Where Aquarium Fish Originate
Marine Fish are Collected from Four Main Collection Areas
Understanding from where the fish you purchase for your marine aquarium come can make you a more successful and knowledgeable aquarist.
Many of the fish commonly seen in the marine aquarium hobby come from the Indo-Pacific. Those that don’t come from the Indo-Pacific, frequently come from the Eastern Pacific, the Caribbean, or West Africa. While other species are available, they are far less common in the hobby. Why is this?
Isotherms
It has to do with isotherms. An isotherm is a line connecting points of equal temperature. Imagine a globe with two lines drawn—one to the north of the equator and one to the south. These lines connect points in the ocean with equal temperatures—a temperature around 20-°C. Map the world’s coral reefs onto this globe, and you will find that the reefs’ northerly and southerly boundaries are roughly equal to the two lines you drew around the globe connecting points with the same temperature. In short, you would find that coral reefs are found within the 20°C isotherm.
20-°C Isotherm and Coral Reefs
Is the fact that the north-south extent of coral reefs coincides with the 20-°C isotherm a coincidence? Of course not. Water temperature is, as most aquarists understand, an important factor in successful husbandry of most marine animals. It is common to keep a tropical marine aquarium somewhere between 25- and 27-degrees Celsius. Reef building corals are limited by temperature, and most cannot survive at temperatures below 20°C. In fact, most do best between 23- and 29°C, and while some animals can tolerate cooler temperatures, they require the habitat provided by hermatypic corals to thrive. As a result, they too limit their range to within the boundaries of the 20°C isotherm.
Greatest Diversity
If you were to trace the 20°C isotherms around the globe, you would find that the largest region of ocean area contained within this narrow band is the Indo-Pacific. That is why so many animals in the marine aquarium hobby come from that part of the world. Within the Indo-Pacific, the greatest diversity of marine life is found in the area off the northeast coast of Australia and extending north and east through the Solomon Islands, north to the Marshall Islands and then west to the Philippines before trending back south through Sulawesi and Papua-New Guinea toward the northeast shore of Australia.
Other Collection Areas
Outside this area are other portions of the Indo-Pacific which frequently are involved in the marine trade such as the Red Sea, Southern Japan and places like Fiji and Hawaii. Travelling outside the Indo-Pacific (in a westerly direction), you find the west coast of Africa—the smallest of the major collection areas involved in the marine aquarium hobby. Crossing the Atlantic, you come to the Caribbean region—a remarkably large region that extends far beyond what most people think of when they think of the Caribbean. From as far north as Bermuda to as far south as Rio de Janeiro, there are stony reef building corals. Finally, travelling further west across Central America, you come to the last of the major collection areas—the Eastern Pacific from southern Baja to the coast of Peru.
As an aquarist, it is useful to keep these four areas in mind as you set-up your tank. The species that live in these areas are all tropical marine animals, but despite their tolerance for the same temperature and general habitat (reef-building stony corals), they are remarkably different based on their separation by either deep ocean or land masses. Setting up a system with animals from the same collection area can be an educational and rewarding endeavor, giving the aquarist an opportunity to learn about a geographical region.
