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
How many people rely on fish as their main source of protein?
1 billion
How much are fisheries worth per year?
$80 billion
How many commercial fishermen and fish farmers are there?
38 million
How much more fish do we need to be catching by 2030?
35% more fish
From 106 million tonnes to 143 million tonnes
What is the ratio of by catch in shrimp trawling?
20:1
What is the Discard Ban for the EU?
States that fishermen must land things, cannot throw them back.
What does IUU fisheries stand for?
Illegal, Unreported, Unregulated fishing.
How much are IUU fisheries valued at?
$10-25 billion
What is the most rapidly increasing food production market in the world?
Aquaculture
How much less is the North Sea biomass of fish than without fishing for fish of size
a) 4-16kg?
b) 16-66kg?
a) 4-16kg = 97% less
b) 16-66kg = 99% less
How much has the biomass of high trophic fish declined in the last 50 years?
By 66%
Within 15 years of exploitation, how much do industrialised fisheries reduce biomass by?
80%
What percentage of stocks are
a) Facing collapse?
b) Overexploited?
a) Facing collapse = 30%
b) Overexploited = 40%
True or False:
There are no underdeveloped fisheries in the world.
TRUE.
What percentage of fisheries are still developing?
5-10%
Describe the work of Boris Worm et al (2006).
Looked at the number of collapsed taxa.
50-60% of taxa collapsed.
Describe the work of Pauly et al (1998).
Described how the trophic level of the community changes within time – showed that trophic level drops.
What is the maximum sustainable yield?
The population size at which it produces the maximum number of offspring available for harvest.
What percentage more additional protein needs to be produced by the sea by 2030?
40%
