The Return of the Sprat

Photo copyright: Aberdeen University


Small fish that live in open water and form a significant part of the base of the marine food chain have returned in huge numbers to the Clyde, according to new research from scientists at the University of Aberdeen.
Sprat – a fish which is food for many other marine species – has increased its numbers 100-fold since the late 1980s, the study shows.

The Clyde was once a thriving marine ecosystem with large fisheries for herring and other species such as cod and haddock.  In recent decades, these fisheries have disappeared, largely due to overexploitation in the latter part of the 20th century, although a sustainable prawn fishery now operates. Herring fishing, in particular, disappeared in the late 1990s.

The new Aberdeen-led study, published in the journal Current Biology, has shown that although herring are still present, populations of sprat, a related species, are now 100 times more numerous, with the combined total biomass (or weight) of herring and sprat now almost four times the size it was in the late 1980s, which was the last time they were measured.

The authors, working with Marine Scotland Science on their vessel Alba na Mara, used scientific sonar equipment to detect enormous schools of sprat – some were over 2km long and over 30m (100 ft) deep.  They then used advanced sonar processing techniques to estimate the numbers of each species over three years from 2014 to 2016. The total weight of sprat in 2016 was estimated at over 70,000 tonnes, equivalent to a population size of 23 billion individuals.

Dr Joshua Lawrence, who led the study which was funded by the Marine Alliance for Science and Technology Scotland (MASTS), was surprised by the results: “The Clyde is famous for its herring, but although there has been virtually no fishing pressure on herring in over 20 years, it is the sprat population that has bounced back, not the herring. We can only speculate as to why this has happened – perhaps it is the warming seas, which may favour the sprat, or their more favourable reproduction strategy, as herring need particular gravel beds to spawn, whereas sprat do not. “We also found a large concentration of krill in the Clyde – a major food source for the fish and for other larger animals such as minke whales which are known to visit the area. 

So, there are large populations at various levels of the marine food chain, which tells us that the Clyde’s marine ecosystem is faring better than previously thought, despite centuries of overexploitation.”  

Professor Paul Fernandes, a fisheries scientist at the University’s School of Biological Sciences, who supervised the study, said: “Sprat form a critical part of the marine food chain, and are vital for other larger fish such as cod and whiting, as well as other animals further up the food chain such as seabirds, whales, dolphins, and sharks. It is fantastic to see these parts of the food chain recover. This should, in time, lead to recovery of the populations of the larger animals that feed on them.” He added: “It does now provide an interesting dilemma for fisheries managers and the local seafaring community.  A sprat fishery could operate, but perhaps a more sustainable and more lucrative opportunity could present itself through whale watching.  There have been anecdotal reports of more whales and dolphins appearing in the Clyde; and in a related study, we detected large numbers of porpoises in the area.  As these whale populations themselves recover, they may find their way into these rich feeding grounds, much as they once did, and I am sure people would pay to see them, as they do in other parts of the world where marine ecosystems have recovered.  The key will be to do this responsibly to ensure a long-term future for the Clyde’s historic seafaring community.”

200th osprey chick for pioneering Rutland Osprey Project

Photo: Andy Rouse

A ground-breaking project that reintroduced ospreys to England and helped bring them back to Wales has seen its 200th chick fledge this year.

Leicestershire & Rutland Wildlife Trust started the project 25 years ago because ospreys had become extinct in England and Wales. As a result of the project, ospreys have now spread across the two countries.

Ospreys are a huge fish-eating bird of prey with a wingspan of nearly 5 feet and can live for up to 20 years. The 200th chick, a female, fledged in July and was ringed with the number 360 to identify her.

Abi Mustard, Osprey Information Officer for the Leicestershire and Rutland Wildlife Trust, says:

“This year is an important and exciting year for the Rutland Osprey Project – we’re thrilled to be celebrating our 25th anniversary and also welcoming the 200th chick. It’s brilliant that we now have a self-sustaining population of ospreys in England. The success of the Rutland Osprey Project is not only due to the resilience of the birds themselves, but also to the hard work, support and dedication of everyone who has been involved – we have a wonderful team of volunteers, staff, local landowners and supporters who have helped facilitate these incredible achievements. We are all looking forward to seeing what the next 25 years brings.”

Leicestershire and Rutland Wildlife Trust launched the Rutland Osprey Project in 1996 in partnership with Anglian Water and the Roy Dennis Wildlife Foundation to reintroduce this magnificent bird of prey to the skies of England, where they had been extinct for over 150 years.

As well as establishing an osprey population in and around Rutland Water nature reserve, the project has helped the birds to breed in other parts of England and Wales.

Ospreys are now found breeding in Cumbria, Northumberland and North and West Wales, while Suffolk Wildlife Trust is working with the Rutland Osprey Project and Roy Dennis Foundation to bring breeding osprey back to East Anglia for the first time in over a century. Essex Wildlife Trust has erected nesting platforms around the Abberton Reservoir to attract the birds.

The Scottish Wildlife Trust has been helping to increase the number of ospreys in Scotland for over 50 years. Three of its reserves host breeding pairs. The Trust’s Loch of the Lowes Wildlife Reserve has been at the forefront of the recovery of the species since 1969, when it became the fifth known breeding site in Britain. 85 chicks have fledged from the reserve in the past 52 years.

Ospreys were once widely distributed across the UK, but faced intensive persecution through shooting, egg collecting and habitat destruction, which eventually led to their extinction as a breeding species in England in 1847.

In the mid-1950s a population in Scotland began to slowly recover, however it was estimated that it would be approximately another 100 years before breeding ospreys would naturally recolonise central and southern England.

In a first, to help re-establish the birds to central England, the Rutland Osprey Project started translocating birds in 1996, carefully collecting 64 osprey chicks from Scottish nest sites and releasing them in Rutland between 1996 and 2001. A further 11 female birds were translocated in 2005. The first breeding pair of ospreys successfully raised a single chick at Rutland in 2001, and 25 years later, there are now approximately 26 adults including up to ten breeding pairs in the Rutland area.

2021 has brought another major milestone with the 200th chick, which hatched on a nest situated nearby on private land. The team hope she will return to Rutland to breed when she is mature.

Rob Stoneman, director of landscape recovery for The Wildlife Trusts, says:

“Seeing 200 chicks successfully hatch at the Rutland Osprey Project is a fantastic achievement. These beautiful birds belong in our skies, and it’s thanks to the hard work of so many people over the last 25 years that we now have osprey across England and Wales. Success stories like this prove what’s possible and help us to visualize how our countryside could look in the future – with wildlife in abundance, a rich tapestry of habitats, green corridors for species to move through landscapes, rivers and lakes free from pollution, and access to nature for all.”

This year’s osprey chicks will likely remain in Rutland until early September, before they begin their remarkable 3000-mile migration journey south, to the west coast of Africa. The chicks will remain in their African wintering grounds for the first couple of years, so it won’t be until at least 2023 before we see if the 200th chick returns.

Read the latest news from the Seahorse Trust

Seahorse trust spring-summer-Newsletter-2021

Captive breeding programme essential for vultures’ survival

  • A new study shows that supporting a declining population of a migratory vulture with captive-reared young birds every year could delay imminent extinction
  • Whilst releasing even 15 captive birds each year will not be enough to maintain the population, it will buy conservationists enough time to remove threats
  • So many Egyptian vultures have died that the Balkan population has declined from >600 pairs in the 1980s to only 48 pairs in 2020

A new study shows that supporting a declining population of the Egyptian vulture with captive-reared young birds every year could delay extinction. However, further work is required to remove threats and ultimately guarantee its survival.

The results of this work, published today in the Journal of Applied Ecology, show that as long as there is a lot of human-induced mortality along the flyway and no improvement in survival, releasing even up to 15 captive-reared birds every year would not be sufficient to maintain the Balkan breeding population.

However, this approach would buy the conservationists some time to remove threats along the flyway, because the extinction risk in 30 years was markedly lower with than without population reinforcement. That time could then be used to increase survival of birds in the wild by about 6%, which would be sufficient for the population to be self-sustainable without the need for further captive releases.

Steffen Oppel, RSPB’s Senior Conservation Scientist and lead author of the study said: “Predicting the future trend of a population is always very difficult, and there is a lot of uncertainty in our predictions. But despite this uncertainty, we can be quite confident that unless we reduce the survival of wild birds along the flyway our hope of maintaining the Balkan population would be very slim – regardless of the fantastic efforts to raise birds in captivity.”

The Egyptian vulture is a large bird of prey found through most of southern Europe, however numbers have declined by more than 50% since the 1990s. Vultures provide the vital service of removing rotting carcasses from the landscape. Whether dead cattle, elephants or antelopes – vultures ensure that these carcasses are cleaned up free of charge. The catastrophic decline of vultures in India led to an overabundance of feral dogs and increased rabies infections in people.

Egyptian Vultures breeding in eastern Europe migrate around 5000 km twice a year between breeding and wintering regions. These journeys are hazardous, and many birds die from human and natural threats along the way, such as direct persecution, inadvertent poisoning, or electrocution and collision with power infrastructure.

This study comes hot on the heels after another paper published last week in the journal Bird Conservation International which identified electrocution from poorly-designed powerlines as a serious threat for Egyptian vultures. In this paper, scientists called for funders and Governments to invest in infrastructure which eliminates the electrocution risk to large birds.

Many migratory species are threatened, and their conservation is often tricky, because it requires the collaboration of many countries. But there is some hope for the Egyptian Vulture population on the Balkans. Work is progressing in many countries to reduce wildlife poisoning, refurbish dangerous power infrastructure to reduce accidental deaths from collision and electrocution, and to reduce the direct persecution of vultures.

Many more years of monitoring will be needed to show whether these efforts along the entire flyway actually lead to the required improvement in survival. But in the meantime, the release of 4-6 captive-reared young birds every year will afford conservationists some time to tackle the Herculean task of reducing threats across the three continents that Egyptian Vultures cross twice per year on their annual migrations.

Rare Butterflies thrive in Mabie Forest

Belted Galloway cattle are helping these butterflies flourish,

read about it HERE>

photo credit: Jim Asher/BCS


Rare white puffin spotted on Scottish island

Photo credit: Dora Hamilton

A leucistic puffin has been seen on Handa Island, off the Sutherland Coast.

Read about it HERE>