Jay Hemdal
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This thread is for the general discussion of the Article Batfish and Spadefish. Please add to the discussion here.
Chaetodipterus lippei – West African spadefish
Ephippus goreensis – East Atlantic African spadefish
Ephippus orbis – Orbfish
Parapsettus panamensis – Panama spadefish
Platax boersii – Golden batfish (unless misidentified as another species)
Proteracanthus sarissophorus – no common name
Rhinoprenes pentanemus Threadfin “scat”
Tripterodon orbis – African spadefish
Zabidius novemaculeatus – Ninespine batfish
Nine batfish species not normally encountered in the pet trade
Husbandry
Batfish are best suited for larger, fish-only marine aquariums. Although not normally considered aggressive, their bulky size and frenetic swimming can wreak havoc in miniature reef aquariums. Adult batfish can be kept with many other species, from damselfish to lionfish and groupers. Batfish will rarely attack their tankmates, and all but the most aggressive species (such as some triggerfish) will leave them alone. The long fins of juvenile batfish are sometimes a tempting target for small territorial angels and damselfish. If the aggression is not too severe, the batfish will quickly re-grow their torn fins.
The following are some general recommendations for selecting a batfish or spadefish to purchase:
Search for a small to medium specimen. Both the largest and the very smallest individuals may have difficulty adapting to captivity. It might be best to avoid batfish collected in the Philippines, as, due to poor collection and handling practices, some batfish arriving from that region are not as sturdy as the same species from other regions. Don’t forget that if you are successful at acquiring a healthy young batfish, your fish will eventually grow large and will lose much of the color and grace that attracted you to it in the first place.
Avoid any batfish that is “ADR” (Ain’t Doin’ Right) in any respect. Folded dorsal and anal fins are a bad sign, as is any severe damage to the fins themselves. Pinnatus batfish in particular seem very prone to external secondary bacterial infections brought about by physical trauma.
See the fish eat at the pet store before you buy it. A healthy batfish will feed actively, chasing after food up to 4" away. Avoid a fish that only eats food which drifts right in front of its snout or one that attempts to feed but then spits the food back out.
Quarantine your new batfish before adding it to your display aquarium. Methods for this vary, but a minimum quarantine would be to keep the fish for two weeks in isolation with proper preventative treatments for protozoans and flukes. Many aquarists find that a six-week quarantine period, although more labor intensive, is much better at protecting their existing fish from diseases brought in by new animals.
Disease issues
With two exceptions, once properly quarantined and adapted to captivity, batfish are remarkably hardy. One exception is the red-rimmed batfish that is well known for being difficult to adapt to captivity. The second exception is this group’s overall predisposition to developing trematode (fluke) infestations, particularly Neobenedinia melleni. It may be that the batfish’s hardy nature actually makes this fluke problem more serious. In most fish, once they have been infected by a few flukes, they develop cloudy eyes and begin flashing or scraping their sides in the aquarium. Batfish on the other hand withstand these minor infestations, and do not begin showing symptoms until they are very heavily infected. Once they reach this stage, flukes are much more difficult to eradicate. Therefore, while batfish do succumb to fluke infestations more often than some other species, it may be because they are so sturdy that they hide the early symptoms very well. A simple diagnostic dip can be used to identify fluke infestations in batfish. Fill a suitably sized container with tap water at the same temperature and pH as the aquarium. Capture the batfish in a soft net and place it in the container of water, taking care not to let anything else like gravel or bits of algae get into the container. Watch the fish carefully for five minutes, and then gently transfer the fish back to the aquarium. Let the water in the container settle out and pour all but an inch or so of the bottom layer down a drain. Take the remaining water, pour it into a smaller container and let it settle out again. Using a pipette, capture any detritus or other material you can see on the bottom of the second container, and move it to a third, even smaller container, such as a watch glass. Then, using a dissecting microscope or even a strong magnifying glass, search the material for any dead trematodes. Neobenedenia melleni will look like whitish flattened ovals, very much like loose fish scales. Gill flukes and other species of skin flukes will be harder to detect as the fresh water may have distorted their bodies. Look for little pieces of protoplasm that have up to four distinct black spots (the eyes).
There are many remedies available for treating flukes, but all have some drawback to their use. Copper is generally not very effective. Freshwater dips, while removing many flukes from the body of the fish, do nothing for fluke eggs or young flukes existing in the aquarium itself. Trichlorfon (Dylox) is very toxic to humans, and some fish are sensitive to it. Praziquantel (Droncit) is widely recommended, but it is expensive and difficult to obtain. A series of four 150 parts per million (ppm) formalin baths of the entire aquarium, spaced one week apart, works well, but a large amount of replacement water is needed to dilute the formalin after each treatment. Additionally, formalin poses serious human health concerns. Some aquarists merely work at controlling fluke infestations. Fluke outbreaks seem to be seasonal, and many fish eventually develop a resistance to them. Giving the affected fish five-minute freshwater dips every week or so may hold the flukes at bay long enough for either the season to pass or the fish to develop a resistance to them. Frequent siphon cleaning of the aquarium’s gravel may help to remove fluke eggs or young flukes of the livebearing species.
Species accounts
Platax orbicularis – Orbicularis batfish, narrowbanded batfish, sicklefish
The most commonly seen species in pet stores, Orbicularis batfish are generally not well suited for small home aquariums as they can reach a length of 20 inches (50 cm), although 16” is more common as a maximum length of this species in captivity. Widespread throughout the Indo-Pacific region, they even range north to Japan and west into the Red Sea. The tiny juveniles are mimics of brown plant leaves, probably a species of mangrove tree. They take this mimicry to the point of developing white spots that resemble the fungal growth that makes small holes in dead leaves. Even their behavior matches that of this plant material, floating sidewise and allowing the waves to wash them back and forth.
Platax pinnatus – Pinnatus batfish, red-rimmed batfish, dusky batfish, longfin batfish
Pinnatus batfish are reported to reach a length of 18” (45cm), although captive individuals are always much smaller. This species is found in the Western Pacific Ocean from Southern Japan to Australia. They do best if kept by themselves in a tall, dimly lit aquarium with few decorations. Be prepared to offer your fish live adult brine shrimp fortified with Selco (or other nutrients) as a starter food. When the fish seems willing, begin adding small krill, live guppies and gelatin foods to its diet. Many individuals of this species refuse all food in captivity, and very few specimens survive more than three months in an aquarium. This is definitely a species for advanced aquarists only. Purchase the smallest fish you can find and keep it in an aquarium by itself until it has settled in and is eating well. Captive raised juveniles have been sporadically available from Indonesia and these are a bit hardier.
Platax tiera – Tiera batfish, longfin batfish, roundface batfish
The Tiera is the largest batfish, reaching 28” (70cm) in the wild. Although wide ranging throughout the Indo-Pacific and the Red Sea, it is not quite as common as the Orbicularis batfish. The extremely long fins of juveniles of this species are unique among fish. As they grow, the size of these fins lessens in relation to the animal’s body size until, as adults, they look very similar to Orbicularis batfish. Normally very hardy, just avoid very small Tiera batfish that are too emaciated from their collection and transport to survive well in your aquarium. Some juvenile “tiera batfish” sold in the trade may actually be a closely related species, the Golden batfish, Platax boersii. This species differs just slightly in coloration (tending to be lighter colored) and in having one less dorsal spine. There is also the possibility that these two species are actually the same, and the color variation simply is due to environmental differences in the areas where the fish are living. Based on the habits of other members of this group, it is likely that juvenile Tiera batfish are also active mimics, but until their model is identified, this cannot be confirmed. They may just be general mimics of floating leaves or other plant debris, but that does not adequately explain their long fins. Another fish that has fantastic fin extensions as a juvenile, the African pompano (Alectis ciliaris) is an active mimic of a pelagic jellyfish. Nature does not create extreme coloration or bizarre forms in animals for no reason, and it is likely that the elongated fins of the Tiera batfish serve some similar function in terms of mimicry.
Platax batavianus – Tiger batfish, Batavia batfish, humpback/humphead batfish
Reported to grow to 20” (50cm), is found sporadically throughout the West Indo-Pacific region. Juveniles are found in deep water, often associated with (and possibly feeding on) crinoids (Kuiter 1996). The distinct color pattern of small specimens combined with this association indicates that they are probably mimicking the unpalatable crinoid as a protection against predators. There are few husbandry reports from aquarists keeping this species. They are probably hardier than Pinnatus batfish, but perhaps a bit more delicate than Tiera batfish.
Chaetodipterus faber – Atlantic spadefish
Reaching three feet (91cm) in length, this species is really only appropriate to be kept by public aquariums. Found in the temperate and tropical regions of the Atlantic Ocean, adults form large schools while the juveniles float close to shore and mimic leaves and other plant debris both by their color and their swimming motion. The Tulsa Zoo has reproduced spadefish in captivity (Walker 1991). The 1.2mm eggs hatched in 24 hours. Two days after hatching, the larva became free-swimming and started to feed on Brachionus rotifers and Chlorella algae. Nine days after hatching the fry began to accept Artemia nauplii.
Chaetodipterus zonatus – Pacific spadefish
Ranging from San Diego south to Peru in the Eastern Pacific, this species is occasionally collected and sold to aquarists. Reaching 25” (65cm), it is slightly smaller than the Atlantic Spadefish but is very similar in all other respects. Both species seem prone to Cryptocaryon (saltwater ick) infections, and although they tolerate copper treatments well, the disease is sometimes difficult to treat with these fish.
Mimicry in Pinnatus Batfish
The natural history of the red-rimmed batfish is not very well known. However, it has been reported that juveniles are active mimics of toxic turbellarian flatworms of the genus Pseudoceros or Callioplana (Randall & Emery 1971). These poisonous flatworms glide openly across the face of the reef with relative impunity from predators. The red-rimmed batfish has a color scheme similar to these worms (Gosliner, et-al 1996), but its vertical swimming motion is obviously not the same. However, these batfish show very little shyness even with people moving around outside its tank. Most easily preyed-upon, small fish are wary of any movement outside the aquarium that might be threatening. Either these fish are exceedingly dull-witted, or they have some other plan to avoid predators. Deciding to test the hypothesis that these fish are active mimics, I placed a net in a tank housing a small pinnatus batfish and touched it against the fish. This resulted in a surprising reaction. Instead of swimming away, the batfish immediately turned itself horizontal, draped its body over a large rock and held very still. It sure looked more like a flatworm now! I removed the net from the aquarium, and it took a full five minutes before the batfish began swimming normally. I tried the net ruse again. This time the batfish immediately fell prostrate to the floor of the aquarium and lay there for ten minutes. During this time, the pale gray body stripe darkened to match the jet-black color of the rest of the fish (as well as the solid black color of the poisonous flatworm). This was enough to convince me that these batfish are indeed active mimics of one of the toxic flatworms (Hemdal 1997).
Fish releases
With the potential size of adult batfish and spadefish in aquariums being so large, aquarists who buy one need to consider which steps they will take when the fish outgrow their aquariums. Purchasing a larger aquarium is certainly an option. Returning the fish to a pet store might also be a solution, although most stores do not have aquariums much larger than that of home aquarists and are usually unable to take back the grown fish they sell as juveniles. Donating it to a public aquarium might be an alternative except that batfish are such long-lived creatures; aquariums usually have enough of these fish for their exhibits. More often, public aquariums are using the very structured Institutional Collection Plan (ICP) process to choose the animals for their exhibits. While this results in exhibits that house the best possible diversity of species for their visitors, it does not allow much in the way of a “fudge factor,” where you can call up a public aquarium and try to talk them into taking your over-sized batfish. These collection plans only work if they are followed, and since your batfish is not likely to be in the plan, the aquarium will not be able to accept it. Not buying a species that you know you will be unable to care for when it reaches adult size is certainly the most prudent course of action. Some people have resorted to euthanizing their over-sized fish out of desperation, not being able to find a better home for it.
One option that must never be considered is releasing the animal to the wild. Captive fish, used to the confines of a home aquarium, are unlikely to survive in the wild. The aquarist is not usually able to identify which aquatic habitat would be best for the fish and may just release the fish into the water regardless of the habitat. Fish released into the wild may harbor exotic diseases that they acquired while in captivity. These diseases might then infect native populations of fish, potentially causing an epidemic. Finally, if the released fish does manage to survive, and meets up with another released member of the opposite sex, reproduction may occur. This has already occurred with venomous Indo-Pacific lionfish released into the Atlantic Ocean either by thoughtless aquarists or, as rumor has it, when a hurricane damaged a coastal fish importation facility. The invasion of a new species always causes damage to the environment in some way. Zebra mussels, round gobies and carp are all introduced aquatic species that caused major damage to their non-native environments. The sidebar lists species of Pacific marine fish that have been observed in the Western Atlantic. Without exception, these fish found their way into this area at the hand of aquarists. Well-meaning but misinformed hobbyists just looking for a home for their over-grown fish probably released the species listed in bold (including batfish). The presence of the other species is a bit of an enigma. It is not very difficult to find a home for your unwanted royal gramma, purple tang or adult emperor angelfish. Why are there a disproportionate number of expensive, highly sought-after Red Sea fish being found in the Atlantic? There is one likely explanation; somebody was releasing these fish with the intent of producing local populations that could then be exploited by the pet trade. Rumors have persisted for many years of fish collectors releasing royal grammas into Florida waters in an attempt to establish a breeding population of these fish that are not native to the area. It is likely that some fish dealer had an assortment of Red Sea fish and then released them in the Atlantic Ocean north of Fort Lauderdale in the hopes of being able to come back later and collect their offspring. This activity gives a tremendous “black eye” to the aquarium hobby, and it is illegal and must stop. Not all fish dealers are part of the problem. One collector in the Florida Keys actually helped round up a stray batfish that had been living on an offshore reef.
Exotic fish species reported from U.S. coastal waters.
Chaetodon fasciatus – Red Sea raccoon butterflyfish
Cromileptes altivelis – Panther grouper
Gramma loreto – Royal gramma
Naso lituratus – Naso tang
Platax orbicularis – Orbicularis batfish
Pomacanthus annularis – Bluering angelfish
Pomacanthus asfur – Arabian angelfish
Pomacanthus imperator – Emperor angelfish
Pomacanthus maculosus – Yellowbar angelfish
Pomacanthus semicirculatus – Koran angelfish
Pomacanthus xanthometopon – Blueface angelfish
Pterois volitans – Black lionfish
Rhinecanthus verrucosus – Bursa triggerfish
Zanclus cornutus – Moorish idol
Zebrasoma desjardinii – Red Sea sailfin tang
Zebrasoma flavescens – Yellow tang
Zebrasoma veliferum – Sailfin tang
Zebrasoma xanthurum – Purple tang
References:
Bullard, S.A., Benz, G.W., Overstreet, R.M., Williams Jr., E.H. and Hemdal, J.F. 2000. Six new host records and an updated list of wild hosts for Neobenedenia melleni (MacCallum) (Monogenea: Capsalidae). Comparative Parasitology 67(2):190-196
Gosliner, T.M., Behrens, D.W. & Williams, G.C. 1996. Coral reef animals of the Indo-Pacific. Sea Challengers Monterey, CA
Hemdal, J.F. 1997. The red-rimmed batfish - revisited. Aquarium Frontiers On-Line
Hemdal, J.F. 1985. The pinnatus batfish: force-feeding, a new idea for maintaining this species? Freshwater and Marine Aquarium 8(10):18.
Kuiter, Rudie H. 1996. Guide to Sea Fishes of Australia. New Holland Publishers, Australia
Randall, J.E. & Emery, A.R. 1971. On the resemblance of the young of the fishes Platax pinnatus and Plectorhynchus chaetodontoides to flatworms and nudibranchs. New York Zoological Society, Zoologica 56(3) 115-119
Batfish and Spadefish in Aquariums
Jay Hemdal
Batfish and spadefish, especially juvenile specimens, have been popular with home aquarists ever since the early days of marine fish importations from the Philippine Islands in the late 1950’s. During the 1970’s three species of batfish were commonly seen in pet stores: Platax orbicularis, Platax tiera and Platax pinnatus. Juvenile spadefish, Chaetodipterus faber and C. zonatus are also occasionally collected by home aquarists for display in their aquariums. Importation of a fourth species, Platax batavianus, has occurred sporadically since the late 1980’s. The taxonomy of this group of fish has been in a state of flux, but most biologists now agree there are fifteen members of the batfish family, Ephippidae. The nine other batfish species that rarely, if ever, enter the pet trade are listed in the sidebar. There is another group of fish known as batfish that share the same common name but belong to an unrelated family, the Ogcocephalidae. These walking batfish are quite different in their habits, being bottom dwelling fish that rely on their modified fins to walk along the bottom. While interesting in their own right, walking batfish can sometimes be difficult to feed and are prone to a variety of internal parasitic infections.Jay Hemdal
Chaetodipterus lippei – West African spadefish
Ephippus goreensis – East Atlantic African spadefish
Ephippus orbis – Orbfish
Parapsettus panamensis – Panama spadefish
Platax boersii – Golden batfish (unless misidentified as another species)
Proteracanthus sarissophorus – no common name
Rhinoprenes pentanemus Threadfin “scat”
Tripterodon orbis – African spadefish
Zabidius novemaculeatus – Ninespine batfish
Nine batfish species not normally encountered in the pet trade
Husbandry
Batfish are best suited for larger, fish-only marine aquariums. Although not normally considered aggressive, their bulky size and frenetic swimming can wreak havoc in miniature reef aquariums. Adult batfish can be kept with many other species, from damselfish to lionfish and groupers. Batfish will rarely attack their tankmates, and all but the most aggressive species (such as some triggerfish) will leave them alone. The long fins of juvenile batfish are sometimes a tempting target for small territorial angels and damselfish. If the aggression is not too severe, the batfish will quickly re-grow their torn fins.
The following are some general recommendations for selecting a batfish or spadefish to purchase:
Search for a small to medium specimen. Both the largest and the very smallest individuals may have difficulty adapting to captivity. It might be best to avoid batfish collected in the Philippines, as, due to poor collection and handling practices, some batfish arriving from that region are not as sturdy as the same species from other regions. Don’t forget that if you are successful at acquiring a healthy young batfish, your fish will eventually grow large and will lose much of the color and grace that attracted you to it in the first place.
Avoid any batfish that is “ADR” (Ain’t Doin’ Right) in any respect. Folded dorsal and anal fins are a bad sign, as is any severe damage to the fins themselves. Pinnatus batfish in particular seem very prone to external secondary bacterial infections brought about by physical trauma.
See the fish eat at the pet store before you buy it. A healthy batfish will feed actively, chasing after food up to 4" away. Avoid a fish that only eats food which drifts right in front of its snout or one that attempts to feed but then spits the food back out.
Quarantine your new batfish before adding it to your display aquarium. Methods for this vary, but a minimum quarantine would be to keep the fish for two weeks in isolation with proper preventative treatments for protozoans and flukes. Many aquarists find that a six-week quarantine period, although more labor intensive, is much better at protecting their existing fish from diseases brought in by new animals.
Disease issues
With two exceptions, once properly quarantined and adapted to captivity, batfish are remarkably hardy. One exception is the red-rimmed batfish that is well known for being difficult to adapt to captivity. The second exception is this group’s overall predisposition to developing trematode (fluke) infestations, particularly Neobenedinia melleni. It may be that the batfish’s hardy nature actually makes this fluke problem more serious. In most fish, once they have been infected by a few flukes, they develop cloudy eyes and begin flashing or scraping their sides in the aquarium. Batfish on the other hand withstand these minor infestations, and do not begin showing symptoms until they are very heavily infected. Once they reach this stage, flukes are much more difficult to eradicate. Therefore, while batfish do succumb to fluke infestations more often than some other species, it may be because they are so sturdy that they hide the early symptoms very well. A simple diagnostic dip can be used to identify fluke infestations in batfish. Fill a suitably sized container with tap water at the same temperature and pH as the aquarium. Capture the batfish in a soft net and place it in the container of water, taking care not to let anything else like gravel or bits of algae get into the container. Watch the fish carefully for five minutes, and then gently transfer the fish back to the aquarium. Let the water in the container settle out and pour all but an inch or so of the bottom layer down a drain. Take the remaining water, pour it into a smaller container and let it settle out again. Using a pipette, capture any detritus or other material you can see on the bottom of the second container, and move it to a third, even smaller container, such as a watch glass. Then, using a dissecting microscope or even a strong magnifying glass, search the material for any dead trematodes. Neobenedenia melleni will look like whitish flattened ovals, very much like loose fish scales. Gill flukes and other species of skin flukes will be harder to detect as the fresh water may have distorted their bodies. Look for little pieces of protoplasm that have up to four distinct black spots (the eyes).
There are many remedies available for treating flukes, but all have some drawback to their use. Copper is generally not very effective. Freshwater dips, while removing many flukes from the body of the fish, do nothing for fluke eggs or young flukes existing in the aquarium itself. Trichlorfon (Dylox) is very toxic to humans, and some fish are sensitive to it. Praziquantel (Droncit) is widely recommended, but it is expensive and difficult to obtain. A series of four 150 parts per million (ppm) formalin baths of the entire aquarium, spaced one week apart, works well, but a large amount of replacement water is needed to dilute the formalin after each treatment. Additionally, formalin poses serious human health concerns. Some aquarists merely work at controlling fluke infestations. Fluke outbreaks seem to be seasonal, and many fish eventually develop a resistance to them. Giving the affected fish five-minute freshwater dips every week or so may hold the flukes at bay long enough for either the season to pass or the fish to develop a resistance to them. Frequent siphon cleaning of the aquarium’s gravel may help to remove fluke eggs or young flukes of the livebearing species.
Species accounts
Platax orbicularis – Orbicularis batfish, narrowbanded batfish, sicklefish
The most commonly seen species in pet stores, Orbicularis batfish are generally not well suited for small home aquariums as they can reach a length of 20 inches (50 cm), although 16” is more common as a maximum length of this species in captivity. Widespread throughout the Indo-Pacific region, they even range north to Japan and west into the Red Sea. The tiny juveniles are mimics of brown plant leaves, probably a species of mangrove tree. They take this mimicry to the point of developing white spots that resemble the fungal growth that makes small holes in dead leaves. Even their behavior matches that of this plant material, floating sidewise and allowing the waves to wash them back and forth.
Platax pinnatus – Pinnatus batfish, red-rimmed batfish, dusky batfish, longfin batfish
Pinnatus batfish are reported to reach a length of 18” (45cm), although captive individuals are always much smaller. This species is found in the Western Pacific Ocean from Southern Japan to Australia. They do best if kept by themselves in a tall, dimly lit aquarium with few decorations. Be prepared to offer your fish live adult brine shrimp fortified with Selco (or other nutrients) as a starter food. When the fish seems willing, begin adding small krill, live guppies and gelatin foods to its diet. Many individuals of this species refuse all food in captivity, and very few specimens survive more than three months in an aquarium. This is definitely a species for advanced aquarists only. Purchase the smallest fish you can find and keep it in an aquarium by itself until it has settled in and is eating well. Captive raised juveniles have been sporadically available from Indonesia and these are a bit hardier.
Platax tiera – Tiera batfish, longfin batfish, roundface batfish
The Tiera is the largest batfish, reaching 28” (70cm) in the wild. Although wide ranging throughout the Indo-Pacific and the Red Sea, it is not quite as common as the Orbicularis batfish. The extremely long fins of juveniles of this species are unique among fish. As they grow, the size of these fins lessens in relation to the animal’s body size until, as adults, they look very similar to Orbicularis batfish. Normally very hardy, just avoid very small Tiera batfish that are too emaciated from their collection and transport to survive well in your aquarium. Some juvenile “tiera batfish” sold in the trade may actually be a closely related species, the Golden batfish, Platax boersii. This species differs just slightly in coloration (tending to be lighter colored) and in having one less dorsal spine. There is also the possibility that these two species are actually the same, and the color variation simply is due to environmental differences in the areas where the fish are living. Based on the habits of other members of this group, it is likely that juvenile Tiera batfish are also active mimics, but until their model is identified, this cannot be confirmed. They may just be general mimics of floating leaves or other plant debris, but that does not adequately explain their long fins. Another fish that has fantastic fin extensions as a juvenile, the African pompano (Alectis ciliaris) is an active mimic of a pelagic jellyfish. Nature does not create extreme coloration or bizarre forms in animals for no reason, and it is likely that the elongated fins of the Tiera batfish serve some similar function in terms of mimicry.
Platax batavianus – Tiger batfish, Batavia batfish, humpback/humphead batfish
Reported to grow to 20” (50cm), is found sporadically throughout the West Indo-Pacific region. Juveniles are found in deep water, often associated with (and possibly feeding on) crinoids (Kuiter 1996). The distinct color pattern of small specimens combined with this association indicates that they are probably mimicking the unpalatable crinoid as a protection against predators. There are few husbandry reports from aquarists keeping this species. They are probably hardier than Pinnatus batfish, but perhaps a bit more delicate than Tiera batfish.
Chaetodipterus faber – Atlantic spadefish
Reaching three feet (91cm) in length, this species is really only appropriate to be kept by public aquariums. Found in the temperate and tropical regions of the Atlantic Ocean, adults form large schools while the juveniles float close to shore and mimic leaves and other plant debris both by their color and their swimming motion. The Tulsa Zoo has reproduced spadefish in captivity (Walker 1991). The 1.2mm eggs hatched in 24 hours. Two days after hatching, the larva became free-swimming and started to feed on Brachionus rotifers and Chlorella algae. Nine days after hatching the fry began to accept Artemia nauplii.
Chaetodipterus zonatus – Pacific spadefish
Ranging from San Diego south to Peru in the Eastern Pacific, this species is occasionally collected and sold to aquarists. Reaching 25” (65cm), it is slightly smaller than the Atlantic Spadefish but is very similar in all other respects. Both species seem prone to Cryptocaryon (saltwater ick) infections, and although they tolerate copper treatments well, the disease is sometimes difficult to treat with these fish.
Mimicry in Pinnatus Batfish
The natural history of the red-rimmed batfish is not very well known. However, it has been reported that juveniles are active mimics of toxic turbellarian flatworms of the genus Pseudoceros or Callioplana (Randall & Emery 1971). These poisonous flatworms glide openly across the face of the reef with relative impunity from predators. The red-rimmed batfish has a color scheme similar to these worms (Gosliner, et-al 1996), but its vertical swimming motion is obviously not the same. However, these batfish show very little shyness even with people moving around outside its tank. Most easily preyed-upon, small fish are wary of any movement outside the aquarium that might be threatening. Either these fish are exceedingly dull-witted, or they have some other plan to avoid predators. Deciding to test the hypothesis that these fish are active mimics, I placed a net in a tank housing a small pinnatus batfish and touched it against the fish. This resulted in a surprising reaction. Instead of swimming away, the batfish immediately turned itself horizontal, draped its body over a large rock and held very still. It sure looked more like a flatworm now! I removed the net from the aquarium, and it took a full five minutes before the batfish began swimming normally. I tried the net ruse again. This time the batfish immediately fell prostrate to the floor of the aquarium and lay there for ten minutes. During this time, the pale gray body stripe darkened to match the jet-black color of the rest of the fish (as well as the solid black color of the poisonous flatworm). This was enough to convince me that these batfish are indeed active mimics of one of the toxic flatworms (Hemdal 1997).
Fish releases
With the potential size of adult batfish and spadefish in aquariums being so large, aquarists who buy one need to consider which steps they will take when the fish outgrow their aquariums. Purchasing a larger aquarium is certainly an option. Returning the fish to a pet store might also be a solution, although most stores do not have aquariums much larger than that of home aquarists and are usually unable to take back the grown fish they sell as juveniles. Donating it to a public aquarium might be an alternative except that batfish are such long-lived creatures; aquariums usually have enough of these fish for their exhibits. More often, public aquariums are using the very structured Institutional Collection Plan (ICP) process to choose the animals for their exhibits. While this results in exhibits that house the best possible diversity of species for their visitors, it does not allow much in the way of a “fudge factor,” where you can call up a public aquarium and try to talk them into taking your over-sized batfish. These collection plans only work if they are followed, and since your batfish is not likely to be in the plan, the aquarium will not be able to accept it. Not buying a species that you know you will be unable to care for when it reaches adult size is certainly the most prudent course of action. Some people have resorted to euthanizing their over-sized fish out of desperation, not being able to find a better home for it.
One option that must never be considered is releasing the animal to the wild. Captive fish, used to the confines of a home aquarium, are unlikely to survive in the wild. The aquarist is not usually able to identify which aquatic habitat would be best for the fish and may just release the fish into the water regardless of the habitat. Fish released into the wild may harbor exotic diseases that they acquired while in captivity. These diseases might then infect native populations of fish, potentially causing an epidemic. Finally, if the released fish does manage to survive, and meets up with another released member of the opposite sex, reproduction may occur. This has already occurred with venomous Indo-Pacific lionfish released into the Atlantic Ocean either by thoughtless aquarists or, as rumor has it, when a hurricane damaged a coastal fish importation facility. The invasion of a new species always causes damage to the environment in some way. Zebra mussels, round gobies and carp are all introduced aquatic species that caused major damage to their non-native environments. The sidebar lists species of Pacific marine fish that have been observed in the Western Atlantic. Without exception, these fish found their way into this area at the hand of aquarists. Well-meaning but misinformed hobbyists just looking for a home for their over-grown fish probably released the species listed in bold (including batfish). The presence of the other species is a bit of an enigma. It is not very difficult to find a home for your unwanted royal gramma, purple tang or adult emperor angelfish. Why are there a disproportionate number of expensive, highly sought-after Red Sea fish being found in the Atlantic? There is one likely explanation; somebody was releasing these fish with the intent of producing local populations that could then be exploited by the pet trade. Rumors have persisted for many years of fish collectors releasing royal grammas into Florida waters in an attempt to establish a breeding population of these fish that are not native to the area. It is likely that some fish dealer had an assortment of Red Sea fish and then released them in the Atlantic Ocean north of Fort Lauderdale in the hopes of being able to come back later and collect their offspring. This activity gives a tremendous “black eye” to the aquarium hobby, and it is illegal and must stop. Not all fish dealers are part of the problem. One collector in the Florida Keys actually helped round up a stray batfish that had been living on an offshore reef.
Exotic fish species reported from U.S. coastal waters.
Chaetodon fasciatus – Red Sea raccoon butterflyfish
Cromileptes altivelis – Panther grouper
Gramma loreto – Royal gramma
Naso lituratus – Naso tang
Platax orbicularis – Orbicularis batfish
Pomacanthus annularis – Bluering angelfish
Pomacanthus asfur – Arabian angelfish
Pomacanthus imperator – Emperor angelfish
Pomacanthus maculosus – Yellowbar angelfish
Pomacanthus semicirculatus – Koran angelfish
Pomacanthus xanthometopon – Blueface angelfish
Pterois volitans – Black lionfish
Rhinecanthus verrucosus – Bursa triggerfish
Zanclus cornutus – Moorish idol
Zebrasoma desjardinii – Red Sea sailfin tang
Zebrasoma flavescens – Yellow tang
Zebrasoma veliferum – Sailfin tang
Zebrasoma xanthurum – Purple tang
References:
Bullard, S.A., Benz, G.W., Overstreet, R.M., Williams Jr., E.H. and Hemdal, J.F. 2000. Six new host records and an updated list of wild hosts for Neobenedenia melleni (MacCallum) (Monogenea: Capsalidae). Comparative Parasitology 67(2):190-196
Gosliner, T.M., Behrens, D.W. & Williams, G.C. 1996. Coral reef animals of the Indo-Pacific. Sea Challengers Monterey, CA
Hemdal, J.F. 1997. The red-rimmed batfish - revisited. Aquarium Frontiers On-Line
Hemdal, J.F. 1985. The pinnatus batfish: force-feeding, a new idea for maintaining this species? Freshwater and Marine Aquarium 8(10):18.
Kuiter, Rudie H. 1996. Guide to Sea Fishes of Australia. New Holland Publishers, Australia
Randall, J.E. & Emery, A.R. 1971. On the resemblance of the young of the fishes Platax pinnatus and Plectorhynchus chaetodontoides to flatworms and nudibranchs. New York Zoological Society, Zoologica 56(3) 115-119
Walker, Stephen D. 1991. Reproducing the Atlantic Spadefish at the Tulsa Zoo. SeaScope Vol. 8, Winder 1991. Aquarium Systems.
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