17_Conservation_fisheries_GL_web

Fisheries and Conservation
1.  Threatened fishes
2.  Habitat loss and modification
3.  Species introduction
4.  Pollution
5.  Commercial exploitation and fisheries
Threatened Fishes
•  IUCN listed +1100 spp of imperiled fishes and
at least 93 extinctions
•  all extinctions from freshwater
•  e.g., harelip sucker
•  Specialist make up majority of extinct and
endangered fishes
•  e.g., the Devil’s hole pupfish
Threatened Fishes
Occupies 3 x 6 m
limestone cave
•  smallest habitat of
any vertebrate
The Devil’s Hole pupfish
Cyprinodon diabolis
Threatened Fishes
•  IUCN listed +1100 spp of imperiled fishes and
at least 93 extinctins
•  all extinctions from freshwater
•  Specialist make up majority of extinct and
endangered fishes
•  e.g., harelip sucker or the Devil’s hole
pupfish
•  Big river fishes with need for clear water have
been strongly affected
•  e.g., sturgeons, paddlefishes, suckers
•  Comparatively few marine fishes
•  broader distributions
Habitat loss
Habitat loss
Woody debris in streams and rivers provides habitat for
fishes and their food
•  Can contain 60% of the
total invertebrate mass
•  Produce four times more
prey than mud or sand
habitats
Many state agencies
emphasize removal for
“habitat improvement”
Habitat loss
Channelization involves straightening a riverine
system and smoothing its sides
Habitat loss
Channelization involves straightening a riverine
system and smoothing its sides
•  River is basically
transformed into a pipe
•  Great reduction in native
fishes
•  Floodplain habitat is
eliminated
•  10x reduction in fish biomass
in lower Mississippi
Habitat loss
Dams
•  fishes adapted to flowing water fare poorly in
impounded water
Habitat loss
Dams
•  fishes adapted to flowing water fare poorly in
impounded water
•  stream assemblages replaced by sunfishes and
catfishes
•  Impede movement of spawning fishes upstream of
damn
•  Modify ecosystems more than most other human
perturbations
•  Colorado river is f****d, only about 1% of its
virgin flow reaches Sea of Cortez
Habitat loss
Giant Totoaba, Totoaba macdonaldi
Habitat loss
Giant Totoaba, Totoaba macdonaldi
Habitat loss
Watershed perturbation: altering the surrounding landscape
or groundwater which through water must flow
•  Logging, bulldozing for construction, groundwater and
surface water withdrawal, overgrazing of streamside
vegetation
Deforestation…
Habitat loss
Watershed perturbation: altering the surrounding landscape
or groundwater which through water must flow
•  Logging, bulldozing for construction, groundwater and
surface water withdrawal, overgrazing of streamside
vegetation
Deforestation…
•  increased temp due to loss of shade, increased variation
in flow rates due to loss of uptake by plants, intensified
erosion leading to turbidity, siltation, and stream bank
collapse, and loss of nutrient input from falling leaves
and fruits
•  cessation of input of woody debris
Habitat loss
Coral loss: bleaching, direct mining, inadvertently by
harmful fishing techniques (poisons, bottom trawling,
explosives), boat anchoring and diver activities,
sedimentation and pollution, and changes in coral
predator abundance as result of fishing practices
Species Introductions
Introduced predators
•  Nile Perch to Lake
Victoria
•  elimination of
herbivorous cichlids
•  algal blooms
•  70% or 200 spp are
threatened or extinct
•  Nile perch has high oil
content, drying
ineffective
•  Must be smoked
•  deforestation
Species Introductions
Centrarchidae
•  31 species native to North
America
•  native east of the Rockies
except for the Sacramento
Perch
•  reduced range in CA
•  least abundant where
non-native sunfishes
have been introduced
•  Bass and sunfish have been
introduced all over the
world…now illegal
Pollution
Acidic rain has led to declines in acid
sensitive fishes of North America and
Europe
•  e.g., Atlantic Salmon, brook trout,
and minnows in eastern US
Pollution
Agricultural chemicals directly and
indirectly cause harm to many fishes
•  Directly ingested with food
•  Indirectly lead to eutrophication
Pollution
Agricultural chemicals directly and
indirectly cause harm to many fishes
•  Directly ingested with food
•  Indirectly lead to eutrophication
•  changes balance of algal species
to inedible blue greens
•  can raise temps and lower
oxygen zones
•  e.g., Gulf of Mexico &
Clear Lake
Pollution
Pollution
Agricultural chemicals directly and
indirectly cause harm to many fishes
•  Directly ingested with food
•  Indirectly lead to eutrophication
•  changes balance of algal species
to inedible blue greens
•  can raise temps and lower
oxygen zones
•  e.g., Gulf of Mexico &
Clear Lake
Clear Lake Splittail
Fisheries
Shift Towards Aquaculture
Shift Towards Aquaculture
Today ~ 50% of seafood derived from aquaculture
Shift Towards Aquaculture
Human growth rate is about 1.13% in 2016
•  220,000 people added everyday
•  or LA county in 45 days
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Importance of Global Fisheries...
•  Marine sources provide about 20% of the animal protein eaten
by humans.
•  Another 5% is provided indirectly via livestock fed with fish.
•  60% of fish consumption is by the developing world.
•  In Asia, about 1 billion people rely on fish as their primary
source of protein.
•  The fishing enterprise employs some 200 million people
worldwide
Fishing methods….
• Hook and Line
• Long line
• Jigging
• Trolling
• Traps
• Gill net
• set
• drift
• Seine
• Beach
• Purse
• Trawl
• Bottom
• Midwater
Hook and Line
Trolling
Hook and Line
Longline
Drift
Set
Fishing methods….
• Hook and Line
• Long line
• Jigging
• Trolling
• Traps
• Gill net
• set
• drift
• Seine
• Beach
• Purse
• Trawl
• Bottom
• Midwater
Drift
Set
Fishing methods….
• Hook and Line
• Long line
• Jigging
• Trolling
• Traps
• Gill net
• set
• drift
• Seine
• Beach
• Purse
• Trawl
• Bottom
• Midwater
Purse
Purse Seine
Roundhaul Netting
Seining
Beach Seine
Fishing methods….
• Hook and Line
• Long line
• Jigging
• Trolling
• Traps
• Gill net
• set
• drift
• Seine
• Beach
• Purse
• Trawl
• Bottom
• Midwater
Bottom Trawling
Trawl
Bottom Trawl
Bottom Trawl
Bottom Trawl
Satellite picture - China trawlers
Trawl
Midwater Trawl
Fishing down the food web
90% decline in
biomass of large
predators in last
40 years
Bluefin Tuna…
~3% prefishing
In 2013, a single Bluefin tuna weighing 222 kg sold for
1.76 million dollars or $3,603 per lb
Objective of Fisheries Harvest
Obtain food for people to eat
Objective of Fisheries Management
Maximize amount of harvest
Objective of Sustainable Fisheries Management
Maximize amount of harvest that can be
sustained indefinitely
Fisheries Management
• 
• 
• 
• 
How can ecological knowledge contribute?
Most fisheries models simple
Why do stocks collapse?
Objective:
– understand basic models within framework of
population biology
– understand how they go wrong
Bottom line questions...
•  Is there an optimal population size from
which to harvest?
– Requires information on population
growth and factors that affect it
•  What age of fish should we harvest?
– Requires information on fish life history
Fecundity
•  Number of eggs produced by a female (per spawning season)
•  Variability- fecundity varies with body size and species:
•  Atlantic cod: 200,000 (small females) to 12 million eggs
(large females)
•  Smallmouth bass: 2,000 eggs (small females) to 20,000
eggs (large females)
•  Ocean sunfish up to 300 million eggs per year
Fish Egg Production
300000000
Number of Eggs
250000000
200000000
150000000
100000000
50000000
0
0
100
200
300
Body Mass
400
500
600
Body Growth
•  Fish grow their whole lives (indeterminate growth) - rates
highly variable
•  Rates change with life stage
•  Grow most rapidly early in life (exponential growth)
•  Growth slows at sexual maturity (gonadal vs. somatic
growth)
•  Exponential growth curve "breaks" to form a sigmoid curve
• Growth plateaus when older (larger maintenance cost,
more into reproduction)
Annual Production
Population size
low –
production
limited by
growth rate
of population
Low
Population size
high –
production
limited by
carrying
capacity
High
Population Size
Stock Size
Fisheries
biologists
call
populations
“STOCKS”
Notice: This
level is K/2!
Time
Annual Production
Limited by
small
population
size
Low
Limited by
carrying
capacity
Stock Size
High
What does fishing do to “Stock Size”?
•  REDUCES IT!
•  The more fishing effort, the more fish you catch,
and the smaller the stock size…
•  Can we combine this with our population model to
come up with something useful for fish
management?
What is the best fishing effort to put out to maximize catch?
Maximum Sustainable Yield !
Total Catch
Fish stock
high – limited
by carrying
capacity
Fishing Effort
Maximizes
amount of
fish caught
per unit of
fishing
effort
Fish stock low
– limited by
growth rate
of population
Catch vs. Fishing Effort
•  Used as basis to define fishery
status
•  Below MSY = underfished
•  Above MSY = overfished
Total Catch
Fishing Effort
Economics of overfishing…
Maximum Economic Yield
Maximum Sustainable Yield
Open Access Yield
The MSY Model as a scientific concept - assumptions:
• The environment is constant
• no fluctuations in the resources available to the
populations - El Nino’s, etc...
• All population regulation is density-dependent
• All mortality is due to harvesting
• Population reaches stable equilibrium
• fish populations intrinsically variable
• recruitment controlled by external factors
• No species interactions
• fishery changes predation, competition dynamics
which affect population
• Replenishment independent of fishing effort
New Management Approaches
•  Maintain recruitment
–  Cut fishing effort
•  Gear restriction
•  Quotas
•  Temporal restrictions
–  Fisher ownership
•  Ecosystem management
–  Spatial management - Marine Reserves
•  Essential Fish Habitats
•  Habitats of Particular Concern
•  Fully Protected Marine Reserves
Marine Reserves