a newHarlequin future for the

keeping and breeding Oxymonacanthus longirostris, a spectacular and challenging species

Story and photos by Matt Pedersen TK

64 CORAL THET DAZZLING APPEARANCE OF THE HarlequinH Filefish, a flamboyant little beautyb with beaked snout and promi- Filefishnentn Swiss-watch eyes, represents the veryv reason so many of us are drawn to marinemarine aquariums. When in good health and fullfull ccoloration,ol it is an arresting species and undeniably seductive for fishkeepers. Common in the wild and found through- out the sprawling Indo-Pacific, from East Africa to Okinawa and Samoa, Oxymonacanthus lon- girostris is imported and offered for sale under a variety of common names, most often the Orangespotted Filefish (a common name also routinely applied to the west Atlantic species Cantherhines pullus), but also the Longnose File- fish or, in Australia, the Beaked Leatherjacket. Harlequin Filefish are typically offered at very affordable prices that often entice an uniniti- ated aquarist to make an impulse purchase. Only later does the hobbyist learn that the Harlequin Filefish is an obligate corallivore that experts say is “rarely alive for more than a week in captivity” and is “doomed to die,” a fish “best left in the ocean.” The pervasive infor- mation available suggests that this fish simply cannot be kept alive without live corals to feed on. Those who attempt to keep this species risk the condemnation of their fel- low aquarists, who often sug- gest returning the fish to the shop that sold it before it dies. What we might not consider is that this advice is often coming from people who have never attempted to keep the species—

Large image: Trio of healthy Harlequin Filefish broodstock, male at center, in the author’s nano-reef. Inset: Female in good condition. TK

CORAL 65 Group of newly imported Oxymonacanthus longirostris being drip acclimated in a 5-gallon bucket.

they are simply repeating what they’ve been told. This it’s time to rethink our stance on this remarkable fish. notion, which is decades old, is so firmly entrenched in Experienced aquarists can master this species, but it’s hobby literature that most responsible aquarists never not easy. I must emphasize that wild-caught specimens question it, and choose to admire this species in pictures are absolutely not for beginners, or even hobbyists with or through the lens of a dive mask. a couple of years of experience. Keeping wild-caught Harlequin Filefish should only be attempted after care- BREAKTHROUGH EXPERIENCES ful deliberation and preparation by dedicated, advanced While that information may have been completely valid hobbyists. Even then, failure (death of a fish) is a pos- and accurate 20 years ago, it isn’t today. Inspired by the sibility that must be accepted before attempting to main- pioneering work of Iris Bönig, who in 2007 became the tain this species. first person to spawn and successfully rear the Bristletail How did the Harlequin Filefish go from doomed to Filefish (Acreichthys tomentosus), I set out to follow her viable? Advancements in the chain of custody from col- lead. I was unable to find Bristletail Filefish locally, but lector to home aquarist mean that sensitive fish arrive instead serendipitously encountered Harlequin Filefish, in better shape now than they did in past decades. The which I reluctantly purchased, assuming failure was like- reduction of drug-caught specimens in the supply chain ly. To my own surprise, in a little over a year I’ve attempt- has also lowered the incidence of “mystery deaths,” espe- ed to keep 17 wild-caught Harlequin Filefish—and suc- cially those that occur in the short term. A better under- cessfully established 12. While I’m not the first to spawn standing of overall marine fish nutrition has resulted in this species in captivity (a single anonymous spawning the availability of far more diverse and nutritious foods report was submitted to the Breeder’s Registry in 1994), to offer our fishes. Equipment and husbandry develop- I believe I’m the first person to successfully spawn and ments, spurred by the boom in reefkeeping in the last rear this species in captivity (and in completely closed two decades, have given us the ability to provide more culture as well), producing the world’s first captive-bred stable, more pristine environments. Improved knowl- Harlequin Filefish. Based on what I’ve learned, I believe edge of marine-fish social structures and behaviors have

66 CORAL helped, too. The Internet has also brought aquarists to- and pellet foods, as well as frozen blended diets, enriched gether to share personal experiences and offer creative frozen brine shrimp, Mysis shrimp, minced squid, and solutions to urgent problems. more. These fish simply won’t thrive without multiple feedings every day. DIETARY MYTHS Harlequin Filefish are somewhat reef safe. A few To reassess the Harlequin Filefish, we must address the aquarists have successfully maintained these fish in large core belief that they will die without live coral flesh in reef aquariums of 200 gallons or more (757+ L) that are their diet, specifically the polyps of small-polyp stony filled with SPS corals. They note no visible damage from (SPS) corals such as Acropora, Montipora, and Pocillipora the filefish feeding on the corals, but some corals cease species. This is simply not true. I am aware of several to extend their polyps during the daylight hours. aquarists who have documented captive lifespans in the For the rest of us with smaller reefs, consider that range of three to five years, feeding nothing but prepared a well-fed filefish is less likely to antagonize the corals. foods. The fact that this species has been brought into The Harlequins kept in my SPS tank ignore Montipora daily spawning condition with only prepared foods fur- capricornis, but do nibble on M. digitata and Seriatopora ther disproves the hypothesis that there is some critical hystrix that continue to grow but no longer extend their nutritional element found only in live corals. My first polyps when the lights are on. Other aquarists have had captive-bred juveniles have been reared exclusively on problems with LPS corals such as Acanthastreas. You rotifers and baby brine shrimp, later weaned onto pellet should be prepared to address the incompatibilities that and flake foods. These babies even went so far as to show may occur between this fish and your corals. no interest in live coral when it was offered, While circumstances preferring the prepared foods. It is fair to say have improved for this that we do not know the true nutritional species as a wild-caught requirements of Harlequin Filefish—indeed, fish, they are still one of does anyone know the nutritional profile of the most difficult marine coral flesh? In the absence of that informa- tion, I have simply offered a widely varied Left: Moderately emaciated omnivorous diet based on the rudimentary male, showing sunken belly supposition that coral consists of both “ani- and nape. mal flesh” (the coral polyp itself) and “al- Below: Plump male after gae” (the zooxanthellae contained within). months of transition to prepared aquarium foods. LIFE IN CAPTIVITY It’s important to know that this spe- cies is best kept singly or in hetero- sexual pairs in a tank at least 10–25 gallons (38–95 L) in size. I have kept a trio (one male, two females) and pairs of females, but I can almost guarantee that two males will not coexist peacefully in the average hobbyist aquarium. Fortunately, sexing Harlequin Filefish is easy. The most pronounced sexual differences are in the ventral flap or pelvic rudiment. In males, the ventral flap is bright orange-red, bor- dered above by a thick band of black containing a few rows of fine blue- white spots. In females, the ventral flap is often black but at times may be a dirty orange. The prominent black border is absent in females, and there will be few fine white spots. Being active grazers, Filefish re- quire several feedings per day. My fish feed on multiple types of flake

CORAL 67 Left: Do-it-yourself filefish feeding sticks: frozen Ocean Nutrition Formula One marine protein and algae cubes, thawed and pressed onto dead branches of Acropora coral rubble. Opposite page: Weaning a filefish onto homemade feeding sticks. Inset: A newly arrived filefish eats coral polyps on a Bali Green Slimer, Acropora yongei.

new fish. Individual specimens establish themselves at different paces, and shared quarters can inhibit progress. A male, for example, may dominate a female before she has a chance to start eating and renourishing herself. For each fish, provide a 10-gallon (38-L) aquarium and all the basics—heater, simple light, filtration, and aeration. (I use Duetto 100 Internal power filters.) A Seachem Ammonia Alert Badge will help you quickly de- tect deteriorating water quality. You should pre-establish the filter media in your main aquarium sump or filter, and then move it to the quarantine tank when needed. Leave the tank bottom bare for easy cleanup of un- eaten food. Provide hiding places for the fish, but under fish to bring into captivity. They share traits with many no circumstances should you include anything resem- other fish typically considered for-experts-only, such as bling coral or coral skeletons. I’ve watched Harlequin Mandarin Dragonettes (Synchiropus sp.) and wild-caught Filefish nip at dead coral skeletons for hours on end in Seahorses (Hippocampus sp.). One or two mistakes are all dealer’s tanks, desperately trying to feed on something it takes to turn possible success into guaranteed failure. that simply isn’t there. We’ll take that strong instinctive There are several key considerations necessary to estab- feeding response and use it to our advantage. lish this species in captivity. OBTAINING YOUR FISH GATHER YOUR MATERIALS Harlequin Filefish are typically offered for sale in some Harlequin Filefish share a trait in common with other stage of starvation. Even in the earliest stages, the fish al- selective feeders: they only recognize certain offerings as ready show visible signs of emaciation, first with pinched suitable foods, and they are very hesitant to try anything stomachs, progressing to sunken areas along the nape remotely different. Ten to 20 years ago, the notion of and back, and ultimately to paper-thin fish that have no feeding live corals to a marine fish would’ve bordered on chance of survival. One strategy sometimes used is to lunacy. Today, cultured live SPS corals are not only avail- purchase your filefish from a reputable online vendor able, but they are commonplace and very affordable. This when a new shipment arrives. These new fish may spend abundance of live SPS coral means that the natural food less time in the chain of custody, starving less, and there- for this species is available to anyone who wants it. You fore should arrive in better shape. The downside is that can use live coral to ease the transition from a wild diet you are ordering sight-unseen. to something more easily sustained in the aquarium. Your other option is to source your fish from a local You shouldn’t have to feed your Harlequin Filefish shop. If your dealer gets his or her fish directly from an live SPS corals forever, but you should be prepared to importer, you can reduce the length of time the filefish offer them as a first food. Therefore, before you obtain spend without food. Buying locally, you have the advan- fish, you must secure a steady source of live Acropora and tage of viewing them firsthand. (Ethical retailers may not Montipora corals. Choose types that have larger extended stock this species, but will usually arrange special orders polyps. Hobbyists today often have extra frags, or you if you explain what you are doing.) You want only active may be able to purchase browned-out colonies from your and alert specimens that aren’t too emaciated. Speci- local fish store at a discount. Live coral is your insurance mens with sunken napes and backs are in much worse policy and safety net. shape than those that have only a pinched stomach. You will also need to obtain dead coral skeletons. I COMING HOME prefer Acropora species that have very rough corallites. Staghorns like Acropora yongei (Bali Green Slimer) are Most likely your new Oxymonacanthus longirostris will ideal. You will need at least six 2-inch (5-cm) sticks. not be eating. It’s important to note that a newly arrived Based on my own experiences, when I personally ad- filefish may display a preference for a certain area of the vise people on keeping this species, I insist that they use tank. Be sure to place food offerings in this preferred an individual quarantine tank as the first home for each location. New filefish are usually timid and reluctant to

68 CORAL CORAL 69 Undeterred by a pair of Spotted Mandarinfish (Synchirpus picturatus) and a pair of Ocellaris Clownfish (Amphiprion ocellaris), a pair of Harlequin Filefish in the author’s community nano-reef inspect a thatch of Red Gracilaria, where they will spawn later in the day. Male is at left with jet-black, spotted patch above his ventral flap or pelvic rudiment.

venture far for food. Competitive tankmates of any kind within a week or two, at which point you can try with- must be excluded. holding the live coral offerings. Throughout the next few The first food to offer is live coral. Getting the Har- weeks, you should not hesitate to offer other foods, but lequin Filefish to eat anything in captivity is a challenge, do not expect them to be eaten. Frozen enriched adult and live coral simply gets the fish over the stress and back brine shrimp is often the second food accepted, followed into a feeding mindset. If the frag dies (or gets eaten), later by the smaller varieties of frozen Mysis shrimp. En- offer another one. riched live adult brine shrimp has been tried with reluc- Once the fish nips at live coral, you can start the pro- tant feeders, but often the filefish appear uncomfortable cess of weaning. I’ve had the best success training Har- with such active prey. Surprisingly, flake foods sometimes lequin Filefish onto prepared foods by coating dead coral prove irresistible to a reluctant filefish. Pellet foods work skeletons with frozen mixed diet foods such as Rod’s well as another new food item because they sink to the Food or Ocean Nutrition’s Pygmy Angel Formula. (I got bottom and hold their form, allowing the fish to graze this idea from Robert P. L. Straughan, who mentioned naturally and making cleanup easy. the technique as a way to feed reluctant Butterflyfishes The first two weeks in captivity will be the most risky— in his 1959 book, The Saltwater Aquarium in the Home.) I all my own filefish losses occurred in this timeframe. This coat several frags each morning, working the food down is a time for very careful and frequent observation for ex- into the corallites, storing them in the refrigerator and tended periods of time. It is a period when nothing sub- offering them one at a time throughout the day. The file- stitutes for the experience of a long-term aquarist who fish will focus its hunger on the coated coral skeletons. has developed certain intuitions and learned to recognize At least once a day, siphon off the uneaten food and the early warning signs that are missed by a novice. remove the coral skeletons for cleaning and recoating the One important note: if you make it past two weeks, next morning. Monitor the Ammonia Alert Badge daily, your filefish will likely be thinner than it was when you and take corrective measures if ammonia levels rise. purchased it! If you have not had success getting the Typically, the filefish should be accepting frozen food fish to eat something other than live coral, you need to

70 CORAL reevaluate your efforts. You must continue to offer live an opaque yellow-orange color during this display. While coral until the fish no longer needs it. courting, females develop a pale horizontal stripe start- At the one-month mark, things are usually looking ing at the mouth; the forehead and dorsal spine often up. Most of the filefish I’ve established were eating with become pale, almost white. greedy appetites at this point and were happy to gorge SPAWNING themselves on certain foods. The second month is a great time to focus on getting your filefish to accept additional At the culmination of courtship, the male and female foods for a more varied diet. press their abdomens up against the patch of algae and By the two-month mark, your filefish should be re- release gametes. The female deposits a few hundred ad- storing lost body fat. It is probably willing to feed from hesive, translucent green eggs, approximately 0.8 mm in the water column and chase down food. You should feel diameter. The pair chooses a different spawning location comfortable introducing the fish to a permanent home. every day. If you do not actually witness the spawn, you If it is going into a community reef, be sure its tankmates may never know where the eggs were laid. are relatively docile and not likely to harass the filefish. EGG COLLECTION AND INCUBATION Do not be surprised if the fish stops feeding for a day or two following the move. At this point, you are likely des- I should mention that with my pair, I tried using artificial tined for a long-term relationship with your Harlequin yarn spawning mops (like the ones I used when breed- Filefish. This is also the point at which you might turn ing Tanganyikan Killifish, Lamprichthys tanganicanus), your attention to breeding them. but the filefish ignored them, preferring real algae for a spawning site. Therefore, I use a turkey baster to col- BREEDING THE HARLEQUIN FILEFISH lect the eggs, sucking them out of the algae and deposit- It took about six months for my first pair of Harlequin ing them in a half-gallon (2-L) specimen container (the Filefish to start spawning. Spawning was sporadic at first, type of container typically used at aquarium stores for but it’s now a daily occurrence. Mating currently oc- holding fish between netting and bagging). I hang this curs around dinnertime (5:00 to 6:00 P.M.) in my pair, container in a 10-gallon (38-L) aquarium to keep the which is maintained at 80ºF (26.6ºC) and has “lights water temperature stable, around 82ºF (28ºC). I use a out” at 10:30 P.M. slow drip of water from the larval tank over the next 48 Observations in the wild note that mating can occur hours to keep the water quality stable, and turn off this at any point in the day and is directly influenced by wa- slow feed shortly before hatching. ter temperature. Cooler temperatures cause spawning to HATCHING occur in the morning; as temperatures warm, spawning times shift to later in the day or into the evening. This Harlequin Filefish hatch around 50–56 hours after shift in mating time accounts for larval development spawning, starting life as primitive prolarvae. A prolarva times at different temperatures and ensures the proper has no eyes, mouth, gut, or gills at hatching; it is basi- hatching time. This means that your fish could start cally a 2.5-mm spinal cord with a bright green yolk sac. spawning in the middle of the day and you’d never know it. So remember, warmer temperatures push spawning time closer to dusk.

COURTSHIP Courtship can last only a few minutes, or it can start hours prior to mating. Courtship in Harlequin Filefish consists of a broad array of behaviors and displays, but I’ll highlight only the two most noticeable here. The female partakes in an “algae ramming” or “thrusting” behavior, where she looks at a patch of algae (typically Red Gracilaria in my tank) and then rams her face into it. The male (and to a lesser extent, the female) engages in a display called a “flutter dive,” consisting of the fish swimming forward and downward, rapidly opening and closing the tail. The male’s dorsal and anal fins become

Right: The act of spawning, male in foreground, with the pair side-by-side depositing eggs and milt in the bed of macroalgae. Spawn events can occur daily and are accomplished in the span of seconds, never twice in the same spot.

CORAL 71 LARVAL REARING and Rotifer Diet products) has been used successfully. After hatching, I transfer the larvae into the rearing ves- (See Matthew Wittenrich’s Complete Illustrated Breeders sel, technically known as a kreisel. The goal is to pro- Guide to Marine Aquarium Fishes for more on greenwater vide very weak currents that keep larvae from bunching technique.) In all my rearing attempts, I allowed a popu- up and food items in suspension. A properly operating lation of Tisbe spp. copepods (available from Phyto2) to kreisel creates a scenario where the larval fish behave develop in the rearing vessels. These copepods may be like trout in a stream, maintaining a stationary position providing nauplii as a secondary food source. The known facing into the current, picking off prey items as they starvation point for Harlequin Filefish larvae is at five float by. This minimizes the energy expended in feeding. days post-hatch. If the larvae live longer than five days, Whether driven by air or by water, the flow must be ad- you are having some feeding success. So far, all my rear- justable to create the proper level of current. ing attempts have included 24-hour lighting until the I’ve had good luck using a 2-gallon (7.5-L) plastic fourth week, with “nighttime” first being simulated by fishbowl suspended in a 10-gallon (38-L) aquarium for reducing light, not completely eliminating it, until the temperature control. My first successes utilized an air fish are post-settlement. feed to create the circulation within the bowl. Daily par- The larvae continue to feed on enriched rotifers all tial water changes from the bowl ensured stable water the way to three weeks of age. At 21 days, the larvae are parameters. More recently, I’ve modified the fishbowl to laterally compressed and have surprisingly long black allow for flowthrough from the tank around it, ensuring dorsal spines that are almost 50 percent of the total body more stable water quality. length. The face is flat, with a tiny mouth reminiscent Within the first 48 hours following hatching, the of a parrot’s beak. Twenty-one days seems to be an ideal prolarvae rapidly develop into functional fish. The eyes, time to introduce newly hatched brine shrimp nauplii mouth, gut, rudimentary fins, and even the beginnings to the diet, while continuing to offer enriched rotifers of the dorsal spine form. The larvae start feeding around until they are no longer preyed upon. So far, I’ve only 50–65 hours after hatching. For first feedings, the green- managed to bring three larvae to this point in the rearing water technique combining live rotifers with phytoplank- process, so the following details are based on relatively ton (in my first attempts, Reef Nutrition’s Phytofeast limited experiences.

Adhesive Harlequin Filefish eggs in a tangle of red and green macroalgae, ready to be removed with a turkey baster for hatching in a separate vessel. TK

72 CORAL Clockwise, from top left: [1] Prolarva in a drop of water, with its own shadow and bright green yolk sac. [2] Larval filefish at about 13 days of age, with characteristic dorsal spine already raised. [3] A 41-day-old filefish with belly full of baby brine shrimp. [4] Color patterns emerging at 48 days. Note live brine shrimp nauplii. [5] At 51 days, juvenile in later stages of metamorphosis, starting to show signs of adult blue and bright yellow coloration. The author recommends introducing prepared micro pellets between days 28 and 35.

It seems that Harlequin Filefish larvae should be the pre-settlement, late-stage larvae start to exhibit a weaned onto prepared foods starting at 28 days post- lavender hue. They are now showing more of the char- hatch. Crushed Spirulina flake foods and Otohime A (a acteristic adult form, but the nose is still lengthening. marine larval rearing pellet available from Reef Nutri- By the beginning of the sixth week, around day 42, the tion) are two ideal foods. Weaning seems to be most suc- first hints of adult coloration may be seen, and the fish cessful at this age, and also produces better growth. At now have the final adult body shape. By the start of the five weeks, if the fish can be kept fat and growing solely seventh week, the first hints of blue may be seen, and on prepared food, there is no longer a need for or advan- by the end of the seventh week, full adult coloration is tage to continuing to feed baby brine shrimp. clearly visible. Right around this time, settlement occurs. In the middle of the fifth week, around day 38/39, This was when I first observed a juvenile resting on the

CORAL 73 substrate in the morning—I feared the worst, until I real- ized they had simply started sleeping at night.

A NEW FUTURE FOR HARLEQUIN FILEFISH At this stage, with admittedly limited success, I am noth- ing but optimistic about this species being routinely bred and raised in captivity. I did lose the first baby I brought through settlement at the age of 93 days. This little fish was introduced to prepared foods rather late in the rear- ing process. It never fully weaned onto prepared foods and wanted only baby brine shrimp, a diet that eventu- ally left it malnourished and stunted. The second two offspring are alive and well at the time of this writing and have eaten nothing but crushed flake food and Otohime for months. At almost four months of age, the oldest baby is around 1.25 inches (3.2 cm) in total length and could be considered mar- ket size, or close to it. Subsequent rearing attempts have yielded improved early larval survival, only to fail when my rotifer cultures started to crash. I am confident that At 54 days, this tiny filefish is approaching my own future attempts will continue to yield larger settlement, when it will move to the reef numbers of juvenile fish. substrate and abandon its purely pelagic life. I hope that the lessons I’ve learned will help change the fate of the Harlequin Filefish in home aquariums. Ideally, wild-caught specimens will get into the hands of experienced hobbyists who are better prepared to meet their needs. (Again, please don’t buy this fish if you are Just Published!

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74 CORAL not ready to keep it alive.) If more breeders take up the challenge, captive-bred Harlequin Filefish could become available within the hobby and should suf- fer none of the feeding problems that make their wild-caught counterparts so difficult to keep. What is currently thought of as a doomed species could be- come one of our next bread-and-butter fish, thanks to the benefits of small-scale aquaculture. One of the first captive-bred There may even be conservation benefits to hav- Oxymonacanthus longistris ing a successful protocol for keeping and rearing known to survive past the Oxymonacanthus longirostris in captive conditions. larval stage. This is a juvenile Harlequin Filefish are one of the first fish to disap- raised by the author, at about 15 weeks pear following coral reef bleaching events. As more post-hatch. coral reefs die off, more Harlequin Filefish popula- tions disappear. I hope we can ensure the survival of this species in captivity, as a genetic repository, if it becomes threatened in the wild.

Matt Pedersen is a software developer and fly-fishing guide residing in Chicago, Illinois. He has been a marine aquarist for 22 years and has spawned 16 species of marine fish to date, successfully raising five of them, all with less than 100 gallons of total working capacity. Matt is the co-founder of MOFIB (Marine Ornamental Fish and Invertebrate Breed- ers’ Association).

ON THE INTERNET

Acreichthys tomentosus (Filefish) breeding as posted by Iris Bönig: http:// www.marinebreeder.org/phpbb/ viewtopic.php?t=116 Oxymonacanthus longirostris Breeding Log (Survival Log) as posted by Matt Pedersen: http://www.marinebreeder. org/phpbb/viewtopic.php?t=1922 Breeder’s Registry Anonymous Spawning Report for Oxymonacanthus longirostris reported on 7/7/1994: http://www.breedersregistry.org/ database/OXYLON01.htm

REFERENCES

Barlow, George W. 1987. Spawning, eggs and larvae of the longnose filefishOxymonacanthus longirostris, a monogamous corallivore. Environ Biol Fishes 20(3): 183-194. Kokita, T. and A. Nakazono. 2000. Seasonal variation in the diel spawning time of the coral reef fishOxymonacanthus longirostris (Monacanthidae): parental control of progeny development. Mar Ecol Prog Ser 199: 263-270. —2001. Rapid response of an obligately corallivorous filefishOxymonacanthus longirostris (Monacanthidae) to a mass coral bleaching event. Coral Reefs 20: 155–158.

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