Fish Flashcards
What is maximum sustainable yield
the highest possible annual catch that can be sustained over time, by keeping the stock at the level producing maximum growth.
When does recruitment overfishing happen
occurs when a stock level is low and the amount of fish that can be harvested is limited because of a lack of adults, which in turn produce too few fish that are able to replenish those that have been removed
What is growth overfishing
is where the recruits to a fishery are caught before they reach the the size that would produce the maximum yield per recruit.
What happens to the growth a stock when it gets excessively large
the growth of the stock
slows down due to competition for food, cannibalism or the limitations in the carrying capacity of
the environment
What is the Stock-Recruitment relationship
relationship between parental stock size and the following recruitment
What are the Stock-Recruitment rules
Must begin at 0 (no females == no offspring)
• Even at high densities, recruitment still happens
• Rate of recruitment decreases continuously with
increasing stock size
• Recruitment must, at some point, exceed the
parental stock size (else stock would collapse
from any system perturbation)
Define spawning stock biomass, SSB
Total biomass of individuals at or above the age of first reproduction
What 4 types of models used in sustainable fishing
Estimating fishery yields (surplus production)
- Delay-difference models (Can account for recruitment, growth and natural mortality)
- Age-structured analyses (VPA, statistical catch at age analysis)
- Yield per recruit models (how much yield per recruit surviving?)
What is Graham’s Theory of Sustainable Fishing (1935)
The fishery is sustainable if removals can be replaced by stock production each year.
Population growth is fastest when the stock size
is maintained at half its carrying capacity; therefore, sustainable yield is greatest.
What is Fmsy
is the fishing mortality that
gives maximum sustainable yield
What is Bmsy
that biomass that gives maximum sustainable yield
What does the European commission consider overfishing to be
considers a fish stock to be overfished when its biomass is below BMSY. In that
situation, it is unable to produce the maximum sustainable yield.
When does overfishing happen
Overfishing occurs when more than the sustainable share is taken out of a given fish stock, i.e. when the fishing rate is above Fmsy
What occurs at zero fishing mortality,
population is limited
by its carrying capacity
What occurs at high fishing mortality (extremely low
densities)
population is limited by its growth
