Prey availability

Seals must find fish to survive, so anything that affects their ability to do so impacts their survival prospects. Humans have become more effective and efficient fishers. This has dramatically reduced stocks available to marine wildlife including seals. Overfishing and unsustainable fishing practices, symbolised by factory supertrawlers, present the most fundamental risk to seals.

Fisheries also present a bycatch risk to seals. Static, drift and trawl nets are a physical risk to foraging seals, whose panic response is to spin. Seals asphyxiate rather than drown, as their dive reflex prevents them from taking a breath underwater.  Bycatch is a major issue, for example in the southwest of England it was estimated to have killed 310 seals in 2015 alone.

Climate change impacts seals in multiple (often unexpected) ways.

Acidification and warming

Feeding grounds are shifting with prey species changing and moving. Red tide algal blooms create toxins such as domoic acid. This has been found in seals and severely affects the functioning of their neurological systems.

Sea level changes

Rising sea levels will change the habitat available to seals for foraging, digesting, resting and pupping. Low lying haulouts are being lost, particularly the sheltered estuarine habitat favoured by harbour seals. Capable of adapting over time, it is hoped that new haul-outs will also become available to seals. New sites will inevitably be more marginal and push seals into coastal spaces more popular with humans.

Pupping caves are now flooded during storm events that are common during the pupping season. Flooding of caves will become more frequent, forcing seals to have pups in coves more accessible to humans.

Extreme weather events

Storms are an obvious risk to seals, particularly white coated pups, moulted pups and juveniles. Youngsters lack the experience and body strength to cope in massive waves. This results in a variety of life-threatening trauma injuries from smashed skulls to broken jaws, flippers and ribs.  

Groundswells associated with storms rip fishing gear from moorings adding to the amount of lost gear floating in our oceans. Seals play with lost rafts of net and become live entangled around their necks and abdomens. This results in life shortening injuries and a considerable welfare issue. Entanglement affects around 4% of seals in the southwest of England. This is the second highest rate of entanglement for any phocid seal species anywhere in the world and potentially a population level effect.

Heavy rain saturates rocks increasing the rate of coastal erosion and cliff collapse. Rockfalls prevent haul outs being used. Worse still they have blocked seal pupping caves during the pupping season, trapping mothers and pups inside.

Runoff from the land impacts water quality, which is critical for all marine life. In some countries, the outflow of raw sewage into our oceans has reduced. However, agricultural chemicals and nutrients are washed off exposed fields with soil adding toxins and silt to the water column. When seals are young and teaching themselves to feed, juveniles struggle to find food. This is made harder in rough conditions with very low visibility and where turbid conditions prevent their whiskers feeling for food.

Human activity: Interaction and disturbance

Commercial, business, tourist and recreational use of our coastal fringe squeezes the habitat available to seals into smaller and potentially more marginal, sub-optimal areas.

Modern technology enables people to access seal sites more frequently. This hugely increases human interaction resulting in increased disturbance levels from land, air and sea.

Unlike many marine species, seals are exposed to a range of different anthropogenic effects when hauled out on land. In this respect, seals most resemble sea birds with their marine and terrestrial habit.  Seals need to haul out on land to rest, socialise, digest their food and replenish emergency oxygen supplies.

Most disturbance incidents are unintentional resulting from a lack of awareness about how to watch seals well.

Harbours

Originally, seals were attracted into harbours by the discards fishers threw overboard. Now they are fed by the public. This leads to a lifetime of humanised behaviour in a very dangerous environment. Seals are known to have been severely injured by propellers and boat strike. The impacts of inhaling light grade diesel fuel oil leads to a slow organ failure and death. Please practice ‘tough love’ and never feed a wild seal.

Household outflows

Chemicals such as bleach from household cleaning products, microplastics from washing machines and pharmaceutical runoff (from prescription medication and hormone replacement drugs) are being flushed into our oceans at ever-increasing rates presenting new and emerging threats to seals and other marine life.

Marine debris

A wide range of human-related items are lost into the sea. These range from containers of plastic raw material pellets to products and items left on coastal fringes. Rubbish blows into the sea and inland litter washes down rivers into the sea.  The variety and quantity of items lost at sea has increased exponentially. Despite all our best efforts, these present a variety of risks to seals. Plastic that has absorbed toxins can be ingested. Any looped item poses an entanglement risk.