trawl

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trawl

Sea fishing
1. a large net, usually in the shape of a sock or bag, drawn at deep levels behind special boats (trawlers)
2. a long line to which numerous shorter hooked lines are attached, suspended between buoys
3. Angling another word for troll (sense 2)
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Trawl

 

a pass fishnet towed through the water by a special ship, called a trawler; it is designed to catch fish such as cod, haddock, banded sea perch, and other marine life.

A trawl is a conical sack of netting that is held open by rigid elements (a beam trawl) or by the hydrodynamic forces that arise when the trawl is moved (an otter trawl). The second type predominates in modern fishing. In trawling, the fish enter the mouth of the trawl and are drawn into the cod, which is the narrow end part. After the trawl is hauled on board the trawler, the cod is untied and the fish are unloaded into the hold or onto the deck.

There are several types of trawls, such as benthic, bathypelag-ic, midwater (which catch fish in the midwater, or pelagic zone), and general-purpose. The headropes of the largest trawls are up to 150 m long; the vertical opening of such nets is 30–35 m, and the horizontal opening is 50 m. These trawls pass up to 6,000 cu m of water per sec. Light and electric current are used to prevent the fish from leaving the area of the trawl. Fishing is made more efficient by the use of instruments to monitor the trawl. Such instruments make it possible to keep track of the trawl opening, the level of trawling, and the accumulation of fish in the net. The manufacture of trawls from synthetic materials, such as olefin polymers and polyamides, makes possible a reduction of the hydrodynamic resistance of the trawl and an increase in its wear-resistance and service life.

REFERENCE

Fridman, A. L., M M. Rozenshtein, and V. N. Lukashov. Proektirovanie i ispytanie tralov. Moscow, 1973.

V. V. RANENKO

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

trawl

[trȯl]
(engineering)
A baglike net whose mouth is kept open by boards or by a leading diving vane or depressor at the foot of the opening and a spreader bar at the top; towed by a ship at specified depths for catching forms of marine life.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

trawl

To sift through large volumes of data (e.g. Usenet postings, FTP archives, or the Jargon File) looking for something of interest.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)
References in periodicals archive ?
Observational periods of 35-minutes included a 10-minute pre-trawl period to locate any dolphins that might be in the area, classify the dolphins' behavioral states, followed by lowering the trawl net into the water, dragging it 150 meters behind the vessel for 10 minutes, and then hoisting the trawl net aboard the vessel to separate by-catch.
Initially, two trawl nets were used, one on each side of the vessel, but in the 80's a significant technological innovation was introduced by Korean shipowners, which consisted of using two nets on each side (Pineros & Sieguert, 1981).
In late May 2011, we collected 30 large scallops (4 y old) with the bottom trawl net and 30 small scallops (1 y old) from a cage of the intermediate culture.
Currently there are two main types of fishing gears used for broadband anchovy catches--the Manjubeira and the trawl nets. The Manjubeira is generally more expensive, so it is bought by businessman with greater buying power, and leased to the fishermen who undertake to deliver the fisheries harvest to the owner of the net.
These winches wind multiple strands ofwire cable that tow the main trawl nets. A smaller third winch, the "try-net" winch, is similarly located and drags a small net used to sample the expected catch of the main trawls.
After testing the NMFS TED against a standard trawl net in South Carolina, Georgia, Florida, Mississippi, Alabama, Louisiana, and Texas, NMFS determined there was either no statistical difference or an increase in shrimp retention when using TED's.
The modification of the fishing gear (short funnel trawl net) represented not only a by-catch reduction, but also may be interpreted as possible energy savings, since the less netting material used for the construction of the modified trawl (consequently less netting working area), may generate a smaller trawling resistance, thus may cause a reduction in fuel consumption; however this objective was not directly quantified in this study.
pealeii, however, it seems that escaping devices (e.g., grids) on the top panels of the trawl net could equally allow escape of I.
Our goal was to land each trawl net quickly on the bottom in fishing configuration at a towing velocity of 1.5 m/s (3 kn) and to maintain vessel speed, with the net retaining fishing configuration and proper bottom contact for 15 min (an area of approximately 2.25 ha was swept on average during each tow).
2011), which could also influence disturbance rates of the taller invertebrates like sea whips, we monitored FLH of the trawl net with a recording inclinometer attached to the fishing line, following Hannah and Jones (2003).
where: [Y.sub.IJK] = response variable ([log.sub.10] of catch); = overall mean; [a.sub.i] = season (winter, spring, Summer, autumn); [p.sub.J] = fishing location (Anhembi, Ponte Santa Maria da Serra e Porto Said); [g.sub.K] = fishing technique (trawl net, cast net, beating gill net, gill net, combination gill net and beating gill net); b = linear effect of the covariate; [X.sub.IJK] = covariate ([log.sub.10] of fishing effort, expressed in fishers per day); X' = mean covariate effort; EJ]K = random error component.
The variable of the catching method (trawl net) was found to be important at the 5 % significance level (pless than0.01).