29 research outputs found
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Status of the European Green Crab in Oregon Estuaries during the Summer of 2002
Prepared for the Pacific States Marine Fisheries Commission and the Alaska Department of Fish of Game.The recent invasion of Pacific Northwest estuaries by the European green crab, Carcinus maenas, caused much initial alarm. A large 1997-98-recruitment event resulted in the colonization of estuaries along the coasts of Oregon, Washington, and as far north as Nootka Sound on the west coast of Vancouver Island, British Columbia. So far, green crabs have not been found in the inland sea between Vancouver Island and the mainland.
Monitoring efforts during the summer of 2002 in Oregon and Washington indicate that green crab populations still persist in coastal estuaries, but at much reduced levels. Population densities in all Pacific Northwest estuaries, even at their peak, were well below those observed in Europe, on the East Coast of North America and in Central California. Green crabs grow well in our estuaries and females are capable of reproduction. Recruitment of young green crabs has occurred in some Oregon and Washington estuaries since 1998, but their numbers have been very low. In the summer of 2002, we trapped only one young crab (39 mm carapace width) in Oregon.
The recruitment event during the 1997-1998 El Niño was linked to unusually strong northward-moving coastal currents. At velocities of up to 50 km/day, these currents had the potential to transport larvae from more established populations in California to the Northwest. Coastal transport events have been much weaker in recent years.
Even though green crab abundances are down, it is imperative to continue monitoring efforts for two reasons: 1) to elucidate the process of range expansion of non-indigenous marine species and 2) to serve as an early warning system for the next strong recruitment event of green crabs
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Status of the European Green Crab in Oregon and Washington Estuaries in 2007
Prepared for the Aquatic Nuisance Species Project, Pacific States Marine Fisheries Commission.A strong cohort of young European green crabs (Carcinus maenas) appeared in North American embayments from Oregon to the west coast of Vancouver Island following the strong El Niño of 1997/1998. Unusually strong north-moving coastal currents transported crab larvae from established source populations in California to the Pacific Northwest. Both coastal transport and recruitment of young green crabs have been weaker since. Although it was predicted that green crabs would become extinct in the Pacific Northwest once the original colonists died of senescence at about age six, this has not happened. Age-class analysis and the appearance of young crabs evidence the existence of local recruitment in the Pacific Northwest. Good recruitment in 2003, 2005 and 2006 is linked to warm winters and shore-ward transport in late winter and early spring when larvae are believed to be settling out from the plankton. Recruitment in 2007 was poor but the strong 2005 and 2006 cohorts will assure a larval source until 2012 when the last of these crabs will die of old age.
An extensive survey by Fisheries and Oceans Canada found green crabs in all the major inlets on the west coast of Vancouver Island, but not in the inland sea between Vancouver Island and the mainland. Therefore, outreach efforts should continue to help prevent the establishment of this invader in the latter waters via ballast water or shellfish transport.
Even though green crab abundance in the Pacific Northwest is still low when compared to Europe, eastern North America, Tasmania and California, it is imperative to continue monitoring efforts for two reasons:
1) to elucidate the process of range expansion and population persistence of this model non-indigenous marine species with planktonic larvae and 2) to understand the role of ocean conditions on recruitment strength in order to predict the next strong recruitment event of green crabs
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Status of the European Green Crab in Oregon and Washington Estuaries in 2005
Prepared for the Aquatic Nuisance Species Project, Pacific States Marine Fisheries Commission.The recent invasion of Pacific Northwest estuaries by the European green crab, Carcinus maenas, caused much initial alarm. Following the last El Niño of 1997-98, a strong cohort of young green crabs appeared in estuaries along the coasts of Oregon, Washington, and as far north as Port Eliza on the west coast of Vancouver Island, British Columbia. Unusually strong northward-moving coastal currents (up to 50 km/day from September 1997 to April 1998) must have transported green crab larvae from more established source populations in California to the Northwest. Coastal transport events and recruitment of young green crabs have been much weaker in recent years.
It was hoped that green crabs would go extinct in the Pacific Northwest estuaries once the original colonists reached the end of their life span of 4-6 years and no new larvae arrived from California. This has not happened. Local recruitment has occurred most years since 1998. Recruitment strength is linked to winter temperatures: cold winters (2002) result in poor recruitment while warm winters (2003 and 2005), in good recruitment. As the 1998 year class dropped out of the population, it was replaced by the 2003 year class as the most dominant one. It was found it in the Coquille, Coos, Yaquina, Netarts Tillamook and Willapa Bay estuaries as well as on the northwest coast of Vancouver Island. Even though the 2003 year class was an order of magnitude less abundant than the 1998 one, it produced sufficient recruits in 2005 to maintain the Oregon and Washington satellite population.
There can be a substantial time lag between the discovery of an exotic species and its impact on the native community. For example, green crabs were documented to exist in New England in 1817, but it was not until the 1950’s when this species expanded its range and increased in abundance sufficiently to impact the soft-shelled clam populations in Massachusetts, Maine and Nova Scotia. Even though green crab abundance in the Pacific Northwest is low when compared to Europe, eastern North America, Tasmania and California, it is imperative to continue monitoring efforts for two reasons:
1) to elucidate the process of range expansion and population persistence of this model non-indigenous marine species with planktonic larvae and
2) to understand the role of ocean conditions on recruitment in order to predict the next strong recruitment event of green crabs.
Efforts to educate the general public, including boaters and shellfish growers, not to transport non-native Aquatic Nuisance Species from one area to another should continue to prevent the establishment of the green crab in the inland sea between Vancouver Island and the mainland, including Puget Sound and Hood Canal
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Status of the European Green Crab in Oregon and Washington Estuaries in 2015
The European green crab (Carcinus maenas) has a six-year life span and has persisted at low densities in Oregon and Washington coastal estuaries since the late 1990’s. After the arrival of a strong year class in 1998, significant recruitment to the Oregon and Washington populations occurred only in 2003, 2005, 2006, 2010 and 2015. Warm winter water temperatures, high Pacific Decadal Oscillation and Multivariate ENSO (El Niño Southern Oscillation) Indices, weak southward shelf currents in March and April and a high abundance of southern copepods are all correlated with strong year classes and vice versa (Behrens Yamada Peterson and Kosro 2015). Right now, green crabs are still too rare to exert measurable effects on the native benthic community and on shellfish culture in Oregon and Washington. However, this could change if a high PDO and strong El Niño patterns were to persist. For example, green crabs were first documented in New England in 1817, but it took warm ocean conditions during the 1950’s for their numbers to build to a level at which they decimated the soft-shelled clam industry in Maine.
The Department of Fisheries and Oceans, Canada found green crabs in all the major inlets on the west coast of Vancouver Island and around Bella Bella on the Central Coast, but so far none have been discovered in the inland sea between Vancouver Island and the mainland. Therefore, outreach efforts should continue to prevent the establishment of this invader in these inland waters via ballast water, shellfish transport or other human-mediated vectors. Even though green crab abundance in Oregon and Washington is still low when compared to Europe, eastern North America, Tasmania, California and the west coast of Vancouver Island, it is imperative to continue monitoring efforts for two reasons:
1) to elucidate the process of range expansion and population persistence of this model nonindigenous
marine species with planktonic larvae, and
2) to predict the arrival of strong year classes from ocean conditions and alert managers and shellfish growers of possible increases in predation pressure from this invader
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Status of the European Green Crab in Oregon Estuaries, Fall 2003
Prepared for the Pacific States Marine Fisheries Commission and the Alaska Department of Fish of Game.The invasion of Pacific Northwest estuaries by the European green crab, Carcinus maenas, caused much initial alarm. Following the strong El Niño of 1997-98, young green crabs appeared in estuaries along the coasts of Oregon, Washington, and as far north as Port Eliza on the west coast of Vancouver Island, British Columbia. Unusually strong northward-moving coastal currents (up to 50 km/day from September 1997 to April 1998) must have transported green crab larvae from more established source populations in California to the Northwest. Coastal transport events have been much weaker in recent years.
Crabs from the 1997/98 colonizing year class were still in the population during the early summer of 2003. Males from that year class ranged from 86-98 mm in carapace width. By the fall we did not trap any crabs over 80 mm, suggesting that these older crabs were dying. Estimates for green crab longevity range from 4 years in Europe to 6 years in Maine. We thus predict that most of the colonizing year class will die of senescence over the 2003/2004 winter.
The loss of the 97/98-year class of green crabs, however, does not mean that green crabs are becoming extinct in Northwest estuaries. Recruitment in 2003 in Yaquina, Netarts, Tillamook and Willapa Bay have has been much stronger than in previous years. Circumstantial evidence indicates that these estuaries harbor a small self-sustaining population that is not dependent on a larval source from California.
Even though green crab abundance in the Northwest is low when compared to Europe, eastern North America, Tasmania and California, it is imperative to continue monitoring efforts for two reasons: 1) to elucidate the process of range expansion of a model non-indigenous marine species with planktonic larvae and 2) to serve as an early warning system for the next strong recruitment event of green crabs
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Status of the European Green Crab in Oregon and Washington Estuaries in 2013
Prepared for the Aquatic Nuisance Species Project, Pacific States Marine Fisheries Commission.Once a non-native species arrives and survives in an area, its long-term persistence depends on its recruitment success. If conditions are not favorable for recruitment it will ultimately disappear. The European green crab (Carcinus maenas) has a six-year life span and has persisted at low densities in Oregon and Washington coastal estuaries for the past 16 years. After the arrival of the strong founding year class of 1998, significant self-recruitment to the Oregon and Washington populations occurred only in 2003, 2005, 2006 and 2010. Warm winter water temperatures, high Pacific Decadal Oscillation and Multivariate ENSO (El Niño Southern Oscillation) Indices, late spring transitions and weak southward shelf currents in March and April are all correlated with the these strong year classes (Behrens Yamada and Kosro 2010). Cold winter water temperatures, low Pacific Decadal Oscillation Indices, early spring transitions and strong southward (and offshore) currents in March and April are linked to year class failure. Right now, green crabs are still too rare to exert a measurable effect on the native benthic community and on shellfish culture in Oregon and Washington. However, this could change if ocean conditions were to switch to a high PDO and strong El Niño patterns. For example, green crabs were first documented in New England in 1817, but it took warm ocean conditions during the 1950’s for their numbers to build to a level at which they decimated the soft-shelled clam industry.
Extensive surveys by Fisheries and Oceans Canada found green crabs in all the major inlets on the west coast of Vancouver Island and the Central Coast around Bella Bella, but so far none have been discovered in the inland sea between Vancouver Island and the mainland. Therefore, outreach efforts should continue to prevent the establishment of this invader in these inland waters via ballast water, shellfish transport or other human-mediated vectors.
Even though green crab abundance in Oregon and Washington is still low when compared to Europe, eastern North America, Tasmania, California and the west coast of Vancouver Island, it is imperative to continue monitoring efforts for two reasons:
1) to elucidate the process of range expansion and population persistence of this model non-indigenous marine species with planktonic larvae and
2) to predict the arrival of strong year classes from ocean conditions and alert managers and shellfish growers of possible increases in predation pressure from this invader
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Status of the European Green Crab in Oregon and Washington Estuaries Final Report November 2006
Prepared for Aquatic Nuisance Species Project, Pacific States Marine Fisheries Commission.Following the last El Niño of 1997-98, a strong cohort of young green crabs appeared in estuaries along the coasts of Oregon, Washington, and on the west coast of Vancouver Island, British Columbia. Unusually strong northward-moving coastal currents (up to 50 km/day from September 1997 to April 1998) must have transported green crab larvae from more established source populations in California to the Northwest. Coastal transport events have been much weaker in recent years.
It was hoped that green crabs would go extinct in the Pacific Northwest once the original colonists reached the end of their life span of 6 years and no new larvae arrived from California. From 2002 to 2004 green crab catches in Oregon and Washington were only around 7 crabs per 100 traps. However, this population size appears to be large enough to keep the population from going extinct. Local recruitment has occurred in Oregon and Washington estuaries and inlets on the west coast of Vancouver Island. Good recruitment in 2003, 2005 and 2006 is linked to warm winters and shore-ward transport in late winter/early spring when larvae are believed to be settling out from the plankton. The 2005 and 2006 year-classes are now the dominant cohorts in the Pacific Northwest, thus assuring a larval source until 2012 when the last of these crabs will die of old age. Even though green crab abundance in the Pacific Northwest is still low when compared to Europe, eastern North America, Tasmania and California, it is imperative to continue monitoring efforts for two reasons:
1) to elucidate the process of range expansion and population persistence of this model non-indigenous marine species with planktonic larvae and
2) to understand the role of ocean conditions on recruitment strength in order to predict the next strong recruitment event of green crabs.
Outreach efforts to educate the general public, including boaters and shellfish growers, not to transport non-native Aquatic Nuisance Species (ANS) from one area to another should continue. Such efforts could delay the spread and establishment of the green crab in the inland sea between Vancouver Island and the mainland, including Puget Sound and Hood Canal
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Status of the European Green Crab in Oregon and Washington Estuaries in 2008
Prepared for the Aquatic Nuisance Species Project, Pacific States Marine Fisheries Commission.A strong cohort of young European green crabs (Carcinus maenas) appeared in North American embayments from Oregon to the west coast of Vancouver Island following the strong El Niño of 1997/1998. Unusually strong north-moving coastal currents transported crab larvae from established source populations in California to the Pacific Northwest. Both coastal transport and recruitment of young green crabs have been weaker since. Although it was predicted that green crabs would become extinct in the Pacific Northwest once the original colonists died of senescence at about age six, this has not happened. Age-class analysis and the appearance of young crabs evidence the existence of local recruitment in the Pacific Northwest. Good recruitment in 2003, 2005 and 2006 is linked to warm winters and shore-ward transport in late winter and early spring when larvae are believed to be settling out from the plankton. Recruitment in 2007 and 2008 was poor in Oregon and Washington, but the strong 2005 and 2006 cohorts assure a larval source until 2012 when the last of these crabs will die of old age.
An extensive survey by Fisheries and Oceans Canada found green crabs in all the major inlets on the west coast of Vancouver Island, but none in the inland sea between Vancouver Island and the mainland nor north of Vancouver Island. Therefore, outreach efforts should continue to help prevent the establishment of this invader in the inland waters via ballast water or shellfish transport.
Even though green crab abundance in the Pacific Northwest is still low when compared to Europe, eastern North America, Tasmania and California, it is imperative to continue monitoring efforts for two reasons:
1) to elucidate the process of range expansion and population persistence of this model non-indigenous marine species with planktonic larvae and
2) to understand the role of ocean conditions on recruitment strength in order to predict the next strong recruitment event of green crabs
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Status of the European Green Crab in Oregon and Washington Estuaries in 2010
Prepared for the Aquatic Nuisance Species Project, Pacific States Marine Fisheries Commission.Once a non-native species arrives and survives in an area, its long-term persistence depends on its recruitment success. If conditions are not favorable for recruitment it will ultimately disappear. The European green crab (Carcinus maenas) has a six-year life span and has persisted at low densities in Oregon and Washington coastal estuaries for the past 13 years. After the arrival of the strong founding year class of 1998, significant self-recruitment to the Oregon and Washington populations occurred only in 2003, 2005 and 2006. Warm winter water temperatures, high Pacific Decadal Oscillation and Multivariate ENSO (El Niño Southern Oscillation) Indices for March, late spring transitions and weak southward shelf currents in March and April are all correlated with the these strong year classes (Behrens Yamada and Kosro 2010). Cold winter water temperatures, low Pacific Decadal Oscillation Indices, early spring transitions and strong southward (and offshore) currents in March and April are linked to year class failure. Right now, green crabs are still too rare to exert a measurable effect on the native benthic community and on shellfish culture in Oregon and Washington. However, this could change if ocean conditions were to switch to a high PDO and strong El Niño patterns. For example, green crabs were first documented in New England in 1817, but it took over 100 years for their numbers to build up to a level to decimate the soft-shelled clam industry during the 1950’s when warm ocean conditions prevailed.
Extensive surveys by Fisheries and Oceans Canada found green crabs in all the major inlets on the west coast of Vancouver Island, but so far none have been discovered in the inland sea between Vancouver Island and the mainland nor north of Vancouver Island. Therefore, outreach efforts should continue to help prevent the establishment of this invader in the inland waters via ballast water, shellfish transport or other human-mediated vectors.
Even though green crab abundance in the Pacific Northwest is still low when compared to Europe, eastern North America, Tasmania and California, it is imperative to continue monitoring efforts for two reasons:
1) to elucidate the process of range expansion and population persistence of this model non-indigenous marine species with planktonic larvae and 2) to predict the arrival of strong year classes from ocean conditions and alert managers and shellfish growers of possible increases in predation pressure from this invader
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Status of the European Green Crab in Oregon and Washington Estuaries in 2009
Prepared for the Aquatic Nuisance Species Project, Pacific States Marine Fisheries Commission.A strong cohort of young European green crabs (Carcinus maenas) appeared in North American embayments from Oregon to the west coast of Vancouver Island following the strong El Niño of 1997/1998. Unusually strong north-moving coastal currents transported crab larvae from established source populations in California to the Pacific Northwest. Both coastal transport and recruitment of young green crabs have been weaker since. Although it was predicted that green crabs would become extinct in the Pacific Northwest once the original colonists died of senescence at about age six, this has not happened. Age-class analysis and the appearance of young crabs evidence the existence of local recruitment in the Pacific Northwest. Good recruitment in 2003, 2005 and 2006 is linked to warm winters and shore-ward transport in late winter and early spring when larvae are believed to be settling out from the plankton. Recruitment in 2007, 2008 and 2009 has been poor in Oregon and Washington, but the strong 2005 and 2006 cohorts assure a larval source until 2012 when the last of these crabs will die of old age.
Extensive surveys by Fisheries and Oceans Canada found green crabs in all the major inlets on the west coast of Vancouver Island, but none in the inland sea between Vancouver Island and the mainland nor north of Vancouver Island. Therefore, outreach efforts should continue to help prevent the establishment of this invader in the inland waters via ballast water or shellfish transport.
Even though green crab abundance in the Pacific Northwest is still low when compared to Europe, eastern North America, Tasmania and California, it is imperative to continue monitoring efforts for two reasons:
1) to elucidate the process of range expansion and population persistence of this model non-indigenous marine species with planktonic larvae and
2) to understand the role of ocean conditions on recruitment strength in order to predict the next strong recruitment event of green crabs