Mystery over decline in sea turtle sightings

Date:
October 19, 2020
Source:
University of Exeter
Summary:
The number of sea turtles spotted along the coasts of the UK and
Ireland has declined in recent years, researchers say.



FULL STORY ==========================================================================
The number of sea turtles spotted along the coasts of the UK and Ireland
has declined in recent years, researchers say.


========================================================================== University of Exeter scientists studied records going back more than a
century (1910-2018) and found almost 2,000 sea turtles had been sighted, stranded or captured. Recorded sightings increased dramatically in the
1980s and 1990s - - possibly due to more public interest in conservation,
and better reporting schemes. Numbers have dropped since 2000, but the
reasons for this are unclear.

"Lots of factors could affect the changing of numbers of sea turtles
sighted," said Zara Botterell, of the University of Exeter and Plymouth
Marine Laboratory. "Climate change, prey availability and environmental disasters such as the 2010 Deepwater Horizon oil spill could all influence turtle numbers and behaviour.

"However, sea turtle populations in the North Atlantic are largely stable
or increasing, and the apparent decrease may represent reduced reporting
rather than fewer turtles in our seas. One reason for this could be
that fewer fishing boats are at sea now than in the past -- and fishers
are the most likely people to see and report turtles." The most common
turtles spotted off the UK and Ireland are leatherbacks - - making up
1,683 of the 1,997 sightings since 1910. Leatherbacks are thought to be
the only sea turtle species that "intentionally" visits these waters,
with adults arriving in summer in search of their jellyfish prey.

Meanwhile, juvenile loggerheads (240 since 1910) and Kemp's ridley turtles
(61) are more often spotted in winter -- likely carried on currents and
finding themselves stranded in cold waters.

There are seven sea turtle species in total, and the others are much
rarer in UK and Irish waters. Only 11 green turtle sightings were found
in the records (all from 1980 to 2016), while just one hawksbill (Cork,
Ireland in 1983) and one olive ridley (Anglesey, Wales in 2016) have
been recorded. The only species never recorded in UK or Irish waters is
the flatback, which is only found around Northern Australia, Southern
Indonesia and Southern Papua New Guinea.

Most of the recorded sightings of turtles in the UK and Ireland were
along western and southern coasts. Of the 1,997 turtles sighted, 143
were "bycatch" (caught accidentally) in fishing lines, nets and ropes --
and the large majority of these were released alive.

The study used the TURTLE database, operated by Marine Environmental Monitoring.

The research team thanked the many members of the public who have reported turtle sightings and strandings, and noted the "pivotal role" of the UK Cetacean Strandings Investigation Programme (CSIP) and Scottish Marine
Animal Stranding Scheme (SMASS), funded by UK governments.

"We have been lucky to analyse this unique dataset that exists because
Britain and Ireland are a real hotbed of engaged citizen science, where
members of the public report their sightings in schemes supported by conservation charities and government bodies," said Professor Brendan
Godley, who leads the Exeter Marine research group.


========================================================================== Story Source: Materials provided by University_of_Exeter. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Zara L. R. Botterell, Rod Penrose, Matthew J. Witt, Brendan
J. Godley.

Long-term insights into marine turtle sightings, strandings and
captures around the UK and Ireland (1910-2018). Journal of the
Marine Biological Association of the United Kingdom, 2020; 1 DOI:
10.1017/S0025315420000843 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201019082904.htm

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