Harbor seals decline in Tay and Eden as marine mammals struggle.
Harbor seal numbers in the Tay and Eden estuaries have dropped 95% as figures show marine mammals are in trouble.
According to the latest statistics from the government agency NatureScot, marine mammals, including seals and cetaceans, are listed at the bottom of the table of species classified by “favorable status”.
NatureScot said the figure for marine mammals is largely due to the decline in harbor seals – which has been dramatic in Tayside and Fife.
In 2000, the Firth of Tay and Eden Estuary Special Area of Conservation was home to around 700 harbor seals, or around 2% of the UK’s total harbor seal population.
But by 2018, the numbers had dropped to around 40, a drop of almost 95%.
Academics in the Marine Mammal Research Unit at the University of St Andrews are studying the reasons for the decline.
Conflict between species
One theory is the increase in the number of gray seals, which are known to kill harbor seals.
Marine Mammal Research Unit (SMRU) director Dr Carol Sparling said it was likely a combination of factors.
“Harbor seals in a number of areas around Scotland have suffered a fairly significant decline while gray seals, especially on the east coast, have seen a massive increase in their numbers,” she said. .
Harbor seals are also in decline around the north coast, Orkney Islands and Shetlands.
Meanwhile, harbor seal populations on the west coast of Scotland have remained stable or increased.
There is clearly something happening in terms of adult survival. “
Dr Carol Sparling, SMRU
“We had this study where we looked at two contrasting populations,” Dr. Sparling said.
In Orkney, the number is dropping, but in Skye the population is increasing, she noted.
“We… are trying to understand the essential difference between these two populations,” she added.
“There is still no clear picture of what could be causing the decline. It is probably a combination of factors.
“What is clear is that the rate of decline has been high enough to understand that there is clearly something going on in terms of adult survival.”
Pregnant seals found dead
She added: “We know that locally around the coast of Fife there have been numerous cases of dead harbor seals – adult and often pregnant female harbor seals that have fallen victim to predation by gray seals.
“Large male gray seals will actually kill adult harbor seals.”
As harbor seals decline, nature watchers are now more likely to see gray seals around the coasts of Fife and Tay.
Dr Sparling said: “These days it’s probably mostly gray seals, although there are pockets where you will see small groups of harbor seals.
“There has been a bit of a change, especially in the Tay, where we had a very large population of harbor seals.
NatureScot claims that more than three-quarters of Scotland’s natural features – wildlife habitats, species and geological features – are in good condition or in the process of recovery.
Decrease since 2016
But the latest statistics suggest that there has been a decrease in the proportion of natural elements doing well in protected sites.
Protected sites include Sites of Special Scientific Interest, Special Areas of Conservation, Special Protection Areas and International Ramsar Sites.
According to NatureScot, the proportion of natural elements under favorable conditions peaked in 2016 at 80.4%. It now stands at 78.3% – half a percentage point lower than the previous year.
However, there has been an overall improvement since 2005, when the figure was 71.4%.
Invasive species threaten forests
As marine mammals struggled, the state of marine habitats fared better. Over 98% were in favorable condition.
Forests face the most challenges, with the proportion in good condition only 64.3%.
Invasive species are said to be the greatest threat to habitats, followed by overgrazing.
Dr Sparling said the variety of whales and dolphins visiting the Forth suggested there was an abundance of food for marine life in the estuary.
And she said increased awareness of the value of marine habitats was cause for optimism.
In particular, public interest in recent whale sightings – including the surprising sight of a sei whale in the Forth – has increased public engagement in marine conservation.
Whales and dolphins are good news
“There is good local news as far as what’s going on in the Forth,” said Dr Sparling.
“The number and variety of cetaceans, whale, dolphin and porpoise species that we see locally have increased dramatically in recent years.
What it does, especially for local communities, is to raise awareness of the marine environment. “
Dr Carol Sparling, SMRU
“There must be something to eat. I guess the waters are cleaner and there are more fish to eat.
“There is still a lot of expedition activity in the Forth. We cannot exclude that this may have an effect, the noise of all these big tankers coming in and going out. But what we do know is that it doesn’t force them to stay away completely.
She added: “What it does, especially for local communities, is to increase awareness of the marine environment and the value of the marine environment, as well as the importance of the health of the marine environment.
“People clean the beach once a week, trying to get rid of the plastic in the environment.”
SMRU is studying how bottlenose dolphins are expanding their range through their Citizen Fins project.
The project encourages members of the public to submit photographs of dolphins they see, taking care not to disturb the animals.
National targets could protect habitats
Nick Halfhide, Director of People and Nature at NatureScot, said the national targets for 30% of Scotland’s land and seas to be in a protected area by 2030 present a “real opportunity” for ‘reverse the loss of nature.
He added: “Scotland’s protected areas have a vital role in strengthening ecological networks and helping us build resilience in the face of the twin challenges of climate change and biodiversity loss.”