in artwork in an Egyptian temple given as a gift to the pharaoh in 1500 B.C. They were popular back then and remain Australia’s most valuable seafood export now. But supply is based on lobsters harvested from the wild, and yield is strictly limited to maintain sustainability. Global demand is very strong and growing, and exceeds that of supply for several species of rock lobsters, especially Tropical Rock Lobsters. Many believe aquaculture production is the way forward. The quest to breed and rear rock lobsters in captivity was spawned as long ago as 1936 in Japan, and the pursuit of commercial scale rock lobster aquaculture is still under the microscope … literally. Scientists at AIMS are turning to microbial communities for answers. "First you must understand why rock lobsters are so difficult to culture," said Dr Mike Hall, AIMS aquaculture specialist. He has just docked from an expedition aboard the AIMS research ship the RV Lady Basten collecting lobster larvae from the Coral Sea, where there is two kilometres between the boat and the seabed. Dr Hall and colleagues are trying to get a better handle on the natural conditions under which larvae thrive, including their natural diet and the natural microbes - the bacteria and the pathogens that challenge larvae in the wild.
Dr Mike Hall on a recent field trip. "It is estimated that more than 50% of biodiversity is either a pathogen or a parasite, many of which are microbial so it makes sense to examine the microbial biodiversity and communities to see what impact they have on our target species. We then compare them with the microbes we are seeing in captivity - in the water column, in the food, the animals themselves and biofilms (the slime that grows on the walls of the aquaria). "Ultimately we’re trying to replicate the conditions of the wild and create a breeding environment that prevents ‘nasty’ bacteria from getting a foothold." So why does this little creature, the crayfish larva, remain a mystery after seven decades? For farming to be successful at a commercial scale it is necessary to use a terrestrial model of farming and forget about sourcing farm stocks from the wild. Currently the farming of many existing aquaculture species is dependent on juveniles collected from the wild and grown out in captivity. It is essential to eventually domesticate a species if it is to be truly ‘farmed’ Dr Hall said, "we need to maintain generations (from egg to adult to egg) in aquaculture farms". The most delicate stages of the farming process is from egg to juvenile, and as it happens rock lobsters have one of the longest larval phases of any marine animal, ranging from months to years. "For hatchery production that’s a nightmare. Since 1988 the Japanese have managed to complete the larval cycle for six species of rock lobsters and others (including Australian researchers) have also been successful, but only in small numbers. Closed cycle production, or ‘true farming’ has only been successful in crustaceans that have a short larval cycle of a few weeks. Overall there is very high mortality rate with rock lobsters. The major problem is poor health and compromised nutrition," Dr Hall said.
Early stage lobster larvae grown in the research aquarium. There is good news however. AIMS scientists have begun to identify the ‘nasty’ bacteria causing poor health. Some of these bacteria, given the right conditions, can dominate the microbial community which leads to poor health and increased mortalities. Scientists have also established the conditions unfavourable to the ‘nasty’ bacteria. They are planning to develop ways to prevent the bacteria from exploding into plague proportions in aquaria conditions and have developed collaborations with European researchers to pursue this. "We have the guilty parties lined-up," Dr Hall said. "A possible control measure could be to use probiotics and bacteriophage therapy." "We set out to understand how the bacteria ticks and then work out a way to interfere with the mechanism that allows it to proliferate. Rather than use an antibiotic that kills all bacteria, both good and bad, we’ve identified approaches that may keep the bad guys under control. It is essentially about controlling water quality and microbial management." AIMS scientists believe these discoveries are proving to be a major step forward for the much anticipated rock lobster aquaculture industry. "We believe success in completing the larval cycle could happen within months. "We are also confident that based on our understanding of the system it will be possible to consistently have success… and it is consistency that is essential to eventual commercial success," Dr Hall added. "We have a unique and ideal laboratory at the AIMS Cape Ferguson headquarters, in that we have good water quality, a state-of-the-art hatchery and great biotechnological research and development infrastructure all on one site. We can take our samples from the sea and aquaria direct to our biotechnology labs," Dr Hall said. There is a huge demand globally for tropical rock lobster and Dr Hall suggested only aquaculture has the potential to meet market demands in a sustainable manner. "The east coast of Australia harvests roughly 1,000 tonnes of tropical rock lobster. We know that there is massive demand for this species, especially in China, which greatly exceeds the wild harvest. "When we have cracked this hatchery phase we will know if the industry is a possible commercial scale proposition." This research was partially supported by Fisheries Research and Development Corporation (FRDC) through the Rock Lobster Enhancement and Aquaculture Subprogram (RLEAS) and private investors. Dr Mike Hall is a Principal Research Scientist at the Australian Institute of Marine Science and can be contacted on 07 4753 4444, or email: m.hall@aims.gov.au Want to know more?
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