The study aimed to improve the efficiency of the Fukui trap for capturing invasive European green crabs by testing modified trap designs. Researchers tested traps with mesh, sinker, assist, and string modifications and found that traps with added weights (sinkers) increased crab catches by 59% while producing limited bycatch, making it the most effective modification. Overall, the modifications increased green crab catches but also caught some rock crabs. The sinker trap design was deemed best for widescale use due to its simplicity, durability and higher catch rates.

1. IMPROVING THE EFFICIENCY OF
THE FUKUI TRAP AS A CAPTURE
TOOL FOR THE INVASIVE
EUROPEAN GREEN CRAB
Presentation by: Wesley Cagle
Based on a Research article by : Jonathan A.
Bergshoeff , Cynthia H. McKenzie, and Brett Favaro

2. INTRODUCTION
• What is the European green crab? (Pictured upper right)
• Invasive species from Atlantic coast of Europe
• Destroy eelgrass beds, prey on native bivalves,
compete with native species like Rock crab (pictured lower right)
• Grow up to 10 cm across and can spawn up to 185,000 eggs per year
• Fukui traps (pictured lower left) had been used to capture green crabs
previously

3. OBJECTIVE
• Main objective from article: “to improve the
performance of the Fukui trap as a capture tool
for green crabs.”
• Plan to reach objective by designing modified
Fukui traps
• Based modifications on previous study where
wild crab and Fukui trap interactions were
filmed

4. METHODS
• Developed four distinct trap
modifications (widest opening)
• Sinker: Three weights were added to
bottom of opening (2 cm)
• Mesh: Mesh screen was added to trap
entrance for more traction(0 cm)
• Assist: Mesh screen strip added past
opening for grip(0 cm)
• String: the top and bottom of opening
held open by strings(6 cm)

5. METHODS
• Experiment conducted in Fox Harbour and North
Harbour, Newfoundland and Labrador
• Ran from June to August of 2016
• Set traps in groups of 5, one of each modified and
one unmodified trap, spaced 10 m
• Baited with cut Herring in perforated plastic bait
container
• Green crabs were
kept to be counted,
sexed, and measured,
all bycatch were
recorded and released

6. RESULTS-BYCATCH
• A total of 17,615 green crabs were captured across 520 trap
deployments
• 174 total bycatch captured including 157 rock crabs

7. RESULTS-TRAP TYPE
• All relative to the standard Fukui trap:
• Mesh, Sinker, and Assist modified traps all saw
increased catch rates
• String modified traps did not show a statistically
significant improvement over the control
• Sinker and string modifications caught larger male
green crabs

8. DISCUSSION-TRAP TYPE
• String modified traps: Least effective in capturing, suspected high
frequency of escapes, easy to install but difficult to empty
• Mesh modified traps: 29% increase in catch, time consuming to
implement
• Sinker modified traps: 59% increase in catch, easiest implemented, most
durable, easily emptied, most effective for large scale
• Assist modified traps: 81% increase in catch, time consuming to install,
lacked durability

9. DISCUSSION-BYCATCH
• All Fukui traps, modified or not, produce very limited bycatch
• The design modifications were made to facilitate crab entry and retention,
which can extend into non-target species
• Traps and pots in general more selective with higher live release rates of
bycatch
• In Sinker modified traps, the mean bycatch rate was .423 bycatch per
deployment

10. CONCLUSION
• Set out to make modifications to the Fukui trap that were simple,
durable, and effective at increasing catch rate
• The sinker modification was found to be the best at meeting these
requirements and has the most potential for widescale use
• The assist modification is great for improved catch rate but needs durability
improvements
• Modifications should be tested in new regions before application
Green crab found on San Juan Island,
Washington state
Green crab caught off the coast of
New Hampshire

11. REFERENCES
Article
• Bergshoeff JA, McKenzie CH, Favaro B. 2019. Improving the efficiency of the Fukui trap as a capture tool for the invasive European green crab
(Carcinus maenas) in Newfoundland, Canada. PeerJ 7:e6308
Images (In order, graphs and tables from article not included)
• https://www.incimages.com/uploaded_files/image/1940x900/getty_515741103_200013351818843106229_new_359310.jpg
• https://reefnation.com/wp-content/uploads/2016/05/Screen-shot-2016-05-24-at-3.27.39-PM.png
• http://www.nlnature.com/observations/827/DSC05969.JPG
• https://dfzljdn9uc3pi.cloudfront.net/2018/4223/1/fig-5-full.png
• http://www.nfl.dfo-mpo.gc.ca/folios/00250/images/green_crab_2.jpg
• http://uhbiology.kahikai.org/?p=1500
• https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSdnAMRSVBaDD4A7oEiBz2EkPKnPzgBSrHGg8bG5auVfS5fTb01qA
• http://3.bp.blogspot.com/-g4YhSkwMT7Y/T0qLgBsEo9I/AAAAAAAAABw/1DORdLD9s4o/s1600/Wanted+European+Green+Crab.jpg
• http://www.iucngisd.org/gisd/species.php?sc=114
• https://wsg.washington.edu/crabteam/greencrab/id/
Addition information
• https://reefnation.com/invasive-european-green-crab/
• https://www.fishaq.gov.nl.ca/research_development/fdp/pdf/rock_crab.pdf

12. QUESTIONS?