Ask a Librarian

Ask a Librarian is the place to find answers to some of the interesting questions we've encountered. Although brief answers are provided below, you are encouraged to continue your research by reading the full reports cited and by searching the NSGL database where you will most likely find additional information on the topic.

If you can't find what you're looking for below, please email us with your question. This service is limited to brief, factual answers.

• Why do whales migrate?
• Do dolphins sleep?
• What do horseshoe crabs and dinosaurs have in common?
• Will underwater robots some day clean our oceans?
• Why are flounder flat?
• Are all sharks dangerous?
• How do waves form?
• How can you tell the age of a fish?

Why do whales migrate? The migration patterns of several types of whales are related to both their breeding and feeding habits. For instance, humpback whales generally migrate north to colder, temperate waters in early spring where food supplies will be more abundant and return to tropical waters in the late fall for breeding. (MEU-E-84-001; HAWAU-H-88-001; VSGCP-E-85-001)

Do dolphins sleep? Dolphins do sleep, but with only one half of their brain at a time and one eye closed. "Dolphins rest this way on and off throughout the day, switching which side of the brain they shut down. During these periods, everything inside the dolphin slows down, and the animal moves very little." (MIT-E-94-002)

What do horseshoe crabs and dinosaurs have in common? Both horseshoe crabs ("Limulus polyphemus") and dinosaurs date back to prehistoric times. The genus "Limulus" dates back to the Triassic, the first period in the Age of Dinosaurs. However the horseshoe crab's earliest ancestors date back even further. In fact, they were among the dominant critters 100 million years before the dinosaurs even arrived! (DELU-G-95-003; RIU-G1-77-003)

Will underwater robots some day clean our oceans? Underwater robotic vehicles have been considered for various potential environmental applications including underwater pollution monitoring and waste cleaning & handling in the ocean. (HAWAU-W-94-004)

Why are flounder flat? This is a special feature that allows them to live on or near the bottom of the ocean. They actually begin life as a symmetrical fish but soon after hatching , one eye migrates so that both eyes are on the same side of the head. At this point they drop out of the water column, turn on their sides and become bottom dwellers. Being flat allows them to blend in with the bottom; they can even bury in the sediment while they wait for unsuspecting prey. (MASGC-G-92-005; NYSGI-G-01-003; NYSGI-G-01-004; AKU-H-95-001)

Are all sharks dangerous? No; only 40 shark species (out of 300 worldwide) have been known to attack humans. The great white and tiger sharks are among the more dangerous. Shark attacks, however, are still very rare. (MIT-E-94-002; OREXT-W-85-001)

How do waves form ? Most waves are formed as a result of wind passing over the water. Wind speed and direction will help determine the size of the waves. Steady winds blowing over water for a long period will produce larger waves. Waves can also be formed by moving something through the water, such as a boat or by underwater earthquakes that can create very large, long waves called tsunamis. These can reach heights of up to 200 feet. (MIT-E-94-002; OHSU-E-87-014)

How can you tell the age of a fish?  As the fish grows, annual layers, or growth rings, are deposited on the fish's scales or its small inner ear bones. These rings grow faster in the summer months (when the rings are wider apart) and slower in the winter months (when the rings are closer together). The age of a fish can be roughly determined by counting the number of rings. (MEU-E-82-001; MIT-E-94-002; AKU-E-83-002)

National Sea Grant Library
University of Rhode Island
Graduate School of Oceanography
Pell Library Building
Narragansett, RI 02882

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