Tracking the Invasive Veined Rapa Whelk
River Watch
Author
Juliana M. Harding, Vicki Clark, Virginia Sea Grant & Virginia Institute of Marine Science
Grade Level
9-12
Lesson Time
1.5-2 hrs.
Objectives
- Describe the introduction and habitat of the invasive veined rapa whelk.
- Predict the distribution of the invasive veined rapa whelk by evaluating habitat characteristics.
- Discuss the impacts of invasive species.
Alien species, Non-native species, Ballast water, Donor habitat, Invasive species, Receptor habitat, Self-sustaining population, Standard error of the mean, Veliger, Whelk
Materials Required
Rapa River Watch booklet Notes
Based on the following publication:
Harding, J.M. and V.P. Clark. 2006. Rapa River Watch Activity Booklet for Educators. Virginia Institute of Marine Science, Gloucester Point, VA.
VSG-05-09, VIMS-ES-58. 12/2005. Credits
Updated by Celia Cackowski
Summary
Determine the risk of a successful rapa whelk (Rapana venosa) invasion for four hypothetical estuaries.
Veined rapa whelks (Rapana venosa) are predatory marine snails that have been introduced into the Chesapeake Bay, USA. These large snails eat ecologically and commercially valuable shellfish including oysters (Crassostrea virginica) and hard clams (Mercenaria mercenaria). There are few predators in Chesapeake Bay that can successfully attack and eat large rapa whelks. Since rapa whelks are long lived (possibly more than 15 years) and reproductively active at 2-3 years old, once introduced, rapa whelks are very likely to become established if the habitat environmental conditions are suitable.
Rapa whelks are native to Asian waters near Japan and Korea. They were introduced to the Black Sea in the 1940s and have since spread into the Aegean, Adriatic, and Mediterranean Seas as well as Chesapeake Bay (USA), the Rio del Plata (Uruguay and Argentina), Brittany coast of France, and the North Sea near the Netherlands. Recent introductions are most likely the result of ballast water transport of swimming larval rapa whelks from occupied habitats into new environments.
The Chesapeake Bay is home to several of the largest ports on the US Atlantic coast, notably Hampton Roads-Norfolk. Most of the rapa whelks caught in the Chesapeake Bay have been from the Hampton Roads-Norfolk region. Aquatic scientists, resource managers, and commercial shellfish growers up and down the US Atlantic coast are very concerned that vessel traffic from Chesapeake Bay may introduce rapa whelks into other habitats. The million dollar question for everyone is: If rapa whelks are introduced to this habitat, will they survive and establish a self-sustaining population?
The answer to this question is a complicated one and will vary from place to place. The secret to finding an answer lies in understanding the biology and physiology of the rapa whelk. Larval period duration, or the length of time that a baby rapa whelk stays planktonic (swimming), and the length of time the larva is in ballast water affect whether or not a transported larva will be able to survive and be pumped out with ballast water into a new habitat. Salinity and temperature tolerances of the larval whelk will determine if the larvae survive if added to a new place via ballast water. The proper substrate and food availability will determine if the whelks survive to maturity and can reproduce, creating a self-sustaining population.