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Dolphins in the Tank


* Section 1
Entanglements
Pingers

* Section 2
Hypotheses
Captive Studies

* Section 3
Daily Experiments
The Future

SECTION 1

Ann BowlesI am Ann Bowles, a senior research biologist at Hubbs-Sea World Research Institute in San Diego, California. My research includes both laboratory and field studies of the behavior and bioacoustics of birds and marine mammals. Right now I'm working with a team of researchers to study how marine mammals respond to human-made objects and sounds that are novel (unfamiliar) to them.

Through this study we are hoping to solve the problem of marine mammals becoming entangled (caught in) in fishing nets. The official name of the project is "Behavioral Responses of Captive Cetaceans and Pinnipeds to Net Fragments and Pinger Sounds." We call it the "Novel Objects Project" for short. The cetaceans (whales) we are studying are dolphins and porpoises. The pinnipeds (feather-foot mammals) we are studying are sea lions, seals, and otters.


Entanglements
Each year many marine mammals become entangled in nets during fishing operations such as tuna fishing and shrimp trawling where large nets are pulled behind boats to scoop up the catch. Marine mammals also become entangled in drift nets and gill nets, which are stationary nets set in shallow water to catch fish as they swim by. These wide nets are made of a fine mesh and are very difficult to see. Marine mammals also become caught in fragments of nets, ropes, and other garbage left in the ocean. Once caught, they drown because they cannot get to the surface to breathe.

When dolphins and other marine animals are caught accidentally in nets, it is called "bycatch" because catching them was not the fishing goal. Bycatch has become a significant cause of injury and death for many species of marine mammals. It also results in millions of dollars of lost fish and damaged gear for the fishing industry. The Novel Objects Project seeks to learn why marine mammals get entangled and to help develop techniques and strategies to reduce bycatch.




Pinger


Our study is designed to answer questions about how to keep pinger sounds novel and useful.

Pingers
We know very little about the way marine mammals discover (or fail to discover) and respond to fishing nets and gear. Many researchers and fishermen are using acoustic warning devices on gill nets to try to reduce accidents. These small devices are called "pingers" because they beep every few seconds. The hope is that the pinging sounds will warn animals and stop them from approaching the gill nets.

Some studies have shown that pingers are effective with some species of dolphins and porpoises. But scientists do not know enough yet about how marine mammals respond to pingers to draw any conclusions. Pingers may keep some marine mammals away from nets because the pinger sounds interfere with the animals' ability to echolocate and to communicate with each other. We need to test this possibility.

Using pingers may not be a long-term solution if marine mammals become habituated to (used to) them. Over time the animals may stop responding to the sounds because they are not unusual. By observing the captive animals in our study, we hope to examine if a number of species become used to the pinger sounds. Our study is designed to answer questions about how to keep pinger sounds novel and useful, and to try to find better possible solutions than pingers.

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