Aquatic food resources

Question 1

What abiotic factors can influence marine productivity?

Answer 1

Temperature, dissolved CO2 level, turbidity and light levels

Question 2

What is the aphotic zone and what does it rely on?

Answer 2

Area of water where light does not reach, it relies on the food produced near the surface, e.g. planktonic algae that is carried down by water currents, or the bodies of dead organisms that sink

Question 3

What are the different types of fishing?

Answer 3

Demersal (organisms that live near or on the bottom of the water body), shellfish traps and pelagic (organisms that live in open water) fishing

Question 4

What is demersal trawling?

Answer 4

Demersal involves fishing for species on the seabed, such as cod, haddock, plaice, shrimps and scampi

Question 5

What are demersal long lines?

Answer 5

Use of line of baited hooks to catch species e.g. cod and haddock

Question 6

What animals do shellfish traps catch?

Answer 6

Baited traps that catch crustaceans e.g. lobsters, crabs and crayfish

Question 7

What is pelagic trawling?

Answer 7

Used for species that form shoals in mid-water or near the surface e.g. bass, anchovies, herding and mackerel, pelagic fish often form single-species shoals so the catch of non-target species is usually low, but predator species may also be caught accidentally e.g. porpoises and dolphins

Question 8

What is drift net?

Answer 8

Long curtain-like nets that are supported by floats and catch pelagic species near the surfaces e.g. tuna and herring

Question 9

What is purse seining?

Answer 9

A net that is laid around a shoal of fish, the top is held up by floats, the bottom is held down by weights then pulled tight underneath the shoal, used for sardines, herring, anchovies and tuna

Question 10

What are pelagic long lines?

Answer 10

These use a line of baited hooks which can be many kilometres in length, used for squid and tuna

Question 11

What are the environmental impacts of fishing?

Answer 11

Overfishing, bycatch, ghost fishing and habitat damage

Question 12

How is the common skate impacted by fishing?

Answer 12

K-selected species, it’s not commercially important, however, it is often caught in by catch of demersal trawls. It has become extinct in the Baltic Sea and Critically Endangered in the Mediterranean Sea and NE Atlantic

Question 13

How is the Greenland Shark affected by fishing?

Answer 13

K-selected species that was fished commercially for lamp and lubricating oil until the 1960s, it’s main threat now is by catch from commercial deep water trawling

Question 14

Why may a species be considered by-catch?

Answer 14

If the catch quota has already been reached, immature fish of the target species that are too small to sell and species that have no commercial value

Question 15

What species are commonly caught as by-catch in shrimp trawling?

Answer 15

Crabs, sea urchins, molluscs and starfish

Question 16

How are albatross birds impacted by fishing?

Answer 16

K-selected species that are commonly caught in pelagic long line fishing, they dive into surface waters for their food where they may get caught on the lure put out for squid or fish and drown

Question 17

What’s a common pelagic trawling by-catch?

Answer 17

Porpoises are trying to catch the bass when they become entangled

Question 18

What is ghost fishing?

Answer 18

Fishing gear that has been discarded or lost may continue to trap and kill marine organisms, the dead organisms in the gear often act as a bait and trap more animals

Question 19

What habitats are affected by fishing?

Answer 19

Coral reefs, seagrass beds and seabed damage

Question 20

Why are seagrass beds important?

Answer 20

Nursery grounds for many species of fish that may live on coral reefs or in deep water as adults

Question 21

How does trawling impact seagrass beds?

Answer 21

Kills the plants so their roots no longer hold the sand grains together, currents and waves move the sand around, making it more difficult for new plants to colonise and become established

Question 22

How does dynamite fishing work?

Answer 22

The pressure waves released by underwater explosions can stun fish and make them easy to catch, the use of dynamite is illegal in most countries but it is still carried out in remote areas, it is particularly common method on coral reefs where nets cannot be used to catch the fish that live among the coral heads , the explosions destroy coral and kill many other organisms

Question 23

How does the mesh impact fishing?

Answer 23

Size can be set so certain smaller fish can escape, the design can be modified by adding the mesh pattern at right angles so they do not close up and smaller fish can escape

Question 24

What are acoustic deterrent devices?

Answer 24

AKA Dolphin pingers, produce high frequency sound to warn dolphins that nets are nearby

Question 25

How can hook shape be changed to save albatross?

Answer 25

Long line hooks with curved points still catch tuna but less likely to catch albatross

Question 26

What are Turtle Exclusion Devices?

Answer 26

Large spring loaded escape panels in the nets which allow turtles to escape

Question 27

What are sinkers?

Answer 27

Weights attached to pelagic longlines hold the hooks down in the water s they still catch fish, but not birds

Question 28

Why is biodegradable and radio tracked equipment desired?

Answer 28

Reduces ghost fishing

Question 29

What equipment design can be changed to prevent birds getting caught?

Answer 29

Hook shape, night fishing, decoys and sinkers

Question 30

What are NTZs?

Answer 30

No Take Zones are areas where fishing and other activities that exploit wildlife or damage the habitat are not permitted. This protects the breeding populations, especially larger individuals,

Question 31

How is turtle by-catch reduced by restricted fishing methods?

Answer 31

Reducing time a net can be trawled, if the trawl is less than 10 minutes, survival is 99%, if it is over an hour it’s 50-100%

Question 32

What are some other restricted fishing methods?

Answer 32

Closed seasons, minimum and maximum catchable size, captive rearing and release and protected individuals

Question 33

What is captive rearing and release?

Answer 33

Wild populations can be increased by releasing individuals that were raised in captivity

Question 34

How is the Atlantic cod impacted by fishing?

Answer 34

They reach a catchable size at 2 but don’t mature until 4, so excessive fishing can remove the majority of the breeding population

Question 35

How is the Orange Roughy impacted by fishing?

Answer 35

K-selected species, they live for 150 years, but only reach maturity at 30 years and produce few eggs

Question 36

Why can collecting data on fish be difficult?

Answer 36

Populations can move long distances, distribution of populations is very uneven or it may be impractical to collect representative data

Question 37

What data can be collected from catches?

Answer 37

Catch size (population estimation), mean fish size or age and catch per fishing expedition is an estimate of decline in populations

Question 38

What is extensive aquaculture?

Answer 38

Minimal inputs which may simply involve a pond where fish have been introduced to feed on the wild food naturally present before being caught when they have grown e.g. oysters

Question 39

What is intensive aquaculture?

Answer 39

Involves artificial control of all abiotic and biotic limiting factors, to maximise productivity and therefore profitability e.g. salmon, cod, trout and prawns

Question 40

What are some desired characteristics of fish for selective breeding?

Answer 40

Rapid growth rate, disease resistant and good appearance e.g. bright colour

Question 41

How is breeding impacted by gender?

Answer 41

Gender can be controlled hormonally, regardless of their genetics, each species can be changed by hormone injections

Question 42

When may different genders be more desired?

Answer 42

Males can be more energy efficient and grow larger (tilapia), whereas females sometimes have better taste (rainbow trout)

Question 43

What are the problems with aquaculture?

Answer 43

Disease and pests spread rapidly, competition and predation and nutrition

Question 44

What abiotic factors need controlling in aquaculture?

Answer 44

Day length, dissolved oxygen, temperature and water flow

Question 45

What is inorganic extractive aquaculture?

Answer 45

Desired species absorb inorganic nutrients to allow growth, an example is seaweed

Question 46

What is organic extractive aquaculture?

Answer 46

Organisms (usually filter feeding shellfish) that catch their food such as plankton

Question 47

What are some of the methods of aquaculture?

Answer 47

Polyculture, integrated multi-trophic, aquaponics and rice fish systems

Question 48

What are the methods of reducing environmental impacts of fishing?

Answer 48

Catch quotas, improved design of fishing nets, restricting fishing effort and restricting fishing methods

Question 49

What are examples of improvements to fishing methods?

Answer 49

Larger mesh size, mesh design so nets are at right angles to the direction of movement and smaller species can escape, acoustic deterrent devices, hook shape, decoys, sinkers, night fishing (reduce bird harm) and biodegradable and radio tracked equipment

Question 50

What factors impact the choice of species for aquaculture?

Answer 50

Local conditions and species adaptations and market demands

Question 51

What abiotic factors need to be controlled in aquaulture?

Answer 51

Temperature, dissolved oxygen, day length and water flow

Question 52

How does day length impact aquaculture?

Answer 52

Some fish like salmon stop growing once they reach sexual maturity, extending the day length delay maturation and increase growth of fish

Question 53

Intensive vs extensive in shrimp production

Answer 53

Shrimp feed on plankton naturally produced in the lagoons of extensive systems
Intensive systems add nutrients to increase the growth of algae, food pellets may also be added, water may be exchanged to remove wastes and aeration may be needed to prevent deoxygenation as wastes decompose

Question 54

What’s the breeding process for salmon aquaculture?

Answer 54

Fish are chosen with desirable characteristics and adult fish are stripped of their eggs and milt, these are mixed to allow fertilisation and the young fish are moved through a series of tanks from 12-18 months before being placed in seawater, they are fed food pellets and then harvested at 3-5kg

Question 55

What controls are in place for limiting factors in salmon aquaculture?

Answer 55

Lower temperature, water sprays or weirs to aerate the water, high flow rate to produce muscular fish, constant flow direction to minimise injury, removal of diseased fish and selective antibiotics and pesticides used

Question 56

What is fed aquaculture?

Answer 56

Species in a IMTA that are given food

Question 57

What is aquaponics?

Answer 57

Combination of hydroponics from agriculture and aquaculture, Aquaculture water is used in hydroponics and then drained back into aquaculture

Question 58

What are suitable hydroponic and aquaculture species for aquaponics?

Answer 58

Lettuce with carp

Question 59

What is food conversion ratio?

Answer 59

The quantity of food required to produce a unit of growth, if 3.5kg of food is needed for 1kg of growth the FCR is 3.5