differences in oxygen consumption and ammonia

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Aqua cultur e, 40 (1984) 183-187Elsevier Science Publisher s B.V.. Amst erda m -Printed in The Neth erlan ds

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Short Comm un icat ionDIFF ERE NCE S IN OXYGEN CONSUMP TION AND AMMONIAPRODUCTION AMONG AMERICAN ELVERS (ANGUILLA ROSTRATA)

MARGIE LEE GALLAGHER, EMILIE KANE and J ENNI FE R COURTNEYEast Carolina Universit y, Greenville, N C 27834 (U.S.A .)(Accept ed 23 Febr ua ry 1984)

ABSTRACTGallagher, M.L., Kan e, E. and Cour tn ey, J ., 1984. Differen ces in oxygen consum pt ion

an d amm onia production am ong American elvers (Anguilla rostrata). Aquaculture,40: 183-187.Oxygen consump tion an d amm onia production in elvers of varying growth rat es

were stu died. The allometr ic equat ion describing th e relationship between oxygen con-su mpt ion an d weight is y = 0.638 x0.5*5, wher e y is th e oxygen consu mpt ion (mg/h)an d x is th e mass (g). The weight specific allometr ic equat ion for th e relationship be-tween am monia excretion an d weight is y/x = 0.0129 x.~. Slow growing elvers wer efoun d to have high er res pira tory ra tes (0.737 mg 0, h- g-) th an would be expectedfor their size.

The capt ur e an d cult ur e of youn g elvers ar e well esta blished comm er-cial pr actices in ma ny coun tr ies (Forr est, 1976). Un fort un at ely, up to50% of a ll capt ur ed elvers ar e consider ed to ha ve no comm ercial valuedue to their slow growth rate. If the factors which result in the differencesin ra te of growth could be determ ined, th e success of comm ercial eel far m-ing could be subst an tia lly enh an ced. Th is stu dy examined one criticalaspect of differences in growth ra tes, specifically differen t met abolic r at es.For this determ inat ion, both oxygen consu mpt ion and am monia produc-tion were measured.

Elvers, capt ur ed from North Car olinas Pamlico Soun d in th eir spr ingmigra tion, were fed ad libitum for 6 mont hs u nt il differences in growthra te were appa rent . Th e elvers were then divided int o four weight clas-sificat ions: Group 1 - 300 mg, Group 2 - 700 mg, Group 3 - 1000 m g,Group 4 - 2500 mg.

Oxygen consum pt ion was mea sur ed at 23C in a st erile 300 m l closedsystem u sing an Orion oxygen electr ode. Oxygen r eadings were ta ken atth e beginning an d end of a 30 min period, an d compa red with th ose ofa cont rol closed system without elvers. All elvers were first acclimat ed

0044-8486/84/$03.00 0 1984 E lsevier Science Pu blishers B.V.


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to the experimental conditions of handling. Eels were fasted for 18 h be-fore measurements were taken. Oxygen consumption was calculated asmg g- h-. The relationship between O2 consumption and mass was cal-culated using log transformation of data. Ammonia production was meas-ured in samples of water taken from the closed system at the end of the30 min test period. The method of Solorzano (1969) was used to deter-mine NH4 f 0.001 ppm.

Mean oxygen consumption (mg g- h-l) and ammonia production foreach group of fasted elvers are given in Table I. Both oxygen consump-tion and ammonia production decreased on a per gram basis as total weightincreased.TABLE IMean oxygen consump tion and amm onia production in fasting elvers (Anguilla rostrata)of varying growth ratesWeight Oxygen consump tion Ammonia production(mg) (mg g- h-l) (mg g- h-)

279 f 30a 0 .647 f 0.033a 0.019 f O.OOla722 r 121 0.542 f 0.009 0.025 + 0.003

1147 f 134 0.340 * 0.035 0.006 + 0.00032493 * 204 0.247 f 0.019 0.007 * 0.0002aStandard error of the mean.

The range of ammonia excretion rates (0.007-9.019 mg g- h -) is with-in the range of those reported in the literature for fish (0.009-0.035 mgg- h-) (Brett and Groves, 1979). Ammonia excretion rates show a weight-dependent relationship similar to that for oxygen consumption. The weightspecific allometric equation for this relationship isy/X = 0.091929 Xo*465 (r = 0.49)where y = ammonia excretion, and x = weight. The weight exponent issimilar to that determined by Gerking (1955) (W*54), but lower than thatcalculated for starving carp (Woeg) by Iwata (1970), or by Savitz (1969)(W-97) for 10-100 g blue gill. However, Savitz (1969) and Iwata (1970)point out that variations in ammonia excretion may be influenced by nu-tritional and thermal history.

The oxygen consumption data fit the allometric equationy = 0.638 xo.528 (r = 0.95)where y is oxygen consumption (mg/h) and x is mass (g). The weight spe-cific allometric equation isy/x = 0.385 xo*46o (r = 0.93)


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Oxygen consumption data in this study are compared with literaturevalues for other fish species in Table II. Tarr and Hill (1978) reportedthe oxygen consumption of southern African elvers. Using their equationsfor inactive and active eels, one obtains a range of O2 consumption of0.235-0.494 mg g-,h- for 0.3 g elvers, and 0.102-0.271 g O2 g-l h-i for2.5 g elvers. The values obtained in the current study are in the upperrange (active) for both 0.3 g (0.737 mg g- h-) and 2.5 g (0.256 mg g- h-l)elvers, although the elvers used were not active as defined by Tarr andHill (1978).Egusa (1958) determined oxygen consumption of Anguilla juponicain eels ranging from 5-300 g wet weight. When the data are convertedfrom ~1 to mg, the value (0.247 mg g- h-l) in this study for 2.5 g elvers iscloser to the value (0.260 mg g- h-l) estimated from Egusa (1958) than thevalue (0.494 mg g- h -) estimated for 0.3 g elvers. This indicates that slowgrowing elvers (0.737 mg g- h-l) may have a higher metabolic rate thanwould be expected.

When Caultons (1978) respiratory equation for Surotherodon mossam-bicus is extrapolated to 2.5 g fish, the result (0.274 mg g- h-) is similar toactual O2 consumption for 2.5 g (0.256 mg g- h-) found in this study.However, if Caultons (1978) data are further extrapolated to 0.3 g fish,the expected oxygen consumption rate is lower (0.568 mg h- g-) than thatwhich was obtained (0.737 mg O2 h-l g-) in the current study. Also, ifrespiratory data obtained for Tilupiu mossumbicu (Mironova, 1974) areused to calculate expected values for 0.3 and 2.5 g fish, 0.563 mg O2 h- g-and 0.318 mg O2 h- g- are obtained respectively. The predicted value forthe slower growing fish is again smaller than that which is obtained ex-perimentally (0.737 mg h- g-l).

The results of this study indicate that slow growing elvers may havehigher metabolic rates than would be predicted for their size. Higher met-abolic rates may indicate inefficient use of nutrients, and/or an increasednutrient requirement. This inefficiency might be overcome by higher feedingrates and possibly hormonal treatment.ACKNOWLEDGMENTS

This work was sponsored in part by the Office of Sea Grant, NOAA,U.S. Department of Commerce, under grant number NA81AA-D-00026,and by a grant from the East Carolina Faculty Research Fund.

REFERENCESBret t, J.R. an d Groves, T.D.D., 1979. Ph ysiological ener getics. In: W.S. Hoar , D.J. Ran dall

an d J.R. Bret t (Editors ), Fish Ph ysiology VIII. Acad emic Pr ess, New York, NY, pp.280-352.


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Caulton, MS., 1978. The effect of tem pera tu re an d mass on rout ine meta bolism inSarotherodon (Tilapia) mossambicus (Peter s). J . Fish Biol., 13: 195-201.

Egusa , S., 1958. On th e oxygen consu mpt ion ra te of pond-cultu red eel, Anguilla japonica.J pn . J . Ichth yol., 7: 49-56.Forr est, D.M., 1976. Eel Capt ur e, Cultu re, Pr ocessing an d Mark eting. Page Bros. (Nor-wich, MA) Ltd., 205 pp.

Gerk ing, S.D., 1955. En dogenous nit rogen excret ion of bluegill sun fish. Physiol. Zool.,28: 283-289.

Iwata , K., 1970. Relationsh ip between food an d growth in youn g crucian carp s, Carassiusauratus cuuieri, as deter mined by th e nitr ogen balance. J pn. J . Limnol., 31: 129-151.

Mironova, N.V., 1974. The ener gy balan ce of Tilapia mossambica. J . Ichth yol., 14: 431-438.

Savitz, J ., 1969. Effects of tem pera tu re an d body weight on endogenous nitr ogen excre-tion in the bluegill sunfish (Lepomis macrochirus). J. Fish. Res. Board Can., 26:1813-1821.Solorzano, L., 1969. Determ inat ion of amm onia in na tu ra l wat ers by th e phen ol-hypo-chlorite method. Limnol. Oceanogr., 14: 799-801.

Tar -r, R.J .Q. a nd Hill, B.J ., 1978. Oxygen consu mpt ion, food a ssimilat ion an d en ergycont ent of south ern African elvers (Anguilla sp.). Aquacultu re, 15: 141-150.

differences in oxygen consumption and ammonia

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