Fisheries Flashcards
Upwelling Areas
Rising currents in the water column bring nutrient-rich water to the surface
Continental Shelves
Relatively shallow, highly productive
Estuaries
- Mixing of salt and fresh water
- Streams empty into oceans
- Important nursery areas
Open Ocean
- Less productive
- Fisheries target larger migratory species
What happened to fishing practices when class-divided urban societies emerged five thousand years ago?
Fish were caught for sale rather than consumption
* Serving fresh fish was seen as a status symbol for the rich*
What is the fish event horizon?
The rapid expansion of commercial fishing in the North and Baltic seas
What is the significance of the Industrial Revolution in regards to the rising industry?
Steam powered vessels replace sailboats
Fishermen can travel farther and fish in deeper waters
Describe the technological advancement of fishing
1930s: Electrically generated sound pulses are used to locate fish
1950s: Fish-finding echo sounders work vertically allowing fishermen to see fish below the vessel
- Sonar is applied to search horizontally around the boat
- Radio and satellite transmissions tell fishermen where fish are and where they are going
What information can fishermen receive from sonar?
- Size
- Abundance
- Movement
Passive sonar
Listening for sounds made by a vessel
What event lead to the advancement of the sonar technology that is commonly utilized in marine research today?
WWII
Submarine warefare
Active sonar
Emitting pulses of sounds and listening for echos
What is the biggest technological advancement that lead to overfishing?
Fish echo sounders
How are radios and satellites utilized by fisheries?
They tell fishermen where the fish are and where they are going
What is a fishery?
Areas where fish are caught for commercial or recreational purposes. This can be a body of water or fishing activities.
Not just referring to fishing vessels
What are the three different types of fisheries?
- Commercial
- Recreational
- Subsistence
Subsistence Fishing
- Fishing for personal, family and community consumption
- Noncommercial
- Traditional methods (no big fishing vessels)
- Fish used for food, shelter, clothing etc.
- Crucial for sustainable livelihoods
Recreational Fishing
- Fishing for sport or pleasure
- Integral part of American coastal life
- important economic driver
Commercial Fishing
- Fishing for commercial profit
- Mostly from wild fisheries
- Provides large quantities of food to many countries around the world
Longline
- Trail a long line behind a boat
- Bait hooks attached to nets at intervals in order to attract fish
- Used for pelagic (midwater) or demersal (bottom) fishing
- Can span up to 60 miles long
- Can have unintended impacts on non-target fish, birds, and other life
Gillnets
- Wall / curtain of net that hangs in the water
- Size of fish caught depends on the size of the net meshing
- Hard to target specific fish –> High bycatch
- No disruption of benthic habitat
Purse Seine
- Used for dense schools of single-species fish (ex: tuna)
- Vertical net surrounds fish then bottom is drawn together
- Bycatch = low
- No contact with seabed
Pots and Traps
- Made from wood, wire, or plastic
- Used to catch crustaceans (ex: lobster / crab)
- Cone shaped entrance (animals can climb in but cant escape)
- Deployed on the seabed for ~24 hours
Pelagic Trawl
- Cone shaped / closed at one end to trap fish
- Pulled through mid-water NOT seabed
- Acoustic technology (sonar / echo-finders) locates position and depth of fish
- Methods are employed to limit bycatch
Dredging
- Rigid structure towed along seabed
- Bar (with / without teeth) dislodges shellfish as it drags over sediment
- Used to catch bivalves (oysters, scallops, and clams)
- High ecological damage
Bottom Trawl
- Cone shaped / closed at one end to trap fish
- Pulled just above or on seabed (does NOT dig up benthic community)
- Efficient in capturing large numbers of fish
- Large impacts through bycatch and seabed damage