Blueline Tilefish

Blueline Tilefish, Caulolatilus microps

The Blueline Tilefish, Caulolatilus microps, whose common Spanish name is blanquillo lucio, is a member of the Tilefish or Malacanthidae Family, known collectively as blanquillos in Mexico. This fish is also known as the Gray Tilefish. Globally, there are ten species in the genus Caulolatilus, seven of which are found in Mexican waters, five in the Atlantic and two in the Pacific.

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 two spines and 21 to 24 rays; their caudal fin is straight to slightly concave; and their dorsal fin has 7 or 8 spines and 24 to 27 rays. Both anal and dorsal fins have very long bases. They have 21 to 27 gill rakers. Their body is covered with rough scales.

The Blueline Tilefish are found demersal in moderately deep waters at depths between 100 and 750 feet over muddy and sandy bottoms on the outer continental shelf, shelf break, and upper slope. They reach a maximum length of 90 cm (35 inches) and weight of 9 kg (20 pounds) with males being larger than females. 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, vermillion 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 4.1 million eggs annually which are fertilized externally and become pelagic. They have a lifespan of up to thirty years.

In Mexican waters the Blueline Tilefish 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 Yucátan Peninsula.

The Blueline Tilefish is straightforward to identify and cannot be confused with any other tilefish, as these all 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.

The Blueline Tilefish 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.

Blueline Tilefish, Caulolatilus microps. Fish caught from coastal waters off Islamorada, Florida, April 2012. Length: 61 cm (24 inches). Catch, photo, and identification courtesy of George Brinkman, Guelph, Ontario, Canada.

Blueline Tilefish, Caulolatilus microps. Fish caught from waters off Pulley Ridge in the Caribbean, August 2014. Length: 69 cm (27 inches). Weight 4.0 kg (8.8 pounds). Catch, photo, and identification courtesy of George Brinkman, Guelph, Ontario, Canada.