Seals and Sea Fishing

There are two species of seals present in UK waters – the grey seal (Halichoerus grypus) and the common seal (Phoca vitulina), which is also known as the harbour seal. The grey seal is common around Iceland, Scandinavia and all of Britain (apart from the south coast of England) and is also present on the east coast of the USA and Canada, while the common seal is found throughout all British waters.

Grey and Common Seal
Two species of seal are found in British waters: the common seal, left, and the grey seal.

Grey seals can grow up to 10ft in length and weigh more than 600lbs, while harbour seals grow to a maximum length of 6ft and weigh up to 300lbs. Seals breed in the summer with most females carrying and giving birth to only a single pup the following year. Pups are usually covered in a soft white coat which soon gives way to the waterpoof fur of the adults. Pups can usually swim strongly within an hour of being born – an essential skill for baby seals born on a sandbank at low tide who will have no choice other than to swim as the tide approaches!

Seal South Shields
A seal spotted in the North Sea off the coast of South Shields. There is a major seal colony nearby on the Farne Islands off the coast of Northumberland.

There are major grey seal colonies off the coast of New Jersey in the United States and Newfoundland in Canada, while Britain’s largest seal populations are off the Orkney Islands in Scotland and the Farne Islands in North East England. Seals are not under threat or endangered and the IUCN (International Union for the Conservation of Nature) classes both grey and common seals as a species of Least Concern. In certain parts of the world, such as the USA and Canada, seal numbers have increased notably in recent years.


Common Seal Hunting Underwater
A common seal hunting for fish underwater.

Both species of seals have diets which are primarily made up of fish. They are unfussy predators and will consume any fish species they can hunt down. Small species such as mackerel, herring, sprats and sandeels are the most common species consumed, but larger fish such as cod, ling, bass, sea trout and any bottom dwelling flatfish such as flounder, plaice and dab will be eaten. Despite being an air-breathing mammal seals will dive down and hunt for fish at depths of 100 metres, and will stay underwater for 3-6 minutes at a time, although it is thought that both common and grey seals can reach maximum depths of 200m and stay submerged for around 20-25 minutes. Seals can travel up to thirty miles away from their colony when hunting and can spend around nintey per cent of their hunting time underwater. If other species are not abundant seals are more than happy to eat other sea creatures with octopus, squid, cuttlefish and even crab and lobsters are taken. In parts of the world (such as South Africa) where fish stocks have been decimated by industrial fishing seals have been known to catch and consume sea birds, including large predatory species such as gannets. Indeed, seals in the UK have even been known to emerge from the water and kill dogs, although this is thought to be due to the seals protecting their young and larger mammals are not seen as a food source for seals.

How Much Fish do Seals Actually Consume?

Bearing all this in mind it is clear that despite their cute appearance and their comical and playful manner when out of water seals are in fact active and at times aggressive predators. There has been much debate on the amount of fish that seals actually consume. It is thought that fully grown adult common and grey seals consume around 5-10% of their bodyweight in fish or other marine creatures when they feed (although it has to be noted that they do not feed everyday, and do not eat anything at all in the breeding season). If we take an average grey seal as weighing 350lbs and say it eats 7% of its bodyweight this would equate to around 24-25lbs of fish every time it feeds. Clearly in areas where large seal colonies are present there is no doubt that they are eating a lot of fish. In some parts of the world it is claimed that seals consume as much fish as the commercial fishing industry takes, whereas others have blamed seals for the failure of fish stocks to recover when restrictions on commercial fishing are put in place. However, there is much opposition to the view of seals as detrimental to fish stocks. A European Parliament technical paper entitled Seals and Fish Stocks in Scottish Waters came to the clear conclusion that “the effects of predation by both species of seals on overall stock abundance of most fish species is likely to be insignificant” (pp. 31), pointing out that seals consume relatively little fish compared to other species – seabirds for example are thought to eat twice as many fish as seals in Scottish waters. A study carried out in Ireland in 2015 also found that seals had a negligible impact on fish stocks and highlighted the fact that seals mostly ate smaller fish which commercial fishermen were not allowed to take. However, there are seal culls in Britain with several hundred seals shot in Scottish waters every year to protect the salmon stocks in fish farms (update: as of summer 2020 legislation is progressing through the Scottish parliament to ban fish farms from shooting seals).

Sea Anglers and Seals

There is the belief that a seal being present in an area where an angler is fishing will mean that the chances of the angler catching anything will be massively reduced. Some anglers even go so far as to pack up and move elsewhere (or go home) as soon as they see a seal nearby. There is no need to this as seals and anglers can co-exist and the apperance of seals is likley to mean that there are fish present in the waters being fished. People need to be extremely careful when interacting with seals as they can quite easily lose their natural fear of humans (and therefore danger) and become reliant on humans for food. Excellent advice on angling when seals are present is available here.

In 2018 anglers were accused of shooting seals dead, as the seals were allegedly interfering with their fishing, although there was no evidence to support the allegation that anglers were responsible. In 2020 national news outlets reported that an angler threw and empty beer bottle at a seal when it interfered with his fishing. Such incidents create a terrible impression of anglers.

What is the Answer?

In the end there is one answer to the seal/fish consumption question – restore fish stocks back to natural levels, or as close to natural levels as we can. If we eliminate the worst excesses of the commercial fishing industry (huge industrial trawlers, the wasteful practice of throwing perfectly good edible fish back into the sea dead as discards, destructive fishing methods such as beam trawling and dredging) then there will be more than enough fish to go round for everyone – anglers, seals, and a responsible and sustainable commercial fishing industry. Seals have fed on fish for thousands of years and the simple fact is that seals only consume a tiny amount of fish when compared to commercial fishing operations. Seals cannot possibly be responsible for the relatively recent reductions in fish stocks – that is entirely the fault of humans who have overfished the seas in an unsustainable manner for too long. Blaming seals for the reduction in fish stocks in Britain is badly misguided and a cull of seals will do absolutely nothing to solve the deep seated problems which are reducing Europe’s fish stocks to record low levels. Culls only make sense in very specific areas where seal populations have rocketed (mostly in the USA and Canada) and British and European anglers worried about reducing fish stocks would spend their time much more productively by campaigning to reform the Common Fisheries Policy and ban the wasteful practice of discards, rather than direct their attention at seals.