Question

Scientists believe that green crabs , originally from Europe, reached U.S. shores in the mid-1800s after riding across the Atlantic in the ballast water on ships. Once here in North America, they travelled to Maine, where they have been present for more than a century. Green crabs are a non-native, or invasive species, organisms that have been transported via human activities and introduced to locations in which they previously did not occur. The green crab population in some areas of Maine has increased dramatically in recent years, and they have been feeding on shellfish resources such as blue mussels and soft-shell clams, threatening the state's third-largest wild fishery. The increase in the green crab population has coincided with an increase in ocean temperatures. A similar cycle occurred in the early 1950s when the ocean temperatures rose and the green crab population increased, devastating the soft-shell clam resource in Maine. What can be done to mitigate the environmental impact of this invasive species? Select ALL that apply.
Responses
A Incentivize green crab trapping and removal programs.Incentivize green crab trapping and removal programs.
B Introduce poisons to green crab habitats to reduce their population.Introduce poisons to green crab habitats to reduce their population.
C Reduce water temperatures in areas with large green crab populations.Reduce water temperatures in areas with large green crab populations.
D Relocate green crabs to other areas of the state with a smaller population.Relocate green crabs to other areas of the state with a smaller population.
E Utilize fencing as a method of excluding green crabs from valuable bivalve shellfish areas.

Answer 1

A and E.

- A (Incentivize trapping/removal): Yes — targeted trapping and commercial/voluntary removal programs are a practical mitigation to reduce local green crab numbers.
- E (Fencing/exclusion): Yes — physical barriers (mesh/netting, exclusion fencing) can protect clam and mussel beds from crab predation.

Why the others are not appropriate:
- B (Poisons): No — pesticides/poisons would harm non‑target species and ecosystems and are not an acceptable control method in marine habitats.
- C (Reduce water temperatures): No — you cannot realistically lower ocean temperatures at the scale required; not a feasible mitigation.
- D (Relocate crabs): No — moving invasive animals spreads the problem and is ecologically and legally inappropriate.