Trawl.
A net dragged along the sea-bottom to gather forms of marine life.
It is a dredge, and is made of heavy and coarse materials for oystermen, and of various kinds and sizes for naturalists in search of the more remote varieties of “all that passeth through the paths of the sea.”
a is a
trawl with a beam ten or twelve feet long to the ends of which are affixed curved iron shoes or runners.
From it depends a funnel-shaped net of perhaps thirty feet in depth, weighted by a string of leads on the forward lower edge.
These weights and that of the runners are sufficient to sink the trawl, and it does not usually need an extra weight in front, on the drag-rope, as does, the dredge.
Projections or webs proceeding from the inside of the net, called pockets, serve to prevent fishes captured in the net from getting out by the route that they go in.
b is a
bag-net with distending hoop, used for catching floating creatures.
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Dredges, trawl, and tangles. |
c is a
dredge the front of which is a rectangular frame of iron, about two feet by eight inches, the long sides extending forward as scrapers, the short sides furnishing points of attachment for handles.
This frame forms the mouth of a tine meshed net about four feet long.
Over the net a canvas bag, open at the bottom, is extended, which serves to protect the
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net from injury while it is dragged over the rocks.
To bring the scrapers down to their work, a weight of about 20 pounds is fastened on the drag-rope about one or two yards in advance of the dredge.
The drag-rope is tied directly to one of the handles, but is attached to the other only by a light line.
The open
iron frame acts as a scraper, and lifts from their bed all the strange forms of life that adhere to the bottom; they are simply scraped up by this contrivance, and, with a great quantity of mud, are caught in the net behind the frame.
d is the
rake-dredge, whose mouth is preceded by an iron bar parallel with it, and bearing a set of sharp-pointed teeth capable of tearing up
Neptune's stubbornest glebe.
The “rake” is essentially a harrow; its especial use is in the case of bottoms of very tough mud or clay, where it is desirable to unearth the animals which are partly imbedded.
Such bottoms are also frequently so serrated with the tough tubes of marine worms as to make the work of the ordinary dredge unsatisfactory: the rake-dredge readily tears through these tubes.
e are
tangles or mops of hemp attached by chains to a bar which has runners and a towing cord.
The
tangles are used to catch small, delicate, or spinaceous forms of marine life, See tangles.
