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 most 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 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 thick fur of the adults. Seal pups often have to swim just hours after birth as the tide comes in over the areas where they were born.
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 off the coast of 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.
Diet
Both species are unfussy predators and will consume any fish species they can catch. Small species such as mackerel, herring, sprats and sandeels are most commonly consumed, but larger fish such as cod, ling, bass and flatfish will also be eaten. Seals will hunt at depths down to around 300ft (100 metres) and stay underwater for around five minutes, although it is believed they can stay submerged for a maximum of around twenty minutes. Seals can travel up to thirty miles away from their colony when hunting and can spend around 90 per cent of their hunting time underwater. If fish are not abundant seals will eat other sea creatures with octopus, squid, cuttlefish and even crab and lobsters being 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 per cent of their body weight in fish or other marine creatures when they feed. For an average grey seal weighing 400lbs, this would mean that it eats around 28lb of fish every time it feeds, although it has to be noted that they do not feed every day, and do not hunt at all in the breeding season.
Clearly, in areas where large seal colonies are present, there is no doubt that they are eating a lot of fish. Research carried out by the University of Gothenburg in Sweden claimed that seals in the Baltic Sea consumed the same amount of fish as the commercial fishing industry took, while a paper published in the academic journal Applied Ecology claimed that seal predation was preventing the recovery of the west of Scotland cod stocks. 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”, 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 permitted to take.
Seals can also take fish from the open water pens used in Scottish salmon farms, damaging the nets and allowing salmon to escape in the process. Representatives of the Scottish fish farming industry claim that seals are a significant problem. Several hundred seals shot in Scottish waters every year to protect fish farm salmon stocks. Legislation introduced by the Scottish parliament in 2020 restricted the fish farms’ ability to shoot seals, leading to fish farmers claiming seals were becoming bolder in their attacks on fish farms and were costing the industry £13 million worth of salmon per year.
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 catching fish will be significantly 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. This may be an overreaction as there are plenty of reports of anglers catching fish when seals are present and the fact that a seal is actively hunting in the area means it is likely that fish are also there.
In 2018 anglers were accused of shooting seals dead, as the seals were allegedly interfering with their fishing, although there was no evidence provided to support the allegation that anglers were responsible. In 2020 national news outlets such as the BBC reported that an angler threw and empty beer bottle at a seal when it interfered with his fishing. Such incidents create an extremely poor image of anglers and if anglers are annoyed at the presence of a seal the only responsible course of action is to pack up and go fishing somewhere else.
What is the Answer?
Seals are not responsible for the reduced number of fish in the sea – 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 little to solve the deep-seated problems which are reducing Europe’s fish stocks to record low levels. Anglers worried about reducing fish stocks would be spending their time much more productively by campaigning to ban destructive commercial fishing practices and restore the health of Britain’s marine environment, rather than directing their attention at seals.