The triggerfishes belong to the Balistidae family, which includes about 40 species in 11 genera. They inhabit subtropical and tropical seas worldwide and generally live on reefs and feed on benthic invertebrates, small fish and sometimes algae. Many species play an important ecological role in controlling sea urchins and other benthic invertebrate populations and some are valuable and delicious food fish (queen triggerfish, grey triggerfish).

Like most triggerfish, queen triggerfish (left) and grey triggerfish (right) are nest builders. Spawn size for both species exceeds 100,000 eggs. The parents defend the nest vigorously until the embryos hatch in the evening, the day after spawning.

Triggerfishes live singly, as pairs, in small groups or in schools. They are demersal spawners and are typically highly territorial during courtship and spawning. Many species build nests, some scatter their eggs and most aggressively defend their spawns. Spawning generally takes place in the early morning, with the spawn size ranging from thousands to millions of eggs, depending on the species. The demersal eggs are small (0.45 to 0.65 mm, depending on the species), spherical, and adhesive and contain multiple oil droplets. Embryos hatch in the evening.

Numerous triggerfish species make hardy, bold and beautiful aquarium fishes and have a high commercial value for the trade. Unfortunately, their aggressive tendencies, especially for the larger species, can be downside in captivity.

Left: Clown triggerfish, a popular and expensive aquarium addition. Right: Niger triggerfish juvenile. Aquarists prefer juveniles to the more aggressive and expensive adults.

Most commercially farmed marine aquarium fish larvae, like clownfishes and dottyabcks, are raised using rotifers from when they first start to feed. Reef fish families that produce smaller and more primitive larvae, such as angelfishes and snappers, require the size and the nutritional qualities of copepod nauplii to survive through first feeding. Using local copepods to successfully rear numerous Centropyge species for nearly a decade led us to believe that most reef fishes could be cultured using this live food.

Left: Copepod nauplii (Oithona sp.), 75 μm TL, a favorite of first-feeding Centropyge larvae Right: Tintinnid, 50 μm TL, can be preyed on by triggerfish and wrasse larvae

We were mistaken. We found several wrasse and triggerfish species (including X. mento) that require smaller foods than copepod nauplii (found in coastal Hawaiian waters). The small mouth size, throat size or limited hunting ability of these larvae restricts them to live feeds less than 60 microns in size at first feeding. Many reef fish species may fall in this category and we spent the past year in search of nutritionally adequate food organisms for their larvae.

Left: Picasso triggerfish adult female Right: Picasso triggerfish larva, 3.1 mm TL, with full gut, 17 dph. The Picasso triggerfish (Rhinecanthus aculeatus) is found throughout the tropical and subtropical Pacific and Indian Ocean. It is common in shallow protected reef flats and lagoons in Hawaiian waters. This species builds nests approximately every three weeks, spawning up to a million eggs. Females aggressively defend the nest. The larvae are very similar to crosshatch triggerfish larvae in size and early development.

Dozens of live foods were isolated from waterways around Oahu, including dinoflagellates, diatoms and many types of ciliates. After more than 20 larval trials using angelfish larvae as a control and wrasse and triggerfish larvae as the test animal a breakthrough was made with an isolated ciliated protozoan oligotrich. The organism was used for 10 days to bridge the critical food size gap and allow the larvae to feed on copepod nauplii. A write-up involving this research is planned.

Crosshatch triggerfish - Xanthichthys mento
Industry First
First raised at RCT in August 2011

We decided to breed the crosshatch triggerfish (Xanthichthys mento) because of its popularity in the aquarium trade, its high and dependable embryo production and its primitive and challenging-to-raise larvae.

Crosshatch triggerfish prefer cooler water between 65 and 74F. In warmer waters of the main Hawaiian Islands they are rare and mostly found singly or in pairs at depths exceeding 200 feet. In cooler waters of the Revillagigedo Islands they are common in shallow waters and form groups of multiple males and females (pictured).

The species spawns approximately every 19-23 days in captivity. It scatters up to a million eggs on the tank bottom substrate. The embryos are 0.48 mm in diameter and the first feeding larvae are 2.1 mm TL. The larval stage is very long, exceeding 100 days.

Clockwise from top left: Crosshatch triggerfish (X. mento) pair (male below female). Triggerfish larva, 2.3 mm TL, 7 days post-hatch (dph), 3 days after first feeding. Triggerfish larva, 8.9 mm TL, 42 dph. Triggerfish post-larva, 43 mm TL, 101 dph.

Interesting Fact
The crosshatch triggerfish is the second triggerfish species to be raised in captivity. The first captive-bred triggerfish was the queen triggerfish (B. vetula). This feat was accomplished in 2009 by a research team headed by Dr. Andrew Rhyne, a scientist at New England Aquarium (NEAq) and a Associate Professor at Roger Williams University (RWU).