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North Pacific Ocean Knowledge Network (DEMO)
Understanding Ocean Change Across the North Pacific

Pacific Halibut

Gadus macrocephalus

BELOW TARGET BIOMASS

Historic Low Spawning Biomass - Continued Decline

Pacific halibut spawning biomass is at 38% of unfished state as of 2025 (149 million lbs / 65,771 MT) - the lowest level since the 1970s. The stock declined 32% from 2016 to 2024, then increased slightly (3%) in 2025 due to maturing 2012 and 2016 year classes. A critical challenge is the dramatic size-at-age decline: a 20-year-old halibut that weighed ~121 lbs in 1988 now weighs only ~44 lbs, reducing spawning biomass. The 2024 harvest (21.4M lbs) was the lowest since the 1970s, with fishermen catching only 74% of the commercial catch limit. IPHC implemented a 15.8% coastwide TAC reduction for 2025 (29.7M lbs) following the January 2025 annual meeting where the lowest spawning biomass in 40 years was reported. Stock is managed internationally (US-Canada) through the International Pacific Halibut Commission (IPHC) with rebuilding efforts ongoing across all regulatory areas.

Stock Status (2025 Assessment)
38%
% Unfished State
Lowest since 1970s
149M
Spawning Biomass (lbs)
65,771 MT
-32%
Biomass Change
2016 to 2024
29.7M
2025 TCEY (lbs)
15.8% reduction
~50%
Size-at-Age Decline
Since 1980s
IPHC
Management Body
US-Canada 🇺🇸🇨🇦
📝

Note on Stock Status

While Pacific halibut is not officially "overfished" under federal definitions (the stock declined primarily due to environmental factors including size-at-age decline, weaker recruitment, and marine heatwave impacts), the spawning biomass is critically low. IPHC has established 30% of unfished state as a threshold of concern and 20% as triggering directed fishery closure. At 38%, there is a 30% probability the stock is already below the concern threshold.
Spawning Biomass Decline Trend (2016–2025)

Long-term Decline in Spawning Stock Biomass

2016201720182019202020222025
Spawning Biomass (lbs) — Source: IPHC Annual Assessments & Federal Register
Life Cycle & Distribution
🗺️
Life History & Distribution Map

Pacific cod spawning areas, juvenile nursery habitats, adult feeding areas, and seasonal depth migrations in the Gulf of Alaska and Bering Sea.

Key Population Challenges

Critical Size-at-Age Decline

  • 20-year-old females: 121 lbs (1988) → 44 lbs (2014) = 64% reduction
  • 12-year-old halibut: Now ~50% of 1980s weight
  • Causes: Size-selective fishing (30-65%), arrowtooth flounder competition, intraspecific competition, climate variability
  • Impact: Significantly reduces spawning biomass calculations even with stable fish numbers
2024 Harvest
21.4M lbs
Lowest since 1970s
Fishery Achievement
74% of limit
Typical: 90%
Recruitment Status
Below historical
Weaker than 1980s
Strong Year Classes
2012, 2016
Currently maturing
Threshold Concern Risk
30% probability
Below 30% unfished
Closure Risk
11% probability
Below 20% unfished
🔎
Key Finding: Pacific halibut faces a complex crisis driven by multiple stressors. The dramatic size-at-age decline means individual fish contribute less to spawning biomass and fishery yields. Size-selective fishing has removed larger, faster-growing fish over decades. Competition with expanding arrowtooth flounder populations and high halibut densities may limit growth. Climate variability affects metabolic rates and prey availability, though mechanisms remain uncertain. The population is not recovering despite reduced fishing pressure.
Data Confidence: HIGH · Based on IPHC FISS annual surveys & comprehensive stock assessment
Data Sources: International Pacific Halibut Commission (IPHC) 2025 Annual Meeting (Jan 27-31, 2025), Federal Register 2025 Management Measures (March 21, 2025, 90 FR 13294), IPHC 2024 Stock Assessment, NOAA Fisheries Stock Status, Sullivan et al. (2016) environmental and ecological variability study, Rodrigues et al. (2022) Future climate vulnerability (ScienceDirect), NCCOS habitat projection studies.Stock Assessment: IPHC uses ensemble of 4 population dynamics models (2 long time-series 1888-present, 2 short time-series 1992-present). AFSC survey (2019–2024). Last Update: October 2025 ·BIC Project: Basin-scale Events and Coastal Impacts | North Pacific Ocean Knowledge Network
🐠 Life History
Maximum Age
~55 years
Max Size (Historical)
~500 lbs
Male Maturity
7-8 years
Female Maturity
8-12 years
Spawning Depth
183-457m
Trophic Level
4.3 (predator)
Habitat
Demersal, 20-1000m
🗂️ Management
Management Body🇺🇸🇨🇦 IPHC
2025 TCEY29.7M lbs (13,480 MT)
2024 Harvest21.4M lbs
US Commercial Value~$120M (2021)
Management SystemIFQ (since 1995)
Min. Commercial Size32 inches
Fishery StatusActive (reduced quotas)
Assessment CycleAnnual
Below Target (38% unfished)Quota Reductions ActiveSize-at-Age CrisisWeak Recruitment
Climate Vulnerability
Overall VulnerabilityMODERATE
Temperature SensitivityLow-Moderate
Oxygen SensitivityHigh
Habitat FlexibilityHigh (depth range)
2100 Habitat Loss (Alaska)50% projected

Primary threats: Dissolved oxygen decline (especially for juveniles at 100m depth), suitable habitat compression and loss by 2100, prey availability changes, and phenological shifts. Temperature tolerance relatively good but oxygen decline is critical concern.

Ecosystem Role
Primary PreyHerring, pollock, cod, octopus, crabs
Key PredatorsSeals, sea lions, sharks (adults rare)
CompetitorsArrowtooth flounder (expanding)
Cultural ImportanceVery High (Indigenous, commercial)
Economic Ranking#9 US fishery (by value)

Welcome to the North Pacific Ocean Knowledge Network Dashboard

This interactive platform connects and synthesizes information about changing ocean conditions, key species, and management approaches across the North Pacific. The North Pacific Ocean Knowledge Network is being developed through the Basin-scale Events and Coastal Impacts (BECI) project to transform fragmented research and data into accessible, actionable insights that support climate-informed fisheries management and conservation decisions across jurisdictions.

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