aquaculture

the amount of sunlight harvested and converted to energy per metre squared of a habitat in a year (KJm²yr⁻¹)

oceans are less productive than land

light nature temperature dissolved gases

shallow and warm = less currents and upwelling therefore less nutrients in photic zone

seasons affect light winter - low light therefore low algal growth therefore high nutrients summer - high light levels therefore high algal bloom therefore increased use of nutrients so low nutrient level and then limit algae growth

continental shelf, estuaries, sea mounts, upwellings, - on the sea floor as all dead organisms fall to the sea bottom (demersal) = more nutrients = DOM

Cod Haddock flat fish (ambush fish) Dover sole Turbot Shrimp and scallop (filter feeders)

schooling fish (single species shoal) - mackerel sea bass anchovies, sardines, herring (filter feeders) tuna

a net that you drag behind a trawler across the sea surface very environmentally damaging to the floor of the ocean - a lot of bycatch - selective by size scallop dredge - heavy iron marine train - disturbs the sea floor - scallop swim up to try and escape and then get caught

selective by bait preference - Cod, Haddock, Pollock, Colley can reduce bycatch not damaging to the sea floor Can snag and damage coral

drop the lobster pot attached to the line - leave for a while traps crabs and lobsters everything is kept alive when brought onboard selective by bait sustainable - don’t overfish

size selective trawled for a long time = 2 boats sonar to find and target schools lots of bycatch

illegal in majority of oceans not selective - animals can’t untangle mesh - very fine so invisible to organisms

net dragged behind 2 trawlers, Nets then join together and are zipped to create a bag catches tuna and swordfish size selective lots of bycatch can target species by sonar

depth determined by species baited for species selective

k selection - few offspring, high parental involvement, long recruitment time, slow reproduction r selection - fast reproduction, many offspring, little parental involvement, short recruitment time target fish - commercial fish, below fish non-target fish - non-commercial, above quota

size is related to maturity take the big fish out = small fish repopulate

less susceptible to overfishing - e.g. herring, mackerel, yellowfin tuna

more susceptible to overfishing - e.g. orange roughy, shark, bluefin tuna

aerobes - dolphins and turtles etc. other - sharks

long lining - best, selective by bait = less bycatch pelagic trawling - third worst - bad for aerobes - non-specific , selection by size, Shoals tend to be single species so will actively catch predators pelagic drift - second worst - not specific at all - very fine mesh - not selective Demersal trawling - worst for bycatch of fish, ocean floor is a mixed fishery - non-specific, selection by size

albatrosses - scavenging birds, will be caught when going to grab fish but if you bring a long line up at night then they won’t be around

destructive fishing methods - non-specific explosives on coral reefs - used so the nets don’t snag and break on the coral electricity (net and probe with electric pulse to stun the fish) ghost fishing - abandoned fishing gear capturing and killing fish direct habitat damage - Trawl and dredge

Deep sea coral reefs shallow waters - kelp forest and seagrass beds which both habitats act as nurseries for young fish