1. Justin G. Mychek-Londer and David (Bo) Bunnell

2. Acknowledgements Great Lakes Fisheries Commission (GLFC) Great Lakes Restoration Initiative (GLRI) USGS Great Lakes Science Center My Advisors: Bo Bunnell, James Diana Vincent Belill, John French III, Melissa Kostich, Kevin Keeler, Mark Rogers, Lynn Ogilvie, Betsy Puchala, Linda Begnoche, Steven Pothoven, Chuck Madenjian, Bruce Davis, Dave Bennion, Greg Jacobs, Timothy DeSorcie, Barbara Diana, Scott Nelson, Jean Adams, Jeff Holuszko, Solomon David, and others I’ve forgotten. The Crew of the RV Grayling Ed Perry and Jim Paige Susie Q Commercial Fishery in Two Rivers, WI School of Natural Resources at The University of Michigan, Ann Arbor

3. Outline Laurentian Great Lakes Ecology in Lake Michigan My research Hypothesis testing Results Discussion Implications

4. Credit: COSEE Laurentian Great Lakes Glacial Colonization Human influence – Pollution – Exploitation – Extinctions – Habitats – Climate change – Invasive species Credit: COSEE

6. Non-natives Engineering: Canal systems Sea lamprey Alewife Introductions Brown trout Rainbow trout Smelt Alewife control – Chinook salmon – Coho salmon

7. Lake Michigan Within US territory Inshore and offshore Extinctions, extirpations Recent environmental change Offshore Ponto-caspian invaders Offshore native aquatic species

9. Prior to 1936 six named deepwater ciscoes Commercial Fishery Restoration Lake Michigan coregonid complex

10. CoregonidsSuperiorMichiganHuronErieOntario hoyi (bloater) XXXX reighardi (shortnose) X zenithicus (shortjaw) XXXX johannae (deepwater) X kiyi XXXX nigripinnis (blackfin) XXX WHITE = extinct, extirpated BLACK = present day RED = extirpated, restoration consideration

12. Quagga effects -Inshore and offshore -Span LMichigan basin -Estimates in trillions -Establish in sediments -Dreissenid biomass > prey fish Quagga mussels 200019952005 Ballasts: Ponto-caspian invertebrates Bythotrephes spp. Zebra mussels Quagga mussels

13. Ballasts: Round goby First found in St. Clair River (D. Jude, 1990) Now in all Great Lakes Benthic, wide diet – larger (>60 mm) molluscivores May outcompete natives for food and space May bioaccumulate toxins Concerns about impacts Migrate offshore in winter

15. Native invertebrate preyfish food Diporeia Mysis Copepods

16. Lake-wide biomass of prey fish time series Prey fish biomass has never been lower 2008: 94% decline from the peak in 1989 GLFC objective: 500-800 kt of planktivore biomass At 25 kt = 5% of objective at best Lake-wide biomass of prey fish in 2008

17. Slimy sculpin (Cottus cognatus) Since 1990, general Increasing trend Benthic No swim bladders Highly developed sensory Polygnous nest guarding males Live 7-9 years TL ~125mm Other studies have addressed egg predation

18. Adult bloater (> 120 mm) Age-0 bloater (< 120 mm) Coregonus hoyi Better lake trout food Sex ratio, survivial bottleneck 30 year cycle hypothesis Planktivore Max length ~ 275 mm, 12 YO

19. Deepwater sculpin (Myoxocephalus thompsonii) Round goby USGS long term trawl data by species X-axis = year Y-axis = Mean g/ha

20. Diet, Distribution Diporeia, Mysis – Most important for SS and DWS SS: copepods, eggs, cladocerans, diverse, adaptable DWS: fish eggs, copepods, less diverse RG: bivalve oriented, diverse in Great Lakes Distribution in deepwater benthic zones: RG new to system: Expected in Lake Michigan in winter based on Lake Erie SS and DWS depth segregation, SS 60-83, DWS past 90m (Madenjian and Bunnell, 2008)

21. (g/ha)

22. Hypotheses about benthivore diets 1)Within species prey specific diet proportions will vary significantly across time and sampling locations 2)Between sculpins diet overlap should be high, while between goby and sculpins overlap should be moderate 3)All 3 benthic predators eat bloater eggs - SS eat the most, most frequently

23. SLIMY SCULPIN DIETS MONTH TRFFSTBMSK 20092010200920102009201020092010 JANUARYXX FEBRUARYXX MARCHXX APRILXXXXXX MAY X XX DEEPWATER SCULPIN DIETS MONTH TRFFSTBMSK 20092010200920102009201020092010 JANUARYXX FEBRUARYXX MARCHXX X APRILX XXXXX MAY XXXX JUNE X ROUND GOBY DIETS MONTH TRFFSTBMSK 20092010200920102009201020092010 JANUARYXX FEBRUARYXX MARCHXX APRILXXXXXX MAY X X Methods Diet proportions SS=1016, DWS=699 RG=552 Sampled at FF, STB, TR, MSK depths 69-128m When Jan-May 2009–2010 Diet Proportions – Used dry weight proportions time/space effects analyses and diet overlap analyses

24. Analysis Hypothesis 1: time and space effects General linear models (GLM) Individual models built for single predator and single prey: Prey categories selected: accounted for > 88% of each predators overall diet proportions Sampling unit: Nets weighted by the number of fish within a net Time – Day of year (DOY): TR January only Space – Location (port): all samples

25. Analysis: Hypothesis two, Overlap Tested overlap between species within each port Schoener’s = 1 – 0.5(Σ│pxi - pyi│) pxi proportion of food category i used by species x pyi is the proportion of food category i used by species y C = Morista’s: overlap between species j and k pij = proportion resource i of total resources used by species j pik = proportion resource i of total resources used by species k nij = # of individuals of species j using resource category i nik = # of individuals of species k that use resource category i Nj and Nk = the total number of individuals of each species in the sample (Morista, 1959). Schoener’s and Morista’s

26. DNA analysis of fish eggs Hypothesis 3: Bloater eggs DNA analysis on viable fish eggs 10 analyzed per sample Known DNA – Bloater, SS, DWS, RG Bloater DWSSS RG

27. Results: For all fish sampled SS N=1016 DWS N=799 RG N=552

28. Space preyfactor predator SSDWSRG mysis depth0.3470.0710.061 port<0.001 year0.3310.8700.004 diporeia depth0.0390.024. port<0.001. year0.7600.240. fish eggs depth.0.201. port.0.017. year.0.477. limnocal depth0.041.. port<0.001.. year0.017.. senec depth0.188.. port0.015.. year0.418.. bival depth..0.148 port..0.074 year..<0.001 chironomids depth0.079.. port0.059.. year0.079.. ostra depth..0.051 port..0.016 year..0.069 Ports: all samples  N = Nets (Fish) SS = 45 (1016) DWS = 40 (699) RG = 36 (552) Alpha significance SS ≤ 0.010 DWS ≤ 0.017 RG ≤ 0.017  Many effects Results: space GLMs

29. TIME EFFECTS Day of year (DOY) TR only  N = nets (fish) SS=22 (468) DWS=19 (238) RG=18 (156)  Alpha set to: SS: 0.05/4 = ≤ 0.012 DWS: 0.05/3 = ≤ 0.017 RG: 0.05/2 = ≤ 0.025 Few effects Time preyfactor predator SSDWSRG Mysis depth 0.0100.0230.114 doy 0.1790.0420.516 year 0.1580.1910.506 diporeia depth 0.3200.004. doy 0.1640.032. year 0.5610.961. fish eggs depth.0.237. doy.0.936. year.0.271. limnocal depth 0.191.. doy 0.195.. year 0.155.. bival depth..0.621 doy..0.131 year..0.038 chironomids depth 0.842.. doy 0.019.. year 0.198..

30. Schoener’s = overlap between SS and DWS = 0.62 Morista’s = overlap between sculpins = 0.70 No overlap between goby and sculpins (0.41 vs. SS; 0.36 vs. DWS

31. Schoener’s: overlap between SS and DWS 0.62 Morista’s = no overlap between sculpins No overlap between RG, sculpins using either index

32. Results: Hypothesis two, overlap Values: 0 = no overlap 1 = perfect overlap ≥ 0.6 = overlap possible competition Overlap analysis using Schoener's portspeciesSSDWS FF SSXX DWS0.62X RG0.410.36 TR SSXX DWS0.38X RG0.120.11 STB SSXX DWS0.62X RG0.190.15

33. NMS supports diet overlap

34. RESULTS: Egg Genetics 85 bloater eggs February- May All four ports Eyed eggs 19 @April 17-20 14 @ May 1, 18 31 eggs in FF in APR 26 individual SS Apr 17, 20 th 66% consumed by SS 34% by DWS RG ate minimal eggs 0 0 0 0 0 0 0 Eyed bloater egg eaten by slimy sculpin

35. Summary for benthivore diets Hypothesis 1) space vs. time, within species – Diets did not vary through time – Diets differed across ports for all species Hypothesis 2) Diet overlap – Diet overlap did occur between sculpins – Goby diets did not overlap with any sculpin species Hypothesis 3) Bloater eggs – Most were consumed by slimy sculpin - true – DWS – also ate bloater eggs – true

36. Worth noting on diets: Space vs. time – Cover more space Without Diporeia – SS diets became broad – DWS turned almost completely to Mysis High egg cannibalism – Species coexistence RG impacts offshore on sculpin diets – minimal, perhaps minimal in offshore foodweb

37. Part II Determination of: – Gastric evacuation - digestion – Index of fullness – how much food in a sculpin stomach – Daily ration Use these estimates, empirical data and diet data to model – How many bloater eggs eaten in one day, by one slimy sculpin Scale up from an individual sculpin to: – to population and lakewide levels of annual bloater egg predation by sculpin Input data into recruitment models to determine if sculpins eat enough bloater eggs to limit bloater recruitment interannually – Can be done for other prey types hypothetically (i.e., Diporeia)

39. Approach Individual sculpin prey specific daily consumption Index of fullness and daily ration Gastric evacuation rate (GEVAC) Diets - now we know Population Level Daily Consumption Bloater Eggs Eaten Bloater Eggs Produced

40. GEVAC using live sculpins

41. GEVAC Digestion rate Two main hypotheses: – Vary by temperature – Vary by prey type Methods: – Fed known quantity of food w/known dry-weight – After 30 min, leftover food removed – Digest in chamber for 24, 48, 72, 120, 168 Hours – Euthanize, remove stomach, dry undigested prey – Quantify %dry-weight remaining → digestion rate

42. GEVAC results Slimy sculpin No variation – by temperature (panel a) – or prey type (panel b) – Very slow: temps

43. Deepwater sculpin – No variation by temperature GEVAC results

44. Index of fullness Used additional fish from our diet samples – 1) Dry fish in a drying tin – 2) Separately dry each fishes stomach contents Index of fullness – Definition: Dry weight of an individual fishes stomach contents divided by the dry weight of everything else making up the rest of the fish – Ratio, used in other studies – Larger fish, expect a lower ratio Three hypotheses for index of fullness – 1) Vary within species according to date sampled – 2) Vary within species according to location in Lake Michigan sampled – 3) Would be lower than when measured in 1976, due to ecological change

45. Index of fullness Results A) = SS B) = DWS FDW important No location effects! No temporal effects! (Jan-Apr) Max values HIGHER THAN 1976 !?

46. Daily Ration

47. Population level daily consumption USGS Trawl data = numbers of SS and bloater per hectare GIS: total hectares: in depth strata 5 to 115m = (SS/ha x #ha) = slimy population Daily ration of bloater eggs in individual SS diets by total SS population (> 40 mm) Bloater: numbers + fecundity = total bloater egg production

48. Individual Prey Specific Daily Consumption Individual Average Meal Size (Daily Ration) Gastric Evacuation Rate Diet Population Level Daily Consumption Bloater Eggs Eaten Bloater Eggs Produced Consumption modeling

49. Initial lakewide consumption modeling results for year 2010, done in 2010 Bloater egg production consumed = 40.7% Sensitivity analysis = 20-130*%

50. A closer, more recent look however….

51. Likewise does not seem to fit

52. Take homes 1) Diet proportions did not vary across time, but did vary across space 2) Overlap between sculpins, none between goby and sculpins 3) Gastric evacuation was slow, not affected by temps, prey type 4) Without Diporeia, slimy sculpin diets diversified, whereas deepwater sculpin consumed almost entirely one prey, Mysis

53. Take homes 5) Despite present differential site based availability, and steep declines in Diporeia abundance since 1976, index of fullness was similar across locations, and mostly higher in 2009-2010 6) Bloater and deepwater sculpin eggs were found in sculpin diets in high numbers, but this may not limit bloater recruitment – further research needs to address DWS recruitment limitation 7) Restoration Reintroduction of bloater into Lake Ontario may succeed if sculpins truly control recruitment of bloater through egg predation in Lake Michigan because slimy sculpin lakewide biomass in Lake Ontario is currently at low levels, and deepwater sculpin exists only marginally

54. Thanks: JGLonder@gmail.com