Fisheries Flashcards
People that depend on fisheries for income
Recreation & Entertainment
Sport fishing
Diving & tourism
Aquarium trade
Sustainable Fishing
fishing up to the maximum sustainable yield so that future fish stocks are not at risk of being depleted
Maximum Sustainable Yield
the intensity of fishing that can be carried out without reducing future populations
Exploitation rate
the proportion of the numbers or biomass removed by fishing
What does sonar mean?
SOund Navigation And Ranging
What is sonar?
a technique which can be used to measure sea depths and locate underwater objects including wrecks and shoals of fish
How does a sonar work?
- Transducers emit sound waves that are reflected by air in the swim bladders of fish like an echo.
- The fish-finder will then measure the time interval for the rebound and determine the distance, direction and depth of the fish.
- Fish have nowhere to hide.
What is a Purse Seine?
A sein net used capture pelagic shoal of fish, it has a series of ropes that are used to close it and trap the fish before hauling them on board
What is the problem with Purse Seines?
Unintended bycatch; i.e. dolphin, sharks, sea turtles
What is the problem with Hook and Line & Long Line?
It is hard to be selective with this gear…but, possible. E.g., choosing bait, jigs, lures, and hook sizes known to catch their target species
What is a gill net?
panel of webbing of clear monofilament line; can be set at any depth; fish can’t see the net, so they swim right into it and are caught
What is the problem with gill nets?
Lots of bycatch (“junk”/non-target) – animals that are too large to pass through the webbing (mammals, turtles, etc.)
What is benthic trawling?
A fishing method that drags a net along the seabed; wooden boards at the front of the net keep the net open and stir up the seabed, causing damage
What is the problem with Benthic Trawling?
- There is a large bycatch
- Trawling can cause considerable damage to the sea floor ecosystem, but the extent of this damage varies according to fishing frequency and the stability of the substrate
- Damage to the habitat may lead to changes in fish stocks through food chains and food webs
What are factory ships?
large, ocean-going fishing boats with on-board processing and freezing facilities.
What is the advantage of factory ships?
They are able to stay at sea for many weeks at a time
What is the problem with factory ships?
These large scale fishing methods can lead to serious depletion of fish stocks and harmful effects on non-target species. This means essentially no respite for the areas fished.
How is income impacted by restricted fishing?
Human communities that are dependent on fishing may experience changes in income as a result of unrestricted fishing and depletion of stocks
How is industry impacted by restricted fishing?
Depleted stock has impacts on the fishing industry itself and associated industries including processing, marketing, distribution and transport.
Equation for recruitment
Recruitment >= natural mortality + fishing mortality
What is recruitment?
Rate of addition of new fish to the population, which depends on the rate of reproduction
How can recruitment occur?
by migration of species e.g. a gradual movement of a population from one areas population to another due to adaptations, a changing of old for young or change in environmental conditions such as gulf stream changes
What is mortality?
The death rate; natural mortality is the death rate arising from natural causes, while fishing mortality is the death rate caused by fishing
What are factors that can affect mortality?
Temperature, pH, CO2 concentration, availability of oxygen, availability of nutrients, fishing effort
What does pelagic mean?
the open sea
How can data on growth be obtained?
Rate of addition of new fish to the population, which depends on the rate of reproduction
What is fecundity?
Refers to the number of eggs/live young produced by a marine organism
What are the ways in which you can monitor fish stocks?
Recruitment, Mortality, Growth, Age of Reproductive Maturity, Fecundity, Habitat
What is demersal?
Region of sea close to seabed, demersal fish live on or close to the seabed
What are the methods to ensure sustainable fishing?
- Setting Fish Quotas
- Restriction by Season
- Restriction by Location
- Restriction of Method
- Restriction on Size of Fish Retained
- Restricting Fishing Intensity
- Market-Orientated Tools
What does restriction by season allow?
- Allow maturation and recruitment
- Protect breeding stock and aggregation sites
- Restrict areas where juvenile fish need to develop
- Restrict fishing methods during migrations to avoid bycatch of migrating animals (whales and turtles)
What does restriction by location allow?
- Protecting breeding locations and areas of juvenile populations ensures recruitment can continue.
- Allows depleted stock a location to recover
- Prevents habitat destruction in sensitive areas
What does restriction on size of fish retained allow?
- Restrict a minimum size to fish to ensure they have matured enough to reproduce prior to being harvested.
- Involves measuring the fish immediately after catch and throwing back fish that are undersized
What does restricting fishing intensity allow?
Regulate:
- Number of boats / fleet size
- Boat sized
- Engine size
- Fishing gear
- Number of boat-days
-Restricting boat size can help the smaller scale fishers and smaller economies to ensure large factory vessels are not taking income from local developing communities.
Name the methods of monitoring and surveillance
- Air patrol
- Sea patrol
- Satellite monitoring
- Inspection of catch
- Catch per unit effort
What is the problem with air and sea patrolling
The area to monitor can be very large = difficult to monitor
What are the advantages of air and sea patroll
- monitor ‘real-time’ fishing
- place observers on boats with little warning
- work together as a team.
What are the disadvantages of air and sea patroll
- there is a high financial cost
- trained staff are required
- they cannot cover all fishing areas
- they can be spotted, and ships may then discard evidence.
Advantages of catch inspcetion
- self-monitoring with licenses, which encourages ownership of fishing regulation by the fishers
- random checks, which allow quotas and fishing methods to be monitored
- fish records, which means that it is easy to trace illegally caught fish back to a particular ship
Disadvantages of catch inspection
- records may be falsified
- if inspectors are present on a ship, fishing practices may be modified
- they are expensive to carry out
- fisheries may distrust the inspectors.
Advantages of Satellite monitoring
- Rapid transfer of information about fishing boats to regulators
- Gathers detailed information about boats
- Reaches all areas of the ocean at all times
- Can gather data about catches as soon as they are taken
Disadvantages of Satellite monitoring
- Costly
- Not all boats have the technology
- Manual inspections still need to be carried out.
- Local authorities required for enforcement.
What is the catch per unit effort?
A measure of fish abundance calculated from the catch size divided by the fishing effort
What is the formula for CPUE
CPEU= fish catch / fishing effort
List some methods of enforcements
- Bans
- Fines
- Confiscation of boats and or gear
- Imprisonment
List some methods of rehabilitation
- Replanting Mangroves
- Building Artificial Reefs
- Releasing Cultivated Fish
