Conservation News
Let's Stop the New Zealand Mud Snail
By Dougald Scott
Let's Stop the New Zealand Mud Snail
By Dougald Scott
The New Zealand Mud Snail (NZMS) is an invasive species new to California waters. It was discovered in the Owens River in 1999, and has since spread to the Calaveras, Mokelumne and Napa rivers as well as Hot, Rush and Putah creeks. NZMS can survive out of water if kept in a damp environment (such as a wading boot). One study reported 50% survival after 25 days out of water in a damp place. It is likely that their spread within California is the result of unintentionally being transported in wading gear. Their tiny size (around 1/8") makes them very difficult to catch in a visual inspection of wading gear.
The main impact of NZMS is their ability to out-compete other aquatic organisms which normally serve as food for fish. Since NZMS pass through the digestive tract of most fish alive and intact, they do not to the food base. There is no doubt that the presence of NZMS is bad news for a trout stream.
The California Department of Fish & Game along with NCCFFF conducted a scientific study to determine effective decontamination protocols for anglers to use after fishing in contaminated streams. The first phase of the study tested the ability of various cleaning solutions to kill ZNMS in the laboratory. The second phase tested the corrosiveness of the cleaning solutions on wading gear. The last phase tested the effectiveness of the cleaning solutions under field conditions. Over fifty volunteers, wearing their own wading gear, followed a marked trail along the stream bed in Putah Creek.
The majority of NZMS recovered during the field tests were associated with wading boots. In addition to being found on the tongue and laces of the boots, large numbers were present inside of the boots, having worked down between the boot and the neoprene bootie of the wader. If the boots contained insoles, snails were also found underneath them. NZMS were recovered from every set of wading gear in the field tests.
The study found that a five minute exposure to a 50% solution of Formula 409 Degreaser/Disinfectant killed all of the snails and did not damage the wading gear. The wading gear could be immersed in a bucket or placed in a "dry bag" (waterproof bag for river rafting) with the cleaning solution (see procedure below).
Recommended Cleaning Procedure for NZMS Infested Wading Gear
Wading gear should be disinfected prior to leaving the site. If this is not possible then wading gear should be sealed inside a large plastic bag and cleaned before it is used in other waters.
1) Remove wading gear upon exiting NZMS infested waters. Avoid allowing infested wading gear to come in contact with interior surfaces of vehicles or camping gear such as tents or trailers. NZMS can be transferred to any surface they come in contact with, and later be transferred back to cleaned wading gear. Turn waders right side out and remove insoles from wading boots.
2) Place waders, wading boots, and boot insoles into a dry sack (waterproof bags for river rafting, recommended size: 65 liter). Walking sticks will need to be cleaned separately outside of the dry sack to avoid rupturing the sack.
3) Add 8 to 10 liters (2 gal.) of a 50% Formula 409 Degreaser/Disinfectant solution to the dry sack and the seal the dry sack.
4) Pick up the dry sack and shake it back and forth using a rolling motion to ensure that the contents are thoroughly coated with the cleaning solution. Continue shaking for approximately 30 seconds.
5) Let dry sack sit undisturbed for at least 5 minutes. Then repeat the shaking and mixing for another 30 seconds.
6) Open the dry sack and remove the contents one piece at a time and inspect it to make sure that all debris that could harbor NZMS has been removed from the gear as well as any NZMS that could be lodged in cracks or crevices.
7) Rinse wading gear in clean water. Do not use water from the NZMS infested source. This may reintroduce NZMS to the wading gear.
8) Return cleaned wading gear to its appropriate storage container.
If you intend to soak your gear in a bucket instead of a dry bag, use the same general procedure, just make sure the gear is completely immersed in the 409 solution, and agitated throughout the 5 minute rinse.
How to make the 409 Cleaning Solution:
Dilute Formula 409 Degreaser/Disinfectant solution 1:1 with clean water to achieve the needed 50% concentration (i.e. 1 gallon of Formula 409¨ Disinfectant to 1 gallon of water).
The report did say "the cleaning solutions were not renewed during the course of the study." I would take this to mean that you can use the same solution for several treatments. Keep in mind that the solution will lose its effectiveness with repeated usage or extended shelf life. I will report more on this issue as information becomes available.
I checked local stores (OSH, San Lorenzo Lumber, Safeway and Costco) and could not find Formula 409 Degreaser/Disinfectant. I did find numerous sources on line. Most sources offer it in case lots of four one gallon jugs for $35-$40. I will order a case and sell it by the gallon at the August meeting. It will probably be around $10/gal after shipping. Don't use Formula 409 Cleaner as a substitute; it is not a strong enough disinfectant.
Club members planning to attend the Mammoth fishout should come prepared to disinfect their gear if they plan to fish the Owens River and/or Hot Creek. It would be a shame to spread this pest to uninfected creeks.
The complete Fish and Game study may be downloaded from Ralph Cutter's website at: www.flyline.com/environmental/nzms/.