Life History
Orange roughy are generally sluggish and demersal; they form aggregations with a natural population density of up to 2.5 fish per square meter, now reduced to about 1 per square meter. These aggregations form in and around geologic structures, such as undersea canyons and seamounts, where water movement and mixing is high—ensuring dense prey concentrations. The aggregations are not necessarily for spawning or feeding; it is thought that the fish cycle through metabolic phases (active or feeding and inactive or resting) and seek areas with ideal hydrologic conditions to congregate during each phase. They lose almost all pigmentation while inactive, during which time they are very approachable. Predators include large deep-roving sharks, cutthroat eels, merluccid hakes, and snake mackerels.
When active, they feed primarily on zooplankton such as mysid shrimp, euphausiids, mesopelagic and benthopelagic fish, amphipods, and other crustaceans; adults also take smaller fish and squid. The orange roughy's metabolic phases are thought to be related to seasonal variations in prey concentrations. The inactive phase conserves energy during lean periods. Orange roughy can live up to 149 years.
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