Now that summer is here we can enjoy the early mornings and laze around on our beautiful coastal beaches. However, with the onset of summer we can also expect increased temperatures, storms and rainfall.
These altered environmental conditions can lead to fish kills in our local fresh, estuarine and marine waterways. Although fish kills are often perceived to be from water pollution, many fish kills are a natural phenomenon often caused by natural events.
Environmental influences, toxicants, pollutants and disease are all factors playing a role in fish kills. Each individual factor or a combination of these factors can be the cause.
Locally we experience 1-2 fish kills per year, many of which can be attributed to low dissolved oxygen (DO) levels. The normal DO range for the varying water types is between 6-8 milligrams per litre (mg/L) with very few fish species tolerating prolonged exposure below 3mg/L.
Some of the causes of low DO levels include excessive plant growth, high rainfall, floods, drought, and sediment disturbance. Other possible causes include acid sulphate soil runoff, water temperature, rapid changes in salinity, pollution, disease and toxic algae. Consequently, the cause of a fish kill can often be difficult to determine.
If you come across a fish kill don't enter the water as they can pose a health risk. Fish kills should always be reported as soon as possible to the Department of Environmental and Heritage Protection (DEHP) on 1300 130 372. In most situations a site inspection by an investigating officer will occur to try and determine the likely cause and a course of action.
For further information contact DEHP on 1300 130 372 or council on 5475 7272.