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Japanese Shore Crab – Invasive Species – Part 52

Invasive Species in USA Waterways - Part 52

Japanese Shore Crab

Hemigrapsus sanguineus

The Japanese Shore Crab is an invasive species of crab. Native to East Asia from Peter the Great Bay in southern Russia to Hong Kong. Another name includes the Asian Shore Crab.

Invasive Species Definition

The definition of an invasive species is any species that is not native to our ecosystems and cause harm when introduced to the ecosystems. Furthermore, these may include amphibians, plants, insects, fish, fungus, bacteria and more. Impacts on the environment may cause economic loss or affect human health.

While, Invasive species tend to grow and reproduce quickly and spread aggressively with the potential to cause harm on the environment, economy or even human health. Therefore, given the label “invasive”.

Description of the Japanese Shore Crab

Japanese Shore Crab Carapace

Features a square 2-inch wide carapace with three teeth along the forward sides. While, the pereiopods consist of alternating light and dark bands.

Generally, the carapace color ranges from green to purple and orange brown to red. While, it has light and dark bands on the legs and red spots on the claws.

Japanese Shore Crab Underside

Meanwhile, the male crab has a distinctive fleshy, bulb-like structure at the base of the moveable finger on the claws.

Biology of the Japanese Shore Crab

Generally, inhabit intertidal or shallow subtidal zones where water depths are a couple of feet at low tide. Further, tolerates a wide range of salinities and temperatures. Inhabit temperate regions.

Distribution of the Japanese Shore Crab

The native range of the species is from Peter the Great Bay in Southern Russian to Hong Kong. Have been introduced to other areas including Canada, France, Netherlands, English Channel, North Sea Coastline, Germany, Denmark, United Kingdom, Wales, Mediterranean Sea, northern Adriatic Sea, Romanian Coast and the Black Sea. As well as in the United States.

Effect on the Ecosystem by the Japanese Shore Crab

Due to the species wide dietary range, the potential to affect populations of native species of crabs, fish and shellfish is good, especially by disrupting the food web. Furthermore, the crab occupies habitats very similar to native mud crabs, possibly overwhelming and dominating habitats.

Therefore, resulting in direct predation or competition for food sources. Furthermore, they have the potential to compete with larger species like the blue crab, rock crab, lobsters and other non-native green crabs.

Therefore, over the years, the native crab populations have decreased while the shore crab populations have increased. These opportunistic omnivores also pose a threat to coastline ecosystems and aquaculture operations.

Introduction to the USA

Speculation has it that the larvae of the species was brought into the United States by incoming ships of global trade via ballast water discharges. Non-indigenous occurrences in the United States occur in Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Rhode Island and Virginia.

Conservation and Management

Unfortunately, there is currently no control measures for marine animals. Meanwhile, the Japanese Shore Crab is preyed on by rockfish and seagulls. While, parasites help control the populations of this shore crab in their native range, these parasites are not present along the US Atlantic Coast.

Therefore, the spread of the crab along the coastline will continue until it reaches the temperature and salinity tolerance levels. While, scientists are closely monitoring the spread of the crab and conducting experiments to increase their knowledge of the species.

While, ballast water management is being researched to reduce or eradicate new introductions from occurring. However, researchers are looking into the effects of what these parasites could have on the crabs in the Atlantic Ocean.

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