Passive or static gears are those that are dropped and left in
place for a period before retrieval. They may either attract fish
using bait, or may passively wait for a fish to swim into a net or
trap.
Longlining
Longlining, as the name implies, involves the use of a 'long
line' with a series of baited hooks spread along the ocean floor or
suspended off the bottom, and marked at both ends with buoys.
Usually this system uses automatic hauling, baiting and shooting
machines. The technique is relatively selective for a specific size
of fish (larger hooks catch fish with larger mouths only), but has
some
bycatch problems. The most prominent of these
globally is the bycatch of oceanic
seabirds such as
albatrosses. In north-west European waters, several thousand
northern fulmars are probably killed each year in these fisheries.
Some fisheries also catch many unwanted sharks that are killed in
the process. Turtles and cetaceans are also susceptible to
entanglement in the lines.
Traps and pots
Traps and pots are usually relatively small structures that are
baited and set on the seabed individually or in
groups on a line.
They usually have one or more funnel-shaped openings, which allow
the target species, often lobster, crabs or whelks to enter the
trap but make it difficult to escape. They are set in suitable
habitat for the target species. Some organisms may be crushed or
broken under the pot or trap, but probably a greater problem occurs
when the pots are 'lost' – usually due to the marker buoy line
becoming detached from the pots. Pots will carry on fishing until
they degrade naturally. This ghost
fishing problem can be reduced with the inclusion of easily
degradable elements in the construction of the pot.
Gillnets
Gillnets are nets that catch fish by the gills; trammel nets
catch fish in a pouch of netting. Such nets are used to catch a
wide variety of species, especially in areas where it is difficult
to tow gear. Modern nets are constructed principally of
monofilament netting and may be either held on the bottom of the
sea (with the use of weights and anchors) or left to drift. Drift
nets have recently been phased out for all but a very few
specialist fisheries in Europe. Gillnets can be highly selective
for species and size range of fish, but also entangle larger
organisms such as
marine mammals, turtles, and, elsewhere in the
world,
birds.
Bycatches of harbour porpoises in bottom-set gillnets
represent the greatest threat to the long-term future of that
species in UK waters. Bycatch monitoring and, where relevant,
reduction is a requirement under the EC Habitats Directive.
Currently the only known ways to reduce this bycatch is to reduce
overall fishing effort (possibly through time/area closures) or to
add acoustic alarms (known as pingers) to nets.
Bag/stake Nets
These are large traps used in salmon fisheries. Long panels of
netting are set across the path of migrating fish to divert them
into a net chamber where baffles prevent their escape. Bag nets are
usually set along rocky shores and are emptied by boat while stake
nets are set above the low water mark on beaches and emptied at low
tide. This type of fishing is becoming increasingly rare as inland
salmon fishing interests have bought out many of the licences and
closed the fisheries. Seals often become habituated to feeding at
salmon nets and tear their way into the nets to take the catch.
This conflict has resulted in unknown numbers of seals being shot
by the net operators.