Fishing and Aquaculture

Question 1

Aphotic zone

Answer 1

Deeper layers of water that receive no sunlight because they are absorbed by shallower layers.

Question 2

Photic layer

Answer 2

The water layer into which light can penetrate.

Question 3

Marine productivity is driven by:

Answer 3

light availability and nutrient availability

Question 4

Where is marine productivity high?

Answer 4

in the photic layer of the oceans near to continental land masses

Question 5

Why is there high nutrient availability near continents

Answer 5

upwelling of nutrients from the ocean floor as deep ocean currents reach continental shelf, runoff of nutrient rich water from land.

Question 6

Where is marine productivity low?

Answer 6

In the centre of large oceans away from land

Question 7

Demersal

Answer 7

Living on the seabed eg cod, plaice.

Question 8

Demersal fishing methods

Answer 8

Demersal trawling, demersal longlining, pots

Question 9

Demersal trawling

Answer 9

a cone shaped net is towed on the seabed to target demersal fish species. The mouth of the trawl is held open by a pair of trawl doors/boards

Question 10

Demersal long lines

Answer 10

Longline fishing uses a line of baited hooks to catch fish. Demersal longlines are typically used in coastal areas on, or close to, the ocean floor and are generally anchored in place. Demersal longlines can be set anywhere from shallow coastal waters to over 1000 metres depth.

Question 11

Shellfish

Answer 11

All the aquatic animals that are caught or grown to be eaten that have shells or an exoskeleton eg crustaceans and molluscs.

Question 12

Shellfish trap/pots

Answer 12

Stationary traps, or pots, typically made from wood, wire netting or plastic, are used to catch crustaceans such as lobsters and crabs. Though the size and shape of traps may vary, all feature a cone-shaped entrance tunnel through which a crab or lobster is enticed with bait, but cannot escape through.

Question 13

Pelagic

Answer 13

Living midwater or near the water surface eg herring, tuna

Question 14

Pelagic trawling

Answer 14

involves towing a large net through the water column to catch pelagic (midwater) fish species. The net has a cone-shaped body and a closed ‘cod-end’ that holds the catch. The trawl net is deployed from the back of the vessel with floats at the top and weights at the bottom to maintain its opening vertically. Angled boards, known as otter boards or trawl doors, attached to the sides hold the net open.

Question 15

Drift net

Answer 15

A net which hangs vertical in the water (like a curtain). The top is held at the surface by floats, with the bottom being held down by weights.

Question 16

Purse seining

Answer 16

A fishing method where a net is used to encircle a shoal of pelagic fish. The bottom of the net is held down by weights and then drawn tight at the bottom

Question 17

Long lining

Answer 17

A fishing method with many hooks attached to a main fishing line that is trailed behind the fishing boat. They can be used to catch pelagic or demersal fish.

Question 18

Environmental impacts of fishing

Answer 18

Overfishing (above the MSY), Bycatch, Ghost fishing, Habitat damage

Question 19

Overfishing

Answer 19

Fishing above the Maximum Sustainable Yield of a population.

Question 20

Bycatch

Answer 20

The non-target organisms that are caught when fishing.

Question 21

Ghost fishing

Answer 21

The capture and death of organisms that get caught in lost or discarded fishing gear.

Question 22

Habitat Damage

Answer 22

Damage/destruction of habitats such as coral reefs, seagrass meadows by destructive fishing methods such as demersal trawling and dynamite fishing.

Question 23

Dynamite fishing

Answer 23

A destructive fishing method that uses explosives to kill fish. It’s illegal worldwide.

Question 24

Reducing the environmental impacts of fishing

Answer 24

Bans/restrictions on destructive fishing methods, designations, no take zones, catch quotas, specific mech size matched to target species, escape panels, acoustic deterrents (pingers), hook shape, decoys, sinkers, night fishing, biodegradable equipment, radio tracked equipment, reduced net tow time, closed seasons, minimum catch size, maximum catch size, protected individuals, captive rearing and release.

Question 25

Marine designations

Answer 25

MCA, MCZ, MPA

Question 26

Catch quota

Answer 26

A limit on the quantity/weight of fish that can be caught

Question 27

Mesh size

Answer 27

the mesh size is set so that fish below a certain size can escape. These fish may be smaller non-target species, or juveniles of the target species.

Question 28

Mesh design

Answer 28

Mesh is designed so that diamond shaped openings become elongated and closed as the net is dragged through the water. Panels of a different shape, that remain open can be incorporated into the net to allow smaller fish to escape

Question 29

Escape panels

Answer 29

A spring-loaded part of a fishing net through which large by-catch organisms can escape e.g. turtles.

Question 30

Acoustic deterrent devices

Answer 30

A device that deters mammals by using sound. They are used to deter small cetaceans from fishing nets, or seals from fish farms, for example.

Question 31

Dolphin pingers

Answer 31

A type of acoustic deterrent device used to deter small cetaceans so they don’t get caught in fishing nets.

Question 32

Hook shape

Answer 32

different hook shapes can target or avoid different species. Hooks with curved points are more likely to catch tuna but less likely to catch albatrosses

Question 33

Decoys

Answer 33

Attract/Distract birds away from longlines

Question 34

Sinkers

Answer 34

Weights that are attached to pelagic longlines to hold the hooks further down in the water to avoid albatross deaths.

Question 35

Night fishing

Answer 35

In particular for longline fishing to avoid bird feeding times.

Question 36

Biodegradable equipment

Answer 36

Pots held together with biodegradable rope so they will degrade and fall apart if lost/abandoned and avoid trapping individuals which will then act as bait for more.

Question 37

Radio Tracked equipment

Answer 37

radio transmitters fitted to equipment that can be activated and recovered if lost.

Question 38

Ban on specific fishing methods

Answer 38

Worldwide or area bans on specific fishing methods that are harmful to important ecosystems. Eg demersal trawling banned off NW coast of scotland to protect deep water corals, dynamite fishing banned worldwide, has been particularly destructive in warm water corals.

Question 39

No take zone

Answer 39

An area in which harvesting or fishing is prohibited.

Question 40

Reducing net tow time

Answer 40

Reducing the amount of time the net is dragged through the water reduces harm to bycatch species, particularly turtles e.g. 99% of turtles survive 10 minutes in a net whereas most die if left for 60 minutes.

Question 41

Closed seasons

Answer 41

ban on fishing a particular species for part of the year which usually includes the breeding season to boost fish populations

Question 42

Minimum catch size

Answer 42

Banning the capture of small fish to allow the fish to grow to a larger size and breed

Question 43

Maximum catch size

Answer 43

Banning the capture of larger individuals to protect the population of breeding adults

Question 44

Protected individuals

Answer 44

Some individuals are marked and then protected from future catches. For example if a female lobster is caught and is carrying eggs, a notch is cut out of the tail so that if it is caught again it will be released to continue to boost the population.

Question 45

Captive rearing and release/population seeding

Answer 45

Eggs/larvae raised in captivity past the point where most would be predated upon and then released.

Question 46

Maximum sustainable yield (MSY)

Answer 46

The greatest amount that can be harvested sustainably.

Question 47

Data required to estimate the MSY

Answer 47

biomass of stock at the beginning of the year, biomass of stock at the end of the year, biomass of young fish added to stock, biomass added by growth of all fish in the stock, biomass caught by fishing, biomass lost through natural mortality

Question 48

Difficulties in calculating the MSY

Answer 48

Fish are mobile and travel long distances and between different populations, distribution of fish is uneven, collecting large amounts of data is impractical, timeconsuming and expensive

Question 49

Assumptions around MSY

Answer 49

The MSY is difficult to calculate so it is often assumed that a fish population can be reduced to down to 30% of the original size and still be able to recover

Question 50

Getting the MSY wrong, The Orange Roughy

Answer 50

The 30% rule assumes all fish are similar to those that we have good data for. Some species are unusual in that their lifespan, age of maturity, reproduction rate differs from the mean. The orange roughy lives for more than 100 years and does not reproduce until 30, this meant that the population recovery rates were much slower than expected and caused both ecological and economic problems.

Question 51

European Union Common Fisheries Policy (EU CFP)

Answer 51

This is a set of regulations intended to ensure the sustainable management of fish stocks within the EU.

Question 52

Cetaceans

Answer 52

Marine mammals including whales, dolphins and porpoises.

Question 53

Aquaculture

Answer 53

The artificial production of aquatic organisms, including fish farming.

Question 54

Principles of aquaculture

Answer 54

Species selection, Selection of breeding adults, Gender control, Control of pests/disease, Exclusion of competition/predation, Control of food supply/nutrition, Control of other abiotic factors (eg temp, light, oxygen, water velocity)

Question 55

Aquaculture species control

Answer 55

species is selected based on demand, value and ease of production

Question 56

Aquaculture selection of breeding adults

Answer 56

The adults which produce eggs/offspring are controlled to produce specific characteristics usually associated with rate of growth, disease resistance and appearance (marketability)

Question 57

Aquaculture gender control

Answer 57

Fish gender can be controlled by giving hormones to young fish. In some species one gender is preferable due to flavour (female trout) or adult size (larger male Tilapia)

Question 58

Aquaculture control of pests/disease

Answer 58

high stocking densities increases risk of pests and disease. Pesticides are used for fish lice. Biological control eg using wrasse to control lice. Water flow is controlled from young fish to older fish to reduce the transfer of established disease.

Question 59

Aquaculture exclusion of competition/predation

Answer 59

Fencing, netting is used on fish cages. Bird scarers are used, culling of predator populations is sometimes authorised eg seals and cormorants in the UK

Question 60

Aquaculture control of food supply/nutrition

Answer 60

Carnivorous fish require artificial feed. Herbivorous fish may require less supplementary feeding.

Question 61

Aquaculture control of abiotic factors

Answer 61

Abiotic factors such as temperature, dissolved oxygen, daylength and water flow are controlled

Question 62

Aquaculture - why control temperature?

Answer 62

Warm temperatures can increase metabolic rate and growth, too warm may reduce dissolved oxygen levels below that required.

Question 63

Aquaculture - why control dissolved oxygen?

Answer 63

required for aerobic respiration, must be high for high stocking densities, decomposition of food waste and faecal matter depletes oxygen so must be removed, some fish can breathe air so less important

Question 64

Aquaculture - why control daylength?

Answer 64

influences reproductive cycle, long daylength delays maturation in salmon and they continue to grow

Question 65

Aquaculture - why control water flow?

Answer 65

fish swim against the flow of water, all fish swimming in the same direction reduces collision/injuries

Question 66

Common aquaculture species

Answer 66

salmon, shrimp, trout, tilapia, scallops, mussels

Question 67

Triploid fish

Answer 67

are a sterile fish with three sets of chromosomes instead of the usual two, resulting in infertility and potentially faster growth rates eg rainbow trout

Question 68

Aquaculture and mangroves

Answer 68

one of the biggest threats to mangroves has been clearance for shrimp aquaculture. Over 10% of mangroves have already been lost to farm species such as Pacific white shrimp and Giant tiger prawns.

Question 69

Aquaculture in Scotland

Answer 69

Scottish salmon farming is a major industry, producing a significant amount of farmed Atlantic salmon, provides both economic opportunities and environmental challenges

Question 70

Extensive agriculture/aquaculture

Answer 70

Agriculture/aquaculture where the yield is achieved with low levels of inputs, often over a large area. Productivity is usually low (yield per unit area) but efficiency is usually high (yield per unit input).

Question 71

Intensive agriculture/aquaculture

Answer 71

Agriculture/aquaculture where the yield is achieved with high levels of inputs. Productivity is usually high (yield per unit area) but efficiency is usually low (yield per unit input).

Question 72

Integrated multi-trophic aquaculture

Answer 72

a sustainable aquaculture approach that mimics natural ecosystems by farming multiple aquatic species from different trophic levels together, utilising waste and byproducts from one species as resources for another eg. shellfish feed upon the waste produced from fish species

Question 73

Impacts of aquaculture

Answer 73

Overfishing of wild fish for feed, habitat loss (mangroves), pesticide pollution, antibiotic resistance, culling wild predators, increase of fish lice transferred to wild populations, escaped fish non-indigenous effects, escaped fish breeding with wild populations, organic waste pollution

Question 74

More sustainable aquaculture

Answer 74

herbivorous rather than carnivorous fish, cage cleaning reduces pesticide use, low stocking density reduces disease and antibiotic use, biological control of lice (wrasse), better cage design to prevent escapes and deter predators, cultivation of species that cannot survive in the wild and become invasive, reduce organic waste by introducing multi trophic feeding.

Question 75

Aquaponics

Answer 75

Aquaponics is a food production system that combines aquaculture with hydroponics, creating a symbiotic relationship where fish waste provides nutrients for plants, and plants filter the water for the fish eg. combining a good hydroponic species like spinach with good aquaculture species like catfish

Question 76

Rice-fish systems / integrated rice-fish farming

Answer 76

a sustainable agricultural practice that combines rice cultivation with aquaculture, it is mutually beneficial for both species. It typically involves freshwater fish and rice and offers benefits like increased yields, diversified production, and reduced reliance on chemical inputs.