Researcher with light trap full of polycheate worms

LARVAL CRAB STUDY

What is the best predictor of adult crab biomass? This question was determined by PCRG members to be our top research priority and, thus, a guide toward the development of our first coordinated research study. A long-term larval crab monitoring study in Coos Bay, Oregon by Dr. Alan Shanks (University of Oregon) provided evidence that larval crab abundance can predict adult crab abundance four years after the larvae are caught. We decided to build off of this model and determine whether it could also work in Washington by developing a statewide larval crab study using light traps deployed on docks/piers to capture Dungeness crab larvae and provide estimates of abundance.

A light trap is a water bottle with funnels on the side, a buoyant lid, and a light in the center that turns on at sunset and off at sunrise. Larval crab exhibit positive phototaxis, meaning they are attracted to light. We can take advantage of this behavior with these traps, which are especially effective at capturing megalopae, one of the larval stages of crab. See examples of what we catch below!

 
 

LIGHT TRAP LOCATIONS

See Where the Research is Happening!

 

Our Methods

The video below provides an overview of the PCRG light trap study methods. For more specific methodology, please refer to the methods guide written by our colleagues at the Swinomish Indian Tribal Community.

Link to Methods Guide