Transcript Fisheries 7.PPT

Fisheries
Where Fish Are Caught
• Fisheries: conc. of species suitable for
harvesting
-74%: ocean catch
-16%: Aqua/ Mariculture
-10%:lakes and rivers
Purse Seining
• Long
rectangular net
w/ weighted
bottom edge &
a buoyant top
(cork) is run
around a school
of fish.
• Indiscriminant
method
Wall of
Death
That
feels
good
• Long line of net;
buoyed on top
and weighted on
bottom.
• Each fishery has
specific mesh
size
• Up to a mile long
and hang 50 ft
below 
• Indiscriminant
Drift & Set Gill
Nets
Trawling
• Drag a funnel shaped net open at the
bottom of the ocean
• Shrimp and bottom dwellers…
Trawling
• Tears up habitat on bottom of
ocean  desert
Trawl
Bag for
Shrimp
?????
Longlining
• Long lines of
baited hooks
(1000s)
• Catches open
ocean orgs like
swordfish,
tuna, and
sharks.
• Indiscriminant
Factory Ships
• Seafood is caught, processed (also
fish meal), quick-frozen
Processing Tuna & Salmon
Sport Fishing
• For personal consumption
• Many “catch & release” programs
• Brings in $$$$$ to FWS
Overfishing Leads To…
• Loss of biodiversity
• Loss of potential medicines
• Disruption of food webs
• Increase in disease
• “Ghost” nets keep on killing
• Trawl bags/longlines target turtles 
• Exclusion Devices (E.D.) now
mandatory, lets turtles escape out a
flap in bag
• Bycatch: Fish not wanted thrown
overboard  RIP
• Top Predator Removal:
Weaker/ill fish able to breed 
decreases health of market stock
Shark Fishing
• Cut off fins for cartilage (Shark-fin soup,
Medicines)
– Shark is thrown overboard, alive
• Now Endangered
Mari/Aquaculture
• Farming - fish grown in controlled
environment
• BLUE REVOLUTION!
Organisms Farmed
• Catfish, salmon, abalone, shrimp
Case Study: Salmon Farming
• Kept in pens for 4 yrs
• Harvested at 4-11 lbs
• Fed fishmeal (anchovies) 4lbs = 1 lb
of salmon
Pros to Farmed Fish
• Increase wild pops (not fishing
them)
• Saves human lives
• No ghost nets/bycatch
• Cheaper
Cons to Farmed Fish
• Farmed strains can cross w/ wild
species  destroy genetic biodiversity
• Disease!!  antibiotic fish
• Mass fecal pollution near water
• Large amounts of fishmeal are caught
to feed carnivorous farmed fish.