The bright summer sun shines over the small beach town of Coos Bay, Oregon on an early July morning. The only clouds in sight are at the far end of the sky, a soft wind blows through the air and a distant rumble comes from the commercial boats floating nearby in the marina. This is Charleston, Oregon, home of the Oregon Institute of Marine Biology where scientist Dr. Alan Shanks performs extensive research on Cancer Magister, the Dungeness crab.

Dr. Shanks pulling his home made megalopae trap from the local dock.

Dr. Shanks walks down one of the many docks towards the far end where he has a trap waiting. The traps are surprisingly low-tech -- typically consisting of an old plastic water jug with a few strategic holes cut in the sides, and a light stick resting in the center. He reaches down for a rope tied to the far corner of the dock and begins to pull the contraption to the surface. Shanks is sampling larval Dungeness crab called megalopae, tiny crab-like creatures that swim with tails that will be repurposed as they continue to mature. Megalopa, the second stage in a hatched crab’s life cycle represents the crab’s transition from larval to a recognizable juvenile crab. The tail will disappear in the next stage, folding in under the body to become the breastplate of a mature crab.

Since 2006, Shanks has been funded by the Oregon Dungeness Crab Commission (ODCC) to report the data he collects on these small crustaceans. The ODCC is headquartered in Coos Bay, Oregon and regulates the commercial crabbing industry for the entire state. The commission aims “to enhance the image of the Dungeness crab industry, and to increase opportunities for profitability through promotion, education and research.”

Dr. Shanks and the ODCC have developed a close relationship in which he reports his yearly catch of megalopae for commercial catch insight. Although fisherman do not catch Dungeness crab at this early life stage, Shanks predicts the commercial catch numbers four years later with his own catch of megalopae. He has noticed throughout his 20 years of sampling that there is a strong translation (>90% variation) between the spring transition and the number of megalopae he has caught.

Macro images of the Dungeness crab in the megalopa stage with a visible tail.

The California Current runs southward down the west coast between latitudes 48 N and 23 N during the spring and summer months. The Davidson Current develops during the winter months, when upwelling has ceased. Due to the winds reversing in direction, the Davidson Current pushes the California Current outwards towards the continental shelf.

Current illustrations provided by Dr. Alan Shanks

This creates an opportunity for the young megalopae to be carried onto the continental shelf from deeper waters. The sooner the spring transition, the more likely they are able to continue their life cycle. As they are transported onto the shelf, they avoid predators in the plankton and make their way to the shore in higher numbers where Dr. Shanks can sample them.

The Dungeness crab population continues to thrive despite the intense commercial demand. The fishery hasn’t collapsed because the regulations on size, sex, and season, match the life cycle of the crab. Only male crabs with shells over the size of 6 ¼ inches are allowed to be kept on boat; this leaves an approximate 70-80% of the crab population uncaught when the fishing season comes to an end.

Female crabs produce up to 2.3 million eggs annually, and male crabs mate with multiple females which ensures that close to all females mate each year. Since only male crabs can be caught, there is no impact on the number of eggs produced. This results in a new population of young crabs that will never dwindle due to overfishing. For a male crab to reach the size requirement, they grow for around 4 years, which enables the males to mate two to three times before they are potentially caught. In addition, male crabs are sexual mature after a year and a half, and since they are caught at 4 years old, the fishery leaves an untouched breeding population.

Turquoise Pacific Seafood bins stacked along the unloading dock in Coos Bay, Oregon. Pacific Seafood is a distributor of Dungeness crab in the region.

However, at first, the crab population was not so stable. When fishing began in 1848, crabs were not sought out by fisherman, but were rather by-catch in other fisheries in the San Francisco Bay. By 1860, the commercial industry was in full swing - but with regulations. All of the Dungeness crabs were caught in the San Francisco Bay, since offshore fishing was prohibited. Soon after, the Dungeness crab population depleted, and the fishery had no choice but to search in different waters. At the time, it was also illegal to sell deceased crabs, or transport them outside of California, which limited the fishery to Northern California, since few people financially supported the crab market.

Original wooden boats with hull design in San Francisco Bay Photo by J.B. Phillips, 1934.

Image courtesy of Dr. Alan Shanks

Soon, changes began to occur within the fishery. There was a replacement of the hoop trap with the cage trap. In 1897, it became illegal to take female crabs since the canneries did not want to deal with crabs under a certain size. Dungeness crabs exhibit sexual dimorphism, where the two sexes display differences beyond sexual organs. It became apparent later that this helped secure the Dungeness crab population. At the turn of the century, a closed fall season was established (Oregon's current fishery is open December 1st - August 14th). By 1905, a size limit was set - 7 inches (now 6 ¼) from spine to spine tip for male crabs, and in 1917, a state law prohibited the exportation of crabs outside of coastal California, but was later removed in 1940.

In various other fisheries, current regulations are not strong enough to limit fishing capacity to a sustainable level. At times there is a failure to follow scientific advice provided for fish quotas, and catch limits are set above the maximum amount. Most other fisheries regulate in opposite models to that of the Dungeness fishery. The Dungeness fishery leaves a sizable population each year, whereas other fisheries catch up to 80% of the mature population in a given year. This was the case for the collapsed Atlantic cod fishery in 1992 due to overfishing and the ignored concerns of marine biologists.

According to Shanks, very few fisheries operate like that of the Dungeness crab in Oregon. Here, the fishing season does not “impact the reproductive potential of the population, have significant problems with by-catch, and damage the environment.”

Designed by Hudson Miller

Words by Meghan Jacinto, Hudson Miller, Xavie Tow & Carl Ranney

Images by Sarah Frimtzis, Hudson Miller, Jeff Dean & Dan Morrison

Historic Images provided by Dr. Alan Shanks

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