Lewis is a global nursery hotspot for Risso’s dolphins
WATERS around the island of Lewis have been revealed as a “globally important” nursery for baby dolphins.
A new scientific paper is calling for more protection for a population of Risso’s dolphins living in a “hotspot” around Lewis.
It has been published ahead of a Scottish Government public consultation on making the site a marine reserve and three other proposed protected sea areas.
The paper, produced by Whale and Dolphin Conservation and published in the Journal of the Marine Biological Association of the UK, reveals for the first time that individual Risso’s dolphins are returning to the same spots in one of the proposed sites off east Lewis each year and have been for at least 12 years.
This is the longest site fidelity evidenced in UK waters for the species.
Risso’s dolphins are vulnerable to noise pollution, and this particular site – being considered in terms of protection for marine wildlife – lies within one of two UK military exercise areas.
The report said: “Octopus are likely to be a primary source of food for Risso’s dolphins, so activities in the area that might affect their prey, such as scallop dredging, which ploughs the seabed where the octopus are protecting their eggs and feeding, might be expected to affect the dolphins too.
“As no data has been collected on this to-date, it is hoped that protecting the area will enable the government to prioritise data collection on this.”
The charity says the Lewis site is unique.
Nicola Hodgins, WDC policy manager and one of the paper’s authors, said: “Our research highlights a unique discovery and a very significant reason for this particular proposed site to be officially made a protected area.
“It is the only known location in Scotland that Risso’s dolphins rely on to feed and bring their calves and return to again and again, month after month and year after year.”
The high sightings rate of calves in the persistent hotspot for Risso’s dolphins was identified using data since 2010 in the area, with dolphin sightings occurring year-round, and peak numbers recorded between May and October.
The 117 individual dolphins were catalogued from 2010-2017 in the waters around east Lewis. Calves, including new-borns, were recorded in more than a third of encounters, one of the highest rates in the world.