The recent fish kill in the Tallow Creek estuary highlights the problems that this Intermittently Closed and Open Lakes and Lagoon (ICOLL) faces, the willingness of people to interfere with natural systems on their whims, and a callous disregard for the killing of hundreds of fish.
I dread to think what contaminants have built up in the estuary sediments from the decades we used it as a sewer, and in runoff from Suffolk Park. Though we stopped using it as a sewerage outfall in 2005 and the water quality is meant to now be not too bad.
While there is abundant ignorance about the functioning of ICOLLs, one lesson that has been learnt throughout NSW is that the artificial opening of ICOLLs often results in fish kills if not done in the right way and at the right time.
Time and again, these kills occurred because waters became de-oxygenated and fish suffocated.
Contrary to claims, the artificial opening of the Tallow Creek estuary in the 90s did result in fish and bird kills.
The primary cause of the recent fish kills in 2012 and this month was the artificial opening of the estuary by people either wanting to stop the nuisance flooding of parts of their properties or just wanting to have fun riding the outflowing waters.
It has opened naturally at other times without these fish kills.
This time it was evident from the behaviour of the thousands of distressed fish I observed that they were suffocating because the water was de-oxygenated.
While I saw hundreds of dead fish, I do hope most of the distressed fish did subsequently recover.
Council’s Tallow Creek Floodplain Risk Management Study and Plan (2009) details an opening strategy for the estuary that was developed in consultation with the community and government agencies.
When the estuary reaches 1.8 metres above mean sea level, council is required to start regular monitoring of water quality, and only if it deteriorates beyond set benchmarks to open the estuary.
Once water levels exceed 2.2 metres, council opens the estuary using a strict procedure. Flooding of houses doesn’t occur until it reaches 3.4 metres.
Obviously the water quality did not deteriorate sufficiently to trigger an opening. Contrary to claims (Suzie Deyris, Gavin Greenoak, letters March 16) it did not become foul and its shores were not fringed with dead fish until it was opened.
In fact, the abundance, variety and size of fish affected prove it was a very productive ecosystem.
I appreciate that there are people who don’t like the colour of the water or understand the processes occurring who want to keep the estuary open all the time.
If they intervene to change the estuary it will change the abundance and diversity of fish and invertebrates present, drain the extensive fringing wetlands (most of which are protected under SEPP 44) and endangered ecological communities, affect a variety of threatened species, drain the surrounding acid sulfate soils and cause the generation of inflows of sulfuric acid and heavy metals.
Whether they are doing it for fun, to stop fllooding of their back yard, or because they have a hunch, I am shocked that vigilantes believe it is their right to undertake an identified ‘key threatening process’ (alteration to the natural flow regimes of rivers, streams, floodplains and wetlands) in a national park and a marine park, ignore council strategies, disregard environmental impacts and kill hundreds or thousands of fish because they want to.
Dailan Pugh, Byron Bay