5.3 Impact of exploitation of the oceans

Question 1

Overfishing

Answer 1

occurs when the number of fish that is caught is greater than the rate at which the fish reproduce, leading to a fall in fish numbers in an area.

Question 2

Sustainable fishing

Answer 2

fishing carried out in a controlled manner so that not many fish are caught in a short period of time, this preventing in failure of stock.

Question 3

Causes of overfishing of marine fish species (w/o nets):

5

Answer 3

• Demand for fish as food due to increasing world population
• Fishing all year round.
• Much bigger boats, which can work a long way from a port for many weeks.
• Freezers fitted in boats that help fishermen to stay for longer time at sea.
• Finding fish easily by using SONAR and detailed weather data. Boats that have high technology such as sonar and radar allows the fisherman to sense the approaching shores.

Question 4

Causes of overfishing (nets)

Answer 4

Creation of huge nets that scoop up everything in an area, often half of which is discarded as bycatch (animals caught by fishers that are not the intended target of their fishing effort).
1) Use of small mesh size nets that trap even small fish.
2) Use of dredge nets. These are nets that are dragged on the ocean floor.

Question 5

Impact of overfishing of marine fish species

6

Answer 5

• Reduced catch leading to loss of jobs and reduction in food supply
• Harvest of untargeted/protected/endangered marine species that are discarded at the sea or shore.
• Reduction in marine biodiversity, causing a disruption in food chain.
• The size of fish gets progressively smaller, increasing the demand for food
• lead to the extinction of some fish species
• pollution of marine water bodies as oil spills, and chemicals are discharged into water bodies by fishing boats

Question 6

farming of marine species

Answer 6

Due to the increasing human population, the increased demand for fish as food is above the production capacity of oceans and seas;
Overexploitation of the fisheries leads to a decline in wild fish populations;
So, fish are farmed in controlled environments.

Question 7

Aquaculture:

Answer 7

farming freshwater fish.

Question 8

Mariculture

Answer 8

aquaculture practiced in marine environments e.g. closed sections of an ocean, tanks, ponds, and raceways filled with seawater.

Question 9

how farming of marine species
reduces the exploitation of fisheries

Answer 9

It reduces the pressure on the wild population, allowing their population to increase;
Production is constant;
No bycatch, as non-interest species are unlikely to be present on the farm;
No erosion of seabed, which is usually caused by trawl nets.

Question 10

trawl net

Answer 10

process
* The trawler is dropped into the sea
* its frame or chain makes it sink to the bottom or seabed
* then dragged along the sea-floor and then lifted up along with caught fish

damage:
* The heavy chain dig into the sea-floor and sediments are disturbed, destroys sea-floor habitats
* sometimes the pieces of trawler are left on the sea floor causing pollution and requires long time to recover

Question 11

Dredge net

Answer 11

• dragged along the seabed, mainly catching shellfish and other types of fish living in the mud
• they dig into the seabed with teeth or water jets