
(This Nov. 13 story has been corrected to show sea is overall 1.2C warmer than 30 years ago, not 0.4C, in 18th paragraph)
KERKENNAH ISLANDS, Tunisia (Reuters) - A decade ago, Tunisian fisherman Ahmed Chelli's nets bulged with fish and octopus that he sold at the local market in the Kerkennah islands. Today, he pulls up only "ISIS" — the name locals have given to the blue crabs that have invaded their fishing grounds in the fast-warming waters of the Mediterranean.