American eels in the Hudson River estuary: from glass to silver

Transcription

1 American eels in the Hudson River estuary: from glass to silver Karin E. Limburg, SUNY ESF Chris Bowser, Sarah Mount Hudson River National Estuarine Research Res. NYSDEC Hudson River Estuary Program Bob Schmidt (in absentia)

2 Outline of today s talk: General biology of eel (emphasis on ) Quick summary of previous HR eel studies Current HR eel studies Glass Yellow Silver Evolution from study object to a river icon that brings people together

3 Freshwater eels are catadromous born at sea, can migrate into estuaries, rivers, streams, lakes even stay at sea Eels have a complex set of life stages: Larvae specialized to drift, called leptocephali (pl.) Transform in estuaries into transparent glass eels Develop yellow-brown pigmentation called elvers bootlace eels yellow phase silver (maturing, migrating back to sea)

4 It wasn t until an enterprising Dane, Johannes Schmidt, began a long-term examination of fisheries collections that we understood the life cycle of eels. Beginning in 194, Schmidt received grants from the Danish queen to send out ships into the middle of the Atlantic, to collect fish larvae. The further the ships went into the heart of the Atlantic, the smaller the leptocephali. Finally, in 1922, the smallest larvae were collected south of Bermuda in the Sargasso Sea the mysterious part of the Atlantic with depths over 5, meters.

5 Source: Maryland Sea Grant

6 American eel leptocephali Source: Uwe Kils, Rutgers University

7 Tesch, 1977

8 Glass eels swim up estuaries in droves Source: Glooskap and the Frog Capable of climbing vertical surfaces capillary action - glass walls of old Now, heavily exploited fishery

9 Yellow eels (growth phase) can live in a wide variety of habitats varied diets (leads to morphological variation their skulls) growth rates highly variable accumulate fat for the long migration back to Sargasso

10 Source: van Ginneken & van Theillart, U. Leiden As eels become ready to migrate to the Sargasso, they become silvery and their eyes enlarge cease feeding Pankhurst s index = a measure of eye size (a maturation index)

11 American eel life history DFO Canada Scientific American

12 Length (cm) Early HR eel studies Hudson River yellow eel study W. Morrison & D. Secor, U. MD ALBANY ATHENS Age vs length Gwb Hav New King Ath Alb KINGSTON NEWBURGH salt front HAVERSTRAW Age (years) G.W. BRIDGE 2 km Hugely variable growth rates!

13 Example of variable growth seen in eel otoliths Estuarine growth (fast) Kingston eel#36, length = 45 cm GWB eel#33, length = 49 cm Hudson River km 2 Hudson River km 145 Upriver/tributary growth Source: Wendy Morrison, U. MD

14 Hudson River tributaries study 23-4 the first, featuring Leonard Machut (ESF M.Sc.)

15 Natural and artificial barriers act as filters that reduce the numbers of eels upstream

16 The Glass Eel Story, or The Young and the Wiggly

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18 Albany The Hudson River Glass Eel Project Spans 15 miles of tidal estuary from Staten Island (salt) to near Albany (fresh) Variety of methods, sites, and audiences Springtime focus on YOY/glass eels/elvers NYC

19 Using fyke nets to monitor glass eels Each spring, nets are placed in the mouths of streams Teams of trained volunteers catch, count, and release eels Project follows ASMFC methods

20 45,+ juvenile eels caught & released above barriers since volunteers at 12 sites in 216

21 16, 14, Total glass eel catch for all sites , 1, , 6, 4, ,

22 Average Eels Caught Per Day Per Year

23 Average Glass Eels/Day at Furnace Brook Albany NYC

24 Average Glass Eels/Day at Fall Kill Albany NYC

25 Average Glass Eels/Day at Fall Kill Albany Furnace Brook range: glass eels/day NYC

26 Number of glass eels per collection period (approx. 24 hours) Albany /25 4/4 4/14 4/24 5/4 5/14 5/24 NYC 4/14

27 2 Number of glass eels per collection period (approx. 24 hours) Albany Minisceongo Creek 4 4/21 3/25 4/4 4/14 4/24 5/4 5/14 5/24 NYC 4/14

28 2 Number of glass eels per collection period (approx. 24 hours) Albany /4 Richmond Creek Minisceongo Creek Crum Elbow Creek 4 4/21 3/25 4/4 4/14 4/24 5/4 5/14 5/24 NYC 4/14

29 # eels per day In 214 we tracked the speed of glass eels upriver 2 Albany /1 5/6 Richmond Creek Minisceongo Creek Crum Elbow Creek Saw Kill 4 4/ /25 4/4 4/14 4/24 5/4 5/14 5/24 Date, 214 NYC 4/14 29

30 Eel Mop at Saw Mill River

31 Eel-evators to get eels past dams (May-Oct)

32 # Eels caught at Furnace Brook Ladder in 211 & 212 (sampling season May through October) < >3 Eel lengths in centimeters

33 Assessing Provenance and Maturity Status of Hudson River Eels

34 Yellow phase HR eels: Provenance studies using otolith chemistry An eel otolith (Photo: L. Machut) Artificial tag

35 Otoliths ( ear-stones )

36 An eel otolith (11-12 yrs old) Here, we show results of analyzing the outermost 1 microns of material for 7 element/calcium ratios + 26/24 Mg isotopes next slide

37 Canonical Discriminant Analysis of 53 eels Plot of Can2*Can1$Tributary. Symbol used is '*'. ƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒ Can2 4 ˆ ˆ * Indian Kill Indian Kill Black Creek * 2 ˆ * * Crum Elbow Kill Black Creek * ˆ Crum ElbownKill Kil** *rum Elbow Kill Indian Kil* * *Indian Kill Indian Fal* *illin*ian*kvlockie IK Kill BC Crum Elbow*Killn*Cru*KEl*ow Kill Crum Elbow Kill***aVlocill*K*lC*um CE Elbow Kill Black Creek * ˆ Fall Crum *lbowvlo*l*ecrumlelbow Kill * Vlockie Kill ˆ Fall Kill** Indi*n **Crum Elbow K*lVlockie Kill FK VK Fall Kill*Indian*Kill * Black *reek Fall*KFall*Kill Vlockie Kill * Fall Kill Fall*Kill * Minisceongo Creek Minisceongo*Creek -2 ˆ Minisceon*oMinieceongo Creek ˆ Crum Elbow Kill * MC * Minisceongo Creek * Fall Kill * Minisceongo Creek * Minisceongo Creek -4 ˆ ˆ ŠƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒŒ (Apologies for SAS output!) Can1 NOTE: 1 obs hidden. 63 label characters hidden.

38 All 53 eels were correctly classified to the tributary where they were captured From Tributary Number of Observations and Percent Classified into Tributary Black Creek Black Creek 4 1% Crum Elbow Kill. Fall Kill. Indian Kill. Minisceongo Creek. Vlockie Kill. Total Crum Elbow Kill. 13 1% Fall Kill % Indian Kill % Minisceongo Creek % Vlockie Kill % Priors Total %

39 Silver Eel Studies Photos: Dave Yozzo

40 1. American eels (Anguilla rostrata) hatch here

41 Tagging adult eels Béguer-Pon et al. 215

42 Béguer-Pon et al. 215

43 Silver eel research Goals: Better understand transition from yellow (resident) to silver (migratory) Develop a non-lethal index of maturity for American eels that can be used by researchers and managers Why? To easily assess eel productivity in the field based on quantitative measures

44 Albany Methods Electrofishing NYC NYC Fyke netting

45 External measurements ( 25cm) Total length Wet weight Horizontal and vertical eye diameter Head length Head width Pectoral fin length Body depth

46 Total length, mm Clusters by size SilverF SilverM Yellow YellowF Maturity class ± S.E.

47 Pankhusrt eye index Clusters by eye and fin index SilverF SilverM Yellow YellowF Pankhurst eye index separates eels into mature (silver) or immature (yellow) Threshold = 6.5 Mature eels have higher eye index, above threshold

48 Pectoral fin index Pankhusrt eye index Clusters by eye and fin index SilverF SilverM Yellow YellowF Pankhurst eye index separates eels into mature (silver) or immature (yellow) Threshold = 6.5 Mature eels have higher eye index, above threshold SilverF SilverM Yellow YellowF Fin index also significantly different between silver and yellow eels

49 Actual maturity stage Discriminant analysis Correctly classify individuals 83% of the time overall Predicted maturity stage SilverF SilverM1 SilverM2 Yellow1 SilverF 13 87% % % % SilverM1 % SilverM2 % Yellow1 % Yellow2 % YellowF % YellowF2 % 17 94% % 1.5% 1 2.4% % % % 17 85% 2 1% % % % % % 16 8% 2 4.8% % % Yellow2 YellowF1 YellowF2 Total 2 15 % % 13.33% % 3 15% % 46 94% % % % % % % 12 71% % % % % % % 7 88%

50 Albany Mark-Recapture on the Indian Kill So far we ve: Tagged 347 eels Recaptured 11 eels at least once Methods allow us to investigate: Growth (~1 cm/year) Movement (62% don t move) Maturity NYC

51 Albany Data Story of Eel Maturity July, 214 4x4 mm eye diameter 14 mm fin length Marsh NYC

52 Albany Data Story of Eel Maturity October, 214 6x6 mm eye diameter 17 mm fin length July, 214 4x4 mm eye diameter 14 mm fin length Marsh NYC

53 Albany Data Story of Eel Maturity October, 214 6x6 mm eye diameter 17 mm fin length July, 214 4x4 mm eye diameter 14 mm fin length NYC Marsh Heading to the Sargasso!

54 % eels caught Timing of maturity clusters Jul 213 Aug 213 Sep 213 Fyke 213 Jul 214 Aug 214 Sep 214 Fyke 214 SilverF SilverM Yellow

55 Summary of silver eel research Research tools important in future studies Non-lethal maturity index has fairly high classification rates Could be used in future studies to: Assess eel productivity how many mature eels out of total numbers Paired with data on other life stages, could calculate survivorship from one life stage to the next Compare maturity breakdown in different habitat types

56 Respect Your Elvers! Evolution from study object to a river icon that brings people together

57 Respect Your Elvers! Evolution from study object to a river icon that brings people together and reconnects waters

58 Respect Your Elvers! Evolution from study object to a river icon that brings people together and reconnects waters

59 Working with students and volunteers!

60 There is life At against first, I all only odds did in it places for extra where credit, you would think there is nothing. Interesting opportunities exist in the scientific but then I realized it was really cool! community for amateur naturalists to make a contribution. --Poughkeepsie --volunteer High Eva Schadeck School student

61 Thank you for listening! Bob Schmidt Thank you, HRF, NYSDEC, and especially Cara Ewell Hodkin and Kayla Smith for helping with oto-analyses

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64 External cluster analysis 983 individuals total Separated into 7 significantly different clusters

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66 Using fyke nets to monitor glass eels Each spring, nets are placed in the mouths of streams Teams of trained volunteers catch, count, and release eels Project follows ASMFC methods