A recent publication shows us that, for the first time, pictures have been taken of an extremely rare adult hypo pigmented (leucistic) harbour porpoise in the northern North Sea. Leucism is the complete loss of pigment production in the body unlike albinism which is the loss of Melanin. The rarity of this harbour porpoise is such that only 7 individuals have been recorded in the last 100 years. The adult status of the individual is also cause for interest as abnormally pigmented animals in the wild are often at a disadvantage compared too regularly coloured individuals. Of the 7 white porpoise seen in UK waters 6 have been adults which indicates that these rather conspicuous individuals can survive for long period of time despite a natural disadvantage.

Anomalously white harbour porpoise (Phocoena phocoena) photographed in the Moray Firth on 24 August 2012. The head, back, sides and pectoral fins appear uniformly pinkish white against a contrastingly darker grey/black dorsal fin (photographs: Kevin Robinson, Robinson and Haskins 2013).
References
Robinson K.P. And Haskins G.N. (2013) Rare sighting of an anomalously white Harbour porpoise (Phocoena phocoena) in the Moray Firth, north-east Scotland. Marine Biological Association of the United Kingdom, 6, E23.
By John Ball