Week 4 renewable resources-fish

Renewable resources

Capacity for reproduction and growth over human-relevant time frames.

sustainable yield

Biological growth processes

Growth rate g may be thought of as the difference between the population’s birth and natural mortality rate

Logistic growth, density dependent growth-where growth rate of population depends on population size

smax is the maximum stock size that can be supported in the environment, maximum amount of growth occurs when stock size is equal to half

Steady -state harvests

stock being harvested (H) is equal to the amount of net natural growth of the resource (G)

magnitudes are constant over a consecutive period of time

An open-access fishery

tend to be over-exploited in both a biological and an economic sense.

continuous time notation

commercially exploited, it is assumed that this is done by independent fishing ‘firms’.

each firm takes the market price of landed fish as given

free entry

assumed to be deterministic (not random)

The dynamics of renewable resource harvesting

Stock

Measure of the quantity of the resource existing at a point in time, measured either as the aggregate mass of the biological material in question (such as the total weight of fish of particular age classes or the cubic meters of standing timber), or in terms of population numbers.

Flow

Change in the stock over an interval of time, where the change results either from biological factors, such as recruitment of new fish into the population through birth or exit due to natural death, or from harvesting activity

Renewable stock driven to zero when (stock extinction)

it can also be driven to zero if conditions interfere with the reproductive capability of the renewable resource, or if rates of harvesting continually exceed net natural growth.

when the resource is harvested under conditions of open access than where enforceable property rights prevail;

the higher is the market price of the harvested resource;

the lower is the cost of harvesting a given quantity of the resource;

when prices are endogenous, the more that market price rises as catch costs rise or as harvest quantities fall;

the lower the natural growth rate of the stock;
n the lower the extent to which marginal extraction

costs rise as the stock size diminishes;

the higher is the discount rate.

Changes in other populations may lead to the collapse of some population in which we are interested.

uncertainty in magnitude (size of minimum population threshold, actual stock size)

sustainable yield

constant amount harvested each period (fish caught without decreasing total population)

Policy solutions

• remove externalities

• improving information

• developing property rights

• removing monopolist industrial structures

• direct control or financial incentives to alter rates of harvesting when harvesting programs are inefficient

Absence of forward market for natural resources

extractigng and harvesting intemporally efficent

Improving and providing information important to the pursuit of efficiency ALSO biological and ecological sustainability by Government

In quantitative terms, previous and current behavior has affected or likely to affect the population of a species

Requires significant monitoring and research (unlikely to be done privately)

classes of renewable resources

biological organism capacity for growth

systems sustained in physical or chemical processes (water or atmosphere)

market based instruments for renewables

Transferable fishing licenses, exclusive property rights to particular quantities of harvested fish for set of operators (must be transferable or marketable like property rights)