Pamphlets on Biology Volume 2735; Kofoid Collection (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1894 Excerpt: ...of More, Norway, precedes, by a short time, Contribution no. 40 from the Woods Hole Oceanographic Institution, Woods Hole, Mass., U.S.A. the appearance of the Sei-whale in these waters. The curve of copepod abundance during 1926 was followed very closely by the curve showing the number of these whales caught, and a distinct parallelism in the fluctuation of copepods and whales was observed to persist during the vears 1926-8. Extensive investigations of the fisheries off the east coast of England, undertaken by Hardy and by Savage, revealed the fact that the herring feed largely on the copepods Calanus and Temora--these animals sometimes comprising more than 75 per cent, of the contents of the stomach. A good correspondence was found to exist between the abundance of planktonic food in the surrounding waters and the quantity of herring caught during the years of the investigation. As an illustration of the amount of food material involved in this relationship, Savage has estimated that 300 tons of plankton would be required for one meal for the 1,000 million herring landed at English east coast ports during 1926. Food not only affects the numerical size of the catch but also regulates to a great extent the rate of development and the quality of the adult fish. Savage has shown that when the food supply is poor, maturity is retarded, and it is suggested that in these circumstances, herring which should spawn in winter may not do so until the following spring. Wimpenny has found that herring feed greedily upon copepods just before they spawn, and that this occurs at a time of year when the fat content of the plankton is increasing. "It seems," he concludes, "that the great congregation of East Coast herring owes its successful reproduction and t...