248 



DETERMINE TRULY SUSTAINABLE HARVEST LEVELS 



The problem with Maximum Sustainable Yield 



Some of the core methodologies and concepts used in fisheries management, 

 such as Maximum Sustainable Yield and Optimum Yield (as currently defined), are 

 flawed and often result in inaccurate assessments and unsustainable allowable catch 

 levels. 



Fisheries scientists cannot reliably determine the Maximum Sustainable Yield 

 (MSY) on which the Total Allowable Catch (TAC) is based Fish are part of 

 complex ecosystems which are highly variable and difficult to understand scientifically. 

 In addition, fish population size is not governed simply by the number of spawning 

 fish present, as is often assumed in conventional stock assessment and management 

 Rather, complex ecological factors determine abundance. MSY is probably 

 unattainable in practice, due to these ecological complications. 



These factors are not generally taken into account in assessment and 

 management, due in part to the paucity of information available on their impacts. 

 As a result, sustainable levels of harvest must be determined largely through trial- 

 and-error; but large levels of natural variability mask the effects of overfishing until 

 it is very severe and sometimes irreversible. A number of factors, such as fishing 

 down vulnerable populations, combine to give the appearance that MSY is larger than 

 it really is. As a result, once MSY is achieved it is unlikely to really be sustainable. 

 In addition, even basic survey techniques and extrapolations are sometimes 

 problematic. Flawed population assessment techniques resulted in a severe 

 overestimate of the number of salmon expected to escape the Pacific Northwest 

 fishery to spawn. This, in combination with a number of other management and 

 assessment problems, resulted in overharvesting of coho salmon in recent years. 



Alternatives to MSY 



The first step toward improving fisheries management is to improve the 

 techniques used to determine the sustainable yield. Many fisheries experts recommend 

 the use of a Constant Maximum Sustainable Yield (CMSY), based on the minimum 

 acceptable population size that must remain in the water after harvest, regardless of 

 variations in the carrying capacity of the ocean environment. This is likely to be 

 subject to less uncertainty and be more conservative than the estimation of "surplus 

 production" currently used to calculate MSY. An alternative would be to apply a 

 safety factor accounting for natural variability and scientific uncertainty to MSY in 

 order to arrive at a conservative level of allowable harvest. 



* Language is needed in the MFCMA to direct fisheries managers to re-examine the 

 concept of maximum sustainable yield with a view toward the development and 

 implementation of a more conservative management concept, subject to less 

 uncertainty. 



* An alternative would be to direct the National Academy of Sciences to evaluate 

 MSY and propose alternatives if necessary. 



