Assessment of Pacific herring (Clupea pallasii) popula ons in the northeast Pacific Ocean
Jaclyn Cleary Fisheries and Oceans, Canada Sherri Dressel Alaska Department of Fish and Game Overview of Bri sh Columbia (Canada) and Alaska (USA) Pacific herring
• Popula ons and fisheries • Surveys and stock assessment methods • Biggest challenges • Collabora on and advancement
2 Global distribu on of herring stocks throughout eastern North Atlan c, Arc c and Pacific oceans
ASIA N. AMERICA
EUROPE *
Hay 1985. CJFAS
3 Pacific herring stocks in the northeast Pacific Ocean 3,000
AK BC BC
Alaska
2,000 things
No r (km) British Columbia
Northeast 1,000 Pacific Ocean
−2,000 −1,000 0 1,000 * Eastings (km) Projection: BC Albers (NAD 1983) Pacific herring stocks in the northeast Pacific Ocean that are assessed with age-structured assessment models Pacific herring stocks in the northeast Pacific Ocean
2,000 Alaska AK Kamishak Bay Togiak Bay BC Prince William Sound
1,500 Tenakee Inlet British Seymour Canal Columbia Sitka Sound
Craig
Northeast Northings (km) 1,000 Pacific Prince Rupert District
Ocean Haida Gwaii
Central Coast
Strait of Georgia 500 West Coast Vancouver Island
−1,000 −500 0 500 1,000 * Eastings (km) 5 Projection: BC Albers (NAD 1983) Significance of herring in the Northeast Pacific …
• Key forage fish
NMML
h p://en.wikipedia.org/wiki/Coho_salmon
6 Significance of herring in the Northeast Pacific …
• Key forage fish • High cultural and socio-ecological value for BC Coastal First Na ons and Na ve Alaskans
Photo credits: Sitka Tribe of Alaksa, H.Kitka
7 Significance of herring in the Northeast Pacific …
• Key forage fish • High cultural and socio-ecological value for BC Coastal First Na ons and Na ve Alaskans • Important commercial industry
8 Surveys
Stock assessment models
Biomass trends
9 Available data: Pacific herring stocks in the northeast Pacific Ocean
2,000 Alaska AK Kamishak Bay Togiak Bay BC Prince William Sound
1,500 Tenakee Inlet Data rich stocks British Seymour Canal 30 to 60+ year me series of: Columbia Sitka Sound • Validated catch Craig • Age, length, weight, sex
• Survey indices (egg, milt, Northeast Northings (km) 1,000 biomass) Pacific Prince Rupert District -4 different survey methods Ocean Haida Gwaii
Central Coast Periodic studies to examine: • Maturity, fecundity Strait of Georgia 500 West Coast Vancouver Island
−1,000 −500 0 500 1,000 * Eastings (km) Projection: BC Albers (NAD 1983) 10 Survey methods and loca ons: Survey type
2,000 Alaska Aerial surveys Egg deposition (spawn) surveys Egg index + Milt survey + Acoustic Index
1,500 Togiak, Kamishak: British Aerial surveys of biomass Columbia
PWS: 3 survey indices: Northeast
Northings (km) Egg, mile-days of milt, acous c 1,000 Pacific SE AK and BC stocks: Ocean Egg deposi on (spawn) surveys
500
−1,000 −500 0 500 1,000 Eastings (km) 11 Projection: BC Albers (NAD 1983) Feb-June: Aerial photos of herring spawn ac vity
Typical colour of Pacific ocean
Herring milt turning water aqua blue
Photo credit: K. Daniel Herring egg surveys: 1) Iden fy spawn from flights 2) Determine shoreline length of spawn 3) Transect and quadrat placement 4) Collect quadrat data (egg layers/numbers, vegeta on type and percent) 5) Extrapolate to total survey area (shoreline length, spawn width (i.e. transect length), egg density)
Photo credit: DFO
Photo credit: DFO
Photo credit: ADFG, S.Dressel Photo credit: DFO, K.Daniel Eggs to fish
Number of eggs Fecundity rela onship
Assume 50:50 sex ra o
Biomass of fish Approaches to stock assessment are similar among regions BC BC and Alaska Alaska Catch age models, fi ed to: Minimize nega ve log • Survey index likelihood for catch data, • Propor ons at age (obs) Least squares to minimiza on differences between obs. and rela ve abundance index, • Weight at age (obs) es mated total or rela ve age-composi on, and • Catch (obs/ validated) stock-recruit rela onships abundance index, age-
(given priors distribu ons composi ons, and stock- and penalty func ons) Objec ve func on recruit rela onships (not all)
Models es mate: Es mated using logis c Fixed maturity at age • Selec vity func on over all years or in • Recruitment me blocks Es mated devia ons in M • Maturity at age Es mated over all years or in using random walk • Natural mortality me blocks
Bayesian es ma on: • Spawning biomass and
SBt and SBT+1 reflect uncertainty Frequen st es ma on: median values of marginal SBt and SBT+1 reflect point posterior distribu ons and es mates, and bootstrapped credible intervals confidence intervals (not all)
15 Overview of stock status
16 Stocks with highest overall biomass in recent 25-years
Pacific herring biomass: spawning (lines) and harvest (bars)
Togiak Bay Kamishak Bay Prince William Sound Tenakee Inlet 300 90 90 90 200 60 60 60 100 30 30 30
0 0 0 0
Seymour Canal Sitka Sound Craig Haida Gwaii ) 3
10 90 90 90 90 ) × 3 60 60 60 60
30 30 30 30
Biomass (t 0 0 0 0
Prince Rupert District Central Coast Strait of Georgia West Coast Vancouver Island
90 90 90 90 Biomass (t x 10 60 60 60 60
30 30 30 30
0 0 0 0 1970 1980 1990 2000 2010 1970 1980 1990 2000 2010 1970 1980 1990 2000 2010 1970 1980 1990 2000 2010 Year Years (1970-2016) 25-years 17 Stocks experiencing low biomass trends in recent 25-years Pacific herring biomass: spawning (lines) and harvest (bars)
Togiak Bay Kamishak Bay Prince William Sound Tenakee Inlet 300 12.5 90 10.0 20 200 7.5 60 5.0 10 100 30 2.5 0 0 0 0.0
Seymour Canal Sitka Sound Craig Haida Gwaii
) 25 80 3
) 7.5
10 20 3 75 60 × 15 5.0 50 40 10 2.5 25 5 20
Biomass (t 0.0 0 0 0
Prince Rupert District Central Coast Strait of Georgia West Coast Vancouver Island 80 60 75
Biomass (t x 10 90 60 40 50 40 60 20 20 30 25
0 0 0 0 1960 1980 2000 1960 1980 2000 1960 1980 2000 1960 1980 2000 Year Years (1951-2016) 25-years 18 Biomass synchrony among stocks between regions… Pacific herring relative spawning biomass
Togiak Bay Kamishak Bay Prince William Sound Tenakee Inlet 1.00
0.75
0.50
0.25
0.00 Seymour Canal Sitka Sound Craig Haida Gwaii 1.00
0.75
0.50
0.25 Rela ve biomass
Relative biomass Relative 0.00 Prince Rupert District Central Coast Strait of Georgia West Coast Vancouver Island 1.00
0.75
0.50
0.25
0.00 1970 1980 1990 2000 2010 1970 1980 1990 2000 2010 1970 1980 1990 2000 2010 1970 1980 1990 2000 2010 Year Years (1970-2016) 19 Biomass synchrony among stocks between regions… PacificSitka, Seymour, Craig herring relative spawning biomass Prince Rupert, Haida Gwaii, Central AK Coast, West Coast Vancouver Island BC
1.00
0.75
0.50 Relative biomass Relative Rela ve biomass 0.25
0.00 1970 1980 1990 2000 2010 1970 1980 1990 2000 2010 Year
Seymour Canal Craig Prince Rupert District West Coast Vancouver Island Stock Sitka Sound Haida Gwaii Central Coast
20 Opposing trends between regions… Pacific herring stocks in the northeast Pacific Ocean Seymour Canal Sitka Sound Craig Haida Gwaii 25 2,000 Seymour Canal 60 Sitka Sound AlaskaCraig Haida GwaiiAK 7.5 Kamishak Bay 25
) 20 ) ) 75 ) Togiak Bay 3 3 3 3 60 BC 7.5 10 10 10 10
) 20 ) ) 15 7540 )
3 Prince William Sound 3 3 3 × × × 5.0 50 × 10 10 10 10 10 15 40 × × × 5.0 50 × 2.5 25 Sitka 20
SSB (t SSB (t 10 SSB (t SSB (t 5 2.5 25 20 SSB (t SSB (t SSB (t 0.0 0 0 0 SSB (t 5
0.6 0.0 0 0 0 1.00 1,500 1.00 Tenakee Inlet Seymour Canal Sitka Sound 0.6Craig Haida Gwaii 1.00 1.00 25 British 0.75 0.75 Seymour Canal 0.4 0.4 60 Columbia 7.5 0.75 0.75
) 20 ) ) 75 ) 0.4 Sitka Sound 3 0.4 3 3 3
M M M 0.50 M 0.50 10 10 10 10 15 40 × × × × 5.00.2 500.2 M Haida M M 0.50 Craig M 0.50 0.25100.2 0.250.2 2.5 25 20 0.25 0.25 SSB (t SSB (t SSB (t SSB (t Gwaii 0.0 0.0 0.005 0.00 Northeast 1960 1980 2000 1960 1980 2000 0.0 1960 1980 Northings (km) 2000 0.0 1960 1980 2000 0.00 0.00 0.0 0 0 1,000 0 Prince Rupert District 1960 1980 2000 1960 Pacific1980 2000 1960 1980 2000 1960 1980 2000 0.6 Prince Rupert District Central Coast 1.00 Strait of Georgia 1.00West Coast OceanVancouver Island Prince Rupert District Central Coast Strait of Georgia Haida Gwaii West Coast Vancouver Island 80 60 0.7580 0.7575 ) ) ) 0.4 0.4 ) 90 West 60 3 3 3 60 3 Central75 Coast ) ) ) ) 90 3 3 10 10 3 10 3 40 10 60
M M M 0.50 M 0.50 × × × × Coast 50 10 10 10 40 60 40 10 × × × 0.2 0.2 × 50 40 60 20 0.25 0.25 30 Vancouver 25
20 SSB (t SSB (t SSB (t SSB (t 20 30 25 Strait of Georgia
20 SSB (t SSB (t SSB (t 0.0 0.0 0.00 0.00 SSB (t 0 0 0 Island 500 0 1960 1980 2000 1960 1980 2000 0 1960 1980 2000 0 1960 1980 2000 0 West Coast Vancouver0 Island 1.00 1960 1980 2000 Prince Rupert District Central Coast Strait of Georgia West Coast Vancouver Island 1.00 0.75 0.9 80 0.75 −1,000 0.75 −500 0 500 0.9 1,000 * 0.4 60 75 0.75 ) ) ) ) 900.4 Eastings (km) 3 3 3 60 0.50 3 0.6
M M M 0.50 M 10 10 0.50 10 40 10 Projection: BC0.6 Albers (NAD 1983) M M M M
× × 0.50 21 ×
× 50 400.2 60 0.25 0.250.2 0.3 20 0.25 0.25 0.3 30 25
20 SSB (t SSB (t SSB (t SSB (t 0.0 0.00 0.00 0.0 0.0 0.00 0.00 0.0 0 1960 1980 2000 0 1960 1980 2000 0 1960 1980 2000 0 1960 1980 2000 1960 1980 2000 1960 1980 2000 1960 1980 2000 1960 1980 2000 1.00 0.75 0.9 0.4 0.75 0.50 0.6
M M M 0.50 M 0.2 0.25 0.25 0.3
0.0 0.00 0.00 0.0 1960 1980 2000 1960 1980 2000 1960 1980 2000 1960 1980 2000 What are the biggest challenges to assessing (AK-BC) Pacific herring stocks, and, What can we learn from each other?
22 What are the biggest challenges to assessing (AK-BC) Pacific herring stocks, and, What can we learn from each other?
• Stability in data collec on programs: securing funding for annual surveys and stock assessment • Nonsta onarity: coping with me varying changes in growth, maturity and natural mortality in stock assessment and in the es ma on of biological reference points
23 Example: Es ma ng natural mortality
• According to Clark (1999, CJFAS): Natural mortality is the most influen al parameter in fisheries stock assessments, rela ng directly to es mated stock produc vity, sustainable catch, op mal exploita on rates and calcula on of reference points.
24 Example: Es ma ng natural mortality
Kamishak Bay SitkaSitka Sound WestWCVI Coast Vancouver Island ) 3
75 75 ) ) ) 3 3 3 20 10 10 10 × × × 50 50
10 25 25 Biomass (t Biomass (t Biomass (t
Biomass (t x 10 0 0 0
0.9 0.9 0.9
0.6 0.6 0.6 M M M M
0.3 0.3 0.3
0.0 0.0 0.0 1960 1980 2000 1960 1980 2000 1960 1980 2000 1960 1980 2000 1960 1980 2000 1960 1980 2000 Es ma ng constant M Es ma ng M in me blocks Es ma ng me varying across me according to changes in devia ons in M using a PDO if it results in random walk, with cubic improved model fits spline interpola ng (defined by AICc criterion)
25 Example: Es ma ng natural mortality
Kamishak Bay SitkaSitka Sound WestWCVI Coast Vancouver Island ) 3
75 75 ) ) ) 3 3 3 20 10 10 10 × × × 50 50
10 25 25 Biomass (t Biomass (t Biomass (t
Biomass (t x 10 0 0 0
0.9 0.9 0.9
0.6 0.6 0.6 M M M M
0.3 0.3 0.3
0.0 0.0 0.0 1960 1980 2000 1960 1980 2000 1960 1980 2000 1960 1980 2000 1960 1980 2000 1960 1980 2000 Addressing cri cal challenges through collabora ons: • Can we further inves gate nonsta onarity (e.g., in M) within stock assessment models using a joint simula on study to iden fy best approaches for es ma ng M for herring • Adop ng similar approaches for es ma ng M could provide consistent basis for
es ma ng biological reference points (e.g., B0) that are comparable across regions
26 What are the biggest challenges to assessing (AK-BC) Pacific herring stocks, and, What can we learn from each other? Other areas for collabora on: Catch age models, fi ed to: • Survey index Joint studies to • Propor ons at age (obs) inves gate changes in • Weight at age (obs) weight-age, fecundity, • Catch (obs/ validated) and growth
Objec ve func on
Models es mate: • Selec vity • Recruitment Field study • Maturity at age • Natural mortality Simula on study • Spawning biomass and uncertainty
27 What are the biggest challenges to assessing (AK-BC) Pacific herring stocks, and, What can we learn from each other?
• We’re keen on developing on-going collabora ons to help us address current challenges such that both countries can advance our respec ve herring stock assessment programs with more synchrony and improve assessment approaches for this key forage species
28 Acknowledgements: • Ma Grinnell • Greg Buck • Ted O s • Kyle Hebert • Steve Moffi
29