article_cherabin
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Peter Novak conducted the first study of the life cycle of the cherabin, a small freshwater prawn species found in northern Australian rivers. Over three years, he monitored over 4,500 adult cherabin and tens of thousands of juveniles across a 400 km stretch of the Daly River. He discovered that the cherabin's reproduction and hatching of larvae is timed to the wet season rains from December to March. After the rains, juvenile cherabin migrate upstream in April and May, with up to 14-15 million juveniles replenishing nutrients in the river system. The cherabin must complete their migration to saltwater nurseries within seven days of hatching to survive.
article_cherabin
- 1. The north of Australia is internationally recognised as one of the most ecologically important regions on the planet. Across this immense landscape run its life-supporting arteries, a remarkable network of rivers largely untouched by human development.The remoteness of these river systems has offered significant protection for the life forms that depend on them for survival, but has also provided challenges in their continued management and conservation. Traditional Indigenous knowledge and modern science tell some of the story of these great rivers, however, much is still not known. This is particularly the case for the life and times of a small, yet prolific species of north Australian freshwater prawn, known locally as the cherabin.This purple-clawed river dwelling crustacean is cherished by fishers and Traditional Owners alike. Until recently, however, there was limited data on the cherabin’s ecological role and life history, including whether they migrate, and where and when they breed. Charles Darwin University, Research Institute for the Environment and Livelihoods (RIEL) PhD candidate, Peter Novak, is changing all that. Peter has been conducting the first ever study into the life cycle of this mysterious cherabin (Macrobrachium spinipes) species.To understand their natural history, Peter researched the species’ annual migration, and breeding process. Peter’s research has involved monitoring a 400-kilometre stretch of the Daly River, from Katherine to the mouth and through the Edith and Ferguson River. Over a three-year period he surveyed more than 4500 adult prawns and tens of thousands of juveniles and larvae. He collected females with egg clutches of ready-to-hatch larvae from the Daly River and, in the lab, tested the survival rates of the larvae in freshwater over a period of days. Peter discovered that for a larva to survive it needed to reach the saltwater nursery grounds within seven days of hatching.Without this annual journey downstream the species would not survive. Chasing cherabin ANGUS SMITH WRITES ABOUT HOW PETER NOVAK IS EXPLORING THE LIFE CYCLE OF THE MYSTERIOUS NORTHERN CHERABIN. FOR FURTHER INFORMATION riel@cdu.edu.au www.riel.cdu.edu.au www.facebook.com/RIELcdu
- 2. Peter discovered that the cherabin’s annual journey is timed to be in tune with river flow and season. Reproduction and the hatching of larvae began with the rains of the wet season from December to March. After the rains, the cherabin which have been developing in the estuary as larvae, migrate back up stream as juvenile mini prawns. From these observations it was estimated that up to 14 to 15 million juvenile cherabin migrate upstream over about 30 days in April/May, along with other iconic species like Barramundi and mullet.The migration is like a replenishing of nutrients and food for the river system.The findings about the annual migration will provide valuable baseline data about the species that can now be used to improve management of cherabin populations in the Northern Territory. “Now we know how important river flow is to the survival of these cherabin populations, and also how vital the species is in the linkage between freshwater and estuarine food webs. Any developments that might impede the migratory behaviour of cherabin could have significant impacts at an ecosystem scale.” Peter said. In the future Peter hopes to conduct research on cherabin in other regions of Australia such as the Kimberley and Gulf country, to determine if the life history that he has uncovered in the Daly region is consistent among rivers with different flow regimes. Further work could also investigate the ability of larvae to survive at sea. For instance, larvae could reach the estuary at the Daly, drift further out and these larvae could then settle in, say the Finniss River. If this occurs and the populations in different rivers are connected, then this may confer stability to the cherabin population. The cherabin project is supported by Charles Darwin University, the Research Institute for the Environment and Livelihoods, the Northern Australia Hub of the National Environmental Research Program, the Northern Territory Government Research and Innovation Post Graduate Scholarship, and Holsworth Wildlife Research Endowment. “Now we know how important river flow is to the survival of these cherabin populations. PETER NOVAK | CHERABIN University, the s, the Northern Program, vation Post h Endowment. Previous page: Peter Novak measures a cherabin on the Daly River. Left: Peter with a cherabin at the aquaculture research facility at Charles Darwin University. Photos Michael Lawrence-Taylor. Below: Two male cherabin (dominant above with the other subordinate). Photo Peter Novak.