Aquatic food resources

Fishing for species that live on the seabed eg cod, haddock, shrimp

Demersal trawling Demersal long lines

Uses a line of baited hooks to catch species such as cod and haddock

Baited traps to catch crustaceans like crabs,crayfish and lobsters

It includes fishing for species that live in open water above the seabed, often near water surface

Pelagic trawling Drift nets Purse seining Pelagic long lines

Used for species that form shoals in mid water or near the surface E.g. bass, anchovies, herrings, mackerels

Pelagic fish are often in single species shoals Little chance of catching non-target species except predator species e.g. dolphins

Long curtain like nets supported by floats and catch pelagic species near the surface line tuna and herring

Uses a net laid round a shoal Top is held by floats The bottom is held by weights, then pulled tight underneath the shoal Used for tuna, sardines,herring and anchovies

Lines of baited hooks which can be many Km in length Catch species like tuna and squid

Population decline due to overfishing Bycatch Ghost fishing Habitat damage

Population of any species will decline if the mortality rate exceeds the birth rate K-selected species are most vulnerable to overfishing-fewer young at older age Some species reach a catchable size before they reach sexual maturity, so overfishing could remove the entire breeding population

R-selected species because they breed at a younger age and produce more young The populations recover more rapidly after over-fishing E.g. herring, yellow fin tuna

Greenland shark It was fished commercially for lubricating and lamp oil until the 1960s Main threat now is deep-sea trawling bycatch It can live over 400 years, doesnt start breeding until 100-150 years and it produces few young

It will still be maintained by exploited fisheries just further away

The catch that is not wanted Usually non-target species included in the catch of target species, or individuals too small to be legally sold.

Immature fish- too small to sell, will affect future catches If the catch quota for a species has already been reached- must be discarder Species with no commercial value

They are usually dead or will be injured and not survive when they are thrown back into the sea

Purse seine nets/pelagic trawling have a lower bycatch usually than demersal trawling Demersal trawling usually exploits mixed fisheries

They are non selective and will catch any animals swimming near the surface including whales,dolphins,turtles and sharks

Albatrosses caught by long line fishing and drown because of it They have a low reproduction rate, and lay one egg every second year, but it takes 7-10 years before they start breeding So populations can be seriously effected

Pelagic pair trawls for sea bass can kill porpoises Because the porpoises are trying to catch the bass but get trapped in the nets and drown

Seabed fish often live in mixed-species shoals so the chance of catching a mixture of species is high