The Oscillating Control Hypothesis Reassessment in view of New Information from the Eastern Bering Sea George L. Hunt, Jr. School of Aquatic and Fishery Sciences University of Washington With help from: Kenneth O. Coyle, Lisa Eisner, Edward V. Farley, Ron Heintz, Franz Mueter, Jeffery M. Napp, James E. Overland, Patrick H. Ressler, Sigrid Salo, Phyllis J. Stabeno
Where I want to go in this talk Walleye Pollock one of USA s most important Fisheries Recently, big drop in pollock biomass in Eastern Bering Sea, now increasing Gap in production of strong year classes What fuels production of young pollock? Role of Sea Ice Long-term consequences
The Bering Sea Russia Cape Navarin Commander Basin Anadyr Basin < 50 m Chirikov Basin 50-100 m Alaska 100-200 m Inner Domain Middle Domain Aleutian Basin (west) Aleutian Basin (east) Outer Domain Modified from: Aydin et al. (2002) and Mueter unpbl
Importance of Walleye Pollock Fisheries Number 1 species in USA by weight 2,298.1 million pounds; 28% of US fish catch Value $323,212, 000 Dutch Harbor/Unalaska USA Number 1 port for weight (612.7 million lb.) Number 2 port for value ($195 million) Source: NOAA Fisheries website
Walleye Pollock Catch eastern Bering Sea and Aleutian Islands Source: NPFMC 2011 SAFE, Dec 2010
Pollock Modeled Biomass Source: NPFMC 2011 SAFE, Dec 2010
Annual Temperature and Fluorescence patterns at Mooring M2 in the Southeastern Bering Sea P.J. Stabeno, NOAA PMEL unpublished data
Ice Concentration between 57 and 58 N on the Southeastern Bering Sea Shelf Figure courtesy of Sigrid Salo, NOAA PMEL
Variation in Copepods (# m-3) with Temperature, SE. Bering Sea Variable Mean temp. C Year 1997 1998 1999 99 Change Mid- Early Late April May March 3.76 3.45 0.32-3.29 C Acartia spp. 961 711 64 Pseudocalanus 1168 893 240 34 72 3.7 Calanoid nauplii 616 626 322 Oithona similis 99 219 28 Onset of Bloom Calanus marshallae -92% -77% -97% -48% -82% Coyle & Pinchuk, 2002
Ice, Wind, Bloom and Copepods Early Ice Retreat Late Bloom, Warm Water Large Copepod Biomass Late Ice Retreat Early Bloom, Cold Water Small Copepod Biomass February March April May June Hunt et al. 2002
Cold Regime Oscillating Control Hypothesis (Bottom-Up Regulation) Beginning of Warm Regime (Bottom-Up Regulation) Warm Regime (Top-Down Regulation) Beginning of Cold Regime (Both Top-Down and Bottom-Up Regulation) Zooplankton Larval Survival Abundance of Piscivorous Adult Fish Juvenile Recruits Hunt et al., 2002
Pollock Recruitment vs. Flatfish Recruitment 2 82 89 1 92 00 84 96 0 77 79 80 90 99 95 91 94 01 98 85 97 93-1 Pollock recruitment anomaly 78 81 8302 05 88 86 03 04-0.5 0.0 0.5 87 1.0 Flatfish recruitment anomaly Figure courtesy of F. Mueter
. Mean CPUE for Age-0 Pollock in the southeast Bering Sea mid-august September surface trawls M ean CPUE 30000 20000 10000 0 2003 2004 2005 2006 2007 2008 2009 Year Data from BASIS Surveys
Distribution of Age-0 Walleye Pollock loge transformed catch per unit effort (fish/m3) Moss et al., 2009 Trans.Amer. Fish. Soc.
Year Class Strength Variable Source: NPFMC 2011 SAFE, Dec 2010
Walleye Pollock numbers-at-age Bottom Trawl Survey Source: NPFMC 2011 SAFE, Dec 2010
Walleye Pollock Numbers-at-Age Acoustic survey Source: NPFMC 2011 SAFE, Dec 2010
Length Frequencies of Pollock Eastern Bering Sea Acoustic Survey Source: NPFMC 2011 SAFE, Dec 2010
Comparisons of Walleye Pollock Caught in Bottom Trawl Survey and Detected in Mid-Water Acoustic Survey Source: NPFMC 2011 SAFE, Dec 2010
What were the Assumptions? Warm water good for copepod survival and growth Euphausiids were always available Warm water good for age-0 pollock feeding and growth Fast growing age-0 pollock will have a greater survival to age-1
The Reality Check The warm years did not lead to big year-classes of pollock Baier and Napp 2003 showed that Calanus marshallae needed an early bloom in cold water Perhaps warm years were good for small copepods but not for the big C. marshallae or for euphausiids So- some bad assumptions! NEW DATA NEEDED
Middle Shelf Copepods (No. m-3) August 1999 vs. 2004 Data Type 1999 2004 Oithona similis 348 1633 P value 0.000 (from Coyle et al. 2008) (Cold) (Warm) Pseudocalanus spp. 404 1211 0.000 Acartia spp. 277 507 0.264 Centropagus abdominalis Calanus marshallae 0 (2.96)-03 0.177 44 (8.13)-04 0.000 Calanoid nauplii 161 2.69 0.015
July Zooplankton Biomass Figure courtesy of J. Napp / N. Shiga
Large zooplankton abundance (# per m3), Bongo Tow, 505 µm mesh net 2002 2003 Hyperiids Neocalanus plumchrus & flemingeri Calanus marshallae 2004 2005 2006 2007
Ice, Wind, Bloom and Copepods Early Ice Retreat Late Bloom, Warm Water Mostly Small Copepods Late Ice Retreat Early Bloom, Cold Water Large Calanus favored February March April May June Modified from Hunt et al. 2002
Abundance of Age-1 Pollock VS. Age-0 Abundance the prior year Age-1 recruitement (millions) 35000 08 30000 06 25000 20000 15000 07 10000 05 03 04 5000 0 0 10000 20000 30000 Age-0 mean CPUE (# per haul) Updated from Moss et al., 2009
Diets of Age-0 Pollock in warm and cold years From Moss et al., 2009
Diets of Age-0 Pollock in warm and cold years by year BASIS Fish Diets; Theragra chalcogramma; <=150 mm 100 Theragra chalcogramma Ammodytes hexapterus Mallotus villosus Fish Shrimp Euphausiids Themisto spp. Large Copepods Small Copepods Limacina helicina Chaetognaths Crab Larvae Larvaceans Small meroplankton Others Prey Items (%) 80 60 40 20 0 2003 2004 2005 2006 2007 2008 2009 Year Figure courtesy of K Coyle, data from the NOAA BASIS Survey Program
Estimates of Calanus marshallae & Euphausiids 4.00 3.50 Euphausiid backscatter 3.00 2.50 2.00 1.50 1.00 0.50 0.00 2003 2004 2005 2006 2007 Year 2008 2009 2010 Euphausiid data from P. Ressler; C. marshallae from J. Napp.
Age-0 Pollock Energy Content kj fish -1 16 12 8 4 0 2003 2004 2005 2006 2007 2008 2009 Jamal Moss unpublished data
Recruitment of Age-1 Pollock as a function of Energy Density of Age-0 fish Source: NPFMC 2011 SAFE, Dec 2010
New Since 2002 Mueter- Pollock recruitment dome-shaped with respect to temperature Moss et al.- Early pollock survival & growth better in warm years; growth weak in cold years (maybe) Baier & Napp- Need early bloom, cool water to have big zoops (C. marshallae, T. raschii) Moss et al- Need sufficient energy to survive winter; size & energy density of age-0s critical Predation on age-0 pollock greater when large zoops scarce in summer
Conclusions Variations in timing of ice retreat affect the availability and size of copepods in spring- warm springs have mostly small copepods, but good early survival of age-0 pollock. High numbers of age-0 pollock in summer do not necessarily lead to high numbers of age-1 pollock the next year In warm years, there is a lack of large crustacean zooplankton in summer, age-0 pollock have low energy density, and there is enhanced cannibalism and possibly more predation In warm years, summer lack of large zooplankton may result from their failure to recruit in the spring
Impacts of Availability of Large Zoops Warm year with late bloom and few large copepods or euphausiids Cold year with early bloom and abundant large copepods and euphausiids Mesozooplankton Age-0s Year 2 and older Age-1s
Biomass of Arrowtooth Flounder on the Eastern Bering Sea Shelf Source: NPFMC 2011 SAFE, Dec 2010
Diets of Arrowtooth Flounder on the eastern Bering Sea Shelf Source: NPFMC 2011 SAFE, Dec 2010
Distribution and Area of Cold Pool in Warm and Cold Years Source: NPFMC 2011 SAFE, Dec 2010
Distribution and Abundance of walleye Pollock in Warm (2003-2005) and cold (2006-2010) Years Source: NPFMC 2011 SAFE, Dec 2010
Cold Regime Oscillating Control Hypothesis (Bottom-Up Regulation) Beginning of Warm Regime (Bottom-Up Regulation) Warm Regime (Top-Down Regulation) Beginning of Cold Regime (Both Top-Down and Bottom-Up Regulation) Zooplankton Larval Survival Abundance of Piscivorous Adult Fish Juvenile Recruits Hunt et al., 2002