Are fish animals?

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The classification of living things into groups isn’t straightforward. As a result, you may be confused about whether fish are classed as animals, or if they are something else.

Biology uses definitions to group the world into ‘kingdoms’. There’s the animal kingdom as well as separate kingdoms for things like plants, fungi and bacteria. However, even science textbooks don’t all agree on exactly how many kingdoms there are!

So, is a fish considered an animal? Yes? Or no? This article explains…

Are fish classed as animals?

According to science, fish are classed as animals. Fish belong to one of the six general animal groups which are: mammals, birds, reptiles, amphibians, fish and invertebrates. While the flesh of fish might not be considered as meat, fish are animals which have brains and can feel pain.

What type of animals are fish?

Fish are a type of animal known as vertebrates – this means that they have a backbone.

There are lots of different kinds of fish, which range in size from the dwarf minnow at around 1 cm to the whale shark which can reach up to 10 metres in length. All fish live in water and have gills, scales and fins.

Fish can be categorised into three main types:

  • Bony fish – Like tuna and salmon
  • Cartilaginous fish – Like sharks and rays
  • Jawless fish – Hagfish and lampreys
lampreys are fish
Lamprey eels have sucker mouths

What defines an animal?

According to biologists, animals are defined by having five common characteristics:

  1. Has multiple cells
  2. Obtains energy by consuming food
  3. Reproduces sexually
  4. Is made of cells that do not have cell walls
  5. Is capable of motion at some stage of their lives
  6. Responds to external stimuli

Fish meet all of the criteria for being animals, just as pigs, parrots, spiders and humans do. Therefore, it is generally agreed that fish are animals.

How are fish different from other animals?

Fish are very diverse creatures. There are more than 32,000 species of fish, which is more than all of the mammals, birds, reptiles and amphibians combined.

Sharks, rays, eels and sea horses are all 100% fish, whereas whales, dolphins, starfish and jellyfish are not fish. So what makes fish different from other animals?

Fish are unique in that they have a combination of gills and fins and that they live only in the water. While some invertebrates and amphibians have gills, some mammals and amphibians have fins and lots of animals live in water, only fish have the combination of all three attributes.

tropical fish
Fish come in all shapes, sizes and colours

Do fish have brains?

Just like almost every other animal on the planet, fish have brains. The few creatures that don’t have brains include corals, jellyfish, sea cucumbers, starfish, sea urchins, sea sponges, clams and oysters – but none of these are fish (despite having ‘fish’ in their names). They are all invertebrates.

Can fish feel pain?

It is widely accepted that fish can and do feel pain. Fish brains have neurons called nociceptors which detect intense pressure, temperature changes and caustic chemicals. Fish produce the same opioids (innate painkillers) as mammals do in response to injury.

“Anatomical, pharmacological and behavioural data suggest that affective states of pain, fear and stress are likely to be experienced by fish in similar ways as in tetrapods (mammals, birds, reptiles and amphibians).” [Source]

In 2013, the American Veterinary Medical Association published new guidelines for the euthanasia of animals, which included the following statements: “Suggestions that finfish responses to pain merely represent simple reflexes have been refuted. … the preponderance of accumulated evidence supports the position that finfish should be accorded the same considerations as terrestrial vertebrates in regard to relief from pain.”

The false belief that fish cannot feel pain causes some people to take part in hobby fishing, when they wouldn’t take part in other blood sports like shooting rabbits or deer. If they were aware that fish feel pain just like rabbits do, perhaps they would think twice.

Do fish have feelings?

Because fishes lack facial expressions, it’s sometimes assumed that they are incapable of feeling emotions. However, science is increasingly demonstrating that fish are sentient and emotional beings.

Just like other animals, fish respond to painful events with changes in their behaviour and physiology. Fish learn to avoid things that cause them harm, which helps them to survive.

It’s a myth that fish have short memories. Goldfish have been shown to remember the exact colours and locations of specific feeding tubes up to a year after exposure. [Source]

Fish may not be capable of experiencing the range of feelings that humans and some non-human animals do, such as anger, joy, worry, amusement and disgust. But to say that fish don’t have any feelings would be inaccurate.

Why would someone say a fish is not an animal?

Some people might assume that animals are medium-sized four-legged creatures, as those are the animals that they are most familiar with. They may not know that the animal kingdom spans all sorts of animals, including marine life like fish.

Another reason why people may think that fish are not animals is because of the Catholic doctrine which states that Catholics must abstain from eating meat on Fridays, but that they can eat fish. 

This may cause some people to wrongly conclude that…

  • Fish isn’t considered to be meat (TRUE)
  • Meat is made from animals (TRUE)
  • Therefore, fish are not animals (FALSE)

This type of faulty reasoning is known as a fallacy.

Why isn’t fish considered meat?

When we look at the history of how fish came to be considered not meat, we can see that this is influenced by both religion and language.

The religious definition of meat

The Catholic Church defines meat as the flesh of warm-blooded animals. It’s interesting that this classification comes from religious leaders, rather than biologists. 

There is a story which says that, centuries ago, a medieval pope with connections to the fishing industry banned the consumption of meat on Fridays to give his friends’ fishing businesses a boost. While this seems plausible, it isn’t true.

The real reason why some Catholics avoid meat on Fridays stems from the Biblical tales of how Jesus fasted for 40 days and how he died on a Friday. To honour his sacrifice, Christians originally fasted on Fridays, eating only bread. By the Middle Ages, the fast had evolved so that they were eating more things, but still avoiding the tastiest foods – meat, eggs and dairy. Eventually, people just avoided the meat.

In ancient times, meat was considered a luxury. Eating something as decadent as beef wouldn’t have been seen as an appropriate way to act on a Friday when, according to religious leaders, their focus should be on sacrifice.

The dictionary definition of meat

According to the Cambridge dictionary, ‘meat’ is defined as ‘the flesh of an animal when it is used for food’. By this interpretation, fish would be a type of meat. 

The Merriam-Webster dictionary defines ‘meat’ as ‘animal tissue considered especially for food’. However, it then goes on to specify that meat means ‘flesh of a mammal as opposed to fowl or fish’.

It seems that even dictionaries cannot agree as to whether fish is a type of meat. Whether you consider fish to be meat or not, this doesn’t change the fact that fish are animals. But it does go some way to explain why people may think that they’re not.

fish caught in a net

Is it okay to eat fish?

The decision to eat fish or not is a personal one. However, those that do choose to eat fish would be wise to educate themselves to ensure that their decision is made on sound principles.

Many people opt to eat fish because they enjoy the taste and believe that a diet that includes fish is beneficial to their heart and brain. The NHS recommends that people eat fish as it is a source of vitamins and minerals.

However, it is possible to get these vitamins and minerals from plant sources and there are some downsides to eating fish that cannot be ignored.

Reasons to consider avoiding fish:

  1. Fish feel pain when they are caught and killed
  2. Fishing causes the death of other animals such as dolphins, turtles and birds
  3. Commercial fishing is bad for the environment
  4. Fish live in polluted waters so their flesh can contain dangerous toxins like mercury  

The problem with pollution is such that although the NHS recommends eating fish, it also recommends that children under the age of 16 and women who are pregnant, breastfeeding or may wish to become pregnant in the future should avoid eating fish too often. Some types of fish should be avoided completely because pollutants can stay in women’s bodies and harm their unborn babies even years later.

Can vegetarians eat fish?

Vegetarians do not eat the flesh of animals. As fish as animals, vegetarians do not eat fish or seafood. Those who choose to avoid eating all animal flesh except for fish and seafood are known as pescatarians.

Do vegans eat fish?

A vegan diet involves abstaining from eating any animal products. As fish are animals, vegans do not eat fish.

What do you call a vegan who eats fish?

A person who follows a vegan diet with the exception of fish is known as a seagan. This portmanteau is formed by blending the words ‘seafood’ and ‘vegan’. The seagan diet isn’t new – it actually mirrors the traditional Japanese way of eating.

Seagan Vs Pescatarian

Both seagans and pescatarians avoid animal flesh with the exception of seafood. The difference is that seagans also avoid animal products like eggs, dairy, gelatine and honey, whereas pescatarians will eat these things.

feeding fish

The bottom line

Nobody can deny that fish are animals. While many definitions of ‘meat’ do not extend to include fish, this does not mean that fish are not animals. Fish have brains and can feel pain, just like other animals can. 

When deciding whether to consume the flesh of fish or not, people should be aware of the implications that this may have on their health, the health of their unborn babies, our planet and the fish and other animals that are killed as part of the fishing industry.

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