Marine Animal Zoogeographical Regions for Collection
Knowing the four main regions from which marine ornamentals are collected for the hobby

The terms range and zoogeographical region are often used interchangeably in the marine aquarium hobby. For example, in the Quick Facts associated with every animal on the Blue Zoo Website, we list the animals rangeusually Caribbean, West Africa, Indo-Pacific, or Eastern Pacific. These are, more accurately speaking, the zoogeographical regions from which these animals are collected, not the animals range per se. Understanding both an animals range and its zoogeographical region is important to the serious aquarist, as it allows that aquarist to be more conscientious, practice better husbandry techniques and pursue a rewarding aspect of the hobby known as biotoping.

The Difference Between Range and Zoogeography

To understand the difference between range and zoogeographical region, it helps to look at some specific examples. The Banggai cardinalfishs (Pterapogon kauderni) range is listed on the Blue Zoo Website as Indo-Pacific, but its native range is actually restricted to a much smaller areathe Banggai Islands of Indonesia. The resplendent angelfish (Centropyge resplendens), on the other hand, has a stated range of Ascension Islands, Mid-Atlantic, even though Ascension Island is part of the Western Atlantic zoogeographical region. For this reason, some retailers will list the resplendent angelfishs range as Caribbean, even though it is clearly not from the Caribbean proper.

Changing Ranges and Crossing Zoogeographical Boundaries

To confuse matters, sometimes animals expand or limit their range in response to natural events or man-made changes to the environment. In fact, natural events are responsible for the establishment of the major zoogeographical regions from which tropical marine aquarium animals are collected. As Mark Martin, director of marine ornamental research at Blue Zoo Aquatics, explains in his forthcoming The Complete Idiots Guide to the Saltwater Aquarium (December 2008), A very long time ago, a continuous belt of coral reefs circled Earth. Then, about 24 million years ago, the shifting of continents and the formation of Eurasia and Africa interrupted that one continuous reef. As the continents continued to shift, a second barrier was formed by North and South America, resulting in two distinct bodies of water. Hence, today we have four distinct zoogeographical regions from which marine animals are collected for the marine aquarium trade. They are the Western Atlantic, West Africa, the Indo-Pacific, and the Eastern Pacific.

While each of these areas shares the same environmental conditions that allow reef-building corals to grow, Martin continues, each is also quite unique as a result of its separation from other coral reefs. As he points out, because of the continents and deep oceans that separate these zoogeographical regions (we call these zoogeographical boundaries), it is rare that a species from one makes its way into another.

Zoogeography and the Conscientious Aquarist

But make their way they do from time to time, usually as a result of human involvement. For example, nearly 400 species indigenous to the Indo-Pacific have migrated to the Mediterranean Sea, most as a result of the construction of the Suez Canal in 1869. These animals, sometimes called Lessepsian Immigrants (Lesseps was the developer of the Suez Canal), have been responsible for profound changes to the Mediterraneans indigenous populations. More recently, the lionfish has become established along the Atlantic Coast of North America from Florida north to New England as a result of specimens originally imported for the marine aquarium hobby.

Human induced expansions of a plants or animals range into other zoogeographical regions can be the source of ecological catastrophe. This has certainly been the case with Caulerpa taxifolia in the Mediterranean, and it is the reason that many Caulerpa species are currently banned for use in the aquarium hobby in the United States. The conscientious marine aquarist must understand the role the aquarium industry has played both incidentally and intentionally in species migrations from one zoogeographical region to another and act accordingly by:

• Knowing the indigenous range of the animals you keep
• Knowing the husbandry requirements of any animal you purchase before you purchase it
• Never releasing an animal into a body of water where it is not indigenous
• Educating other aquarists about the importance of preserving the integrity of zoogeographical regions

Zoogeography and Husbandry

Reef-associated tropical animals such as those we keep in our aquaria are among the most interesting, diverse and specialized animals on the planet. In many cases, animals are so adapted to their specific environment that they cannot proliferate (or in some cases even survive) elsewhere. It is interesting to note that, while tropical reef animals appear to be most limited in their range by temperature, many species are not found in other areas even if the appropriate thermal conditions exist. For example, many tropical marine aquarium fish species are not found circumtropically. Instead, an animal that is indigenous to one zoogeographical region such as the Indo-Pacific may be completely absent from another zoogeographical region such as the Western Atlantic even though the temperature is the same.

It naturally follows that a species so specifically adapted to one part of one zoogeographical region will do best if that areas environmental conditions are most closely replicated in the animals captive environment. Is an Indo-Pacific reef really that different in terms of environmental conditions than a Caribbean reef? Yes and no. While temperature may be similar on a given Indo-Pacific reef and a given Caribbean reef, other important environmental factors are different based on the way that reef system evolved and its zoogeography.

The success of a species is often highly dependent on the interconnectedness of plant and animal species living within the same ecosystem. These plants and animals are usually restricted to the zoogeographical region by naturally occurring zoogeographical boundaries, and, because of this isolation, these species have evolved together in such a way that their relationships may prove beneficial, if not even essential, to their success. Hence, understanding how zoogeography affects an animals behavior in the wild may well help the aquarist when it comes to the captive husbandry of that animal.

In addition to zoogeography, a given species success may also be highly dependent upon other environmental conditions such as storm activity (e.g. the effect of hurricanes on Western Atlantic reefs), dominant currents and seasonal temperature changes. Taking into account as much zoogeographical data as possible when considering the best husbandry for a particular species can, in some cases, be the difference between success and failure.

Does all this mean the marine aquarist should not mix species from different zoogeographical regions or introduce a Western Atlantic fish to a tank built to replicate a nearshore Indo-Pacific reef? Absolutely not. Designing a Fantasy Reef Tank, where you cherry pick the best species from each of the four zoogeographical regions can be very rewarding, as these animals would never be seen together in the wild.

Zoogeography and Biotoping

While a fantasy tank may appeal to some, other aquarists prefer to design systems that are more like the natural environment. One way to do this is to employ a biotope approach whereby you select first a zoogeographical region, then a specific ecosystem within that zoogeographical region and, finally, an individual sessile invertebrate (one that wont move much or at all) from that region around which to build your aquarium. As we shall see in a moment, approaching aquarium design in this manner can be quite rewarding, as you are truly bringing a piece of an ocean environment into your home. A biotope tank such as this also provides an opportunity for the aquarist to observe the close-knit relations of species that live together in a complex matrix of symbiosis in the wild.

The aquarist interested in replicating a portion of a reef they photographed while diving in the St. Barths Marine Reserve in the Western Atlantic Zoogeographical region, might choose to build their biotope aquarium around a sessile invertebrate such as the dazzling orange spot ricordea (Ricordea florida) or a magnificent feather duster (Sabellastarte magnifica). In this aquarium, other species from the same biotope (which roughly translates from the Greek as life place) might include a condy anemone (Condylactis spp.), some zoanthids (Zoanthus pulchellus), a couple of anemone shrimp (Thor amboinensis), cerith snails (Cerithium litteratum), two long spined urchins (Diadema antillarum), a sally lightfoot crab (Percnon gibbesi), a sea cucumber (Holothuroidea spp. ), a lettuce sea slug or two (Tridachia crispate), a fairy basslet (Gramma loreto), a shoal of blue chromis (Chromis cyanea), a redlip blenny (Ophioblennius atlanticus), several neon gobies (Gobiosoma oceanops), and a blue tang (Acanthurus coeruleus).

Published 15 July 2008. Blue Zoo Aquatics