PACIFIC RATTAIL

PACIFIC RATTAIL

LIFE HISTORY

Adult Stage:

Adults are demersal and occur mainly all along the west coast at depths from 155 to 2470 m, and are often associated with sandy bottoms of the abyssal plains.

Composites: non-rocky shelf, continental slope/basin

Spawning Stage:

Spawning may occur year round, likely within the adult habitat.

Composites: non-rocky shelf, continental slope/basin

Juvenile Stage:

Juveniles are demersal and likely occur within the adult habitat.

Composites: non-rocky shelf, continental slope/basin

Larval Stage:

Larvae are pelagic and usually occur in the upper 200 m of the water column over the continental slope/basin.

Composites: oceanic

Egg Stage:

Insufficient information.

Range

Pacific rattails (also known as Pacific grenadiers) are found in the northeast Pacific from the Bering Sea off Alaska to Baja California [114].

Fishery

A commercial fishery is developing for rattails and they are marketed primarily as grenadiers. Most catches are made with trawl gear, but hook and line (longline) is also effective [140]. Incidental catches of rattails in deepwater trawl fisheries are often used in livestock feeds [220].

Habitat

Rattails are among the most abundant fishes of the continental slope and abyssal waters worldwide [220]. They are found at depths from 155 to 2,470 m, most commonly below 1500 m in the Northeast Pacific Ocean [114, 354].

Spawning depth is not known [140]. Stein [353] noted that larval stages of the Pacific rattail have been captured in the water column in waters less than 200 m whereas older larvae and juveniles occur deeper. Newly metamorphosed fish off Oregon settle out of the water column in 500 m or less [353]. As they grow, juveniles move to deeper water [141].

Pacific rattails occur in highest densities on the sandy bottoms of the abyssal plains of the northeast Pacific [354], but specific habitat associations for any life history stage have not been studied.

Migrations and Movements

Migrations have not been documented and it is assumed that this is a relatively sedentary species [285]. Iwamoto and Stein [141] did note that larger fish are found in deeper water, suggesting a movement to deep water with increasing size.

Reproduction

Pacific rattails are oviparous and fertilization is external [353]. Stein and Pearcy [354] and Matsui, et al., [220] collected ripe females in September, October, and April, and they implied the possibility of two spawning seasons per year. Off southern California, spawning occurs mostly from late winter to early spring, although spent females are found throughout the year [140]. Fecundity has been estimated to be between 22,657 and 118,612 eggs per female [220, 354] and as much as 150,000 eggs in a large female off California [140].

Growth and Development

Fertilized eggs are about 2.0 mm in diameter [353]. Larvae hatch at about 2 mm total length and are pelagic, occurring in the upper 200 m of the water column [353]. Metamorphosis occurs at about 10 mm total length [353, 354]. Female rattails mature at about 650 mm total length; males mature as small as 480 mm total length. Female rattails grow faster and reach a larger average size than do male rattails [220]. Maturity is reached in about 10 years or more, based on estimated size at maturity [140].

Trophic Interactions

Stomach contents of rattail fishes are usually evacuated between capture and retrieval of the fish, so analysis of stomach contents is difficult. Pearcy and Ambler [281] found stomachs to contain the remnants of cephalopods, other demersal fishes (often other macrourids) and sinking food particles of dead nekton. The food and feeding of larvae and juveniles is not known [285].

Rattails are, in turn, likely preyed upon by other demersal fishes, including other macrourids. Stein [353] noted that cannibalism is not uncommon, and may be responsible for high larval and juvenile mortality.

PACIFIC RATTAIL

SUMMARY TABLE