AIS September 2014 : Mystery Snails

Best Detected by walking your shoreline because when snails die, their shells wash up on shore.

Habitat Requirements

• Prefer shallow highly productive lakes and slow-moving streams with soft mud, silt, or sand substrate
• Productive systems provide minimum calcium requirements for shell growth
• Feed non-selectively on organic and inorganic bottom material, diatoms, and algae
• Prefer pH of 6.3-8.5, dissolved oxygen 7-11 ppm, and depths up to 3m
• Usually buried in sediment but can seal ‘trap door’ tight and float at the surface
• In the fall, migrate to deeper water to overwinter
• Most growth occurs in spring and summer when the water is warmer
• More likely to occur near boat landings, and in water bodies near population centers or with a high shoreline housing density

How Did They Get Here?

• First sold live in Chinese food markets in the 1890’s, then intentionally released to create a locally-harvestable supply
• Also released from aquariums and water gardens
• Now transported via bait buckets and livewells
• Will attach to macrophytes that can tangle on boat trailers or inadvertently occur in sediment on anchors
• Ability to close operculum makes them resistant to desiccation on a boat or trailer
• Bear live young which can be ‘stored’ inside the adult for long periods of time

Why Are They A Problem?

• Both species potential vectors for the transmission of parasites and diseases
• In Korea, Chinese Mystery snails host human intestinal trematode parasites
• Clog screens of water intake pipes
• Restructure established food webs through competition with native species for food and space, which negatively impacts native gastropods
• Banded Mystery snails significantly reduce survival of largemouth bass eggs in guarded nests

What Can Be Done?

• Squish ‘em!
• Physical removal: baiting and hand netting
• More snail eating turtles!

Note: DNR permits are required for chemical treatments, mechanical treatments, some manual treatments, biological control, bottom screening, and buoy/barrier placement.

 

Chinese Mystery Snail

• Olive Green with growth rings on shell
• Rounder outer lip than the native ‘elongated’ snails
• Up to 2.5 inches
• Native range: from Southeast Asia to Japan and eastern Russia

Life History

• Females live 5 years, males 3-4 years
  Ovoviviparous (embryos develop inside eggs retained within female until ready to hatch)
• Females contain embryos from May-August and young are born June-October
• Females produce >169 young in lifetime and up to 102 young/ brood, bearing most young in their 4th and 5th years

Banded Mystery Snail

• Tan and orange, 4 dark bands
• Relatively globose shell
• Up to 1.7 inches
• Reproductive females are larger than 0.6 inches
• Native to southeastern U.S. and north through Indiana/Illinois in the Mississippi River system
• Considered invasive in Wisconsin

Life History

• Ovoviviparous, lay eggs singly in albumen filled capsules
• Females brood eggs for 9-10 months and can brood more than one batch of young at a time
• Females produce 4-81 young/female but average of 11 young/female
• Brood size is positively related to the size of the female
• Females live 28-48 months;males 18-36 months
• Live at high densities up to 864/m²