Files Not Meant For Your Toolbox (or Reef Aquarium): The Genus Pervagor by Henry C. Schultz III

Files Not Meant For Your Toolbox (or Reef Aquarium!):
The Genus Pervagor


Many marine aquarium hobbyists are always on the lookout for something new and exotic to catch their eye while perusing available livestock at their local fish stores. This trait is just part of being a true hobbyist. This ongoing search seems only to intensify the longer the aquarist remains active in the hobby. So, it stands to reason that eventually the hobbyist is going to come across the bizarre-looking fish of the genus called Pervagor. Although they are not regularly offered for sale, oftentimes when the aquarist stumbles upon them, an impulse purchase ensues. Hopefully, this isn't the case and instead the seasoned aquarist decides to find more information on this fish prior to purchase. That is the best-case scenario, however. More than likely, though, the impulse purchase does indeed take place and you have found this page only after the first couple of days of owning one haven't gone so well. In either case, I present the Filefishes, genus Pervagor, as the February edition of "Fish Tales."

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A beautiful tail display from this Pervagor spilosoma.
Photo courtesy of Keoki Stender, Fishpics Hawaii.

Meet the Family

Nelson (1976) placed Pervagor in the subfamily Monacanthinae, but more recent works (Nelson, 1994; Michael, 1998) have elevated it family status, thus the family Monacanthidae is recognized. Monacanthidae is among the Order Tetraodontiformes, which also includes the extremely personable triggerfish and puffers. Another 30 genera (31 total) are represented in the family Monacanthidae, numbering just slightly above 100 species in all.

The genus, which contains a total of eight species (see below), was originally described as a subgenus of Stephanolepis by Whitley (1930). At that time, 13 species were placed in that subgenus. Later work by Fraser-Brunner (1941) raised Pervagor to generic status and named six species. Finally, Hutchins (1986) provided an in-depth review of the genus, and his work accounts for the present order of eight species.

Monacanthidae
Pervagor
alternans
aspricaudus
janthinosoma
marginalis
melanocephalus
nigrolineatus
randalli
spilosoma

The differences between the original thirteen described species and the current eight specimens are two-fold. First, the species tomentosus was erroneously placed in Pervagor and was later correctly placed into the subgenus Acreichthys, which is now recognized as a valid genus (Hutchins, 1986). Second, the three species were erroneously described only from specimens of pelagic prejuvenile individuals. Pervagor prejuvenile individuals do not resemble their adult forms, or even their juveniles, having different coloration or body shape. Do not confuse prejuvenile with juvenile specimens. Prejuvenile specimens have not yet settled and possess features indicative of the pelagic life. The fully settled juveniles have nearly the adult coloration and body form and typically lack only the sexual structures and characteristics found in mature animals. This failure to distinguish the prejuvenile from the juvenile resulted in the erroneous naming of three additional specimens. Further research with the species of the three erroneously named species proved they were indeed the prejuvenile individuals of other, already described species (Hutchins, 1986).

Previously used, but erroneous
species names of Pervagor:

nitens
pricei
scanleni

Pervagor has been further divided into two complexes. The first complex, referred to as the melanocephalus complex (see below), is noted to have "the posterior margin of the ventral flap narrowly attached to the pelvic fin rudiment" (Hutchins, 1986). Being the lone member of the nigrolineatus complex, nigrolineatus is noted as having "the pelvic fin rudiment broadly attached to the posterior margin of the ventral flap" (Hutchins, 1986).

Members of the melanocephalus complex:

alternans
marginalis
aspricaudus
melanocephalus
janthinosoma
randalli
spilosoma

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Pervagor nigrolineatus is not often seen in the hobby, most likely due to the drab coloration when compared to some of the other Pervagor species. However, color, size, fin-ray counts, and overall size are noted to be highly variable depending upon the locale of the fish. Photo courtesy of John Randall.

Regardless of the complex, however, all Pervagor species are known to share a few common traits. Most notable is the first dorsal spine, which is armed with two rows of laterally directed barbs. In addition, all Pervagor species have a barbed pelvic rudiment and 10 teeth in the upper jaw (five per side with three outer and two inner teeth) and six teeth in the lower jaw (three per side).

In the Wild

The largest geographical distribution for Pervagor is found among P. janthinosoma and P. aspricaudus, which have a natural home range from the east coast of South Africa and the Red Sea to as far west as the Hawaiian Islands. However, even though P. janthinosoma is the most abundant member of the genus, it does not extend east of Samoa, while P. aspricaudus does. Of the remaining six species, five are rather geographically limited including P. spilosoma, which is endemic to the Hawaiian Islands, and P. randalli, which hails from the Red Sea.

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One of the most recently described specimens (Hutchins, 1986), Pervagor randalli
may still be imported as P. melanocephalus. Photo courtesy of John Randall.

The depths at which filefish can be found do not widely fluctuate among members of the genus. Although Pervagor spilosoma has been taken by trawls at depths of 180 feet, filefish generally range between 30 to 60 feet of depth. The notable exception is P. melanocephalus, which prefers depths below 100 feet, although it appears none have been collected from as deeply as P. spilosoma. At these depths the filefish associate with diverse, rocky coral reefs, and they most often relate to the substrate, choosing to remain fairly close to it. It is upon these reefs that the filefish, most often seen as individual adults or pairs, feed. Technically, Pervagor are classified as omnivores, meaning that filefish will basically feed upon most anything that garners their interest. Although most filefish have a diet rich in various algae, they will also feed upon most any meat-based food items such as clams, shrimp, or small fish, and even dine on the occasional coral (I should note that some members of the family Monacanthidae are strict corallivores). It is not unusual to see two separate species of Pervagor feeding upon the same reef. In fact, in areas where these two species are sympatric, divers frequently report seeing the two species swimming together as a pair.

Many of the males in species of this genus can be readily differentiated from the females of the same species. Although the differences may be slight, they are detectable. For instance, in Pervagor nigrolineatus the male's second through fourth anterior soft dorsal rays are more elongated than those of the rest of the remaining rays. Females of the same species lack the elongated soft dorsal rays entirely. Other differences noted among the genus include the scale spinules on the posterior half of the body. On males, the spinules curve forward, whereas on the female they project rearward.

Even though confusion existed early on with this genus, it was only because it was named using juvenile specimens as type specimens. Nowadays, it is recognized as a disntict species, and Pervagor alternans is easily identified by the yellow circle around the eyes. Photo courtesy of John Randall.
click here for full size picture

In the Home Aquarium

First and foremost, I should stress the point that most filefish typically do not do well in the home aquarium, especially Pervagor. Although a reef aquarium does provide the best opportunity towards long-term care, the destruction caused by the filefish quite possibly far outweighs the pleasure of maintaining them. In the wild the occasional nipping of coral polyps by the filefish rarely leads to the death of a coral. However, in the confines of the home aquarium, corals are not so lucky. The unavoidable, persistent nipping by the filefish is often too much to cope with and ultimately the death of the coral ensues.

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Pervagor melanocephalus, commonly referred to as the Blackheaded Filefish, is a beautiful filefish and is occasionally available in retail outlets. It appears sympatrically with the Fantail Filefish, as well as in other western Pacific locations. Unfortunately, it does not fare as well as the Fantail. Be sure it is eating prior to purchase. Photo courtesy of John Randall.

As a whole, filefish are known to regularly refuse to eat and may eventually starve to death in captivity. The best feeding option to prevent this unfortunate event includes regularly offering live foods. For most aquarists, the most readily attainable live food is brine shrimp. Adult brine shrimp are preferred unless the filefish is especially small. Once the filefish begins accepting live food, it is best to try to wean them onto the frozen variety of the same type of food. This is best accomplished by slowing mixing the prepared food with the live food until eventually no live food is being fed at all. Of course, the logical next step would be to introduce a greater variety of food. Because filefish are omnivores, they can essentially be fed any foods regularly offered to the trade for herbivorous and carnivorous fish. Also, because they are omnivores, try to make sure a well-varied diet is provided; repeatedly offering the same foods should be strictly avoided.

The difficulty of getting a filefish to eat may require it to be purchased from a local store where the fish can be observed eating prior to its purchase. For this reason alone, purchase of these fish online is discouraged; it should be obvious that it's too great of a gamble that one will be acquired from an online supplier that is in good health and eating.

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Because the photo is of a preserved specimen, this Pervagor marginalis is missing a black
band which it was named for. The bar extends from the base of the pectoral fin through the
eye and onto the nape of the fish. Photo courtesy of John Randall.

Assuming you can find one that is eating, it needs to be placed into the proper environment. The ideal aquarium would be moderately filled with live rock such that open water swimming space is provided, yet one in which ample hiding places into which the fish can retreat are also available. Given their omnivorous tendencies, the presence of various macroalgae should be considered a bonus - if not a requirement. Although the adult size of filefish is highly variable, any standard six-foot long aquarium should provide ample room for a single adult.

The tankmates of the filefish also warrant some discussion. Even though some filefish can attain lengths over six inches, any tankmates included must be passive. If aggressive eaters or fast-swimming fish are already in the aquarium prior to the introduction of the filefish, the chance for success drops dramatically. Pervagor species are timid upon addition to a new aquarium, and the aggressive feeders may not allow them a chance to settle into the aquarium. This would include all surgeonfish, large angels, and larger wrasses. Some of the better choices may include gobies, grammas, and wrasses of the genus Macropharyngodon. Placing individuals from two Pervagor species in one aquarium is not advised. Exceptions would include exceptionally large aquariums, or two fish that were obtained as a male-female pair. Although Pervagor species can be observed associating together in the wild, it seems this mutual respect in the wild does not transfer to the home aquarium in most circumstances.

Compatibility chart for Pervagor:

Fish

Will Co-Exist

May Co-Exist

Will Not Co-Exist

Notes

Angels, Dwarf

 

X
 

Add the filefish first and allow it to acclimate.

Angels, Large

 

 
X

Will likely harass or stress the filefish.

Anthias

 
X

 

Add the filefish first and allow it to acclimate.

Assessors

X
 

 

Excellent choice.

Basses

 

X
 

Add the filefish first and allow it to acclimate.

Batfish

 

 

X

Large size and aggressive feeding habits.

Blennies

X
 

 

Excellent choice.

Boxfishes

X
 

 

Excellent choice.

Butterflies

 

X
 

Add the filefish first and allow it to acclimate.

Cardinals

X
 

 

Excellent choice.

Catfish

 

X
 

Add the filefish first and allow it to acclimate.

Comet

X

 

 

Excellent choice.

Cowfish

X
 

 

Excellent choice.

Damsels

 

 

X

Will likely harass or stress the filefish.

Dottybacks

 

X
 

Add the filefish first and allow it to acclimate.

Dragonets

X

 

 

Excellent choice.

Drums

X
 

 

Excellent choice.

Eels

 

X
 

Some eels are best left in their own aquarium.

Filefish

 
X

 

Some filefish may co-exist.

Frogfish

 
 

X

May consume filefish.

Goatfish

X
 

 

Excellent choice.

Gobies

X
 

 

Excellent choice.

Grammas

X

 

 

Excellent choice.

Groupers

 

 

X

Will likely harass or stress the filefish.

Hamlets

X

 

 

Excellent choice.

Hawkfish

 

X

 

Add the filefish first and allow it to acclimate.

Jawfish

X

 

 

Excellent choice.

Lionfish

 

X
 

Add the filefish first and allow it to acclimate and purchase juvenile lionfish.

Parrotfish

 

 
X

Will likely harass or stress the filefish.

Pineapple Fish

X

 

 

Excellent choice.

Pipefish

 
 

X

Pipefish are best suited in their own aquarium.

Puffers

 

 

X

Will likely harass or stress the filefish.

Rabbitfish

 

 
X

Will likely harass or stress the filefish.

Sand Perches

 
X

 

Add the filefish first and allow it to acclimate.

Scorpionfish

 
X
 

Add the filefish first and allow it to acclimate.

Seahorses

 
 

X

Seahorses are best suited for their own aquarium.

Snappers

 

 

X

Will likely harass or stress the filefish.

Soapfishes

 

 

X

Will likely harass or stress the filefish.

Soldierfish

X

 

 

Excellent choice.

Spinecheeks

X
 

 

Excellent choice.

Squirrelfish

X

 

 

Excellent choice.

Surgeonfish

 

 
X

Will likely harass or stress the filefish.

Sweetlips

 

X

 

Add the filefish first and allow it to acclimate.

Tilefish

X

 
 

Excellent choice.

Toadfish

 
 

X

Will likely harass or stress the filefish.

Triggerfish

 

 

X

Will likely harass or stress the filefish.

Waspfish

 
X

 

Add the filefish first and allow it to acclimate.

Wrasses

 

X

 

Use discretion - avoid large or over-active wrasses.

Note: While many of the fish listed are good tank mates for Pervagor species, one should research each fish individually before adding it to the aquarium. Some of the fish listed above are better left in the ocean or for advanced aquarists.

A final note regarding filefishes in the home aquarium: do not use nets to handle them. Their rough scales have a tendency to become caught in the webbing of the nets. Obviously, this causes undue stress upon the animal when attempting to release it. The best option is to gently direct the fish towards a large, clear specimen container and lift the fish out of the aquarium using the container.

Meet the Species

The most commonly imported filefish from Pervagor is P. spilosoma, or the Fantail Filefish. Fortunately, this also happens to be the best filefish at adapting to aquarium life. It is not uncommon for this filefish to begin eating prepared foods. Although not endemic to the Hawaiian Islands, P. spilosoma is considered rare at the Johnston Atoll - the only other locale it is known from. It prefers the shallow reefs around Hawaii, rarely going deeper than 60 feet. Two population explosions of this species have been noted around the Hawaiian Islands; one in 1975 and the another in 1985. Large individuals may reach up to seven inches in length.

click here for full size picture
click here for full size picture
Pervagor spilosoma is possibly the most common reef fish among the Leeward
Group of the Hawaiian Islands. They become larger than many of the other
Pervagor species, attaining around seven inches of length.
Photos courtesy of Keoki Stender, Fishpics Hawaii.

Pervagor spilosoma appears sympatrically with P. aspricaudus, or the Orange-Tail Filefish (not to be confused with the Orange-Spotted Filefish, Oxymoncanthus longirostris) in Hawaii. However, the Orange-Tail is not nearly as common in Hawaiian waters as the aforementioned P. spilosoma. It is average-sized for Pervagor species, topping out around five inches.

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Pervagor aspricaudus, also called the Orange-Tail Filefish, prefers isolated locations in the wild.
It would be best to try to simulate this in the home aquarium.
Photo courtesy of Keoki Stender, Fishpics Hawaii.

Another commonly imported specimen is Pervagor janthinosoma, or the Blackbar Filefish. At one point P. janthinosoma was regarded as a synonym of P. melanocephalus, but further research resulted in the melanocephalus complex and P. janthinosoma being raised to generic status. The similar appearance of the Blackbar Filefish to all the other members of the melanocephalus complex results in the frequent misnaming of imported specimens. Due largely to this, and the fact that P. janthinosoma generally does not begin to accept prepared foods as readily as the Fantail Filefish, I recommend aquarists avoid this species.

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Pervagor janthinosoma, the Blackbar Filefish, will barely exceed five inches in the home
aquarium. Avoid this species unless you witness it eating prior to purchase. This
particular specimen was photographed in a home aquarium.
Photo courtesy of Greg Rothschild.

Conclusion

The purchase of a filefish is not one to be taken lightly; it can test the experience and resolve of the most seasoned veterans. I hope you had a chance to read this prior to the purchase of a filefish, thereby empowering yourself to make an informed decision. For those aquarists reading this after the purchase, with any luck this will serve as a launching pad to a successful husbandry.



If you have any questions about this article, please visit my author forum on Reef Central.

References:

Baensch, H.A. 1994. Baensch Marine Atlas, Volume 1. Microcosm. Shelburne, VT. 1215 pp.

Hutchins, J. B. 1986. Review of the Monacanthid Fish Genus Pervagor, with descriptions of Two New Species. Indo-Pac. Fish. No. 12: 35 pp.

Lieske, E. and Myers, R., 1994 Collins Pocket Guide. Coral reef fishes. Indo-Pacific & Caribbean including the Red Sea. Harper Collins Publishers, 400 pp.

Michael, S.W. 1998. Reef Fishes Volume 1. Microcosm. Shelburne, VT. 624 pp.

Michael, S.W. 1999. Marine Fishes 500+ Essential-To-Know Aquarium Species. Microcosm. Shelburne, VT. 448 pp.

Nelson, J. 1976. Fishes of the World. New York. John Wiley & Sons, Inc. 416 pp.

Nelson, J. 1994. Fishes of the World. New York. John Wiley & Sons, Inc. 624 pp.

Whitely, G. P. 1930. Additions to the checklist of the fishes of New South Wales, no. 3. Astral. Zool. 6(2): 117 - 124, 1 pl.




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Files Not Meant For Your Toolbox (or Reef Aquarium!): The Genus Pervagor by Henry C. Schultz III - ReefKeeping.com