Fisheries and conservation - Part 3

Question 1

Rank, by selectivity, the different fishing techniques.

Answer 1

Trawling
Purse seines
Longlines
Gillnetting
Harpooning/angling

Question 2

Describe trawling

Answer 2

Drag big net behind the boat for a large distance catching most every thing.
Least selective.

Question 3

What are the benefits of trawling?

Answer 3

Easy, catches a lot, good economically

Question 4

What can be regulated for trawling?

Answer 4

Mesh size.

Larger size will allow smaller fish and babies through.

Question 5

What are the issues with trawling?

Answer 5

Least selective.

Destructive to habitat, specifically deep-water trawling. (coral reefs and seagrass beds)

Question 6

How are purse seines more selective than trawling?

Answer 6

Only set when the target fish is found.
Selectively target fish species they catch.
Modified to avoid dolphin catching.

Question 7

Describe longlines.

Answer 7

Long lines of hooks, km or more long, can be baited.

Come back to collect after a period of fishing.

Question 8

How are longlines selective?

Answer 8

Primarily target larger, predatory fish.
Will catch any species large and hungry enough to bite hook.
Not selective in terms of species but, size and predatory selective.

Question 9

How has bycatch changed the way longlines operate?

Answer 9

Modified to go deeper and changed to hooks to prevent non-fish bycatch.

Question 10

What is a major issue to longlines?

Answer 10

By the time you come back, fish are already dead.

Can get lost and continually fish for a long time.

Question 11

Describe gill nets.

Answer 11

Nets that catch fish by the gills.
Allow fish heads to go through the net but not the body. Fish will then try to swim back but get net caught in operculum.
Left then, harvested later.

Question 12

How is gillnetting selective?

Answer 12

Size selective.
Large headed fish and baby fish will not be caught.
Size selective but not species selective.

Question 13

Describe the controversy with longlines and gill nets.

Answer 13

These can be lost during a storm or due to a satellite issue.
They can keep killing fish and other animals for years.

Question 14

What are the regulations for gillnetting and longlines?

Answer 14

Pretty much unregulated and heavily used.

Only regulation is on mesh size.

Question 15

How can harpooning and angling be used commercially?

Answer 15

They have very little bycatch (if at all) and are the most sustainable.
However, they both arent particularly efficient and are only worthwhile is the fish is large enough.

Question 16

As we overfish, we have a tendency to fish _____ the _____ _____.

Answer 16

down the food chain

Question 17

Describe a redsnapper and a whitefish.

Answer 17

Anything semi red is called a redsnapper

Anything semi white is called a whitefish

Question 18

Aquaculture.
What do most big fish eat?
What happens after fish eat?

Answer 18

1 - Other fish

2 - Fish poop

Question 19

In aquaculture, _______ systems may be okay but oceanic ___ ____ are particularly bad.

Answer 19

Inland

Net pens

Question 20

Why doesn’t aquaculture solve the fishing problem in some instances.

Answer 20

Have to feed the fish in the farm with other fish.

Question 21

Fish _____ is a large issue in regulation of fish farms.

Answer 21

waste

Question 22

Why is an inland system better than an oceanic system in terms of wastes?

Answer 22

Can treat inland wastes.

If the farm is in oceanic waters, just hope it washes away.

Question 23

What are the different aquaculture set-ups?

Answer 23

Net pens
Ponds
Raceway
Recirculation

Question 24

What are the benefits of net pens?

Answer 24

No water chemistry issues.
Can have high fish densities
Can keep in bay for high accessibility
Relatively inexpensive

Question 25

What are the problems with net pens?

Answer 25

Fish density is high so, if not placed correctly, can get waste buildup
Habitat can get degraded due to wastes
Fish escape can occur whereby the fish outcompete the native ones (ex: Atlantic and Pacific salmon)
Diseases

Question 26

Describe the benefits of a pond.

Answer 26

Inland system

Water comes from ocean so water chemistry is generally not an issue

Question 27

What are the problems with ponds?

Answer 27

Generally near shore so can have issues with wastes and can be devastating to coastal environments

• i.e. may need to build near the coast and destroy estuary or forest buffer strip
• can have buildup of wastes in coastal areas, degrading them

Question 28

What are the benefits to recirculation systems?

Answer 28

Waste problem eliminated
Less environmental damage
Doesnt need to be near an ocean or coastal areas

Question 29

What are the problems with recirculation systems?

Answer 29

Expensive for maintenance
Have to carefully monitor water chemistry
Fewer fish
Still might not take care of overfishing issue

Question 30

What is the best way to get around the overfishing issue with aquaculture?

Answer 30

Raising vegetarian fish like Tilapia.

Question 31

What is the best aquaculture system?

Answer 31

Grow Tilapia in a recirculation system.

Question 32

What is the main species for aquaculture in BC? Why?

Answer 32

Atlantic salmon.

Grows fast, productive species.

Question 33

What are the main concerns with aquaculture and Atlantic salmon?

Answer 33

If these fish escape, they can potentially outcompete native endangered, Pacific Salmon.
High density of net pens may cause outbreaks of sea lice to affect Pacific Salmon when coming close to net pens during spawning.

Question 34

What are some answers to the Atlantic Salmon aquaculture problem?

Answer 34

Grow Pacific salmon instead, less likely to get sea lice and less of a problem if they do escape.
Don’t grow as fast however.

Question 35

What is point source pollution?

Is this easy to regulate?

Answer 35

Pollution deriving from a single source.
ex: factories discharging directly to the system.
Easy to regulate.

Question 36

What is non point source pollution?

Is it easy to regulate?

Answer 36

Pollution from multiple different sources, can’t pinpoint exact location since it comes from everywhere.
ex: chemical lawn treatment, farms flow off, car emmisions
Hard to regulate

Question 37

Describe the Lake Erie dead zone.

Answer 37

Every couple of years during the summer, get a dead zone in Lake Erie.
Large problem due to phosphorus run-off.
Algae grows and then dies off in the summer due to heat and sink to the bottom.
During the summer, there is less mixing due to decreased wind and bacteria decompose the algae, consuming the oxygen at the same time.
Fish either die or run away from anoxic conditions.

Question 38

Describe bioaccumulation.

Answer 38

Accumulation/amplification of contaminants such as

PCBs as one goes up the food chain.

Question 39

How does El-Nino affect fish populations?

Answer 39

Surface temperatures are warmer than usual and upwelling events aren’t present at the same scale as they usually are leading to decline in fish populations.

Question 40

How does Global warming affect the state of the Worlds fisheries?

Answer 40

Warmer waters get even warmer and fish are forced to migrate to cooler waters.
This causes large migration events and possible death if fish populations cannot migrate.
See a disruption in local ecosystems as ice melts, water gets warmer, etc.

Question 41

Draw the MMSY graph, axes are percent of maximum (y) and exploitation rate (X)
show where MMSY, and show total catch, total biomass, mean Length max and collapsed species.

Answer 41

refer to notes