Guidelines for fish salvage

The construction and maintenance of waterway barriers and in-stream structures may require the use of temporary bunds to allow dry work conditions. Fish can become stranded in large numbers within bunded areas. This stranding may cause heat stress and depleted oxygen levels, for the fish, leading to death. Relocation may be needed to reduce this impact.

Bunds can be placed to minimise fish salvage, or suitable temporary pools can be maintained. This removes the need for fish to be moved. However, where bunds will be in place for longer than a day, fish salvage procedures should be implemented.

• Quantities of fish shouldn’t be under estimated. Several tonnes of live fish may be present at barriers in major river systems and small waterholes.
• Where possible, works should be undertaken in the cooler months. Fish are less active in cooler weather, are easier to handle and will incur less stress. Warmer temperatures during spring and summer, increase oxygen demand while the oxygen in the water decreases.
• It is important to take all possible steps to remove trapped fish and handle them in the correct manner.
• The waterbody should be assessed for a design that will facilitate safe fish removal. For example, access to the site, depth, and natural contours. Fish will concentrate in deeper areas as water levels drop.

Guidelines for Fish Salvage

1. Remove as many fish as possible using appropriate nets.

   Note: It is illegal to use certain types of nets, especially in freshwater. A General Fisheries Permit maybe required. Please call DAF for further information.

2. Lower the water level by 25% and remove as many fish as possible. Repeat at each subsequent 25% reduction. Removing fish at each reduction is important as overcrowding can result in a fish kill.

   Note: Noxious and non-indigenous fish must be killed immediately with a quick sharp blow to the head, or by placing in an ice slurry. Their bodies must be disposed of away from the waterway in a bin or buried. They are not to be returned to the water. For a list of Noxious Fish species, see the Biosecurity Act 1994.

   

   Seine netting to remove fish from a bunded area

3. The following handling methods lessen damage to fish by reducing the risk of bacterial infections after handling:

   • Use nets with a fine, soft, knotless mesh.
   • Handle fish with wet hands or a wet towel. Gloves that are wet, open weaved and knotless are good for handling purposes.
   • Handle large fish carefully. Fish of 2 kg or more need to be fully supported in a horizontal position with two hands or in a knotless net.
   Fish should be placed into suitably sized receptacles as soon as possible to minimise the handling time. The fish holding containers should have good quality, well oxygenated water.
   

   Native fish being salvaged using a fine soft mesh & knot free net

4. Remove, store and release the fish as quickly as possible.

   • Use appropriately sized containers with a sufficient water depth to allow for comfortable swimming positions. The container should have soft, rounded surfaces and a lid.
   • Size the container depending on the size and number of the fish that will be held. As a guide, 0.2 kg of fish per litre of water is acceptable for oxygen and stress levels.
   • Observe fish for signs of stress such as increased gill movements or swimming at the surface.
   • Monitor water conditions continuously. Regularly change water, to ensure oxygen levels are maintained, or release fish downstream if suitable conditions exist. As a guide, change 25% to 50% of water hourly, more frequently if conditions are hot. Alternatively, an aerating device that bubbles oxygen at a rate of 2 to 4 litres per second. If possible, keep the containers in the shade while working.
   • If pumps are used to exchange water ensure hoses are screened to prevent fish being injured or sucked through.
   • Where practical sluicing fish directly is a better option than transportation. A sluice should:
     • Consist of large diameter PVC pipe with smooth joints or a smooth earthen channel lined with a continuous length of plastic.
     • Be sloped no more than a ratio of 1:10 and must be provided with an auxiliary flow of water.
     • Have a base pool deep enough to cushion the descent of the largest fish. A minimum depth of approximately 1 metre would be suitable for the receiving pool.
   

   Scoop net and rounded container suitable for small bodied native fish

   Scoop net and rounded container suitable for small bodied native fish

5. Release fish carefully by placing the container in the water and allowing the fish to swim away. Drops from height should be avoided. If water temperatures are equal, then a release by scoop net may be possible. Where there is a notable temperature difference water should be exchanged to equalise the temperature before release. These actions will minimise stress.

6. In the event of a fish kill call the hotline number on 1300 130 372.

7. Removing Temporary Bunds

• Remove the most downstream bund first.
• All barrier material to be removed from the waterway.
• Silt fences must be used to prevent erosion.
• Natural stream channel to be reinstated.
• Banks of stream reinstated to natural state, contours and vegetation
• Aquatic environment similar to the prior state is to be reinstated

Further information

Further Information about fisheries issues can be obtained from the DAF Call Centre on 13 25 23.