Aquaculture
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What is Imta?
integrated multi tropic aquaculture it is a polyculture system where species in different trophic levels benefit from each other
What is polyculture?
Rearing species together that arent competitors, this increases productivity
Give an example of polyculture
silver carp feeding on phytoplankton bighead carp feeding on zooplankton grass carp feeding on vegetation
What is aquaponics?
hydroponics combined with aquaculture. The water from aquaculture is used in hydroponics because it contains inorganic nutrients from fish faeces. Drained filtered water by the plants is pumped back into aquaculture.
What does hydroponics remove from the water pumped back into aquaculture?
Nutrients that could cause deoxygenation
Examples of species used in aquaponics?
Leafy greens Tilapia, carp
What is the food conversion ratio and how do you calculate it?
the quantity of food required to produce a unit of growth. Mass of food/mass of growth
What is the photic zone?
Above 100m, where light can penetrate water and photosynthesis occurs
What is the aphotic zone?
below 100m, cannot photosynthesise
What is coastal upwelling?
Death of organisms produces DOM which sinks to the seafloor. Deep ocean currents are deflected by a seamount causing the nutrients from DOM to be upwelled to photic zone.
What is demersal trawling?
A net dragged along the seabed to catch species like cod, haddock
What is demersal long lines?
A line of baited hooks along the seabed to catch species like cod, haddock
What is pelagic trawling?
Used a large net dragged in the water. Used for species that form shoals in water like herring.
What is the bycatch of pelagic trawling?
Low by catch Can catch predator species like dolphins
What are drift nets?
Long curtain like nets that are supported by floats and catch tuna/herring
What is purse seining?
Uses a net laid around a shoal of fish, top is held by floats bottom is held by weights and is then pulled tight. Catches species like tuna, herring
What is pelagic long lines?
A line of baited hooks to catch tuna/squid
What are k-selected species?
Species that high breeding age, live longer, have fewer young, reach sexual maturity later Orange roughy, greenland shark
Why is overfishing of k-selected species bad?
They may reach a catchable size before they are sexually mature so overfishing can remove whole populations
What are r-selected species?
Species that breed at a young age, have many young, pregnant many times a year, dont live long. herring, yellow fin tuna
describe the greenland shark
lives to be over 400yrs old but doesnt reach sexual maturity until 100-150 yrs and has few young
Why would by-catch be unwanted?
Fish caught are too small to sell Catch quotas already reached for species caught Species caught has no commercial value
Why is killing immature fish bad?
This reduces the future catches because the young that were killed dont have a chance to grow to catchable size
What is the bycatch of drift nets?
Drift nets will catch everything, whales, dolphins, turtles. High bycatch