11.5.12 Diadromous Migratory Species
11.5.12.1 River and Sea Lamprey 167. River lamprey and sea lamprey are parasitic anadromous migratory species. Their distribution around the British Isles is shown in Figure 11.9. Sea lamprey were recorded in low numbers in IBTS surveys in the vicinity of East Anglia THREE (Table 11.5). Records of river and sea lamprey in East Anglian rivers are relatively scarce compared with other areas of the UK.
168. Both species spawn in fresh water in spring or early summer, followed by a larval phase (ammocoetes) spent in suitable silt beds in streams and rivers before migration to the sea, to feed (Laughton and Burns, 2003).
169. Ammocoetes can spend several years in freshwater on silt beds, feeding on organic detritus and eventually transforming into adults from late summer onwards (Laughton and Burns, 2003). The transformation into the adult stage is characterised by the development of functional eyes and the mouth changes into a fully formed sucker (Maitland, 2003a). After transformation, river and sea lampreys migrate to sea, where they use their suckers to attach to other fish (Maitland, 2003a).
170. River lampreys generally inhabit coastal waters, estuaries and accessible rivers feeding on a variety of fish including young herring, sprat and flounder. After one to two years in an estuarine environment, river lampreys cease feeding in the autumn and move upstream between October and December (Maitland, 2003a). After several years in the marine environment the adults return to fresh water to spawn (Laughton and Burns, 2003).
171. Sea lamprey are recorded most in estuarine and inshore waters, with low abundance (Maitland and Herdson, 2009) and in the open sea with attachment to host species including basking shark and occasionally sperm whale (Maitland and Herdson, 2009). Their distribution is largely dictated by their hosts (Waldman et al. 2008) and adults are parastitic on a variety of marine mammals and fish, including herring, salmon, cod, haddock and sea bass (Kelly and King, 2001; ter Hofstede et al. 2008). Homing behaviour is not apparent in this species (Waldman et al. 2008) and unlike salmonids and shads, lampreys do not have specific river populations (ter Hofstede et al. 2008). The rarity of capture in coastal and estuarine waters suggests that marine lampreys are solitary feeders and widely dispersed at sea. It is possible that sea lamprey often
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
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