Atlantic salmon spawn. Each year salmon return from their feeding grounds in the world's oceans and somehow find the stream or river where their lives began. With death comes the regeneration of life, and the cycle begins all over again. It is one of nature's most moving pageants. Science is providing the answer.
Most salmon really do go home to spawn and die.
The most recent evidence comes from the hills of Vermont, where biologists at Dartmouth College are studying salmon that spawn in the tributaries of the Connecticut River. Biologist Brian Kennedy began with the supposition that all streams are different. As a stream flows over rocks, it picks up natural elements, including strontium, a soft, silver-white metallic element that resembles calcium. According to Kennedy, strontium of different atomic weights, called isotopes, varies from stream to stream, depending on the local geology. He reasoned that the strontium isotopes absorbed in the bones of a young salmon should match the ratio found in its home stream.