APPENDIX 4 

 SCIENTIFIC PRINCIPLES AND TERMS 



In this circumstance a large fishery harvest would 

 not be sustainable in the long run, but it would 

 bring the stock down to the level supporting LTPY. 



Recent average yield (RAY) 



RAY is equivalent to recent average catch. 

 Unless designated otherwise, RAY is the reported 

 fishery landings averaged for the most recent three- 

 year period, 1995-97. 



Stock-level relative to LTPY 



Fo further clarih' resource status, stock level 

 (i.e. abundance) in the most recent year is com- 

 pared with the level ot abundance that on average 

 would support the LTPY har\'est. This is expressed 

 as being below, near, above or unknown relative 

 to the LTPY stock level. In some cases, heavy fish- 

 ing in the past reduced a stock to a low abundance, 

 and even if the stock currently is harvested only 

 lightly, it may take many years tor ir to rebuild. 



Status of resource utilization 



In this report, a resource is classified as 

 underutilized, fully utilized, overutllized, or un- 

 known as a qualitative measure of the level of fish- 

 ery use. This is derived by comparing the present 

 levels of fishing effort and stock abundance to 

 those levels necessarv to achieve LTPY. 



A fisherv resource is defined as fully utilized 

 when the amount of fishing effort used is about 

 equal to the amount needed to achieve LTPY and 

 where the resource is near its LTPY stock level, 

 for full)' utilized fisheries, the RAY and CPY are 

 usually about equal. In most cases, LTPY and CPY 

 are also about equal, but they may differ as a re- 

 sult of production variability. 



A fishery resource is considered overutllized 

 when more fishing effort is employed than is nec- 

 essarv to achieve LTPY. When RAY is greater than 

 C.VW and CPY is less than LTPY, overutilization 

 is indicated. If stock abundance is near the level 

 that on average produces LTPY, RAY mav be 

 greater than LTPY for an overutllized stock, im- 

 ph'ing that recent landing levels cannot be sus- 

 tained. If stock abundance is below the level asso- 

 ciated with LTPY, RAY will likelv be less than 



LTPY 



Additionally, it is possible for RAY, CPY, and 

 LTPY to be about equal while the fishery resource 

 is overutllized. This occurs when reducing fishing 

 effort would have little effect on the amount of 

 catch realized. In such cases, overutilization may 

 not have an apparent adverse effect on produc- 

 tion, but it further reduces the size of the popula- 

 tion, it wastes effort and economic resources, and 

 imposes other deleterious consequences (e.g. ex- 

 cessive bycatch and gear interactions). 



A fishery resource is classified as underutilized 

 when more fishing effort is required to achieve 

 LTPY. This situation is genetally indicated when 

 RAY is less than CPY and CPY is greater than 

 LTPY while stock level is above the reference level 

 that on average produces LTPY. But there may be 

 exceptions. For example, RAY may be held below 

 CPY and LTPY by management to compensate 

 for uncertaint)' in population estimates and eco- 

 system considerations. 



Classification of stock and fishery status 



The utilization level and stock-level relative to 

 LI" PY are the major factors NMFS considers for 

 determining the status of a stock for Our Lii'iiig 

 Occivii, but they may not always give a complete 

 picture or one that is consistent with legal classifi- 

 cations. 



It is important to note the differences between 

 this classification system and the classification sys- 

 tems based on requirements for overfishing defi- 

 nitions or status determination criteria in fishery 

 management plans (FMPs). In 1989, NMFS pub- 

 lished revised guidelines addressing National Stan- 

 dards 1 and 2 of the 1 976 Magnuson Fishery Con- 

 servation and Management Act, as amended 

 (Magnuson Act). Among other things, the intent 

 of the guidelines was to prevent tecruitment over- 

 fishing and to have a conservation standard for 

 each fishery such that stocks were not driven to, 

 or maintained at, the threshold of overfishing. The 

 guidelines defined overfishing as a level or rate of 

 fishing mortalirv that jeopardizes the lonti-term 

 capacitA' of a stock ot stock-complex to produce 

 maximum sustainable yield (MSY) on a continu- 

 ing basis. F^ach FMP was required to specify, to 

 the maximum extent possible, an objective and 



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