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Science Frontiers ONLINE No. 30: Nov-Dec 1983 |
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The Problem Of The Precocious Parr
A startling shift in the breeding pat-terns of the Atlantic salmon is taking place in the rivers of North America and Europe. Male parr (parr are young sal-mon that have not yet been to sea) are becoming sexually precocious in large numbers. The small males have up to 20% of their body weight allocated to testes and, in consequence, seem to be bulging from full meals. Actually, they are ready to dart in under mature spawning salmon and fertilize some of the newly laid eggs. Experiments show that the parr are rather successful in their furtive endeavors. The question at hand is why the parr are developing precociously when there are sufficient mature male salmon around to do the job. (Montgomery, W. Linn; "Parr Excellence," Natural History, 92:59, June 1983.)