Marine Science - Unit 8.2 - Sustainable Fisheries

Sustainable fishing

Optimum sustained yield, co-management of fisheries with government set quotas and limits on fishing seasons

maximum sustainable yield (MSY)

the maximum amount that can be harvested without compromising the future availability of that resource

factors which affect fish population - recruitment

-fecundity

-age of reproductive maturity

-growth

-habitat dependency

fecundity

rate of reproduction of organisms

in fish, rate of egg production is a measure of fecundity

Age of reproductive maturity

-is the time when an organism is able to reproduce sexually

-is variable in fish and may depend upon population density. for example, the age at which spawning occurs in sardines decreases as the population density decreases. larger and older fish produce more eggs than younger fish.

growth rate

an expression of the increase in the size of an organism or population over a given period of time

habitat dependency

Most species have complex life cycles. Habitats are important in different stages of the life cycles, if habitat lost the cycle will be disrupted

factors which affect fish populations -losses

-natural mortality

-fishing mortality

natural mortality

Mortality caused by predation, starvation, diseases, accidents, or other natural causes.

fishing mortality

Proportional to the fishing effort and can be estimated using tagging experiments, or by calculation of mortality rates from data obtained from the history of a fishery

-fish caught,harvested,and sold

-bycatch

-discarded fish

-fish killed by indirect means such as habitat destruction

recruitment

≥ natural mortality + fishing mortality

mortality rate (death rate)

natural mortality + fishing mortality

restrictions to ensure sustainable fishing

-season

-quota

-licensing

-marine protected areas

-method (rod and line fishing)

-size of fish (eg. no lobster less than 6")

-intensity (engine, boats)

restricted fishing - short term effects [4]

-reduced fishing intensity

-fewer boats

-increased unemployment

-reduced earnings

restricted fishing - long term effects [2]

-sustainable future fishing

-ensures future employment and income

unrestricted fishing - short term effects [3]

-continued high-intensity fishing

-continued employment

-no reduction in earnings

unrestricted fishing - long term effects [3]

-fish stocks collapse

-total loss of fishing industry

-mass unemployment and loss of income

CPUE (catch per unit effort)

the total catch divided by the total fishing effort

rehabilitation- replanting mangroves [A3][D3]

Advantages:

-prevent coastal erosion

-fish nursery

-increases biodiversity

Disadvantages:

-costly

-may not work

-requires expertise

rehabilitation- building artificial reefs [A2] [D2]

Advantages

-increases fish stock

-increases biodiversity

Disadvantages

-may introduce harmful chemicals

-may damage other habitats

rehabilitation- release of cultivated fish [A1] [D3]

Advantages:

-increases fish stock

Disadvantages:

-may affect gene pool of wild fish

-may introduce disease

-may affect other food chains