Key Words: Introduction of crab species, Barents sea, genetical and ecological effects
The Red king crab (Paralithodes camtschatica) was intentionally introduced from the Sea of Japan to the Barents Sea in the 1960ís. Since that time, this species has not only successfully survived, but the population is growing in number as well as increasing the distribution range. In 1996, the first discovery of the occurrence of Snow crab (Chionoecetes opilio) was made in the Barents Sea area by PINRO in Murmansk. One female and 4 males were caught, and all males were mature when comparing with biological information obtained from other snow crab populations in other distribution areas. This species has probably been introduced accidentally through ballast water.
Introductions of alien species are considered as one of the main threats for maintaining biodiversity, and any new introduction, intentionally or accidentally, should be carefully monitored. In light of this it is of uttermost importance to explore and elucidate the genetical and ecological effects of the "new" crab species into the new areas. Obviously there will be competition with other crab species in the area for food, shelter etc, but likely also with commercially exploitable species as capelin (Mallotus villosus), cod (Gadus morhua) and wolf fish (Anarchichus minor and A. lupus).
The genetic characterisation of introduced populations and comparisons with donor populations must be done. The level of genetic variability can be important for new adaptations and potential spread into new areas. At present, little information is available about potential ecological effects of the introduced crab species into the Barents Sea region. Long-time bottom-trawl records at IMR and PINRO can, however, be evaluated to look for any changes after the introduction of King crab in the Barents Sea. Further, fish eggs are found in stomach of the king crab, and the distribution range overlaps with important spawning grounds of capelin in Finmark. Thus, a more detailed investigation to assess predation on capelin eggs, and compare with previous information of the spawning area is needed to be conducted. Further, management and legislative approaches will be outlined.
Author to Contact: G. Dahle
Institute of Marine Research
Department of Aquaculture
P.O. Box 1870 Nordnes
N-5024 Bergen NORWAY
T +47 5523 6349
F +47 5523 6379
Email: geir.dahle@imr.no
Key Words: nonindigenous pathogenic virus, ecological risk assessment, shrimp, stakeholders
Public concerns over the potential introduction and spread of nonindigenous pathogenic shrimp viruses to shrimp aquaculture and to the wild shrimp fishery in the U.S. are increasing. Although these viruses pose no threat to human health, outbreaks on U.S. shrimp farms, the appearance of diseased shrimp in U.S. commerce, and new information on the susceptibility of shrimp and other crustaceans to these viruses prompted the Federal Interagency Joint Subcommittee on Aquaculture (JSA; National Science and Technology Council) to initiate an ecological risk assessment. The risk assessment process considered both EPAís Guidelines for Ecological Risk Assessment and the Aquatic Nuisance Species Task Forceís Generic Nonindigenous Aquatic Organisms Risk Analysis Review Process. The JSA presented a preliminary report (Shrimp Virus Report), structured according to the problem formulation phase of a risk assessment, to stakeholders in the shrimp industry, several state and Federal agencies, environmental organizations, and the public, at meetings held around the southeastern U.S. and the Gulf of Mexico. Subsequently, under the auspices of the JSA, the EPA sponsored a qualitative ecological risk assessment conducted by a group of scientific and technical experts at a public workshop. Here, we describe workshop conclusions regarding risks associated with shrimp viruses, and preliminary results of a risk management workshop. We also identify lessons learned during the stakeholder process, and the strengths and limitations of the overall approach for assessing the risks of biological stressors over a large geographic region.
Author to contact: H. K. Austin
U.S. EPA, Office of Research and Development
National Center for Environmental Assessment (8601D)
401 M Street SW, Washington D.C. 20460
T 202-564-3328
F 202-565-0062
E-mail: austin.kay@epamail.epa.gov
The polychaeta fauna of the benthos and fouling of the north-western part of the Sea of Japan was studied during the period of 1971-1998. Three introduced species of polychaetes: Hydroides elegans (Haswell), Polydora limicola Annenkova, Pseudopotamilla occelata Moore were found. H. elegans was discovered only on the artificial surfaces in Zolotoy Rog Bay (port Vladivostok), where this species may occur because of "thermal pollution" due to the discharge of warm waters of the water cooling system of Thermal-Electric Power Station-2 (TEPS-2) in Vladivostok which has been in function since 1971. The abundant population H. elegans exists in the bay throughout the year and is capable of reproduction. The biomass of H. elegans may reach several kg/m2 in August - September. P. limicola was found at the same time in the fouling of hydrotechnical structures of Vladivostok, Nakhodka, Holmsk and Uglegorsk ports with a biomass of 1-3 kg/m2. Slow introduction P. limicola occurs by coastal sail ships at present.
The invasion of P. occelata into the Peter the Great Bay may be an example of introduction and subsequent naturalization, which produced considerable changes in the structure of benthic communities. The three species of polychaetes sessile organisms and their invasion occurred by ocean and coastars sea-going ships (unintentional transport vectors). H. elegans and P. occelata were most probably transported to the north-western part of the Sea of Japan from Japan, and P. limicola from the Kamchatka Peninsula.
Author to contact: E.V. Bagaveeva
Institute of Marine Biology
Far East Branch of Russian Academy of Sciences
Vladivostok, 690041
RUSSIA
Key Words: Carcinus, population bottleneck, population genetics, microsatellite DNA
Analysis of molecular genetic variation in introduced and native populations can help to localize the geographic sources of biological invasions and can provide insight into gene and population dynamics associated with successful invasion events. The multiple worldwide invasions of the European green crabs of the genus Carcinus provide an excellent model system to evaluate the utility of a molecular genetic approach for the study of marine invasions. We developed five polymorphic microsatellite DNA markers for green crabs to complement concurrent analyses of mitochondrial DNA. Our nuclear DNA analysis was unable to confirm hypotheses that South Africa and Japan were multiply invaded by the sibling species C. maenas and C. aestuarii, as was suggested by mitochondrial DNA analysis. Similarities in allelic composition indicate that the west coast of North America was invaded by green crabs that originated from an introduced population on the eastern North American coast, while crabs in Tasmania appear to have originated from an introduced population in Australia. Significant population structure was not detected among samples of native crabs from the Atlantic coast of Europe, precluding geographic localization of the native sources for C. maenas invasions.
Invasions were accompanied by large reductions in average heterozygosity and the average number of segregating alleles per locus. Average heterozygosity for introduced populations was 7 to 31% less than for native populations. Invasions that were inferred to have proceeded in a stepping stone pattern showed serial reductions in genetic diversity with each step. The magnitude of heterozygosity losses for introduced populations is consistent with extremely small founding population sizes (2-20 individuals) and/or genetic bottlenecks that lasted for several generations. Current work is focussed on the use of explicit population genetic models and Monte Carlo simulation techniques to more precisely estimate founding population sizes and post-invasion population dynamics.
Author to contact: Mark J. Bagley
Department of Animal Science
University of California, Davis
Davis CA 95616
T 530-752-6351
F 530 752-0175
Email: mjbagley@ucdavis.edu
Key Words: estuaries, oysters, disturbance, indigenous species
The Olympia oyster, Ostrea conchaphila (=lurida) is native to the Pacific coast of North America. Although it survives in full seawater, significant populations occur only in estuaries with stable euryhaline zones (22-28 ppt). South of Washington State, such estuaries are sparse and often highly isolated. These habitats formed from drowned valleys during post-glacial sea level rise, and some have subsequently been altered by natural sediment deposition which eliminated the euryhaline zone and O. conchaphila populations. One such habitat appears to have been Coos Bay, Oregon, in which O. conchaphila thrived in the late Holocene, but went extinct prior to European settlement. A major deliberate inoculation of O. conchaphila from another estuary in 1917 failed to reestablish this species in Coos Bay. In 1987, however, following many years of minor accidental inoculations via shellfish transfers (of nonindigenous, cultured Pacific oysters, Crassostrea gigas) from other estuaries, O. conchaphila reestablished in Coos Bay, and has maintained a large population since then.
The adult distribution of O. conchaphila in Coos Bay is clearly correlated with salinity distribution patterns of a stratified estuary. Based on bathymetry and early salinity data, salinity distribution in Coos Bay has changed markedly since 1917, due to channel dredging. The main channel depth has more than doubled, permitting high salinity to intrude and again producing a stable euryhaline habitat suitable to O. conchaphila, similar to the situation prior to natural sediment deposition. Natural events created and then destroyed a habitat for a native species. Human activities of a "destructive" nature (dredging) have apparently restored this habitat for O. conchaphila. Furthermore, the mostly likely vector for reestablishment of this native species is shellfish transfer, more often associated with accidental introduction of harmful nonindigenous species.
Author to Contact: Patrick Baker
Dept. Ecology and Evolution, State University of New York
Stony Brook, NY 11794-5245
516-632-8589 Fax: 516-632-7626
Email: bakerp@life.bio.sunysb.edu
Key Words: European Green Crab, Carcinus maenas, Oregon, invasion
Since its first discovery in Coos Bay, OR in 1997, Carcinus maenas, is now found in at least five Oregon estuaries: Coos, Alsea, Yaquina, Netarts and Tillamook. Exuvia were found in three more: the Coquille, Siletz and Salmon estuaries. All the Carcinus maenas found in Coos Bay in 1997 were large crabs, ranging in size from 54-86 mm CW (carapace width). We estimate that they represent the 1995/1996 year class. Similar sized crabs were found in Tillamook and Netarts Bays this year. During the summer of 1998, a new year class appeared in Oregon estuaries as well as in Humboldt Bay, CA to the south and Willapa Bay and Grays Harbor, WA to the north. These crabs averaged 14 mm CW in June, 27 mm in July and 48 mm in August. This coast-wide colonization event is correlated with unusually strong northward moving coastal currents off the Oregon coast from September 1997 to spring of 1998. Transport of larvae from well established populations to the south, rather than oyster transport, appears to be the dominant mechanism for the appearance of this new year class.
Author to Contact: Sylvia Behrens Yamada
Zoology Department, Oregon State University
Corvallis, Oregon 97331-2914
T 541-737-5345
F 541-737-0501
Key Words: polychaetes; shellfish culture; oysters
The introduction of seed stocks of nonindigenous commerical shellfish has acted as a vector for the introduction of exotic marine invertebrates into U.S. coastal waters. The most important consumable oysters in U.S. restaurants are not indigenous. On the Pacific coast, the Japanese Oyster, Crassostrea gigas has been cultivated for more than 50 years. Formerly, seed stocks were imported from Japan and set out on tidal flats to grow and mature. On the Atlantic coast, the European Oyster, Ostrea edulis was imported in a similar manner. Although modern culture methods include rearing of larvae in local laboratories rather than importation of juveniles, there is considerable evidence that many species of polychaetes were probably imported with the oyster seed stocks. The distribution of polychaetes by this vector may account for the wide distribution of some species. Two types of polychaetes are capable of transportation with seed stocks: (1) shell borers that form tunnels or channels in the shell itself; and (2) soft-sediment worms that are transported in mud on and between the shells. Shell borers that appear to have been transported in this manner include: Polydora websteri and P. brevipalpa. Sediment dwellers include: Polydora cornuta, Pseudopolydora kempi, P. paucibranchiata, Phyllodoce mucosa, Harmothoe imbricata, and Nereis succinea. An additional mode of transportation is with the direct importation of marketable products from a source country to a host country where the shellfish is sold in local markets. For example, in the early 1980's large specimens of a nonindigenous shell boring spionid, Boccardia acus, were found in a New Zealand mussel that was for sale at a fish market in Honolulu. This review suggests mechanisms of establishment for several nonindigenous species of marine polychaetes and recommends strong quality control measures intended to protect local shellfish from damage caused by exotic shell borers.
Author to Contact: James A. Blake
ENSR Marine & Coastal Center
89 Water Street
Woods Hole, MA 02543
T 508 457-7900
F 508 457-7595
Email: jablake@ix.netcom.com
Key Words: Hemigrapsus sanguineus, crab, molluscs, macroalgae, prey preference, predation
The prey preferences of the recently-introduced Western Pacific shore crab, Hemigrapsus sanguineus, were investigated to gain insight into the crab's potential to alter New England rocky intertidal ecosystems through predation. Laboratory experiments were conducted to determine prey preferences of the crab feeding on molluscs and macroalgae of the area. H. sanguineus were collected from the rocky intertidal zone of two southeastern Massachusetts sites from June to October 1998. Prey selection was examined in relation to mollusc prey of different size and species. Crabs of three size classes (12-18mm, 19-25mm, 26-31mm) were offered three mollusc species: the bivalves, Mytilus edulis and Mercenaria mercenaria, and the gastropod, Littorina littorea. Equal ratios of prey from three size classes were offered concurrently to indicate size preference. In another set of experiments, equal ratios of each species of the preferred size were offered simultaneously to determine species preference. When presented with a range of prey sizes, crabs selected small sizes, male crabs opening larger sizes than females. Crabs offered macroalgae in both multiple-choice and no-choice experiments readily consumed green algae in the laboratory. Enteromorpha spp., Ulva lactuca, Codium fragile, Chondrus crispus, Polysiphonia spp., Fucus spp., and Ascophyllum nodossum were presented to individual crabs separately to determine consumption rates and together to ascertain species preference. Additional feeding trials will examine the crab's preference for animal or plant material by presenting individual crabs with both mollusc and macroalgae species found to be preferred by previous experiments.
Author to Contact: Paul Bourdeau
Center for Marine Science and Technology (CMaST)
University of Massachusetts Dartmouth
706 Rodney French Blvd.
New Bedford, MA 02744-1221
T 508-910-6312
Email: pbourdeau@umassd.edu
Key Words: Hemigrapsus sanguineus, population genetics, RFLP, biological invasions, crabs
The shore crab, Hemigrapsus sanguineus, native to the western Pacific Ocean, was first discovered in the eastern United States in September, 1988 in Cape May County, New Jersey. Since then, H. sanguineus has been found in coastal areas from southeast Massachusetts to North Carolina. H. sanguineus was likely introduced via ballast water from ships traveling from the western Pacific. Introduced species often have detrimental ecological effects on their new environments. Understanding the mechanisms of species introduction and their subsequent spread is very important. Restriction enzyme digest patterns of mitochondrial DNA obtained from individuals collected in Massachusetts, New Jersey, North Carolina, and one location in Japan are being compared. The hypothesis of multiple introductions predicts that the patterns obtained from crabs from at least two locations will be distinctly different. The degree of difference will be used to infer the degree of allelic variation within and between the populations. The presence of near-identical patterns from individuals along the East coast will support the hypothesis that either a single introduction of H. sanguineus, or multiple introductions from the same source, has occurred. Primers specific for the mitochondrial cytochrome c oxidase subunit I (COI) gene successfully amplified a 700 bp region of DNA from individuals from Massachusetts. Seven of twelve assayed restriction digests of this PCR product showed multiple bands and can be used for genetic comparison. Currently the study is being extended and DNA from 30-50 individuals from each sampling location will be amplified with COI primers, and will subsequently be restriction digested with the same 12 enzymes. Sequences of PCR product from a few individuals from each location will also be obtained to confirm that the region being amplified is COI, and to compare sequences to each other and to results from restriction enzyme digestions.
Author to Contact: Michael D. Brandhagen
Department of Biology
University of Massachusetts, Dartmouth
285 Old Westport Road
North Dartmouth, MA 02745-2300
T 508-999-8950
F 508-999-8196
Email: mbrandhagen@umassd.edu
Key Words: Japanese shore crab, food preferences, predator, Long Island Sound
The Japanese shore crab (Hemigrapsus sanguineus), a recent introduction to the Atlantic coastline, has been extending its range since its first recorded appearance in Cape May, New Jersey in 1988 (Williams & McDermott, 1990). Breeding Populations of H. sanguineus are now well-established in western Long Island Sound (pers. observ.) and its appearance has been documented at least as far north as the Cape Cod Canal (Lafferty & Kuris, 1996). Very little is known about the ecological impact this invader is having on the indigenous biota, but indications are that it could be significant. This study presents preliminary information on the food preferences of the Japanese shore crab in western Long Island Sound based on gut content analyses and food choice experiments conducted in the laboratory.
Pairwise choice experiments on four of the most common intertidal macroalgae in western Long Island Sound indicate the following preference hierarchy: Enteromorpha ssp. > Chondrus crispus > Ulva lactuca > Fucus vesiculosus. Crab algal consumption rates do not appear to be a function of crab size (carapace length). Experiments designed to investigate possible predatory habits of the Japanese shore crab, demonstrated that in addition to feeding on macroalgae, H. sanguineus will prey on a variety of bivalve seed, including Mya arenaria, Mercenaria mercenaria and Crassostrea virginica. These findings support the conclusion that the Japanese shore crab is omnivorous in habit and may represent the latest addition to a growing list of bivalve seed predators along the east coast of the United States.
Gut content analyses of wild-caught crabs were also
performed on H. sanguineus and the two most common co-occurring
species of mud crabs. (Eurypanopeus depressus and Panopeus
herbstii) to determine degree of dietary overlap with the Japanese
shore crab. Macroalgae were found to make up a large part of the
gut contents of both H. sanguineus and E. depressus,
suggesting that these two species may be competing for similar food
resources, whereas P. herbstii guts contained large amounts
of barnacle shell fragments indicating that they focus primarily
on animal food items. Author to contact: Diane Brousseau
Biology Department
Fairfield University
Fairfield, CT 06430
T: 203-254-4000
F: 203-254-4253
Email: brousseau@fairl.fairfield.edu
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