The Story of the Invasive Asian Shore Crab

      Hi! My name is Christian Herbosa. You may remember me from the blog post on the American Eel. Here's what I have to say about the Asian Shore Crab:
      The Asian Shore Crab is one of many invasive species that have successfully established colony populations in North America. An invasive species is an introduced species or a non-indigenous species that invades a habitat outside of their native range. These invasive species can have a negative environmental, ecological, or economic affect on the habitats they invade. Invasive species can come in all life forms: animals, plants, or in this case crabs.
      The Asian Shore Crab is native to the Western Pacific from Russia to Hong Kong including the Japanese Archipelago. Their enormous native range is largely due to their diet. They are opportunistic omnivores meaning they'll eat most things: microalgae, salt marsh grass, larval/juvenile fish, invertebrates, and more. Their flexible diet is also one of the main reasons why they were able to successfully invade the Eastern Seaboard of North America, despite the differences in ecology from the Western Pacific.

      It was first seen in North America in 1988 on the shores of New Jersey. It is widely believed that these critters found their way to the East Coast in the ballast water of a shipping vessel. Ballast water is held at the bottom of cargo ships in the ballast tank. The ballast water is used to lower the center of gravity of the ship in order to provide adequate stability after they drop off their cargo. So cargo ships will take on large amounts of coastal water into their ballast tank after they unload their cargo, then discharge their ballast water at their next port of call.

      The first Asian Shore Crab colonizers were probably taken onto a cargo ship in ballast water from the Western Pacific. These individuals then journeyed across the Pacific to the Atlantic in the ship's ballast tank to be discharged on the East Coast. This is the story of many invasive marine species including: the Zebra Mussel, several strains of Cholera, the European Green Crab, and many more.

Nonnative Range of the Asian Shore Crab

      Since their invasion in 1988 the Asian Shore Crab has grown in population and range. Similar to their vast native range, these invasive crabs have established a extensive nonnative range on the East Coast stretching from North Carolina to Maine. Their introduction to the coastal ecosystems of North America has had a negative affect on the populations of the native marine species. The Asian Shore Crab threatens native species directly through predation and indirectly through competition for limited food sources. By disrupting the balance of the food chain, they pose a serious threat to a wide variety of native species including commercially viable crabs, shellfish, and fish. The overarching threat that Asian Shore Crabs and other invasive species pose is a threat to the biodiversity of the invaded habitats, which is crucial to the health of the native ecosystem. Invasive species in worldwide threaten biodiversity on a global scale. The aggregate quantity of invasive species has increased along side of our increasingly globalized society. A decrease in the global levels of biodiversity could have disastrous effects on the global ecosystem.
      So what do we do?!?! Well, once an invasive species has established itself, it is incredibly difficult (if not impossible) to get rid of them. So the best environmental policy response should be a forward thinking one. First, we should prevent the spread of invasive species in the future. Ballast water has been identified as the cause for a number of invasive species introductions. We must prohibit or treat the discharge of ballast water in nonnative areas.

      The second step is to mitigate the damage done by the these invasive species. We can limit or reverse the growth of invasive species by intervening in a number of ways. However these mitigation efforts can be costly. For example, removing the invasive water chestnuts from the Mystic and Charles Rivers has involved an enormous amount of volunteer and local government effort. As with many invasive species mitigation efforts, it is an consistent uphill battle with no end in sight.
      One solution that has been suggested for the Asian Shore Crab and many other invasive species is to eat them. Introducing invasive species to our diets could be one of the more commercially viable and tasty solutions. The members of this new environmentally responsible food movement to eat invasive species call themselves invasivores. Asian Shore Crabs are even on the menu at Miya's Sushi, a restaurant in New Haven Connecticut. You can find recipes for Asian Shore Crabs here.
       Another commercially viable option for the mitigation of the Asian Shore Crab is to use them as a replacement for Horseshoe Crabs in the bait industry. Thi Tran, one of Save the Harbor/Save the Bay's former Harbor Explorers, found Asian Shore Crabs as a useful replacement bait on one of our summer excursions to George's Island: read about it here! Asian Shore Crabs have attended many of Save the Harbor/Save the Bay's youth beach programs. While they represent a fun part of our summer youth programs, we feel that it is important to educate the youth and the general public about the environmental threat that they represent. In the summer of 2011, we conducted a research project to find out how the Asian Shore Crab has established its populations in the Boston Harbor. Our findings are pictured above to the right. To lean more about our research on Asian Shore Crabs in the Boston Harbor click here.

To learn more about Asian Shore Crabs and the Invasive Species Problem, explore these links:

• More information about the Invasive Asian Shore Crab
• Wikipedia page on Ballast Water and Environmental Concerns
• Wikipedia page on Invasive Species
• Wikipedia page on Biodiversity
• Recipes for Invasivores
• I personally recommend Eating Aliens by Jackson Landers a book about hunting and eating invasive species

The American Eel

            As an Environmental Policy Intern here at Save the Harbor/Save the Bay, I felt compelled to write a blog post about one of the most important creatures in the Boston Harbor, the American Eel. While these may be among the most slippery and slimy critters you've ever seen, they also play a crucial role in the ecosystem of the Boston Harbor as well as an important source of income for many New England fishermen. My name is Christian Herbosa, and I speak for the eels.
             The American Eel is a migratory species of eel that can be found along the North American East Coast. American Eels are also known as the “glass eel”, “elvers”, or (if you’re a sushi eater) you may know them as unagi. These Eels spend most of their lives in freshwater rivers and estuaries along the East Coast, however they leave these habitats and travel thousands of miles to spawn in the Sargasso Sea. In the Sargasso Sea, a region of the North Atlantic, these eels lay eggs in a massive seaweed mat located east of the Bahamas. After these eggs hatch they make their way back to the freshwater rivers and estuaries along the East Coast where they can mature from juveniles to adult American Eels. These eels have a relatively slow rate of maturation needing 24 or more years before they reach sexual maturity.

           Eels are collected from their freshwater habitats on the East Coast in their juvenile stage. As juveniles they are generally 3 inches long and have translucent skin. After they are collected, they are sold to eel farms in China and other Asian countries where they mature to be about 3 feet long. Once they reach an ideal size they are harvested and sold for human consumption. American Eel is popularly served in the sushi dish unagi or in the grilled eel dish called kabayaki. Additionally, juvenile eels are also useful as fish bait.
            Until recent years there were only a handful of fishermen in Maine and South Carolina who were interested in the American Eel. However the demand for American eels increased after two developments in the eel trade. First, the global supply of eels available for trade decreased sharply after the 2010 European Moratorium on Exporting Eels. Second, a tsunami hit Japan in 2011, which severely damaged their eel stocks. After these events the price of juvenile American Eels skyrocketed. The price of baby American Eels increased from $25 per pound in 2003 to $1,997 per pound in 2012.

            As a result of the drastic increase in price, formerly small time fishermen were able to make a fortune. One fisherman allegedly made $200,000 in a night on the Penobscot River. The big profits sparked a gold rush of eel fishing. Unsurprisingly, these profits were followed by reports of historically low US eel stocks. In 2012 an assessment done by the Atlantic States Marine Fisheries Commission found that eel stocks were depleted in US waters. Since the Commission has passed several Addendums to the Interstate Fishery Management Plan to restore and protect the eel fishery on the East Coast using quotas to limit the harvest.

            The increased monetary value of these eels has created a very serious eel poaching problem along the East Coast. There have been several instances of large scale poaching in New England. In Massachusetts, it is illegal to harvest eels. The Massachusetts Environmental Police has deployed coastal officers to search for poaching activity in river from Cape Cod to the North Shore, nevertheless poaching persists. Part of the challenge in enforcing poaching restrictions is that it is relatively cheap and easy to catch baby eels. They are easy to intercept as they travel upstream from the ocean. Eel fishing gear often only includes mesh nets, waders, and a holding tank. No boat is necessary for eel fishing, which allows eel poachers to go about their business fairly discretely.

             Eels are also threatened offshore in their breeding grounds in the Sargasso Sea.  The Sargasso Sea is located within the North Atlantic Subtropical Gyre. The defining characteristic of the Sargasso Sea is that it is constituted of Holopelagic Sargassum, a free-floating algae. When the eels are sexually mature they migrate to the Sargasso Sea to lay buoyant eggs in this massive mat of seaweed. In the seaweed mat of the Sargasso Sea the eggs have a safe place to hatch. Once they enter their larval stage they begin their journey along the Gulf Stream to reach the coastal rivers and waterways along the East Coast where they can mature.

            These eel breeding grounds in the Sargasso Sea are threatened by a number of factors. As you may expect, major threats facing the Sargasso Sea include climate change and ocean acidification. Both land and sea based pollution are also a serious concern. Additionally, sargassum seaweed, which is an invaluable habitat for a number of marine species, is harvested to be used as a fertilizer and for the production of biofuels. The main impediment to protecting the Sargasso Sea and the marine life that it supports is the fact that the majority of the Sargasso Sea lies beyond the jurisdiction of any nation in international waters. The Sargasso Sea needs an international organization to conserve and protect its marine habitat.

            The Sargasso Sea Alliance, a partnership led by the Government of Bermuda, is leading the international effort to establish an institution to protect and manage the Sargasso Sea. The organization refers to the Sargasso Sea as “the golden floating rainforest of the Atlantic Ocean.” This organization fights for the international recognition of the Sargasso Sea as a habitat that serves a number of vital ecological functions for a diverse range of marine life including breeding grounds for the American Eel.

            In the Boston area, American Eels can be found in both the Mystic and Charles River.The Mystic River Watershed Association monitors American Eels as the pass the Upper Mystic Lake Dam. The MRWA recorded 2,908 eels in 2012, and they recorded 12,965 eels in 2013. One unique challenge that eels in the Mystic face are low oxygen levels that are created by the invasive Water Chestnut.
            The eels in the Charles have become celebrities at Save the Harbor/Save the Bay's youth summer programs. These slippery, slimy creatures are an integral part of the Boston Harbor Explorer's Community Boating event. Look at the eels that these harbor explorers caught at this link!
            Declining populations of American Eels can have negative ecological and commercial consequences. These eels constitute an important part of the diet of a wide range of fish and wildlife. They are a particularly important food source for commercial and recreational fisheries. Eel conservation is a particularly difficult task given their enormous migratory range.  Efforts to restore and protect American Eel populations must take place in both domestic and international forums. The survival of the American Eel is in everyone’s best interest.

To learn more, explore these links:

• Eels in the Boston Globe
• Eels at boston.com
• Pictures of eels
• Eels in the Mystic
• Eels in the Charles
• Eel poaching on Cape Cod
• Massachusetts Division of Marine Fisheries Report (eels on page 9)
• Atlantic States Marine Fisheries Commission American Eel Report
• ASMF American Eel Fishery Management Plan
• Sargasso Sea description
• Sargasso Sea Alliance