Transcript Chapter 11

Fisheries (and Wildlife)
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Fisheries and Wildlife are a “Renewable” Resource
Forests are also renewable
Extinction (depletion) is possible if use too much of
the resource, but can enjoy continued use if use
some
Depletable Resources are those which cannot be
renewed, oil, coal, copper, diamonds, etc.
Focus on fish in this discussion --- most discussion
would also apply to other wildlife
Modern fishing technology, coupled with increased
demand and open-access exploitation of fisheries,
has driven many fish stocks to low levels; some are
threatened with extinction.
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FAO State of the World Fisheries, 2006
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FAO State of the World Fisheries, 2006
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FAO State of the World Fisheries, 2006
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Collapse: End of Global Fish Stock by
2050? (source: Globalization 101.org, the Levin Institute)
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According Food and Agriculture Organization
(FAO), over 70 percent of fish species are
currently in danger of collapse. Monitoring
600 groups of fish species, the FAO deems
52 percent to be fully exploited, 17 percent
overexploited, 7 percent depleted, and 1
percent recovering.
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Collapse: End of Global Fish Stock by
2050? (source: Globalization 101.org, the Levin Institute)
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Study published in Science using historical analysis projects the
collapse of all fish stocks worldwide by 2048.
The four-year study was conducted by ecologists and
economists at the National Center of Ecological Analysis and
Synthesis, UCSB.
Scientists examined fish catch reports from 1950-2003 for 64
ocean-wide regions that represented 83 percent of fish species in
the world. The biodiversity of 48 marine reserves and areas near
fishing grounds were then examined.
The results show that the “collapse”, a decline of over 90 percent
of stock, of one fish species can threaten an entire marine
system. The reduction of biodiversity impairs an ecosystem’s
ability to recover from environmental stresses and promotes
instability.
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Projections of
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US NOAA – Fish Stock Sustainability
Index
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Overfishing – Harvest rate is above a prescribed fishing mortality
threshold.
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Overfished - Stock size is below a prescribed biomass threshold.
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Approaching Overfished Condition - Based on trends in
harvesting effort, fishery resource size, and other appropriate
factors, it is estimated that the fishery will become overfished
within 2 years.
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MSY - Maximum Sustainable Yield - The largest long-term
average catch or yield that can be taken from a stock or stock
complex under prevailing ecological and environmental
conditions.
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US Recreational Fishing
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Recreational fishing is also very important in
the United States.
According to the U.S. Fish and Wildlife
Service, approximately 34 million adult
Americans (over age 16) participated in
recreational fishing in 2001.
These anglers accounted for 500,000 days of
fishing and $35 billion on fishing-related
expenses.
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Fisheries Biology
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The reproductive potential of a fish population is a
function of both the size of the fish population and
the characteristics of its habitat.
Both the growth of the population and the population
itself are measured in biomass (weight) units.
Biomass does not distinguish between number of
individuals and mass of individuals.
Figure 11.1 depicts a logistic growth function which
illustrates the relationship between the fish
population and the growth rate of the population.
Initially, there is no growth, then over some range of
population (up to X2), population growth is
increasing. Beyond X2, the growth of the population
is decreasing.
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Fisheries Biology
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The ecosystem's ability to support the fish
population is the most significant reason for the
changing relationship between population growth
and population.
With a low population, the resources will support
increasing growth.
As the population grows, there is a growing
competition for those resources and the growth in
the population slows.
Eventually, the amount of growth falls to zero, which
occurs at the maximum population K.
This point is also referred to as the carrying capacity
of the environment and is a biological equilibrium.
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Fisheries Biology
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The growth function represented in Figure 11.1
represents a a compensated growth function.
Figure 11.2 contains a depensated growth function,
where the growth rate initially increases and then
decreases.
Figure 11.3 contains a critically depensated growth
function where, X0 represents the minimum viable
population.
If population falls below this level, growth becomes
negative and population becomes irreversibly
headed towards zero.
The implication is that if managers make a mistake
and allow too much harvest, they may doom the
population to extinction.
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The Optimal Harvest
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In order to determine how harvesting affects a fish
population, consider the growth function in Figure
11.4.
Note that C1 represents the level of harvest (harvest
and growth are measured on the vertical axis).
When a harvest of C1 units per year is removed from
the fishery, the fish population declines because
harvesting is removing a portion of the population.
Population will continue to fall until natural growth is
equal to the harvest, which occurs at X1.
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The Optimal Harvest
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In Figure 11.5 a harvest level of C1 is associated
with two equilibrium populations (X1' and X1").
This means that growth is exactly equal to harvest
and the population will remain unchanged at either
of these levels.
Cmsy represents the harvest level associated with
maximum sustainable yield for the fishery.
This is the only harvest level associated with one
equilibrium point.
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The Optimal Harvest
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In the early discussions of fishery
management, maximum sustainable yield
was the theoretical goal of management
policies.
Recent policy targets a more precautionary
goal of a population between the carrying
capacity and the level associated with
maximum sustainable yield.
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The Gordon Model and Its Evolution
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In a 1955 article, H. Scott Gordon made the point that
uncontrolled access to fishery resources would result in a greater
than optimal level of fishing effort.
Gordon derived a catch function that represented a "bionomic"
equilibrium.
This catch function considered the relationship between fishing
effort, catch, and fish population.
Gordon’s analysis began by assuming that, holding everything
else constant, catch is proportional to the fish population.
Figure 11.6 illustrates a set of yield functions, where each curve
represents a different level of fishing effort.
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The Gordon Model and Its Evolution
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By superimposing the equilibrium catch function on
the yield functions (Figure 11.7) it is possible to
identify the effort and yield function associated with
maximum sustainable yield in the fishery.
This is known as the sustainable yield function
(Figure 11.8).
Notice the sustainable yield function examines the
relationship between effort and catch.
As effort increases, sustainable yield increases and
then decreases.
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The Gordon Model and Its Evolution
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A sustainable total revenue function can be derived
from a sustainable yield function.
Price is assumed to be constant, based on the
additional assumption that catch from that particular
population will be small relative to the total market.
Given a constant price, a sustainable total revenue
function can be derived simply by rescaling Figure
11.8.
In Figure 11.9, the sustainable total revenue function
is labeled TR and an additional curve representing
total costs (TC) is also given.
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Efficient use of the fishery
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Economic goal is to maximize net benefits
(also called economic rent)
This occurs where NB = TR-TC is the
greatest (also where MR=MC).
Economic rent originates from the
productivity of the fish stock, where more fish
implies greater catch with less effort (cost).
Where is economically efficient level of effort
and harvest?
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Efficient use of the fishery
$
benefits,
costs
TC =cE
E*
EMSY
Effort
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Economic Efficiency
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Assumptions in diagram
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Price of fishing is fixed and constant
Cost of effort (c) is fixed and constant
Catch/unit effort increases with larger population
Optimal effort, that effort which maximizes economic
rent, occurs at E*
How does efficiency compare to MSY? Smaller
harvest and larger fish population
Why? Because higher fish population means lower
cost/unit effort, when consider both costs and
benefits, efficient to use less than MSY
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Economic Efficiency
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Extra benefit of fishing not worth extra effort past E*
so more conservation than MSY
This is economically efficient level, will private
market achieve this result?
Suppose there is a single owner of the fishery (not a
monopoly, i.e., competes with other fisheries for
price of fish, but only 1 decision maker concerning
how much to fish this location)
What E will a single owner choose to maximize
profits?
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Single Owner solution
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Profits = total revenue – total costs = pE – cE,
same as net benefits
Can also see this in MR and MC curves
(MC=c, shape of MR comes from TR curve)
Table 11.2 illustrates the relationship between
total catch, marginal catch, and average
catch.
Profits are maximized when MR = MC
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Economic Efficiency, Open Access
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Single owner would choose economically
efficient level, will open access?
Open access = everyone can access the
fishery,
Common property = everyone within a subset
of the population can access the fishery (open
access, but only to a subset of the population)
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Solution under Open Access
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In an open-access fishery, when economic rent is
earned in the fishery, entrance by new firms occurs
until economic rent falls to zero, effort level of E1 in
Figure 11.9.
The entrance of firms in response to economic rent
and the resulting increase in effort to E1 results in
AR = MC rather than the optimal effort level of E2
where MR=MC.
Open access results in over exploitation of the
resource
Total profits from fishery are reduced compared to
single owner, more effort than necessary is being
expended to get a given harvest
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Overexploitation and Open Access
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Each individual fisher compares their average catch
and associated revenue with the value of the highest
alternative to fishing.
If the highest alternative available is $50 per day, then
the fisher will compare average catch (AP) multiplied
by Price against the alternative of $50.
The result is that there are a greater number of fishers
in the fishery than would be if the decision to enter
was based on a comparison of marginal product*
Price, rather than average product* Price.
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How to get efficient solution?
Privatize Fishery --- often hard to do, not popular
with many
Impost tax on effort --- would work, but not done
much
Raise real cost of fishing ---- common, but not
efficient, end up using more resources to catch
same number of fish
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Gear restrictions
Shorten season
Close certain fisheries,
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Current Fishery Policy
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Example of gear restriction, in Maryland's share of the Chesapeake,
it is illegal to dredge for oysters under motorized power. This means
sails, smaller dredging equipment, and slower movement across the
oyster beds.
Regulation which revolves around restrictions on the minimum size
of fish that are legal to harvest are designed to leave a portion of the
fish stock in the water to provide a sufficient breeding stock to
ensure future populations.
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Fishers generally implement this restriction by choosing a mesh size
for their nets that allows smaller, illegal fish, to escape.
Because fishing activity may disrupt the spawning process, often the
fishing season is closed for a certain period on an annual basis,
generally during spawning season.
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Also, some species become so extremely congregated during
spawning that fishing effort could capture virtually the entire
population.
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Current Fishing Policy
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Regulations on where fish may be caught are
designed to protect fish stocks when they are
congregated and vulnerable to overharvesting.
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These types of regulations also protect vulnerable fishing
habitats from destruction by the fishing process.
There can be limits on how many fish may be captured
in a given time period.
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These limits may be in the form of weight caught, number of
fish, or volume of catch.
Example, the catch limit on giant bluefin tuna is 1 fish per
boat. A fish can often weigh as much as 1000 pounds and the
market price has been $18 per pound.
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Individual transferable quotas
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Individual transferable quotas (ITQs) would work in a fashion
similar to marketable pollution permits.
By limiting the number of catch quota which are issued, bidding
for the quotas will occur until the price of the quota is exactly
equal to the divergence between average cost and price
(average rent).
Limited entry techniques structured to direct effort rather than
catch can also be developed.
Here only a fixed number of boats would be allowed to operate in
the fishery.
The method of permit allocation could be by auction or historical
presence in the fishery.
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Limited Entry Techniques
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If these ITQs are transferable, it will be possible to
have only the most efficient fisherman in the fishery.
Enforcement of effort-based limits, that is vessel
permits, would be much easier than that associated
with the catch limits.
No measuring or weighing is necessary; a poster
sized certificate of operation would allow easy
identification of legal vessels.
Catch-based ITQs are subject to several problems.
People might cheat on their quota by selling to
foreign vessels or in an underground market.
Another problem is associated with the differing
market values of different size fish.
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Limited Entry Techniques
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Although most fishery regulation relies on open-access
techniques, an important example of a limited entry technique is
the Virginia oyster fishery, where oyster beds are treated as
private property.
It gives oyster bed operators incentive to invest in their property
such as seeding with larval oysters and creating more structures
to which the oysters can attach.
An additional example of the limited entry regulation is the
economic exclusion zone, established under the authority of the
United Nations Convention of the Law of the Sea.
This regulation established a 200 mile limit along the coast of a
country where each country has the right to limit access to their
waters. This is a partial limited access regulation.
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Other Issues in Fishery Management
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Other problems associated with fishery
management include:
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incidental catch;
destruction of habitat through fishing activities;
destruction of wetlands and related habitat
through non-fishing activities;
pollution of fishery habitat;
conflicts between user groups and
international cooperation concerning the
harvesting of migratory species.
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Aquaculture
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Aquaculture, the cultivation of fish in artificial
environments or in contained natural environments, is
often suggested as a means of dealing with the openaccess problem.
Not all species can be cultivated.
Shellfish are ideal because of their inherent immobility.
Wildfish will benefit indirectly from aquaculture if the
"farmed" species usurps part of the market demand for
the wildfish and therefore reduces the fishing pressure
on the species.
Aquaculture creates its own set of problems.
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Aquaculture
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Aquaculture can damage the environment,
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e.g., Shrimp aquaculture in Central and South
America has resulted in a loss of mangrove
forests, excess nutrient loading into estuaries and
severely reduced dissolved oxygen in areas
bordering estuaries.
There are also potential problems associated
with hybridized fish escaping and damaging
the gene pool of existing species.
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Gill Nets and Long Lines
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Often the fisher will catch not only the species that
they seek but also other species, referred to as
incidental catch.
Many types of fishing gear do not discriminate
among fish species, and both the desired species
and a spectrum of untargeted species are caught by
this gear.
Among the most notorious of these are the gill nets,
whose lengths often measured in miles.
These nets are vertically suspended in the water,
like underwater fences, ensnaring the gill covers of
fish as they attempt to back out.
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Gill Nets and Long Lines
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Another indiscriminate fishing method is "longlining."
A long-line consists of line that may be 10 kilometers
in length or longer, with baited hooks every several
meters.
These lines are employed off the Atlantic coast in
pursuit of highly profitable swordfish.
Because sharks are often caught, these long-lines
have been an important factor in the decline of the
shark populations.
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Gill Nets and Long Lines
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Due to the difficulties of monitoring, restrictions on fishing
methods may be preferential to policies based on economic
incentives.
An example of this type of policy is the requirement that
shrimpers install a Turtle Excluder Device (TED) in their nets to
allow endangered sea turtles to escape.
In addition to the turtles which are "kicked" out of the shrimp net,
non-targeted fish are also allowed to escape.
Whether policy makers should implement the restrictions on gill
nets and long-line operations needs to be determined on a caseby-case basis for each potential restriction.
The benefits of protecting untargeted species are spread out
over a large number of people, but the costs are concentrated
upon a very few.
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Destruction of Habitat Through Fishing
Activities
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Some fishing techniques can cause damage to the
ecosystem in which the fish exist, diminishing the
productivity of the fishery and ecological services.
Damage can occur when contact of fishing gear with
the floor of the estuary or ocean uproots aquatic
plants, breaks coral, dislodges shell fish, and so on.
One particularly sensitive ecosystem is that
associated with a coral reef, where anchors and
boat bottoms dragging across the coral can kill it.
Even more destructive is the practice of fishing
using explosions or the use of cyanide in the coral to
stun and collect fish for consumption and
aquariums.
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Destruction of Wetlands and Related
Habitat
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Other habitats such as upland and coastal wetlands,
temperate forests and free flowing rivers are
critically important to fisheries.
The temperate rainforests of the Pacific Northwest
are critically important to maintaining the riverine
habitat, which is essential to anadromous fish, such
as salmon and steelhead.
Any activity which impacts the quality of these
ecosystems can impact the quality of the riverine
system and the salmon and steelhead.
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Pollution of Fishery Habitat
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In the United States, many fisheries are in decline
because pollution has diminished habitat.
This pollution and loss of habitat has affected
virtually every freshwater species, and many
saltwater species, where saltwater species are
affected by estuarine pollution.
Anadromous species such as salmon, steelhead,
shad, and striped bass are particularly vulnerable to
riverine pollution.
In developing countries, soil erosion from
deforestation and intensive cultivation of hillside
lands has severely impacted water quality not only
in the rivers, but in reservoirs, estuaries, lagoons,
and coral reefs.
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Management of Recreational Fishery
Resources
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In most North American recreational fisheries, there is
unrestricted access to the resource, leading to open-access
exploitation.
Recreational policies take the form of limits on the number of fish
that may be kept, restricted seasons, and size limits.
By stocking fish, where a very large number of fish are hatched,
grown to size, and released into the wild, the problem of openaccess is addressed by increasing resource base.
Recreational fisheries often have closed seasons timed to
coincide with spawning periods in the fishery.
Access improvements such as launching ramps, fishing piers,
parking areas, and artificial reefs can be designed to reduce
congestion in the fishery, although they may also lead to
increased use.
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Management of Recreational Fishery
Resources
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Catch and release programs are based on the idea that a
recreational angler does not have to kill his or her catch to
produce utility from fishing.
These regulations allow fish to be caught, released, and left to
grow, reproduce, and be caught again.
Catch and release regulations generally take the form of moral
suasion and command and control.
Size limits place restrictions on the minimum (and sometimes
maximum) size of fish that are legal to keep.
Creel limits place restrictions on the maximum number of fish per
day that may be kept.
Both restrictions are designed to protect the reproductive viability
of the fish stocks.
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Summary
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Fishery resources are renewable but destructible.
The destructibility problem is amplified by the openaccess nature of many of the world’s fishery
resources.
For commercial fishing, optimal management
strategy requires the limitation of effort to a level that
maximizes the sum of consumers’ surplus,
producers’ surplus, and fishery rent.
Actual fishery management seldom achieves this
goal and is based on developing restrictions on how,
when, where, and how much fish can be caught.
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