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or 10 foot seine with a bag may be used for broader beaches of lakes, rivers, 
and the sea. These nets require two persons to pull them. The bottom of 
the loop of rope joining the top and bottom of the net may be placed under- 
foot (Figure 47) to ensure that the lead line stays on the bottom. Force to 
move the net is applied by leaning forward and pulling with the arms and 
shoulders. Alternatively the seine may be operated with poles tied to the ends. 
The net billows out behind, forming a bag. Seining downstream, except in 
fast water, is said to be more productive. In riffles and rapids the net may be 
fastened across the current and the fish driven down into it by stamping and 
by kicking boulders and other cover. Creosote applied upstream may drive 
the fish down into the fixed net. 
Seines larger than 60 feet may be used but may require more men or a 
winch (unless seine of quite large mesh). Large seines may be set out in deep 
water with a boat and then pulled into shore with long ropes, thus seining a 
large undisturbed area. When pulling seines through vegetation, care should 
be taken to avoid rolling up the bottom of the net. 
Purse seines are large seines which are set out in a circle on the surface. 
The bottom of the net is then closed or pursed by tightening a line which runs 
through rings at the bottom of the net, thus trapping fish within the circle. 
By drawing the net into a boat the fish are gradually restricted into a small 
pocket from which they can be dipnetted. 
Dip nets are often handy to catch fishes attracted to a night light or bait, 
in spawning swarms or those killed by explosives or ichthycides. A metal 
hoop with the netting laced inside with wire makes for durability. 
Gill nets, open-meshed nets which catch by the gill covers or other 
projecting body parts, may yield many specimens. Best results are obtained 
by setting overnight and retrieving early in the morning, the meshes being 
less visible to the fish at night. Frequent removal of fish from the net means 
that specimens are fresher, less abraided by the meshes, less eaten by isopods 
or other scavengers or torn by predators. The nets may be set floating at the 
surface, hung in midwater from the surface, or set on the bottom. To make 
nets easily retrievable buoys should be used ; by so marking the position of the 
nets, boats can easily avoid disturbing them. Setting nets out at right angles 
from shore is often productive. 
It is best to join several nets of different mesh sizes as gill nets are 
selective in the size of fishes caught, e.g., f-, 2-, and 3^-inch (stretched 
mesh) panels may be joined. The length and depth of the net may be varied 
according to requirements. However, if a standard gang of nets is set in a 
standard fashion, catches from different places may be compared. 
McKenzie (1947) and Sprules (1949) described the Canadian prairie ice 
jigger used for setting gill nets under the surface of the ice. By using it, only 
a single pair of holes need be made in the ice. Pulling on a line causes the 
jigger to work along under the ice. When it has gone far enough, a second 
hole is made over the jigger. The net can then be pulled along until set 
between the two holes by means of the rope threaded by the jigger. 
Trawl nets or trawls are bag-like nets which are generally drawn through 
the water by a boat. They provide a most effective collecting method on 
smooth bottoms or in mid-water, even in the deep sea. The bag may be kept 
open by planing boards — otter trawls ; by a pole — beam trawl ; or by vanes — 
mid-water trawls. Long trawl drags should be avoided as they may damage 
specimens. Trawls are themselves damaged on rough bottoms and work 
best on gravel, sand, or mud bottoms. An echo sounder is a valuable aid in 
