Lecture 12 - Fisheries and Aquaculture Flashcards
How many years have we been fishing?
40,000 years
Who described fisheries as an inexhaustible harvest, claiming that the number of fish we catch is insignificant as the multitude of fishes is inconceivably great?
Thomas Huxley (1883)
Describe fishing using a purse seine.
- In open water
- Surrounds a whole school of fish, pulls strings tight to enclose them.
How are most of the world’s tuna caught?
In purse seine nets
What is a disadvantage of purse seine fishing?
Indiscriminate.
A lot of by catch of turtles, whales, dolphins etc.
How do gill nets work?
Intercept fish.
Fine monofilament/transparent mesh that cannot be seen by fish, tangles them.
What is trawling?
The use of a net in a mobile form in open water.
Name some fish caught by midwater trawling.
- Mackerel
- Sardines
- Herring
What is bottom trawling?
Large wooden beams are dragged along the seabed with a thick net or chain mesh.
Catches anything living close to the seabed.
How many times might the same patch of seabed be trawled in a year?
3-5 times
What is a benefit of trawling?
Often has large open panels at the top, allowing turtles and dolphins to escape.
Give three kinds of fish caught by longlines.
- Swordfish
- Marlin
- Shark
How many jumbo jets can fit into some large pelagic trawl nets?
13
Describe the use of SONAR in fishing.
Can see the sea bed and follow contours that the fish might aggregate in, look for trenches, avoid obstructions, view fish in midwater.
SONAR bounces off of fish’s swim bladder, can detect age and size of fish.
How many people do global fisheries provide essential nutrition for?
3 billion
