North Pacific Council SSC Role in Stock Assessment, Peer Review, and Annual Catch Limits for Groundfish Terry Quinn, SSC Member National SSC Workshop Honolulu, Hawaii November 12-14, 14, 28
Stock Assessments of North Pacific Groundfish Data Available Surveys: bottom trawl, longline, hydroacoustic Observers: catch composition by species; length and age data collection. Life History: age, growth, mortality, maturity, etc. Catch: total catch by area & species. Assessment modeling Authors: NMFS AFSC scientists prepare full assessments for all target stocks. Models: Nearly all assessments based on age structured models. Internal Review: AFSC. External Reviews: CIE; Plan Teams; SSC
SAFE Report Stock assessments are compiled in annual groundfish stock assessment and fishery evaluation (SAFE) report, which consists of 4 parts: 1. BSAI Groundfish: >1,2 pages; 2 assessments, plan team recommendations on OFL/ABC. 2. GOA Groundfish: 6-1,2 pages; 21 assessments [some biennial], plan team recommendations on OFL/ABC 3. Ecosystem Considerations: >35 pages; indicators and new information on ecosystem and nontarget species. 4. Economic Status >3 pages; summarized economic data (catch, discards, bycatch, effort indicators (vessel counts, sizes, weeks participating), production, prices and values, and external factors. Notes: The AFSC issues a guide to stock assessment authors on standard information to include in their assessments developed in consultation with the SSC. The SSC has guidelines for review of SAFE reports.
The Process for Specifying Catch Limits [EIS]
Catch Limits In the North Pacific, annual catch limits are specified where: TAC<ABC<OFL OFL (overfishing level) is harvest limit associated with MSY. Acceptable Biological Catch (ABC) Total Allowable Catch (TAC) ABC (acceptable biological catch) is the harvest limit that takes into account uncertainties in the assessment process. TAC (total allowable catch) is the target that includes socioeconomic considerations. TAC may be set lower than ABC: to remain under 2 mmt OY limit in Bering Sea; to limit incidental catch of halibut; to increase rebuilding rate or address other conservation issues; or, to account for state water removals. The fisheries are managed so that catch (incl. discards) < TAC. The SSC sets the OFL and ABC.
OFL and ABC based on biomass For most stocks: ABC or OFL = Fishing Mortality (F) applied to Exploitable Biomass (B) 1. Determine Biomass: Age structured models incorporating survey data, catch and observer data, life history information, etc. 2. Determine Fishing Mortality: Based on a series of tiers, depending on information available. -- F OFL Example F 35% -- F ABC.. Example F 4% Where Fx% refers to the F associated with an equilibrium spawner per recruit (SPR) that is x% of the level in the absence of fishing. Exception: For stocks without reliable biomass estimates (e.g. squid, octopus), OFL and ABC based on historical catches.
Control Rules for OFL and maxabc based on data available Based of Quality of Data Tier 1 -- Reliable B, B msy, pdf of F msy Tier 2 -- Reliable B, B msy, F msy, F 35%, F 4% Tier 3 Reliable B, B 4, F 35%, F 4% Tier 4 Reliable B, F 35%, F 4% Tier 5 -- Reliable B and M Tier 6 Reliable Catch History Data Note: pdf = probability density function.
OFL and maxabc control rules: Tiers 1-2 Tier 1 - Reliable point estimates of B, B MSY, and reliable pdf of F MSY. Tier 2 - Reliable point estimates of B, B MSY, F MSY, F 3%, and F 4%. 1a) Stock status: B/B MSY > 1 F OFL = ma, arithmetic mean of pdf F ABC < mh, harmonic mean of pdf 1b) Stock status: a < B/B MSY <1 F OFL = ma (B/B MSY - a)/(1 - a) F ABC < mh (B/B MSY - a)/(1 - a) 1c) Stock status: B/B MSY < a F OFL = F ABC = 2a) Stock status: B/B MSY > 1 F OFL = F MSY F ABC < F MSY (F 4% /F 35% ) 2b) Stock status: a < B/B MSY < 1 F OFL = F MSY (B/B MSY - a)/(1 - a) F ABC < F MSY (F 4% /F 35% ) (B/B MSY - a)/(1 - a) 2c) Stock status: B/B MSY < a F OFL = F ABC = Note: a=default value of.5.
OFL and maxabc control rules: Tier 3 Tier 3 - Reliable point estimates of B, B 4%, F 35%, F 4%. 3a) Stock status: B/B 4% > 1 F OFL = F 35% F ABC < F 4% 3b) Stock status: a < B/B 4% < 1 F OFL = F 35% (B/B 4% - a)/(1 - a) F ABC < F 4% (B/B 4% - a)/(1 - a) 3c) Stock status: B/B 4% < a F OFL = F ABC = Tiers 1-3 provide for automatic rebuilding as F ABC and F OFL rates depend on biomass relative to B MSY or B 4 for most stocks. In other words, the lower the biomass, the lower the F ABC and F OFL rates applied to generate the ABC and OFL. Tier 3 control rule Note: a=default value of.5.
OFL and maxabc control rules: Tiers 4-6 Tier 4 - Reliable point estimates of B, F 35%, and F 4%. F OFL = F 35% F ABC < F 4% Tier 5 - Reliable point estimates of B and M. F OFL = M F ABC <.75 M Tier 6 - Reliable catch history from 1978 through 1995. OFL= the average catch from 1978-1995, unless an alternative value is established by the SSC based on best available scientific information ABC <.75 OFL Note: a=default value of.5. Also, the directed fishing for pollock, Pacific cod, or Atka mackerel will be prohibited if spawning stock < 2% of unfished level (Steller sea lion mitigation).
Stocks by Tier, 28 Tier 1: Tier 2: Tier 3: Tier 4: Tier 5: Tier 6: Bering Sea: Pollock, Yellowfin sole, Rock sole. None Bering Sea: Sablefish, Greenland turbot, Arrowtooth flounder, Flathead sole, Alaska plaice, Pacific ocean perch, Northern rockfish, Atka mackerel, Pacific cod, AI pollock. Gulf of Alaska: Pollock, Sablefish, Deep-water flatfish, Rex sole, Shallow-water flatfish, Flathead sole, Arrowtooth flounder, Pacific ocean perch, Northern rockfish, Rougheye rockfish. Gulf of Alaska: Shortraker rockfish, Other slope rockfish, Demersal shelf rockfish. Bering Sea: Bogoslof pollock, Other flatfish, Shortraker rockfish, Rougheye rockfish, Other rockfish, Skates. Gulf of Alaska: Pacific cod, Thornyhead rockfish, Skates. Bering Sea: Squids, Sharks, Sculpins, Octopus. Gulf of Alaska: Atka mackerel.
Example Tier 1: BSAI Pollock Assessment 2 Catch (1, M.Tons) 1964-27 Survey Biomass 1979-27 Line=On-Bottom Trawl, Diamonds Dots = Off-Bottom 15 1 5 1964 1974 1984 1994 24 1 5 1979 1984 1989 1994 1999 24 7 5 EBS Pollock Age 1 Recruits in Billions Average Recruitment 1964-27 = 22.5 15 1 Model Biomass 1964-29 Line=Age 3+ Biomass, Diamonds Dots = Female Spawning Biomass 3 1-11964 1969 1974 1979 1984 1989 1994 1999 24 5 1964 1974 1984 1994 24
Example Tier 1: BSAI Pollock, 28 Stock is in Tier 1, because we have reliable point estimates of B and Bmsy, and a reliable probability density function of Fmsy. It falls into the 1b category because 28 spawning biomass projected slightly less than Bmsy. So: F OFL = F msy,ave (B/Bmsy -.5)/(.95) =.3 F ABC < F msy,har (B/Bmsy -.5)/(.95) =.21 These rates applied to 28 biomass yield: OFL = 1.44 million mt MaxABC = 1.17 million mt Bsmy = 1,876, t female spawning biomass However, the SSC noted the following: There was a 4 yr series of poor recruitment; Year classes appeared weaker than projected; Biomass projected to drop below Bmsy in 28; Reduced weight at age indicated reduced forage; The female spawning biomass approaching B2. So, the SSC agreed with the authors and plan team, and set ABC = 1. million mt. Council set TAC = ABC [This is a limited access privilege program (LAPP) fishery, so there is no chance of overage].
Example Tier 3: BSAI Pacific Ocean Perch 28 25 2 15 1 5 Catch (1, M.Tons) Bottom bar = Aleutians, Top bar = EBS 1977 1982 1987 1992 1997 22 75 6 45 3 15 Survey Biomass (Aleutian Islands Region) 198 1985 199 95 2 25 Age 3 Recruits in Millions, Ave= 82 2 15 1 5 1977 1987 1997 5 4 3 2 1 Model Biomass in Thousand M.Tons, Line = Age 3+ Biomass, Diamond Dots = Female Spawning Biomass 1977 1982 1987 1992 1997 22
Example Tier 3: BSAI Pacific Ocean Perch 28 Stock is in Tier 3, because we have reliable point estimates of B, B4%, and F4%. It falls into the 3a category because 28 spawning biomass projected above B4% (153, mt > 133, mt). So: F OFL = F35% =.7 F ABC < F4% =.59 These rates applied to 28 3+ exploitable biomass (453,mt): OFL = 25,7 mt ABC = 21,7 mt The ABC is further apportioned among regulatory areas based on survey biomass. Council set TAC = ABC for all regulatory areas. [This is another LAPP fishery, so no real possibility of exceeding TAC.]
Another Example Tier 3: GOA Arrowtooth 28 Recruitment (billions age 3 fish) 1.4 1.2 1.8.6.4.2 Recruitment Biomass 2.5 2 1.5 1.5 Age 3+ Biomass (millions mt) Rex sole 3% Shallow water flatfish 17% Flathead sole 13% Deep water flatfish 3% Arrowtooth flounder 64% 1961 1964 1967 197 1973 1976 1979 1982 1985 1988 1991 1994 1997 2 23 26
Another Example Tier 3: GOA Arrowtooth 28 Stock is in Tier 3, because we have reliable point estimates of B, B4%, and F4%. It falls into the 3a category because 28 spawning biomass projected well above B4% (1,275,1 mt > 489,493 mt). So: F OFL = F35% =.222 F ABC < F4% =.186 These rates applied to 28 3+ exploitable biomass (2,244,87 mt): OFL = 266,914 mt ABC = 226,47 mt The ABC is further apportioned across regulatory areas based on biomass. Council set TAC = 43, mt, apportioned by regulatory area based on catch needs. The TAC is set low due to bycatch of halibut in the arrowtooth fishery. Note: This large predator dominates the GOA biomass, raising serious ecosystem concerns as the stock continues to grow.
Example Tier 4: GOA Demersal Shelf Rockfish DSR is a complex of 7 species; 96% of catch is yelloweye rockfish. Biomass based on submersible transect surveys (density estimate of yelloweye applied to available habitat). This is the only groundfish assessment done by state scientists (not NMFS). [State scientists do scallop and crab assessments]
Example Tier 4: GOA Demersal Shelf Rockfish Stock is in Tier 4, because we have reliable point estimates of B, F35%, and F4%. So: F OFL = F35% =.32 F ABC < F4% =.26 However, the SSC agreed with the Plan Team s conservation concerns (unreported discards and decline in CPUE), and set F ABC =M=.2 These rates applied to 28 yelloweye exploitable biomass (18,329 mt), and adding 4% to account for other DSR species: OFL = 611 mt ABC = 382 mt Council set TAC = ABC. Biomass (1s mt) 35 3 25 2 15 1 5 Biomass Catch TAC ABC 199 1992 1994 1996 1998 2 22 24 26 28 1.2 1.8.6.4.2 Catch (1s mt)
Example Tier 5: BSAI Other Flatfish 6 5 4 3 2 1 Catch (MetricTons) 1995 2 25 15 1 5 NMFS Trawl Survey Biomass (Thousand M.Tons, Line = EBS, Diamond Dots = Aleutians) 1982 1987 1992 1997 22 27 Other Flatfish only 2% of all flatfish Assessment Features Alaska Plaice 18 % Rock Sole 22 % Arrowtooth Flounder 17 % Yellowfin Sole 27 % Flathead Sole 12 % Other flatfish 2 % Greenland Turbot 2 % 1. Species Composition -- 16 species from EBS, 5 species from Aleutians, -- Starry flounder = 74 % of Biomass -- Rex & Butter Sole = 25% -- Other misc species = 1%
Example Tier 5: BSAI Other Flatfish 28 M applied by species Rex sole =.17 Dover sole =.9 Others =.2 Biomass estimated by trawl survey = 149, mt F OFL =.17/.9/.2 F ABC =.13/.6/.15 OFL = 28,8 mt ABC = 21,6 mt Council set TAC = ABC
Example Tiers 5+6: BSAI Other Species 28 Other Species complex consists of different groups of species managed as one unit (at least for now): Sculpins (2 species) Skates (11 species) Sharks (3 species) Octopus (6 species) OFL maxabc Sculpins [Tier 5] 53,1 39,8 Skates [Tier 5] 49,96 37,6 Sharks [Tier 6] 62 46 Octopus [Tier 6] 32 24 TOTAL 14, 78,1 6 5 4 3 2 1 Skate and Other Species Catch (MetricTons) Bottom=Skates, Top=Remainder Species 1992 1997 22 Council set TAC = 5, mt Note: The plan team had recommended skates in Tier 3; the SSC disagreed.
Example: Alternate Procedures On occasion, a new assessment model (or parameter in model) may translate to large increases in OFL or ABC. The SSC has sometimes used precautionary stairstep increases to this new level. Example - 26 GOA Pacific Cod. A new assessment was provided, that used new software (Stock Synthesis II), and included a a new maturity-at-length schedule that implied earlier maturation. Based on the new assessment model, the maximum permissible ABC under Tier 3a was 79,618 t for 26, compared to a 25 ABC of 58,1 t. The SSC did not feel comfortable with the large implied increase in fishing mortality because of some concerns over the new maturity schedule, a series of very low recent recruitments in 21-24, and limited experience with the new model. So, the SSC recommended using a stair-step approach and setting the ABC for 26 at 68,859 t [ABC25 +.5 (maxabc26 ABC25)].
Sustainable Catch Limits
Groundfish Stock Status - 28 Bering Sea and Aleutian Islands Region Gulf of Alaska 27 Catch / msy..2.4.6.8 1. 1.2 Pcod EBSPollock Sable POP Atka Yellowfin NrthrnRF Flathead Rock sole Greenland turbot AK_Plaice AIPollock Arrowtth 27 Catch / msy..2.4.6.8 1. 1.2 POP Sable Pollock Pcod NrthrnRF Rougheye Dusky Rex Dover Arrowtth Flathead 1 2 3 B 28 /Bmsy..5 1. 1.5 2. 2.5 3. B 28 /Bmsy
Closing Comments Relatively speaking, the North Pacific is data rich, allowing for age based modeling for most major stocks. The SSC provides final review of assessments and Plan Team recommendations for OFL and ABC catch limits. The OFL and maxabc levels are established by formula, based on tiers of information available. The SSC can (and does) set ABC levels below the maxabc levels to account for population trends or other concerns. Alternate procedures are allowed. In addition to groundfish, the SSC also sets annual OFLs for BSAI crab (based on formula tiers). For Alaska scallops, overfishing is static, and is based on Fmsy=M=.13, and Bmsy = MSY/M = 9.54 million lbs.). Groundfish stocks remain in good shape overall; crab stocks are mixed status; scallop catches ~ ½ MSY.