Beam Trawling Flashcards
When was beam trawling introduced?
Latter part of 19th century
What countries use beam trawling?
Dutch, Belgians, English and growing interest in North and east Scotland
Where does beam trawling take place?
Sometimes operated by small boats by inshore fisheries where modern otter trawl is too large
How is the beam trawl net held open?
-Held open by rigid framework that maintains its shape
-Made it ideal for towing behind early sailing boats with unpredictable course and speed
Where is the beam trawl on the boat?
Modern boats
-Tow two beam trawls from long derricks projecting over each side of vessel
-Early days
trawling only one net from stern
How long is the haul duration for beam trawling?
Usually two hours
What depths are fished by beam trawls
100 m
What species are fished with beam trawling?
Internationally 75% of flatfish like plaice, sole, turbot and brill
-Shrimp
North Sea and Irish Sea flatfish fishery is carried out with beam trawls
How long can the beam be?
12 m
Describe the structure of the beam trawl?
-Heavy steal beam of tubular section supported by steel beam heads at each end
-Beam heads have wide shoes at the bottom which slide over seabed
-Beam and beam heads form rigid framework that keeps net open
Where is the headrope connected to?
The beam
Where is the ground rope fastened?
Fastened loosely between bases of the shoes so that it curves backwards
What is the purpose of tickler chains?
Placed in front of ground rope to drive flatfish from the sea bottom into the net
What are the two types of beam trawls?
-Open gear
-Chain mat gear
What is the chain mat gear beam trawl used for?
For towing over harder, rockier areas of seabed
-Usually used by bigger class of beamers
Describe a chain mat beam trawl.
Is a rig of lattice work of chains towed from the back of the beam sloping down to the footrope of the net
What is the purpose of the lattice work of chains in a chain mat beam trawl?
Guide the trawl over rough ground and boulders on the seabed to minimize damage
What is the purpose of flip up ropes?
To prevent stones from entering the net and damaging it.
Describe the structure of flip up ropes.
Rope mesh fence towed ahead of the footrope to lift the footrope over obstacles
What are some issues with beam trawling?
-Plaice is caught is mixed fisheries with sole in southern North sea using 80 mm mesh size nets
-Result- plaice under minimum of 27 cm landing size which causes high discard rates (50% by weight)
Why aren’t beam trawl mesh sizes increased?
-Increasing mesh size would result in less by-catch and discarding of juvenile plaice
-However this would lead to loss of marketable sole
What is the approximate size of which 50% of female plaice first spwan?
30 - 34 cm
(EU minimum is 27cm)
What are the advantages of beam trawling?
-Effective for flatfish
-Irish sea- catch sole, plaice, lemon sole, (rays and skates by-catch)
-Megrims and monkfish are caught in deeper water
What are the disadvantages of beam trawling?
-One of most destructive forms of bottom trawling
-Sea bed is dug up ecosystem is disturbed
-Hundreds of species of no commercial value are killed - large by-catch
-Mortality caused by tickler chains
-Low discard survival
-Fish in net are injured- reduced commercial value
How has beam trawling affected the North sea>
Reduced the benthic biomass and production 56% and 21% respectively compared with unfished state
What is the discard survival rate of beam trawling?
10% (40% max, but rarely)
How many tickler chains can be used at the same time?
26 chains
What is the minimum mesh size of beam trawls?
80 - 90 mm
What is the EU estimated fishing pressure of trawl fleets?
Two to three times the sustainable level
What are some fish retailers doing in regards to beam trawl policies?
-Some are planning to phase out selling beam trawled flatfish
