Tasmania has a diverse range of fish species with hundreds of known species with the majority being in marine and estuarine areas. There are 25 native fish species that occur in inland waters and around 8 introduced fish species. Of the native species 12 are listed as threatened being either rare, vulnerable or endangered. Introduced trout form the basis of a major recreational fishery whilst other introduced species such as Redfin perch are known pest species. Some freshwater fish species are migratory and inhabit freshwater, estuarine and marine areas at various times in their life cycle whilst others are non-migratory and occur solely in freshwater.
Marine fish species may move very little or may migrate many 1000s of kilometres over the course of their life cycle. Many species periodically move between marine and estuarine environments to complete their life cycle or feed. Fish species have a preference for the environmental conditions they inhabit (limited range for salinity, temperature, oxygen levels for example). As a result they tend to inhabit a certain area or geographic range within the marine ecosystem which reflects the most suitable environment.
A fish kill is characterised by a sudden and unexpected large number of fish dying over a short time period and generally within a limited area.
Fish kills can be a result of human-induced impacts or due to natural events.
Human-induced fish kills can be caused by the release of pollutants, such as industrial or agricultural chemicals, hot or cold water, sewage and fuel spills. These can either cause a direct impact on the fish or cause changes in the environment, such as deoxygenation, rapid temperature and salinity changes.
Natural causes of fish kills can be related to life cycle events (such as migration and spawning), diseases (caused by bacteria, viruses and other vectors) and predator-prey interactions (feeding or avoiding being eaten). Physical changes to the environment (such as closing of estuaries and rainfall) can result in sudden changes in the physical water parameters.
In order to minimise potential risk to yourself if you see a fish kill do not
- Touch the fish or water in the area
- Collect fish for bait or other purposes (such as garden fertilisers)
- Consume any fish that have been caught in the area
In the event of a fish kill please report immediately
Contact the EPA Incident Response Hotline 1800 005 171, or email to firstname.lastname@example.org