Didymo (aka Didymosphenia Geminata) 

A NZ Biosecurity hazard 

The following information is provided for the benefit of all anglers coming to NZ during the time of the 28th FIPS-Mouche World Fly Fishing Championships. Following discussions with Biosecurity NZ, Fish & Game and other interested parties, the organisers have been informed that restrictions on wading gear to be used in NZ will be in force during these championships. This due to the threat posed by an invading water algae, Didymo (see below).

The use of felt soled (footed) boots or waders are prohibited during the world championships. 
This requirement will form part of the rules modifications but is advised in advance to help teams with their planning.  

Anyone coming to NZ either as a member of the teams or as a guest, who is planning to fish either before, during or after the championships is advised that inspections of fishing gear are likely to be carried out on entry. Any equipment which has not been sterilised adequately may be required to be fumigated before entry. Please consult the web site of the NZ Government’s Ministry of Agriculture for details of what may and may not be brought into NZ. 

Members of FIPS who are planning to come to NZ prior to or stay on after the World Championships in 2008 are advised to ensure that if they fish in any South Island water PRIOR to coming to Rotorua, that they do the following: 

a) Clean all their gear according to the advice given below. Please pay particular attention to waders and any equipment which has been immersed in a river or lake. 

b) Any fly which has been used in a South Island waterway should be discarded BEFORE leaving the South Island and preferably before moving to another river. Failing this please ensure it is dried at temperature and not used again for 48 hours. 

c) Clean all nets, rods, outer clothing, lines and leaders. 

So what is Didymo? Also known as “Rock Snott” , this pest is being investigated in New Zealand after it was found in South Island waterways. It is one of the worst organisms to have infested New Zealand’s waterways. Didymo is a freshwater algae that forms a thick brown mat on rocks, plants and other materials in the water.

Didymo can form large mats on the bottom of streams, rivers and occasionally lake edges where there is a wave action. Its thick growths adversely affect most freshwater fish, plant and invertebrate species by reducing the number of suitable habitats. The loss of suitable insect habitat leads to the fish in the rivers starving. 

Currently, there is no 'cure' for didymo. Preventing its further spread relies on freshwater anglers cleaning their aquatic equipment between use in different waterways – regardless of location (North or South Islands) and even if they don’t see any didymo present while fishing. 

All anglers should note that Didymo is an unwanted organism under N.Z.’s Biosecurity Act 1993. It is an offence to knowingly spread an unwanted organism with penalties of up to 5 years imprisonment, and/or a fine of up to $100,000. 

If you suspect you have found this pest call 0800 80 99 66. 

Didymo has currently only been found in the South Island of N.Z. but every effort must be made to prevent it spreading to the North Island. The information provided here is taken from the N.Z. BioSecurity web site www.biosecurity.govt.nz. See this web site for full details 

Cleaning Methods for Didymo approved by BioSecurity NZ and NZ Fish & Game 

Didymo is most commonly spread by humans moving items between waterways. Fish without rocksnot – don’t take it with you. As a single celled organism it only takes one cell to start a new colony in formerly pristine place!!! 

It is our responsibility as users and lovers of New Zealand’s unique wilderness to do all we can to stop the spread of didymo and other aquatic pests. Clean all your gear every time you go into fresh water, anywhere, anytime and for any activity. 

For fishermen, this includes flies, any fly or storage box which has been wet, lines, leaders, rods, priests, and nets. Particular care should be taken to clean all outer garments including jackets, waders and boots, boats, motors, trailers and car tires (if the boat has been launched from the trailer into the water). Try to keep equipment bags and boxes away from the water or clean them too. 

To ensure YOU DON’T spread Didymo, wherever possible restrict equipment, boats, clothing and other items to exclusive use in one waterway. If you are moving items between waterways you should always clean them thoroughly before re-use. 

And its easy. Following the Check, Clean, Dry procedure below will ensure didymo and aquatic pests don’t travel with you. 

Check, Clean and/or Dry for 48 hours before re-using it. 

1. Check: 

Before leaving a waterway (river, lake or reservoir), check all your gear for threads or clumps of algae. Leave any debris that is found at that waterway. Do NOT throw it into rubbish bins untreated. If you find any later, treat it first and only then put in the rubbish, never down the toilet or drain. Drains lead back into other waterways. 

2. Clean: 

Soak all items for as long as it takes for the solution to thoroughly saturate the item, plus for at least an additional minute with one of the following:

Preferably, 

• 5% solution of dishwashing liquid (50 ml (approx 4 Tablespoons) per litre) Alternatively, if this is not available
• Hot (60°C + ) water
• 2% solution of bleach (20 ml (approx 1 1/2 Tablespoons) per litre)
• 5% solution of salt (50g of sodium chloride per litre)
• 5% solution of antiseptic handcleaner (50 ml per litre)
• 5% solution of nappy cleaner such as Napisan (50 ml per litre)

     To make up a bucket of solution for cleaning boots, use: 

• Minimum of 200ml of (chlorine) bleach (1 cup = 250ml) with water added to make ten litres for a 2% bleach solution
• 500ml or 2 cups, with water added to make ten litres for a 5% solution of dishwashing detergent, antiseptic hand cleaner or nappy cleaner
• 500gm Sodium chloride in 10 litres of water for a 5% salt solution. 

All these items can be found at a local supermarket. We recommend that you use products that are biodegradable.  

3. Dry: 

Dry – Items must be completely dry for at least 48hrs before use in another waterway. Preferably Clean the item then dry it and leave it for 48hrs. 

A good method to quickly dry and sterilise fishing lines and leaders, flies, clothes etc is to clean them, then dry them thoroughly using a hair drier, as this provides both heat and quick drying. Take care not to get the items being dried too close to the drier or they may burn. 

Once dry, leave for 48 hours as noted above in a warm dry place (such as an airing cupboard or near a heated towel rail) before re-using in another waterway. 

Anglers planning to fish in the South Island are advised to bring more than one set of flies so one can be drying while another is being used. The same holds true for reels, lines and leaders. 

Sport Fly Fishing NZ appreciates your helping to keep our fishing safe. Please don’t bring any alien species with you and make sure you don’t take any home either. We hope you will have a wonderful stay in NZ and be able to come back to still pristine rivers and lakes in years to come.

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