Predator models

Sarah Gaichas, NEFSC Herring MSE workshop #2 December 7-8, 2016 Herring’s role as forage: summary Predator Class Consumption of Dependence on herring herring as prey Groundfish Highest Moderate-low Marine mammals Intermediate Moderate-low Humans () Intermediate High / Lowest High* Birds Lowest Moderate-high

Predators in the Northeast US have many prey options. Herring is a high energy option which migrates seasonally throughout the shelf. Herring prey on zooplankton, which also vary.

*Herring size may be more important than herring abundance Groundfish Status relative to Herring MSE design predator Bmsy, abundance, model condition Status relative to Tuna predator Bmsy, abundance, model Herring N at age, condition Herring operating Weight at age, model Unfished N at age Bird predator Reproductive model success

Whale Abundance, predator Stock status condition model (Error added to Herring surplus operating model production, status output) relative to Bmsy, condition Alternative Alternative Herring control rules allowable catches Herring catch

Economic Herring and interactions fishery model revenues & profits Models, uncertainty, and complexity

Aydin’s Modelling Yield Curve “Realist”

Insights gained Insights “Non believer” “Believer” Belief in model Summary

Predator and overlap Modeled herring relationship • Tuna  Herring average weight Forage throughout North affects tuna growth Atlantic, seasonally in GOM • Terns  Herring total biomass Forage seasonally near island affects tern reproductive breeding colonies in GOM success (productivity) • Groundfish  Herring total abundance Forage through same range as affects dogfish survival herring most of the year • Marine mammals  model Tuna Herring condition biomass

0.0230 Herring size, 0.0225“The decline in bluefin tuna condition, Gulf of Maine 0.0220despite high prey biomass in the Gulf of 0.0215Maine, suggests that managing for high 0.0210abundance at middle trophic levels does 0.0205 0.0200not guarantee the success of all top

GrowthIntercept 0.0195predators. In fact, it suggests that for 0.0190some upper level predators, the quality 0.0185of the prey may be more important than 0.0180 the 0overall0.05 abundance.”0.1 0.15 0.2 0.25 0.3 Herring Avg Wt Tuna Biomass

Tuna Numbers

Tuna Average Weight

0.0230 0.0225 0.0220 0.0215 0.0210 0.0205 0.0200 0.0195 GrowthIntercept 0.0190 0.0185 0.0180 0 0.1 0.2 0.3 Herring Avg Wt

MAP OF REGION AND COLONIES

1.10 Herring  1.08 1.06 1.04 Common tern 1.02 1.00 0.98 0.96

0.94 PredatorRecruitMultiplier 0.92 0.90 0 500000 1000000 1500000 2000000 2500000 Herring Abundance

Top groundfish predators of herring 100 90 80 70 60 50 40 30 20 10

0

1976 1989 1973 1974 1975 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

100 90 80 70 60 50 40 30 20 10

0

1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

0.100 Herring  0.090 0.080 0.070 Dogfish 0.060 0.050 0.040 0.030 0.020

PredatorAnnualNatural Mortality 0.010 0.000 0 1000000 2000000 3000000 4000000 5000000 6000000 Herring Abundance

Simulated dogfish with Simulated dogfish with no fishing

Mass balance food web model parameters

System of linear equations For each group, i, specify: Biomass (B) [or Ecotrophic Efficiency (EE)] Population growth rate (P/B) Consumption (Q/B) Diet composition (DC) Fishery catch (C) Biomass accumulation (BA) Im/emigration (IM and EM) Solving for EE [or B] for each group

 P    Q   Bi   * EE i  IM i  BAi  B j *   * DCij   EM i  Ci  B i j   B  j  Data uncertainty rating  distributions for parameters

Good

OK

Bad

Ugly Incorporating uncertainty

50

45

40

35

30

25

20

15

10

5

0 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49

20 Perturbation: change in survival for one group 10 ...... 0

-10

basebiomass -20 % change from from change %

Effects on each group in the food web Increase GOM herring survival 10%

High uncertainty Herring up Groundfish Marine mammals 10% increase in production

No change in production

Other forage down Decrease biomass 50% GOM herring Proportional Difference from Base

−0.5 0.0 0.5 1.0 1.5 2.0

Phytoplankton−Primary Producers

Bacteria High uncertainty Microzooplankton Small Large Copepods Gelatinous Zooplankton Micronekton Macrobenthos−polychaetes Macrobenthos− Macrobenthos−molluscs Macrobenthos−other

Megabenthos−filterers vul, herr Megabenthos−other Species

Shrimp_etc ing do Larval−juv − all wn 50%, B Small Pelagics− commercial Small Pelagics− other Small Pelagics− Small Pelagics− anadromous Medium Pelagics− (piscivores & other) Demersals− benthivores Demersals− omnivores Demersals− piscivores − pelagics HMS Pinnipeds Baleen Odontocetes Birds Is forage quality changing?

Beyond Biomass Is forage quality changing?

Slide courtesy Tim Sheehan, NEFSC Possible improvements?

• Consider multiple forage species of a predator together or “forage base” as a whole • Consider integrated two way feedbacks between predators and prey where possible • Consider changes in forage quality