Scamander River Fish Mortality Event 2015
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Late in May 2015 large numbers of fish were sighted dead and dying in the Scamander River. Council and the Tasmanian Environment Protection Authority (EPA) worked together with community members to monitor the fish mortality event and collect information after a late June spike in fish deaths.
Scamander River is a famous black bream fishery and the loss of possibly thousands of bream during the 2015 winter has alarmed many local residents and recreational fishers. Estuary eels, luderick, chub mullet and other species also died, but in much smaller numbers. Pelicans and gulls flocked to the river to feast on the windfall.
On Sunday 9 August 15 concerned local residents and fishers attended a community information session convened by Council and the EPA to present findings of tests and review events since May.
A timeline for events was presented by Council’s NRM Facilitator and findings from water sampling and laboratory analysis of water, fish and ‘white powder’ samples were presented by the EPA’s Compliance & Incident Response Section.
No signs of pollution or pesticides were found and exceptional natural conditions were considered to be the cause of the deaths.
The water sampling that was undertaken indicates there was significant stratification of the water in late June. This included low oxygen levels in warmer water at depth, over a colder low salinity surface layer. Some oxygen levels were low enough to be harmful to fish and this is the best explanation for the deaths from what is known. A green filamentous algae was also observed and appeared to be dense at times on upper and middle reaches of the river during the period.
Seasonal stratification, including low oxygen levels and algae occur naturally. However, participants pointed out at the community information session in August that they had not seen such a fish mortality event in living memory – as much as 70 years ago.
Copies of laboratory analysis reports for various samples and the EPA’s summary of findings from that data and events can be downloaded here, courtesy of the EPA. The timeline of events is shown below along with a map plotting some of the water quality data.
2015 timeline of events
Mid May Scamander River barway closed/closing.
19 May (AM) Fish deaths reported.
19 May (AM) Council and EPA work together on reports of fish deaths.
19 May (PM) Check of river confirms reports.
20-May Pelican & gull numbers increase, some fish still dying.
20-May Fish sample sent to pathology - no signs of disease or cause of death.
20-May River water levels rising.
9 June Council considering opening barway.
11 June Opening barway should be okay.
18 June (PM) Barway opened by Council to protect roads.
22 June Taswater ‘ice-pigging’ to clean water mains starts.
24 June Spike in fish deaths.
24 June 2nd dead fish sample to pathology: no signs on of disease, pollution or cause.
26 June Volunteers, EPA and NRM survey river and water quality.
29 June Fish still dying and birds feeding.
30 June Extreme natural conditions the likely explanation for deaths.
2 July Taswater review of recent operations finds none likely to be involved.
15 July Birds becoming fewer.
15 July EPA update to media - natural conditions the likely explanation for deaths.
27 July Still a few fish dying.
9 August Community information session at Scamander by Council and EPA – water and fish test results.
20 August A few dead fish seen near Wigram St. Barway closed/closing.
27 August School of healthy bream seen under Workers Ck. bridge
Working in partnership with NRM North, Council plans to facilitate future community activity to improve understanding of the condition of the Scamander River and its natural systems.
Council is supported by NRM North through funding from the Australian Government and also welcomes the support and collaboration of Tasmanian Government agencies such as the EPA.