zLIM- -99-001 c2 Oaphnia lumholtzi: The Next Great Lakes Exotic? James A. Stoecke} Patrice M. Charlebois Illinois Natttral History Survey Illinois-IndianaSea Grani College Program, Illinois NaturalHistory Sttrvcy, Dcpartmetttof Natural Resourcesand EnvironmentalScicnccs, University of Illinois

Daphnia iumhoifzi, an exotic zooplanktonspecies, has beenwell as long as the body, which is partially coveredwith smaller establishedin the illinois River since 1995,and now appears spines,Large individuals can reach total lengths of 5.6min poisedto invadeLake Michigan. This invasion will likely be nearly0.25 in!, makingthem visible to thenaked cye. facilitated by the system of locks, dams, and artificial canals connectingLake Michigan and the Illinois River. Constructionof Potential impacts this connectionbetween two major drainagebasins, the Great Scientistsare concerned that iumhoitzi may have Lakes-St.Lawrence and the Mississippi, was initiated in the late negativeeFects on NorthAmerican ecosystems. The large 1800sand now, unintentionally,provides a conduitfor exotic spinesmake it diITicultfor youngfish larvaland juvenile stages! speciesestablished in onebasin to invadethe other. For example, to consumethis exotic, Native Daphnia havefewer, smaller zebra mussels invaded the Great Lakes in the 1980s and are now spines Fig. I! and,therefore, are more susceptible to fish well establishedin the Mississippi River and severalof its .The protection from predationafforded by its spines tributaries.Daphnia iumholfzi, alreadycommon in the Illinois mayallow Daphnialumholrzi to replace native Daphnia species. River, is now found in the canalsystem near Lake Michigan, and If this replacementoccurs, the amountof food availableto Iarval maysoon be anotherunwelcome addition to thelong list of non- andjuveiule fishes may be reduced. This could result in reduced native species that have become established in the Great Lakes. survivorshipof young sport and food fishes in lakes,rivers, and fish hatcherieswhere Daphnia lumhoitzi becomesabundant.

Cladocerans,also known as water fleas, are a typeof Fishesthat most likely would be affected are late-spawning nearlyinvisible to thenaked eye. Despitetheir small size, they speciessuch as bassand other sunfish. In the Midwest, arean important food source for larvaland early juvenile stages populationsof Daphniaiumhoitzi tend to peakduring mid- of nearly every speciesof North American fish. One of the most summerwhen juveniles of thesefishes may still bedependent on important and well studiedcladoceran groups is Daphnia. zooplanktonas a primaryfood source. Reduced survivorship of Daphnia spendmost of their time drifting in the water column theseyoung fishes is a worst-casescenario and may not occur where they feedon algal cells andother small particles. everywhereDrtphnia lumholrzi becomesestablished.

Daphnialumhoirzi is a speciesof Daphniathat has recently Initial studiesindicate Daphnia lumhoitzi is havingvarying invadedNorth America. Easily identified, Daphnia iumhoitzi effectson the zooplanktonof North American lakes and producesmuch larger and more numerousspines than do North reservoirs, In Norris Reservoir TN!, larval andjuvenile AmericanDaphnia Fig. I !. Thehead and tail spinesmay be threadfinshad avoided Daphnia iumholrzi, but fedheavily on other Daphnia species. Despitethe disparity in predation pressure,Daphnia lumholtzi did not appearto be replacing native Daphnia populations. Studiesof reservoirsin Kentucky and Illinois,however, indicate that Daphnia iumhoirzi may be replacingnative Daphnia and other zooplankton species. Ultimate effects of this invasive specieswill becoinemore apparentin subsequentyears as long-term trendsin zooplankton abundanceand fish survivaland growth within ecosystems invadedby Daphnia lumholrzi are documented.

Inhuduction and Spread Daphnia iumhoitzi is native lo Africa, Asia, and Australia. It most likely was brought to North America with African fish imported for the aquarium bade or to stock reservoirs. The earliestpublished record of Daphniahcmholrzi in NorthAinerica is from a Missouri reservoir in 1990. This date of first detection Daphnis Daphnis Daphnis Daphnis will likely change,however, as sainples collected prior io 1990 iumhnttai mendoise parvuls srnblasrs g i/4 in g 1Nin < i/Ih in s t/ier in arere-examined. In Illinois, Daphnia iumhoitzi hasbeen established in several reservoirs since 1992. It was first Figurei. CrimmonDrrphnirr species of theillinois Riverdrainage basin as comparedto the new invader,l>aphnia lrrrnhrrttzi,and a GreatLakes invader, documentedin theIllinois Riverin 1995,but wasprobably Bvthirtrepheseederstrrremi ithe spinywater fleah Adding to the mix. Daphnia presentsporadically in the river since 1991. In 1995.Daphnia rnendr>taeshown here may actually be a hybrid betweenDaphnia medotaeand a Europeanspecies, Daptrnia //a!err/a. lumholtzi was collected as far north as Illinois River Mile IRM! What Can Be Donee 195.9, approximately I 35 river miles from Lake Michigan Eliminating a speciesonce it hasbecome established can be Fig. 2!. In 1996,it was found in the Cal-SagChannel extremely difTicult. Therefore, it is important that wc work to prevent the initial introduction of exotic species such as Daphnia lumholtzi. Variousresearch projects, educational activities, and state and federaI regulations are established to prevent initial introductions. Once a speciesbecomes established, we can work to slow its spread. Recreational water userscan avoid accidentallyspreading established exotic nuisance species and in some cases prevent new introductions! with a few simple steps see below!. Aquarium enthusiasts can help, too, by neverdumping aquariawater or aquarium Iaag organismsinto local lakes or streams. Sometropical plants and PNII fish can survive northern winters, and undetected hitchhikers such as zooplankton may thrive,

What Can You Dot" I! Learn how to identify exotic speciessuch as Daphnia lumholtzi see Fig. I!. Biologists rely on sightings reported by Figure 2. Known proxiinity ol Dapttnirt fttrtnrtrrltzito LaleeMichigan in the illinois River and he Cal-SagChannel, I995-1998 RM = river tniieh the public to track the spreadof thesespecies. Your help is extremelyimportant. Daphnia lumholtzi may be visible to the approximately30 river miles from Lake Michigan, In l997 and nakedeye in standingwater of baitbuckets,livewells, etc, 1998, Daphnia lurnholtzi was collected just upriver of the T.J. 2! If you find Daphnia lumholtzi or any other exotic O' Brien Lock and Dam, less than 10 river miles froin Lake species!,preserve it in rubbing alcohol or freezeit. Preservation Michigan. This species is likely to invade Lake Michigan in the of the specimenallows for expertconfirmation of the near future if it hasnot done so already. identification. Then, contact Sea Grant Illinois-Indiana Sea Grant: 847 872-8677!,or your statenatural resourcesagency. Daphnia lumholtzi may have spread upriver toward Lake Michigan in a number of ways. Although it likely does not swim against river currents, Daphnia lumholtzi may have traveled upriver in baitbucketsor in bilge-water of recreationaland BEFORE leaving boat launch: commercial watercraft. It may also have spread upriver in its Inspectboat, trailer, and equipment;then remove dormantegg stage, Occasionally,Daphnia lumholtzi producesa any observedplants and animaJs. pair of resting eggs coated in a protective coating called an ephippiuin I fip' ee um!. This ephippiutnprotects the resting Drain, on land, all water from the motor, eggsagainst drying and freezing. Theseephippial eggsmay be livewell, biIge, and transom well. transported far distances overland by migrating birds, high winds, and human activities. Emptywater from bait bucke~ ~;, '; ','~ and disposeof unwante ' rittttash, Potential for Successin Lake Michigan The likelihood of Daphnia lumholtzi establishing large AFTER leaving boat lpuigCh. x' populationsin Lake Michigan is uncertain. In the IIIinois River, Washall equtpttienl~bi %'water Daphnia lumhoftzi exhibits peak abundances and highest ora highpressure s~y!r.i reproductionrates during mid-summerwhen water temperatures are 20-3&6 0-86'F!. Individuals with eggs, however, have OR gt.e~$t been collected from the Illinois River in water temperatures of i 3- IO"C 7-50"F!. If most individuals are intolerant of cool Dryequipment forat/epP Eve temperatures,Daphnia lumholtzi may be restrictedto warm surfaceand nearshorewaters of Lake Michigan. Cold-tolerant individuals, however, may be able to establish viable populations Thispublicatiun is jointly publishedby thclllinoisdndiana raniCollege Program, PhillipF. Pope,Director; the illinois Natural ItistoryS y, DavidL. Thomas,Chief: throughout the lake. andthe Department vf NaiuralRcrarurccs and Environmental Setencet, UIUC,Gary L. Rolfc,Chair. Funding is providedby iheNauonal Sea Grant CollegeProgram National JCeanic and Airnospheric Adminittra ion, JI ! Another introduced cladoceran, the spiny waterflea Bythotrephes US. Depanrneniof Commerceunder Crrant JJNAgfrRGJJtyttt. Illinois-Indiana cederstroemi, is already established in Lake Michigan. In some ScaGrani is «joim I'ederaland stain progmm of Purdueilnivcrsity. Wcsi I.afayetteand the lJniversity of Illinoisat llrhana-Champaign.Purdue I Jinver«ty and areas, it has caused a reduction in the abundance of small Universityoi Iuinvisvflcr cttualvppvrtuniticv in pnrgrarnaand employment. cladoceranspecies. Unlike Daphnia lumhoitzi, Bythotrephesis a predator and feeds mainly on other zooplankton; it is unknown NATJJRAl whether Bythotrepheswill feed on Daphnia lumholtzi. If Bythotrephes does not eat it, Daphnia lumholtzi may have even more of a competitive advantage over native cladocerans. Foradditional copies, contact the Sca Grant cvrnmunicauonsoflice: Ph. 217 t3 t-iJ44g Fax:217 ttt.2614 Fmail.gocttelt+uiuc.cdu SeaCrrant PuhliCaiinn IISG-rtrt- IIJ