Transcript Biological Resources

Chapter 13
Marine Resources
--Oceans and inland waters cover more than 2/3 of the
surface of Earth
--This aquatic ecosystem provides products and
services: commercial and recreational fishing;
transportation services; shore-based and offshore
recreation activities; atmospheric and climate control,
and mineral supplies
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Some Facts
• Figure 13-1, p.240: the total commercial fish harvest
in the world (and in the U.S.) over the last few
decades has increased
• No. 1 U.S. finfish by value is salmon; No. 1 U.S.
shellfish by value is sea scallops
• In North America only about 7% of animal protein
intake comes from fish; in Africa, it is 21%; in
southeast Asia, it is 28%
• As some of the higher-value species (cod…) have
become more scarce, much of the growth in harvest
has been accounted for by lesser-valued species
(sardines…)
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1. Categories of Marine Resources
• Physical resources include petroleum and natural gas,
which form from the buried remains of marine plankton.
This category also includes many other kinds of minerals,
as well as fresh water extracted from seawater by
desalination
• Other energy resources include several methods of
generating electrical power from waves and currents,
wind, tides, and thermal gradients in the oceans
• Biological resources are marine animals and plants
harvested for food and other uses. The commercial
fishing industry has fished many commercial fish stocks
beyond their maximum sustainable yield
• Nonextractive resources include use of the oceans for
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transportation and recreation
Biological Resources
• Biological resources represent all the animals and
plants that we harvest from the sea, primarily for
food
• Marine sources of food provide a significant
proportion of the human population’s protein
intake. Fish, crustaceans, and mollusks constitute
the majority of the world’s commercial marine
harvest
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Biological Resources
• Major types of commercially harvested
• fish, mollusks, and crustaceans.
Major types of commercially harvested
fish, crustaceans, and mollusks
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Seaweed Harvesting
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Biological Resources
• Commercial fishing is a multibillion dollar
industry, and is the most dangerous job in the
U.S., having the highest death rate of any
profession!
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Biological Resources
• A stern trawler net with Statue of Liberty for
scale. Some trawler nets can hold a dozen
747s!
Slides 3-8 and 10-12: http://scidiv.bellevuecollege.edu/gj/Ocean101-Ch15-Resources.pdf
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2. Current Problems in Marine Fisheries
• Excessive harvesting of many commercial fish stocks means that
today we may be close to the catastrophic collapse of many
fisheries
• Some problems relating to fishery management:
1. Overfishing–a status assigned to fish stocks that have been
harvested so thoroughly that there are not enough individuals left
to provide breeding stock to replenish the species
2. Overcapitalization—excessive investments in national fishing fleets
3. Commercial extinction–the depletion of a species to the point
where it is no longer profitable to harvest
4. By-kill–animals unintentionally killed when other species are being
harvested during commercial fishing
5. Water pollution that threatens the health of some species
6. Conflicts over fishing rights both intercountry and intracountry
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By-Kill
• By-kill refers to animals unintentionally killed
during commercial fishing. Tremendous
amounts of by-kill occur during many fishing
operations. One of the main causes of by-kill
are drift nets: large, vertically suspended
floating nets that snare nearly anything that
runs into them. Turtles, seals, dolphins, and
many noncommercial fish species are killed by
the thousands in these nets each year
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3. Modeling a Fishery
• A fishery: a collection of fish that inhabit a
reasonably well delimited section of marine
habitat
• We measure the fish stock in biomass—the
aggregate weight of all the individuals
• Two major natural growth factors:
reproduction; maturation
• Two forces working in the opposite direction:
losses from predation and food scarcities;
losses from natural mortality especially old age
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The Logistic Model of Population Growth for
Figure 13-3, p.245
a Fishery
• Horizontal axis—the size of the biomass; vertical
axis—change in biomass during a period of time
• The inverted U-shaped function starts at the
origin—no fish, no increment
• At higher stocks, the increment is larger, reaching
a maximum at a stock size of s1
• At s0, the different factors are all in balance, so
there is no increment
• Beyond s0 , increment is negative; biomass
decreases
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• Yield: a certain amount of the biomass
harvested and removed each year
• Any stock size is sustainable if the yield matches
the natural increment in the biomass (y2
pounds at s2); stock size would be unchanged
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The Effort-Yield Curve
• Harvesting effort—the economic resource
devoted to catching fish; includes capital goods
(boats and gear), labor, materials, and energy
• Yield is sustained yield (= the natural increment
in the biomass)
• Origin: stock size is s0, increment is 0, effort is 0
• As effort increases, yield increases; at an effort
level of em, yield reaches its maximum point
• At still higher effort levels, stock levels become
reduced; at a very high effort level, stock is 0
Figure 13-4, p.246
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• An effort level of em produces the maximum
sustainable yield (MSY) from this fishery
• MSY
– the maximum biological yield that the fishery is
capable of producing
– the maximum quantity of harvest that can be
realized in the long run
– often regarded as the best target to aim for in
exploiting renewable resources
– new name: long-term potential yield
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Efficient Rates of Effort
•
•
•
•
Net benefits = total revenue – total cost
Total revenue = yield * price
Total cost = cost per unit of effort * effort
Net benefits are maximized at e*
– Maximum net benefits = r1 – r2
• Net benefits at em are lower than at e*
– At em, yield is higher, the extra costs are even
greater, so net benefits are lower
Figure 13-5, p.248
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$
Total cost
r1
r2
0
Total revenue
e*
em
Effort
4. The Problem of Open Access
• Open-access rule: anybody who has wanted to
buy a boat and go fishing had the right to do so
• At e*, there are profits to be made by any
individual entering the fishery
• This incentive continues to exist until total
effort has grown to e0 (p.248) where total
revenue = total cost
• The open-access condition has produced higher
effort levels and smaller stock levels than is
socially efficient; there are too many fishers
exploiting a fishery
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5. Approaches to Fisheries Management
a. Restricting Access
• Territorial use rights in fisheries (TURFs) have
been recognized around particular geographical
areas that make it possible to set boundaries
and exclude would-be encroachers (eg., the
harbor gangs of Maine)—the logic is exclusion
of outsiders
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b. Regulating Fishing Practices
• The dominant approach in fishery regulation
has been command-and-control (CAC) types of
restrictions on fishing practices: closing certain
areas, restricting the size of boats…
• Figure 13-6, p.251
– CAC raises the cost of fishing (restricting the type of
net that may be used makes it more costly to catch
a given quantity of fish)
– Original total cost curve TC1 shifts to TC2 or TC3; now
open access, instead of leading to e0, produces only
em or e3 units of effort
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• Problems
– Although it is possible to reduce effort levels and
increase stock, it makes fishing much more costly
– This type of direct control can never be complete;
when some parts of the fishing enterprise are
constrained, fishers attempt to expand in
uncontrolled directions
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c. Catch Limits
• Authorities establish upper limits on the
quantity of fish that may be taken from
particular fisheries—total allowable catch
(TACs) or total catch quotas
• Problem: derby fishery—fishers have incentive
to do whatever it takes (bigger boats, nets…)
to get bigger shares of the TAC before the
fishery is closed down when the limit is
reached
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d. Individual Transferable Quotas (ITQs)
• Setting TACs and then dividing them up into
quotas for individual fishers will reduce the
incentive for a “race to fish”
• Allow individual quotas to be bought and sold,
and keep track of who owns how many
• Fishers cannot harvest and sell quantities of fish
in excess of their quota holdings
• Monitor the performance of the ITQ market to
spot and manage problems related to
concentrated ownership, community impacts,
and biological uncertainties
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*
*Summarize the main points of today’s
lecture.
*What did you find most interesting about
today’s lecture?
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