Purpose and Need

The 1996 amendments to the MagnusonStevens Act defined the terms “overfishing” and “overfished” to mean a rate or level of fishing mortality that jeopardizes the capacity of a fishery to produce the maximum sustainable yield (MSY) on a continuing basis. Additionally, it required that all FMPs specify objective and measurable criteria for identifying when the fishery is overfished and, in the case of a fishery which is approaching an overfished condition or is overfished, contain conservation and management measures to prevent overfishing and rebuild the fishery. The Magnuson-Stevens Act further required regional fishery management councils to submit amendments, by October 11, 1998, that would bring fishery management plans into compliance. The Magnuson-Stevens Act and the revised guidelines indicate that MSY, treated as a target strategy under the current FMP definition of overfishing, should represent a limit rather than a target. This means that “limit” harvest strategies (such as the rules used to specify overfishing levels [OFL]) should result in a long-term average catch that approximates MSY, and that “target” harvest strategies (such as the rules used to specify ABC) should result in catches that are substantially more conservative than the limit. Because tiers 2-4 of the current FMP definition could be interpreted as treating MSY as a target rather than as a limit, Amendment 56 revised tiers 2-4 by changing the default fishing mortality rate value from F30% to the more conservative estimate of F35%

Analysis

A 24-page EA (final draft dated June 23, 1998) was prepared for this amendment. Two alternatives including the status quo were considered. The alternative chosen was more conservative in that it consistently treats MSY as a limit rather than a target.

Tiers used to determine ABC and OFL for BSAI groundfish stocks under Amendment 56. (1) Information available: Reliable point estimates of B and BMSY and reliable pdf of FMSY .

1a) Stock status: B/BMSY > 1 

FOFL = mA , the arithmetic mean of the pdf

FABC ≤ mH , the harmonic mean of the pdf 

1b) Stock status: a < B/BMSY ≤ 1

FOFL = mA × (B/BMSY - α)/(1 - α) 

FABC ≤ mH × (B/BMSY - α)/(1 - α) 

1c) Stock status: B/BMSY ≤ α 

FOFL = 0

FABC = 0 

(2) Information available: Reliable point estimates of B, BMSY , FMSY , F35% , and F40%. 

2a) Stock status: B/BMSY > 1 

FOFL = FMSY 

FABC ≤ FMSY × (F40% /F35%) 

2b) Stock status: α < B/BMSY ≤ 1 

FOFL = FMSY × (B/BMSY - α)/(1 - α) 

FABC ≤ FMSY × (F40% /F35%)×(B/BMSY - α)/(1 - α) 

2c) Stock status: B/BMSY ≤ α 

FOFL = 0 

FABC = 0 

(3) Information available: Reliable point estimates of B, B40% , F35% , and F40%. 

3a) Stock status: B/B40% > 1 

FOFL = F35% 

FABC ≤ F40% 

3b) Stock status: α < B/B40% ≤ 1 

FOFL = F35% × (B/B40% - α)/(1 - α)

FABC ≤ F40% × (B/B40% - α)/(1 - α)

3c) Stock status: B/B40% ≤ α 

FOFL = 0 

FABC = 0 

(4) Information available: Reliable point estimates of B, F35% , and F40% . 

FOFL = F35% 

FABC ≤ F40% 

(5) Information available: Reliable point estimates of B and natural mortality rate M. FOFL = M 

FABC ≤ 0.75 × M 

(6) Information available: Reliable catch history from 1978 through 1995. 

OFL= the average catch from 1978 through 1995, unless an alternative value is established by the SSC on the basis of the best available scientific information

ABC ≤ 0.75 × OFL

Regulation Summary

Amendment 56 revised the ABC and overfishing definitions set under Amendment 44 to be more precautionary. Like Amendment 44, the maximum allowable rates are prescribed through a set of six tiers which are listed below in descending order of preference, corresponding to descending order of information availability. For most tiers, ABC is based on F40%, which is the fishing mortality rate associated with an equilibrium level of spawning per recruit (SPR) equal to 40% of the equilibrium level of spawning per recruit in the absence of any fishing. To further minimize the possibility of catches jeopardizing a stock’s long term productivity, there is a buffer established between ABC and OFL. Amendment 56 modified the OFL definition from F30% to F35% for stocks having tiers 2-4 information.

Results

These definitions are currently used in the annual catch limit specifications process.