Wellfleet Bay Horseshoe Crab Surveys (from the August 28 edition of Bird's Eye View)

Summer is heating up and so are horseshoe crab counts in Wellfleet Bay. Research interns Katherine Terkanian and Sarah Martinez have been working hard since January to get a grasp on the number of horseshoe crabs in our backyard through three separate, yet intertwined, research projects.

Adult spawning surveys were conducted around the new and full moon cycles in May and June during high tides. Over 50 much appreciated volunteers took time out of their schedules to help out in all types of weather and at all times of day. Surveys were conducted in cold water, in pouring rain, and even at one in the morning! Despite possible unfavorable conditions, seeing pair after pair of mating horseshoe crabs was worth it. Although not all results for this year have been calculated, we have crunched some numbers. We found a total of 814 crabs: 544 males and 265 females. Our overall density of crabs was 0.175 crabs per 5x5 meter quadrat, and our spawning index was 0.060 female crabs per 5x5 meter quadrat. Since this is the first year of the study, we are unsure if the number of crabs in Wellfleet Bay has increased or decreased. We’ll let you know next year!

Juvenile surveys were conducted in May and June and will continue through July and August during low tides. We are happy to say that there are many three to six year-old crabs in our creeks. We have also started to find tiny crabs that were potentially hatched this year. Good luck finding them on your own; they’re about the size of the O on a standard computer keyboard!

When we find spare time between surveys and the occasional nap, we’ve also been tagging adult crabs. We drill a small hole in the back of the shell and insert a tag. This does not hurt the crab, and does not affect them during molting because adult crabs do not molt. To date, we have tagged 739 crabs—mostly males. Females were harder to tag because they were usually in mating pairs and could not be disturbed while spawning. All tagged crabs are measured, and their condition is recorded and some are even given names! Keep an eye out for long, bright orange tags on local crabs. If you find one, write down the time, location, and of course tag number and give us a call. Thanks to a public effort, 66 crabs have been recaptured.