XX EEPOET OF THE COMMISSIONER OF FISHERIES 



total yield of the Great Lakes fisheries has not declined appreciably, 

 there has been a noticeable reduction in the take of whitefishes and 

 oiscoes, their place having been taken by other less desirable species. 

 An investigation of the more valuable species was undertaken sev- 

 eral years ago and was continued during the past year. 



Two lines of investigation have been followed — one dealing with 

 the systematic relationships of the various coregonine fishes "•(the 

 wJiitefishes, ciscoes,'and related forms), and the other with the life 

 histories and ecology of some of the more important species. The . 

 study has been brought to an advanced stage and much of the ma- 

 terial is already in manuscript form. The life-history studies are 

 also well advanced, and much information has been obtained from 

 an analj'-sis of the scales, including rates of growth in different 

 localities, age composition of the commercial catches, age at sexual 

 maturity, and other related matters. It was found that in the region 

 of Alpena 70 per cent of the commercial take during the summer 

 consisted of fish in their fifth year. It has further been shown that 

 the whitefish in Lake Huron do not ordinarily reach the spawning 

 stage before their fifth year, while the inajority do not spawn before 

 the sixth year. At Alpena only 45 per cent of the females taken 

 during the summer were sexually mature, in spite of the fact that 

 none of the fish were below the legal size limit. It is apparent 

 from these facts that the commercial catch draws to an alarming 

 extent upon the immature fish, which are thus prevented from par- 

 ticipating in the maintenance of the species. Some additional regu- 

 lation of this fishery obviously is necessary if it is to be maintained. 



OYSTERS 



For many years the oyster resources of the Atlantic coast con- 

 stituted our most valuable fishery, but recently the supply in certain 

 important localities has declined to an alarming extent. In spite 

 of this, however, the annual yield approximates 20,000,000 bushels, 

 ^ alued at $14,000,000. The serious depletion of such an important 

 resource as this naturally occasions general concern, and for a num- 

 ber of years investigations have been conducted for the purpose of 

 discovering the cause for it and, if possible, means whereby the 

 siituation might be remedied. . 



During the past year the organization of this work has been en- 

 tirely revised, and it is believed that more rapid progress will be 

 achieved than ever before. Particular attention has been given to 

 conditions in Long Island Sound, where the greatest mortality has oc- 

 curred, due to excessive pollution and the serious overfishing of 

 certain of the inshore areas that were of special importance in the 

 ])roduction of spawn. The effect of various pollutants on the fer- 

 tilization and development of the eggs was studied and extensive 

 experiments in the artificial propagation and culture of oysters 

 carried on. A small hatchery was built at Milford, Conn., and 

 various types of apparatus for rearing the larval oysters were tested 

 out. A new method was perfected, by means of which o^^ster larvae 

 -vvere reared from the egg until they attached to the collectors. The 

 oysters artificially propagated by the bureau during the summer of 

 1923 Avere placed on suitable inshore beds, and by August, 1924, 

 had attained an average size of two and one-half inches. It is 



