Fishing

Question 1

Name the 2 factors that affect marine productivity

Answer 1

Light

Nutrients

Question 2

Outline light as a factor that affects marine productivity

Answer 2

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

Question 3

Outline nutrients as a factor that affects marine productivity

Answer 3

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

Question 4

Define photic layer

Answer 4

The water layer into which light can penetrate

Question 5

What are the two fishing techniques

Answer 5

Pelagic fishing

Dermersal fishing

Question 6

What is pelagic fishing?

Answer 6

Pelagic species live near the surface. They include tuna and mackerel.

Question 7

What is dermersal fishing?

Answer 7

Dermersal species live on or just above the sea bed, which makes it impossible to select the species that are going to be caught

Question 8

Give an example of pelagic fishing techniques

Answer 8

Drift net (e.g. for tuna)

Question 9

Give 2 examples of demersal fishing techniques

Answer 9

Bottom trawling

Demersal longline

Question 10

Estimating the MSY of fish populations is not easy. What information is needed to estimate MSY?

Answer 10

Current total biomass

Annual biomass growth

Breeding rate

Survival rate of each age group

Question 11

Name a fish species that has been overfished

Answer 11

The orange roughy

Question 12

Name 5 environmental impacts of fishing

Answer 12

Bycatch

Factory fishing

Seabed disturbance

Food web effects

Ghost fishing

Question 13

Drift nets can cause bycatch to which species?

Answer 13

Whales, turtles, dolphins

Question 14

Demersal longlines can cause bycatch to which species

Answer 14

Sharks

Question 15

To avoid ghost fishing of lobsters, what do some countries do?

Answer 15

Lobster pots must be held together by biodegradable rope

Question 16

Outline seabed disturbance

Answer 16

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

Question 17

Outline factory fishing as an environmental impact of fishing

Answer 17

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

Question 18

Name 6 ways marine production systems can be managed

Answer 18

Closed seasons 
Protected individuals 
No-take zones
Fishing effort limits
Catch quotas
Minimum catchable size

Question 19

Outline protected individuals as a way of managing marine production systems

Answer 19

Some good breeding animals may be protected such as female lobsters

Question 20

Outline fishing effort limits as a way of managing marine production systems

Answer 20

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

Question 21

Outline catch quotas as a way of managing marine production systems

Answer 21

The total weight of fish that can be landed. Quotas can work well where fish are found in shoals of a single species