page_title: Giant trevally
section_title: Relationship to humans
hierarchical_section_title: Giant trevally / Relationship to humans
caption_attribution_description: English: Scanned photo of 40 cm giant trevally taken by soft plastic lure off Cairns, Australia
context_page_description: The giant trevally, also known as the lowly trevally, barrier trevally, giant kingfish or ulua, is a species of large marine fish classified in the jack family, Carangidae. The giant trevally is distributed throughout the tropical waters of the Indo-Pacific region, with a range stretching from South Africa in the west to Hawaii in the east, including Japan in the north and Australia in the south. Two were documented in the eastern tropical Pacific in the 2010s, but it remains to be seen if the species will become established there.
  The giant trevally is distinguished by its steep head profile, strong tail scutes, and a variety of other more detailed anatomical features. It is normally a silvery colour with occasional dark spots, but males may be black once they mature. It is the largest fish in the genus Caranx, growing to a maximum known size of 170 cm and a weight of 80 kg. The giant trevally inhabits a wide range of marine environments, from estuaries, shallow bays and lagoons as a juvenile to deeper reefs, offshore atolls and large embayments as an adult.
context_section_description: The giant trevally has been used by humans since prehistoric times, with the oldest known records of the capture of this species by Hawaiians, whose culture held the fish in high regard. The ulua, as the fish is known to Hawaiians, was likened to a fine man and strong warrior, which was the cause of a ban on women eating the species in antiquity. The species was often used in Hawaiian religious rites, and took place of a human sacrifice when none was available. Culturally, the fish was seen as a god, and treated as gamefish which commoners could not hunt. There are many mentions of ulua in Hawaiian proverbs, all generally relating to the strength and warrior-like qualities of the fish. The Hawaiians considered the fish to be of excellent quality, with white, firm flesh. Despite this, intrusions of giant trevally into modern-day fishponds used by Hawaiians for rearing fish are unwelcome; being a predator, it eats more than it is worth at market.
  The giant trevally is of high importance to modern fisheries throughout its range, although quantifying the amounts taken is very difficult due to the lack of fishery statistics kept in most of these countries. Hawaii has the best-kept statistics, where the 1998 catch consisted of 10,194 pounds of giant trevally worth around US$12,000. Historically, the species has been taken in far greater numbers, and has been an important food, market and game fish since the early 1900s. However, their exploitation has seen the landings of the species decrease by over 84% since the turn of the century, declining from 725,000 lb to 10,000 lb in recent catches. FAO statistics of the Asian region record catches between 4,000 and 10,000 tonnes between 1997 and 2007, although this excludes most fisheries which are not monitored or do not discriminate between trevally species. The giant trevally is commercially caught by a number of methods, including hook and line, handlines, gill nets and other types of artisanal traps. The species has also successfully been bred for aquaculture purposes in Taiwan. It is sold at market fresh, frozen, salted, and smoked, and as fishmeal and oil.
  The giant trevally is considered one of the top gamefish of the Indo-Pacific region, having outstanding strength, speed and endurance once hooked. It can be taken by many methods, including baits of cut or live fish and squid, as well as a wide array of lures. The species is commonly taken on bibbed plugs, minnows, spoons, jigs and poppers,  soft plastic lures and saltwater flies. In recent years, the development of both jigging and surface-popping techniques has seen the giant trevally become an extremely popular candidate for catch and release fishing, with many charter operators based around this concept. The species is also popular with spearfishermen throughout its range. The species' edibility has been rated from poor to excellent by different authors, although numerous cases of ciguatera poisoning have been reported from the species. Detailed tests on a large (1 m) specimen taken from Palmyra Island showed the toxicity of the fish's flesh, liver and washed intestinal tract produced no or weakly positive symptoms to laboratory mice, but the digested contents of the intestine were lethal. The authors argued, based on this test, the flesh of giant trevally was safe to consume. However, analysis of case studies in which ciguatera poisoning was reported after eating the fish suggested an accumulative effect occurs with repeated consumption; and tests like the one outlined above are not reliable, as the toxin appears to be distributed haphazardly throughout each fish. Since 1990, giant trevally taken from the main Hawaiian islands have been blocked from sale by auction internationally due to concerns over liability from ciguatera poisoning.
caption: A giant trevally taken by a soft plastic lure
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