Mackeral: Scomber scornbrus
Streamlined, iridescent, fast, and strong, the mackerel (Scomber scornbrus) is among the most beautiful fish in the sea and,weight for weight, the hardest fighting. Unfortunately, it reaches an average size of no more than a pound, so only ruthlessly scaled-down tackle will do it justice. It shoals in vast numbers and few parts of the British coast are not visited by it at some time in the summer or autumn. It provides generous sport for many anglers, sport that is generally under-valued because the fish are available in such quantity. It is closely related to the tunny.
Identification problems should not arise. Occasional variations occur in colouration, producing the so-called ‘spotted’ and `scribbled’ varieties, but these are merely varieties, not separate species, in the eyes of the ichthyologist. Scad, sometimes called horse mackerel, are different in body structure and colour. Very rarely a bonito may turn up in a catch of mackerel, especially in coastal areas of the Celtic sea, where a number of occurrences have been noted. This fish (the ‘plain’ bonito) is larger than our mackerel and rather more stoutly built, and largely lacks the typical marblings that are so characteristic of the native species.
It seems fairly certain that the little `Joey’, or harvest mackerel, is a fish in its first year, attaining a length of 17 or 20 cm (7 or 8 ins). The great majority of mackerel taken around our shores are in their second year or older, and average slightly more than a foot long. Most of the growth seems to take place in the first two years, so that G. A. Steven (who investigated the habits of mackerel in the Channel and in the Celtic Sea) writes of a thirty-year-old fish that reached 46 cm (18-1/2 ins) in length and weighed 1.2 kg (21 lb). There is a class of mackerel, however, not very numerous but certainly present in our seas, that may attain a weight of 2 kg (4 lb) or more, so that it seems likely that some factor of which we are not yet aware may enter into the life history of these exceptional fish, of which more will be said later.
The October storms usually see the last of the mackerel, which then leave for deeper water. Recent research has shown that they make for certain quite precise locations that may be separated from each other by many miles; the Hurd Deep, for example, north of the Channel Isles, and the area of the Smalls, off west Wales. In these depths they winter, huddled together in great numbers, feeding very little because there is little for them to feed on. The first fish leave the winter quarters in January, beginning a migration that will end with the spawning period, which reaches its peak in April but may be prolonged into June. Mackerel from the southern and western coasts of Britain and Ireland concentrate in vast numbers on the 100-fathom line of the so-called Celtic Sea (the portion of the Atlantic adjacent to Wales, south Ireland, Cornwall, and Brittany) for spawning.
Once spawning is over, the shoals make for the littoral shallows. Until this happens they have fed chiefly on plankton. But from this point on fish play a larger and larger part in their diet. According to Dr Kennedy, rockling fry preoccupy them at first. Then, as they move inshore, larger fish — sand-eels, sprat, the fry of species like herring and pilchards — become their staple diet.
Once they are inshore, mackerel become roving fish. The shoals may be found almost anywhere. They will enter harbours, especially in the evening: they will shoal on beaches within casting distance of the sands; they will suddenly rip through placid water near rocks in search of food fish. Mackerel can turn up almost anywhere without warning, churning up two hectares of sea or more as they break surface in pursuit of fry, and many an angler who has been bottom fishing from the rocks for other species has cursed his luck for being withoutgear when they arrive.