Something strange has been going on at the Oregon Coast. Fisher Crabbins takes us out on his boat to his usual crabbing spot. He drops his crab “pot”, or basket with bait, into the water. After waiting, we help him pull it back up onto the boat. But the crab pot is empty. This is bad for the fisherman, who sells his catch to the local restaurants for tourists to eat.
Fisher decides to reach out to a marine scientist, Dr. Seeksalot, at Oregon State because this has been happening more often, especially during the summer. He decides to try another crabbing spot, and takes the boat to a different location. After dropping the crab pot and waiting for crabs to take the bait, he struggles to pull up the heavy crab pot. This time, it’s full of crabs. There seem to be many of them gathered in this location.
Curious, he decides to take the boat back to the first spot he dropped his crab pot. Perhaps we can find a clue about what may be going on. When we arrive, we look down into the water. Where the crabs were gathered, we had seen many fish swimming around. But here the water is empty of fish. He continues to look around, searching for signs of life. The water is murky like broth, and down below, there seem to be a few dead organisms you can’t quite identify.
It looks like marine organisms are struggling to survive in this area. He then contacts the office of a local policymaker, Representative Wordsmith because he is concerned about the economic consequences of this strange phenomenon. In order to figure out what might be going on, we need to get to know the area and check out the available data.
Why do we care about dungeness crabs on the Oregon coast?
Dungeness crab (Cancer magister) is an iconic species of the West Coast, sought after by humans and non-humans alike for their delicious and abundant meat. Considered the most valuable single-species commercial fishery in Oregon, an average of 14 million pounds of crab are caught each season from coastal Oregon and the Columbia River estuary.
The ocean crab season along the Oregon coast begins in late fall and continues through the end of summer. The peak harvest occurs during the first eight weeks of the season with up to 75% of the crabs caught annually during this period.
Source: ODFW
Source: VectorStock
Biology
Life expectancy 8-13 years old but commercially caught crabs are usually about 4 years old.
Claws are used for defense and to tear apart large food items.
As adults, dungeness crabs primarily eat bivalves, crustaceans and fish. As a juvenile it feeds on fish, shrimp, mollusks, and crustaceans.
Predators include: seals, sea lions, a variety of fish and humans.
Adults prefer living in eelgrass beds, sandy or muddy bottom areas.
Source: highwater00 on YouTube
Other fun facts about dungeness crabs:
A female crab can carry up to 2.5 million eggs
Dungeness crabs can live in water and on land. They prefer to live in salty seawater but sometimes come up to the beach to rest under the sun.
Crabs walk sideways, and if they lose a leg, they can grow a new one!
How does crabbing impact Oregon's economy?
On the right is real data for dungeness crabbing in Oregon.
Pounds: cumulative weight of crabs caught in Oregon for a given year
Dollars: total revenue for dungeness crab fishing for a given year
Crabbing brings in a LOT of money in Oregon!
Activity: Let's think money
Here are publicly available data from the National Oceanic and Atmospheric Administration (NOAA) showing the amount of crabs sold and the crab landings per year from 2000 to 2020 in the state of Oregon. Landings are defined as the catches of marine fish landed in foreign or domestics ports.
With this data, do the following:
A. Calculate dollars per pound by year
B. Calculate mean, median and mode for dollars per pound.
C. Graph dollars per pound over time using the downloadable spreadsheet below.
Crab landings_class.xlsx
