Use of Ice-Water and Salt Treatments to Eliminate an Exotic Snail, the Red-Rim Melania, from Small Immersible Fisheries Equipment

Abstract

Ice-water and salt treatments were evaluated for disinfection of small immersible fisheries equipment contaminated with a nonindigenous tropical snail, the red-rim melania Melanoides tuberculatus. This introduced species can displace native snails and transmit trematodes directly to fish and indirectly to other animals, including humans. The red-rim melania has a well-developed operculum that protects it from desiccation and allows it to remain viable for days on dry fisheries equipment. Treatments were produced by adding 10 kg of salt and 33.3 kg of ice to 66.6 L of water (salt–ice-water [SIW]) or by adding 40 kg of ice to 32 L of water (ice-water only [IW]) and were tested for various periods (0.17 min to 24 h) to find exposures that would kill 100% of the treated snails. Temperatures produced in the test containers ranged from −6.3°C to −2.4°C for SIW and from 0°C to 4.9°C for IW. The survival of snails in saltwater-only (SW) treatments (10 kg of NaCl in 100 L of water) was also tested. Three size-groups of snails were tested: 2–4-, 15–20-, and 30–40-mm shell heights. Exposure periods that resulted in an estimated 0% survival for the 15–20-mm snails were 35.8 min for SIW, 179.6 min for IW, and 423.6 min for SW. The calculated amounts of time (regression analysis) required to kill 100% of the three size-groups of snails exposed to the SIW treatment were 17.8 min for 30–40-mm snails, 35.8 min for 15–20-mm snails, and 67.5 min for 2–4-mm snails.