The Oscillating Control Hypothesis Reassessment in view of New Information from the Eastern Bering Sea

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1 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

2 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

3 The Bering Sea Russia Cape Navarin Commander Basin Anadyr Basin < 50 m Chirikov Basin m Alaska m Inner Domain Middle Domain Aleutian Basin (west) Aleutian Basin (east) Outer Domain Modified from: Aydin et al. (2002) and Mueter unpbl

4 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

5 Walleye Pollock Catch eastern Bering Sea and Aleutian Islands Source: NPFMC 2011 SAFE, Dec 2010

6 Pollock Modeled Biomass Source: NPFMC 2011 SAFE, Dec 2010

7 Annual Temperature and Fluorescence patterns at Mooring M2 in the Southeastern Bering Sea P.J. Stabeno, NOAA PMEL unpublished data

8 Ice Concentration between 57 and 58 N on the Southeastern Bering Sea Shelf Figure courtesy of Sigrid Salo, NOAA PMEL

9 Variation in Copepods (# m-3) with Temperature, SE. Bering Sea Variable Mean temp. C Year Change Mid- Early Late April May March C Acartia spp Pseudocalanus Calanoid nauplii Oithona similis Onset of Bloom Calanus marshallae -92% -77% -97% -48% -82% Coyle & Pinchuk, 2002

10 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

11 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

12 Pollock Recruitment vs. Flatfish Recruitment Pollock recruitment anomaly Flatfish recruitment anomaly Figure courtesy of F. Mueter

13 . Mean CPUE for Age-0 Pollock in the southeast Bering Sea mid-august September surface trawls M ean CPUE Year Data from BASIS Surveys

14 Distribution of Age-0 Walleye Pollock loge transformed catch per unit effort (fish/m3) Moss et al., 2009 Trans.Amer. Fish. Soc.

15 Year Class Strength Variable Source: NPFMC 2011 SAFE, Dec 2010

16 Walleye Pollock numbers-at-age Bottom Trawl Survey Source: NPFMC 2011 SAFE, Dec 2010

17 Walleye Pollock Numbers-at-Age Acoustic survey Source: NPFMC 2011 SAFE, Dec 2010

18 Length Frequencies of Pollock Eastern Bering Sea Acoustic Survey Source: NPFMC 2011 SAFE, Dec 2010

19 Comparisons of Walleye Pollock Caught in Bottom Trawl Survey and Detected in Mid-Water Acoustic Survey Source: NPFMC 2011 SAFE, Dec 2010

20 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

21 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

22 Middle Shelf Copepods (No. m-3) August 1999 vs Data Type Oithona similis P value (from Coyle et al. 2008) (Cold) (Warm) Pseudocalanus spp Acartia spp Centropagus abdominalis Calanus marshallae 0 (2.96) (8.13) Calanoid nauplii

23 July Zooplankton Biomass Figure courtesy of J. Napp / N. Shiga

24 Large zooplankton abundance (# per m3), Bongo Tow, 505 µm mesh net Hyperiids Neocalanus plumchrus & flemingeri Calanus marshallae

25 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

26 Abundance of Age-1 Pollock VS. Age-0 Abundance the prior year Age-1 recruitement (millions) Age-0 mean CPUE (# per haul) Updated from Moss et al., 2009

27 Diets of Age-0 Pollock in warm and cold years From Moss et al., 2009

28 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 (%) Year Figure courtesy of K Coyle, data from the NOAA BASIS Survey Program

29 Estimates of Calanus marshallae & Euphausiids Euphausiid backscatter Year Euphausiid data from P. Ressler; C. marshallae from J. Napp.

30 Age-0 Pollock Energy Content kj fish Jamal Moss unpublished data

31 Recruitment of Age-1 Pollock as a function of Energy Density of Age-0 fish Source: NPFMC 2011 SAFE, Dec 2010

32 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

33 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

34 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

35 Biomass of Arrowtooth Flounder on the Eastern Bering Sea Shelf Source: NPFMC 2011 SAFE, Dec 2010

36 Diets of Arrowtooth Flounder on the eastern Bering Sea Shelf Source: NPFMC 2011 SAFE, Dec 2010

37 Distribution and Area of Cold Pool in Warm and Cold Years Source: NPFMC 2011 SAFE, Dec 2010

38 Distribution and Abundance of walleye Pollock in Warm ( ) and cold ( ) Years Source: NPFMC 2011 SAFE, Dec 2010

39 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