Lessons for stock assessment from the northern cod collapse

Fisheries assessment scientists can learn at least three lessons from the collapse of the northern cod off Newfoundland: (1) assessment errors can contribute to overfishing through optimistic long-term forecasts leading to the build-up of overcapacity or through optimistic assessments which lead to TACs being set higher than they should; (2) stock size overestimation is a major risk when commercial catch per effort is used as an abundance trend index, so there is continued need to invest in survey indices of abundance trend no matter what assessment methodology is used; and (3) the risk of recruitment overfishing exists and may be high even for very fecund species like cod. This implies that harvest rate targets should be lower than has often been assumed, especially when stock size assessments are uncertain. In the end, the high cost of information for accurate stock assessment may call for an alternative approach to management, involving regulation of exploitation rate via measures such as large-scale closures (refuges) that directly restrict the proportion of fish available to harvest. Development of predictive models for such regulatory options is a major challenge for fisheries assessment science.

[1]  Ransom A. Myers,et al.  Salinity and Recruitment of Atlantic Cod (Gadus morhua) in the Newfoundland Region , 1993 .

[2]  Ransom A. Myers,et al.  What can be learned from the collapse of a renewable resource? Atlantic cod, Gadus morhua, of Newfoundland and Labrador , 1994 .

[3]  Kenneth Patterson,et al.  Fisheries for small pelagic species: an empirical approach to management targets , 1992, Reviews in Fish Biology and Fisheries.

[4]  D. Pauly.  On the sex of fish and the gender of scientists: Collected essays in fisheries science , 1994, Reviews in Fish Biology and Fisheries.

[5]  A. F. Sinclair,et al.  Fish distribution and catchability : what is the appropriate measure of distribution ? , 1994 .

[6]  A. Rosenberg,et al.  In search of thresholds for recruitment overfishing , 1994 .

[7]  André E. Punt,et al.  Placing odds on sustainable catch using virtual population analysis and survey data , 1994 .

[8]  C. Walters,et al.  Quantitative fisheries stock assessment: Choice, dynamics and uncertainty , 2004, Reviews in Fish Biology and Fisheries.

[9]  D. Steele,et al.  The Managed Commercial Annihilation of Northern Cod , 1992 .

[10]  D. P. Swain,et al.  Changes in catchability of Atlantic cod (Gadus morhua) to an otter-trawl fishery and research survey in the southern Gulf of St Lawrence , 1994 .

[11]  S. Pooley,et al.  Fishing for Truth: A Sociological Analysis of Northern Cod Stock Assessments from 1977-1990. Alan Christopher Finlayson , 1997 .

[12]  J. Beddington,et al.  The Relationship between Catch Rates and Abundance in Fisheries , 1984 .

[13]  W. Overholtz,et al.  Causes of Density-Dependent Catchability for Georges Bank Haddock Melanogrammus aeglefinus , 1990 .

[14]  R. Alpoim,et al.  An Assessment of the Cod Stock in NAFO Divisions 3NO , 2000 .

[15]  R. Deriso.  Optimal F0.1 criteria and their relationship to maximum sustainable yield , 1987 .

[16]  J. Dugan,et al.  Applications of marine refugia to coastal fisheries management , 1993 .

[17]  John M. Hoenig,et al.  A simple simulation approach to risk and cost analysis, with applications to swordfish and cod fisheries , 1992 .

[18]  Christopher S. Guy,et al.  An Introduction to Learning and Teaching Styles: Making the Match , 1995 .

[19]  Carl J. Walters,et al.  Calculation of Bayes Posterior Probability Distributions for Key Population Parameters , 1994 .

[20]  C. Walters,et al.  ADAPTIVE MANAGEMENT OF HARVEST RATES IN THE PRESENCE OF A RISK AVERSE UTILITY FUNCTION , 1987 .