UK Seals Suffering Massive Decline
Marine Biologists have disturbingly discovered that some of the UK’s harbour seal Phoca vitulina vitulina populations have and are undergoing ‘massive’ declines. The results are particularly concerning given that scientists are as yet, unable to account for exactly why these declines are occurring at their present rate.
Ian Boyd, a professor with the sea mammals research unit at St Andrew’s University said:
“This is very abnormal. To give you an idea of the level of abnormality, the rates of decline are equivalent to these populations producing no offspring for five or six years.”
The declines coincide with reports that other groups in these areas (Orkney islands and East England) such as sea birds are undergoing similarly rapid declines. Last month scientists at the University of Stockholm reported that their ‘junk food hypothesis‘ could offer some explanation to the declines. The theory goes, that as key prey populations in the North Sea such as cod Gadus morhua have depleted to near extinction, fish such as sprat Sprattus sprattus have grown considerably in abundance, replacing the cod’s ecological niche. However despite their abundance, they lack the nutritional value of cod leading to leaner seabirds and lower survival rates in young.
Other theories researchers have put forward include an increasing range overlap with gray seals Halichoerus grypus resulting in greater competition, direct persecution at fishing grounds by shooting, and a greater reported abundance of killer whales around Orkney and the North sea, leading to increased mortality of seal pups.
The report comes at a time when Scotland is consulting on a Scottish Marine Bill. Conservationists have called for the abolishment of the Seal Conservation Act that permits seal shooting near fisheries, and for protection under the existing Wildlife & Countryside Act.
Since top predators such as seals are sensitive to perturbations in community dynamics, the declining trend seen in many of their British populations should be a considerable cause for concern. Continued monitoring will provide a better understanding of whether this is a natural fluctuation in their population dynamics or a more concerning trend.
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