IT— SOME PLANKTON STUDIES IN THE GREAT LAKES. 



BY JACOB E. REIGHARD, 



Professor of Animal Morphology, University of Michigan. 



The history of the wh itefish industry of the Great Lakes is well known to the mem- 

 bers of this conference. It is presumably the history of a diminishing production in 

 spite of a very large annual outlay for artificial propagation. The enthusiasm with 

 which the fish-culturists of twenty years back undertook the restocking of the Great 

 Lakes was born of success in many similar enterprises. Trout and shad had been 

 made to swarm in depleted waters. Similar results were, therefore, to be expected 

 from the application of similar methods to the Great Lakes. These expectations have 

 not been realized, and fish-culturists are casting about for an explanation. 



On the one hand it is asserted that the expected increase in the yield of whitefish 

 has not been realized because of the destructive methods of fishing. The ravages of 

 the pound net are thought to be more than sufficient to wipe out the gain due to arti- 

 ficial propagation. It is said that if fishing methods were properly regulated the 

 results of artificial breeding would at ouce make themselves felt, and that, while the 

 planting of whitefish has not resulted in increasing the supply of adult fish, it has 

 prevented any large reduction in that supply, so that many grounds, which now pay 

 for the fishing, would have been utterly exhausted but for artificial propagation. The 

 remedy for the present condition of things is believed to lie both in legislation con- 

 trolling fishing methods and in a still greater extension of artificial propagation. 



On the other hand it is claimed that if the artificial propagation of whitefish were 

 successful it should result in an increasing yield in spite of existing methods of fishing. 

 The remedy does not lie in restrictive legislation; it lies rather in greater effectiveness 

 of methods of artificial propagation, and perhaps also in an increase of the annual 

 output of artificially hatched fish. 



The first view is held for the most part by fish-culturists, who favor restrictive 

 legislation and increased facilities for artificial propagation. The second view is held 

 for the most part by fishermen, many of whom are not yet convinced of the value of 

 artificial propagation. When one who is neither fish-culturist nor fisherman attempts 

 to discover the facts upon which the various opinions are based he very soon finds 

 that there are but few recorded facts. 



In order to know whether the number of whitefish is increasing or diminishing 

 for any locality or for all localities it is necessary to have statistics extending over a 

 term of years. Statements based on statistics which are taken in two years separated 

 by an interval of five or ten years are nearly valueless for purposes of comparison, for 

 the reason that such statistics do not and can not take into account the climatic con- 

 ditions which make one year favorable and another year unfavorable. The fact that 

 in the year 18S0 the number of whitefish marketed was greater than in 1890 does not 

 prove that the number of whitefish has diminished in this interval ; it proves only 



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