Marine life is changing in the South-west of England, says the influential Marine Biological Association (MBA) in its annual report for 2023, covering one of the most active areas for scuba-diving in the UK.
The MBA’s 138-page report, the tenth in the series, is edited by Dr Keith Hiscock and reflects the work of hundreds of volunteer citizen-scientists and professionals working in the South-west, according to the Plymouth-based organisation.
It says that the findings help to explain how the marine environment is changing and whether management of human activities and impacts is making a difference to the health of the seas.
2023 saw the most turtles recorded in the South-west for nine years, with most of the reports concerning “cold-shocked” juvenile loggerhead or Kemp’s Ridley turtles, says the report.
Meanwhile high numbers of cetaceans were noted coming inshore, continuing a trend that began around 2015, though the MBA says that research into the reasons for this has so far been hampered by lack of funding.
More seals were recorded dead across Cornwall in 2023 than born, with half the dead animals less than a year old. Autumn storms in particular seriously affected seal pups and juveniles. 2023 also saw the largest seal disturbance on record, when human interference caused some 250 to stampede off two adjacent beaches.
Sand tiger shark
In May, a 3m sub-adult female smalltooth sand tiger shark was found floating dead off Lyme Regis, following another reported to have stranded in Hampshire. They were both more than 300km north of any previous observation.
Several unfamiliar bony fish such as variable blennies, combers and axillary sea breams became more established in South-west waters. However, conspicuously for divers, there were declines in the occurrence and abundance of some species such as coldwater plumose anemones in inshore areas.
There were no increases in extent or abundance of warmwater seashore and seabed species that might suggest significant climate change effects, says the MBA, although common octopus eggs were recorded, suggesting that the Mediterranean species is breeding in UK waters.
Unusual numbers of salps (colonial seasquirts) and hydrozoan “crystal jellyfish” were noted in the Channel in late summer, and these were also spread over a wider area than usual. Sightings of true jellyfish revealed similar patterns to those seen in previous years but barrel jellyfish, rarely reported in 2022, made a comeback.
Crawfish and spurdog
Marine Management Organisation (MMO) analysis showed an overall reduction in quantities of fish and shellfish landed by the fishing industry in the South-west since 2016. Brown crab and mackerel stocks continued to decline, while other species such as crawfish and spurdog increased as their stocks recovered.
The MBA says that climate change will continue to benefit species such as black seabream, red mullet and anchovy while others such as lemon sole, Atlantic cod and haddock would decline.
“Excellent volunteer work continues in the South-west to remove plastics from the marine environment,” notes the MBA. “Analysis of debris from coastal cleans in 2023 by the Clean Ocean Sailing organisation also highlighted high density polyethylene (HDPE), plastic bottles and nets and ropes to be the most commonly removed debris.”
“We are grateful to all of the contributors and especially want to encourage more casual observers to send their sightings of events and of unusual species and behaviour to the section editors for the 2024 report,” says Hiscock, who hopes that the annual reports will influence policy that protects, restores and enhances marine ecosystems.
The South-West Marine Ecosystems (The State of South-West Seas) Report for 2023, published by the Marine Biological Association, is free to download as a PDF. It is. Webinars on the topics covered can be viewed on YouTube.
