396 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
COLLECTING FROM INTERMEDIATE DEPTHS. 
A lianl of the Tanner intennediate tow net usually follows the trawl or dredge, as 
the possible change of depth would not affect its use unless observations are required 
near the bottom ; then it follows the sounding. A dfescription of tlie apparatus and its 
use will be found under the title of “Surface and intermediate collecting.” 
The recorder notes: 
1. Time re(piired to veer each 100 fathoms of rope. 
2. The depth at whicli the net is towed. 
3. The length of rope out and angle at which it is 
towed. 
4. Time and distance the net is towed. 
5. Time of descent of messenger. 
6. Time each 100 fathoms of rope was hove np. 
7. General account of the contents of lower and 
upper nets. 
8. Anything of interest in connection with haul. 
TRIAL LINES. 
Cod and halibut trial lines are extensively used in the exploration of fishing 
banks. They are operated by the crew from the shiii’s rail as she drifts slowly over 
the ground; if she drifts too rapidly, as she is liable to do in boisterous weather, her 
stern is turned to the wind and the vessel is held in jiosition with the propellers, as in 
sounding. The use of trial lines from the rail is practically limited to depths within 
70 fathoms. The fishery expert takes charge of the catch, examines every specimen, 
and keeps a record of — 
1. The numbers and species of hsh taken. 
2. Weight of each fish. 
3. Tlieir length and general dimensions. 
4. Parasites found on them, external and internal. 
.5. Food-contents of stomach. 
6. General physical condition of catch. 
7. Relative abundance. 
8. Bait and apparatus used. 
He preserves a sufficient number of specimens from each station to show the 
general condition of the various species of fish, their food (as shown by contents of 
stomach), and examples of parasites which are found upon them. 
The recorder notes the number of lines used in the trial, the numbers and species 
of fish taken, the duration of the trial, and any further information obtainable. 
Fishing trials from the rail with the vessel underway are limited to fifteen 
minutes or half an hour, and if further examination is required it is customary to 
anchor and send the boats out, or leave them to continue the trial while the ship 
engages in other work in the vicinity. 
THE USE OF TRAWL LINES. 
Whenever an examination is extended beyond ordinary limits trawl lines con- 
taining from 300 to several thousand hooks are employed. They remain on the 
bottom from an hour to half a day, the shorter interval being sufficient for codfish 
and some other species, but not for halibut, which are slow at taking the hook. The 
set is repeated as often as occasion requires. 
The vessel remains by the trawl line, or works in the vicinity, according to 
circumstances. 
GILL NETS. 
These nets are occasionally used at sea, and may properly be included in the 
occupation of a station, though usually employed near land. They may be allowed to 
drift with the current, or anchored at surface, bottom, or at intermediate depths. 
