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  • Shock and Awe! Es4ma4ng Mysis Density and Catch Avoidance ... · - We sampled on quarter and full moon phases. - Water clarity in Lake Michigan is higher than in oceans due to LM’s
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Background Sample Design • Our sampling scheme followed that of Wiebe et al. (2004, 2013) for krill aggregaAons in deep oceans off AntarcAca and in North AtlanAc Ocean. • We conducted power analysis of Wiebe et al. (2013)’s krill density esAmates to esAmate numbers of replicates (n=4) needed to detect significant differences in Mysis density between strobe on and strobe off. WELLS, D. 1 , PSAROUTHAKIS, Z. 1 , RUTHERFORD, E. 2 , CHIN, T. 1 , VANDERPLOEG, H. 2 , CAVALETTO, J. 2 , GLYSHAW, P. 1, and Mason, D. 2 1 CooperaAve InsAtute for Limnology and Ecosystems Research , 2 NOAA GLERL Shock and Awe! Es4ma4ng Mysis Density and Catch Avoidance using the MOCNESS in SE Lake Michigan Results Acknowledgments: This work is supported by NOAA GLERL. Mysis diluviana (opossum shrimp) is a key member of Great Lakes aquaAc food webs and an important prey for pelagic fish. Mysis are visual predators of zooplankton, and undergo diel verAcal migraAon from the lake bo_om (day) into the water column at night. Mysis biomass esAmates are highly variable but criAcal for food web models that inform salmonid stocking decisions. In 2016, we evaluated catch efficiency of Mysis in a MulAple Opening/Closing Net and Environmental Sensing System (MOCNESS) with LED strobe lighAng that is used to sample Euphausid shrimp (krill), plankton and fish larvae in marine waters. We made replicate tows in thermally straAfied depth layers during night, and compared Mysis densiAes sampled with the LED strobe on vs strobe off. There were no significant differences in Mysis density or size in samples with strobe on or off in any month. Mysis densiAes were highest in the metalimnion at night. We conclude that the strobe flash light had no effect on catch avoidance by Mysis. Abstract Why no difference in Mysis density or size in nets with strobe on/off? • Too much ambient light! - We sampled on quarter and full moon phases. - Water clarity in Lake Michigan is higher than in oceans due to LM’s lower producAvity and intense filtraAon by invasive dreissena mussels. - Our sample sites in Lake Michigan were shallower and closer to shore. Wiebe et al. (2013) sampled krill in deep, remote ocean sites far from land. • Perhaps Mysis are more light sensiAve than krill. Why was Mysis density highest in metalimnion? – They migrate at night to areas of high zooplankton prey density. Research Objec4ve and Hypothesis • EsAmate catch avoidance by Mysis in Lake Michigan at a mid depth and offshore staAon (M45, M110) using MOCNESS with LED strobe lights. Figure 1. Map of sampling sites off Muskegon, MI in S.E. Lake Michigan. Wiebe, P. E., Ashjian, C. J., Gallager, S. M., Davis, C. S., Lawson, G. L., and Copley, N. J. 2004. Using a high-powered strobe light to increase the catch of AntarcAc krill. Marine Biology 144: 493–502. Wiebe, P. E., Lawson, G. L., Lavery, A. C., Copley, N. J., Horgan, E., and Bradley, A. 2013. Improved agreement of net and acousAcal methods for surveying euphausiids by miAgaAng avoidance using a net based LED strobe light system. ICES J. Marine Science 70:650-664. Are bigger Mysis caught with strobe flash? Study Area Mysis were collected from S.E. Lake Michigan at a 45m site (M45) in June, and a 110 m site (M110) in July and September, 2016 (Figure 1). Methods Field CollecCons Methods Discussion & Future Direc4ons Literature Cited and Acknowledgments Results Future Work Are more Mysis caught with LED strobe flash? • Sample during new moon. In 2016, we sampled on quarter moon (June, July) and full moon (Sept.) phase due to ship availability. • Test whether Mysis catchability varies by LED strobe intensity, duraAon or pulse. • Evaluate catchability of fish larvae in nets with LED strobe on/off. Will larval fish catchability be suscepAble to strobe flash “shock and awe”? We hypothesized Mysis densi4es sampled by MOCNESS would be higher with the LED strobe light on vs. off. Figure 2. Above leI - VerAcal profile of temperature at the 45 m staAon in July, and example of MOCNESS sample track in the metalimnion with LED strobe flash on (in white) and off (in red). Above right – Laser opAcal plankton counter shows highest zooplankton density in the metalimnion. BoLom - HydroacousAcs profile shows highest Mysis densiAes at 18m in the metalimnion (1 km screen image). Mysis density in the water column Figure 3 (ler). Mysis collected at night at the 45 m site in June and the 110 m site in July indicated mean (± s.e.) Mysis density was higher in the metalimnion than in the epilimnion (p > 0.236). The hypolimnion was not sampled in either month because of lack of Ame. Figure 4 (ler). Data from all sites and months indicate there was no significant difference (P>0.36) in mean density (± s.e.) of Mysis with strobe on or off. Figure 5 (ler). Data from the 45 m site in June indicate there was no significant difference (P>0.53) in mean length (± s.e.) of Mysis caught between strobe on or off. Mysis: are cold-water shrimp-like organisms that feed opportunisAcally on plankton and benthos. With two stalked compound eyes, Mysis diel verAcal migraAon is highly sensiAve to light level and temperature. MOCNESS with strobe is a MulAple Opening Closing Net, with an Environmental Sensing System plus LED strobe lights. Our MOCNESS system has 9, 1-m 2 nets; each net can be closed and opened independently at depth so that it samples a discrete patch of water. The MOCNESS records temperature, depth, chlorophyll, oxygen and light levels during each sample. The LED strobe lights have been shown to improve catchability of krill in marine systems (Wiebe et al. 2013) We targeted thermal strata where laser opAcal counts of zooplankton were high and backsca_er from fisheries acousAcs showed potenAally high densiAes of Mysis. We tow-yo’d MOCNESS nets (total number of net samples=40) for 10 minutes each within thermal strata. We randomized the on/off sequence of LED strobe lights for each net. All samples were preserved in ethanol, and Mysis were later counted and measured in the laboratory. On Off Depth(m) Amplitude(Db)

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Page 1: Shock and Awe! Es4ma4ng Mysis Density and Catch Avoidance ... · - We sampled on quarter and full moon phases. - Water clarity in Lake Michigan is higher than in oceans due to LM’s

Background

SampleDesign•  Our sampling scheme followed that of Wiebe et al. (2004, 2013) for krill

aggregaAonsindeepoceansoffAntarcAcaandinNorthAtlanAcOcean.•  WeconductedpoweranalysisofWiebeetal.(2013)’skrilldensityesAmatesto

esAmatenumbersofreplicates(n=4)neededtodetectsignificantdifferencesinMysisdensitybetweenstrobeonandstrobeoff.

WELLS,D.1,PSAROUTHAKIS,Z.1,RUTHERFORD,E.2,CHIN,T.1,VANDERPLOEG,H.2,CAVALETTO,J.2,GLYSHAW,P.1,andMason,D.2

1CooperaAveInsAtuteforLimnologyandEcosystemsResearch,2NOAAGLERL

ShockandAwe!Es4ma4ngMysisDensityandCatchAvoidanceusingtheMOCNESSinSELakeMichigan

Results

Acknowledgments:ThisworkissupportedbyNOAAGLERL.

Mysis diluviana (opossum shrimp) is a key member of Great Lakes aquaAc foodwebs and an important prey for pelagic fish. Mysis are visual predators ofzooplankton,andundergodiel verAcalmigraAon from the lakebo_om (day) intothewatercolumnatnight.MysisbiomassesAmatesarehighlyvariablebutcriAcalfor food web models that inform salmonid stocking decisions. In 2016, weevaluated catch efficiency of Mysis in a MulAple Opening/Closing Net andEnvironmentalSensingSystem(MOCNESS)withLEDstrobelighAngthatisusedtosample Euphausid shrimp (krill), plankton and fish larvae in marine waters. WemadereplicatetowsinthermallystraAfieddepthlayersduringnight,andcomparedMysis densiAes sampled with the LED strobe on vs strobe off. There were nosignificantdifferences inMysisdensityor size in sampleswith strobeonoroff inanymonth.MysisdensiAeswerehighestinthemetalimnionatnight.WeconcludethatthestrobeflashlighthadnoeffectoncatchavoidancebyMysis.

Abstract

WhynodifferenceinMysisdensityorsizeinnetswithstrobeon/off?•  Toomuchambientlight!

-Wesampledonquarterandfullmoonphases.-WaterclarityinLakeMichiganishigherthaninoceansduetoLM’slowerproducAvityandintensefiltraAonbyinvasivedreissenamussels. -Our samplesites inLakeMichiganwereshallowerandcloser toshore.Wiebe et al. (2013) sampled krill in deep, remote ocean sites far fromland.

•  PerhapsMysisaremorelightsensiAvethankrill.

WhywasMysisdensityhighestinmetalimnion?–Theymigrateatnighttoareasofhighzooplanktonpreydensity.

ResearchObjec4veandHypothesis•  EsAmatecatchavoidancebyMysisinLakeMichiganatamiddepthand

offshorestaAon(M45,M110)usingMOCNESSwithLEDstrobelights.

Figure1.MapofsamplingsitesoffMuskegon,MIinS.E.LakeMichigan.

Wiebe,P.E.,Ashjian,C.J.,Gallager,S.M.,Davis,C.S.,Lawson,G.L.,andCopley,N.J.2004.Usingahigh-poweredstrobelighttoincreasethecatchofAntarcAckrill.MarineBiology144:493–502.

Wiebe,P.E.,Lawson,G.L.,Lavery,A.C.,Copley,N.J.,Horgan,E.,andBradley,A.2013.ImprovedagreementofnetandacousAcalmethodsforsurveyingeuphausiidsbymiAgaAngavoidanceusinganetbasedLEDstrobelightsystem.ICESJ.MarineScience70:650-664.

ArebiggerMysiscaughtwithstrobeflash?

StudyAreaMysiswerecollectedfromS.E.LakeMichiganata45msite(M45)inJune,anda110msite(M110)inJulyandSeptember,2016(Figure1).

Methods

FieldCollecCons

Methods

Discussion&FutureDirec4ons

LiteratureCitedandAcknowledgments

Results

FutureWork

AremoreMysiscaughtwithLEDstrobeflash?

•  Sampleduringnewmoon.In2016,wesampledonquartermoon(June,July)andfull

moon(Sept.)phaseduetoshipavailability.•  TestwhetherMysiscatchabilityvariesbyLEDstrobeintensity,duraAonorpulse.

•  Evaluate catchability of fish larvae in nets with LED strobe on/off. Will larval fishcatchabilitybesuscepAbletostrobeflash“shockandawe”?We hypothesizedMysis densi4es sampled byMOCNESS would be higher

withtheLEDstrobelightonvs.off.

Figure2.AboveleI-VerAcalprofileoftemperatureatthe45mstaAoninJuly,andexampleofMOCNESSsampletrackinthemetalimnionwithLEDstrobeflashon(inwhite)andoff(inred).Aboveright–LaseropAcalplanktoncountershowshighestzooplanktondensityinthemetalimnion.BoLom-HydroacousAcsprofileshowshighestMysisdensiAesat18minthemetalimnion(1kmscreenimage).

Mysisdensityinthewatercolumn Figure3(ler).Mysis

collectedatnightatthe45msiteinJuneandthe110msiteinJulyindicatedmean(±s.e.)Mysisdensitywashigherinthemetalimnionthanintheepilimnion(p>0.236).ThehypolimnionwasnotsampledineithermonthbecauseoflackofAme.

Figure4(ler).Datafromallsitesandmonthsindicatetherewasnosignificantdifference(P>0.36)inmeandensity(±s.e.)ofMysiswithstrobeonoroff.

Figure5(ler).Datafromthe45msiteinJuneindicatetherewasnosignificantdifference(P>0.53)inmeanlength(±s.e.)ofMysiscaughtbetweenstrobeonoroff.

Mysis:arecold-watershrimp-likeorganismsthatfeedopportunisAcallyonplanktonandbenthos.Withtwostalkedcompoundeyes,MysisdielverAcalmigraAonishighlysensiAvetolightlevelandtemperature.

MOCNESSwithstrobeisaMulApleOpeningClosingNet,withanEnvironmentalSensingSystemplusLEDstrobelights.OurMOCNESSsystemhas9,1-m2nets;eachnetcanbeclosedandopenedindependentlyatdepthsothatitsamplesadiscretepatchofwater.TheMOCNESSrecordstemperature,depth,chlorophyll,oxygenandlightlevelsduringeachsample.TheLEDstrobelightshavebeenshowntoimprovecatchabilityofkrillinmarinesystems(Wiebeetal.2013)

WetargetedthermalstratawherelaseropAcalcountsofzooplanktonwerehighandbacksca_erfromfisheriesacousAcsshowedpotenAallyhighdensiAesofMysis.Wetow-yo’dMOCNESSnets(totalnumberofnetsamples=40)for10minuteseachwithinthermalstrata.Werandomizedtheon/offsequenceofLEDstrobelightsforeachnet.Allsampleswerepreservedinethanol,andMysiswerelatercountedandmeasuredinthelaboratory.

On

Off

Depth(m)

Amplitu

de(Db)

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