Cai, Zhengwei

Curtis, Lawrence R.

Oregon State University. Water Resources Research Institute

Undetermined

ScholarsArchive@OSU

Bioenergetics of Grass Carp :Water Quality ImplicationsbyZhengwei CaiLawrence R. CurtisWater Resources Research Institute-- -Oregon-State University-- -Corvallis, OregonWRRI-101	' August 1988ffiOII 2ICS OF LASS CARP :WATER QUALITY IMPLICATICtiSby7hengwei Cai and Iawrenoe R. CurtisDepartment of Fisheries and Wildlife, Oregon State UniversityFinal Technical Completion ReportProject Nuttier G1444-06S .itted toMilted States Department of the InteriorGeological SurveyReston, Virginia 22092Project Sponsored by :Water Resources Research InstituteOregon State UniversityCorvallis, Oregon 97331The research on which this report is based was financed in part by th eDepartment of the Interior, U .S . Geological Survey, through the OregonWater Resources Research Institute .The contents of this publication do not necessarily reflect the viewsand policies of the Department of the Interior, nor does mention oftrade names or commercial products constitute their endorsement by th eUnited State Government.WRRI- 101	August 1988APSIRACTTriploid grass carp (TGC) were introduced into Devils Lake (nea rLincoln City, Oregon) during 1985 for 'aquatic weed control . Use of thisspecies as a biological pest control agent in the Pacific Northwes traised some controversy . Most previous U .S . introductions were withdiploid fish in the , Southeast and Midwest . Information on comparativebioenergetics of diploid and TGC under Northwestern environmenta lconditions was not available . Consumption rates of problem macrophyte spresent in Oregon coastal lakes at temperatures found in such water swere unestabli'shed . The proportion of ingested energy utilized by TGC(i .e . assimilation efficiency) under such conditions was also unknown .This latter point was of concern since law assimilation efficiency a thigh consumption rates has been associated with increased availabl enutrient concentrations and blooms of bacteria and . algae.Bioenergetics of diploid and TGC were not significantly different .Relative consumption rates for the problem aquatic macrophytes teste dwere elodea > water milfoil >> coontail at 20°C . Consumption of elodeaby TGC increased 4-fold between 14 and 24°C without significant effect son assimilation efficiency, which averaged 45% on an energetic (caloric )basis and 40% on a dry weight basis. Near the annual high temperaturefor Devils Lake (19°C) . TGC consumed 25% of their body weight per day o felodea and increased their body size 24% in 32 days . Temperatures ofNorthwestern lakes may protect against algal and bacterial bloom sassociated with over-grazing by TGC. Lower consumption rates forcoontail, and to a lesser extent water milfoil, than elodea may resultin a shift in abundance of aquatic weeds .Il	JCITONProblemMany of Oregon's coastal lakes, including Devils Lake (near LincolnCity, Oregon), are undergoing eutrophication linked to excess influx ofnutrients fruit a variety of sources including pollution film septi csystems and livestock. Aquatic macrophytes obstruct boating, impairfishing, and encourage siltation resulting in greatly diminishe drecreational potential . Control technologies for aquatic weeds have notbeen implemented successfully and public pressure led to experimenta lintroduction of triploid grass carp . This action was controversial fortwo primary reasons. (1) Over grazing by grass carp in certain watersand subsequent increases in nutrient levels associated with incompletedigestion of ingested plants lead to blooms of bacteria and algae (Kogan1974 ; Menzel 1974) . These organisms can produce conditions (e .g .noxious odors and surface layers) more unpleasant than aquati cmacrophytes. (2) Aquatic vascular plants provide forage for waterfowl .Heavy grazing by grass carp could substantially reduce the standing cropand thereby eliminate habitat .Careful evaluation of grass carp as a weed control technology i sessential due to the scope of Oregon's lake eutrophication problem andthe scarcity of data available to evaluate potential effects of thes efish on Northwestern lakes .Research ObjectivesIn order to rehabilits a eutrophic lake grass carp must consumesufficient plants to reduce the standing crop, and the energy should b e1fixed in fish tissue to remove it as a source for growth of undesirableorganisms (e.g., bluegreen algae and bacteria) . The desired amount ofreduction in plants will depend upon perceived value of other organism swhich utilize aquatic vascular plants as a resource (e.g., waterfowl) .Regardless of the desired level of weed control, estimates of grass carpconsumption and growth are necessary to estimate stocking rates for atarget standing crop . Consumption and assimilation rates for triploidgrass carp feeding on problem macrophytes in Oregon lakes are probablyimpossible to define in the field. Our laboratory experiments provid ean empirical basis for understanding bioenergetic relationships betweenthese animals and Northwestern lake environments .Related WorkEcological research on responses of aquatic macrophyte and anima lcommunities after stocking of triploid grass carp is ongoing in Devil sLake, Oregon . This work is directed by Dr. Gilbert Pauley of theUniversity of Washington Cooperative Fisheries Unit .Mitzner (1978) reported decreased mean nitrites, nitrates, POD an dturbidity and increased alkalinity after introduction of grass carp a tRed Haw Lake (Iowa) . He also found mean concentrations of organic an dinorganic phosphate gradually increased but not to a statisticallysignificant extent. Lembi et al . (1978) reported increased potassiumlevels in test ponds . Nitrogen and phosphorus levels were also higher ,but the increase was not statistically significant . Increasedavailability of nutrients from grass carp grazing can lead to excessiv ephytoplankton blooms . Shireman (1984) states stocking rate is a n2essential variable in occurrence of such problems . No report of impactof triploid grass carp on water quality has been published . Nolaboratory data are available for conditions patterned to reflect th eenvironments of Northwestern lakes .EXPERIMENTAL DESIGN AND METHODSRationaleOne objective of this research is increased understanding of th ecapacity of grass carp to fix . the energy of aquatic macrophytes int otheir tissues . Removal of plant biomass from eutrophic aquatic system sis the goal of grass carp introduction . Energy consumed as plantbiomass but not fixed in fish tissues is 'excreted and available fo rsubsequent plant growth, particularly algae and bacteria . Estimation ofgrass carp efficiency in assimilation of ingested macrophytes can helpexplain impacts of their introduction into eutrophic aquatic systems .The second major objective of this research is improved understanding offood consumption and growth of triploid grass under conditions i nNorthwestern lakes . Food type and temperature were the two parametersstudied. Such data are necessary for estimating stocking rates requiredfor a given level of weed control .MethodsWe fed diploid and triploid grass carp the three principal aquati cmacrophytes present in Devils Lake . Fish were donated by OsageCatfisheries (Osage, MD) . Additional fish were fed a vial catfishfeed to serve as a control . The rates of food consumption and3efficiency of conversion of ingested material were determined attemperatures relevant to Oregon coastal lakes for triploid fish .Water milfoil (Myriophyllum ssp) coontail (Ceratophyllum demersum)and elodea (Elodea canadenis) were selected based on food preferenc estudies with triploid grass carp conducted by the University o fWashington Cooperative Fisheries Unit (personal comwnication) . Watercontent, protein, fat, ash, and cellulose in each diet were measured bythe AOAC methods (1975) . Energy content of materials was determined byan oxygen bomb calorimeter . Before feeding, fresh aquatic plants werewashed to remove adherent sediments and encrusting organisms and the nblotted and weighed . Uneaten food and feces in each aquarium wer ecollected and weighed before new food was added . The uneaten food wasalso washed, blotted, and weighed to calculate food consumption . Thecollected feces were dried and used to measure protein, fat, ash, an dcellulose by the same method as used in diet measurements .Food consumption rate (mg per gram of fish per day), growth rat e(mg of weight gain per gram of fish per day), assimilation efficiencyand gross growth efficiency (mg of weight gain per mg of food ingested )were calculated (Warren 1971) .Assimilation efficiency was calculated using cellulose as areference (Buddington, 1980) .Assimilation efficiency =1 - percentage of cellulose in fecesar	Gross growth efficiency	 rate	ency = food consumption rat epercentage of cellulose in food4Bcenb calorimetry was-used to quantitate the assimilation and. wasteof energy consumed. The basic bioenergetic too- of Warren (1971) wasapplied .STS AND SIGNIFICANCETable 1 summarizes the composition and energy content of variou sdiets used in this study. Water contents of all plants were around 90%while that for the caunercial feed was about 10% .. As .would be expectedthe commercial diet contained more protein than the aquatic plants .Elodea leaf did have a rather high protein content however . Lipidcontents of all plants tested were higher than the . commercial diet .Elodea had about twice the lipid of water milfoil and coontail wa sintermediate. On a dry weight basis, energy contents of all dietstested were comparable .The consumption, growth rates, and assimilation efficienciesiOfdiploid and triploid grass carp fed the above diets at 20°C are'in Table2 . Relative consumption rates on a wet weight basis for both diploi dand triploid fish were elodea > water milfoil >> coontail >>> catfis hfeed. When food consumption rates were expressed on a dry weight basisabsolute differences between catfish feed and plants were greatl ydecreased while relative rates were little changed. It is important tonote that relative growth rates were elodea > water milfoil .> catfishfeed >> coontail for both diploid and triploid fish. Assimilationefficiencies decreased in the order : catfish feed > elodea >> watermilfoil > coontail for both diploid and triploid fish . Taken togetherour data indicated no differences between bioenergetics of diploid an d5triploid grass carp fed different diets. This suggests literature ondiploid fish may be useful in understanding bioenergetics of triploi dgrass carp.We next examined the effect of environmental temperature onconsumption, growth, and assimilation efficiency of triploid grass carpfed elodea (Table 3) . Consumption and growth rates increased from 14 . 4to 24 .4°C. Analysis of variance indicated assimilation efficiency, o nboth a dry matter and energy basis, remained nearly constant over thi srange. At higher consumption rates, however, fecal energy los sincreased with environmental temperature . At 18 .8°C (near the annualhigh temperature for Devils Lake) fish consumed about 25% of their bodyweight in elodea per day and grew 24% in 32 days . These data suggesttriploid grass carp can grad at modest rates under conditionsrepresentative of Northwestern coastal lake environments . Further ,since consumption rates more than double between 14 .4 and 18 .8°C highestgrazing rates should occur in summer .We next evaluated the relative benefit of diet type in growth o ftriploid grass carp between 14 .4 and 24 .4°C. At all temperatures growthrates decreased with time after changing the diet from elodea to catfishfeed (Table 4) . This effect was more pronounced at 14 .4 and 24 .4°C than18 .8°C. Consumption rates for catfish feed remained constant except at14 .4°C (Table 4), however feed conversion efficiency (Fig. 1) decreasedwithin 3 weeks after changing diet in all temperatures . Onset of thiseffect was most rapid at 18 .8°C. These data suggested triploid grasscarp will grow at higher rates over prolonged periods when consumin gelodea than commercial catfish feed. It therefore seems their nutrition6requirements should be met in Northwestern coastal lakes. Of the threeaquatic plants tested elodea had the highest Protein and lipid contests .Grass Carp fed elodea consumed more and grew faster than fish on an yother diet. Simple protein and lipid content alone may explain th eapparent higher quality of elodea as food for grass carp . More specificaspects of plant composition, for example amino acid consistuents o fproteins or fatty acid constituents of lipids, may likely contribut ealso.ConclusionsBoth diploid and triploid grass carp consumed the aquatic weedstested at the relative rates : elodea > water milfoil > coontail . On anenergy basis assimilation efficiency df triploid fish at 20°C was about40% for elodea and water milfoil, but 20% for coontail . Fecal energyloss increased exponentially with the amount of elodea consumed by grasscarp. Respective consumption and growth rates for triploid fish fedelodea increased about 4 and 5-fold between 14 and 24°C . Temperaturedid not effect assimilation efficiency over this range .Annual peak temperatures of 18-19°C occur in late summer in Devil sLake . Our laboratory data indicate triploid grass carp will consumeabout 25% of their body weight per day of their most preferred foo d(elodea) at 18 .8°C. Consumption-related reductions in assimilationefficiency do not occur at this feeding rate . Typical Northwesternenvironmental water temperatures may therefore protect against algal andbacterial blooms associated with over-grazing by grass carp . Lawconsumption rates and assimilation efficiencies for coontail and to amuch lesser extent water milfoil may result in afor aquatic vascular plants.ftspec8References1. AOAC. 1975 . Official Methods . of Analysis of the Association ofOfficial Analytical Chemists (William Horowitz, ed.) 112th ed .Washington, D .C. AOAC.2. Buddington, R .K. 1980 . Hydrolysis-resistant organic matter as areference for measurement of fish digestive efficiency. Trans . Am .Fish. Soc . 109,653 .3. Kogan, S .I. 1974 . Overgrowing of the Kara Kum Canal and same aftereffects of introducing the white amur into water bodies . Gidrobiol .Zh. 10 :110-115 . (In Russian) .4. Lembi, C.A. et al . 1978 . The effect of vegetation removal by grasscarp on water chemistry and phytoplankton in Indiana ponds .Am . Fish . Soc . 107(1) :161-171 .5. Menzel, A.V. 1974 . Clearing water with herbivorous fish . Proc.Eur. Wed. Res. Counc. Int. Symp. Aquat. Weeds. 4 :139-141 .6. Mitzner, L. 1978 . Evaluation of biological control of nuisanceaquatic vegetation by grass carp. Trans. Am. Fish. Soc.117(1) :135-145 .7. Shireman, J .V. 1984 . Control of aquatic weeds with exotic fishes .In "Distribution, Biology, and Management of Exotic Fishes" (ed.) by9W.R. Courtenay and J .R. Stanffer. Pp. 302-312 .8 . Warren, C .E . 1971 . Bioex	tics and growth .	Biology and WaterPollution Control, pp . 135-167 . W.B. Saunders Co ., Phil104cgipHrnNO81cocoNN0NHWO• 4 a6ON+ It-1coWO04a3ONNticotoNHr-1ONOOtIOHNHNtIOHO+ ItoNN▪ O IHmOcoNNNco• O1MonrNHPOTIONNONN I0U11ifIN N1+ 100 0*~~*IN oo100to (71aal a,gOwoiw ~	,t00	~• O('4	W J	N hd-	.P	R QaI	JH-.l Ul10 00I+ WI0 0l0 W ,Op l0IlO3 10 O01 (JlLO(~JlH .11.~N	H -a10 0OHv1001	100 0H W	O N'0 001 W O HIA1 2Table 3 . Consumption and Growth Rate of Triploid Grass Carpfed Elodea at different temperatures .Temp .	14 .4 0C	18 .8 0C	24 .4 0CFinal bodyweight (g) 86 .6+6 .4 96 .2+4 .8 116 .7+8 . 4Initial bodyweight (g) 80 .6+5 .2 77 .3+6 .6 82 .3+3 . 4Consumption(% of body weightper day *) 11 .0+0 .5 25 .2±0 .9 39 .9+2 . 1Instantaneousgrowth rate(% per day) 0 .21+0 .07 0 .72+0 .14 1 .06+0 .1 2Food conversionratewet food 50 .6 36 .9 35 . 4dry food 5 .39 3 .93 3 .7 7Digestionefficiency* *on dry matterbasis 41 .0+1 .8% 44 .2+2 .6% 38 .6+4 .1 %on energybasis 44 .6+1 .7% 49 .2+2 .3% 48 .8+3 .4%* Based on the total six fish in each aquarium . Results areexpressed as the mean of relative daily consumption + SE ove r32 days .** Based on measurements of cellulose content in three fece ssamples .1 3Table 4 . Consumption and Growth Rate of Triploid Grass Carpafter changing diet from Elodea to catfish food . * , .Date (days )Temp .Sept .14 to25	(12)Sept .26 toOct .6	(11)Oct .7 to 1 6(10 )GR 0 .68+0 .10 0 .51+0 .08 -0 .06+0 .0 814 .4 0CCR 112	(2 .50%) 100	(2 .25%) 83	(1 .94% )GR 0 .50+0 .26 0 .41+0 .05 0 .34+0 .1 118 .80CCR 164	(3 :12%) 145	(2 .77%) 153	(3 .13% )GR 1 .23+0 .07 1 .28+0 .10 0 .31+0 .0724 .4 0CCR 302	(4 .64%) 330	(4 .76%) 323	(4 .45%)	.* Results are means+SE for 4 fish .GR= instantaneous growth rate, % per day ;CR= consumption rate, gram of diet consumed during that perio d(% of body weight per day) .14 .Figure 1 . Feed conversion efficiency of grass carp before andafter diet change at various temperatures .EL-fed fish in 32 days, before diet change ;CP-fed fish in the first 12 days, after diet change ;CP-fed fish during the 13th to 23rd day, after dietchange ;CP-fed fish in the last 10 days, after diet change .r.1,15

Bioenergetics of grass carp : water quality implications

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Bioenergetics of grass carp : water quality implications

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