Amberjack (Seriola dumerili) and almaco jack (Seriola rivoliana) are circum-tropical species ranging from about 45oN to 30oS.
Amberjack are found throughout the Atlantic, Mediterranean, and Indo-West Pacific whereas almaco jack are distributed in the Indian Ocean, Pacific and western Atlantic. These globally sought-after gamefish species are also known to occasionally venture into northern New Zealand waters during late summer and early autumn.
Although amberjack grow to a maximum size of 190cm and almaco jack are a bit smaller, growing to a maximum size to 160cm, the largest amberjacks described around New Zealand mainland were 50cm and almaco jack were slightly bigger at 65cm. Our own kingfish (Seriola lalandi) – which are a close relative of these jacks – do not reach maturity until they are over 70cm long, so it is likely that all the amber- and almaco jack recorded in New Zealand waters are reproductively immature.
Outside of mainland New Zealand, the closest breeding populations for both jack species are likely in Norfolk Island and eastern Australia. Juveniles of both species associate with drifting debris and so probably disperse into New Zealand by drifting with logs and seaweed.
So how do you know if you’re looking at an amberjack, an almaco jack, or a plain old kingfish? Amberjack are blueish-grey on top and silvery below the lateral line, and there is often a distinct amber stripe along the flanks, hence ‘amberjack’. Almaco jack usually have a brown-olive tinge to the whole body and a dark bar that runs from the eyes back to the start of the dorsal fin. The most distinguishing feature of almaco jack is the tall dorsal fin – it is generally over 1.5 times as tall as the pectoral fin is long. Both jack species are generally deeper-bodied and squatter than our local Kingfish. However, none of these features are especially obvious, and the three species can easily be confused.
We’d like to know more about these jacks arriving in New Zealand – whether they are surviving our winters, and how big they’re getting over here. To help us track these species, it is recommended that any strange looking kingfish or jack species you catch, spear, or see are photographed and the image is sent to WhatsThatFishNZ for a fish taxonomist to identify.
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