Status and Trends of the Lake Superior Fish Community,

Transcription

1

2 Status and Trends of the Lake Superior Fish Community, An Overview of the USGS Lake Superior Monitoring and Research Program Owen Gorman, Mark Vinson & Daniel Yule Lake Superior Biological Station Annual Meeting of the Wisconsin Land & Water Conservation Association Elkhart Lake, Wisconsin, Osthoff Resort March 2, 2016

3 Status and Trends of the Lake Superior Fish Community Lake Superior Biological Station Program R/V Kiyi R/V Siscowet

4 LSBS Program Early years ( ) emphasized gillnet and bottom trawl surveys focused on lake trout restoration and defining prey base (single species management paradigm) Middle years ( ) emphasized lake-wide bottom trawl monitoring to assess prey fish abundance for lake trout (fish community management paradigm) R/V Siscowet

5 LSBS Program Later years ( ) expanded trawl surveys to deepwater habitat to better describe the deepwater fish community (whole lake assessment) More recently ( ) application of hydroacoustics; provide more precise estimates of preyfish abundance useful for setting limits for harvest New studies in 2005-present integrated multiple sampling methodologies across habitats and trophic levels; increased knowledge of production and energy transfer via fish-mediated habitat coupling. Emphasis on ecosystem modeling and function (ecosystem restoration and management paradigm). R/V Kiyi

6 USGS Fisheries Science - Trawling

7 USGS Fisheries Science Hydroacoustics Zooplankton Neuston

8 Where to sample? What you catch depends on where you sample, and what you sample with. U.S. Geological Survey Lake Superior Biological Station 1957 to present Bottom trawls, 13,000 at 250 sites Gillnet sets, 2019 at 1,245 sites Mid-water trawls, 650 at 466 sites Hydroacoustic transects, >200

9 Offshore Sites Sampling Locations Nearshore sites sampled, annually Deepwater sites sampled 73 Offshore CSMI sites sampled 57

10 USGS Lake Superior Annual Fish Surveys ~120 sites per year, 84 nearshore, 36 offshore What s in the sample? How does it compare to previous years?, 75 days, 6,000 miles, 0.001% of the lake sampled Why is it different?

11 Lake Superior Depth Zones 0-15 m m >80 m >250 feet > 80 m depth (77% of surface area) Lake Superior is a Siscowet Lake! 80 m depth (23% of surface area)

12 cisco bloater kiyi rainbow smelt Photo by Owen Gorman shortjaw cisco Lake Superior Fishes lake whitefish Photo by Owen Gorman Photo by Owen Gorman siscowet lake trout Photo by Owen Gorman lean lake trout burbot Photo by Owen Gorman Sulpins: slimy, spoonhead, deepwater

13 Societal dilemmas Native vs. exotic communities: Lake trout, Ciscoes, Sculpins vs. Pacific salmon, Alewife, Smelt, Goby How did we get here? Where do we go from here? See Dettmers et al. (2012, 2014) and Claramunt and Clapp (2014) for a recent debate. 32% of articles cited by these papers written by GLSC scientists

14 Bloater chub fishery collapse in Lake Michigan; August 13, 2011 Salmon collapse hits Lake Huron hard and fast; December 7, 2014

15 Commercial yield of lake herring, rainbow smelt, and lake trout from Lake Superior, Harvest, 1000s of pounds Lake herring Smelt Lake trout LKT CPUE, No. fish / 1000 m / night Year 0 Data from are from Baldwin et al. (1979), data from are from Mattes (2004), LKT data from are from Wilberg et al. (2003)

16 Photo by Owen Gorman Photo by Owen Gorman Sea lamprey (introduced) Victim: hatchery lake trout

17 Lake Superior Success Story: Restoration of wild Lake Trout Shown are trends in mean relative density (fish/ha) of age-1 and older Lake Trout for all nearshore sampling stations in Lake Superior, Relative Density (fish / ha) Relative Density (fish / ha) Hatchery lake trout Year Wild (lean) lake trout Year < >400 < >400 Relative Density (fish / ha) Siscowet lake trout Year < >400

18 Lake Superior Fish Community: Trends in Relative Biomass, Relative Biomass (kg/ha) Other L. Whitefish Bloater Cisco R. Smelt All Lake Trout : 1.12 kg/ha - lowest biomass on record: 2012: 1.20 kg/ha Year 1983: 2.15 kg/ha

19 Relative Biomass (Kg/Ha) Trends in Lake Superior Nearshore Prey Fishes, Other L. Whitefish Bloater Cisco 52% 38% 21% 21% 16% 2.0 Smelt Interval Other R. Smelt Other Cisco Other Cisco L. Whitefish Cisco Bloater R. Smelt L. Whitefish Bloater R. Smelt L. Whitefish Bloater SJ Cisco SJ Cisco

20 Change in the Lake Superior Nearshore Fish Community Structure III cisco + bloater + wild lake trout I Factor smelt + hatchery lake trout + demersal spp. - lake whitefish II*. Reset Factor IV. 2015

21 USGS 12 Cisco Spring Bottom Trawl Assessment Lake Superior, Relative Biomass (kg/ha) Biomass Trends 10 Bloater Year Cisco Bloater Relative Biomass (kg/ha) Year

22 USGS Spring Bottom Trawl Assessment Lake Superior, Year Class Trends Cisco Bloater - possible 2015 year class?? Relative Density (fish/ha) Relative Density (fish/ha) Cisco Yearlings Bloater Yearlings Year-class Year-class??

23 Why the lack of Cisco recruitment? Change in predators are they being eaten? Change in their food supply are they starving? Environmental changes? Where is the bottleneck? Photo by National Geographic

24 Lake Superior Understanding cisco recruitment dynamics Lakewide, 2014: 19 billion, 787 / ha Lakewide, 2015: 35 billion, 1,459 / ha

25 2014 high ice cover, very slow spring warming 92% ice cover, 25 March 2014 Max ice cover % Photo from UW-Madison, Data from Canadian Ice Service 0

26 2015 high ice cover, plus spring warming? 68% ice cover, 25 March 2015 Warmer spring temperatures? Better growth? Better survival? Photo from UW-Madison, Data from Canadian Ice Service Max ice cover %

27 Conclusions- Nearshore Prey fish biomass has declined 84% since the early 1990 s Due largely to reduced abundance of cisco, bloater, whitefish, and smelt. Absence of strong cisco year class since Absence of strong bloater year class since 2005 Decline in year class sizes of smelt and lake whitefish since 2007

28 8.0 Lake Superior Deepwater Fish Community, nearshore offshore Deepwater Sculpin 5.0 Kg / Ha Bloater Siscowet Lake Trout Cisco Kiyi LN Sucker 0.0 Lean Lake Trout < >200 Depth Bin, meters Burbot

29 8.0 Lake Superior Deepwater Fish Community, nearshore offshore Kg / Ha Deepwater Sculpin Siscowet Lake Trout 2.0 Kiyi 1.0 Bloater L Whitefish Pygmy Whitefish Lean Lake Trout 0.0 Smelt < >200 Depth Bin, meters Burbot

30 Conclusions- Offshore Principal species: Siscowet, DW Sculpin, Kiyi; represents > 93% total biomass 3-5 times the biomass of Nearshore waters Deepwater biomass increased between and Increased biomass of kiyi: maturing 2003 year class Increased biomass of adult siscowet: maturity, growth Decreased biomass of deepwater sculpin: decreased density of adults,> 200 m; decreased density of all sizes <161 m depth

31 Conclusions Nearshore and offshore fish communities distinct Show different trends; biomass of nearshore community at lowest point in 35 years Offshore community more stable, much higher biomass Offshore community is the dominant community in Lake Superior; occupies ~77% of the lake by area, represents >90% of total fish biomass

32 Acknowledgments LSBS scientists (since 1957) Bill Dryer, Dick Pycha, J. Beil, J. Rahrer, Merle Bailey, Jim Selgeby, Chuck Bronte, Don Swedberg, Gary Curtis, Michael Hoff, Owen Gorman, Jason Stockwell, Daniel Yule, Mark Vinson R/V Kiyi crew, Joe Walters, Keith Peterson, Mike McCann, and Chuck Carrier USGS technicians Dan David, Joan Bratley, Gary Cholwek and Lori Evrard The many Northland College students that contributed to collection of fish, sample work up, and data entry since 1957! Supporting agencies and cooperators USGS USFWS USEPA Minnesota DNR Wisconsin DNR Michigan DNR OMNR DFO-Canada GLFC LSTC GLIFWC CORA etc.