Presentation on theme: "Ken Dahler, Taylor Ferreira and Ryan Glew (Team 11)"— Presentation transcript:
Ken Dahler, Taylor Ferreira and Ryan Glew (Team 11)
Problem Statement A growing Double-crested Cormorant population is affecting sport fish populations as well as destroying island nesting habitat in Lake Champlain.
Goals Evaluate why cormorant populations have begun to grow so rapidly in the Lake Champlain basin. Investigate how the increasing cormorant population is effecting the local fish populations Look at what effects cormorants impose on island nesting sites.
Objectives To assess the ecological risks associated with increasing Cormorant populations, with focus on habitat destruction and alteration, fish consumption, and competition among piscivorous birds. To identify factors that influenced the drastic increase of cormorants in the Lake Champlain basin. To identify if and how Cormorants destroy habitat and how that affects other island nesting species. Determine how cormorants impact sport fishing in Lake Champlain, and how they affect fish populations. Review case studies and current legislation on management techniques to develop a management plan on how mitigate the negative effects of this species.
Double-crested Cormorant One of 40 species of Cormorants Inhabits rivers, lakes and costal areas in North America. Can weigh between 2.6 to 5.5 lbs. Body length between in. Wingspan of between in. (Hatch and Weseloh 1999)
Feeding Behavior Surface divers, they forage underwater for fish. Fully-webbed feet propel their slim bodies on dives up to 60 feet deep. Chases prey underwater, grabbing them in their bill. (USFWS, 2009) (Hatch and Weseloh 1999)
Cormorant fishing on the Nagara River, Japan
Nuisance Species Aquaculture Perch on boats and docks Destruction of private property Kill nesting trees (aesthetics) Non-charismatic species Predate game fish?
Historic Populations Archaeological records show skeletal remains of Double- Crested Cormorants from native American sites that date years old. Remains found throughout all of continental US and into Canada Records indicate higher populations before English settlement Late 1800s – early 1900s = big decrease Early 1900s – mid 1900s = increase 1960s and early 1970s = decrease Since 1970s = increase (Wires, Cuthbert 2005)
Range (Hatch and Weseloh 1999 )
Regional Population Growth Since 1970s: Great Lakes cormorant populations increased at annual rate of 29% (Weseloh et al. 2006) Coastal New England population increased at annual rate of 6% annually (Krohn et al 1995) Where is Lake Champlain located…?
Lake Champlain Population Growth 1970s: Cormorants = rare visitors 1981: First nest observed 1981 – late 1990s: population has shown annual increase of 21% (Duerr 2007)
Population Misconceptions Cormorant populations are higher now than ever Cormorant populations are expanding to “new” territories
Factors that Influenced Population Growth 1969: Canada bans the use of DDT 1972: US bans the use of DDT (Hatch and Weseloh 1999) 1972: Cormorant protected under Migratory Bird Treaty Act (Hatch 1984) Catfish farms help decrease overwinter mortality Fishermen overharvest large predatory fish in Lake Champlain…increase in smaller fish populations (Allan Strong)
Effects on Vegetation Cormorants are colonial nesting birds Remove sticks and leaves from trees and shrubs to use as nesting material Slows growth and increases mortality of vegetation Acidic guano that kills trees and ground shrubs (Sullivan et al. 2006)
Change in forest cover on Middle Island, Lake Erie, due to cormorant nesting between 1995 and Hebert et al ~1,000 nests ~4,000 nests
Effects on Other Bird Species When cormorants inhabit a new location, they will often nest with other colonial waterbirds (Allan Strong) Habitat destruction by nest construction and guano often displaced other native island- nesters (Duerr 2007) Early arrival to nesting sites can directly displace other birds looking to establish nests (Allan Strong)
Lake Champlain YOUNG ISLAND/ FOUR BROTHERS: – Snowy Egrets – Cattle Egrets – Black-crowned Night Herons – Ring Billed Gulls – Greater Black-backed Gulls MISSISQUOI NWR – Great Blue Herons BIXBY ISLAND – Black-crowned Night Herons POPASQUASH ISLAND – Common Terns* (Endangered) (Audobon Vermont 2010)
Effects on Fish WARNING: DISTURBING PICTURE ON NEXT SLIDE!!
Effects on Fish (Lake Champlain Fishing Forum) Cormorants are opportunistic foragers that consume the most abundant fish species available. (Allan Strong)
Effects on Fish : (Lake Oneida, NY) (Rudstam et al. 2004)
Effects on Fish: (Lake Champlain) Duerr (2007) conducted research from 2001 to 2002 examining the stomach contents of cormorants in Lake Champlain. Collected 154 cormorants for diet analysis From these samples, 2,255 fish of 21 species were identified. Most common prey items identified were Yellow Perch and Rainbow Smelt Yellow Perch being the most abundant prey item by mass (78%) These results suggest that cormorants may have a negative effect on the Lake Champlain Yellow Perch population, such that they did in Oneida Lake.
What are the effects on sport fishing? Should sport fishermen really be concerned? Cormorants do consume large quantities of yellow perch Do not commonly feed on the larger sport fish However...
Non-Lethal Methods of Control Harassment: Nest or Egg destruction Egg Oiling Monofiliment barriers
Harassment Pyrotechnic Devices Automatic Exploder Alarm or Distress calls Lights Water-Spray devices Human Effigies Harassment patrols Images from scaregun.com
Nest and/or Egg Destruction Form of Harassment Destroying nests and/or eggs is a viable option in harassing birds to relocate a new nest If done too early in the breeding season, birds have opportunity to build new nest, and lay a 2 nd clutch (not useful)
Egg Oiling Kills embryos before they have opportunity to develop. What does putting oil on an egg do? With What? Why is this method so effective? Egg Flotation Test
Egg oiling is very effective Table from Johnson et. Al 2000
Monofilament barriers Have a variety of applications from aquaculture to agriculture Can be as simple as 1-5 lines being stretched over a small field, pond or island and tied off. Can also be a complex grid system with 6-12” grid squares. Makes travel difficult for large birds
Wire Barrier Systems The Picture to the left and bottom are from Popasquash Island, and shows the wire barrier system in place there to reduce the number of cormorants from landing and nesting there. Established to protect the Common Tern. Images from Beckett 2008
Monofilament Barriers Popasquash Island: has an experimental monofilament barrier established with lines tied between metal stakes and small shrubs Discourages and reduces the ability of Cormorants and Other large birds from landing. This method is proving to be affective against cormorants due to their size and poor agility, but is not as inhibiting for terns and other small agile birds.
Popasquash Island Is a very small island between Swanton and st. Albans VT It is home to one of the few breeding habitats for the endangered common tern Try to keep cormorants off of the island
Popasquash Island Grid System This Diagram Shows the approximate grid system created on Popasquash Island. The darker lines on the northern side of the island represent areas where enclosures were created for common terns to nest in. Image from Beckett 2008.
Lethal Management Options The last resort, populations have become to large, or destructive and a large number of individuals need be removed from the area. The right to use lethal control must be issued by the USFWS, after a representative from the service has come and completed a full site assessment and determined that non-lethal control is no longer effective. If lethal control is instituted, there are 2 acceptable methods The use of non-toxic lead free shot must be used Asphyxiation
Conclusions Populations have exploded over the past 30 years Populations may be lower than they historically were, but they are high compared to recent records (past 30 years) It appears they are re-colonizing old breeding grounds, rather than expanding to new territory Populations have boomed since DDT ban Science suggests cormorants are not detrimentally affecting bait or sport fish populations They do destroy island nesting sites, making them uninhabitable for other island nesters
Recommendations We recommend the use of non-lethal harassment techniques Egg Oiling Monofilament barriers Human Patrols at nesting sites The lake Champlain population is not large or destructive enough to warrant lethal management, but it could be an option in the future if populations continue to grow exponentially
Outlook for the Future More information needed on population size and nesting locations. Non-lethal options should be explored before lethal techniques are used. Issue of social versus biological carrying capacity should be addressed.
Summary: Problem Statement: A growing Double-crested Cormorant population is affecting sport fish populations as well as destroying island nesting habitat in Lake Champlain. Goals: Evaluate why cormorant populations have begun to grow so rapidly in the Lake Champlain basin. Investigate how the increasing cormorant population is effecting the local fish populations. Look at what effects cormorants impose on island nesting sites. Conclusion: Increasing cormorant populations are affecting small island nesting sites, and possibly diminishing sport fish populations.
Audubon Vermont. (2010). Lake Champlain Colonial Waterbird Database. from Accessed 23 March Beckett, Sean Assessing Endangered Lake Champlain Common Tern Predator Deterrent Systems via Video Surveillance. VINS Environmental Science Research Fellowship. Pp August Duerr, A.E. (2007). Population Dynamics, Foraging Ecology, and Optimal Management of Double-crested Cormorants on Lake Champlain. Dissertation to the Faculty of the Graduate College of the University of Vermont. May, Green Mountain Audubon center: 255 Sherman Hollow Road. Huntington, VT (802) Hatch, J.J. (1984). Rapid Increase of Double-crested Cormorants Nesting in Southern New England. American Birds38: Hatch, J. J., and D. V. Weseloh. (1999). Double-crested cormorant (Phalacrocorax auritus). Account 441 InA. Poole and F. Gill, editors. The Birds of North America, The Academy of Natural Sciences, Philadelphia, Pennsylvania, and The American Ornithologists’ Union, Washington, D.C. USA. Hebert, Craig E., Jason Duffe, Chip Weseloh, and Ted Senese. "Unique Island Habitats May Be Threatened by Double-Crested Cormorants." The Journal of Wildlife Management 69.1 (2005): Web. Johnson, J.H., Ross, R.M., Farquhar,J. March 1, The effects of Egg oiling on Fish Consumption by Double-Crested Cormorants on Little Galloo Island, Lake Ontario. New York State Department of Environmental Conservation, Watertown, NY Krohn W. B., R. B. Allen, J. R. Moring and Hutchinson A. E. (1995). Double-Crested Cormorants in New England: Population and Management Histories. Colonial Waterbirds, 18(Special Publication 1): Rudstam, L.G., VanDeValk, A.J., Adams, C.M., Coleman, J.T.H., Forney, J.L., Richmond, M.E., and (2004). Cormorant Predation and the Population Dynamics of Walleye and Yellow Perch in Oneida Lake. Ecological Applications.14(1), Strong, Allan. Personal interview. 24 Mar Sullivan, K. L., Curtis, P. D., Chipman, R. B. and McCullough, R. D. (2006). The Double-Crested Cormorant: Issues and Management. Retrieved from Cornell University Cooperative Extension. Department of Natural Resources, Cornell University, Ithaca, New York. United States Department of Agriculture, Bird Predation and Its Control at Aquaculture Facilities in the Northeastern United States, Animal and Plant Health Inspection Service, APHIS Issued June 1997 Wires, L.R., F.J. Cuthbert, D.R. Trexel and A.R. Joshi. (2001). Status of the Double-crested Cormorant (Phalacrocorax auritus) in North America. Final Report to USFWS