106 Conservation Department 



As the survey of the lake proper did not ])egin until July 26 

 it was not possible to determine the production centers of those 

 economically important species which incubate during the winter 

 months and hatch when the ice breaks up in the spring. By July 

 the herring and w^hitefish had dispersed from the spawning 

 grounds and had become sufficiently large to escape the gear 

 designed for earlier stages. However, those species which spawn 

 in spring and early summer were taken, and next year it is 

 hoped that by starring in I\Iay this part of the problem can be 

 completed. 



General Discussion. — Considering the general results of the 

 survey, it can safely be stated that Lake Erie is capable of sup- 

 porting a few^ large fauna of open lake fishes. There are no 

 dangerous silt deposits affecting the spawning beds, the open lake 

 water is not polluted, and there is food in abundance. Only those 

 species which enter the stream mouths to spawn are to date in 

 danger of depletion, from chemical or scAvage pollution. The 

 depletion appears to have resulted from over-fishing and unwise 

 fishing. At least these seem to be the only important factors that 

 have not been tentatively eliminated in the course of the investi- 

 gations. By protecting the spawning grounds during the breed- 

 ing season, by increasing the number of hatcheries, by reducing 

 the number of under-sized fish destroyed in the nets, and, if 

 necessary, by limiting the catch, one may hope for improvement. 

 However, before action by those legislative bodies having jurisdic- 

 tion over the lakes can be wisely taken to protect the spawning 

 grounds, these production centers must be located, evaluated, and 

 the breeding seasons carefully determined. Before perfect stock- 

 ing methods can be devised the natural requirements for success- 

 ful production and development must be ascertained. If the \ 

 greatest mortality is found to take place during the early weeks ; 

 after hatching, it will be desirable to carry those species over the ! 

 critical period before liberating them. Through extensive collect- j 

 ing and plotting of the distribution of different stages the source j 

 and migrations of the young fish may be traced and those areas j 

 most wortliy of protection located. The improvement of the fish- ! 

 ing methods forms a i^art of the program of the Federal Bureau i 

 of Fisheries. , 



Although tlie present investigations indicate tliat Lake Erie is i 

 capable of siipporting a very much larger fish fauna than now \ 

 exists, what in its present depleted condition it is capable of \ 

 producing has not yet been determined. In the light of the present 

 findings the greatly reduced parent fish stock is ajiparently the ' 

 only serious limiting factor at tliis time and every possible effort 

 should be made to ])rotect the fish during the spawning season ] 

 and to find means of decreasing the mortality among incubating ] 

 eggs and develoi)iiig young. The work of the survey to date has | 

 been largely one of elimination, eliminating theories advanced to 

 explain the decline in the fishery. There remains the task of estab- 

 lishing a basis for improvement. 



