XCII REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



The studies and experiments relative to the propagation of the Span- 

 ish mackerel in Chesapeake Bay begun in June, 1891, were comx)leted 

 later in the same summer, and although the number of eggs obtained 

 and hatched was relatively small, sufficient information was secured to 

 indicate the proper methods to pursue in case it should be deemed 

 advisable to increase the abundance of this importaut food-fish by arti- 

 ficial meaus. The great falliug off in the supjdy of this species which 

 has taken i>lace during recent years would seem to justify such action. 



A case of river pollution brought to the attention of the Fish Com- 

 mission has been thoroughly investigated, and although the results 

 obtained were not entirely conclusive, advantage was taken of the 

 opportuuity to conduct a very interesting series of observations. The 

 Source of pollution is a wood pulp paper mill situated on the banks of 

 the Susquehanna River, the waste liquor from which finds its way 

 directly into the stream. The harmful influence of the sulphurous acid 

 thus discharged was practically demonstrated upon fishes held in con- 

 finement, but it yet remains to be decided whether the volume of water 

 in the river at the site of the mill is sufficient to overcome the perni- 

 cious effects of the acid or not. In smaller streams there could be no 

 question as to the harm produced from such a cause. 



Studies upon the diseases of fishes, a subject which has been very 

 generally neglected, notwithstanding its important relation to the 

 welfare of fishes in general and to successful fish-culture in particular, 

 have been carried on at intervals during the year by Dr. R. R. Gurley, 

 who has been mainly occupied in bringing together the literature on 

 the subject and in preparing a monograph on one of the most extensive 

 groups of injurious parasites, the Myxosporidia. Several special cases 

 of disease have also been made the subject of inquiry. 



CRUISE WITH THE BERING SEA COMMISSIONERS. 



At the beginning of the fiscal year the steamer Albatross was at San 

 Francisco, Cal., prepared to start upon a trip of investigation to the 

 Alaskan coast, where it was proposed to continue the survey of the 

 fishing-banks in Bering Sea, begun the previous summer. 



During the season of 1890 the work had been confined mainly to the 

 extreme southeastern part of that sea, including Bristol Bay as far up 

 as the mouth of the j^ushagak River, but exceedingly important results 

 had been obtained in the development of Baird and Slime banks, the 

 former of very large size and both comparatively little known as regards 

 either their hydrograi^hy or fishery resources. The narrow stretch of 

 shallow water along the northern side of Unalaska Island Avas also 

 explored at the same time, and several lines of deep sea soundings 

 served to define the approximate outer limits of the continental platform 

 as far north as latitude 58° 43' IS"., or about 168 miles northwesterly 

 from St. Paul Island, of the Pribilof group. 



