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The conflict between cormorants and fisheries

FACTS AND MANAGEMENT

NIELS JEPSEN DTU AQUA, SILKEBORG

Merimetso - Helsinki 2016

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Main questions:

1. Overview of the development of the cormorant conflict in Denmark

2. How the cormorants have moved from the coast to freshwater, could this happen in Finland?

3. The Danish cormorant management plan and our experience with it

4. How we apply article 9 of the birds directive; especially how we interpret "to prevent serious damage"

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Status:

• We have documented severe damage from cormorants on

• several fish populations and fishery as well as economy

• After 15 years of increasingly tough (lethal) management we still have many conflicts

• Cormorants may very well start to move inland in Finland.

• If they do you must be ready to respond

• We cannot solve the problem alone, we need Nordic cooperation

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Population status - brief

Predation studies, coast, lakes, rivers – what have we learned?

Management – MP and the long lasting conflict

Questions and discussion

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East Sand Island in Columbia River 2015

26,000 nests to be destroyed, 11,000 birds to be shot

Cormorants are eating nearly 20 million baby salmon a year on

East Sand Island, a tiny man-made Oregon island. (Jamie Francis/The Oregonian )

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Conflict: Conservation of a healthy cormorant population and conservation of harvestable fish stocks

Fish enough for predators and anglers

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Colonies 2014

Current max number of birds: 250.000

Current min number of birds: 15.000

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Development in breeding stock (pairs) in Denmark 1973-2015

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Who has the problems?

• Pound-net fishers

• Recreational net fishers

• Anglers

• Biodiversity?

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The story - brief

• 80’ies – 90’ies – Traditional pound net fishing disappeared

• Then coastal fish (and fishing) was heavily reduced

• Relatively few, large colonies

• Heavy predation on sea-trout and salmon smolts

• Large colonies started to collapse (2002-2008)

• More, but smaller colonies

• More birds overwintering (mostly from Sweden and Finland)

• 2009/10 change of behaviour, birds going inland, less shy

• Recent years – much more problems in rivers, brooks and lakes

• Grayling, resident trout and North Sea Houting are threatened

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Coast:

Eelpout (kivinilka) disappeared, very few left Documented impact on flounders (kampela) Documented impact on eel (ankerias)

Documented high impact on salmon (lohi)

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Skjern River North Sea

Sluices

Surface area: 300 km 2 Depth: 0 - 10 m

+2000 nests

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0 200 400 600 800 1000 1200 1400

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Commercial catch

0 500 1000 1500 2000 2500 3000

Number of nests

Flounder (1000kg) Eel (100 kg)

Cormorants

Number of nests in colony, catches of flounder and eel

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10,000 eel were cw-tagged and released in 2003

and 64.000 CW tagged 1-year salmon were released in Skjern River

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4,000 flounders (7 – 20 cm) were caught and cw-tagged in 2004

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Pellet collection

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Recovery of cw tags from salmon smolts from cormorant pellets collected April through June 2003

Predation of salmon smolts 2003

0 100 200 300 400 500 600

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43

Days after first collection

Estimated number of smolts

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Otolith analyses from pellets

115

38 33 2 2

0 200 400 600 800 1000 1200 1400 1600

x 1000

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Results from Ringkøbing Fjord 2000 – 2004

Telemetry (2000, 2002): Salmon smolts 40 – 50 % of tags were recovered from one colony.

CW-tagging (2003, 2004): 25 % of the available tagged salmon smolts were eaten during the 3-weeks smolt migration period.

40 – 50 % of tagged eel were eaten in one year.

All (100%) of tagged flounders eaten in 15 days

Pellet analyses: 30,000 salmon smolts, 1.4 million flounders, 38,000 eel were eaten.

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Mink Otter

Cormorant Grebe Heron

Estimated fish-consumption (Total 12595 t)

Freshwater

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The current predation pressure from Great Cormorants on river fish populations is judged as being generally high. In particular

Grayling, Salmon and larger

(resident) Brown Trout are being predated upon during winter at apparently unsustainable levels in some rivers. Some populations of Grayling are presently very close to local extinction. Results have also demonstrated high predation pressure from Great Cormorants on lake fish populations, in particular Trout and Perch.

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Cormorants in our streams – a new phenomenon

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Foto: Allan Guido Nielsen

Foto: Michael Holm

Two cold winters 2009-10

2010-11

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Grayling – Omme Å Number pr. km

2009 2010

Fry 147 0

1+ 250 5

Larger 15 1

Total 412 6

Catch of Grayling by electrofishing a 2 km stretch in Omme Å 2009 og 2010 (Iversen 2010).

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Grayling (harjus)

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Grayling

Grayling density in 1,5 km stream. Cormorants were first seen in 2007, but in larger numbers after 09/10.

0 500 1000 1500 2000 2500

1987 1988 1990 1991 1999 2004 2011 2012 2013

Antal pr. km

Større Yngel

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In an ongoing study, 25 grayling (32-36 cm) were radiotagged in October.

No loss until a cold week in late January, where birds showed up and 8 of the tagged fish were taken.

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Trout

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Trout

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Salmon spawning-run - River Skjern Effect of in-river predation?

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Predation on lake fish

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Loldrup Sø Viborg søerne

2005 2007 2008 2009 2008 2009

Roach (särki) 19% 32% 17% 30% 24%

Bream (lahna) 11% 33% 33%

Perch (ahven) 41% 46% 70% 45%

Pike (hauki) 33% 30%

Minimum estimates (Skov et al. 2014)

PIT studies of lake fish

More than 1000 PIT tags were found in one colony 13-20 km away

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Perch

Large perch (>25 cm) are more vulnerable (> 40%)

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Pike

Large pike (> 30 cm) are more vulnerable (50%)

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Other studies:

• Impact of cormorants on flounder population in Kattegat

• Ecologic modelling for the Limfjord (Eco-path)

• Hald Sø lake trout (20 – 50 % of smolts eaten)

• Sea-trout smolt in Funen (massive loss)

• Trout and salmon smolts in Randers Fjord (no big impact)

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Conclusion:

Significant impact on fish populations in Rivers, Lakes and coast Documentation (by many methods) that predation from cormorants is the main regulating factor for many fish stocks.

Effects include:

• Economic loss (commercial and recreational fishing)

• Cultural loss

• Biodiversity loss

• Problems in reaching WFD requirements

For Art. 9, we have enough documentation to apply derogations

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Management

Ministry of Environment

Cormorant-group: Stakeholders, managers, experts

National cormorant management-plan since 1997:

• Egg oiling

• Prevention of new settlements

• Protective Shooting (fishers and hunters)

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The cormorant group meets regularly and consists of:

Ministry of the environment (Naturstyrelsen) Anglers (DSF)

Commercial fishers

Recreative net fishers (Fritidsfiskere)

Animal protection (Dyrenes Beskyttelse) Hunters (DJF)

Ornithologists (DOF)

Minstry of agriculture and fisheries Bird expert (T. Bregnballe, ÅU) Fish expert (N. Jepsen, DTU)

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Adaptive management

• MP provides the framework

• Loss in poundnets – fishermen were permitted to shoot cormorants at nets (1000 m)

• Loss of smolts – anglers were permitted to shoot cormorants during smolt migration

• Cormorants foraging in the rivers – protective shooting was initiated

• Now it will also be possible to shoot at night roosting sites

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Permissions granted to regulate (shoot) in rivers

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Oiling off eggs

Fotos: Jan Skriver

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Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management

AARHUS UNIVERSITY, National Environmental Research Institute

xx

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0 10.000 20.000 30.000 40.000

1971 1975 1979 1983 1987 1991 1995 1999 2003 2007 2011

Number of nests

Oiled nests

Total nests

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Course in Wildlife Ecology and Management, spring 2011, Block 5: Cormorants: Population ecology, modelling and management

AARHUS UNIVERSITY, National Environmental Research Institute

Ringkøbing

Fjord

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Sprayed Not sprayed

Nest numbers 2001-2011 in a regulated colony - Ringkøbing

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Cold winters and lack of food

Management measures seems NOT to be the main cause of the recent decrease of Cormorant numbers in DK.

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Human - Wildlife Conflicts in Europe

Fisheries and Fish-eating Vertebrates as a Model Case Series: Environmental Science and Engineering

Klenke, R.A.; Ring, I.; Kranz, A.; Jepsen, N.; Rauschmayer, F.;

Henle, K. (Eds.). 1st Edition., 2013, 50 illus.

Dieperink, C., Pedersen, S. & Pedersen, M.I. (2001). Estuarine predation on

radiotagged wild and domesticated sea trout (Salmo trutta L.) smolts. Ecology of Freshwater Fish 10, 177–183.

Dieperink, C., Bak, B.D., Pedersen, L., Pedersen, S. & Pedersen, M.I. (2002).

Predation on Atlantic salmon and sea trout during their first days as postsmolts.

Journal of Fish Biology 61, 848–852.

Koed, A., Baktoft, H. & Bak, B. D. (2006). Causes of mortality of Atlantic salmon (Salmo salar) and sea trout (Salmo trutta) smolts in a restored river and its estuary.

River Research and Applications 22, 69–78.

Jepsen, N, Sonnesen, P., Klenke, R. & Bregnballe, T. (2010). The use of coded wire tags to estimate cormorant predation on fish stocks in an estuary. Marine and

freshwater Biology 61, 320-329.

Skov, C., Jepsen, N., Baktoft, H., Jansen, T., Pedersen, S. & Koed, A. (2014).

Cormorant predation on PIT-tagged lake fish. Journal of Limnology (in press).

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No conservation issue No recreational value No commercial value Feelings

Conservation Biodiversity

Recreational value Commercial value Cultural history Feelings

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Thank you

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The North Sea houting

Monitored by e-fishing and gill netting – PIT tagging

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LIFE project (2006 – 2012):

Budget of 13.4 million Euros

Two hydroelectric power plants and 11 other weirs (fish farms) have been removed, giving 120 km of lost river habitats to the NSH

Channelized river sections have been re-engineered (21 km)

Establishment of 470 ha of new nursery area

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Status 20014

• Ribe Å: The population has been followed (PIT tagging) for many years. Since 2011 very few individuals have been seen

• Varde Å: Same situation as Ribe. In 2012, we could not catch one fish in the whole system

• Vidå: Still holds a decent population, but much smaller than in 2011.

Where’s the problem???

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