Do otters eat fish?

This article will answer the questions “Do otters eat fish?”. We will learn which types of fish otters eat in marine and freshwater environments, and also some other predators of fish. Initially, we will understand who the otters are and their general characteristics. We will then understand the main different types of otters, their foraging behaviours and habits. 

Do otters eat fish?

Yes,  Otters eat fish. The main course for the majority of otters is fish. River otters can eat up to 4 kilograms daily. Do you think that is too much for a 35 kg cute otter? All of the otter species eat between 15 and 30% of their body mass daily. This is because they have a very fast metabolism. In general, they spend around 5 hours per day hunting.

The most common fish consumed by the different otter species are:

–       Carp;

–       Sunfish;

–       Sculpin; 

–       Catfish;

–       Eels; 

–       Perch;

–       Minnows;

–       Suckers;

–       Trout;

–       Salmon.

The sizes of fish otters eat are between 1,75 to 50 centimetres. However, giant otters can eat even bigger prey. If they cannot find fish around, they can even eat ducks and rabbits. 

Who are the otters?

Otters are mammals that spend the majority of their time in the water. They inhabit from freshwater to marine environments, from rivers and lakes to oceanic areas. However, they prefer locations with low or without human activities. Thus, they are considered semi-aquatic animals.

Their bodies are slender and elongated. Some of the individuals can reach up to 2 metres long. Their body shape, interdigital membrane, and strong tail are great adaptations to aquatic environments.

Otters have light to dark brownish fur that protects them from losing heat, with thermic impermeable isolation. Their olfaction, vision and audition are highly developed. These systems development allow the otters to capture their prey very successfully.

Otter species

Currently, there are 13 living otter species. They inhabit different environments, from freshwater to marine. Thus, otter species that occupy different environments will feed and behave differently. 

Although they feed on different species, the groups of animals that are part of the otters’ menu are the same. Thus, generally speaking, they feed mainly on fish. But can also feed on other aquatic animals, such as molluscs, crustaceans, small mammals, amphibious, eggs, snakes, and small birds. 

Otters are classified as opportunistic predators. This means that they select the prey according to their escape speed. Thus, the selected individuals are the easier-to-catch ones. 

How do otters capture fish?

The otters’ fishing behaviour varies according to the species of fish they are hunting. However, they normally choose the easier-to-catch prey. This means that sick and old fish are the ones caught. Otters avoid chasing their prey.

There are records of otters collaboratively fishing with fishermen in Bangladesh. They chase the fish towards the fishing net, capture their fish and reduce the fishermen’s efforts.

What about pet otters?

Otters as pets have become a very popular practice. To raise these animals as pets, some basic conditions are required. Very specialized diet and vaccines are among these basic conditions.

Breeding otters is a very difficult practice. However, getting them from the wild could cause serious problems related to socialisation and environmental equilibrium.

According to some experts, pet otters diets can be based on nutritionally complete cat food. More than 90% is required to be meat-based food. However, 90% is recommended to be fish. If the fish is frozen, it would be necessary to supplement the otters’ diet with vitamin E. It is also very important to maintain the natural daily consumption, around 20% of their body weight daily.

In addition, it is recommended also to plan enrichment activities for pet otters, that is because their natural behaviours of hunting and spending energy are affected by captivity. Thus, a few ideas of environmental enrichment for otters are below:

–       Iced fruits in cubes/buckets during hot days;

–       Hide and seek with feathers and food items;

–       Toys and entertaining activities with food dispensers.

What other predators eat fish?

As seen above, fish are the main course on the otters’ table. However, they are also part of the diet of many other species. Such as:

–       Aquatic mammals;

–       Terrestrial mammals;

–       Reptiles;

–       Insects;

–       Birds;

–       Fish.

Aquatic mammals

Although otters are semi-aquatic mammals, other aquatic mammals are also predators of fish. Sea lions, seals and other pinnipeds prey on a diversity of fish. Marine and river delphinids and other cetaceans also have a diet that includes fish. Usually, they eat smaller fish, once they are not able to chew their prey.

Terrestrial mammals

Few terrestrial animals perform fishing behaviour to obtain their food. Bears and jaguars are known to hunt fish on rivers. 

Reptiles

Crocodiles, alligators, large lizards, snakes, and turtles also prey on a huge variety of fish, from larval and juvenile small fish to large adult fish.

Insects

Insects and some insect larvae can also prey on some fish at an early life stage, eggs, and just hatched fries.

Birds

Many bird species rely their diets on fish as the main item. From riverine fish to oceanic species. However, shallow waters make fish more susceptible to bird hunting. Birds can feed on fish at all stages and their hunting behaviour is normally associated with shoals concentration. 

Fish

Predatory fish are also a problem for fish. Sharks and some other large species, such as barracuda, prey on smaller fish. 

Humans

However there are also other animals threatening the fish, none of them compares to the biggest threat of all, Human beings. 

Overfishing is a huge issue for fish populations. Overfishing means fishing more fish than the population capability of recovering. Consequently, the population becomes depleted. Commercial fishing is responsible for a massive amount of fish waste through by-catch. Therefore, not only the commercial species is affected, but all the others that come from the fishing net.

Besides overfishing, habitat destruction and pollution have enormous impacts on aquatic environments. These anthropogenic impacts affect not only the fish but other aquatic animals too. As noticed above, fish are a part of most animal groups menus. And if contaminated by human activities, fish will indirectly contaminate many other animal groups.

Conclusion 

Here, we answered the question “Do otters eat fish?”. Firstly we learnt about otters biology, behaviour, and their diet. Then we understood what fish species are normally eaten by otters. We also discussed pet otters and other fish potential predators.

If you have any doubt, feel free to join us with a comment below!

Frequently Asked Questions (FAQs): Do otters eat fish?

How many kilograms of fish can an otter eat? 

Otters require at least 15 % of their body weight of food daily. However, their consumption may reach up to 30 % of their body weight in the case of giant otters. This is because otters own a very fast metabolism, which requires a high amount of energy to perfectly function.

How do otters move? 

Otters are very good swimmers. In the water, they can reach up to 109 km per hour. Generally, they have interdigital membranes that support their swimming activities. In addition to the interdigital membrane, they also have an extremely robust tail that also supports swimming. On land, they do not face any issue referring to locomotion. They can even chase some small prey if needed, although they normally opt not to chase their prey. 

How long can an otter be submerged? 

Although otters prefer to capture easier-to-catch prey, sometimes they need to chase or even escape from a predator. Thus, they are capable of staying submerged for up to (hold your breath!) 6 minutes. 

Do otters eat the entire fish?

Yes. Otter begins to eat the fish by their head. Occasionally, they may leave the fish bones. Sometimes, otters may invade fish farms and steal fish from the ponds. This behaviour can be detected because they leave tracks of fish waste behind.

What is the otters’ environmental function? 

The otters’ function is extremely important to the ecosystem. They occupy a space at the top of the food chain. Thus, they can be considered biological indicators. In addition, otters also help to control some animal populations. As they prey on sicker, older and/or weaker individuals, they maintain the populations’ health.

Are otters friendly? 

Otters can be very friendly and social within their group. In the wild, the otters’ group can have 15 members. However, they can become very aggressive during periods of lack of food, for example. Pet otters may have problems in socializing with other domestic animals, and can even become aggressive if they understand a dog as a threat.

Can I hunt otters? 

In the past, hunting otters had a huge importance in the fashion market. Nowadays, this market is extremely low. In addition, hunting otters is rigorously restricted by law. Although laws vary from country to country, biologically speaking, by removing a predator from the top of the food chain, you will cause an enormous disequilibrium in the ecosystem. Some otter species are already classified as vulnerable or at risk of extinction, thus conservation practices are recommended in respect to the otters.

References 

SeaWorld Parks & Entertainment. Diet & Eating Habits. https://seaworld.org/animals/all-about/otters/diet/

Dotson, J.D. 2018. What Do River Otters Eat? https://sciencing.com/foods-do-harp-seals-eat-6747374.html

The Otters Diet and Feeding. https://ottersandbutterflies.co.uk/pages/otters-diet-and-feeding

Do Otters Eat Fish? https://wildexplained.com/do-otters-eat-fish/

Predators, Their Damage and Control in Fish Culture. https://agrisujan.wordpress.com/2018/04/04/predators-their-damage-and-control-in-fish-culture/

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