Transcript History waters spearfishing

Fisheries
Mo’ Fish
for Moe
Fisheries
“To hunt a species to extinction is not logical” – Mr. Spock
Fish populations are renewable resources
Overexploitation first occurred in shellfish
beds and in estuaries
Open-ocean fisheries were essentially
limitless until the development of powerdriven vessels and gear
Fisheries
International shortages and disputes over
fishing rights were solved the establishment of
the Exclusive Economic Zone (EEZ), a 200-mile
national fishing zone
Actually led to overfishing by U.S. domestic
fishing fleets
You Down With EEZ
Law Of the Sea – established 200-mile-wide Exclusive
Economic Zones (EEZ) – granting coastal nations
exclusive rights with respect to natural resources
Fisheries Science
Initiated in 1850”s by Norwegian government – hired
scientists to determine why catches of cod fluctuated
annually
Stock – basic management units in fisheries because birth,
growth, and death within the stock have greater effects on
dynamics than immigration of emigration
Size of a stock is mainly assessed by quality of landings
function of:
population size
spatial variability of fish
amount of fishing effort
Health of a stock is assayed by its production, which is
explained in terms of growth of previous year classes and
recruitment into the new year class
Why study fisheries
Despite collapse of individual fisheries and demise of highseas fleets, new resources have been exploited and total
landing have risen steadily since 1950
What does this trend
represent? A better
utilization of multiple
resources or the “beginning
of the end” in resource
utilization
Phases of fisheries use
Individuals can exploit fisheries at rates exceeding their
capacity for replenishment – undergo phases of use
Fishing Techniques
Purse seine
Bottom trawl
Gill net
Longline
Settlement vs. Recruitment
Settlement – larval transition from plankton to benthos
Recruitment – Fisheries term; the point at which fish
can be caught using standard gear
Settlement numbers – the end result
Final distribution depends on:
- dispersal
- predation and starvation (pre and post-settlement
- settlement at the adult site
- made some final movements toward
the adult habitat
- metamorphosed successfully
- survived to be detected by the observer
Settlement
Time to stop floating around
Factors influencing settlement
Light levels
Physical aspects of substrate
Chemical aspects of substrate (waterborne)
Conspecifics
Potential food
Potential competitors (avoid sites with damselfish)
Potential predators (if predator settles first->avoid)
Settlement
Time to stop floating around
Can reduced current flow
affect larval settlement?
Can seagrass density affect
larval settlement?
Slow Flow = Deposition
Fast Flow = Resuspension
Can Habitat Affect Settlement
High diversity
High diversity in reefs systems
Can habitat variety (complex 3-d systems) explain the
diversity level?
e.g., - Reefs = mix of coral, sand, caves, seagrass
High degree of vertical zonation
Many different available niches to occupy
Numerous habitats not enough to explain diversity
4 theories to explain reef fish diversity
& community structure
The models:
* 1. Lottery (chance)
* 2. Recruitment limitation
+ 3. Predation-Disturbance
+ 4. Competition
* Presettlement events
+ Post-settlement events
The Lottery
Supply of living sites on reef
Disturbing
factors
Removing
fishes
Change
nature of
site
A
B
C
A
C
A
B
B
A
Sites
gained
space opens
Pelagic batch
of larvae
A
B
C
C
Filled by random settlement
A
Recruitment Limitation Model
e.g., - Victor, Doherty, Doherty and Williams
Larval supply for total pop
to reach K
Nc
Changes in population
structure reflect “input”
Independent of post-settlement
processes (competition)
Result: community size unstable-> spp
composition unstable
S
Time
Recruitment Limitation
e.g., - Doherty & Williams
Evidence: Correlation between recruitment levels &
long-term changes in adult abundance
Juv
Adult
Not always
proportional
many times: no correlation!
Predation-Disturbance Model
e.g., - Talbot et al., Jones, Hixon
Predation (disturbance) after recruitment ->keeps
pops below the level at which resources are limiting
Naive recruits-> vulnerable
Higher mortality early in life
Type III curve
Nc
S
Time
Survivorship Curves
Type I
Type II
Type III
# of
survivors
Risk of
mortality
Type I – describes the
situation in which mortality
is concentrated toward the
end of the maximum life
span – e.g., - marine
mammals, turtles
Type II – describes a
constant mortality rate from
birth to maximum age e.g., - sharks, rays
Type III – indicates
extensive early mortality,
but a high rate of
subsequent survival. This
is typical of species that
produce many offspring
e.g., - teleost fishes
Determining post-settlement
predation
e.g., - Doherty & Sale
Determine effect of predatory exclusion on survival
survivorship
of reef fish
recruits
40% loss
(predation)
Predator removal: caging, spearfishing, poisons, trapping
Competition Model
e.g., - Smith & Tyler, Jones
Classic view: strong competitive interactions following recruitment
lead to high degree of specialization
Narrower ecological niches => so, more spp/area
(“reduced niche breadth”)
Support: competition inferred if (-) effect of density
on 1) survival, 2) growth, 3) fecundity/maturation
Evidence: Not conclusive
Summary: Community Models
Post-recruitment (PR) competition
Recruitment
modified by
PR processes
Recruitment
not modified by
PR processes
Intense
Weak
Competition
Model
Predation
Model
Lottery
Model
Recruitment
limitation
Model
Y
N
Space limited
Community Models
Processes structuring communities-> not
mutually exclusive
All 4 affect population structure
Need to consider pre- & post-recruitment processes
R
P,C
S
Nc
Lottery Model
e.g., - Sale, Kaufman & Ebersole
"I've never been so sure of anything in my life.
I am going to WIN this lottery."
– Homer Simpson
Stochastic or random recruitment events
Lottery for limited resource (space)
Priority access: first one there wins
No competitive advantages--Recruitment key!
Result: community size stable->
species composition unstable
Factor Controlling Recruitment
Recruitment – the number of individuals that reach a
specified stage in the life cycle (e.g., - metamorphosis,
settlement, joining the fishery)
Factors influencing recruitment
abundance and distribution of adult population
number and viability of eggs produced
survival of eggs and larvae
Factor Controlling Recruitment
Over 99% mortality occurs between egg fertilization
and settlement or recruitment of juveniles
Important period – small variations in mortality rates
have profound effects on subsequent abundance
e.g., - higher fecundity is associated with greater recruitment
variability
Variable supply of recruits determines:
population structure
strength of interactions in multispecies communities
biomass of fishes that can be caught
Fisheries based upon one or two year classes are highly
dependent upon successful recruitment
Poor recruitment when fishing effort is very high may
cause collapse
Mortality during early life history (ELH)
Development – behavioral and physiological performance
are key to survival and subsequent recruitment
Growth - leads to changes in size or abundance of existing
features
Ontogeny - leads to the appearance of new features and
reorganization or loss of existing ones
metamorphosis – transformation from one body form
(larval) to another (juvenile)
endogenous – exogenous feeding – transition from yolk sac
to external feeding
“point of no return” – point at which larvae become too
weak to feed and recover (starvation threshold)
- resistance to starvation increases as larvae grow
Starvation and its effects upon recruitment
Ocean stability hypothesis – aggregations of food, rather than
total integrated food, were more important to larval survival
e.g., - Hjort, Cushing, Lasker, Sinclair
Patches of high food concentration 
as ocean stability 
Larvae in patches could feed
effectively
When ocean is rough, prey would
become dispersed and density would
become too low to support larvae
Starvation and its effects upon recruitment
Match-mismatch hypothesis – interannual variation in larval
survival could be explained by the match or mismatch between
the timing of the production cycle and the peak of spawning
time
e.g., - Cushing, Mertz & Myers, Pope et al.
If there is mismatch in space or time between larval food
production and larval hatching time then the larvae may
not encounter sufficient food and reach the “point of no
return”
Starvation and its effects upon recruitment
Member-vagrant hypothesis – importance of the relationship
between spawning time and stable oceanographic features
which retain larvae in favorable environments
e.g., - Sinclair
Emphasizes the role of physical rather than biological
factors in governing spawning or year-class success
Reality: - physical and biological processes will interact
and both will be important
Starvation and its effects upon recruitment
Bigger is better hypothesis – since mortality rates decline
with size during ELH, it might be expected that getting big
quickly will minimize mortality events
e.g., - Houde
High growth rates have costs that can lead to increased
mortality, and actually growth rate evolved to balance the
costs and benefits
Reality: - Bigger may be better but is not necessarily
the best strategy to get big quickly
If it were, then natural selection would drive the genetic
capacity for growth to the maximum permitted by
physiological and phylogenetic constraints
Fisheries Models
To produce a good fisheries model, we must account for all
contributions to reproduction, growth, and mortality,
throughout the life cycle of the fishery resource species
Mortality
Reproduction
Growth
Recruitment
(Nursery Area)
Fisheries Models
Similarly, population biomass depends upon growth,
reproduction, natural mortality, but also includes the
implications of fishing mortality
Reproduction
Growth
Population Biomass
Models!
Fishing
mortality
Natural
mortality
Constructing Fisheries Models
Initial goal to to determine maximum sustainable yield
(MSY)
Surplus population models – used to search for the largest fishing
mortality rates that can be offset by increased population growth,
normally measured in changes in population biomass per unit time
Complex calculations based upon several life history parameters,
including:
population density
population biomass
population growth rate
* Equilibrium – point at which
processes balance one another
*
Oh, I forgot to er, carry the one
“I first observed this technology at the airport gift shop” – Professor John Frink
Logistic population growth
Bmax
Populations grow most quickly at intermediate
sizes up to a maximum total biomass Bmax
MSY in biomass occurs at a level of fishing
mortality that places the population at an
intermediate size
MSY
Bmax
Bmax
Applying Fisheries Models
Since MSY is a small target (an actual number) and is also
a moving target (due to temporal changes in productivity),
actual catch controls are first gauged by simulations of
high and low quotas.
If quota set too high:
yield would exceed the
surplus population so the
population would be driven
to extinction
If quota set too low:
if the population is larger than BMSY – will stabilize and yield lower
than BMSY
if population is smaller than BMSY – will become unstable and either
increase to equilibrium at the higher population size or crash
Evaluating Fisheries Models
The choice of production quotas is minor compared to the
procedure of fitting these models to real data to estimate
MSY and the level of fishing effort at which it occurs
Several to choose from:
e.g., - delay-difference, virtual population, statistical catch-at-age
Yield-per-recruit models – seek fishing mortality rates that achieve
the best tradeoff between the sizes of the individual caught, and the
number of individuals available for capture
A
The logic of yield-per-recruit models is
based upon the trade-off between growth
and mortality of individuals
A = optimal age at
which to catch fish
Fisheries Models in Action
If fishing mortality rates are set too high, too many
individuals will be taken before they have had a chance to
grow – growth overfishing
If fishing mortality is too low, although individuals will be
large when captured, the total yield will be low
Yield per recruit (Y/R) and
population biomass per recruit
(B/R) for a single cohort of fish,
for various potential fishing
mortalities, F
Y/R
Overfishing!
B/R
Fishing mortality - F
Fisheries Management
Fisheries are managed because the consequences of
uncontrolled fishing are undesirable
e.g., - fishery collapse, economic inefficiency, loss of employment,
habitat loss, decreases in abundance of rare species
Primary goal – maintain maximum biologically sustainable
yield (MSY or BSY)
Recently a mixture of biological, economic, social, and
political objectives
Multiplicity
Current thinking: - concept of MSY may not be useful in
fisheries management since overfishing has caused major
alterations in the trophic structure of marine food webs
Individual species do
not live in a vacuum –
they eat each other and
may compete for food
and space
Biological interactions
– mean that population
dynamics of different
species are inevitably
linked
Bycatches and Discards
"Do yourself a favor; don't turn around,“ – Keep America Beautiful
Native American
The aim of most fishers is to capture species that
have financial or energetic value – target species
Unfortunately, target species are often associated with other organisms
that may not be the intended catch of that fishery – non-target species,
which can become part of the catch known at incidental catch
Trawling effects
It has been estimated that across fisheries worldwide, up to
1/4 of any given catch is bycatch
Much higher in trawling operations; shrimp fisheries > 35% of global
fisheries discards
Kg discard per Kg
Fishery
landed
Trinidadian shrimp trawl
GOM shrimp trawl
NW Atlantic fish trawl
Atlantic Menhaden purse seine
NW Atlantic Hake trawl
14.70
10.30
5.30
0.30
0.01
Case Study: GOM shrimp fisheries discarded
19 million red snapper and 3 million Spanish
mackerel in 1989 (Alverson 1994)
What about the Wee Turtles?
“If I don’t save the wee turtles, who will? Ah! Save me from the wee
turtles. They were too quick for me. Ahh!” – Groundskeeper Wille
For more than a quarter century, there has been concern about
the impacts of shrimp trawling upon dwindling populations of
endangered sea turtles.
It is estimated that 150,000 sea turtles each year are killed in
shrimp nets.
Efforts by the United States to reduce sea turtle mortality by
the required use of turtle excluder devices - TEDs - has
resulted in a global environment-trade dispute now pending at
the World Trade Organization
What about the Wee Turtles?
A record 450 dead or disabled stranded sea turtles washed up on
Texas beaches in 1999, 95 of them endangered Kemp's ridleys
The Kemp's ridley, the most severely endangered sea turtle
species, now numbers fewer than 2,000 females, down from over
40,000 recorded in 1947
Shrimping activity has increased 400% in Texas bays and 95% in
adjacent gulf waters since 1961
What’s the solution?
“Well, that's why I asked. That's how you learn, by asking.. you dumbass.” - Carl Carlson
Limited to a change in fisheries resources (stop eating shrimp) or a
switch to another source of shrimp (aquaculture)
Is aquaculture the solution?
Disease outbreaks
Environmental issues
Habitat destruction
Shrimp!
Invasive species
Live weight (thousand tonnes)
World Production of Farmed Penaeid Shrimp
1000
800
600
400
200
83 84 85 86 87 88 89 90 91 92 93 94 95
Year
Purse Seining
Rate of incidentally caught dolphins in the
Pacific tuna purse seine fishery in the 60’s and
70’s sparked the tuna-dolphin debate and the
Marine Mammal Protection Act of 1972
However,  6 million dolphins killed since 1959
Three methods of purse seining for tuna in the
eastern tropical Pacific
On “Log”
On “School”
On “Dolphin ”
Who’s Seining Who
Although they are most detrimental to marine mammals, “Dolphin
sets” overwhelmingly produces the least amount of bycatch and the
greatest amount of large, adult tunas
Between the 1950’s
Bycatch taxa Log sets
School sets Dolphin sets and 1970’s, 100%
of purse seiners in
Dolphins
6
11
4,521
the Eastern
Tropical Pacific
Turtles
232
100
64
utilized Dolphin
sets
Billfishes
4,121
1,708
894
Sharks and
rays
105,632
30,258
7,760
Large pelagic
fishes
2,611,312
202,159
2,608
Triggerfishes
1,735,960
11,714
1,474
Other fishes
2,651,856
169,842
73,414
Since that time,
effort placed upon
moving the
fishery towards
Log and School
sets
1993-1996 total data
N= 10,000 sets per type
Hug This!
"Yarr, it begins. The dolphins are upon us and only this
old sea dog knows how to stop them -- Yarr!" - Captain McAllister
The Problem: Log sets are easy to conduct, but produce incredibly high
bycatch numbers (tens of millions) and generally yield young (5-15 lb) tuna
School sets are difficult to conduct; require spotting schools independent of
dolphin pods. Primarily utilizes juvenile tuna (10-25 lb) not yet associated
with dolphins
Dolphin sets – focus upon adult (>70 lb) fish with little associated bycatch
numbers
The Solution: Possible paradigm shift from the conservation of a single
species toward the protection of entire ecosystems/trophic communities???
or
More chicken contained in “Chicken of the Sea”
Fisheries Management – A Review
Fisheries are managed because the consequences of
uncontrolled fishing are undesirable
However, we are still loosing species every year – moving towards
smaller and “less desirable” species
What effect will this have on marine/estuarine food chains?
Over ½ of the world’s fisheries stocks are listed as either overfished or at capacity
Primary goal – maintain maximum biologically sustainable
yield (MSY or BSY)
Difficult in a global community looking for heart healthy food
products, cheap sources of protein, and the next delicacy
Recently a mixture of biological, economic, social, and
political objectives
Shift from biological and social to political and economic?
Marine Protected Areas (MPAs)
“Help! She’s touching my special area!” – Ralph Wiggum
A Marine Protected Area is a geographic conservation unit
designed to protect crucial communities and to provide
reproductive reserves for fishes that hopefully will disperse
into wider areas
MPAs are based upon the concept of Metapopulation – a
group of interconnected subpopulations, often of unequal size
Marine Protected Areas (MPAs)
Establishment can be justified by 2 points:
1. Protection of areas crucial to the maintenance and
even population expansion of fishery species
2. Protection of very diverse structural habitats, such
as coral reefs, or other communities that are deemed by
society to be of importance for economic, educational, or
aesthetic reasons
Source population – individuals from these populations move to other
local populations by means of larval spread and adult dispersal and are
aided by high reproduction
Sink population – receive individuals dispersing from others, but do
not provide dispersing individuals to other local populations
Marine Protected Areas (MPAs)
3 broad types of MPAs – also called No Take Zones (NTZ)
Fisheries Enhancement MPAs – focus on protecting local
populations as a management tool to augment or stabilize regional
fisheries yield
Ecosystem Diversity MPAs – focus on the preservation and
maintenance of broad-scale marine biological diversity
Special-Feature MPAs – focus on the preservation of a
particular locality because of its cultural importance or its value to a
particularly vulnerable life history stage
Taxonomy of MPAs
There are many different goals of MPAs, and as a
consequence, they are implemented in many different ways
Fall into 3 broad categories (fisheries, ecosystem diversity,
crucial geographic area), but also whether it is expected to
have a local effect (only within boundaries), or a wider
impact upon the ecosystem in which it is located (regional)
Reserve Type
Scale of desired effect
Ecological Diversity
Local
Regional
Fisheries Management
Local
Regional
Special Feature
Local
Regional
Design of MPAs
No-Take Area
Spawning
Area
Juvenile Feeding Area
Adult Feeding Area
Adult Feeding Area
Adult Feeding Area
Adult Feeding Area
Current and dispersal
direction
The spawning and
juvenile feeding areas
and one adult feeding
ground are no-take
zones, to allow a
minimum population
to complete a life
cycle
Y, MPAs
“Don't touch my stuff! Hey, this isn't the YMCA…” – Lionel Hutz
Attorney at Law
Philosophy of MPAs – an approach to conservation that
focuses preservation efforts on a relatively small proportion of
the geographic range of a species or community type
Rules – range from mild restrictions on fishing or ecosystem
damage to strict rules prohibiting fishing or taking of marine
specimens
Case studies – Looe Key National Marine Sanctuary, Bonaire
Marine Park, Great Barrier Reef, Hawaii
Men Without Hats!
“We have them in America. They're called bullfrogs” – Lisa Simpson
“What? That's an odd name. I'd have called them chazzwazzers” – Dash Dingo
Great Barrier Reef – largest
MPA in the world
Is zoned according to use:
1. Scientific Research
2. National Park (tourism)
3. General Use
- includes some regulated
recreational and commercial
fishing
Protecting Hawai‘i
Marine Life Conservation Districts (MLCDs) are
designed to conserve and replenish marine resources
Allow only limited fishing and
. other consumptive uses
Introduced to Hawaii in the fall of 1967 with Hanauma
Bay on Oahu
Resulting increase in fish populations was phenomenal,
and the bay has become world famous
Marine Life Conservation Districts (MLCDs)
Fishery Management Areas (FMAs)
Fishery Replenishment Areas
Wildlife Sanctuaries
Questions?
Comments?