11.5.9 Commercial Pelagic Species
11.5.9.1 Herring 94. Herring are common throughout the North Sea (Figure 11.24), occupying depths from the sea surface to 200m. They have a wide distribution in North Atlantic waters and migrate considerable distances in large shoals to feeding and spawning grounds (Munro et al. 1998). Juvenile fish generally remain for up to two years in nursery areas before joining adult fish migrations (ICES, 2010b). The migration of herring is divided into three phases, the over-wintering phase, the feeding phase and the spawning phase (Maurcops, 1969).
95.
The North Sea autumn-spawning herring stock is understood to be a complex of multiple spawning components (sub-populations) (Payne et al. 2010). There are considered to be four major components, each defined by distinct spawning times and sites (Payne et al. 2010). The sub-population relevant to the proposed East Anglia THREE site is the Downs component. The Downs herring spawn during December and January in the eastern English Channel and overwinters in the southern North Sea (ICES 2013). The other three components spawn in the North Sea in August/September (the Orkney–Shetland, the Buchan and the Banks components) (Figure 11.25). The Downs herring move to the central and northern North Sea to feed in the spring (Corten, 2001).
96.
The Downs herring generally spawn in high energy environments on coarse substrates including gravel, sandy gravel, and small stones or rocks (Keltz and Bailey, 2010; Munro et al. 1998; Hodgson, 1957) at depths between 20-40m (Cushing and Burd, 1957; Parrish et al. 1959). Herring spawn benthic eggs in single batches, often several eggs deep (Maitland and Herdson, 2009) forming large mats and clumps that tend to hatch synchronously (Harden Jones, 1968; Burd, 1978; Blaxter and Hunter 1982).
97.
The Downs herring are less fecund than the other three spawning components (i.e. produce fewer eggs). However, the eggs produced by the Downs herring are larger (Baxter 1959; 1963; Cushing, 1958; Almatar and Bailey, 1989) and as a result, the hatched larvae are larger than their northern counterparts (Heath et al. 1997). Herring larvae hatch after approximately three weeks, depending on sea temperature and become planktonic (Craik and Harvey, 1984; 1987; Ying and Craik, 1993). The Downs larvae hatch between 7.5 and 9.5 mm in length (Dickey-Collas,
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
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