Anadromous: in fish: those species that spend most of their lives at sea but migrate to fresh water to spawn.
Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
Larvae: stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
Spawning: the production or depositing of large quantities of eggs in water.
Cihar, J. (1991) A Field Guide in Colour to Freshwater Fish.Aventium Publishing, Prague.
Davies, C., Shelley, J., Harding, P., McLean, I., Gardiner, R. and Peirson, G. (2004) Freshwater Fishes in Britain – The Species and their Distribution.Harley Books, Colchester.