Fish Facts

Fish Facts: Spanish mackerel revisited

SPANISH mackerel (Scomberomorus commersonii) are the largest of the mackerel species encountered by anglers fishing the northern half of the country, growing to around 2.4 metres long and in excess of 60kg.

These exciting sportfish can be encountered from as far south as Geographe Bay in WA, along our northern coastline and down the whole of the east coast of the mainland, even as far south as the north east coast of Tasmania during the summer months. Throughout this range Spaniards can be found from the very edge of the continental shelf in areas such as the Great Barrier Reef, to quite shallow turbid waters such as off the islands and headlands in the Northern Territory.

Spaniards are widely distributed throughout the West Pacific and Indian Oceans, as far north as Japan and even in the eastern Mediterranean Sea (which they entered via the Suez Canal). Until very recently, scientists thought that there was only one species of Spanish mackerel throughout their entire range, basing this on the fact that tagged fish sometimes travelled long distances, suggesting mixing between populations of fish in different regions. However, French scientists recently found large genetic differences between fish from the Persian Gulf, Asia and the south Pacific (including Australia), such that there may in fact be two or more species, with further genetic differences within each of these three main regions.

This might be explained by the fact that some schools of Spanish mackerel are known to establish permanent resident populations in particularly favourable spots such as drop-offs and points which jut out into strong currents. A lack of intermixing between these separate resident populations could explain some of the genetic results. The existence of a population of occasionally “toothless” Spanish mackerel in a particular region off Malaysia (yes, mackerel with no teeth) also suggests that resident populations of spanish mackerel exist throughout their range.

Spaniards are a handsome fish with a long, streamlined silvery body broken up by a number of narrow transverse wavy lines (which lead to the name narrow barred Spanish mackerel). They have a turn of speed which few fish can match, and can hit lures avidly, sometimes leaping over 2 meters into the air as they attempt to take a rapidly trolled or retrieved surface lure. Their scissor like teeth are lethally sharp and must be given the utmost respect when handling these fish, alive or dead.

On the plate they are great eating when fresh, but in some parts of their range (e.g. Platypus Bay inside of Fraser Island in Queensland) extreme caution must be observed when eating large specimens, which accumulate ciguatoxin probably due to eating a diet of bottom dwelling algae eating fishes. Large spaniards tend to eat a wide variety of pelagic and bottom dwelling fishes which the other smaller mackerels do not, which may be why spotty and school mackerel captured from the same areas as ciguatoxic Spanish mackerel are generally OK to eat.

On the Great Barrier Reef the main spawning season for Spanish mackerel occurs from October to December. They are fast growing species which reach over 40 cm in the first year. Around 50 per cent of spaniards are mature at two years of age and around 80cm long. Growth rates of individual fish appear highly variable. In one study the largest spaniard collected was a 180cm, 10 year old female weighing 48kg, while the oldest fish was another female of 17 years that weighed only 23 kg. Male spaniards are generally considerably smaller than female fish of the same age, seldom exceeding 140cm and 20kg.

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