topic 12 Flashcards
how does aphotic orgaisms survive
relies on food produced in the surface-dead organisms-photic is opposite
nutrient availability in aphotic and photic zones
low phosphate levels-not soluble
runoff into photic zone+upwellibg
freshwater productivity
total productivity is higher but limited by small total area
demersal fishing -2 types
demersal long lining-line oif baited hookks
demersal trawling-
pelgoic fishing types
trawling-tuna is example
drift nets-long net that trap fish
purse seining-net around shoal of fishboat goes around shoal and pulled tight underneath-trapping fish
long lines
environemental impacts of fishing
k selected specie decline-reach sexual maturity at older age-orange roughy-20 years
overfishing could remove breeding populations
issues with byctachfor each type of fishing
Immature fish aare too small to sell
Catch quota may already have been reached-so thrown away
Drift net bycatch-non selective-shark
Pelagic long line-albatross-k selected
Pelagic trawling-trap predators in nets
Demersal-high chance of mixed species
shrimp bycatch-small netting lagrer fish unable to escape
habitat damage
dynamite fishing-stuns fish-used in coral reefs
food chain impacts
se\bed damage-demersal trawling
sea grass beds-trawling may cause disturbance -increased sedimentation-harder for new plants to colonis-important for fishing nursery
how to reduce environmental impacts((
catch quotas
fishing euipment and design-
-mesh size
TEDS-escape panels for turtles
dolphin pingers
hook shape-curved tip hooks-tuna instead of albatross
night fishing-no birds
biodegradbel-redues ghost fishing
restricted fishing methods
ban drift nets
bans on demersal trawling
NTZs-no take zones
closed seasons-allowing fish to grow to a large size
p.t 2 restricted fishing methods
maximum catchable size
protevted individuals-female lobsters carrying eggs
captove breeding and release-
popultain dynamiccs
breeding rates-carrying cap[acity
asult mortality rate
adult population
overfishing
MSY
russell formula
s2=s1+(aA+G)-(C+M)
biomass at end
biomass-beg. year
yong fish added-biomass
biomass added by growth
caught by fishing
lost through mortalilt
why is collecting data difficult
uneven spread of fish population
they are mobile
need a large sample size to be proportional to the total area
data from fishing catches
mean fish size-reducing fish size may show that adult pop. is dclining
data from research what it shows
shows the likelihood of a sudden collapse
colllecting data on planktonic fish eggs-nummber of fish likely to be recruited -allows to aniticpate th elowering of the MSY
Factors affecting aquaculture specie selection
local conditions
market demand
disease res.
rapid growth rate
good apperance
gender control-hormonally when young-rainbow trout-better flavour female-still produce milt but only produces female offspring
control of pests and disease
cirulating currents-less contact between fish- less pathogens
low stock density+pesticides
wrasse to kill lice
competition and predation
fencing+netting-
liscence to cull seald
control of abaiot ic factors
temperature-
dissolved 02-removal of faecal matter
day length-longer day lengths-de;ays maturation-larger-salmon
water flow-reduces collisions-less pathogens
control of limiting factors in salmon aquaculture-
salmon need high 02-water sprays
using antibiotics reduces pathogens
food chain is controlled–low value pellets-sand eels
polyculture
reaerinf species together increasing productivity
example of a polyculture
IMTA
fed aquaculture-large
inorganic extractive aquaculture-absorb of inorganic nutrient seaweed
organic extractive aquaculture -species that catch food items such as plankton
aquaponics
hydroponics+aquaculture
lettuce+tilapia
increasing trophic efficeincy
herbivourous fish-tilapia
carnvorous more demand-low efficiency low basal metabolic rate
FCR
food conversion rate
environmental impacts of aqauculture and how to reduce
Habitat loss-mangroves-careful site selection
Antibiotic resistance -lower stock densities
Wild gene pool impacts-fish escape and breed with local pop.-brighter colour less likely to survive-put eggs under high pressure creating triploid fish-sterile-also bigger
organic waste-faecal matter surplus-deoxygenation-freshwater aquaculture systems have effluent treatment plants
food supply impacts-overfishing of wild pop.-sandeels-use more plant based products -herbivorous plants
aircraft body design how it can be made to reduce noise
high bypass ratio engines-
2 cowlings allows airflow
smooths the follow of the air and reduces the noise
