Fisheries Management T Review of Maximum Sustainable Yield Concepts and Problems

Reasons to Fish Below the MSY I. Inaccurate Information A. I Fish Therefore I Lie (Schaefer Model) B. Not Enough Biological Data (Beverton-Holt Model) II.Variable Recruitment III. Resource Mismatch IV.Presence of Competitors V.Stock Stability VI.Economics (Law of Diminishing Returns) I.T

Reasons to Fish Below the MSY I. Inaccurate Information A. I Fish Therefore I Lie (Schaefer Model) B. Not Enough Biological Data (Beverton-Holt Model) II.Variable Recruitment III. Resource Mismatch IV.Presence of Competitors V.Stock Stability VI.Economics (Law of Diminishing Returns) I.T

Schaefer Model UnderfishingOverfishing (hours)

Schaeffer Model Requirements: Measurement of Fish Caught Measurement of Fishing Effort

Schaeffer Model Fish Caught per Unit of Fishing Effort: A PROXY for Population Size

Schaefer Model OverfishingUnderfishing (pounds/hour)

Beverton-Holt Model Requirements: Measurement of Fish Caught Knowledge of Fish Biology Population Size (Tagging) Age (Otoliths) Reproductive Biology

Beverton-Holt Model F

Beverton-Holt Model: Application to a Resource-Limited Population F Mortality declines with fishing because: 1.Caught fish don’t die a natural death; 2.A fished population is a younger population, with a lower death rate; 3. Individuals in a fished population have access to more resources, so they are healthier and have a lower death rate. Gross Production declines with fishing less rapidly than M declines because: 1. Individuals in a fished population have access to more resources, so they grow faster and have higher fecundity.

Reasons to Fish Below the MSY I. Inaccurate Information A. I Fish Therefore I Lie (Schaefer Model) B. Not Enough Biological Data (Beverton-Holt Model) II.Variable Recruitment III. Resource Mismatch IV.Presence of Competitors V.Stock Stability VI.Economics (Law of Diminishing Returns) I.T

Percentage contribution of year classes of Norwegian spring spawn herring to the adult stock from 1954 through The very good year class of 1950 began first appearing in significant numbers in 1954 and dominated the adult stock throughout this period.

Reasons to Fish Below the MSY I. Inaccurate Information A. I Fish Therefore I Lie (Schaefer Model) B. Not Enough Biological Data (Beverton-Holt Model) II.Variable Recruitment III. Resource Mismatch IV.Presence of Competitors V.Stock Stability VI.Economics (Law of Diminishing Returns) I.T

Reasons to Fish Below the MSY I. Inaccurate Information A. I Fish Therefore I Lie (Schaefer Model) B. Not Enough Biological Data (Beverton-Holt Model) II.Variable Recruitment III. Resource Mismatch IV.Presence of Competitors V.Stock Stability VI.Economics (Law of Diminishing Returns) I.T

Reasons to Fish Below the MSY I. Inaccurate Information A. I Fish Therefore I Lie (Schaefer Model) B. Not Enough Biological Data (Beverton-Holt Model) II.Variable Recruitment III. Resource Mismatch IV.Presence of Competitors V.Stock Stability VI.Economics (Law of Diminishing Returns) I.T

Fishing at 15% of MSY Fishing at 75% of MSYFishing at 100% of MSY Stock Stability (Population Resilience)

Stock Size

Fishing

Stock Size Good Recruitment

Stock Size Good Recruitment

Stock Size Bad Recruitment

Stock Size Bad Recruitment

Stock Size Low Stock Size

Stock Size Low Stock Size

Stock Size ENSO

Stock Size ENSO

Stock Size Low Stock Size High Stock Size

Stock Size Low Stock Size High Stock Size

Stock Size Low Stock Size High Stock Size

Fishing at 15% of MSY Fishing at 75% of MSYFishing at 100% of MSY

Reasons to Fish Below the MSY I. Inaccurate Information A. I Fish Therefore I Lie (Schaefer Model) B. Not Enough Biological Data (Beverton-Holt Model) II.Variable Recruitment III. Resource Mismatch IV.Presence of Competitors V.Stock Stability VI.Economics (Law of Diminishing Returns) I.T

ECONOMICS

The Canadian Cod Example: Fished to Commercial Extinction Before Establishment of a Moratorium: No Recovery of the Stock, No Recovery of the Fishery

During the 1980s cod catches remained steady but that was because larger, more powerful and sophisticated vessels were chasing the few remaining fish.

During the 1980s cod catches remained steady but that was because larger, more powerful and sophisticated vessels were chasing the few remaining fish. Working harder and harder, to catch the few remaining cod.

"In normal years we'd get 200,000 pounds of cod, but that year it was more like 70,000 pounds. Then all of a sudden they just crashed." Fisheries scientists concluded that quotas had to be more than halved in order to prevent this stock's collapse. Politicians were appalled; the proposed quotas would have caused economic chaos throughout Eastern Canada. So the politicians compromised what could not be compromised. Quotas were cut by only 10 percent. Fishermen tried as hard as they could, but could only catch 122,000 of the 190,000-ton cod quota for The estimated combined weight of the adult cod population was a mere 1.1 percent of its historic levels of the early 1960s.

ECONOMICS Law of Diminishing Returns

Reasons to Fish Below the MSY I. Inaccurate Information A. I Fish Therefore I Lie (Schaefer Model) B. Not Enough Biological Data (Beverton-Holt Model) II.Variable Recruitment III. Resource Mismatch IV.Presence of Competitors V.Stock Stability VI.Economics (Law of Diminishing Returns) I.T