Research Article:
The Abundance & Diversity of Life in the Water

Icthyology is the study of fish. Dr. Jim Bohnsack is an ichthyologist who is interested in reef fish and the world in which they live. Dr. Bohnsack describes this world of reef fish as "another planet," where the inhabitants move gracefully through the water in search of food or shelter. This world presents not only travel obstacles but also visual obstacles for humans. Every object that humans look at is seen through a lens of water that magnifies and alters its true shape, size, and color.

Although this world is not the most natural environment for humans, Dr. Ballard, Dr. Bohnsack, and many other researchers believe that the underwater world is a new frontier that will play a role in human survival in the future. They believe it's important to learn more about this new frontier and the organisms that live there. To explore this world, researchers need specialized equipment to travel and work underwater-specialized scuba (self-contained underwater breathing apparatus) gear, submarines (such as the U. S. Navy submarine NR-1), and remotely operated vehicles (ROVs) and cameras (ROCs). During JASON VII, Dr. Bohnsack will use all this equipment to conduct his research. You will learn more about scuba and the Navy's NR-1 submarine in Investigations 14 and 15, respectively.

As an ichthyologist, Dr. Bohnsack is interested in nearly every subject dealing with fish. However, his specialty is tropical reef fish, of which approximately 300 to 400 species live in the Atlantic Ocean and 600 to 700 species in the Pacific Ocean. That is a lot of fish to learn about and remember! Therefore, Dr. Bohnsack uses his own strategies as well as those of other ichthyologists to remember all the different kinds and their respective behaviors.

To identify fish, Dr. Bohnsack looks at many aspects of fish appearance and behavior, including:

By understanding the relationships among these various characteristics, Dr. Bohnsack can classify a fish when he first sees it, according to its physical characteristics and its behavior. For example, when Dr. Bohnsack sees a fish with a long body, sharp teeth, silver color, and forked tail with slits hiding among other fish, he knows that this fish is most likely a stalker. The fish has coloration that blends in with the other fish, allowing it to hide in their midst. The teeth tell him that the fish is probably a piscivore (an animal that eats fish). Dr. Bohnsack knows that the slender body shape reduces resistance to water when the fish swims, which makes this fish a fast swimmer. The tail also helps Dr. Bohnsack determine how fast the fish can swim. In this case, the tail with slits indicates that the fish is a sprinter (fish that swims at fast pace in short bursts), which is what a stalker generally needs to be.

The location in which Dr. Bohnsack finds a fish also helps him identify that fish. For example, some fish are specialists. They live in water with a particular type of bottom, such as sea grasses, sand, rubble, mangrove roots, or coral reefs. Or they live at a particular level within the water: near the top (shallow), in the middle (midwater), or at the bottom (benthic). Other fish are generalists and are found in many places. The fish described in the previous paragraph is found in midwater near sea grass beds, rubble, mangrove roots, and corals where other fish are found. This indicates to Dr. Bohnsack that this fish is probably a generalist.

Can you guess what type of fish Dr. Bohnsack is looking at? (Hint: People are often afraid of these fish and they are quite common in southern Florida, the Caribbean, and other warm waters.)


Rainbow Line

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Revised: 17 Oct 1995