Ministry of Natural Resources

Estimating the critical reproductive periods of lake sturgeon (Acipenser fulvescens) using daily water temperature unitsMike Friday Technical Note TN-48

Figure 1A and 1B. Example of a newly hatched “yolk-sac” larva (A) and a fully developed larva (B).

Index

Introduction .................................................... 1

Section 1. How the model was developed ...................................................... 2

Methods ...................................................... 2

Determining spawning dates .................... 2

Determining period of larval drift ............. 2

Water temperature ..................................... 3

Cumulative temperature units ................... 3

Results ......................................................... 3

First spawning date and start of larval drift ..................................................... 3

First spawning date and end of larval drift ..................................................... 3

Discussion ................................................... 3

Section 2. How to use the model ................. 4

Water temperature ..................................... 4

Predicting first spawning ............................ 4

Predicting duration of drift ........................ 4

Section 3. A practical trial of the CTU model ..................................................... 4

Methods ...................................................... 4

Water temperature ..................................... 4

Spawning date prediction ......................... 4

Drift netting ................................................. 4

Testing predictions ..................................... 4

Results ......................................................... 5

Drift netting ................................................. 5

Model predictions ...................................... 5

Discussion ................................................... 5

Recommendations ......................................... 6

Acknowledgments ......................................... 6

Literature cited ............................................... 7

IntroductionLake sturgeon (Acipenser fulvescens) are a fluvial dependant species as they are found in a variety of habitats, but require flowing water (typically mainstream river systems) during all or part of their life cycle. This species may have significant lake, reservoir, or estuary populations, but the use of tributary streams or rivers is essential for a portion of their life history (Galat and Zweimuller 2001). Spawning takes place in the high-gradient, fast flowing reaches of large rivers over coarse gravel or cobble substrates and at least two separate spawning events during a spawning season are common (Kempinger 1988, Bruch and Binkowski 2002, Smith and King 2005). Multiple annual spawning events have been documented in the Kaministiquia River with spawning occurring at temperatures of approximately 13 °C (mid to late May) and then again at 16 °C (timing variable, up to late June) (Friday 2004, 2005).

Newly hatched “yolk-sac” larvae (9 – 12 mm) are an underdeveloped, burrowing form (Figure 1A) and swim about in search of suitable cover within the interstitial spaces of the rocky substrates where they were spawned (Harkness and Dymond 1961, Kempinger 1988). After yolk sac absorption, the fully developed larvae (16 – 24 mm) (Figure 1B) emerge from the substrate at night and rapidly disperse downstream, often drifting for several kilometres before settling on the river bottom to begin exogenous feeding (Kempinger 1988, LaHaye et al. 1992). Larval drift is not uniform in time or space and the larvae can be found at varying distances from spawning sites, across the width of the river channel, and throughout the water column (Auer and Baker 2002, Friday 2009, Smith and King 2005).

Successful spawning largely depends on the timing, magnitude, and duration of spring freshet and water temperature regimes. Hydroelectric facilities can alter the natural hydrograph and flow regimes of a river impacting the ability of adult sturgeon to access spawning habitat, deposit eggs in suitable substrate, and may negatively influence incubation, hatch, and larval drift (Auer 1996, Friday 2007, Haxton and Findlay 2009).

A B

Science and Research Branch

Technical Note TN-48

Biodiversity and Monitoring

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The relationship between water temperature and lake sturgeon reproductive ecology is an important environmental connection that is applicable to the development of water management plans, and waterpower exemption agreements under the Endangered Species Act, mitigating the operational effects on lake sturgeon reproduction at existing hydroelectric facilities or collecting baseline data for new waterpower projects.

This technical note describes the use of cumulative water temperature units (CTU) to predict the start and duration of lake sturgeon larval drift. To define this period, we applied Kempinger’s (1988) equation (Appendix 1) to drift data collected on the Kaministiquia River from 2004 to 2012. Using the date of spawning as a starting point, we quantified the effect of water temperature on the timing and duration of larval drift by calculating accumulated CTU. Section 1 of this technical note presents the field and analytical techniques that were used to develop the model. Section 2 describes how to use the model. Section 3 presents the results of a practical trial of the model carried out on the Kaministiquia River in 2013.

Section 1. How the model was developed

MethodsDetermining spawning datesFrom 2004 to 2012, adult lake sturgeon were captured in the Kaministiquia River, fitted with external radio transmitters, and tracked as they moved to and from the spawning site at the base of Kakabeka Falls. A stationary data logger, situated on shore, was used to detect transmitters and record fish movement. On the date when groups of radio-tagged sturgeon (at least two fish) left the spawning site, a spawning event was presumed to have occurred (eggs deposited). This is typical spawning behavior (Harkness and Dymond 1961, Kempinger 1988), and was also verified in 2012 through visual observations of spawning adults, egg collections (by the author), and corresponding telemetry data.

Determining period of larval driftFrom 2004 to 2012 the period of larval drift was determined by setting drift nets overnight to collect larvae as they drifted downstream from the spawning site. Drift netting took place approximately 400 m downstream of Kakabeka Falls on the east shore of the river. Stainless steel, D-shaped drift nets were used that measured 0.76 m across the base, 0.53 m high, and had a 3.6 m tapered, knotless, nylon mesh bag (700 µm)

that terminated at a detachable collection container with filtering holes covered by 1,000 µm nitex mesh. Drift nets were positioned in the current and held in place with a 4.5 kg fishing anchor connected to the three point bridle of each net frame (Figure 2A). To sample the catch (daily), the cod end was lifted from the water, the collection container was detached, and the contents emptied into a shallow white pan for examination (Figure 2B). All sturgeon were removed, counted, and measured. Live sturgeons were released downstream.

Figure 2A and 2B. Drift nets deployed downstream of Kakabeka Falls (A) and emptying the collection container (B).

A

B

Water temperatureWater temperature, during the spawning and drift period (April to August), was recorded hourly approximately 400 m downstream of Kakabeka Falls, using a data logger.

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Biodiversity and Monitoring

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Cumulative temperature unitsUsing Kempinger’s equation, we calculated the CTU necessary for the following time periods, during lake sturgeon reproduction:

1. The start of larval drift, from the date of first spawning.

2. The end of all larval drift, from the date of first and any subsequent spawning events.

ResultsFirst spawning date and start of larval driftThe first spawning event was documented in each of the study years (n = 9) and occurred from May 14 to June 7. The mean daily water temperature on the date of spawning was 13.4 °C and drift of fully developed larvae (Figure 1B) commenced 10 to 21 days later (June 1 to June 26). The mean CTU value from the date of first spawning to the start of larval drift was 149.4 (95% CL: ± 3.6) (range 131 – 163) (Table 1, Figure 3).

First spawning date and end of larval driftFrom the date of first spawning to the end of all larval drift, took an average of 37 days (range 22 to 61 d) and drift of all larvae was complete from June 10 to July 20 (Table 1). The mean CTU value from first spawning event (n = 9) to the end of all drift was 398.6 (95% CL: ± 35.0) (range 299 – 571) (Table 1, Figure 3).

Table 1. First spawning dates, duration of larval drift and accumulated CTU values.

Year Date of first spawn

Start of drift period

End of drift

period

Days from first spawn to the end of drift

(CTU)2004 21-May 10-June 20-July 61 (571)2005 21-May 07-June 25-June 36 (376)2006 21-May 01-June 16-June 27 (333)2007 24-May 07-June 19-June 27 (328)2008 07-June 26-June 13-July 37 (352)2009 21-May 15-June 03-July 44 (352)2010 19-May 29-May 10-June 22 (299)2011 19-May 04-June 28-June 41 (405)2012 14-May n/a (see note) 06-July 55 (560)2013 31-May 16-June 05-July 36 (411)

Note: The start of larval drift could not be determined in 2012 due to high water conditions which prevented drift netting.

Figure 3. The CTU values from first spawning events to the start (blue circle) and end of all larval drift (red triangle).

Year

Cum

ulat

ive

tem

pera

ture

uni

ts

20030

50100150200250300350400450500550600

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

First spawn to start of drift First spawn to end of all drift

DiscussionThe mean CTU value from spawning to the start of larval drift (149.4) is consistent with the mean CTU value reported by Smith and King (2005) in the Upper Black River, Michigan (CTU = 151.2). The low variability in our data (CV = 5%) suggests the methods for determining the date of spawning is precise, and that development from egg to larvae is water temperature dependant. Temperature dependant development of lake sturgeon eggs has also been documented by Kempinger (1988) in the Wolf River, Wisconsin, and Wang et al. (1985) under laboratory conditions.

The mean CTU value for the time period from spawning to the end of larval drift (398.6) was more variable (CV = 24%), as evidenced by the high CTU values documented in 2004 (571) and 2012 (560), and the corresponding range in days that this CTU range translates to (36 – 61 d) (Table 1). In 2004, a late, second spawning event was documented (June 27), which resulted in larval drift that ended in late July (Friday 2004). In 2012, based on water temperature and larval drift that ended on July 7, we suspect that a second spawning event occurred on June 15 (14.4 °C), which resulted in a high CTU value to the end of drift. In all other years, when second spawning events were documented, they occurred early in June, resulting in earlier drift periods and lower CTU values (Friday unbl. data). Kempinger (1988) documented the days between multiple spawning events on the Wolf River, Wisconsin between 12 and 21 days.

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Biodiversity and Monitoring

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Water temperature is an important environmental factor that has a direct effect on the timing of spawning, embryonic development, and the period of larval drift. In managed systems, where lake sturgeon populations exist, water temperature data can be easily collected and used to predict the timing of these key life-history parameters. With these ecological periods defined, operational provisions at hydropower and other water control facilities can be developed to ensure successful reproduction.

Section 2. How to use the modelTo estimate lake sturgeon spawning dates and the period of larval drift the following procedures can be used:

Step 1: Water temperatureMean daily water temperature data is required from May 1 to July 31 using a continuous temperature data logger.

Step 2: Predicting first spawningUsing water temperatureInitial spawning will occur when water temperatures are between 11 and 13 °C, typically after May 1.

Using drift data and CTUTo determine the date of spawning, when the period of lake sturgeon larval drift has been sampled (drift netting data), simply back calculate CTU from the date when the first larvae was captured to the date when 150 CTU is reached.

Step 3: Predicting duration of driftIf the date of spawning is known (from visual observations, eggs collections, telemetry data, etc.) or has been approximated from known spawning temperatures, larval drift will commence after 150 CTU have accumulated (from the date of spawning) and in most years will be complete when 400 CTU is reached.

Section 3. A practical trial of the CTU modelIn 2013, the model was tested using water temperature and drift netting data from the Kaministiquia River and the procedures outlined in this technical note.

MethodsWater temperatureHourly water temperature data was collected from May 1 to July 31 using a continuous temperature data logger.

Spawning date predictionBased on daily analysis of water temperature data and a mean daily spawning temperature requirement of 13 °C, the predicted date of initial spawning was May 31, 2013. This was the first day when water temperature increased beyond 13 °C (Figure 4).

Figure 4. The 2013 predicted date of spawning (May 31) in relation to water temperature spawning requirement (13 °C).

Date

Wat

er te

mpe

ratu

re °

C

Predicted spawning temperature (13°C)

Spawning date

01-M

ay04

-May

07-M

ay10

-May

13-M

ay16

-May

19-M

ay22

-May

25-M

ay28

-May

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ay03

-Jun

06-J

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Drift nettingThe predicted date of spawning and period of larval drift was verified by setting drift nets to collect fully developed larvae (Figure 1B) as they drifted downstream from the spawning site. To ensure the entire drift period was sampled, drift nets were set when approximately 100 CTU had accumulated (on June 10) from the predicted date of spawning (May 31), and were removed from the water when larvae were no longer being captured (July 6). Two weekend days were not sampled (June 30 and July 1).

Testing predictionsWater temperature and drift data were used to test the model predictions. To determine the spawning date, CTU were back calculated from the date when the first larva was captured (June 17) to the date when approximately 150 CTU had accumulated. To estimate the end of all larval drift (from the predicted spawning date (May 31)), CTU were calculated forward to the date when approximately 400 CTU was reached (July 5).

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ResultsDrift nettingDuring 24 overnight sampling events (June 10 to July 6), 4,912 fully developed lake sturgeon larvae were captured (Figure 5). Prior to the start of larval drift, six newly hatched, underdeveloped “yolk-sac” larvae (10 – 12 mm) were captured on June 11 after 95 CTU had accumulated from the date of spawning (Table 2, Figure 5). The first fully developed larval sturgeon (15 mm) was captured on June 16, 16 days after the predicted spawning date (May 31) and 151.2 CTU. The duration of the downstream movement of larvae from the spawning site was 20 days (June 16 to July 5), and 411.4 CTU from May 31 (Table 2).

Figure 5. The 2013 catch of yolk-sac larvae (black bar), fully developed larvae (red bars) and predicted start (June 16) and end of larval drift (July 4) and associated CTU requirements.

Cum

ulat

ive

tem

pera

ture

uni

ts

yolk sac larvae

Predicted drift start (150 CTU)

Predicted drift end (400 CTU)

31-M

ay02

-Jun

04-J

un06

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Num

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Accumulated CTULarval catch

Model predictionsWhen CTU were back calculated from the date when the first larvae were captured, a value of 151.2 CTU was obtained on May 31 (Figure 5). When CTU were calculated forward from May 31, 411.4 CTU had accumulated when drift ended (July 5) (Figure 5).

DiscussionDuring the 2013 drift netting, a small number of underdeveloped, yolk-sac larvae (n = 6) (Figure 1A) were collected prior to the drift of fully developed larvae (Figure 1B). In 2004 and 2009, yolk-sac larvae were also captured prior to the drift of fully formed larvae (Friday 2004 and 2009). Field staff should be aware that under certain conditions, such as high flows, some newly hatched yolk-sac larvae may not burrow into the substrate and be swept downstream into the drift nets. This, however, does not signify the starting point of drift for this model.

Table 2. Water temperature, CTU and larval drift catch in the Kaministiquia River, 2013.

Date Mean daily water

temperature °C

K X i - K CTU accumulation

Larval catch

31-May 13.2 5.8 7.4 7.4

1-June 12.6 5.8 6.8 14.2

2-June 12.0 5.8 6.2 20.4

3-June 11.8 5.8 6.0 26.4

4-June 12.5 5.8 6.7 33.1

5-June 13.1 5.8 7.3 40.4

6-June 13.3 5.8 7.5 47.9

7-June 14.1 5.8 8.3 56.2

8-June 15.3 5.8 9.5 65.7

9-June 15.7 5.8 9.9 75.6

10-June 15.5 5.8 9.7 85.3

11-June 15.5 5.8 9.7 95.0 6

12-June 13.5 5.8 7.7 102.7 0

13-June 17.7 5.8 11.9 114.6 0

14-June 18.1 5.8 12.3 126.9 0

15-June 18.2 5.8 12.4 139.3 0

16-June 18.0 5.8 12.2 151.2 1

17-June 18.2 5.8 12.4 163.9 34

18-June 18.2 5.8 12.4 176.3 128

19-June 18.5 5.8 12.7 189.0 270

20-June 19.1 5.8 13.3 202.3 169

21-June 18.0 5.8 12.2 214.5 588

22-June 17.7 5.8 11.9 226.4 236

23-June 18.3 5.8 12.5 238.9 470

24-June 19.4 5.8 13.6 252.5 691

25-June 20.3 5.8 14.5 267.0 1871

26-June 18.8 5.8 13.0 280.0 310

27-June 18.6 5.8 12.8 292.8 54

28-June 19.8 5.8 14.0 306.8 36

29-June 20.0 5.8 14.2 321.0 34

30-June 20.1 5.8 14.3 335.3 0

1-July 21.5 5.8 15.7 351.0 0

2-July 21.8 5.8 16.0 367.0 8

3-July 21.8 5.8 16.0 383.0 5

4-July 21.5 5.8 15.7 398.7 4

5-July 18.5 5.8 12.7 411.4 3

6-July 18.5 5.8 12.7 424.1 0

Note: The 11-June larval catch (n = 6) are yolk-sac larvae.

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Biodiversity and Monitoring

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The timing of capture, mean size (11 mm), and CTU required for incubation of newly hatched yolk-sac larvae (95) is similar to the results documented in other early life-history studies (Kempinger 1988, Smith and King 2005). Yolk-sac larvae captured in the Black River, Michigan (Smith and King 2005) prior to the main drift, averaged 14.1 mm and hatched at a mean CTU value of 60.4. On the Wolf River, Wisconsin the first newly hatched yolk-sac larvae ranged in length from 9 – 13.1 mm, and hatched at a mean CTU value of 57.6.

Using water temperature data, we predicted the date of spawning and verified this date using drift data and back calculating CTU. From the date of spawning (May 31) to the end of drift (July 6), 411.4 CTU had accumulated. Given the variability in CTU to the end of drift, this is close to the predicted end of drift CTU value (400). The timing of spawning and period of larval drift were similar to other study years (Table 1).

RecommendationsUsing CTU to define the critical periods of lake sturgeon reproduction is a valuable tool for the development of water management practices that ensure successful spawning, hatch, and larval drift. Implementing flow management strategies that consider the following connections between water temperature and lake sturgeon reproductive ecology should ensure spawning success.

1. Spawning will commence when the water temperature reaches 13 °C.

2. Larval drift will start when approximately 150 CTU is reached.

3. In most years larval drift will be complete when 400 CTU is reached.

AcknowledgmentsThis technical note used data collected during studies initially funded by the Canada Ontario Agreement respecting the Great Lakes Basin Ecosystem (2004 to 2011). Funding to support testing of the model was provided by the Northwest Region Species at risk fund. The contributions of Upper Great Lakes Management Unit staff including Karen Schmidt (technical expertise) and Kim Ahola (data entry), the field work of Quetico-Mille Lacs Fisheries Assessment Unit staff in 2012 and 2013 (Lorne Kraft and Dan Wojick), report review (Kim Armstrong, Tim Haxton, Marilee Chase, Tom Mosindy and Charles Hendry) desktop publishing (Trudy Vaitiinen and Annalee McColm) and the assistance of summer field staff are greatly appreciated. Thanks to Ontario Power Generation for monitoring spill flows, providing spill reports and assisting with logistical aspects of the project. Thanks to Ontario Parks for allowing us to carry out this research in the park.

Literature citedAuer, N.A., and E.A. Baker. 2002. Duration and drift of

larval lake sturgeon in the Sturgeon River, Michigan. Journal of Applied Ichthyology 18(4 – 6): 557 – 564.

Auer N.A. 1996. Response of spawning lake sturgeon to change in hydroelectric facility operation. Trans. Am. Fish. Soc. 125(1): 66 – 77.

Baemesderfer, C.P. and Ruth A. Farr. Alternatives for the protection and restoration of sturgeons and their habitat. 1997. Environ. Biol. of Fishes 48: 407 – 417

Bruch, R.M., and F.P. Binkowski. 2002. Spawning behavior of lake sturgeon (Acipenser fulvescens). J. Appl. Ichthyol. 18(4-6): 570 – 579. doi:10.1046/j.1439-426.2002.00421.x.

Dumont, P., J. D’Amours, S. Thibodeau, N. Dubuc, R. Verdon, S. Garceau, P. Bilodeau, Y. Mailhot and R. Fortin. 2011. Effects of the development of a newly created spawning ground in the Des Prairies River (Quebec, Canada) on the reproductive success of lake sturgeon (Acipenser fulvescens). Journal of Applied Ichthyology 27: 394 – 404.

Friday, M. 2004. The migratory and reproductive response of spawning lake sturgeon to controlled flows over Kakabeka Falls on the Kaministiquia River, 2004. Ont. Min. Natur. Resour. Upper Great Lakes Management Unit – Lake Superior Tech. Rpt. 06.01. 27 pp.

Friday, M. 2005. The migratory and reproductive response of spawning lake sturgeon to controlled flows over Kakabeka Falls on the Kaministiquia River, 2005. Ont. Min. Natur. Resour. Upper Great Lakes Management Unit – Lake Superior QUIK Report 05.01. 16 pp.

Friday, M.J. 2006a. The migratory and reproductive response of spawning lake sturgeon to controlled flows over Kakabeka Falls on the Kaministiquia River, ON 2006. Upper Great Lakes Management Unit – Lake Superior, Ont. Min. Natur. Resour., QUIK Rpt. 06.02 13 pp.

Friday, M.J. 2006b. An assessment of growth of young-of-the-year lake sturgeon in the Kaministiquia River, ON. Upper Great Lakes Management Unit – Lake Superior, Ont. Min. Natur. Resour. Tech. Rpt. No. 06.06.

Friday, M. 2007. The migratory and reproductive response of spawning lake sturgeon to controlled flows over Kakabeka Falls on the Kaministiquia River, 2007. Ont. Min. Natur. Resour. Upper Great Lakes Management Unit – Lake Superior Tech. Rpt. 2007.01. 18 pp.

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Friday, M. 2009. The migratory and reproductive response of spawning lake sturgeon to controlled flows over Kakabeka Falls on the Kaministiquia River, 2009. Min. Natur. Resour. Upper Great Lakes Management Unit – Lake Superior Tech. Rpt. 2009.01. 21 pp.

Galat D.L. and I. Zweimuller. 2001. Conserving large-river fishes: Is the highway analogy an appropriate paradigm? J. N. Am. Benthol. Soc. 20 (2): 266 – 279.

Harkness, W.J.K. and J.R. Dymond. 1961. The lake sturgeon: The history of its fishery and problems of conservation. Ontario Department of Lands and Forests, Fish and Wildlife Branch.

Haxton, T.J. 2011. Assessing the magnitude of effect of hydro-electric facilities on lake sturgeon abundance in Ontario. Aquatic Science Unit Draft report. 22 pp.

Haxton, T.J. and C.S. Findlay. 2009. Variation in large-bodied fish community structure and abundance in relation to water management regime in a large regulated river. Journal of Fish Biology 74: 2216 – 2238.

Kempinger, J.J. 1988. Spawning and early life history of lake sturgeon in the Lake Winnebago system. Wisconsin. Pp. 110-122 in R.D. Hoyt, editor. 11th annual larval fish conference. American Fisheries Society, Symposium 5. Bethesda. Maryland.

LaHaye, M., A. Branchaud, M. Gendron, R. Verdon, and R. Fortin. 1992. Reproduction, early life history, and characteristics of spawning grounds of the lake sturgeon (Acipenser fulvescens) in Des Prairies and L’Assomption rivers, near Montreal, Quebec. Can. J. Zool. 70: 1681 – 1689.

Nilo, P., P. Dumont, and R. Fortin. 1997. Climatic and hydrological determinants of year-class strength of St. Lawrence River lake sturgeon (Acipenser fulvescens). Can. J. Fish. Aquat. Sci. 54: 774 – 780.

Parsley, M.J., P.J. Anders, A.I. Miller, L.G. Beckman, and G.T. McCabe Jr. 2002. Recovery of white sturgeon populations through natural production: Understanding the influence of abiotic and biotic factors on spawning and subsequent recruitment. Pp. 55-66 in W. Van Winkle, P.J. Anders, D.H. Secor, and D.A. Dixon, editors. Biology, management, and protection of North American sturgeon. American Fisheries Society, Symposium 28, Bethesda, Maryland.

Smith, K.M., and D.K. King. 2005. Dynamics and extent of larval lake sturgeon Acipenser fulvescens drift in the Upper Black River, Michigan. J. Appl. Ichthyology, 21(3): 161 – 168.

Appendix 1. Kempinger’s CTU equation

CTU = ∑=

−n

ii Kx

1)(

K = the constant (5.8 °C)

xi = mean daily water temperature ( °C) for day i

calculated from real time data

n = number of days from spawning to end of drift

Friday, M.J. 2014. Estimating the critical reproductive periods of lake sturgeon (Acipenser fulvescens) using daily water temperature units. Ont. Min. Natur. Resour., Northwest Bio. & Mon, BAMS Technical Report TN-48. 7 pp.

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