Fishing Flashcards
Name the 2 factors that affect marine productivity
Light
Nutrients
Outline light as a factor that affects marine productivity
Autotrophs in deeper water are free floating phytoplankton
Turbidity can reduce the depth of water that light can penetrate
In polar regions, the sun never sets in summer and never rises in winter. These changes can produce great seasonal variations with summer algal blooms that support rich food webs
Outline nutrients as a factor that affects marine productivity
Marine autotrophs absorb nutrients directly from the water because there is no soil
Some essential nutrients are always abundant such as CO2
Others can be a limiting factor when they are not abundant such as nitrates and phosphates
Define photic layer
The water layer into which light can penetrate
What are the two fishing techniques
Pelagic fishing
Dermersal fishing
What is pelagic fishing?
Pelagic species live near the surface. They include tuna and mackerel.
What is dermersal fishing?
Dermersal species live on or just above the sea bed, which makes it impossible to select the species that are going to be caught
Give an example of pelagic fishing techniques
Drift net (e.g. for tuna)
Give 2 examples of demersal fishing techniques
Bottom trawling
Demersal longline
Estimating the MSY of fish populations is not easy. What information is needed to estimate MSY?
Current total biomass
Annual biomass growth
Breeding rate
Survival rate of each age group
Name a fish species that has been overfished
The orange roughy
Name 5 environmental impacts of fishing
Bycatch
Factory fishing
Seabed disturbance
Food web effects
Ghost fishing
Drift nets can cause bycatch to which species?
Whales, turtles, dolphins
Demersal longlines can cause bycatch to which species
Sharks
To avoid ghost fishing of lobsters, what do some countries do?
Lobster pots must be held together by biodegradable rope
Outline seabed disturbance
Dredging involves dragging heavy nets across the seabed, some of which have balls or chains to disturb the seabed and bring organisms up to the surface
Outline factory fishing as an environmental impact of fishing
Factory ships have been developed to store large numbers of fish. These require large amounts of fuel. Also, the effluent from processing the fish is discharged into the sea where it is broken down and can cause deoxygenation
Name 6 ways marine production systems can be managed
Closed seasons Protected individuals No-take zones Fishing effort limits Catch quotas Minimum catchable size
Outline protected individuals as a way of managing marine production systems
Some good breeding animals may be protected such as female lobsters
Outline fishing effort limits as a way of managing marine production systems
If the fishing effort is reduced then the catch size should also be reduced
This can be achieved by setting limits on the number of nets, boats, days spent fishing.
Where a fishing fleet is too large, there may be a compensation scheme where fisherman are paid to sell their boats and stop fishing
Outline catch quotas as a way of managing marine production systems
The total weight of fish that can be landed. Quotas can work well where fish are found in shoals of a single species
