Trachurus Trachurus (Maasbanker)
Colour, Shape and Size
T he Mackerel is an elongate fish that is almost round in cross-section. The overall body colour is silver, but olive-green to grey above and white below. Darker, vertical bars may be visible on the flanks and there is always a distinct black spot on the gill covers. The fins are translucent or dusky. Can attain
70cm.
External Anatomy
The body is covered with about 75 series of scales arranged along the lateral line. The scales of 40 of these series are sharply spiked. He double dorsal fin comprises one forward plus eight normal spines, which are followed by one spine plus 30-36 rays. The anal fin consists of
two detached spines plus one spine followed by 24-32 rays. The caudal fin is deeply forked. Bands of minute, villiform teeth occur in both the upper and lower jaws. Some 50 elongate rakers occur on the first gill arch. The large eyes are extensively covered with adipose tissue.
Natural History
The Mackerel is a pelagic shoaling species of cooler coastal waters and
ranges from the surface to depths of 400m. Considerable vertical movement has been recorded, however, with shoals rising to feed in surface waters at night and conversely moving downwards to spend the daylight hours near the bottom. The diet consists of krill, mysids and amphipods, most of which are filtered from the water by the elaborate gill rakers. Dolphins, Tuna and Sea birds prey extensively on this species. Sexual maturity is attained at the age
of three years at an equivalent total length of about 20cm. Spawning occurs from late winter to spring and the young are widely distributed by ocean currents. Its possible that the fry of Mackerel like the young of the closely related North Sea Mackerel, shelter below very large jellyfish during their first few months. Presumably these young fish are immune to the stinging cells of the jellyfish.
Capture
The Mackerel is of considerable commercial importance in Southern Africa. Most catches are made in bottom trawls during daylight and much of it as a bycatch. While catches have declined in recent years, the Mackerel may yet prove to be under exploited. Anglers catch this fish from ski-boats and consider it an excellent bait for the larger gamefish. The Mackerel is also value as bait in the rock lobster industry.
Specific Catch Restrictions
Commercial catches are subject to quota.
