Blueline Tilefish, Caulolatilus microps

Blueline Tilefish, Caulolatilus microps. Fish caught from coastal waters off Ft. Lauderdale, Florida, August 2021. Length: 34 cm (13 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.

Blueline Tilefish, Caulolatilus microps. Fish caught from coastal waters off Broward County, Florida, August 2021. Length: 34 cm (13 inches). Catch, photograph and identification courtesy of Ben Cantrell, Sebastian, Florida.

Blueline Tilefish, Caulolatilus microps. Fish caught from coastal waters off Point Pleasant Beach, New Jersey, August 2018. Length: 58 cm (23 inches). Catch, photograph, and identification courtesy of Kenneth Tse, Toronto, Ontario, Canada.

Blueline Tilefish, Caulolatilus microps. Fish caught from coastal waters off Islamorada, Florida, April 2012. Length: 61 cm (2 feet 0 inches). Catch, photograph, and identification courtesy of George Brinkman, Guelph, Ontario, Canada.

Blueline Tilefish, Caulolatilus microps. Fish caught from waters off Pulley Ridge, 100 miles west of the Tortugas Ecological Reserve, Florida Keys, August 2014. Length: 69 cm (2 feet 3 inches). Weight 4.0 kg (8.8 lbs). Catch, photograph, and identification courtesy of George Brinkman, Guelph, Ontario, Canada.

The Blueline Tilefish, Caulolatilus microps, is a member of the Tilefish or Malacanthidae Family, that is also known as the Gray Tilefish and in Mexico as blanquillo lucio. Globally, there are ten species in the genus Caulolatilus, of which seven are found in Mexican waters, five in the Atlantic and two in the Pacific Ocean.

The Blueline Tilefish have robust rectangular shaped bodies with a uniform depth throughout their length that is 25 to 30% of standard length. They are gray-brown with a black ridge along their nape, a turquoise snout, and a narrow gold stripe under their eyes. They also have a broad oblique bar that runs from under the rear edge of their eye to the center of their mouth. Their gill covers are yellow. Their anal fin is white with a central dark stripe; their caudal fin has several vertical rows of yellow spots; and their dorsal fin has gray membranes, indistinct yellow areas, and a wide yellow margin. They have a relatively deep head with a steep rounded profile, small eyes, a small terminal mouth that does not reach the eyes, and serrated gill covers with a short blunt spine. Their anal fin has 2 spines and 21 to 24 rays and a long base; their caudal fin is straight to slightly concave; and their dorsal fin has 7 or 8 spines and 24 to 27 rays and a long base. They have 21 to 27 gill rakers. Their body is covered with rough scales.

The Blueline Tilefish is found demersal in moderately deep waters at depths between 30 m (100 feet) and 230 m (750) feet over muddy and sandy bottoms on the outer continental shelf, shelf break, and upper slope. They reach a maximum of 90 cm (2 feet 11 inches) in length and 9 kg (20 lbs) in weight, with males being larger than females. As of January 1, 2024, the International Game Fish Association world record stood at 10.55 kg (24 lbs 4 oz) with the fish caught in coastal waters off Lindenkohl Canyon, New Jersey in May 2015. They inhabit burrows and are generally non-migratory making them sitting ducks for commercial fishermen. They co-mingle with Atlantic Golden-eyed Tilefish, Blackline Tilefish, Great Northern Tilefish, Red Porgy, Silk Snapper, Snowy Grouper, Vermilion Snapper, and Warsaw Grouper. They are opportunistic predators that consume fish and invertebrates found in the substrate. They are aggregating spawners with females significantly outnumbering males indicative that they are protogynous hermaphrodites and change from female to male at midlife. Females release between 210,000 and 4,100,000 eggs annually which are fertilized externally and become pelagic. They have lifespans of up to thirty years. The Blueline Tilefish is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.

The Blueline Tilefish is a resident of Mexican waters of the Atlantic Ocean but have a limited distribution being found only along the coast of the Texas–Mexico border in the Gulf of Mexico and off the northwestern continental shelf of the Yucatán Peninsula in the Gulf of Mexico.

The Blueline Tilefish is straightforward to identify and cannot be confused with any other tilefish, as all other tilefishes have a large mouth that reaches at least the anterior margin of the eyes and a dark spot above the pectoral fin axil. The Blackline Tilefish, Caulolatilus cyanops, is a possible exception, as it has blue stripes under its eyes but distinct markings on its dorsal fin.

From a conservation perspective the Blueline Tilefish is currently considered to be Data Deficient. They are caught at a significant level by commercial fishermen as a by-catch of the Red Grouper and Yellowedge Grouper fisheries in Mexico using hook and line and longlines. Annual catch rates are estimated to be approximately 180,000 tons. Catch levels are poorly documented and confusion occurs because other large fish are taken from the same general areas. They are uncommon in Mexican fish markets. They are also caught at good levels by recreational anglers. They are the predominant catch in deepwaters off the southeastern United States. They are prone to overfishing in some locations as Tilefish are not specifically protected to any great extent by current regulations.