Trawling is the operation of towing a net to catch fish, and the basic requirements for operating the trawl-net are sufficient power to tow the net , a means of holding the mouth of the net open while towing, a system of wires to connect the net and gear to the source of towing power and the ability to cast and haul the net .

1. Beam-trawl fisheries
STUDENT : EYHAB GAMAL BADRA
MARINE FISHING ENGINEERING DEPARTMENT
FISH RESOURCES COLLEGE – SUEZ UNIVERSITY

2. Characteristics
♦Overview
♦EVOLUTION
♦Plan
♦Accessory Equipment
♦Handling Equipment
♦Vessel Overview
♦Fish Operation
♦Target Species
♦Water Area Overview
♦Gear Environment

3. overview
A beam trawl consists of a cone-
shaped body ending in a bag or
codend, which retains the catch.
In these trawls the horizontal
opening of the net is provided by
a beam, made of wood or
metal, which is up to 12 m long.
The vertically opening is provided
by two hoop-like trawl mostly
made from steel. No
hydrodynamic forces are
needed to keep a beam trawl
open.heads/shoes
beam trawl

4. EVOLUTION
The beam trawl is one of the earliest forms of towed fishing gear,
being used in the Southern North Sea by the sailing smacks from
Grimsby and Lowestoft in the latter part of the 19th century. The net
is held open by a rigid framework ensuring it maintains its shape and
effectiveness despite changes in towing speed. This made it ideal
for towing behind early sailing boats with their unpredictable course
and speed. As diesel engines were developed along with
mechanised hauling methods the gear was made larger and towed
at faster speeds in an effort to improve catches. In the early days of
beam trawling only one net was towed from the stern of the boat.
Nowadays most commercial beam trawlers tow two beam trawls
from long derricks projecting over each side of the vessel.

5. Plan
Principal features of a beam trawl

6. Plan ( continued )

7. Accessory Equipment
While fishing for flatfish the beam trawl is often equipped with tickler
chains to disturb the fish from the seabed. For operations on very
rough fishing grounds they can be equipped with chain matrices.
Chain matrices are rigged between the beam and the groundrope
and prevent boulders/stones from being caught by the trawl. Shrimp
beam trawls are not so heavy and have smaller mesh sizes. A
bobbin of groundrope with rubber bobbins keeps the shrimp beam
trawl in contact with the bottom and gives flatfish the opportunity to
escape.

8. Handling Equipment
Beam trawl is normally towed on outriggers, one trawl on each side.

9. Vessel Overview
Beam trawlers are in most cases specialized medium size vessels,
equipped with powerful engines arranged with large outriggers tow
two parallel beam trawls

10. Fish Operation
Close bottom contact is necessary for successful operation. To
avoid bycatch of most juvenile fishes selectivity devices are
assembled (sieve nets, sorting grids, escape holes). While targeting
flatfish the beam trawls are towed with up to seven knots, therefore
the gear is very heavy; the largest gears weight up to 10 tonnes. The
towing speed for shrimp is between 2.5 and 3 knots

11. Target Species
Beam trawls are used mainly for flatfish and shrimp fishing.

12. Water Area Overview
This technique is very successful used in many parts of the world for
catching shrimp and flatfish normally in shallower depth than 100
meters.

13. Gear Environment
Beam trawls are towed with very close bottom contact.
ImpactsSpecies Conclusions from some recent research on the physical impact
of beam trawls on the sea bed are: 1) the penetration depth of a beam trawl
depends on sediment characteristics and varies between 1 cm and 8 cm; 2) the
pressure force exerted on the sea floor is strongly related to towing speed and
the warp length to depth ratio; 3) beam trawls leave detectable marks on the
seabed. The duration that the beam trawl marks remain visible depends on the
upper sediment layer and on the hydrographic conditions. On the seabed
consisting of medium to coarse sand, tracks have been observed to remain
visible for up to 6 days. On sediments with mainly finer particles a corresponding
figure of 37 hours was observed. The major impact of beam trawl on species is
capture and removal from the ecosystem of small sized organisms (juveniles)
and non-target species, which frequently are discarded at sea. Sieve netting
and selection grids together with larger codend mesh sizes are used to mitigate
this problem, particularly in shrimp trawl fisheries. Square mesh panels are used
with some success to reduce capture of non targets species in flatfish fisheries.

14. References
http://www.ecomare.nl/en/encyclopedia/
http://www.fao.org/fishery/en
http://en.wikipedia.org/wiki/bottom_vessel
BASIC FISHING METHODS pdf