Common names:  rattails, grenadiers

Distribution:  Depths from 200 to 6000 meters (bathyal to abyssal) throughout the world’s oceans. The majority of species are benthopelagic, swimming in the water column just over the sea floor. Some specimens have been captured as much as 1000 meters off the bottom in the abyssopelagic zone. At least two genera of macrourids are entirely bathypelagic.

General description and features:  Macrourids are the most common and abundant family of benthic deep-sea fishes. They generally are large (~.5 - 2kg) and have large heads and mouths and long tapering tails. The latter feature gives them the common name "rattail." Most macrourids are a dull brown or gray color, sometimes black.  

Macrourids have large eyes, a well developed lateralis systems (likely enhanced by their long bodies) and a suite of chemoreceptors on the head, lips, and barbel under the chin.  

With the exception of bathypelagic species macrourids have gasbladders to aid their benthopelagic lifestyle.

Feeding:  Studies of the diet and feeding habits of macrourids suggest that most species are generalist predators feeding on a variety of epifaunal megafauna and small benthopelagic crustaceans. Several macrourids are also scavengers, as documented by their attraction to baited cameras and the presence of carrion in their stomachs. Considering their large size, abundance, and general feeding habits macrourids are important apex predators in the deep-sea environment.

Reproduction and life history:  Many macrourids have special strumming muscles attached to their gasbladders. It is thought that these may aid in mate location or attraction in their dark habitat.  

Macrourids produce large numbers (>100,000) of ~1-2mm eggs. The eggs have a large lipid droplet making them bouyant and they rise towards the surface. The larvae hatch out near the permanent thermocline and then slowly descend towards the seafloor as they develop. Macrourid larvae are relatively rare and the early life history of macrourids remains largely hypothetical.

Young macrourids are typically found at the shallower end of the depth distribution for a species and move progressively deeper as they mature. Both aseasonal and seasonal reproduction have been noted in macrourids and one species, Coryphaenoides armatus, may even be semelparous (dies after spawning).