|Brandt, Thomas - USDI/USFWS|
Submitted to: North American Journal of Fisheries Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 2008
Publication Date: May 1, 2009
Citation: Mitchell, A.J., Brandt, T. 2009. Use of ice water and salt treatments to eliminate an exotic snail, red-rim melania Melanoides tuberculatus, from small immersible fisheries equipment. North American Journal of Fisheries Management. 29:823-828. Interpretive Summary: The red-rim melania, a non-indigenous tropical snail, can displace native snails and transmit trematodes directly to fishes and indirectly to other animals, including humans. The snail is very hardy and resistant to desiccation and to most disinfectants including chlorine. Dip nets and other small fisheries equipment are known to be a means by which this snail is spread from one water body to another. A practical and inexpensive method to disinfect fisheries equipment is needed to help prevent the snail’s spread. A treatment using 10 kg salt, 33.3 kg ice and 66.6 L water placed in insulated 120 L garbage was shown to be completely effective in killing all sizes of snails tested following two-hour exposures. The treatment consistently produced water temperatures of less than -2°C for the two-hour exposure period. This method is of value to fisheries personnel because they can quickly disinfect small immersible fisheries equipment for reuse in a matter of a few hours with supplies and material that are easily obtained and inexpensive.
Technical Abstract: Ice water and salt treatments were evaluated for disinfection of fisheries equipment contaminated with a non-indigenous tropical snail, the red-rim melania Melanoides tuberculatus. The snail can displace native snails and can transmit trematodes directly to fishes and indirectly to other animals, including humans. The red-rim melania has a well developed operculum that can protect it from desiccation and allows it to remain viable for days on dry fisheries equipment. Ice water treatments were produced by adding 10 kg salt and 33.3 kg ice to 66.6 L water (SIW) or by adding 40 kg ice to 32 L water (IW) and were tested at various time periods (from 0.16 min to 24 h) to find exposures that would kill 100% of the treated red-rim melania. Temperatures produced in the test containers by SIW and by IW treatments ranged from -6.3° to -2.4°C and 0° to 4.9°C, respectively. The survival of snails in salt water (SW) treatments (10 kg NaCl in 100 L of water) was also tested. Three size groupings of snails were tested; 30- to 40-mm, 15- to 20-mm, and 2- to 4-mm snails. The exposure periods that resulted in an estimated 0% survival for the 15 to 20 mm snails that were subjected to the SIW, IW, and SW treatments were 35.8, 179.6 and 423.6 min, respectively. The calculated amounts of time from the regression analysis required to kill 100% of the three size groups of snails exposed to the SIW treatment were 17.8, 35.8 and 67.5 min for the 30- to 40-mm, 15- to 20-mm, and 2- to 4-mm snails, respectively.