Aquatic Resources
Environmental impacts of fishing:
Population decline:
If mortality rates > birth rates, populations decline
Therefore, K-selected species are more vulnerable to overfishing
Ending overfishing:
Stocks have in the last 60 years
2008, fishing limit on bluefin tuna introduced
By-catch:
90% of shrimp fishing is by-catch
Exceeding quotas creates by-catch
Habitat damage*:
Habitat fragmentation: Exposure to predators
Dynamite fishing: Stuns fish using shockwaves; Destroys habitats
All impacts influence the food webs
*Seabeds cannot be destroyed only damaged.
Reducing environments impacts:
Catch quotas:
Limits on the total weight brought back to port and sold.
The quota must be divided up by all boats in a fleet.
Works best for fish found in single species shoals
Fishing equipment:
Trawling nets with built-in escape panels; This allows non-target species to avoid becoming by-catch.
Different net mesh sizes: This can allow juvenile fish to escape nets
Acoustic deterrent devices: Produces sound waves that repel aquatic species which communicate using echolocation.
Biodegradable fishing equipment: Prevents ghost fishing
Different hook shapes/sizes: Specially designed to only catch target species
Decoys: Deter birds from becoming susceptible to ghost fishing.
Restricting fishing methods:
Limiting the time turtles are in nets to prevent them becoming bycatch
Closed Seasons
Minimum catchable size
Maximum Catch Size
Protected Individuals
Captive rearing and release: Population seeding
Species | Min. Catch Size | Min. Breeding Size |
---|---|---|
Cod | 35cm | 60cm |
Plaice | 22cm | 35cm |
Mackerel | 30cm | 34cm |
Aquaculture:
Intensive aquaculture:
High inputs in a small area
Artificial control of abiotic and biotic factors to maximise productivity: High food inputs for carnivorous species; Fish farms; Monoculture; Growth hormones; Small nets; Pesticides.
Extensive aquaculture:
low inputs over a large area
Introducing a fish to a pond and allowing it to feed on wild food: Maintaining habitats; Protection from predators; Natural food; Pest control species; Decreases disease
Species selection:
Location: Does the specie thrive in the local abiotic factors.
Market demand; MEDC’s raise carnivorous species based on flavour/popularity, whilst LEDC’s raise herbivorous or omnivorous species that feed off naturally occurring vegetation or waste.
Selective breeding:
Size
Colour
Quality
Quantity
Disease resistance
Number of offspring
Maturity age
Aesthetics
Fat-muscle ratio
Eggs and milt are collected from mature individuals (sometimes using hormone injections)
Sex control:
Sex in fish can be controlled hormonally, regardless of genetics.
In some species, it is desirable to have a specific sex: Growth rates; Breed stock; Caviar (Andalucía)
Controlling biotic factors:
Increased stock density increases the spread of parasites and diseases.
This is controlled using:Circulating water tanks (fish naturally swim against the flow); Pesticides; Biological control (lump suckers)
In outdoor systems, competition and predators can become a problem.
These are controlled by: Netting; Bird scarers; Culling of predators
Herbivorous fish are more likely to find natural food.
Carnivorous fish need artificial feeding.
Controlling abiotic factors:
Temperature: Dependant on species, warmer temperatures increase growth rates, but decrease oxygen; Increases metabolic reaction rates
Dissolved oxygen: Fish with high oxygen requirements need aerated tanks; Food waste and faecal matter need to be removed; Fish with low oxygen requirements can be kept at greater densities.
Day length: Reproduction is affected by day length; Some species stop growing when they become sexually mature.
Water flow: Fish often swim against the flow of water; This is used to get individuals to swim on the same direction, decreasing collisions and disease spread.
Intensive vs Extensive:
Carnivorous species, like salmon, are fed of small oily (like herring) fish which are caught easily
This is due to them being shoaling species
Polyculture:
Total productivity can be increased by rearing non-competitive species together
Integrated multi-trophic aquaculture
Aquaponics:
A combination of hydroponics and aquaculture
Hydroponic productivity increases because of the nutrients and organic matter supply: Fish faeces is full of nutrients that the plants use
Aquaculture benefits due to the nutrients being removed
The excess nutrients can cause eutrophication
This can cause deoxygenation.
Replacing fishing:
Advantages of aquaculture: High productivity; High food conversion rates (energy ratios); Herbivorous species feed off naturally growing plant species or crop waste
Disadvantages of aquaculture: Carnivorous species have lower productivity; Carnivorous species are fed off fished species; Some species cannot be raised in captivity.
For large scale aquaculture to replace fishing, it needs to become more sustainable
Environmental impacts that need to be reduced include: Food supply impacts; Habitat loss; Pesticide pollution; Development of antibiotic resistant bacteria; Lice control impacts; Wild gene pool impacts; Introduction of non-indigenous species; Organic waste pollution
Practical skills:
Scientists want to investigate whether distance from a river mouth impacts the diversity of corals
Location: In field
Sampling type: Systematic sampling
What is being measured: How many different species of corals in each given area
Equipment: Transect (tape measure), Quadrat
How do you collect the data: Diving down at even intervals, Simpson diversity index
How much data: 30 samples for a statistical test
How do you make the data accurate: Same weather conditions, same tide level
Aquatic Resources
Environmental impacts of fishing:
Population decline:
If mortality rates > birth rates, populations decline
Therefore, K-selected species are more vulnerable to overfishing
Ending overfishing:
Stocks have in the last 60 years
2008, fishing limit on bluefin tuna introduced
By-catch:
90% of shrimp fishing is by-catch
Exceeding quotas creates by-catch
Habitat damage*:
Habitat fragmentation: Exposure to predators
Dynamite fishing: Stuns fish using shockwaves; Destroys habitats
All impacts influence the food webs
*Seabeds cannot be destroyed only damaged.
Reducing environments impacts:
Catch quotas:
Limits on the total weight brought back to port and sold.
The quota must be divided up by all boats in a fleet.
Works best for fish found in single species shoals
Fishing equipment:
Trawling nets with built-in escape panels; This allows non-target species to avoid becoming by-catch.
Different net mesh sizes: This can allow juvenile fish to escape nets
Acoustic deterrent devices: Produces sound waves that repel aquatic species which communicate using echolocation.
Biodegradable fishing equipment: Prevents ghost fishing
Different hook shapes/sizes: Specially designed to only catch target species
Decoys: Deter birds from becoming susceptible to ghost fishing.
Restricting fishing methods:
Limiting the time turtles are in nets to prevent them becoming bycatch
Closed Seasons
Minimum catchable size
Maximum Catch Size
Protected Individuals
Captive rearing and release: Population seeding
Species | Min. Catch Size | Min. Breeding Size |
---|---|---|
Cod | 35cm | 60cm |
Plaice | 22cm | 35cm |
Mackerel | 30cm | 34cm |
Aquaculture:
Intensive aquaculture:
High inputs in a small area
Artificial control of abiotic and biotic factors to maximise productivity: High food inputs for carnivorous species; Fish farms; Monoculture; Growth hormones; Small nets; Pesticides.
Extensive aquaculture:
low inputs over a large area
Introducing a fish to a pond and allowing it to feed on wild food: Maintaining habitats; Protection from predators; Natural food; Pest control species; Decreases disease
Species selection:
Location: Does the specie thrive in the local abiotic factors.
Market demand; MEDC’s raise carnivorous species based on flavour/popularity, whilst LEDC’s raise herbivorous or omnivorous species that feed off naturally occurring vegetation or waste.
Selective breeding:
Size
Colour
Quality
Quantity
Disease resistance
Number of offspring
Maturity age
Aesthetics
Fat-muscle ratio
Eggs and milt are collected from mature individuals (sometimes using hormone injections)
Sex control:
Sex in fish can be controlled hormonally, regardless of genetics.
In some species, it is desirable to have a specific sex: Growth rates; Breed stock; Caviar (Andalucía)
Controlling biotic factors:
Increased stock density increases the spread of parasites and diseases.
This is controlled using:Circulating water tanks (fish naturally swim against the flow); Pesticides; Biological control (lump suckers)
In outdoor systems, competition and predators can become a problem.
These are controlled by: Netting; Bird scarers; Culling of predators
Herbivorous fish are more likely to find natural food.
Carnivorous fish need artificial feeding.
Controlling abiotic factors:
Temperature: Dependant on species, warmer temperatures increase growth rates, but decrease oxygen; Increases metabolic reaction rates
Dissolved oxygen: Fish with high oxygen requirements need aerated tanks; Food waste and faecal matter need to be removed; Fish with low oxygen requirements can be kept at greater densities.
Day length: Reproduction is affected by day length; Some species stop growing when they become sexually mature.
Water flow: Fish often swim against the flow of water; This is used to get individuals to swim on the same direction, decreasing collisions and disease spread.
Intensive vs Extensive:
Carnivorous species, like salmon, are fed of small oily (like herring) fish which are caught easily
This is due to them being shoaling species
Polyculture:
Total productivity can be increased by rearing non-competitive species together
Integrated multi-trophic aquaculture
Aquaponics:
A combination of hydroponics and aquaculture
Hydroponic productivity increases because of the nutrients and organic matter supply: Fish faeces is full of nutrients that the plants use
Aquaculture benefits due to the nutrients being removed
The excess nutrients can cause eutrophication
This can cause deoxygenation.
Replacing fishing:
Advantages of aquaculture: High productivity; High food conversion rates (energy ratios); Herbivorous species feed off naturally growing plant species or crop waste
Disadvantages of aquaculture: Carnivorous species have lower productivity; Carnivorous species are fed off fished species; Some species cannot be raised in captivity.
For large scale aquaculture to replace fishing, it needs to become more sustainable
Environmental impacts that need to be reduced include: Food supply impacts; Habitat loss; Pesticide pollution; Development of antibiotic resistant bacteria; Lice control impacts; Wild gene pool impacts; Introduction of non-indigenous species; Organic waste pollution
Practical skills:
Scientists want to investigate whether distance from a river mouth impacts the diversity of corals
Location: In field
Sampling type: Systematic sampling
What is being measured: How many different species of corals in each given area
Equipment: Transect (tape measure), Quadrat
How do you collect the data: Diving down at even intervals, Simpson diversity index
How much data: 30 samples for a statistical test
How do you make the data accurate: Same weather conditions, same tide level