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Figure 1. A male green wolf eel blenny.

It's well understood that the fish we have in our home aquariums originated in one of the many oceans of the world and that these fish were collected from the wild, shipped across continents, and finally end up at a local fish store. Hopefully, we also have an appreciation of the hardship suffered by these fish due to wild collection and that many of these fish populations will ultimately not support unlimited and unregulated harvesting without vanishing. Given this, the time is now for many home aquarists to act in regards to reducing the demand for wild caught fish by aquaculturing fish as part of their home efforts. In fact, many hobbyists are beginning to do just that; there are a number of commonly available clownfish species (Amphiprion sp.) that are being home bred with great success. Banggai cardinalfish (Pterapogon kauderni) are another species commonly bred as part of ongoing home-based breeding efforts. Most importantly, breeding and raising the fry of these fish is not out of the grasp of many aquarists with limited aquarium experience, and as more commercially available first foods for fry become commonplace, breeders should expect to be increasingly successful with additional marine ornamental fish. Back in April 2004 as part of the Fish Tales column, Henry Schultz described the family Congrogadus, i.e., "wolf eels," a family little known to most hobbyists, yet this fish is perfectly suitable for home breeding efforts and makes an interesting and hardy addition for the aquarist who keeps fish-only tanks.

This fish from the Indo-West Pacific is neither an eel nor a blenny (and most certainly not a wolf). Other common names include the carpet eel blenny or just plain ol' eel blenny. As described in detail in Fish Tales 2004-4, this fish is a member of the Pseudochromidae (Dottyback) family. Attaining a full-grown length of 45cm makes it one of the largest in that family; Pseudoplesiops typus is the largest, reaching 46cm. One useful attribute of this fish is that it is sexually dichromatic; meaning the males (figure 1) are green, while the females (figure 2) are a more drab gray/brown with a pinkish hue that seems to vary in intensity. Additional species descriptions can be found here and here.

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Figure 2. A female green wolf eel blenny.

The wolf eel blenny has a temperament and size that would prohibit keeping it in most reef tanks. In fact, I highly recommend this fish be kept with other larger aggressive fish that cannot fit into its cavernous mouth; however, wolf eels generally do best in a species-only tank. The wolf eel blenny is occasionally collected for the trade and can be found for sale at local fish stores or online retailers. In its natural habitat of shallow reef areas, this fish prefers to inhabit rocky crevices where it can easily lunge out at unsuspecting prey.

Even though this fish attains an adult size of around 18 inches, it doesn't require a lot of room to feel comfortable or to breed in captivity, as this fish acts very eel-like, usually projecting its head from the rockwork or hiding behind rock outcrops. In one particular instance, I know of a hobbyist who had a pair that spawned in a 30-gallon tank. To make this fish feel at home the aquarium should be set up with plenty of rockwork, creating caves where it can lurk waiting for its next meal to pass by. The wolf eel should be fed plenty of meaty foods. When first acquiring this fish, it will readily accept live feeder fish and crustaceans (such as ghost shrimp) but, given enough time, it is not difficult to wean over to dead or prepared foods and should be fed to satiation two or three times weekly. Rapidly growing juvenile wolf eels can be fed smaller, more frequent meals daily. If properly fed, these fish prove to be hardy tankmates; however, my experience also suggests that they do not hesitate trying to consume a new tankmate if the new fish "appears" to be the right size to fit into its mouth.

The spawning ritual of C. subducens is similar to most dottybacks. The female lays eggs in a ball-shaped mass, which the male fertilizes and then guards by wrapping his body around the egg mass. Little information is available from the literature regarding this fish's spawning behaviors; suffice it to say that the information presented here will be composed of a summary of experiences from a few different hobbyists that have been fortunate enough to create spawning pairs. However, be advised, as with most fish, it seems that getting the fish to spawn is the easy part; raising the fry is the biggest challenge. For some reason (and I am not discounting luck) I have been the only person I know who has been able to successfully raise green wolf eel fry.

The wolf eel blenny is a seasonal spawner, usually spawning five or six consecutive times about 10 to 14 days apart and typically starting around November/December. I don't know how they sense the change of seasons when they live in controlled, constant environments with no effort made to simulate the change, but somehow they do. As noted above, an enormous tank is not necessary to house a pair of these fish, but there should be plenty of places for the female to hide, since the male is the more aggressive/dominant one and is likely to harass her. In every case of captive spawning that I know of, the female was the first inhabitant of the tank, while the male was added some time later. In each case, however, this was by chance rather than by planning; but I feel it is important, given the male's more aggressive/dominant role. I would not be surprised if a female would be killed if she were added to a tank where a male had first made his home. Another factor that may be important when pairing up this species is that the female should be both ready and able to spawn. The female will produce an egg mass at regular intervals during the spawning season. When this happens, she can be observed guarding the nest with her body wrapped around it, in much the same way the male does, or she will swim around the tank carrying the egg mass in her mouth, presumably looking for a male to hand off the egg mass to. When there is a male present, he will readily take the eggs as soon as the female produces them, but that is where the female's role ends. The male defends and protects the nest from any intruder, including the mother. As mentioned, the male will curl his body around the nest while periodically shifting, rotating and fanning it with his fins. He typically keeps the nest in a cave or dugout area in the substrate.

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Figure 3. An egg mass after six days of development.

The nest is an egg mass (figure 3) of approximately 100-200 eggs that are about 5mm in diameter. The individual eggs appear covered with bumps and stick to each other creating this mass. Incubation of the eggs occurs over 14 days, after which fry approximately 10mm long emerge. It was interesting to observe the fry within the egg during its development, around the 5th day, the shape of the developing fry becomes discernible, and as the days progress, its eyes begin to appear, along with a red spot in its abdomen, which, I presume, is its heart. From about the 10th day onward, the fry shift noticeably within the egg.

Since my wife and I are amateur fish breeders, we have learned that parental behavioral care can vary widely between specimens of the same species. Some breeders have reported that the male cares dutifully for the nest up until hatching and even then does not actively feed on the newly hatched fry. I was not that fortunate. The spawning pair that I have worked with is actually owned by some friends, Doug and Barb Arnold. They asked for our help in trying to raise the fry (since my wife and I are known in our area for breeding clownfish) after they had made a few unsuccessful attempts.

I soon discovered that one of the problems they faced was that the male was slowly consuming the nest, polishing it off before the 14 day incubation was complete. This was how they lost their first two nests. Subsequent nests were taken from the male a few days after spawning (risking great bodily harm to do so) and put it in a breeder basket at the water's surface. Despite keeping those nests in the same tank and directing water from the filter return over them to keep them aerated, the next few batches had a very low hatch rate with most of the eggs turning milky white and becoming infected with a fungus before they were due to hatch. Combine that with the parents sucking the hatched fry through the slots of the breeder basket and eating them, and Doug and Barb didn't have much to work with. For some reason, the fry that did survive did not survive for long; all died within one day. So, after talking to Doug and Barb, we decided to take the next nest and see what results we could achieve (admittedly, not much of a plan). Five days after the spawn, we gently separated the egg mass into one small part for Doug and Barb to keep while I took the larger portion. The portion I took was placed into a large fish bowl containing only water from the parent's tank, and it was aerated so that the nest was gently moving (see figure 3). Things went well for the first few days, after which the water quality started to deteriorate quickly as some of the eggs began dying off. Water changes of up to 90% were conducted on a daily basis in an attempt to maintain water quality. In spite of my best efforts, the nest began to break apart with some of the eggs fouling and turning milky white. I did my best to keep the dying eggs removed from the mass, but as the 14th day approached, things quickly took a turn for the worse. By the 15th day there was no hatch, and the nest was slowly deteriorating. I took these two pictures below; the first (figure 4) is a still viable egg and the second (figure 5) is a pre-hatch fry whose shell I had manually removed. On the 16th day it looked as if this project was going to be a total failure. Looking into the bowl, I couldn't see any eggs that appeared to be still viable. I was considering dumping the whole egg mass down the drain when my wife spotted a newly hatched fry swimming around in the bowl. We removed the fry and put him into a separate container with some water from another tank, and closely examined what was left in the bowl one more time. It seemed that one was all we were going to get from this batch.

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Figures 4 & 5. Left: An egg due to hatch. The egg shell has become less transparent than earlier in development. Right: A fully developed fry that has been manually removed from its shell. Its features are much more distinct than in the left picture, and a yolk sac can now be seen.

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Figure 6. Junior at 14 weeks old. Judging by his coloration, I would say that our Junior is a male. I have been unable to find information about this species' potential sexual dimorphism, so I suppose this guess could change.

Junior, as he was so aptly named by my wife, was about 10mm long when born and was very active, making repeated laps around the fish bowl. It looked just as others have described their fry: slender, silvery/transparent with big eyes and a large red spot in his abdomen. Since we normally have a large supply of rotifers on hand, we tried this as a first food. Judging from his size we supposed that freshly hatched Artemia would be small enough, but from the limited information that I had, it would seem that this hadn't worked well for other breeders. For the first two days I kept a dense supply of rotifers in its bowl with some greenwater added to ensure the rotifers remained nutritious until Junior had a chance to eat them. It was very hard to tell if it was actually consuming the rotifers, so I started adding newly hatched Artemia to the bowl. Junior's belly then gained an orange hue from eating the live BBS, so I felt that we might have a good chance at raising him. I believe the difference is that other breeders tried offering frozen BBS, while we had success using live ones. In that first week, the fry grew rapidly, gaining about 50% in overall size; the coloration gradually became a more opaque silver with just a hint of green. Live baby brine shrimp was the primary food for the next few weeks, and he continued growing with color patterns slowly developing. As Junior grew, I started raising brine shrimp to larger sizes and fortifying them with Selcon™ before feeding them to him. But, as anyone who has raised brine shrimp knows, this is something that is not easily done. I figured since it was only one fish, it would be easier to capture some mysid shrimp and amphipods, which were numerous in my reef tanks, to feed him. It seemed that Junior preferred the mysids and amphipods over the brine shrimp, as these critters remained on the bottom of the tank where he typically stayed, precluding a swim up into the water column to get the brine shrimp. At about one month of age I decided to try feeding him frozen brine shrimp, which he took to immediately. Whew! No more siphoning critters from the bottom of my reef tanks. At the time of writing this article Junior is 16 weeks old and about 30mm long. He looks just like a smaller version of his father with the only exception being that his coloration is not quite as dark as his dad's. While Junior has been a joy to raise, I wish we had been more successful incubating the eggs and had at least 50 more just like him. As we began our rearing at the pair's last spawn of the season, we will have to wait until the spawning season of 2005 to make a second attempt at rearing the fry.

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Figure 7. Posing on a quarter for scale.

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Figure 8. An overhead shot with a quarter and a test vial for size reference.

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Care and Breeding of the Green Wolf Eel Blenny, Congrogadus subducens by Alan Drehmel and Frank Marini -