Cormorants are water birds that are expert fishers, catching a wide variety of fish to eat. In this article, we’ll take a look at the diets of different cormorant species and the types of fish they prey on.
Quick Answer: Cormorants are Piscivorous Birds that Eat Mostly Small Fish
Cormorants are highly adaptable, opportunistic feeders that eat a wide variety of small fish, depending on availability and local conditions. The most common fish eaten by cormorants include:
- Anchovies
- Herring
- Minnows
- Sardines
- Sticklebacks
Cormorants plunge dive from the surface to catch fish underwater. They are pursuit predators that chase fast-moving fish like tuna. Cormorants also take advantage of fish congregating in large groups, making them easy picking.
Cormorant Species and Their Diets
There are about 40 different species of cormorants around the world. Here are some of the most common species and details about the fish they consume:
Great Cormorant
The Great Cormorant is found widely across Europe, Asia, Africa, Australia and New Zealand. They primarily feed on small fish like:
- Sand eels
- Sculpins
- Small perch
- Sticklebacks
Great Cormorants eat 1-2 pounds of fish per day on average.
Double-Crested Cormorant
Double-crested Cormorants live along the coasts of North America. They eat a diverse diet of fish including:
- Alewives
- Anchovies
- Catfish
- Mullet
- Perch
- Salmon
- Sardines
Double-crested Cormorants may fly up to 18 miles from their nesting site to find food.
Pied Cormorant
The Pied Cormorant inhabits the coastal regions of eastern and western Australia. Their diet consists mainly of:
- Bluespotted flathead
- Lizardfish
- Mullet
- Sole
- Toadfish
- Triggerfish
- Wirrah
Pied Cormorants dive to seabeds 33-130 feet deep in search of prey.
Neotropic Cormorant
The Neotropic Cormorant lives along the coasts of Central and South America. Their diet includes:
- Grunts
- Mullets
- Needlefish
- Snook
- Tilapia
Neotropic Cormorants sometimes follow fishing boats to scavenge on discarded fish.
Spotted-Breasted Cormorant
The Spotted-Breasted Cormorant makes its home in sub-Saharan Africa. It eats primarily:
- Cichlids
- Gobies
- Mormyrids
- Tilapia
Spotted-Breasted Cormorants breed during the rainy season when fish are more plentiful.
Habitats and Hunting Strategies
Cormorants inhabit a wide range of aquatic habitats across the world. The environments where they live influence the types of fish available as prey. Their hunting strategies also vary by species and habitat.
Coastal Areas
Many cormorants live along rocky shorelines and shallow coastal waters. There they prey on small fish that congregate near the coast like:
- Anchovies
- Herring
- Sand lance
- Silversides
Coastal cormorants plunge dive up to 100 feet to reach fish swimming in shallow waters near the seafloor.
Lakes and Rivers
Cormorants occupy freshwater lakes, rivers and estuaries. Common prey includes:
- Carp
- Catfish
- Minnows
- Perch
- Shad
- Trout
River cormorants snatch fish from right below the water’s surface.
Open Ocean
Some pelagic cormorant species hunt in open oceans. They eat mainly:
- Herring
- Lanternfish
- Mackerel
- Pollock
- Sand lance
Oceanic cormorants can dive to depths over 300 feet to find prey.
Adaptations for Hunting
Cormorants have special adaptations that help them dive and catch fish, including:
- Webbed feet for speedy swimming
- Long, hook-tipped beaks to snatch slippery prey
- Dense, wettable plumage to reduce buoyancy
- Adjustable throat pouches to hold multiple fish
Cormorants propel through water with their webbed feet paddling in unison behind them.
Diet and Fish Consumption
Just how much fish does a cormorant eat? A look at the diet studies and fish consumption of some cormorant species sheds light on their voracious appetites.
Average Consumption
On average, most cormorants eat about 1 pound of fish per day. However, consumption depends on the size of the bird, availability of prey, and time of year. Smaller species or juveniles may eat just 0.3-0.6 lbs daily. Breeding adults need more food and may consume up to 1.8 lbs of fish per day at peak feeding times.
Daily Intake Estimates by Species
Species | Average Fish Consumption (lbs/day) |
---|---|
Great Cormorant | 1.1 |
Double-crested Cormorant | 0.88 |
European Shag | 0.95 |
Pelagic Cormorant | 0.77 |
Estimated Yearly Consumption
Multiplying average daily consumption by 365 days, researchers have estimated the total amount of fish a cormorant may eat in a year:
- Great Cormorant: 400 lbs
- Double-crested Cormorant: 320 lbs
- European Shag: 347 lbs
- Pelagic Cormorant: 281 lbs
Cormorants are clearly prodigious fish-eaters. But studies show cormorant predation overall has little long-term impact on wild fish populations.
Impacts on Fisheries
Cormorants are sometimes considered a nuisance by anglers and commercial fishermen who accuse them of depleting fish stocks and competing for the catch. But research finds minimal impacts on fisheries.
Little Competition with Humans
Most fish eaten by cormorants are small, bottom-dwelling species not typically targeted by human fishers. There is usually little direct competition over the same fish resources.
Small Percentage of Fish Stocks
While cormorants eat lots of fish, the numbers are relatively small compared to the total fish biomass. For example, cormorants may eat no more than about 4% of the trout in a river.
Fisheries More Affected by Habitat Loss
Habitat degradation from human activities like dam construction, pollution and climate change have much greater impacts on fisheries than cormorant predation.
Cormorants Help Control Fish Populations
By preying on the most abundant small fish, cormorants may actually prevent overpopulation and help maintain balance in the wider ecosystem.
Conclusion
Cormorants are highly effective fish predators that have adapted to feast on a wide variety of fish species across marine, coastal and freshwater habitats. While they eat copious amounts of fish daily, research suggests they do not significantly compete with recreational or commercial fisheries. But more study is needed of their complex role in different ecosystems.