1 University of Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences Volume 6 Number 1 2002 Highlighting UF/IFAS Programs in Fisheries and Aquatic Sciences, Aquaculture, and Pond Management D e p a r t m e n t o f F i s h e r i e s & A q u a t i c S c i e n c e s U n i v e r s i t y o f F l o r i d a IFAS The Sam Mitchell Aquaculture Demon- stration Farm in Blountstown is one of several facilities that were closed due to severe budget reductions imposed on UF/IFAS in the wake of Florida’s budget deficit. Budget call- backs for the current fiscal year and large cuts anticipated fo next year have resulted in immediate closure or consolidation of both on- and off-campus IFAS units. In conjunction with the closure and reduction in these facilities, many of the associated staff have been laid off to meet the budget restrictions. The aquaculture facility, part of UF/IFAS’ Department of Fisheries and Aquatic Sciences (FAS), was opened in 1988 to provide commercial fish farmers with the latest technology and management practices in foodfish and baitfish aquaculture. Through the years, work at the 40-acre farm has included applied production research and demonstration on species such as sturgeon, golden shiners, Gulf killifish, hybrid striped bass, and fancy goldfish. The official closing date for the Sam Mitchell Aquaculture Demonstration Farm was February 28. Equipment and supplies at the facility have been moved to the Department’s core facility in Gainesville and to its Tropical Aquaculture Lab in Ruskin for use in on-going programs. Disposition of the property has yet to be determined. UF/IFAS Blountstown Aquaculture Facility Closed Though all staff positions associated with the Blountstown facility were eliminated, FAS is using temporary grant funding to retain Debbie Britt Pouder as a Senior Biological Scientist assisting with aquaculture extension and applied research programs in the Florida Panhandle. For general aquaculture information, Debbie can be reached on Monday’s at the Bay County Extension Office in Panama City at 850/784-6105. Calendar of Events April 4-5 Fish Health Management Workshop Tropical Aquaculture Lab / Ruskin Roy Yanong 813/671-5230 x104 April 11 Parasite Identification Workshop Tropical Aquaculture Lab / Ruskin Roy Yanong 813/671-5230 x104 May 13 Pond Management Workshop for Rural And Recreational Pond Owners Hardee County Civic Center/ Wakulla John Brenneman 863/533-0765 May 13-24 Diseases of Warmwater Fish Tropical Aquaculture Lab / Ruskin Whitney Lab / St. Augustine Ruth Francis-Floyd 352/392-9617 x229 May 19-24 Aquatic Weed Control Short Course 2002 Ft. Lauderdale Research & Education Center Ft. Lauderdale Marriott North Beth Miller Tipton 352/392-5930 Debbie Britt Pouder, foreground, captures a young sturgeon as Dave Carpenter, left, and Randall Kent pull the fish net toward the shoreline at the (former) Sam Mitchell Aquaculture Demonstration Farm. Milt Putnam, UF/IF AS Communication Services
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University of Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences Volume 6 Number 1 2002
Highlighting UF/IFAS Programs in Fisheries and Aquatic Sciences, Aquaculture, and Pond Management
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Depar
tmen
tof
Fisheries & AquaticS
ciences
Univer
sityof Florid
a
IFAS
The Sam Mitchell Aquaculture Demon-stration Farm in Blountstown is one of severalfacilities that were closed due to severebudget reductions imposed on UF/IFAS in thewake of Florida’s budget deficit. Budget call-backs for the current fiscal year and largecuts anticipated fo next year have resultedin immediate closure or consolidation of bothon- and off-campus IFAS units. In conjunctionwith the closure and reduction in thesefacilities, many of the associated staff havebeen laid off to meet the budget restrictions.
The aquaculture facility, part of UF/IFAS’Department of Fisheries and AquaticSciences (FAS), was opened in 1988 toprovide commercial fish farmers with thelatest technology and management practicesin foodfish and baitfish aquaculture. Throughthe years, work at the 40-acre farm hasincluded applied production research anddemonstration on species such as sturgeon,golden shiners, Gulf killifish, hybrid stripedbass, and fancy goldfish. The official closingdate for the Sam Mitchell AquacultureDemonstration Farm was February 28.
Equipment and supplies at the facilityhave been moved to the Department’s corefacility in Gainesville and to its TropicalAquaculture Lab in Ruskin for use in on-goingprograms. Disposition of the property hasyet to be determined.
UF/IFASBlountstownAquacultureFacility Closed
Though all staff positions associated withthe Blountstown facility were eliminated, FASis using temporary grant funding to retainDebbie Britt Pouder as a Senior BiologicalScientist assisting with aquaculture extensionand applied research programs in theFlorida Panhandle. For general aquacultureinformation, Debbie can be reached onMonday’s at theBay CountyExtension Officein Panama Cityat 850/784-6105.
Calendar ofEvents
April 4-5Fish Health Management WorkshopTropical Aquaculture Lab / RuskinRoy Yanong 813/671-5230 x104
May 13Pond Management Workshop forRural And Recreational Pond OwnersHardee County Civic Center/ WakullaJohn Brenneman 863/533-0765
May 13-24Diseases of Warmwater FishTropical Aquaculture Lab / RuskinWhitney Lab / St. AugustineRuth Francis-Floyd 352/392-9617 x229
May 19-24Aquatic Weed ControlShort Course 2002Ft. Lauderdale Research &Education CenterFt. Lauderdale Marriott NorthBeth Miller Tipton 352/392-5930
Debbie Britt Pouder, foreground, captures ayoung sturgeon as Dave Carpenter, left, andRandall Kent pull the fish net toward the shorelineat the (former) Sam Mitchell AquacultureDemonstration Farm.
Milt
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Student Involvement at UF
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Undergraduate and graduate students are an important part of the teaching, research,and extension programs at the University of Florida. Student involvement is high-lighted in each issue of WaterWorks.
The following UF/IFASfaculty and staff areavailable to answerquestions or providetechnical support foraquaculture, fisheries andaquatic sciences, andpond management.
Ed Sullivan received abachelor of sciencedegree in Marine Biologyfrom the University ofWest Florida in May of1999. That fall, he beganhis graduate studies atthe University of Floridaunder Dr. Debra Murie. Ed was interested instudying new manage-ment techniques formarine fisheries andproposed the idea ofstudying hatchery-rearedred drum in the wild.
Dr. Murie and co-investigator Dr. DarylParkyn were able tosecure funding for asmall project involvingthe cooperation of FloridaPower and Light’s (FP&L)Mariculture Center and theUSGS ChassahowitzkaNational Wildlife Refuge. In the refuge, theyreleased approximately20,000 juvenile red druminto two creeks in Juneof 2000. Subsequent tothe release (within thefirst week) they observeda high rate of disappear-ance from the releasecreeks. Based onrecapture locations andultra-sonic tracking oftagged fish, fish thatsurvived the releaserapidly emigrated out ofthe tidal creeks.
The project demon-strated that both thelocation of the releasesite and the seasons areimportant considerationswhen releasing hatchery-reared red drum into thewild and tracking theirprogress into a red drumfishery. “Our original plan wasto release two-inchfingerling redfish into therefuge in the autumn,”said Sherwood. “This
would have been an in-season release. However,due to a variety of hatcheryconstraints, we released2.5-inch fingerlings duringJune of 2000. This made itan out-of-season release,and allowed us to evaluateit against in-seasonreleases.” Our results provide abasic insight into the useof supplemental stockingas a management strategyfor red drum. “We expected the fishto move from the creeks,but were surprised at justhow quickly they moved.We assume that themajority of fish left thecreeks (rather than died)because we ultrasonicallytracked similar sized reddrum during the post-release period and mostof these fish moved towardthe mouth of the creeksbefore disappearing.” In June of 2001, Edbegan work at the FloridaMarine Research Institute(FMRI) as a researcher inthe Fisheries IndependentMonitoring Program (FIM).FIM tracks the relative
abundance of a varietyof marine fish and selectinvertebrates within theTampa Bay estuary andmonitors the release ofhatchery-reared reddrum into the AlafiaRiver. The goal of thestudy is to increaserecreational catches ofred drum in Tampa Bayby 25 percent. Ed wasdrawn to the project, asit pertained to hisgraduate work. During his short timewith FMRI, Ed wasoffered a position as aMarine Research Assoc.in November of 2001.He is now working onseveral projects includinga gear comparison study;the Project Tampa Baystudy; an examinationof the distribution andabundance of red drumin three Florida estuaries;and the development ofa temporal and spatialmodel of red drumwithin Tampa Bay. “I enjoy my workvery much,” says Ed.“I’m in the field two orthree days a week andhave used a variety ofgear to capture and studyestuarine fish. I’vegained a tremendousamount of field experienceand am starting to getmore involved with dataanalysis. My long-termgoals are to be involvedwith annual stockassessments andmanagement decisionsof Florida’s marinefisheries. I think I canaccomplish these goalshere at FMRI.” Ed iscurrently writing hisMaster’s thesis andhopes to defend it thisSpring.
Dr. Debra Murie352/392-9617 x 245
Ed Sherwood
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Curbing Cormorants
WaterWorks is published by UF/IFASDepartment of Fisheries and AquaticSciences. Subscriptions are free. (See thesubscription form on page 8.) Questions,comments or editorial submissions maybe submitted by contacting:
T he U.S. Fish and Wildlife Service recently released a draft Enviro-
mental Impact Statement (EIS) forpublic review that will guide developmentof a nationwide management strategy fordouble-crested cormorants.
The EIS analyzes various options formanaging rapidly growing cormorantpopulations—to reduce conflicts withrecreational anglers, commercial aquacul-ture companies, and other human activities.
“The double-crested cormorant was givenFederal protection during serious populationdeclines in the 1970’s. Today, we face adifferent problem as we seek to achievesustainable populations and reduce conflictswith human activities,” said Tom Melius, theService’s assistant director for MigratoryBirds and State Programs.
Cormorants have been federally protectedby the Migratory Bird Treaty Act since 1972,when they were given protection after theirpopulations dropped precipitously due to thepesticide DDT, killings by humans, and theoverall declining health of many ecosystems,especially the Great Lakes. Today, thepopulation is at historic highs, due in largepart to the presence of ample food in theirsummer and winter ranges, federal and stateprotection, and reduced contaminant levels.
Between 1970 and 1991, in the GreatLakes region of the U.S. and Canada, thenumber of double-crested cormorant nestsincreased from 89 to 38,000, with anaverage annual increase of 29 percent. By1997, the Great Lakes population reachedapproximately 98,000 pairs. The totalpopulation of double-crested cormorants inthe U.S. and Canada has most recently beenestimated at some 2 million birds.
The population resurgence of double-crested cormorants has led to increasingconcern about the bird’s impact on commer-cial and recreational fishery resources.
The draft EIS evaluates six managementalternatives, including such options ascontinuing current management practices,implementing only non-lethal managementtechniques, issuing a new DepredationOrder to address public resource conflicts(the Service’s proposed alternative) andestablishing frameworks for a cormoranthunting season.
Cormorants and other waterbirds such aspelicans and herons can have adverseimpacts on fish populations when fish areconcentrated in artificially high numbers—
conditions such as those found at fishfarms, hatcheries, and sites where hatch-ery-reared fish are released. The Servicehas previously taken action to protect fish inthese situations.
In 1998, the Service issued a DepredationOrder authorizing commercial freshwateraquaculture producers in 13 states includingFlorida, to take this species of cormorantwithout a federal permit, when the birdswere found committing or about to commitdepredations to aquaculture stocks.
The Depredation Order states thatdouble-crested cormorants may be taken byshooting only during daylight hours, andonly when necessary to protect freshwatercommercial aquaculture and state-operatedhatchery stocks and that such actions mustbe carried out in conjunction with a non-lethal harassment program.
The 1998 Order does not addressimpacts on commercial and recreationalfisheries. The effect of cormorants on fishpopulations in open waters is less clear thanat aquaculture facilities. In some cases,research suggests that cormorants appearto be capable of taking numbers of sportfish significant enough to have a negativeimpact on catch rates.
The Service believes that at this time,there is no sufficient scientific evidence tojustify controlling cormorants on a nationallevel to benefit open water commercialfisheries. Where site-specific problems aresignificant, the Service’s practice is, and willcontinue to be, to issue depredation permitsto alleviate conflicts outside the authority ofthe depredation orders.
The Service’s proposed action wouldestablish a new Depredation Order authoriz-ing state, tribal and federal land managementagencies to implement a double-crestedcormorant management program while main-taining Federal oversight of populations viareporting and monitoring requirements toensure sustainable populations.
Control activities carried out under thisnew depredation order would take place onpublic and private lands and waters wherethese cormorant populations are demon-strably having a negative impact on publicresources.
Under this action, the 1998 AquacultureDepredation Order would continue to allowcormorants to be taken at commercialfreshwater aquaculture facilities and state-owned fish hatcheries in 13 states and
would be expanded to include winter roostcontrol by the U.S. Department ofAgriculture’s Wildlife Services Program inthose states. A service regulation prohibitinglethal control of cormorants under mostcircumstances at National Fish Hatcherieswould be revoked.
Requests for copies of the draftEnvironmental Impact Statementshould be mailed to:
Chief/Division of Migratory Bird Mgmt.U.S. Fish and Wildlife Service4401 N. Fairfax Drive, Room 634Arlington, VA 22203
Copies can also be downloaded from theDivision of Migratory Bird Managementweb site at:
A reproducing population of exoticconvict cichlids Cichlasoma nigrofasciatumwas recently eradicated from Green Pond,near the J. Wayne Reitz Union, on theUniversity of Florida (UF) main campus.
The cichlids are small tropical fish (< 5 inch),native to Central America, that havemanaged to survive Gainesville’s wintertemperatures due to the constant inflow ofwarm water from the Reitz Union’s heatingand cooling system.
The Florida Fish and Wildlife ConservationCommission (FWC) requested that GreenPond be renovated to remove the convictcichlids — the only reproducing populationin Florida. Personnel from UF/IFAS’ Dept. ofFisheries and Aquatic Sciences, under thedirection of Dr. Chuck Cichra, conducted theeffort, with assistance from the FWC andFlorida Museum of Natural History. Thepond will be restocked with native fishes.
Over 1,000 convict cichlids were removedalong with two other exotic fish species, twoblack pacu Colossoma macropomum and asingle oscar Astronotus ocellatus. It’s unknownexactly how these exotic fish ended up inthe pond, but all are popular aquarium fish.(It’s illegal to release any non-native fish intoopen waters of Florida.) Regardless of howthey got there, it is the legal responsibility ofthe landowner to keep these fish out of thewater. In this case, UF had the honors. TheFWC, which has regulatory and enforce-ment authority over exotic fishes, workedclosely with UF to remove the fish.
Florida has several species of exoticfishes that have established reproducingpopulations. Most of them are undesirableand represent potential problems for nativespecies. Green Pond is being used as anexample, for the University community andthe public, of the legal, environmental, andethical issues involved in fish introductions.Extension materials, and a series of popularand scientific articles are currently underdevelopment. Signs discouraging fishreleases will also placed near UF ponds.Look for more information in the next issueof WaterWorks.
Jeff Hill352/392-9617 x 236
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UF/IFAS Fisheries and Aquatic Sciences, Aquaculture,and Pond Management Update
Clam farmers (and anyone else for thatmatter) can now go on-line to checkcurrent water quality and weather dataconditions at a select number of offshoreclam leases off Florida’s Gulf Coast.
“Real-time” equipment, installed byUFIFAS’ Dept. of Fisheries and AquaticSciences and the Dept. of Agriculture andConsumer Services’ (DACS)/Division ofAquaculture, is transmitting data to theDivision’s web site:
www.FloridaAquaculture.comSo far, three of four sets of scientific
equipment have been installed nearcommercial clam culture leases. One islocated on the Gulf Jackson lease, anotheron the Horseshoe Lease. Both are highdensity leases located near Cedar Key.A third unit is in the Aquaculture Use Zonenear Sebastian and a fourth unit isscheduled for the Charlotte Harbor area.Installation of the equipment is an integralcomponent of CLAMMRS (Clam LeasingAssessment, Management and Modelingusing Remote Sensing).
CLAMMRS is a four-year study by UF/IFAS’Dept. of Fisheries and Aquatic Sciencesand the Dept. of Environmental Engineering,with the goal of developing a productionmodel that identifies optimum clam farmingpractices and monitors changes in theirnatural food abundance and quality. Themodel, along with an improved understand-ing of hard clam nutrition and physiologicalrequirements, will help identify optimumsites for leases. The data can also beused by farmers to document crop losses,should they occur, for financial assistance.
Workshops will be held this Spring, byUF/IFAS’ Shellfish Aquaculture ExtensionProgram and DACS’ Division of Aquaculture,to describe the value and practicalinterpretation of this information. Also, theDivision is seeking commercial clamfarmer’s comments on how best topresent the information on their web site.
You’ve got sick fish on your hands.Who do you call? The followingindividuals are a good place to start:
Commercial Fish Farm ProductionDr. Roy YanongUF Tropical Aquaculture Lab / RuskinCall 813/671-5230 x [email protected]
Pet Fish and KoiDr. Allen RiggsUF College of Veterinary Medicine352/392-4700 x [email protected]
Game and Recreational FishDr. Ruth Francis-FloydDept. Fisheries & Aquatic Sciences/Gainesville352/392-9617 x [email protected]
Ruth Ellen Klinger352-392-9617 x 230Dept. Fisheries & Aquatic Sciences/[email protected]
Exotic FishRemovedfrom UFCampus Pond
Dept. of Fisheries andAquatic SciencesGainesville
Lesl
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Despite early morning rain and chillyconditions, a crowd of 455 anglersconverged on the ponds at the UF/IFAS
Department of Fisheries and AquaticSciences, for the fourth annual Fishing ForSuccess (FFS) Law Enforcement AppreciationDay. The February 16 event was the first ofmany FFS Family Fishing Days scheduledfor the coming months, and the fishing wasfast and furious throughout the morning.
This first FFS event of the year held a newexciting attraction. Watson Construction andother local businesses recently combined effortsto construct a new half-acre pond for FFS, tocompliment its many quarter-acre ponds.
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The new pond was built to replace theone-acre pond on USGS property, whichhad previously been used for fishing events,but is now off-limits to the public, due to theevents of Sept. 11.
In preparation for this year’s events, thenew pond was stocked with hundreds oflarge catfish (up to 30 pounds), nearly 1,000sunshine bass, and thousands of bluegills.
The Florida Fish and Wildlife ConservationCommission (FWC) donated sunshine bass,and the catfish and bluegills were movedfrom the old USGS pond to their new home.FFS staff are hoping to raise the necessaryfunds to build a handicap-access dockadjacent to the new pond in the near future.
On Feb. 16, scores of kids hurried out tothe new pond and the result was continuousfishing action punctuated by the screamingof overloaded reels and excited children.Several big fish were hooked briefly, but noone landed any of the 25-30 pound catfish.
Little Nikki Bennett, age 4, captured the“most fish” trophy by reeling in 68 bluegillsand sunshine bass in three hours, with onlyminimal help from her father Greg.
In addition to its Family Fishing Days,FFS also hosts many educational field tripsfor area schools and church groups. Lastyear, more than 9,800 people participated inFFS programs, and attendance is expectedto increase again this year.
New Pond A Big Success
The new, bigger fish pond will certainlyhelp absorb some of the fishing pressure.Somewhere in that new pond lurks “GeneralSherman,” a monster 30-pound catfish. Withthe standing FFS policy of catch and release,“The General” will surely give more than afew youngsters the fight of a lifetime in thecoming years. Tom Glancy
Fishing for Success Coordinator Tom Glancystocks the new fishing pond at UF’s Dept. ofFisheries and Aquatic Sciences.
Sean Phinney, age 11, won the trophy forBiggest Fish with a 16.1-pound channelcatfish, which he managed to land in spite of aseparated shoulder. WaterWorks editor JoeRichard wrestles with the brute.
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lorida lake fisherman haveoften wondered why the blackcrappie, a popular panfish, isabundant one year and notthe next. Do overall crappie
populations change that much? It wouldseem so.
Recent studies conducted by UF/IFASfisheries researchers indicates thatFlorida’s black crappie fishery fluctuatesconsiderably due to a highly variablerecruitment each year. (“Recruitment”refers to the production and survival ofyoung fish.) This variation contributes to a“boom and bust” fishery later whencrappie grow large enough to be caughtby anglers.
Dr. Mike Allen and his team of graduatestudents at UF’s Department of Fisheriesand Aquatic Sciences have been investigat-ing black crappie recruitment for the lastfive years in Florida, with the followingfindings:
Winter severity may influence blackcrappie recruitment.
For example, in Lake Wauberg in northcentral Florida, graduate student Bill Pinefound that early-hatched black crappie
that were subjected to cold water tempera-tures (e.g., resulting from a late-seasoncold front), experienced slower growth andhigher mortality, compared with late-hatchedfish in the same lake.
Black crappie growth is dependent ontheir density in some lakes.
Graduate student Kevin Dockendorffound that high densities (number of fish
per acre) of young blackcrappie in Lakes Lochloosaand Wauberg led to slowerfish growth, causing thesefish to take much longer,three to four years, to growbig enough to be caught.
Conversely, in the years2000-2001, young blackcrappie in Lake Tarpon hadlow densities and the fishgrew quickly, requiring onlytwo years to grow toharvestable sizes. Theseobservations have importantimplications for the blackcrappie fishery. In lakes withhigh densities, fishery
CrappieRecruitmentVaries Widely
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UF/IFAS Fisheries and Aquatic Sciences,Aquaculture, and Pond Management Update (continued)
managers may be able to ease harvestregulations by increasing bag limits.
That way, anglers can help reduce fishnumbers and hopefully increase fishgrowth. Lakes with low-density popula-tions could be managed with stricter baglimits that will, in turn, help preserve thelow numbers of fast-growing fish, eventu-ally building a quality fishery.
On the subject of crappie, a long-termcooperative study is now being conductedwith the Florida Fish and Wildlife Conser-vation Commission and the UF/IFAS FloridaLAKEWATCH program.
LAKEWATCH volunteers monitor waterquality on the lake they live on, and sendin samples to the University each month.Participating volunteers will harvest crappiefrom 15 Florida lakes each autumn. Thegoal is to document trends in the numberof young fish as the years go by. Combinedwith water sampling, it’s hoped this studywill provide an indication of how changesin water levels and aquatic plant growthmay also be influencing this fishery inFlorida.
Dr. Mike Allen352/392-9617 x 252
Black crappie (Pomoxis nigromaculatus)
UF/IFAS grad students Kevin Dockendorf and Kristin Henryexamine a black crappie caught in their trawl on Lake Wauberg.
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Dear Frank,Your observations of numerous dead
and dying pleco catfish over the wintermatch those reported by fisheriesbiologists and the public. These fishesare tropical in origin and cold wintertemperatures will cause partial or total kills.
Florida has several established exotic(i.e., foreign) fishes, including plecocatfish. Plecos belong to the SouthAmerican fish family Loricariidae, thearmored suckermouth catfish. Membersof this family are often called plecos inthe aquarium fish trade. Florida hasmembers of at least two genera,Hypostomus, armored suckermouthcatfish, and Pterygoplichthys, sailfincatfish. The sailfin catfish are morewidespread and occur in much ofpeninsular Florida, including the upperSt. Johns River and west coast streamsnorth of Tampa Bay, southward to thecanals of southeast Miami-Dade County.The range of plecos has increased inFlorida in recent years and, as you haveseen, they may reach high densities.
As a group, plecos feed mainly onalgae and detritus (organic material)from the bottom. Some species are more
carnivorous than others, but the speciesestablished in Florida mainly eat this typicalpleco diet. I have maintained plecos of variousspecies in aquaria and also observed themfeeding on shrimp pellets, other fish foodpellets, dead fish, and fish eggs. In mostcases, cichlid fishes are able to successfullyraise young in the presence of plecos, but anoccasional individual pleco may develop ahabit of eating undefended or exposed fisheggs. This behavior is also found in manytypes of fishes (e.g., native sunfish Lepomisspp.). Moreover, food items of captive fish arenot necessarily reliable indicators of diets innatural habitats. For example, nearly any fishlarge enough will eat the small easternmosquitofish Gambusia holbrooki in anaquarium, regardless of normal food selectionin the field.
Like you, I have often wondered about therole of plecos as nest predators of exoticcichlids and native sunfishes in Florida.Nevertheless, based on a fair amount ofaquarium observations and limited fieldobservations, I suspect that plecos may not bea significant limiting factor to nesting successof these fishes. Even in confined aquaria,cichlids in particular seem quite capable ofnest defense against plecos. I have even hadplecos injured or killed by nesting cichlid parents.On the other hand, nighttime nest predationcould occur. The fact is that no one hasresearched this topic, an undertaking thatwould require carefully controlled laboratoryand field experiments.
You have also identified a perceivedproblem, namely reduced harvest of fish fromFlorida lakes, and suggested a mechanism toexplain it — egg predation by plecos reducingfish recruitment. In science, we call this ahypothesis, a testable possible explanation foran observed phenomenon. First, we wouldneed to clarify if the problem is real or justapparent by reviewing historic fish and fisherydata and conducting research to assesscurrent fish populations. If the problem is real,we move to the next step. According to thescientific method, we would make predictionsbased on this explanation and devise tests toattempt to disprove this hypothesis. That isright, attempt to disprove it. We do not provehypotheses in science, but gain confidence inan explanation based on numerous failedattempts to demonstrate that it is false.
What else may be a cause of thedecline of a fishery?
Numerous possibilities come to mind -drought, muck build up, excessive aquaticplants, summer fish kills due to low dissolvedoxygen, lack of food for larval or juvenilefishes, overharvest, etc. You see, there aremany possible explanations that would requirestudy, not just plecos eating fish eggs.
Although exotic fishes have been prominent
Dear Editor,Below is a photo I took of a
plecostomus from Lake Marian atKenansville, Florida last year ...whilestopped there, I noticed several fishbelly-up and others dying in the smallpockets of water in the almost drycanal. I walked over and found not afew, but hundreds of these fish dying.(It was a few days after the coldestweather last year in Florida).
We then traveled a mile or two toLake Jackson. While there, we foundhundreds of dead or dyingplecostomus. This caused me towonder about other areas, as it wasobvious that Kissimmee and its canalsare infested with them. Two days laterwe took a trip to the Peace River atZolfo Springs. It was also down verylow, and we found many dead anddying plecostomus there. We thentraveled to Arcadia, and it was thesame there.
I raised two of these fish in a 110-gallon aquarium to adult size. Whenmy cichlids laid eggs in the aquarium,the plecostomus would eat the eggs ifpossible. Since the pleco has naturalarmor and a taste for fish eggs, is itpossible the deterioration of fishpopulations in Florida lakes is relatedto these voracious catfish?
Frank Hamill
in the state since the 1950s, relativelyfew researchers have studied them. TheFlorida Fish and Wildlife ConservationCommission (FWC) has regulatory andenforcement authority over exotic fishesin open waters and has for many yearsmaintained a monitoring and researchprogram in south Florida. Recently, UF’sDepartment of Fisheries and AquaticSciences of the University of Florida, theU.S. Geological Survey, Florida Interna-tional University, and individual research-ers in other institutions are directing efforttowards exotic fishes in Florida.
The release of non-native fishes intoopen waters in Florida is illegal, and theFWC attempts to eradicate newintroductions if possible. Once an exoticfish becomes established, however, it isgenerally not feasible to attempteradication. It is clear that pleco catfishare firmly established in Florida andbeyond eradication.
Many people assume that exoticfishes have caused widespread harm toFlorida’s native fishes. Contrary to thisopinion, there is almost no scientificdocumentation that exotic fishes havecaused such harm. It is an unfortunatefact that little research has beenconducted concerning interactionsbetween native and exotic fishes inFlorida. On the other hand, there hasbeen an accumulation of large amountsof qualitative fishery data and somequantitative data that is useful forassessing the overall status of nativefish populations in areas affected byexotic fishes.
The conclusion from these data isthat widespread catastrophic effectshave not occurred. This is not to say thatexotic fish are “good,” nor are theyinherently “bad.” Nearly everyoneagrees that exotic fishes are generallyundesirable and that much research isneeded todetermine theeffects thatexotic fishesmay have inFlorida’saquaticsystems.
Jeff HillUF/IFASGradute
Fellow
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The Institute of Food andAgricultural Sciences is an EqualEmployment Opportunity —Affirmative Action Employerauthorized to provide research,educational information and otherservices only to individuals andinstitutions that function withoutregard to race, color, sex, age,handicap or national origin.Inclusion of material in thisnewsletter does not constituteendorsement, nor does exclusionrepresent censure of any item,organization, individual, orinstitution by the University ofFlorida/Institute of Food andAgricultural Sciences.
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SUBSCRIPTION FORM
For a free subscription to WaterWorks please complete the following formand send it or fax it to the address below.
Editor / WaterWorksUniversity of FloridaDepartment of Fisheries and Aquatic SciencesPO Box 110600Gainesville, FL 32611-0600Phone: 352/392-9617 ext. 225 Fax: 352/392-3672E-mail: fishweb@gnv. i fas .uf l .eduWebsite: http://fishweb.ifas.ufl.edu/
In an ongoing quest to bridge theinformation gap between the scientificcommunity and Florida’s citizenry, UF/IFAS’ Florida LAKEWATCH programhas assembled a series of informationcirculars designed to provide anintroduction to the terminology andconcepts used in water management.
A Beginners Guide to WaterManagement — The ABCs(Circular 101) Formatted as a glossary, this bookletprovides definitions and additionalinformation for much of the terminologyused in water management. Enhancedwith dozens of black and white photos,the circular is 39 pages in length, coveringsubjects from A to Z (i.e., algae, averageplant biomass, limiting nutrients, potassium,trophic state, and water quality — to namea few).
Now available on the UF/IFAS EDISwebsite: http://edis.ifas.ufl.edu/fa078
A Beginner’s Guide to WaterManagement — Nutrients(Circular 102) Nutrients are substances required by allorganisms for growth, and they’re found inevery aquatic system. They are also the
Now Available!Beginner’s Guides to Water Management
object of much discussion by lake managers andthe general public, who are concerned aboutthe influence nutrients sometimes have on thegrowth of algae and/or aquatic plants. Writtenfor a lay audience, this information circular isan ideal reference booklet for students and/orprofessionals interested in water management.It’s thirty-two pages in length, with manysupporting graphs and photos. Now available on the UF/IFAS EDISwebsite: http://edis.ifas.ufl.edu/fa079
A Beginner’s Guide to WaterManagement — Water Clarity(Circular 103) Water clarity is one of the most notice-able attributes of a waterbody. In Florida, awide range of water clarity occurs naturallyin lakes and waterbodies. This booklet is 33pages in length and includes numerousphotographs and figures. Topics include:measuring water clarity and what affects it;the relationship between water clarity andbiological productivity; and techniques usedfor managing clarity in lakes. Mathematicalmodels are also introduced as a way ofpredicting water clarity in lakes.
Now available on the UF/IFAS EDISwebsite: http://edis.ifas.ufl.edu/fa080
Printed copies are available by contactingyour local UF/IFAS Cooperative ExtensionService or from the LAKEWATCH programitself. (Quantities may be ordered at cost.)They may also be downloaded for free byvisiting the UF/IFAS EDIS website addressesprovided here or from the Florida LAKEWATCHwebsite listed below:
