New measures to protect common seals around Scotland have come into force.
No single factor is thought to have caused the drop in seal numbers
The Conservation of Seals (Scotland) Order 2007 brings in a year-round close season for areas where there has been a 40% drop in seal numbers.
This includes Shetland, Orkney and an area of the east coast between Stonehaven and Dunbar.
The shooting of common seals will only be possible with a licence from the Scottish Executive or under the terms of the "netsmen's defence".
This defence protects fishing nets or catches.
The Scottish Executive said it was unlikely that any single factor was responsible for the reduction in numbers.
There is no evidence it is a direct result of the phocine distemper virus outbreak among seals in 2002, as no large numbers of carcasses were reported at that time.
The executive said it was also unlikely to be a direct result of shooting alone for similar reasons. It is also unclear whether this reduction is a short-term or longer-term phenomenon.
The executive, Scottish Natural Heritage and Sea Mammal Research Unit will monitor the effectiveness of the new order and consider research into the possible causes of the decline in common seal numbers.