Marine Invertebrates

282 Natural Reef Aquariums there is potentially a much larger market for reef aquari- extremely delicate aquariums subjects. For example, Stan ums than at present. When people learn what can be done Brown of the Breeder's Registry has a photograph depict-

with a 30-gallon tank, provided a few simple techniques ing spawning by captive Orange-spotted Filefish (Oxy-

are mastered, dealers will sell more of them, along with the monacanthus longirostris). This species is generally livestock to go in them. This can only help the industry, impossible to acclimate to aquarium life, but there they are, and it will be captive-propagated livestock that will form the placing adhesive eggs on the tank glass. I have observed Cir-

base of this new economic pyramid.

ripectes blennies spawning and guarding eggs in aquarium-store holding tanks.

Marine Fish Aquaculture vU •

For those species that cannot be induced to spawn in

the normal manner, the marine aquaculturist has other options. Hobbyists often assume, since they often have only Eggs and sperm can be stripped from adult fish collected the experience of freshwater enthusiasts upon which to from the ocean, and fertilization can take place in the labo-draw, that the problem with the propagation of marine fish ratory. Using this technique, Martin Moe was not only able is in enticing a suitable pair to spawn. This is seldom the to culture both the French and Gray Angelfishes (Pomacan-case, although determining the sex of a fish can sometimes thus paru and P arcuatus), but also to produce a hybrid of be a problem. Aquarium spawnings of marine fish are ac- the two species. Moe's fishes were too costly to compete tually rather commonplace, and even include species that are with wild-harvested specimens, but this might not be the case for other species.

No, the problem is not in getting fertilized eggs. The problem is in rearing the offspring past a certain critical point. Marine fish eggs hatch into larvae that are scarcely more than a swimming brain and spinal cord. Many are so small that they are at the lower limit of human visual acuity. Immediately after hatching, the larvae are attached to yolk sacs that provide nutrition, but once these are exhausted, an appropriate food must be available, suspended in the water column, or the larvae will starve. Providing an appropriate substitute for the rich oceanic soup called "plankton" is the primary challenge of the aquaculturist.

The most commonly used plankton substitutes are discussed in Chapter Twelve and include unicellular algae, rotifers, and brine shrimp nauplii. Experiments with more exotic fare have become popular with the proliferation of interest in captive propagation. Mollusk larvae have been used with success, and the larvae of other invertebrate groups, especially arthropods and echinoderms, should prove to be

Invertebrates

A remarkable crop of Neon Dottybacks CPseudochromis aldabraensis) reared at William Addison's C-Quest facilities

Chapter Thirteen 283

among the most useful. Eggs or sperm may also be used directly as food, and can often be extracted easily from a donor organism. Sea urchins, for example, can be induced to extrude gametes by administering an injection of potassium chloride. Larval echinoderms can also be produced in a laboratory culture, using techniques in widespread use in research laboratories. The size of the food organism is important, although there may be a variety of other factors that determine whether larval marine fishes can survive to metamorphosis on one diet or another. This is an area ripe for extensive research, as very little is known about the ecology of fishes during this critical period of life. Collection or cultivation of natural plankton is another approach often taken in the search for an appropriate larval fish food. A good beginning point for anyone wanting to research this aspect of Striped Mushroom Anemone (Actinodiscus sp.): much in demand and marine biology is Smith (1977). easily propagated, organisms like these are excellent candidates for

A recent survey of 51 public aquariums small-scale captive reproduction by hobbyist-breeders. (Walker, 1996) shows that, for larvae produced as a result of aquarium spawnings, 43% of all species could chance meeting of gametes cast into the open sea. Spawning be reared beyond metamorphosis. Almost half (48%) of the behavior is timed to maximize the chances of such a meet-successful rearings were at one institution, suggesting that ing, or it may be accomplished through the release of chem-more species could be reared through the delicate meta- icals that lure sperm to eggs. "Sperm" or "male" gametes morphosis period if the effort is made, and that laborato- are, by definition, the smaller, motile member of the pair, ries that develop techniques that work for one species may while "eggs" or "female" gametes are larger, contain a food supply for the larva, and are incapable of locomotion. Of course, there are exceptions, and the terms "male" and "female" can become blurred in the world of marine invertebrates and algae.

Nevertheless, invertebrate larvae, once obtained from

Invertebrates

have later success with another.

Propagation of Marine Invertebrates

Culture of marine invertebrates from sexually produced larvae offers challenges similar to those faced by captive or wild spawnings, may prove as difficult to feed as the fish culturist. Obtaining larvae is rarely the issue; many fish larvae are. For example, many attempts by aquarists to species can be induced to shed gametes, and the natural rear the popular Banded Coral Shrimp (Stenopus hispidus)

method of fertilization in reef invertebrates is frequently the have failed, despite the fact that a pair will produce a clutch

Marine Invertebrate

Chapter Thirteen 285

oflarvae in the aquarium on a regular basis. By contrast, the Peppermint Shrimp {Lystriata wurdemanni) is easily reared on a diet of rotifers and brine shrimp nauplii. The early life stages of tridacnid clams must be reared under laboratory conditions, and the baby clams must be "infected" with zoo-xanthellae prior to their placement in grow-out trays in the lagoon. For a complete account of the process of farming tridacnids, consult Heslinga, et al. (1990).

Fortunately, a considerable variety of invertebrates popular with aquarium hobbyists can be propagated by fragmentation, or otherwise induced to produce offspring vegetatively. Disc anemones and some soft corals, for example, may grow so well in some systems that they must be thinned or pruned regularly. It appears that virtually any of the leather corals, many sea mats, photosynthetic gor-gonians, and xeniids can easily be multiplied by taking cuttings. SPS (small-polyped scleractinian) corals, many of which expand their range in nature when shards of their colonies are broken off and scattered by storms, can also be propagated from small fragments. Typically, pieces are attached to a suitable substrate using underwater epoxy, placed under appropriate conditions, and a new colony develops within weeks or months. The anemone Entacmaea quadri-color can be persuaded to divide under suitable aquarium conditions. This clownfish host could someday be as com-monplace as the clownfishes themselves.

Another aspect of captive propagation is only beginning to be explored. This approach is well suited to the home hobbyist interested in a small income from "playing around" with marine aquariums. It involves simply obtaining small specimens of desirable species and growing them out to a larger size. Since bigger specimens command a higher price and smaller ones are easier and cheaper to ship in large

Captive-propagated "Bali Green" stony coral (Acropora youngei) grown by Steve Tyree's Dynamic Ecomorphology.

numbers, this can be a profitable project for anyone with the space and know-how. Among the better choices for such an aquaculture project are tridacnids, any sessile invertebrates, and clownfishes. Simply placing two juvenile clowns from the hatchery into a tank together will result in the formation of a mated pair within months, and the value of the fishes then more than doubles.

Marine fish hatcheries and other types of aquaculture facilities are springing up all over the country. I have had the opportunity to visit several of them, and have corresponded with many of the proprietors. What emerges is an exciting picture of a growth industry in its formative stages.

MAJOR VENTURES. Aqualife Research Corporation, founded by Martin A. Moe, Jr., in 1973, was the first large-scale ornamental marine fish hatchery in the United States. It was located initially in Florida, and then moved to the Ba-

mr hamas when Moe sold the business to Precision Valve Corporation. Aqualife continued to produce clownfishes and neon gobies until it closed when investors pulled out in

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