AIS / Fisheries

September AIS: 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!

Chinese Mystery Snail
Chinese Mystery Snails

  • 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
Banded Mystery Snails

  • 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

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