Amazing Advancements In Captive Breeding Of Marine Fish

Advancements are being made every day in the field of marine breeding by professionals and hobbyists alike.

Orange Spotted Filefish (Oxymonacanthus longirostris. Via Richard Ling/Wikipedia

Mandarinfish. Orange-spotted filefish. Pygmy seahorses. Blue Tangs. All are species that were once considered impossible to breed in captivity, but this has proven not to be the case. Granted, none of these fish are being produced on a commercial scale and we still are unaware of the exact details of the P. hepatus spawning, though ORA was reliably breeding mandarins until this particular operation was suspended due to lack of consumer support. It’s incredible to think about how far the captive breeding of ornamentals has come since Martin Moe first made clownfish commercially available in the ‘70s, and it’s reasonable to think that we have some exciting times to look forward to in the near future.

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A couple decades ago it was a major accomplishment just to keep some of these fish alive for more than six months, let alone successfully breed them and rear their larvae to adulthood in a captive environment. This shift has occurred gradually and can be attributed to many developments including but not limited to steady advancements in tank maintenance equipment, research conducted and widely disseminated by both scientists and hobbyists, use of proper capture and transportation methods, and a much better understanding of fish nutrition.

For these and other reasons, the variety of species that aquarists regularly have access to has grown exponentially along with the species that can and have been captive bred. According to a study published in 2012 that examined in detail “an entire year (May 2004-May 2005) of import records of marine tropical fish entering the United States,” the approximately 11 million fish imported comprised of 1,802 species from 125 different families. While this is a high level of diversity overall, the top 52% of the total number of fish imported was made up of only 20 species, with half of these being Pomacentrids (clowns and damsels).

To date, approximately 250 species of marine ornamentals have been bred in captivity, but only about a hundred of these are commercially available, and often times only sporadically. As this list of captive bred organisms increases, so does the degree of difficulty associated with rearing the larvae, but with the wide availability of larval foods and determined hobbyists at every level of expertise, funding and space seem to be the only limiting factors to progress.

Space is certainly thought to be one of the biggest issues surrounding captive spawning of a popular marine aquarium species, the Regal Tang, Paracanthurus hepatus. These fish are pelagic spawners and as such mate in mid water, making it difficult to not only provide them with a habitat deep enough to induce spawning behavior, but also to collect their minute eggs and larvae. In general, pelagic spawners release thousands of tiny eggs into the water column, making up for a complete lack of parental care with sheer numbers. Due to their extremely high mortality rate as pre-settlement larvae, the Regal Tangs that we call “captive/tank raised” have been collected from the wild shortly after they “settle” onto a reef but before they officially begin their lives as juveniles. This keeps collection pressure on wild populations to a minimum because it removes individuals that would more than likely have been eaten on the reef long before becoming juveniles, making tank raised tangs a far more sustainable choice in comparison to wild caught ones.

Of course, the best option would be to breed them entirely in captivity, but this is yet to be accomplished on a commercial scale, probably due to the inherent cost and space required for such an operation; conversely, they have spawned in home aquariums no deeper than 24 inches, so depth may turn out not to be the biggest hurdle. Their lengthy larval stage is another factor that makes breeding tangs a challenge. It was reported three years ago that a scientist in Taiwan had successfully bred Regal Tangs in a lab at their Fisheries Research Institute, but details of the process have never been made available, an information gap that makes all of us a bit skeptical as to the validity of this claim. Hopefully this will change in the near future.

Pygmy seahorse. Photo by Alex Rose

At the opposite end of the space spectrum, we have the Pygmy Seahorse, Hippocampus bargibanti. California Academy of Science’s Steinhart Aquarium recently collected from the Philippines some of the first pygmies to be kept in captivity. They are already breeding these fantastically tiny (less than an inch when fully grown) and colorful animals and have some equally amazing documentation to go along with it. Bargibantis are hard enough to maintain, let alone breed, as they spend their entire adult lives in the protection of their host coral, a gorgonian in the genus Muricella, the texture and color of which they mimic so well as to be nearly invisible to all but the most trained eye. Both the coral and the seahorse require nearly constant access to high densities of live food, or they will perish in short order, making water quality a primary issue in successfully keeping these animals. While it’s highly doubtful that we’ll be seeing this species in the trade, and I tend to think that’s a good thing, it’s an exciting achievement in the world of captive bred marine species and a great opportunity to learn more about these most diminutive of seahorses.

Advancements are being made every day in the field of marine breeding by professionals and hobbyists alike, making our trade more sustainable and well-informed with each accomplishment.
Alex Rose

Alex Rose is a biologist (BS and MS Biology), diver (PADI Divemaster), musician, underwater photographer, and lover of all things aquatic. Her driving goal is to find ways to protect our world’s coral reefs through diving, writing, education, and the establishment of a sustainable marine aquarium trade.

Article Categories:
Fish · Saltwater Fish