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How Captive Propagation Helps the Aquarium Hobby

The hobby affects global fish biodiversity in many ways — some positive and some negative.

By John Tullock |

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Despite a continued and alarming loss of species worldwide, there is some very good biodiversity news about fish and other aquatic species. Although the individual stories vary, the common thread that links rare fish from Indonesia, Tennessee and places in between is about the success of aquaculture as a tool for species preservation.

Much of the progress achieved in cultivating nonfood fish species — including some unique and endangered ones — would not have been possible without techniques long familiar to aquarium hobbyists. In some cases, the potential market represented by the world’s amateur aquarists provides the incentive for private investments in hatchery facilities and research leading to rare species recoveries.

The Banggai Cardinalfish

A splendid example of a fish species both harmed and helped by the aquarium hobby is the Banggai cardinalfish (Pterapogon kauderni). In the years since its introduction to American aquarists by Dr. Gerald Allen in 1995, the wild population of this fish has shrunk by nearly 90 percent — likely the result of collecting for the aquarium trade. Found in shallow, inshore waters, this fish associates with long-spined sea urchins (especially when young). This habit makes them easy targets for collectors. When alarmed, the fish seek shelter in the nearest urchin, which the collector simply scoops into the net, Banggai cardinalfish and all.

Banggai cardinalfish
Banggai cardinalfish. Photo by Aaron Norman

The World Conservation Union (IUCN) placed P. kauderni on its Red List as an endangered species in September 2007. This came after a failed attempt to have the fish listed on Appendix II of the Convention on International Trade in Endangered Species (CITES) in June 2007. The IUCN is an international nonprofit conservation organization with no enforcement powers or other authority, but CITES is a treaty that spells out numerous aspects of international law and has enforcement provisions. More than 100 countries are signatories of CITES, so a listing in CITES would have a greater impact than with the IUCN.

CITES’ listing would have resulted in restrictions on the international trade in Banggai cardinalfish. In a discussion on the Marine Ornamental Fish & Invert Breeders Association website, Dr. Alejandro Vangelli, who has done extensive scientific research on the ecology of this species, says there should be "no doubts about the bleak conservation situation of the Banggai cardinalfish, the lack of any meaningful conservation action by the local government or any other party, and the need of developing captive breeding programs to replace the wild harvest as much as possible”  (marinebreeder.org/phpbb/ viewtopic.php?t=268).

Dr. Vangelli believes low rate of reproduction and unusually limited range contribute heavily to the fish’s rapid decline under collecting pressure. Fewer than 13 square miles of suitable habitat exist for the fish within the Banggai archipelago, a group of some 50 islands spread across about 2,100 square miles of the Indian Ocean. Spawns typically result in fewer than 50 individuals. The male incubates the large yolky eggs in his mouth, which necessitates a smaller brood size. Evidence of the rapid decline in population comes from census data. Between 2004 and 2007, six of 11 sites that were reviewed showed significant population declines, with three of the sites reduced to fewer than 50 fish.
Nevertheless, as many as 900,000 Banggai cardinalfish are exported from the islands each year. Given that the local economic value of the fishery is relatively small, scientists and others were surprised when the United States withdrew its proposal for a CITES listing for the Banggai cardinalfish. Several other countries (most notably Indonesia) objected to the listing. When it became apparent that not enough votes for passage were available, the proposal was withdrawn. To many observers, politics had trumped sound resource management.

The saga of the Banggai cardinalfish provides a study in irony: Although it is easy to breed in aquaria, specimens available to aquarists continue to be wild-caught. Collecting from the wild is still the primary source for the vast majority of species in the marine aquarium trade. No other commercial collection of Banggai cardinalfish exists — the aquarium trade is solely responsible for the decline of wild Banggai cardinalfish.

Usually, reliance on collecting persists because marine aquarium fish often present great challenges to successful captive propagation. The Banggai cardinalfish, however, is a notable exception. The young can be raised almost as easily as guppies, and the small size and early maturity of adults make aquarium spawnings commonplace. Unfortunately, the relatively low numbers of fry also mean low productivity to a hatchery manager. As long as wild-caught fish remain available, captive propagation of the Banggai cardinalfish may offer little incentive to commercial breeders.

Hobbyists have been reporting success in breeding P. kauderni almost from the moment they first learned of its existence. It’s likely that a few tank-raised fish from home-based businesses will join a trickle of commercially produced specimens into the aquarium market over the short term. If the rate of population decline continues, wild-caught Banggai cardinalfish will become ever more rare and expensive, providing encouragement to the hatchery industry. The unfortunate consequence of waiting on such market forces to reduce the wild harvest and stimulate captive production will likely be the total loss of several wild populations of this beautiful and adaptable fish.

Seahorses

Evidence of the way in which CITES listing can affect the aquarium trade can be seen in the increased availability of tank-raised seahorses ever since this group became the first marine fish to receive protection in 2004. The listing requires any country participating in the treaty and wishing to export seahorses to demonstrate that no wild populations are harmed by the trade. Many countries imposed a minimum size limit — proposed by Project Seahorse and accepted by the CITES technical committee — as an enforcement tool. According to Project Seahorse, this approach makes sense because "the size limit — a height of 10 centimetres (4 inches) — falls between size at maturity and maximum size for most species. This reflects a trade-off between ensuring persistence of wild seahorse populations and the need for continued trade [and] offers protection to all but one species. It also allows continued exports in all but one currently traded species” ("Global Trade Rules for Seahorses Take Effect,” Project Seahorse website).

seahorse
Seahorse. Photo by Al Castro
Although the proposal was not intended to eliminate wild-caught seahorses from the aquarium market, in practice it has had this effect, according to a report appearing in the August 2007 edition of Pet Product News International ("Captive-Bred Tasmanian Seahorses,” Pet Product News International). To meet the demand, several commercial seahorse hatcheries have appeared. 

Born in Captivity, Released into the Wild

Too often, the aquarium hobby receives more media attention in cases such as the Banggai cardinalfish and is portrayed as an economic engine helping to drive unsustainable harvest of wild fish populations. Nevertheless, aquarium science and technology — much of it developed for the hobbyist market — offer the best available tools for restoration of damaged aquatic habitats.

The idea of raising rare fish in captivity and releasing them into the wild is not new. As an example, it has been thoroughly tested over the past 20 years in Tennessee by a little-known organization: Conservation Fisheries. This nonprofit has succeeded in restoring three species of rare native fish (the smoky madtom, Noturus baileyi; the yellowfin madtom, Noturus flavipinni; and the duskytail darter, Etheostonum percnurum) that had disappeared from Abrams Creek in Great Smoky Mountains National Park. Studies have shown all three species are now reproducing in the creek, though years will be required for a complete recovery. Conservation Fisheries also works with about 10 other rare fish from locations throughout the southeastern United States. From a small number of wild parents, thousands of baby fish are propagated each year and returned to their native streams.

Yellowfin madtom
Yellowfin madtom. Photo by Dick Biggins/USFWS

Across half the planet in Oman, officials are looking into captive propagation as a means of restoring damaged areas of coral reefs. A storm inundated many of the country’s coastal reefs with silt. Siltation killed large areas of the reef by smothering corals. Now there is hope that corals from undamaged areas can be propagated and transplanted to restore the damaged areas more rapidly than natural regrowth would occur. Reef aquarists will recognize the techniques involved as "fragging” but carried out on a grand scale in the Arabian Sea.

Future Captive Propagation

Every continent has numerous native fish species now threatened with extinction. The Nature Conservancy summarizes the bleak news on its website: "Worldwide, most types of freshwater ecosystems generally are in grave condition and are declining at a much faster rate than terrestrial systems....More than 20 percent of the world’s known 10,000 freshwater fish species have become extinct or imperiled in recent decades. In the United States, 303 fish species, or 37 percent of the freshwater fish fauna, are at risk of extinction; 17 species have already gone extinct, mostly in this century” ("The Declining Status of Freshwater Biodiversity and National and International Water Resources,” The Nature Conservancy website).

The only real limits of the application of captive propagation techniques to a broader spectrum of aquatic species are in funding. And when compared to other types of organisms, fish are often relatively cheap to produce. Less than half a million dollars per species has been spent over the past 20 years for the restoration in Abrams Creek. Compare that to the millions expended on some other noteworthy species restoration efforts, such as the California condor. Reproductive rates for wild fish offspring are so high that hatchery production results in orders of magnitude increases in the number of surviving individuals. With birds and mammals in particular, such gains are almost impossible to achieve, due to the small number of offspring produced per pair. Captive propagation as a conservation tool probably makes more sense for fish than for any other animal group.

Aquatic biodiversity conservation focuses mainly on habitat preservation. Protecting entire ecosystems from development or other human impacts is recognized as the best insurance against species loss. Yet for many imperiled aquatic species, such protection may come too late.

Captive propagation is neither the only, nor even the best answer to the problem of declining aquatic biodiversity. However, aquaculture and aquarium science are likely to play an increasing role in conservation in coming years.
Aquarium propagation and maintenance of captive stocks of rare fish provide a way to protect species from extinction. Marine hobbyists who seek out captive-propagated fish support not only the fledgling ornamental marine aquaculture industry but also the continued survival of the wild coral reefs that inspire us. Freshwater enthusiasts have had access to captive-propagated fish for decades, but now the techniques pioneered by the industry are being successfully applied to problems of freshwater biodiversity worldwide.

Aquarium hobbyists — both freshwater and marine — now have the option to support sustainable practices that promote aquatic biodiversity. By purchasing captive-propagated fish, hobbyists place no demand upon fragile wild populations, while continuing to enjoy a fascinating and educational hobby. I call that a win-win situation.


 

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