Cormorant Overpopulation - Ontario Federation of Anglers and

Cormorant Overpopulation
Prove Fish & Wildlife Conservation
Requires Management
Dr. Terry Quinney
Provincial Manager, Fish and Wildlife Services Department
Ontario Federation of Anglers and Hunters
OVERVIEW




Overpopulation concerns
Double-Crested Cormorant – History,
Distribution
Impacts – Ecological, Social, Economical
Management – Addressing DCC Impacts
CONCERN

Overpopulation and range expansion of
Double-crested Cormorants has had significant
impacts on fisheries, habitats, other species,
and human socio-economics

When not managed, cormorants threaten
ecosystem stability and natural biodiversity
Double-crested Cormorant
(Phalacrocorax auritus)



Photo Credit: Jill Roedding
Fish eating migratory bird
Colonize all of the Great Lakes
Rapid range expansion and
population growth in the last 2
decades
– Expansion includes many
inland lakes/large
waterbodies adjacent to the
Great Lakes
Great Lakes Cormorant Nests*
Superior
Huron
Erie
Ontario
St. Lawrence
20,000
10,000
20
03
20
01
19
99
19
97
19
95
19
93
19
91
19
89
19
87
19
85
19
83
19
81
0
19
79
Number of nests
30,000
•Superior and Huron data are Canadian colonies only; 03 & 04 Lk Ontario/SLR only
Courtesy of NYSDEC
30000
25000
Lake Ontario Cormorant Nests
14000
12000
Eastern Basin
L. Galloo Is.
Total
20000
10000
Central Basin
8000
15000
6000
10000
4000
5000
19
79
19
80
19
81
19
82
19
83
19
84
19
85
19
86
19
87
19
88
19
89
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
0
2000
0
Courtesy of NYSDEC
Overpopulation Impacts

Habitat
- Habitat loss number one threat to biodiversity
(Canadian Biodiversity Strategy, Ontario Biodiversity Strategy)
–

Fisheries
–


vegetation mortality (degradation of ecosystems)
sport and commercial fisheries
Impact other species (colonial nesters, fish species &
Species at Risk)
Impact on humans (socio-economic)
Impacts
Habitat
 Significant negative impacts on island habitats where
cormorants nest
–
–
–
Physical (i.e. breaking branches, stripping foliage, loss of
canopy cover, tree mortality)
Chemical (i.e. large quantities of guano change soil chemistry,
affect photosynthesis and plant respiration)
Degradation of ecosystems (i.e. Carolinian ecosystem on
Middle Island, Lake Erie which includes a number of species at
risk)
Impacts
Habitat – other species



Loss of potential nesting and roosting
habitat for other colonial birds
Direct competition for existing nest
sites
Displace other colonial nesters (i.e.
Great Blue Heron, Great Egret, Blackcrowned Night-Heron)
Management Strategy for Double-crested Cormorants at Presqu'ile Provincial Park, 2004
Photo Credit: Jill Roedding
Photo Credit: Jill Roedding
Impacts
Fisheries
 Overpopulation of cormorants
can negatively impact fish
abundance and production
–
–
–
Consume 20 - 25% of their body
weight (~ 1lb of fish/day)
Increased foraging pressure on
local fish population
Nutrient run-off into surrounding
water
NYSDEC
1998 Percent Cormorant Diet by Number, Little Galloo Island
1.5%
Alewife
Yellow Perch
Smallmouth
Other
Courtesy of NYSDEC
Frequency of occurrence of prey fish consumed by double-crested cormorants,
Little Galloo Island, eastern Lake Ontario, 1999-2003 (J. Johnson, pers. comm.
2004). Mean weight by species = 108.1 g and by individual = 39.8 g. Per cent by
number and weight: sports species = 3.8% and 26.4%, commercial species =
40.4% and 46.9%, and prey fish species = 49.1% and 26.4%.
Number
Weight
Name
Body
weight
Rank
%
Rank
%
Alewife
Yellow perch
Cyprinids
Pumpkinseed
Three-spine stickleback
Rock bass
Smallmouth bass
Slimy sculpin
Trout-perch
Brown bullhead
Other sport fish
Others (goby, etc.)
26.4
37.3
10.6
53.6
1.5
49.3
260.1
3.3
6.0
250.0
577.1
20.8
1
2
3
4
5
6
7
8
9
10
11
12
35.0
25.6
9.8
8.7
6.6
6.0
3.6
2.7
1.6
0.6
0.2
0.1
3
1
8
4
10
5
2
11
9
6
7
12
23.2
24.0
2.6
11.7
0.2
7.4
23.5
0.2
0.3
3.8
2.9
0.1
Courtesy of NYSDEC
Smallmouth Bass Population Dynamics
4.5
Relative mortality
(CPUE age-3 / CPUE age-6)
4
2
r = 0.9101
3.5
3
2.5
2
1.5
2
r = 0.0385
1
0.5
0
0
1000
2000
3000
4000
5000
6000
7000
Cormorant nests (3 year average)
NYS Fish Wildlife & Marine Resources
Impacts
Fisheries

Declines in smallmouth bass
and yellow perch abundance
in the eastern basin of Lake
Ontario have been associated
with cormorant population
increases
(NYSDEC Lake Ontario Annual Report 2008)
Credit: DNR Cornell
Impacts
Socio-Economical




Economic losses to fisheries, and fishingrelated businesses
– Millions of anglers participate in
recreational fishing Ontairo
– Contribute billions of dollars to Ontario’s
economy annually ($2.5 billion 2005)
Losses to private resources (private lakes and
damaged trees)
Water quality – nutrient run
Damage to private property
–
Private landowners have specific rights under the
Fish and Wildlife Conservation Act to deal with
cormorants causing property damage
ON Legislation & Policy


Not included under the federal Migratory Birds
Convention Act, and thus are not protected by
federal law
Protected under Ontario’s Fish and Wildlife
Conservation Act 1997 (FWCA)
–
–
prohibits the hunting and trapping of cormorants;
prohibits the destruction, taking and/or possession
of nests or eggs without authorization from the
Minister of Natural Resources.
Management Required
Addressing Impacts of Double-Crested Cormorants

O.F.A.H. recommends having the cormorant added to
the list of provincially unprotected birds
–
Private Members Bill 156 introduced will remove the
protection that cormorants currently enjoy, treat these birds
the same as common crows and grackles and allow for culling
of the birds in addition to other population control methods
currently being used
Methods of Control



Culling – most rapid means of reducing adult breeding
birds from the population
Egg oiling – Ground nests reduces population growth –
impractical for tree nests
Mechanical nest destruction – enhances predation and
abandonment – requires more than one visit per colony
(time consuming)
Canadian Wildlife Servic
Acknowledgements
Fisheries information and data courtesy of Steve LaPan,
New York State Department of Environmental Conservation
NYSDEC Lake Ontario Annual Report 2008
NYSDEC Lake Ontario Annual Report 2007
Review of the Status and Management of Double-crested
Cormorants in Ontario 2006