Gobies, wrasses, and angels will undoubtedly have their time in my column, but every now and then it’s nice to mix things up and toss in an unusual fish. For American hobbyists, I think we are doing just that this month. It is not often that any members of the Caesionidae family make it into the American market. Naturally, when they do show up at the fish store in your neighborhood, not much is known about their natural history and captive care. To the credit of the fish, they are naturally hardy aquarium inhabitants. To the dismay of some hobbyists, they don’t always make the best friends of other inhabitants in the confined quarters of our aquariums. Hopefully, your New Year’s resolution was always to research your aquarium purchases before they’ve been released into your care. As a result, you might avoid adding a snapper commonly referred to as a fusilier.

Also known as the Scissortail Fusilier, Caesio caerulaurea makes an attractive aquarium fish with its bluish-silver scales and a vibrant yellow streak running the length of the lateral line. Photo courtesy of John Randall.

Meet the Family

The Family Caesionidae was erected by Johnson (1980), but only after extensive osteological research. Because of his efforts, we believe that the family has two sub-families, four genera, six subgenera, and 21 species. It should be noted that Johnson labeled only 15 species; the additional six species came with Carpenter’s (1987) revision of the family. As astute readers of my column should expect, however, the classification of this family was not always so cut and dried.

Lacepede (1801) laid the tracks when he described Caesio caerulaureus (later corrected to C. caerulaurea - more on this below) as a new genus and species. The most notable feature of C. caerulaurea was a protrusible jaw. This jaw structure has proven effective for capturing plankton. Given its similar bodily shape, Lacepede aligned Caesio close to the planktivorous tunas.

The characteristics that later defined both species and the family itself were unclear when much of the early work on the group was done. As an example of this confusion, Cuvier and Valenciennes, in 1830, originally had described nine species, however, only five were later recognized as valid species, including three which were newly described in the paper. A similar situation occurred when Bleeker (1853a, 1853b, 1856, 1865) introduced four new species into the genus Caesio. Only one of the four species remains in Caesio today. Furthermore, he errantly named one genus, Paracaesio, which is now a valid genus in the family Lutjanidae. In Bleeker’s defense, he is credited with establishing the remaining three genera of the family. He did, however, place his five genera of caesionids within the family Maenoides (1873).

Klunzinger (1870) was the very first author to separate Caesio into a separate family when he erected the Caesionidae . The majority of authors thereafter nevertheless did not agree with this assessment and did not recognize the Caesionidae. Some authors (Snyder, 1912 and Fowler, 1928) aligned the species with Haemulidae, and yet others (Schultz, 1953 and Norman, 1966) placed them within the family Lutjanidae. I can honestly list references for over a dozen peer reviewed papers which contain differences of taxonomical opinion, but I think that would be going over the top and you probably get my point already. As I mentioned at the head of this section, the revisions by Johnson (1980), and subsequently by Carpenter (1987), have been instrumental in clarifying the state of the family as we now understand it.

Let’s get back to Caesio caerulaureus being renamed C. caerulaurea. Lacepede originally named the genus Caesio for what he believed was the masculine Latin word for blue-grey, the life-color of the fish species he was describing. Ironically enough, however, he doomed the genus to confusion from the start - he meant to use the Latin adjective for blue-grey, which is caesius. “Furthermore there is a feminine Latin noun caesio which means … a wounding, or killing (Carpenter, 1987).” But wait; there’s more! “The genitive case of Caesio is Caesionis; therefore the correct basonym for higher ranks is Caesion and hence the family name is Caesionidae (Carpenter, 1987).”

Locals of the Caroline Islands called this fish the Tile fish and when researchers needed a name for their new species description they chose Pterocaesio tile in honor of the locals. The blue stripe, which runs from gill plate to the caudal fin, has iridescent hues and looks spectacular underneath actinic lighting. Adults will be less than 10 inches in length. Photo courtesy of John Randall.

Articles 30 and 32 of the International Code of Zoological Nomenclature specify that the original spelling will be retained but all species names will be changed to reflect the feminine status. In other words, it is the noun gender agreement code for marine ichthyologists. OK, so what does this mean? In short, all species names ending in “reus,” as in C. caerulaureus, will be changed to “rea,” or C. caerulaurea. One last note on this topic: because the effect goes all the way up to the family name, all the generic names of the family are affected accordingly.

Without further ado, the complete classification of the family as opined by Carpenter (1987) is presented below.

Caesionidae’s defining characteristics are listed as “ascending premaxillary process a separate ossification. Etho-maxillary ligament absent.” In addition, they are described as having a highly protrusible mouth and a deeply forked caudal fin, small ctenoid scales, and small conical teeth. Many additional, greatly generalized descriptions of the family’s features are present, but perhaps more important are the differences that create the two subfamilies, genera, and subgenera. Given the number of subfamilies, subgenera, et cetera, and the close resemblance of all members to one another, I think a chart of the osteological features that separate one from the other will likely assist the reader in gaining a better grasp of the family. Of concern below are a number of areas probably unfamiliar to the majority of hobbyists. Hopefully, a few short sentences describing the scientific terms in an easier to understand language will also assist in this regard. Please note that both the above classification and the differences noted below are taken from Carpenter (1987).

The median fins are those fins attached along the centerline of the fish, namely the caudal, anal and dorsal fins. When present, the conical, or cone-shaped teeth are located on the premaxilla, the bone which forms the front portion of the upper jaw of the fish. In regards to Caesionidae, this can be in either one or two distinct pieces.

Naturally, the postmaxillary bone(s) comprise the rear portion of the jaw. Again, in species placed in the Caesionidae there may be either one or two distinct bones. Additionally, the bone which forms the roof of the mouth is called the vomer. The bones which surround the palate of the fish are referred to as the palatines. All of these bones may carry teeth.

The internal bone (or sometimes cartilage) which supports a median fin ray or spine is called a pterygiophore. This particular bone for Caesionidae species is divided into three sections. The exact number of these bones can vary within the genus Caesio. Epipleural ribs refers to ribs which start at the pleurapophysis, or the lumbar vertebrae. Finally, the number of openings along the throat region is described as pars jugularis.

The bony flap which covers the gills is called the opercle or operculum. Certain Caesionidae have a flap at the rear quarters of the opercle.

In the Wild

Fusiliers prefer only the warm waters of the tropical Indo-Pacific region. No members of the family have been noted to extend into subtropical waters, nor are species present in the Atlantic or Caribbean. Two species, Caesio suevica and C. striata, are endemic to the Red Sea, while localized distribution in the Indian Ocean is also displayed by C. xanthonota, C. varilineata, and Pterocaesio capricornis (east coast of Africa). Caesio teres could be considered to have the largest geographical distribution, as this species has been recorded from the eastern shores of Africa to the Palmyra group of islands. Not to be outdone, however, members of Caesio caerulaurea have been collected from Samoa to the Red Sea. Species from Indonesia and the Philippines represent an important element of the commercial fishery.

In addition to the black spots at the tips of the caudal fin, which is present on all Red Seas species, Caesio suevica sports a white margin around the inside of the spots. All other species with the black spots on the caudal fin lack these white stripes. Adults will almost reach nine inches in length. Photo courtesy of John Randall.

Whenever they are found, the sheer numbers of fusiliers present can be staggering. They prefer to stay in tight schools, usually residing close to a nearby reef face or underneath an overhang when danger is present. Most of the family members have been noted to adjust their coloration to shades of red or brown to closely resemble the rock behind them - an act of camouflage. When undisturbed, at night the fusiliers will relate to the reef and disappear for the evening because they are diurnal. Otherwise, a tight school will move over the reef wall or adjacent to the reef in open water and continually feed throughout the daylight hours. Schools frequently consist of at least two different species. Only a single species, Dipterygonotus balteatus, is known to be pelagic, while all of the remaining family members relate closely to coral reefs, most often on steep reef slopes from 40 to 200 feet deep.

More commonly found sold alongside freshly caught sardines than in aquarium stores, Dipterygonotus balteatus, the Mottled Fusilier, is also the lone species of Caesionidae which does not relate to coral reefs, instead opting for a near-shore pelagic lifestyle. It is also one of the smallest Caesionids reaching a length of only four inches. Photo courtesy of John Randall.

Unlike the vast majority of snappers, fusiliers are planktonic feeders. Although the sound of their common name might suggest otherwise, they are not fussy feeders. If an item drifts past their vicinity, and it fits into their mouth, they likely will eat it. This includes items ranging in size from as small as larval fish or shrimp, to basically any non-venomous vertebrate or invertebrate that is small enough to fit into their mouth and which has the misfortune of swimming or drifting past the fusilier.

The individuals of most species generally remain under 10 inches in length, although in some species such as Caesio cuning and C. teres individuals may reach up to 16 - 20 inches. Males are externally indistinguishable from females. Very little is known about the family’s spawning and mating rituals. Bell and Colin (1985) reported a mass spawning of Caesio teres occurring around sunset, and to this day it remains the lone occasion this family’s spawning has been recorded.

	The vast geographical distribution of Caesio teres is largely responsible for the frequency that it makes it into the aquarium trade in relation to its other family members. The top photo is a C. teres taking on the reddish-brown coloration common amongst Caesionids during periods of stress or rest. The bottom photo shows its normal coloration. Photos courtesy of John Randall.

In the Home Aquarium

Although it isn’t all that often that any of the fusiliers show up in aquarium stores in the United States, they are fairly common overseas. Many species are attractive, but their size and diet doesn’t make them the best of reef aquarium inhabitants. Feeding them isn’t the issue at hand; as planktivores they are very easy to feed once established in the home aquarium. Almost anything floating in the water column will get taste-tested, making the home aquarist’s job that much easier. Even so, a proper diet must be achieved. A diet rich in mysid species shrimp will go a long way toward accomplishing this. Other foods which will serve fusiliers well include: enriched brine shrimp, frozen/thawed mosquito larvae, chopped clams and squid meat, and any of the commercially available flake or pellet foods designed with the carnivore in mind.

The issue which gives greatest concern to aquarists intending to keep fusiliers in the home aquarium is their potential tank mates. Small gobies, blennies, and pretty much anything that fits into their mouth, will need to be avoided. They will become a meal immediately upon entering the aquarium. Conversely, fusiliers could almost be considered a wimp in the aquarium itself as larger, more active fish will cause the fusiliers to remain uncomfortable and prevent them from settling in to the aquarium. A happy medium must be realized. Achieving this is considerably easier if you are capable of acquiring juvenile fusiliers to begin with. The size of the adult, and consequently the size of the food items it is capable of swallowing, can present stocking problems. Good options for tank mates would include most wrasses, dwarf angels, small groupers, and basses, to name a few. Fusiliers generally do not bother fishes they cannot swallow. In most situations fusiliers will remain nearly oblivious to their tankmates if they are themselves left alone. Mixing fusiliers with other snappers, however, is not a good idea. To maximize the odds of a good mix, consider obtaining species known to have overlapping geographical distribution with the fusiliers and which are also known to interact in the same schools.

The Goldband Fusilier, with the yellow stripe common to many Pterocaesio, makes an attractive aquarium inhabitant. As one of the smaller fusiliers, Pterocaesio chrysozoma will also adapt well to an aquarium. Adults reach eight inches in length. Photo courtesy of John Randall.

Compatibility chart for the family Caesionidae:

Fish	Will Co-Exist	May Co-Exist	Will Not Co-Exist	Notes
Angels, Dwarf	X			A good option.
Angels, Large	X			A good option. Add fusilier first.
Anthias		X		Both are planktivores. This can be a bad mix in a small aquarium.
Assessors			X	Assessors are at risk of being consumed.
Basses	X			A good option, assuming individuals of like size are obtained.
Batfish	X			A good option.
Blennies		X		Small blennies should be avoided.
Boxfishes	X			A good option.
Butterflies	X			A good option. Add fusilier first.
Cardinals		X		Small cardinalfishes should be avoided in the presence of larger fusiliers. Add cardinals first.
Catfish	X			A good option. Add fusilier first.
Comet	X			A good option. Add comet first.
Cowfish	X			A good option.
Damsels		X		Certain damsels may harass fusiliers too much. Add fusiliers first, if you wish to try.
Dottybacks		X		Certain dottybacks need to be avoided. Commonly available, captive-bred dottybacks are a good option.
Dragonets	X			A good option.
Drums	X			A good option, assuming individuals of like size are obtained.
Eels		X		A good option if the larger, more aggressive eels are avoided.
Filefish	X			A good option. Add fusilier first.
Frogfish			X	Frogfish will try to consume fusiliers.
Goatfish	X			A good option.
Gobies			X	It may be best to avoid gobies as the small ones can become food for the fusilier.
Grammas		X		Small grammas in first, otherwise obtain individuals of similar size.
Groupers		X		Avoid large groupers or groupers that can become large, and add fusilier before small grouper.
Hamlets	X			A good option. Add fusilier first.
Hawkfish	X			A good option. Add fusilier first.
Jawfish	X			A good option. Add jawfish first.
Lionfish		X		Fusilier in first; obtain juvenile lionfish.
Parrotfish		X		Fusilier in first; obtain juvenile parrotfish.
Pineapple Fish	X			A good option. Obtain pineapple fish first.
Pipefish			X	Pipefish are best left to their own aquarium.
Puffers	X			A good option. Add fusilier first.
Rabbitfish	X			A good option. Add fusilier first.
Sand Perches		X		Obtain individuals of like size. Some sand perches can become aggressive over time.
Scorpionfish		X		Fusilier in first; obtain juvenile scorpionfish.
Seahorses			X	Seahorses are best left to their own aquarium.
Snappers		X