Nav: Home

Seals, birds and humans compete for fish in the Baltic Sea

November 13, 2017

In Sweden and in other parts of Europe there are concerns that seals and birds compete with humans for fish resources. For the Baltic Sea, an international study now shows that this competition is a reality.

"Because fish is nutrient-rich food and angling provides valuable recreation, the increased populations of seals and fish-eating birds in the Baltic have resulted in a sometimes contentious debate over the effects of these animals on the fish stocks. The debates are often based on assumptions, which is why I took the initiative to look at the problem from a scientific viewpoint," said Sture Hansson, Professor of Ecology, Environment and Plant Sciences at Stockholm University.

Together with four researchers from the Swedish University of Agricultural Sciences (SLU) and seven other colleagues from countries around the Baltic, Hansson has estimated birds' and seals' fish consumption. Seals are the primary fish-eating mammals, and their consumption is about the same as that of all birds together. Humans catch 3 to 4 times more fish than seals and birds combined.

Small-scale coastal fishing most impacted by wildlife

The fishing grounds most impacted by competition from wildlife are the coastal areas with species like perch, pike, pikeperch, brown trout, salmon, whitefish and vendace. Seals and cormorants consume similar amounts as humans. Because we know that these fish are impacted by human fishing activities, it's reasonable to conclude that they are also impacted by predation from seals and birds. Wildlife thus competes with humans for these fish resources.

For some unknown reason, there has been such a dramatic reduction in eel that they are now considered critically endangered. Eel fishing has been drastically reduced and complete bans are being discussed. In this case as well, it is worth noting that the eel consumption by cormorants is at the same level as human fishing.

Based on these results, the scientists conclude that the impacts of seals and birds (primarily cormorants) on fish stocks should be considered in future management plans. Both reductions in fishing quotas and wildlife predation rates should be considered when fish stocks decrease so precipitously. This might take the shape of hunting or harassments to reduce animal abundances.

Seals and birds had no major impact on open sea fisheries for herring, sprat and cod.
-end-
The article is published in ICES Journal of Marine Science, https://academic.oup.com/icesjms/advance-articles

Contacts:

Sture Hansson, Stockholm Univ., +46708-140599, sture.hansson@su.se

Ulf Bergström, SLU, +4610-478 4117, ulf.bergstrom@slu.se

Facts and figures:


Fishery catch: 700,000 tons/yr, of which 650,000 tons are herring, sprat and cod

Consumption by seals: 100,000 tons/yr, of which 60,000 tons are herring, sprat and cod. Grey seal 75,000 tons, ringed seal 20,000 tons and harbour seals 5,000 tons

Consumption by birds: 100,000 tons/yr, of which 30,000 tons are herring, sprat and cod. Cormorants consume 40,000 tons/yr, while razorbill, common guillemot, common and red-breasted merganser each consume about 10,000 tons/yr. The remaining 20,000 tons are consumed by other bird species.

Stockholm University

Related Birds Articles:

Birds become immune to influenza
An influenza infection in birds gives a good protection against other subtypes of the virus, like a natural vaccination, according to a new study.
Even non-migratory birds use a magnetic compass
Not only migratory birds use a built-in magnetic compass to navigate correctly.
When birds of a feather poop together
Algal blooms deplete oxygen in lakes, produce toxins, and end up killing aquatic life in the lake.
Birds of a feather mob together
Dive bombing a much larger bird isn't just a courageous act by often smaller bird species to keep predators at bay.
Monitoring birds by drone
Forget delivering packages or taking aerial photographs -- drones can even count small birds!
The color of birds
New research provides insight into plumage evolution.
Migrating birds speed up in spring
It turns out being the early bird really does have its advantages.
Birds on top of the world, with nowhere to go
Climate change could make much of the Arctic unsuitable for millions of migratory birds that travel north to breed each year, according to a new international study published today in Global Change Biology.
City birds again prove to be angrier than rural birds
The researchers' observations shed light on the effects of human population expansion on wildlife.
Teaching drones about the birds and the bees
Unmanned Aerial Vehicles (UAVs) of the future will be able to visually coordinate their flight and navigation just like birds and flying insects do, without needing human input, radar or even GPS satellite navigation.

Related Birds Reading:

The Genius of Birds
by Jennifer Ackerman (Author)

National Geographic Backyard Guide to the Birds of North America (National Geographic Backyard Guides)
by Jonathan Alderfer (Author), Paul Hess (Author)

National Audubon Society Field Guide to North American Birds: Eastern Region, Revised Edition
by National Audubon Society (Editor)

National Geographic Field Guide to the Birds of North America, 7th Edition
by Jon L. Dunn (Author), Jonathan Alderfer (Author)

Backyard Birds (Field Guides for Young Naturalists)
by Karen Stray Nolting (Author), Jonathan Latimer (Author), Roger Tory Peterson (Illustrator)

Birds of the Photo Ark
by Noah Strycker (Author), Joel Sartore (Photographer)

Birds: A Fully Illustrated, Authoritative and Easy-to-Use Guide (A Golden Guide from St. Martin's Press)
by Herbert S. Zim (Author), Ira N. Gabrielson (Author), Chandler S. Robbins (Editor), James Gordon Irving (Editor)

Bird Bingo
by Christine Berrie (Illustrator)

Sibley Backyard Birding Flashcards: 100 Common Birds of Eastern and Western North America (Sibley Birds)
by David Allen Sibley (Author)

National Geographic Little Kids First Big Book of Birds (National Geographic Little Kids First Big Books)
by Catherine D. Hughes (Author)

Best Science Podcasts 2018

We have hand picked the best science podcasts for 2018. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Why We Hate
From bullying to hate crimes, cruelty is all around us. So what makes us hate? And is it learned or innate? This hour, TED speakers explore the causes and consequences of hate — and how we can fight it. Guests include reformed white nationalist Christian Picciolini, CNN commentator Sally Kohn, podcast host Dylan Marron, and writer Anand Giridharadas.
Now Playing: Science for the People

#482 Body Builders
This week we explore how science and technology can help us walk when we've lost our legs, see when we've gone blind, explore unfriendly environments, and maybe even make our bodies better, stronger, and faster than ever before. We speak to Adam Piore, author of the book "The Body Builders: Inside the Science of the Engineered Human", about the increasingly amazing ways bioengineering is being used to reverse engineer, rebuild, and augment human beings. And we speak with Ken Thomas, spacesuit engineer and author of the book "The Journey to Moonwalking: The People That Enabled Footprints on the Moon" about...