. 
| 
REPORT OF COMMISSIONER OF FISH AND FISHERIES. 129 
organisms was thus obtained. Those collected in 1889 have been re- 
| ported upon by Prof. W. K. Brooks, in the paper of Prof. Libbey above 
cited, and the material subsequently taken has been referred to Prof. 
Brooks and others for examination. During the first summer Prof. 
Magie took adyantage of the opportunity afforded to secure a set of 
observations on the electric conditions of the atmosphere, which have 
also been published in Prof. Libbey’s report. 
Southern mackerel-grounds.—From May 5 to June 8, 1891, the schooner 
Grampus was engaged in making a series of observations over the 
mackerel-grounds, from Delaware northward to Massachusetts. This 
was in continuation of similar inquiries made in previous years to de- 
termine so far as possible the temperature and other physical phenom- 
ena connected directly with the northerly movement of the advance 
schools of mackerel along the coast. As is well known, these fish 
first make their appearance inside of the warm waters of the Gulf 
Stream at a variable distance north of Cape Hatteras, and work thence 
northward or approach the shores at successively more northern lati- 
tudes. The first schools have generally been seen the very last of 
March or early in April, and previous to the enactment of the law pro- 
hibiting the use of purse seines before June 1, the fishing vessels were 
accustomed to anticipate their coming with much eagerness, making 
diligent search for them, and subsequently following the fish during 
their migrations. In her former cruises over these grounds the Grampus 
was greatly aided by the presence of these vessels, which, scattered 
over a rather wide area, made it difficult for any schools of fish.to pass 
unnoticed. During the last season, however, her work was necessarily 
carried on without this very material assistance. 
The principal object of the cruise was to locate the early schools of 
mackerel, to follow their movements northward or in whatever direc- 
tion they might take, and to learn everything possible regarding the 
conditions of the air and water in connection with their habits. As it 
was somewhat late in the season before the trip began it was expected 
. that the schools were already upon the grounds, and that it would not 
be necessary to proceed very far south before meeting them. Such was 
found to be the case, but the observations were carried southward from 
Woods Holl until the fish were encountered, and thence over a part of 
the area through which they had passed, in order to obtain the neces- 
sary data for comparing the conditions in advance of the first schools 
with those existing in their rear. Subsequently the Grampus followed 
the schools as far as Marthas Vineyard, taking ripe males the last of 
May and ripe females the first of June, in that vicinity. The physical 
observations have not yet been reduced and compared. 
H. Mis. 113——9 ~ 
