Rare mackerel species caught in Sligo Bay
28th August 2018
A rare mackerel species has recently been caught in Irish waters. Caught on August 14th by Gerry Sheerin fishing on board Sligo Boat Charters, the Atlantic chub mackerel (Scomber colias) is rarely found this far north, with its normal distribution being near the Mediterranean and further south, off Africa. Whilst the fish is occasionally caught around Irish and UK coasts by both recreational anglers and trawlers alike, it is certainly not common but numbers appear to be increasing in recent years.
Owner of Sligo Boat Charters Daryl Ewing said of the unusual catch, “It’s a first here for me and I’m fishing out of Sligo Bay for over 30 years. I also asked another older charter skipper and a commercial mackerel & scad fisherman from Killybegs but neither have seen one before and both have a couple of decades on me! I had to get the Marine Institute to I.D. it as I was unsure of the species but they confirmed by doing a count of the rays on the dorsal fin that it was a spanish or Atlantic chub mackerel.”
The Atlantic chub mackerel is also confusingly known to some as “Spanish mackerel”, which is the more common name for the much larger and very different looking species Scomberomorus maculatus which tends to live around the Gulf of Mexico. Whilst their colours are similar at a glance, Atlantic chub mackerel differs from our ordinary Atlantic mackerel (Scomber scombrus) in having a larger eye and head, a definite area of large scales around the pectoral region, noticeable dark spots on the flanks and an easily observable swim bladder, which is absent in normal mackerel.
This latest example off Sligo, which is unusually north for the species, was caught on traditional mackerel feathers at a depth of 6-7m down over 22m, at a water temperature of 17°C and was swimming with a shoal of Atlantic mackerel. At a glance the species can appear similar and so it is likely that other examples caught in nets or by rod & line have simply gone unnoticed over the years. The species is usually epipelagic, feeding in deep waters of 250-300m, coming inshore to shallower waters in the summer months and can grow to 2ft long and over 2kg in weight.
The first positive identification of Scomber colias in Irish waters was in August 1967, when two specimens were caught trawling in Dingle Bay and sent for investigation at the then national Fisheries Laboratory in Dublin. Dr. Arthur Went was the prominent Irish fisheries biologist of the time and recorded unusual fish in Irish waters from 1958 onwards. In 1967 remarked that whilst there has been a number of claims of Atlantic chub mackerel in Irish waters before this, including one as far back as 1858 (again off Dingle) none had been reliably identified.
Several other records of Atlantic chub mackerel have been officially verified off the Irish coast. Another specimen was formally identified by Went in 1968, as well as in 1970 and 1976 – all of these fish were caught via trawls in Dingle Bay. In 1993 another specimen was recorded (again, in a trawl) off Kerry Head whilst more recently, in 2003, a single fish was landed off the NW coast of Donegal by boats pair trawling for scad. In 2011 another fish was caught alongside Atlantic mackerel off the SW coast.
Although certainly uncommon in Irish waters, especially off more northern shores, it would appear likely that the occurrence of fish species more typical of southern climes, such as chub mackerel, are set to become more and more frequent due to climate change and shifting ocean currents.
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