XIV REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



tion respecting the tiroes of occurrence, the abundance, life histories, 

 habits, diseases, parasites, etc., of the useful fishes and marine inverte- 

 brates. The Boosen process of preserving fresh fish, which has at- 

 tracted much attention in Europe, was given several trials, with the 

 expectation of finding it adapted to the preservation of bait for the 

 offshore fishing vessels, a problem of unusual importance at the pres. 

 ent time. It proved to be entirely unsuited to this purpose, however, 

 the fish placed in it becoming too soft either for bait or for food, though 

 generally free from the offensive odors of decomposition. Many large 

 aquaria were added to the equipment of the lower floor of the labora- 

 tory and fish-hatching building, and under Mr. Seal's arrangements 

 gave excellent opportunities to observe the habits of even large-sized 

 fishes, of which an abundant supply for that purpose was always kept 

 on hand. During the hatching season it was intended that these aqua- 

 ria should be used for the temporary storage of the fry. 



B. — Special Investigatk >xs. 



Temperatures and densities. — One of the most important scientific 

 problems before the Fish Commission has been the determination of 

 the temperature and density of the water along the sea-coasts and in 

 all inland lakes and rivers which afford valuable fisheries, or might be 

 suited to that purpose. The object in studying these physical charac- 

 teristics is at least twofold: First, to ascertain the influence of tem- 

 perature and density on the movements of those migratory fishes which 

 form so large a proportion of the fisheiw production of the country, 

 and the appearance and abundance of which during any fishing season 

 may possibly, in a measure, be predicted by a thorough knowledge of 

 the physical conditions essential to their well-being; second, to fur- 

 nish a guide in the transplanting of fishes and the stocking of any 

 region with the species most likely to survive and propagate. General 

 results are not so important or so applicable to this study as special 

 series of observations continued from year to year. In the furtherance 

 of this object, observations of temperature, and where expedient de- 

 terminations of density, were made at all of the stations of the Com- 

 mission during the entire year, or while operations were in progress. 

 Tfie same observations were made with great care by the vessels of the 

 Commission, whether in port or cruising, and generally at intervals of 

 one hour. The bottom and serial temperatures, and other physical 

 data obtained by the steamer Albatross, on the fishing banks and in 

 deep water, are of special value in the same connection. The most 

 important continuous series of surface temperatures, however, are those 

 taken for the Commission by employes of the Light- House Board and 

 Signal Service along both sea-boards of the United States, at several 

 stations on the Great Lakes, and upon some of the most important 

 shad and salmon rivers on both sides of the continent. This co-opera- 

 tion between the two bureaus just mentioned and the Fish Commission 



