Sustainable Fisheries Management

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Questions and Answers

What event disrupted the ideal conditions for the Peruvian anchovy fishery in 1972?

Overfishing

El Niño system (correct)

Nutrient-rich water influx

Hurricane

What was the main consequence of the environmental changes in 1972 for the anchovy fishery?

Decline in juvenile anchovy populations (correct)

Establishment of fishing regulations

Recovery of fishery stocks

Increased catch levels

What do density-independent factors generally include?

Climatic events and disturbances (correct)

Nutritional availability

Population density

Predation and competition

What was the primary factor regulating the population of Thrips imaginis during the 1930s and 1940s?

Climatic factors impacting food sources Signup and view all the answers

What assumption must managers consider when using the logistic model to estimate the maximum sustainable yield?

Environmental conditions can change carrying capacity Signup and view all the answers

What is a classic example of a density-independent effect on population regulation?

Drought affecting the food supply Signup and view all the answers

How did the anchovy fishery manage to continue harvesting at the maximum sustainable yield despite environmental disruptions?

They failed to adjust to changing conditions. Signup and view all the answers

Which of the following represents an intrinsic factor that can affect a population's growth?

Food source availability Signup and view all the answers

What does maximum sustainable yield (MSY) refer to?

The maximum number of individuals harvested without jeopardizing the population. Signup and view all the answers

At what population level does the highest production rate of biomass increase occur in a fish population growing logistically?

At half of the population’s carrying capacity. Signup and view all the answers

What was one of the significant methods used by M. Graham to set fishing limits?

Using data from fish trawlers and logistic growth model. Signup and view all the answers

What does the fishing quota need to achieve to maintain the maximum yield?

It should keep the population at the steepest point of the logistic curve. Signup and view all the answers

How did fishery managers estimate the annual maximum sustainable yield for the anchovy population?

By fitting the logistic growth curve to collected data. Signup and view all the answers

What was the estimated MSY for the anchovy fishery?

10 million tons per year. Signup and view all the answers

What factors do fishery managers consider when setting limits for harvested biomass?

Total biomass harvested, natural mortality losses, and seabird consumption. Signup and view all the answers

What is a potential consequence of not allowing the fish population to recover after each harvest?

Decreased population leading to possible extinction. Signup and view all the answers

Study Notes

Maximum Sustainable Yield (MSY)

MSY aims to maintain populations of fish, trees, and game at levels that prevent extinction while maximizing economic profit.
Economic profit is achieved through maximum harvests, necessitating population recovery post-harvest.
The relationship between biomass of new adults and adults remaining alive must balance losses from natural mortality and harvest.

Logistic Growth Model

Developed by fishery biologist M. Graham in 1935 using North Atlantic trawler data.
Highest biomass increase occurs at half the population's carrying capacity rather than at maximum density.
Fishing quotas should maintain populations at this optimal point to ensure sustainable yield.
The model has guided management decisions for various fish stocks, including the significant Peruvian anchovy fishery.

Peruvian Anchovy Case Study

Managers estimated an MSY of approximately 10 million tons per year by analyzing multiple years of catch data.
The model assumed logistic growth; however, the 1972 El Niño disrupted conditions, leading to an ecological and economic collapse.
Overharvesting continued despite environmental changes, highlighting the need to account for fluctuations in carrying capacity.

Density-Independent Factors

Unlike density-dependent factors, these variables impact populations regardless of their density.
Major climatic events (e.g., hurricanes, floods) or disturbances (e.g., fires) can decimate population numbers uniformly.
Thrips imaginis study illustrated that population declines were more influenced by environmental factors (like drought) rather than population density.

Regulatory Factors and Impacts

As population density increases, regulatory factors become more pronounced, affecting growth rates and management strategies.
Understanding the balance between density-dependent and density-independent factors is vital for effective species management.
The case of cougars in North America underscores the impact of habitat destruction and overhunting on population distribution and survival.

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Description

This quiz covers key concepts related to Maximum Sustainable Yield (MSY) and the Logistic Growth Model in fisheries management. It also examines the Peruvian Anchovy case study, highlighting the importance of maintaining fish populations while maximizing economic profits. Test your understanding of sustainable practices in fisheries.