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Chinese Mitten Crab ( Eriocheir sinensis)

Chinese Mitten Crab ( Eriocheir sinensis). Reproduction. The mitten crab is Catadromous - adults reproduce in salt water and the offspring migrate to fresh water to rear. Mating and fertilization occurs in late fall and winter, generally at salinities >20‰.

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Chinese Mitten Crab ( Eriocheir sinensis)

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  1. Chinese Mitten Crab(Eriocheir sinensis)

  2. Reproduction • The mitten crab is Catadromous - adults reproduce in salt water and the offspring migrate to fresh water to rear. • Mating and fertilization occurs in late fall and winter, generally at salinities >20‰. • The females carry their eggs until hatching and both sexes die soon after reproduction. • A single female can carry 250,000 to 1 million eggs. • After hatching, larvae are planktonic for approximately 1 to 2 months. • The small juvenile crabs settle in salt or brackish water in late spring and migrate to freshwater to rear.

  3. Mitten Crab Life Cycle Zoeae(marine)

  4. Habitat • In San Francisco Estuary, the mitten crab was first collected in 1992 by commercial shrimp trawlers in South San Francisco Bay. • Juvenile mitten crabs are found in tidal freshwater areas • Usually burrow in banks and levees between the high and low tide marks.

  5. Habitat Cont’d Burrows

  6. Genetics in San Francisco Bay • Haplotype: A set of alleles from closely linked loci carried by an individual and usually inherited as a unit. • Within American samples of the mitten crab, biologists have found only 1 haplotype (ES4). • This discovery indicates that the San Francisco population was established by a single event. Either by eggs that came over on a boat an hatched, or on purpose by humans.

  7. East Coast Invasion • Live Chinese Mitten Crabs (Eriocheir sinensis) have been caught in crab pots in Chesapeake Bay (2005-2007) and Delaware Bay (May 2007). • To date however, there have been only 9 mitten crabs found in the eastern bays. • Establishment of reproduction on the East Coast is unknown to biologists.

  8. 2008 Distribution on East Coast

  9. Migration Patterns • Older crabs are found further upstream than juveniles. • They have been reported several hundred miles from the sea. • We do not understand what cues this upstream migration, although high densities were reportedly a factor. • The upstream migration may be tied to the monsoon season. • Maturing crabs move from shallow areas to the channels in late summer and early fall and migrate to salt water in late fall and early winter to complete the life cycle.

  10. Mitten Crab Introduction to North America • How exactly the mitten crab was introduced to America is still an uncomfirmed issue. • However, some biologists believe it got here by fishery boats. • Other biologists believe it migrated here all the way from Asia.

  11. Impact of Mitten Crab on Humans • The mitten crab is the secondary intermediate host for the Oriental lung fluke. • Humans become infested by eating raw or poorly cooked mitten crabs . • Generally, a fluke parasite will inhabit the digestive system or the lungs.

  12. Impact of Mitten Crab on the Fisheries • Burrowing activity of mitten crabs may accelerate the erosion of banks and levees. • In China and Korea, juvenile mitten crabs have been reported to damage rice crops by consuming the young rice shoots and burrowing in the rice field levees. • Become a nuisance for commercial Bay shrimp trawlers in South Bay. • Shrimp trawlers have also reported that a large catch of mitten crabs damages and even kills the shrimp, making them unsuitable for the bait market. • In the Delta, the mitten crab may reduce abundance and growth rates of the introduced signal crayfish (Pacifastacus leniusculus), which supports a commercial fishery.

  13. Ecological Impact • Although juveniles primarily consume vegetation, they do prey upon animals, especially invertebrates, as they grow. • A large population of mitten crabs could reduce populations of native invertebrates through predation. • Also can change the structure of the Estuary's fresh and brackish water benthic invertebrate communities.

  14. Geographical Range In North America Hydrologic Unit Code (HUC) - a hierarchical classification of drainage basins. An 8 digit HUC indicates region (leftmost 2 digits), a 6 digit sub-region (next two digits), accounting unit (next 2 digits), and cataloging unit (rightmost 2 digits).

  15. Lacey Act Terms • It is illegal to import, transport, or possess live Chinese mitten crabs. • If you keep a mitten crab, it must be dead. • You must posses a valid California Sport Fishing License to fish for Mitten Crabs. • Upstream of the Carquinez Bridge, you can only fish by hook and line and there are no bag or size limits. • Downstream of the Carquinez bridge, you can fish with traps and hook and line, but the limit is 35 per day.

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