The Nature Conservancy on Block Island has a prominent presence. Block Island is often described as microcosm of the world at large. The Island gives scientists, anthropologists, sociologists, naturalists and more the opportunity to study a variety of things to understand the bigger picture along with communities and areas that may be more difficult to perform controlled studies. As a laboratory of the natural world, it is crucial to protect. The Nature Conservancy (TNC) embodies their mission statement to protect and restore natural resources. Examining loss of habitats and other destruction allows organizations like TNC to find new ways to protect, enhance, and maintain the delicate environment acting as home to marine and human life.
On July 13th I was given the opportunity to volunteer with TNC for a few hours while they did their routine fish surveying. They set up fish traps in specific locations throughout the Great Salt Pond and take measurements of life within the pond on a weekly basis year round. Diandra ("D"), who works for TNC and lives on the island year round, is the one who in charge of this collecting and mapping data. She has two assisting interns in the summer season who I had the opportunity to join and experience first hand their daily activities. We got on the TNC's boat that was previously used as a shellfishing boat. We went out into the waters and D explained to me the importance of the Garmin GPS for these studies while also looking at water depth. I was impressed by how the Garmin opened my eyes to how vast and deep the pond actually is. You can of course read water depths in a textbook, but when you see it and experience it in real time, it makes a much larger impact on how you're perceiving it. Thinking about the chart and how it was reading the depth that was directly below us was very cool. The garmin also has the spots where the traps are located down to the latitude and longitude. Ensuring the traps remain in the same location is crucial in keeping the study accurate and controlled. When we got to the traps we pulled them out of the water and transferred what was in them into the large green bucket featured in the picture above. Once all the marine life was in the bucket we documented what species we had- the gender, the length and the weight. On this specific outing we found several spider crabs, a few scup, and a juvenile black sea bass. Crabs were a constant in all locations. We only found fish in the trap near the coast guard station. When D was setting up the study and where the traps should be she considered several factors and one was the accessibility to the traps during the winter months. a few traps are only accessible by boat but a majority are located off docks making them easy to reach during the winter when she wants to limit her time on the water.
Through this trip my knowledge of crabs increased. Spider crabs aren't just called spider crabs because they resemble spiders with their long legs and unsettling aesthetic. They are actually very closely related to the arachnid family. Spiders and Crabs fall into the same phylum known as anthropoidea. They are put here because they all have segmented bodies, jointed legs, and exoskeletons. The biggest difference between crabs and spiders are crabs have a mandible jaw and spiders do not.
I also learned from Diandra that green crabs are one of the largest predators in the Great Salt Pond. They were introduced back when the island was originally settled and were brought over in ballast waters. Humans brought over more than just diseases but they also brought a variety of marine life. Now we consider these a natural species, not invasive. They feed on small fish, shellfish, and other important species that keep the ecosystem of the pond well and thriving. There are people trying to introduce green crabs as something to eat to create a commercial use for them which will in turn curb the population.
This picture highlights the claw length and the mouth location. The mouth of a spider crab is something that will greet me again in my nightmares. It is located on the bottom side of the exoskeleton allowing easier access to debris and other things it would find on the bottom of the ocean. This was a female and was approximately 4cm in size. On this excursion we snorkeled to a trap near Andys Way and when snorkeling I could see crabs crabbing around at the bottom of the sea. I saw the claws picking things up and almost shoveling sand into the mouth. It also made me confirm the fact that I never want to step on the bottom of the Great Salt Pond. Don't want one of those suckers pinching a toe.