Blueline Tilefish: A Profile

by Tom Sanfilippo, Hourly Fisheries Technician
Bureau of Marine Fisheries
October 27, 2017

Common Name: Blueline Tilefish, Grey Tilefish
Scientific Name: Caulolatilus microps

Background: Blueline Tilefish are frequently caught as bycatch by long liners and charter/party boats fishing for Golden Tilefish. Tilefish in general are relied upon on to "save a trip" meaning that the catch of a tilefish by anglers fishing for species like tuna can still make the trip worthwhile, even if the original target species is not biting.

Management: As tilefish are non-migratory, they become very susceptible to the pressures of over fishing. Previously, Blueline Tilefish had no regular federal regulations for fish caught north of Virginia, as the fishery is data deficient in the Mid-Atlantic region. Because of this and the increasing number of catches, an interim fishery management plan was set in place in June 2016 to limit the number of tilefish caught and prevent tilefish from being overfished as data is gathered and the stock is further assessed. The Division of Fish and Wildlife cooperated with the Mid-Atlantic Fishery Management Council to collect gonads and otoliths in hopes of gaining a better understanding of the population, age and reproduction rates of Bluelines off New Jersey's coast.

Biological Characteristics: Blueline Tilefish are dull-olive grey fish gradually turning white moving toward their underside. They lack a fleshy structure behind their head which visually separates them from the popular Golden Tilefish. Blueline Tilefish have a long snout, a narrow gold stripe underlined in fluorescent blue from the snout to the tip of the eye, and a strong flat spine on their gill cover. They also have an elongated, continuous dorsal and anal fin that is roughly half the length of the body. Males tend to be larger than females and can grow up to 32 inches long and live for up to 15 years.

Range: Western Mid-Atlantic Ocean south to Florida; also in northern and eastern Gulf of Mexico

Habitat: Bluelines live in deep water around the continental shelf and upper slope. Their preferred water temperature range is 15°-23°C (59°-73°F) with a depth range from 73 m-238 m (240 ft-780 ft) in a mud and rubble substrate, which allows them to construct and inhabit burrows which they share with other fish such as groupers and snappers.

Food and Feeding: Being a bottom dwelling fish, Blueline Tilefish are opportunistic feeders that prey mainly on benthic invertebrates associated with the substrate in which they inhabit. These invertebrates include portunid crabs, mollusks, polychaete worms, and Brittlestars; however, they occasionally feed on smaller fish.

Spawning: Blueline Tilefish typically begin to spawn at 4-5 years old when they reach 17-18 inches in length for females, and 23.5 inches for males. Spawnning occurs April-October. During this time females can release upwards of 4 million free-floating eggs into the water column. It is speculated that Blueline Tilefish are hermaphroditic, or able to reverse gender.

Migration: Bluelines are not known to migrate, however they will move if the constant deep-water temperature they prefer drops to below their minimum threshold for which they can survive.

References:
The IUCN Red List of Threatened Species: Caulolatilus microps
www.iucnredlist.org/details/190191/0

South Atlantic Fisheries Management Council: Blueline Tilefish
https://safmc.net/regulations/regulations-by-species/blueline-tilefish/

Reproductive Biology of The Blueline Tilefish, Caulolatilus Microps, off North Carolina and South Carolina
https://archive.org/stream/cbarchive_54318_reproductivebiologyoftheblueli1971/reproductivebiologyoftheblueli1971#page/n15/mode/2up

Tilefish, Lopholatilus chamaeleonticeps, Life History and Habitat Characteristics (NOAA)
www.nefsc.noaa.gov/nefsc/publications/tm/tm152/tm152.pdf

A special "Thank You!" to Jeff Gutman, captain of the Voyager, for allowing us onboard to collect data.