Endangered sawfish killed in river low in oxygen December 17, 2015 Some of the dead freshwater sawfish and bull sharks (Pic: Dr David Morgan) A fish kill event in the Kimberley has seen at least 12 critically endangered freshwater sawfish die in water that was depleted in oxygen. Scientists from Murdoch University’s Freshwater Fish Group & Fish Health Unit were alerted to the deaths in a 15km stretch of the Fitzroy River in and upstream of Geikie Gorge National Park by Darngku Heritage Tours. Nine bull sharks, one freshwater whipray, cherabin (freshwater prawn), freshwater bivalve molluscs and catfish also perished. Dr David Morgan, Director of Murdoch University’s Centre for Fish & Fisheries Research, who attended the fish kill with fellow researchers, said water samples taken in the area of the deaths revealed that the water below one metre in depth was depleted of dissolved oxygen. “It is a real shame to see such large threatened species die, but hopefully this is a one off event. It’s not something I’ve seen before in the Fitzroy,” he said. “We believe the fish kill is linked to rainfall in the area that flowed into this section of the river. “The water there was black, tannin stained and likely to have carried large amounts of biologically active matter where rapid bacterial decomposition occurred. “This resulted in low dissolved oxygen and was compounded by extremely high temperatures in the area. When the fish kills were first reported to us in late November, the daily air temperature was 46oC. The river we sampled was also extremely low, the lowest in the 15 years we have been conducting fish research in the area.” Dr Morgan expected fish kill events to become more common under drying trends particularly when water temperatures were incredibly high in late spring and summer. Dr Morgan shot the following footage when he and fellow researchers were first alerted to the deaths. The Fitzroy River is a global refuge for freshwater sawfish and Murdoch University researchers have been studying various aspects of their ecology for over a decade. Team Sawfish, which includes the researchers and many local groups, has tagged hundreds of sawfish in the river. Two of the dead sawfish and one of the bull sharks had previously been tagged by Dr Morgan and his team. One of the sawfish was a 2.6 metre male, and is the biggest male ever recorded in the freshwaters of the river. One fish, which was tagged in 2011 (the biggest year of sawfish pups ever known) had grown from a one metre pup to 1.9 metres at the time of the fish kill. The Department of Water’s Phytoplankton Ecology Unit analysed water samples that were collected form the gorge and found no known toxic microalgae. The fish were too degraded pathologically for analysis. Print This Post Media contact: Jo Manning Tel: (08) 9360 2474 | Mobile: 0408 201 309 | Email: firstname.lastname@example.org Categories: General, Research, Animal and plant studies, environment and bioinformatics, School of Veterinary and Life Sciences Research Tags: bull sharks, centre for fish and fisheries research, darngku heritage tours, david morgan, fish health unit murdoch, fitzroy river, freshwater fish group and fish health unit, freshwater fish group murdoch, freshwater sawfish, freshwater whipray, geikie gorge national park, sawfish, tagging sawfish, team sawfish Comments (One response) Jimi Morgan January 9, 2016 This is a classic case of fish kills due to 'inversion' of the water column due to thunderstorm activity. This happens alot in aquaculture ponds and lakes David Morgan. Cheers Leave a comment Name (required) Mail (will not be published) (required) Website You can use these tags : <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong> We read every comment and will make every effort to approve each new comment within one working day. To ensure speedy posting, please keep your comments relevant to the topic of discussion, free of inappropriate language and in-line with the editorial integrity of this newsroom. If not, your comments may not be published. Thanks for commenting!