Whitebaiters urged to "Check, Clean, Dry" to prevent didymo spread

Date: 11 August 2008

With the whitebait season about to get underway, whitebaiters are being reminded to "Check, Clean, Dry" their nets and other gear between rivers to help protect our waters from the invasive algae didymo.

The whitebait season starts in most of New Zealand on Friday 15 August and runs until 30 November. On the West Coast the whitebait season is from 1 September to 14 November and on the Chatham Islands it is from 1 December till the end of February.

Martin Heine, Nelson/Marlborough Technical Support Manager for the Department of Conservation, which manages the whitebait fishery, said whitebaiters along with all other river users had a key role to play in preventing didymo getting into waterways currently free of the algae.

"We need everybody to do their bit by cleaning their gear between waterways to protect our freshwater environments, including whitebait habitat, against didymo and other aquatic pests."

Jeff Donaldson, Didymo South Island Operations Manager, MAF Biosecurity New Zealand, said whitebaiters should choose the most practical of several cleaning options for their situation.

"All waterways should be treated as if they are infected with didymo and all gear used in a waterways should be cleaned before it is used elsewhere using the approved 'Check, Clean, Dry' cleaning methods.

"As a first step, before leaving a waterway, whitebait nets, including corners, and other items should be checked for clumps of algae or other matter and any debris found left at the waterway.

A fact sheet with information on cleaning methods for whitebait nets and gear can be obtained from DOC rangers patrolling whitebaiting areas or found on the MAF Biosecurity New Zealand website www.biosecurity.govt.nz.

DOC is also calling on whitebaiters to ensure they comply with whitebaiting regulations in place to protect the whitebait fishery and native fish populations. The regulations include requirements to use only one whitebait net at a time, to stay within 10 metres of the net, and the net should not exceed more than one third of the water channel width. Information on whitebait regulations can be obtained from DOC offices and visitor centres, or follow these links:

Whitebait Regulations (all NZ except West Coast)

Whitebait Regulations (West Coast)

Protect our waters - Check, Clean, Dry whitebaiting gear

Didymo can be a problem for whitebaiters, clogging nets as it floats down rivers. Didymo is a single-celled micro-organism that can spread from one river or lake to another by the movement of water, equipment, clothing and any other damp item. To ensure you don't spread didymo or other aquatic pests, please restrict equipment, boats, clothing and other items for exclusive use in a single waterway between cleaning.

• Nets, neoprene waders and other items made of absorbent material can be decontaminated by soaking in a 5% solution of dishwashing liquid or nappy cleaner for as long as it takes to thoroughly saturate the item. Then leave the item for an additional minute to kill didymo cells trapped deep within the cracks, crevices and absorbent parts of the item. Non-absorbent items such as metal set nets, tyres, trailers and buckets can be soaked or sprayed with the above products.
• Dilute seawater such as is found in whitebaiting areas is ineffective at killing didymo. Whitebaiters who prefer to decontaminate their gear with salt should use a 2% by volume salt solution (saltier than seawater) prepared by adding one small cup (200mls) of table salt to water to make 10 litres. Soak for as long as it takes to thoroughly saturate the item, then leave the item to soak for an additional 10 minutes.
• Seawater will kill didymo. Submerging your net in 100% seawater for four hours will kill didymo.
• Other options for decontaminating gear include soaking in hot water above 45oC for at least 20 minutes (longer for absorbent items), freezing until solid or drying. Although drying will kill didymo, slightly moist didymo can live for months. If you are hanging up your nets to drain and dry, ensure the entire item is completely dry to the touch, inside and out, then leave for at least 48 hours before use.
• Whitebait nets with hollow frames will hold water inside the frame; drill holes in the frame, flush through with decontamination solution and allow the solution to drain out.

Information for whitebaiters who use felt-soled waders

• Fishing footwear containing absorbent material, such as felt-soled waders and boots, poses high risk of didymo transfer - these items are likely to come into direct physical contact with didymo cells (e.g. stepping on or brushing against algal mats), and the moisture in these helps cell survival.
• Choose one of the following treatments specific to felt-soled waders and boots. Absorbent items require longer soaking times to allow thorough saturation. For example, felt-soled waders require:
• • hot water: soak for at least 40 minutes in hot water kept above 45oC for the entire time; or
  • hot water plus detergent: soak for 30 minutes in hot water kept above 45oC containing 5% dishwashing detergent or nappy cleaner; or
  • freezing any item until solid will also kill didymo.
  • DRY: Drying will kill didymo, but slightly moist didymo can survive for months. To ensure didymo cells are dead by drying, the item must be completely dry to the touch, inside and out, then left to dry for at least another 48 hours before use.
• If cleaning or drying is not practical, restrict equipment to a single waterway. NOTE: The thicker and denser the material, the better it will be at holding moisture (and live cells), the slower it will be to dry out and the more difficult it will be to soak completely with cleaning solutions.
• When cleaning equipment, we recommend that you:
• • soak porous materials for longer than the specified treatment times to ensure cleaning solution has soaked right through the item soaking for the required decontamination time;
  • choose a decontamination solution that will not adversely affect your equipment;
  • follow manufacturer's safety instructions when using products;
  • dispose of cleaning waste well away from waterways.

Cleaning is only necessary when moving between waterways.

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