Swimming Performance in Juvenile and Sub-Adult Lemon Sharks (Negaprion brevirostris) at the Bimini Islands, Bahamas.
Tim Fieret & Dr. Samuel H. Gruber
A large part of a shark's energy budget is spent on locomotion. Therefore it is important for sharks to swim at an efficient performance level. Swimming performance can be defined as the ratio of tail beats over distance covered per tail beat. When this is taken relative to the shark's size, we have a tool to compare swimming performance between large and small sharks. As a shark grows older and thus larger, they swim faster. We expect swimming performance to be constant while the shark matures, as studies on other fish have shown such results.
To study the development of swimming performance, several sizes of shark are needed. This study focuses on Lemon sharks (Negaprion brevirostris). They are born at about 60 cm in length, and grow to about 350 cm. Lemon sharks usually reach maturity at a length of about 235 cm. For practical reasons we limit the size of the sharks used in the experiments to approximately 200 cm.
The sharks are kept in a large oval shaped holding pen. Meter markers are placed along the straight edges of the pen. The sharks are filmed with a hand held video camera while they swim freely in the pen. From the film we can determine speed, distance covered and tail beats, allowing the calculation of the swimming performance.
The smaller specimens are collected with gillnets, while the larger ones are caught on rod and reel. For a good sample size range, around seven specimens are required. So far sharks measuring 70, 93, 106, 123 and 167 cm in length have been filmed.
An additional part of this study is to investigate whether there are diel variations in swimming speed and performance.
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