\n<\/p>\n
A young Murray cod has swum one of the longest ever recorded journeys for the species, travelling about 900km through the Murray River, its streams and backchannels.<\/p>\n
Murray cod, Australia\u2019s largest freshwater fish, grow up to 1.5 metres and can live for half a century. Research by Victoria\u2019s Arthur Rylah Institute has shown the species, listed as vulnerable under federal environment laws, is capable of covering extreme distances.<\/p>\n
Dr Zeb Tonkin, a freshwater ecologist with the institute, said Murray cod had huge cultural and conservation significance.<\/p>\n
\u201cThey\u2019re the apex predator of the Murray-Darling Basin,\u201d he said.<\/p>\n
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In the years following a major mortality event due to low oxygen levels in 2016, researchers tagged about 70 juvenile cod using small audio tags \u2013 a bit like a microchip on a cat or dog \u2013 enabling their movements to be tracked via \u201clistening stations\u201d along the river and adjoining streams.<\/p>\n
Initially, the young cod didn\u2019t move far. \u201cThey basically hunkered down in their nursery habitat,\u201d Tonkin said. But as they approached maturity \u2013 about the age of four, when they were 50cm long \u2013 several took off in search of a new home range.<\/p>\n
One champion swimmer, which the scientists dubbed \u201cArnie\u201d in honour of Australia\u2019s multiple Olympic gold medallist Ariarne Titmus, left the entire study area and kept swimming, he says. It later popped up over the border into New South Wales.<\/p>\n
Taking advantage of the removal of barriers during the 2022 floods, the cod swam into the Wakool then the Niemur rivers before heading back towards home. In all, the fish travelled nearly 900km in less than two years. It was most recently tracked in late 2024 at a section of the mid-Murray, near Belsar Island, just upstream of <\/strong>Euston, and appears to have settled there for the time being.<\/p>\n \u201cFor this species, it\u2019s the longest we\u2019ve seen,\u201d Tonkin said. \u201cThere\u2019s a couple of other species that we know do this as part of their life cycle regularly, species like golden perch and silver perch.\u201d<\/p>\n <\/span> Photograph: Arthur Rylah Institute<\/p>\n Murray cod tend to be thought of as a sedentary species and can often be found hanging out near snags, or submerged logs. But as the research found, they also move \u2013 in some cases hundreds of kilometres \u2013 to disperse and breed.<\/p>\n Another individual, the \u201ccasanova cod\u201d, was previously found to have made a 160km round trip four times over four years.<\/p>\n By tracking fish movements in the river for more than a decade, ARI researchers have found that in dry years cod tend to prefer flowing anabranches of the river, while in wet years they are more likely to choose the main channel. The results have helped inform the way regulators manage flows and gates in the river to support fish breeding and survival.<\/p>\n skip past newsletter promotion<\/p>\n Sign up to Breaking News Australia<\/span><\/p>\n Get the most important news as it breaks<\/p>\n Privacy Notice: <\/strong>Newsletters may contain information about charities, online ads, and content funded by outside parties. If you do not have an account, we will create a guest account for you on theguardian.com to send you this newsletter. You can complete full registration at any time. For more information about how we use your data see our Privacy Policy. We use Google reCaptcha to protect our website and the Google Privacy Policy and Terms of Service apply.<\/span><\/p>\n after newsletter promotion<\/p>\n \u201cIt really highlights the importance of connectivity,\u201d Tonkin said. \u201cWith that big flood event and those barriers out of the way, they\u2019ve got capacity to really disperse and distribute, which is quite important in terms of species recovery.\u201d<\/p>\n Tonkin said tracking the cod over such large distances was only possible thanks to collaboration with interstate agencies and with funding from the Murray-Darling Basin Authority.<\/p>\n Associate Prof Paul Humphries, a fish and river ecologist at Charles Sturt University, who has written a book on Murray cod, said the fish was a \u201ckeystone species\u201d \u2013 both reliant on and critical to the diversity of animals and plants in the river floodplain \u2013 that had been heavily fished since Australia\u2019s gold rush in the 1850s.<\/p>\n \u201cMurray cod are like the lions and tigers of our rivers,\u201d he said.<\/p>\n Humphries, who was not involved in the ARI research, said movement \u2013 to feed, breed, disperse and migrate \u2013 was as biologically important to fish as living and breathing. But it was also important for conservation, by allowing them to recolonise areas, swap genes and breed.<\/p>\n \u201cOne of those things that we\u2019ve managed to be very successful at as humans is to put barriers in the way of fish movement,\u201d he said, with thousands of dams, weirs and other structures throughout the Murray-Darling Basin.<\/p>\n \u201cIf we are to maintain our populations of fish in a healthy condition, we do need ultimately to allow them to have unfettered movement \u2013 to go where they want to go, rather than confining them by the way that we manage our rivers.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":" A young Murray cod has swum one of the longest ever recorded journeys for the species, travelling about 900km through the Murray River, its streams and backchannels. Murray cod, Australia\u2019s largest freshwater fish, grow up to 1.5 metres and can live for half a century. Research by Victoria\u2019s Arthur Rylah Institute has shown the species,<\/p>\n","protected":false},"author":1,"featured_media":30749,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[50],"tags":[17994,2029,9124,752,7831,11846,2095,17995,17993,3219,943,392,10225],"class_list":{"0":"post-30748","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-environment","8":"tag-900km","9":"tag-australias","10":"tag-basin","11":"tag-biggest","12":"tag-cod","13":"tag-fish","14":"tag-murray","15":"tag-murraydarling","16":"tag-notsolittle","17":"tag-river","18":"tag-swimming","19":"tag-system","20":"tag-tracked"},"_links":{"self":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/30748","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=30748"}],"version-history":[{"count":0,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/30748\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/media\/30749"}],"wp:attachment":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=30748"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=30748"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=30748"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}