The alfonsino ( Beryx decadactylus), also known as the alfonsin, longfinned beryx, red bream, or imperador, is a species of deepwater Berycidae fish of the order Beryciformes. It can be found in temperate and subtropical ocean waters nearly worldwide, though it is uncommon. It is typically associated with deep-sea , and schools are known to form over seamounts. Adults are demersal and search for prey along the ocean floor, primarily fish, , and . Like other members of its family, it is remarkably long-lived, with individuals reaching ages of up to 69 years, and possibly longer. It can reach sizes of up to in length and in weight and is targeted by commercial fisheries. Its low reproductive rate and the time it takes for juveniles to mature make it vulnerable to expanding deep-sea fisheries, but it is listed as Least Concern by the International Union for Conservation of Nature (IUCN) due to its extensive range.
With an extensive depth range below the surface, the alfonsino occurs in localized aggregations over deep-sea coral habitats on the continental shelf and continental slope. By day it stays in deeper water and vertically migrates to shallower waters at night. It is most commonly found deep in waters around in temperature, however depth range varies by region. In the eastern Atlantic its depth range is , while in the western Atlantic its depth range is , common depth range . Its depth range is largest in the Indo-Pacific, where it is found as deep as in the waters off of Australia, New Zealand, New Caledonia, La Reunion Island, Mauritius, Madagascar, Comoros, Seychelles, Korea, Japan, New Guinea, the Ryukyu Islands, and Hawaii.
Spawning occurs in the summer months, June through September, though males can reproduce year-round. Alfonsinos are batch spawners, that is they release eggs multiple times over an extended spawning season rather in a short period. Eggs and larvae are epipelagic, staying near the ocean's surface. Eggs hatch after around 27 hours and larvae are initially Fish measurement in size, identifiable by pigment near the brain. Flexion, when the larva bends upwards prior to development of the caudal fin, occurs at SL. Fin rays and scales are fully formed by SL. They are distinguished by elongated pelvic rays and anterior dorsal spines as well as pigment near the gas bladder, though they are very similar to the larvae of the splendid alfonsino. Juveniles live deeper, but are still pelagic for a few months, eventually moving to their demersal habitat where they will live as adults. After 4 years, they reach sexual maturity, at which point they will be about in size, with females being slightly larger on average than males. Individuals grow slowly, as is common among members of Berycidae. Although their maximum age is unknown, individuals have been caught at 69 years old. Their actual maximum age is unknown, however, with estimates ranging as high as 85 years.
Despite being widespread throughout its range, the alfonsino is an uncommon fish in many areas, likely due to exploitation by commercial fisheries and depletion due to bycatch. It is listed as Least Concern by the International Union for Conservation of Nature (IUCN) because its extensive distribution protects it from danger of extinction and in parts of its range it is not a targeted species. It could also be threatened by habitat loss due to deep-water trawling causing damage to deep-sea corals.
Biology and ecology
Human interaction
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