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Summer 2010 collapse of the Lake Nipissing zooplankton community subsequent to the introduction of the invasive zooplankter Bythotrephes longimanus Jean-Marc.

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Presentation on theme: "Summer 2010 collapse of the Lake Nipissing zooplankton community subsequent to the introduction of the invasive zooplankter Bythotrephes longimanus Jean-Marc."— Presentation transcript:

1 Summer 2010 collapse of the Lake Nipissing zooplankton community subsequent to the introduction of the invasive zooplankter Bythotrephes longimanus Jean-Marc Filion A Lake Nipissing Partners in Conservation case study Correspondence address: 135 West Peninsula Rd, North Bay, ON P1B 8G4 lnpc.northbay@gmail.com April 4, 2012

2 2010 – Sampling Stations – Lake Nipissing S3 S6 S5 S8 S4 S2 S1 N Goose Is Manitou Is French River South Bay Sturgeon Falls North Bay Callander Bay 5 km Surface area 873 km 2 Average depth 4.5m5% of all Ontario angling

3 Horizontal strata sampling method Direction of travel Float Weight Net

4 Net being hauled horizontally 150 m at a depth of 1 m in this instance.

5 Depth data logger inserted in net to monitor depth of haul

6 Taking the animals out of the net, and washing them into a large, white, plastic tub

7 Samples, once concentrated with 80 micron filter

8 The Players

9 Young Adult Juvenile Time With each molt, an additional barb is added Bythotrephes longimanus barb

10 Large transparent predator – is out-competed by Bythotrephes longimanus

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14 GeotrichiaConochilus unicornis Blue green algae Colonial rotifer

15 Lake herring (Cisco) (Coregonus artedi) - to 18 inches approximately Yellow perch (Perca flavescens ) – to 12 inches approximately Rainbow smelt (Osmerus mordax) – to 8 inches approximately

16 Yellow walleye Stizostedion vitreum This fish was live-released

17 Results

18 2010 – Sampling Stations – Lake Nipissing S3 S6 S5 S8 S4 S2 S1 N Goose Is Manitou Is French River South Bay Sturgeon Falls North Bay Callander Bay 5 km

19 Population expansion Population crash 2010 an./m3

20 Population expansion Population crash

21 Bythotrephes eats zooplankton So what is the zooplankton population doing during this time?

22 S8 - Zooplankton abundance per date per stratum 2010 Relative scale

23 Relative scale S8 - Zooplankton abundance (averaged over the strata ) Population crash due to Bythotrephes predation 2010 Partial recovery later in the summer

24 Large Daphnia galeata mendotae population S8, May 30 th, 2010 in the 5m stratum

25 Mostly daphnia Mostly daphnia 100 Bythotrephes 3900 Bythotrephes 150 Bythotrephes 300 Bythotrephes 40 Bythotrephes 10 Bythotrephes

26 1900 Bythotrephes720 Bythotrephes 750 Bythotrephes 1000 Bythotrephes 170 Bythotrephes 400 Bythotrephes Fewer daphnia Zooplankton depleted in all strata June 13 June 20

27 3100 Bythotrephes 990 Bythotrephes 480 Bythotrephes By the end of June, the spiny water flea had pretty well eliminated most of the zooplankton in the water column

28 1500 60 150 Bythos 60 300 70 Bythos By July 11, 2010, Bythotrephes itself had crashed to much lower abundances. Only small remnant zooplankton populations remain over much of the lake.

29 S8 Results Aug. 7, 2010 Kevin O'Grady captures a 35 cm walleye with only Bythotrephes in its stomach. Aug. 13, 2010 Stéfane Filion captures a 30 cm walleye with only Bythotrephes in its stomach. Come August some harvestable walleye started consuming Bythotrephes Bythotrephes

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31 Food web implications walleye snails minnows insect larvae perch copepods cladocera herring smelt Energy flow Before introduction of Bythotrephes

32 Food web implications walleye snails minnows insect larvae perch copepods Cladocera herring smelt Energy flow After introduction of Bythotrephes Lost to sediments Nutrients may recycle in early fall - wind / shallow depths

33 Food web implications (before Bytho) walleye 1 kg perch 10 kg zooplankton 100 kg phytoplankton 1000 kg

34 Food web implications (after Bytho – no collapse) walleye 0.1 kg perch 1 kg Bytho 10 kg zooplankton 100 kg phytoplankton 1000 kg

35 Food web implications (after Bytho – after collapse) Energy flow constricted walleye 0.001 kg = 1 g perch 0.01 kg Bytho 10 kg * 1/100 0.1 kg zooplankton 100 kg phytoplankton 1000 kg

36 Fisheries management implications (present system) Healthy walleye pop + Healthy ecosystem Max. sustainable yield = 100,000 kg

37 Fisheries management implications (present system) Healthy walleye pop + Healthy ecosystem Max. sustainable yield = 100,000 kg Stressed walleye pop (harvest set at 2/3 of m.s.y.) = 66,000 kg

38 Fisheries management implications (present system) Healthy walleye pop + Healthy ecosystem Max. sustainable yield = 100,000 kg Stressed walleye pop (harvest set at 2/3 of m.s.y.) = 66,000 kg NFN gets 2 fish for every 1 fish sport fishery NFN harvest quota set at 44,000 kg Sport fishery quota set at 22,000 kg

39 Fisheries management implications (Energy flow restricted) Healthy walleye pop + Unhealthy ecosystem Max. sustainable yield = 50,000 kg (too high?)

40 Fisheries management implications (Energy flow restricted) Healthy walleye pop + Unhealthy ecosystem Max. sustainable yield = 50,000 kg Stressed walleye population (harvest set at 2/3 of m.s.y.) = 33,000 kg

41 Fisheries management implications (Energy flow restricted) Healthy walleye pop + Unhealthy ecosystem Max. sustainable yield = 50,000 kg Stressed walleye population (harvest set at 2/3 of m.s.y.) = 33,000 kg NFN gets 2 fish for every 1 fish sport fishery NFN harvest quota set at 22,000 kg Sport fishery quota set at 11,000 kg

42 Fisheries management implications (Energy flow restricted) NFN gets 2 fish for every 1 fish sport fishery NFN harvest quota 22,000 kg Sport fishery quota 11,000 kg 2011 harvest results NFN quota set at 40,000 kg or so Caught 21,000 kg

43 Fisheries management implications (Energy flow restricted) Healthy walleye pop + Unhealthy ecosystem Max. sustainable yield = 50,000 kg Very stressed walleye population (large walleye?) (harvest set at 1/3 of m.s.y.) = 17,000 kg ??? NFN gets 2 fish for every 1 fish sport fishery NFN harvest quota set at 11,000 kg Sport fishery quota set at 6,000 kg (Just one of many management options)

44 Fisheries management going forward We are at a critical point Doing nothing is the worst option We are out of time Nobody wants the take the medicine Need a plan and a way to sell it /implement it

45 Food web implications A number of problems may arise from the introduction of Bythotrephes. “We demonstrated that increases in trophic position of the magnitude reported here can lead to substantial increases in fish contaminant concentrations.” Bythotrephes invasion elevates trophic position of zooplankton and fish: implications for contaminant biomagnification Michael D. Rennie Angela L. Strecker Michelle E. Palmer Biol Invasions (2011) 13:2621–2634 DOI 10.1007/s10530-011-0081-0 Nineteen lakes studied, focused primarily on lake herring (Coregonus artedi)

46 Food web implications of the addition of smelt to the ecosystem “Rainbow smelt invasion may affect the accumulation of persistent lipophilic contaminants and heavy metals such as mercury in top predators.” Ecosystem effects of Rainbow Smelt (Osmerus mordax) invasions in inland lakes: A literature review Rebekah C. Rooney and Michael Paterson Canadian Technical Report of Fisheries and Aquatic Sciences 2845 (2009)

47 Children (to age 15) and women of child bearing age Walleye in this range must be released March 2011, MOE Guide to eating sport fish in Ontario. Consumption advice in the tables is based on an average meal size of 227 grams for an average size adult of 70 kilograms (154 pounds). Meals per month

48 Bow to the queen ! Want a copy of the full report? Jean-Marc Filion lnpc.northbay@gmail.com

49 S3 S6 S5 S8 S4 S2 S1 N Goose Is Manitou Is French River South Bay Sturgeon Falls North Bay Callander Bay 5 km Lake Nipissing Outlet – French River Headwaters S4 - Zooplankton community structure

50 S4 – A biodiversity refuge S4 is located in an area of crucial importance to Lake Nipissing as it serves as both a fish and zooplankton refuge, thus helping to preserve biodiversity. It is near the outlet of Lake Nipissing, which drains in a southwesterly direction via the French River. The bathymetry of this area is unusual in that a cold water refuge is available due to the deeper waters available in this location. The maximum depth that we were able to find using our Hummingbird depth sounder was 54m. In the summer this area becomes a cold water refuge for the lake herring (cisco) and the smelt. Warmer waters on top and oxygen depletion at depth keep the fish sandwiched in a definite band, as indicated by this picture taken of our Hummingbird sonar unit.

51 S4 0.5 km Depths in metres

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54 4 mm New Players Mysis relicta Chaoborus

55 Fish zone Something interesting may be going on at these depths Bythotrephes abundances correlate negatively with depth

56 Relative abundance Copepod abundances correlate positively with depth Something interesting may be occurring at these depths Fish zone

57 Relative scale (max is 30) Mostly D. pulicaria Fish zone Diaphanasoma birgei only collected in trace amounts and only in the 1m stratum Depth (m)

58 S4 - Relative abundances of Conochilus, Geotrichia and Ostracoda taxa vs depth Relative scale (max is 30) Depth (m)

59 Callander Bay S3 S6 S5 S8 S4 S2 S1 N Goose Is Manitou Is French River South Bay Sturgeon Falls North Bay Callander Bay 5 km S1 - Zooplankton community structure

60 0.5 km S1 Callander Bay

61 S1 - Callander Bay an./m3

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63 Relative scale In 2000/2001 Leptodora was quite abundant reaching abundances of over 100 an./m3 in mid-August. In 2010, Leptodora is only present in trace amounts in early July, and is not collected Aug. 1 st. S1- Leptodora kindtii S1 - 2010 140 14 1.4 0.14 an./m3 - mouth area of 0.5 m2 – 300 micron Nitex mesh. S1 - 2001

64 Relative scale By the end of the 1 st week of July Bythotrephes had driven Diaptomids at S1 to trace amounts. Historicaly abundances at this time were in the 15000 an./m3 range. By the 1 st of August the Diaptomids are recovering somewhat. S1- Diaptomids S1 - 2010

65 Relative scale By the end of the 1 st week of July Bythotrephes had driven Cyclops at S1 to trace amounts. Historically abundances at this time were in the 20000 to 40000 an./m3 range. By the 1 st of August the Cyclops are recovering somewhat. S1- Cyclops S1 - 2010

66 Relative scale By the end of the 1 st week of July Bythotrephes had driven Daphnia at S1 to trace amounts. Historically abundances at this time were variable but typically in the 5000 an./m3 range. In 2010, by the 1 st of August Daphnia were very abundant at depth. In 2001 only D. retrocurva was collected at S1. In 2010 only one D. retrocurva individual was collected, the rest being Daphnia galeata mendotae. S1- Daphnia S1 - 2010

67 Relative scale By the end of the first week of July 2010, Bythotrephes had pretty well eliminated the Bosmina sp. from Callander Bay. They remain absent from the collections on Aug. 1 st. In 2000/2001 their average abundances come July were in the 5000 to 20000 an./m3 range. The ‘U’ shaped curve from 2001 may imply that Bosmina may serve as a food source for juvenile and larval fish who move on to other prey as they reach a larger size. S1- Bosmina sp. S1 - 2010

68 Historically Diaphanasoma at S1 was a highly variable species, sometimes attaining abundances as high as 40000 an./m3, only to almost disappear from the collections the week after. Collections in 2000/01 were made using vertical hauls. This may imply horizontal patchiness. Populations were usually small at the beginning of July, but then increased to an average of 10000 an./m3 come the first of August. In 2010, Diaphanasoma was not collected on July 7 th, 2010 and showed little sign of becoming abundant on the 1 st of August. It was absent from the collections at the 8m stratum. Bythotrephes may be keeping this species at low abundance levels at S1. Relative scale S1- Diaphanasoma birgei S1 - 2010

69 S1 was sampled July 7 th and August 1 st, 2010. Holopedium gibberum was only collected in trace amounts from the 5m stratum on July 7 th. Historically, Holopedium had average abundances of around 100 an./m3 in early July and early August. It would seem that Holopedium disappears quicker and attains lower maximum abundances since the introduction of Bythotrephes. S1 – Holopedium gibberum

70 Relative scale Conochilus unicornis and Geotrichia, not collected in any important amount in 2000/01 is now becoming common to moderately abundant as summer progresses at S1.

71 In the winter perch turn to eating snails and mayfly naiads. They could do the same in the summer.


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