Fish Species of the Month: Atlantic Herring

Atlantic Herring
Clupea harengus

Family: Clupeidae (Herrings, shads, sardines, menhadens)
Order: Clupeiformes
Class: Actinopterygii (ray-finned fishes)

Description: A small commercially important shoaling fish that reaches a maximum size of 45.0 cm. The herring is predominantly silver in colour with a blue or blue/green tinge along its back and a single dorsal fin located halfway along its length. The head is scaleless and bony in appearance with a lower jaw that extends beyond the top jaw and an eye, large in comparison to its head, positioned 3 quarters along the length of its mouth.

Similar species: Sprat (Sprattus sprattus). The juvenile herring and sprat can be extremely difficult to distinguish between using the naked eye. The dorsal fin of the herring is set slightly in front of the start of the pelvic fins while the sprat's is located just behind. The sprat has a strong serrated line of scales on the keel of its belly and these are often used to distinguish between the two species by running a finger along the length.

Biology: A pelagic species, the herring migrates between feeding and spawning grounds, with the timing often dependent on distinct races and geographical area. The herring feeds visually taking planktonic copepods from the water column. Depth can range between 0-200 m and the vertical distribution is often dependent on light, with movement from deeper to shallow water from day to night. Schooling in large shoals, herring have been known to turn the water dark in appearance due to density and number.

Facts: The herring family is one of the most important food fishes world wide. North Sea herring stocks were severely overfished during the 1970s and commercial fishing was banned and did not reopen until 1983. The stocks have since recovered and have provided landings of over 300,000 tonne in recent years.

The Thames Estuary herring are members of a spring-spawning coastal race which inhabits a number of localities in European waters, the individual stocks being usually rather small. The fish are smaller in size than the Atlantic herring with on average one less vertebra. The larvae of the year tend to appear within the Thames in most abundant numbers during early summer. The main spawning grounds are around Stud Hill off the Kent Coast and Eagle Bank off the Essex Coast. Large shoals of mature fish venture into the estuary during winter months.

Herring are commercially fished using driftnets and mid-water trawls.Trawling for herrings is prohibited in the northern outer sections of the Thames estuary where the drift net only fishery is certificated by the Marine Stewardship Council.