Fisheries

Question 1

What are all gears and techniques

Answer 1

• All gears and techniques are either active or passive
• Active gears are either trawls or dredges
• Passive gears are much more diverse, and can be nets, pots, traps, or lines
• All about maximising catch per unit effort. (CPUE)

Question 2

Dredges

Answer 2

Mechanical dredges (top 10 cm)

Hydraulic - whips up clams and mussels. More expensive and difficult to use but does much less damage to the seabed.

Question 3

Trawls

Answer 3

• Otter trawls can be much larger, can be towed between 2 or 3 boats.
• Benthic trawls often contain tickler chains to create hydrodynamic disturbance (noise). Cause fish to rise up and shoal in front of the net, they swim in ahead as if chased by a predator, until they become tired and drop back into the net.

Question 4

Method good for picking up large shoaling pelagic species like tuna,

Answer 4

• Purse seining, good for picking up large shoaling pelagic species like tuna, nearly always done from boats.

Question 5

Static - drift nets

Answer 5

• Really selective with what you catch. Big things aren’t caught in smaller mesh sizes.
• Set across a current, and fish’s operculum gets caught.
• Trammel net’s don’t cause as much damage to the fish. They come in through the wide net, panic and turn around becoming pocketed within the net.

Question 6

Pots

Answer 6

Common and popular in the North East. Parkour pots have a separate chamber to put the bait in, meaning there is no limit to the amount of individuals you can catch.

Can be selective about catch by varying baits or putting crushed up scents of the species you don’t want to catch (Carcinus maenas.

Question 7

Traps

Answer 7

Can range from really simple things, or be bigger and more complicated.

Set up on a tide or river current and can be baited.

Question 8

Lines

Answer 8

Range from one person and a line to industrial operations with 50 km of line, and all automatic.

Lines can be very specific with different bates and lures.

Question 9

Squid

Answer 9

Squid harvesting, green lights attract fish.

Question 10

Squid

Answer 10

Squid harvesting, green lights attract fish.

Question 11

Individual methods

Answer 11

Spears and harpoons can be more destructive than you might expect through trampling and direct damage to the coral.

Poisons are easier to get away with, bleach is easier to explain.

Any kind of fishing is the most dangerous thing humans do on a regular bases. Infection, loss of limbs and parasites.

Many other techniques, such as cormorant fishing - collar around neck.

Question 12

Fisheries play a key role in providing food and income

Answer 12

• 35-50 million fishers in 4.6 million vessels
• Land 93.5 million tonnes of fish (that we know of)
• Not all gets eaten
• Caught fish are worth $65 billion per year
• Contribute $230 billion to the global economy - although there are about £35 billion a year in subsidies.
• Invaluable ‘labour buffer’ for LEDC’s - don’t have to be a full time fisherman.
• 22 million fishers (44-63%) are ‘small scale’
• 78% of fisheries workers are from LEDC’s
• 8% of planet’s population supported by fisheries
• However, they are rife with environmental, logistical, political, and economic problems
• Fish dominate catches (~90%)
• 50% of all catches are 20 species 22,000 species of fish in the ocean.

Question 13

A global Overview of Fisheries

Answer 13

• 144/196 nations have fisheries
• 86% of fishers (and fish farmers) are in Asia.
• LEDC’s produce 50% by value, 60% by weight. 67% exported to MEDC’s
• Biggest chunk to trash fish, which 90% of is used to make fish oil/meal
• Landings dominated by low-value species for fishmeal and oils for food and agriculture
• Lesser-fished species can still have high value (e.g. $ea cucumbers)
• Overall landings (maybe) stable since ~1990
• But individual landings fluctuate widely between years (both because of abundance and fisher behaviour)
• Fish stocks probably declining
• ‘Stability’ possible through increased effort and technology

Question 14

History of Fishes

Undertaken since prehistoric times

Answer 14

Fish hooks found dating back to 8000BC

Referred to in some of the earliest writings

Determined the spread of empires

Question 15

History of Fishes

Answer 15

• Sail power
• Smoking and salting
• Powered engines
• Canning (1840)
• Refrigeration
• Powered-winches
• Post WW2 technology
  
  • Sonar
  • Echo-sounders - good enough to distinguish between species.
  • GPS
  • Automation

Question 16

History of Fishes

Changes over time

Answer 16

• First industrial fisheries targeted shoaling fish for fishmeal, early 1800’s.
• Originally believed that abundance was essentially infinite
• Scotland was the first country to protect inshore waters (purely political), 15 Century, other countries followed
• Post WW2 agreements eventually lead to development of United Nations Convention on the Law of the Sea
• 200 Nautical mile Exclusive Economic Zones established (90 % of fishing is coastal)
• Not to be confused with 12 mile territorial waters.
• Rapid expansion of fisheries since 1950’s
• 10% of all primary production on 2/3’s of continental shelves is taken out through just fisheries
• Between 1961-1995 production increased from 34MT to 83MT – 4x more area fished
• 10x more energy used now than during the 1950’s, CPUE has halved
• Long history of disputes between otherwise friendly nations – The Cod Wars

Question 17

What is fisheries managment?

Answer 17

• Whole point of fisheries management is maximum sustainable yield.
• Fisheries science’ emerged in the 1950’s, developing these single species models, a lot of which are crap but still form the base of management strategies we see even today.
• Fisheries proceed through distinct phases (number and names differ between texts), irrespective of species

Question 18

Where does fisheries management tend to operate?

Answer 18

• Management tends to operate at the ‘stock’ level
• Reduced competition increases fish abundance, management aims to keep stocks at this point
• Stocks are assumed to be independent
• Fundamentally floored, due to many other factors needing to be considered
• Quotas based on amount of fish caught, when the amount of fish caught doesn’t equate to the total amount of fish
• Subsidies keep fishing from reducing to the growth phase.

Question 19

Fishery management today.

Answer 19

MSY formed the basis of management for decades.

Now much more complicated

• Environment
• Economy
• Social/cultural factors
• Politics

Note that these are often difficult or impossible to quantify, and none are independent

Major problem – catches do not reflect abundance (more later….)

Subsidies can keep fisheries in the ‘collapse phase’

Question 20

Subsidies

Answer 20

• No single agreement on definition
• Many fisheries subsidised, totalling ~ $35 billion globally
• Take many forms, fuel (22%), management (20%), ports (10%)
• Common in Asia (Japan & China ~ 20% each) and Europe (25%)
  
  • One of two types (although there is overlap)Capacity enhancing
    
    • e.g. In1989 the USSR landed $5 billion worth of fish, but operating costs were $10-13 billion
  • Beneficial subsidies
    
    • e.g. management and conservation programs, development of cleaner gear etc.
    • Only the US has higher beneficial than capacity-enhancing subsidy values

Question 21

Where do subsides often fail and why?

Answer 21

Very often fails in the tropics

• LEDC countries produce fish for export, although this is often unregulated.
• Multispecies fisheries - hard to regulate how much of each fish to catch
• Limited knowledge of target species, ecosystems as a whole, and actual fishing effort
• Strong cultural significance - hard to prevent fishing at certain times for example.
• Problems with reporting and enforcement
• (Not unique to LEDC’s)
• Latest recommendations are simply to use ‘biomass’ to set limits in tropics
• Fish biomass closely related to health of reefs
• Whatever the strategy, management relies on understanding abundance, recruitment, and production

Question 22

Catches and abundance - what is fisher behaviour impacted by?

Answer 22

Fisher behaviour impacted by

• Market demand
• New Regulations
• Politics
• War
• Changes in costs
• Weather
• Taxonomy

Question 23

Ecosystem based management

Answer 23

• Ecosystem based management’ has been the adopted policy in most MEDC’s since the 1990’s
• Supposed to replace the ‘single species equilibrium’ paradigm
• Include non-target species, ecosystems as a whole, habitats
• ~2% fisheries actually use ecosystem drivers in management
• Many reasons for lack of uptake – logistical, scientific, political, economic.
• Considering other factors such as oil rigs qualifies as ‘EBM’

Question 24

Why are stats important in fisheries managemnt?

Answer 24

• Even when catch-abundance relationships are strong, using the wrong statistics can have serious consequences
• Fish start to cluster when their abundances drop for breeding, meaning some fisheries were catching far more fish. This caused a skewed mean - pulling the numbers way up. (median or geometric mean show were the stocks began to go wrong)

Question 25

Ecological problems

Varied and variable in space and time – between species, between stocks (esp. widely-dispersed), and between fisheries

Some of the largest issues include

Answer 25

• Removal of target species (obviously!)
• eImpacts on non-target species (e.g. bycatch)
• Damage to habitats
• Shifts in population structure/life-histories

Question 26

Varied and variable in space and time – between species, between stocks (esp. widely-dispersed), and between fisheries can lead to

Answer 26

• Unexpected declines
• Range shifts (movement, expansion, contraction)
• Prey-switching (a nightmare for management)
• Even whole ecosystem shifts

Question 27

By-catch defined as

Answer 27

‘incidental catch’ + discards

• Highly variable between fisheries
• The more specific and the more regulated, the more ‘by-catch’
• Even valuable catch can be discarded to make room for more valuable species (“Highgrading”)
• Or when quota is reached for a given species but not others

Question 28

By catch - what has been changed?

Answer 28

Although many species are caught as ‘incidental catch’, birds, mammals, and turtles receive the most attention (i.e. all the attention)

• Drift/Gill-netting is now illegal on the high seas because of bird and dolphin bycatch
• Birds can take 70% of long-line baits
• Trawl Efficiency Devices developed to protect turtles
• Threats of trade embargoes forced East Asian fisheries to adopt
• ‘Backing-down’ now standard practice in tuna purse-seining
• Pingers and other ‘Scarers’ developed to discourage dolphins

Question 29

Damage to habitats

Answer 29

Active Gears

• Benthic trawling/dredging
  
  • Areas of intense fishing can be 20% trawl-marks by area, but extremely variable in space
  • Longevity of tracks and severity of impacts are variable with habitat, method, and species present
    
    • e.g. marks last hours in gravel, months in mud
    • e.g. A bivalve can be killed, a starfish will lose a regeneratable arm
    • e.g. biodiversity of stable mud fauna impacted for >18 months, mobile sand infauna not impacted at all. Coldwater reefs impacted for years
• Impacts can be subtle
  
  • Long-term declines in North Sea whelks due to fishing (probably) led to declines in hermit crabs, increases in brittle stars, and subsequent shifts in plankton

Question 30

Damage to habitats static gears

Answer 30

Generally not as damaging as active gears

• Some damage during deployment/retrieval
• But more easily lost – ‘Ghost-fishing’
  
  • Fish and crustaceans often caught
  • Decomposing corpses attracts scavengers
  • Can persist for well >1 year

Coral reefs are particularly susceptible

• Blast fishing may be the damaging ‘alternative’ practice at the local scale, but plenty of other practices damage reefs

Question 31

Shifts in population structure/life-histories

Can be due to phenotypic plasticity, or genetics

Answer 31

Shifts in population structure/life-histories

Can be due to phenotypic plasticity, or genetics

• Fishing is selective, even in non-selective fisheries
  
  • Pots tend to catch the brave
  • Nets tend to catch the shy
• Size-selection can shift sex ratios
  
  • In protandric spp., females are larger
  • In protogynous spp., males are larger
• Growth rate and age at maturity are both impacted by size-selective fishing
  
  • Fish usually mature at 65-80% of their maximum size
• Fish alter behaviour as they grow and mature, so impacts on these factors change their entire ecology
• Fisheries Induced Evolution
  
  • Difficult to actually evidence, but probably inevitable
  • Reduces genetic diversity
  • Leads to cascades throughout the ecosystem

Question 32

Marine Protected Areas

Answer 32

• Popular management strategy, especially when understanding is low
• Quantifiable management ‘effort’, looks good on paper!
• So variable that each MPA is probably unique
• Whether they actually work is very debateable
• Five key factors which determine success
  
  • Size
  • Age
  • Degree of fishing permitted
  • Enforcement
  • Presence of continuous habitat
• On average, large fish see a 35% increase in biomass (variable), few other generalizable benefits
  
  • Probably down to compliance
• Has been suggested that gear restrictions work better than space restrictions, especially where enforcement is limited
  
  • Benthic fish abundance is up 500% off the East of the US since 1990’s – tighter controls, not closures

Question 33

What is the future of fishing?

Answer 33

• Coastal zones are already heavily fished
• Fisheries are moving deeper, and farther north
  
  • Many polar fisheries seem highly productive, but this may be a result of fish moving because of climate-change
  • Polar species are often not suitable for fishing due to slow growth and maturity rates.
  • Most polar and deep sea species are listed as ‘least concern’ by the IUCN - although many might simply be data deficient
  • Polar and deep sea species tend to have long life-histories, and lack genetic diversity and phenotypic plasticity
  • Serious lack of data on these species and ecosystems
• Climate change models predict a 14% increase in primary production by 2050
  
  • Increases in fish at high latitudes (+ 30-70%), decreases in low latitudes (- 40%), + 1-3.4% overall
    
    • Key fisheries are set to decline (e.g. Peruvian anchovy)
• Climate change models predict a 14% increase in primary production by 2050
• Increases in fish at high latitudes (+ 30-70%), decreases in low latitudes (- 40%), + 1-3.4% overall
  
  • Key fisheries are set to decline (e.g. Peruvian anchovy)
• Note the importance to the country does not reflect the importance to the planet

Question 34

WIDER READING: Fisheries management for human and food security- Conflicts

Answer 34

• McClanahan et al., 2015- Fisheries management for human and food security- Conflicts

The study:

• Evaluate the extent of nations’ dependency on fisheries and aquaculture in a food security context and threats to supplies

Results:

• Wars/ Conflicts can cause food security- Unsafe to fish so fish in other areas to supply the food which causes a collapse e.g. Monterey bay 1940s sardine to provide for American troops. N Atlantic was left and had large catches after the war.
• Fisheries lead to military confrontations- Cod Wars- 1950s-1970s between Iceland and UK.
• Iceland extended its waters caused conflict with UK which had been fishing these waters since 15th century- threatening livelihoods of UK fishing ports
• Conflicts over failing states unable to govern their EEZs and where states are unwilling or unable to defend the interests of their own fishing fleets. E.g. Piracy off the Horn of Africa
• All create job insecurity (260 million people employed globally in fisheries + Aquaculture).
• If not resolved, current trends towards declining net resources, increased costs and sensitivity by high resource dependence, inescapable poverty traps through lack of resources and alternatives, a North–South divide in investment and production, and increasing competition for access predict more conflicts between poor and wealthy nations over equitable trade and potentially less food security in the future.
• Fish may become a luxury, inaccessible to those who rely on common property.

Question 35

WIDER READING: Does catch data reflect abundance?

Answer 35

Pauly et al., 2013- Does catch data reflect abundance?

The study:

• Can catch data be trusted to represent abundance?

Results:

• Yes- Crucial signal- without catch data, there would be no signal of downward trends would even exist without FAO (Food and Agriculture organisation) catch data- predict future declines
• No- Misleading
  
  • Many other factors as well as abundance determine fisherman hauls
  • Factors include: Shrink in markets, new fishing regulations and changes in taxonomy
    
    • E.g. 1950s global shark catches assigned to 7 taxonomic groups, early 2000s 36 groups- catches may not have decreased only being registered under different names

Question 36

WIDER READING: Management, MPAs, conservation of fisheries

Answer 36

Edgar et al., 2014 – Management, MPAs, conservation of fisheries

The study:

• How MPA’s conservation benefits increase with 5 key factors: No take, Well enforced, Old (>10 years), Large (>100km2), isolated by deep water or sand

Results:

• Need at least 4/5 factors to work effectively
• Effective MPAs compared to fished areas
• x2 large (>250mm total length) fish species per transect
• x5 more large fish biomass
• x14 more shark biomass

Question 37

WIDER READING: future of fishing

Answer 37

Barange et at., 2014 – The future of fishing- What could happen

The study:

• Climate shelf-seas model to 67 marine national exclusive economic zones (EEZs). 60% of global fish catches

Results:

• Mixed layer depth temperature (MLDT) expected to increase
• Largest predicted increase in the Nordic Sea (+29.3%),
• The largest average decreases are expected in the Canary Current (−14.6%)
• Impacts will be of greatest concern to the nations of South and Southeast Asia, Southwest Africa
• Increases and decreases in fish production potential by 2050 are estimated to be <±10% from present yields.

Question 38

danish seine

Answer 38

Rare but interesting way of fishing. The rope acts as tickler chains and corals the fish together, works well for large non shoaling demersal species such as big sturgeon. The big advantage is that fish don’t spend long in the net and don’t get too damaged. This is very difficult to do, ropes can get caught and you don’t catch huge amounts.