The above data clearly demonstrate selectivity in the Aureliu rmurita L. (Scyphozoa, Semaeostomae). Wiss. diets of the four colnrnon species that show predation Martin Luther Univ. HaBle-i$litter-aberg hfath. Naturwiss on other coelenterates. However. no predator was de- Reihe 33) : 479-482. M. pendent on a single prey species. Tt is difficult to evaluate HYMN, L. 2940. Ob5ervations and experiments on the physiology of medusae. Biol. Bull. (Woods Hole) 79: the degree of competition involved. Not only do the 282-296. four species vary in period of maximum abundance in LEBOUK,M. V. 1922. The food of plankton organisnas. J. Mar the bay but all four species will accept noncoelenterate Riol. Assoc. U.M. 12: 644-677. prey. This study will be extended to investigate preda- 1923. The food of plankton organisms HI. J. Mar. tion on other possible prey including fish larvae. Biol. Assoc. U.K. 13: 70-92. LC)C;INOVA,N. P., AND N. M. PERZOVA.1967. Some data on Acknowledgnie~zts- We are very grateful for the facil- ecology of feeding of pelagic Coelemterata in the White ities of the Pacific Biological Station, Nanaimo, B.C., where Sea. Issled. Fauny Morei 7415): 21-28. (In Russian) this study was carried out and the cooperation of the staff. ~~CCORMICK,J. M. 1969. Trophic relationships of hydro- Dr Z. Kabata kindly translated several Russian papers. Miss medusae in Yaquina Bay, Oregon. Northwest Sci. 43: Valerie Overend assisted in collection of specimens. The 207-2 14. project was supported by NRC Grant A2007 to M.N.A. PETIPA,T. S.? E. V. PAVLOVA,AND C;. N. MIRONOV.1970. The food web structure utilization and transport of energy by trophic levels in the planktonic communities, p. 142-167. It1 J. H. Steele [ed.] Marine food chains. Oliver and Boyd, AGASSIZ,L. 1862. Contribution to the natural history of the Edinburgh. 552 p. United States of America. Second Monograph. IV. PLOTNIKOVA,E. D. 1961. On the diet of medusae in the littoral MydroBdae 4: 183-372. pl. 16-35. of Eastern Murman, p. 153--156. I/? M. M. Kamshilov FOMBPS.E. 1848. A monograph of the British naked eyed [ed.] Hydrological and biological features of the shore medusae with figures of all the species. The Ray Society waters of Murman. Akad. Nauk USSR Kolsk. Fil. Publication, London. 104 p., pl. 1-13. (In Russian) FRASER,J. H. 1969. Experimental feeding of some medusae SOUTHWARD,A. 3. 1955. Observations on the ciliary currents and Chaetognatha. J. Fish. Res. Board Can. 26: 1743- of the jelly-fish AIIT~~~LIrmrifu L. 1. Mar. Biol. Assoc. U.K. 1762. 34: 201-216. C~REVE,W. 1970. Cultivation experiments on North Sea SVESPINIKOV,V. A. 1963. The feeding habits of jelly-fish as ctenophores. Helgol. Wiss. Meeresunters. 20: 304-317. possible rivals of the White Sca herring, Mosco\v Univ. 1971. Okologische U~~tersuchungenan Pleurobrtrcllitr Belmorsk. Biologichesk. Tr. 2: 246-249. (In Russian; piieus. 1. Freilanduntersuchurlgen. Helgol. Wiss. Meeie- English abstract) sunters 22: 303-325. ZELICKMAN,E. A. 1076. The biology of a little known neritic 1972. Okologische Untersuchungen an Pl~urobrctclriu hydromedusa Poi~.orchis kurufirroc~nsis (I'olyorchidae: pilrus. 2. Laboratoriumsuntersuchungen. Helgol. Wiss. Coelenterata). Tr. Inst. Okeanol. Altad. Nauk SSSR. 105: Meeresunters. 23 : 141-164. 210-213. (In Russian; English abstract) HUN~LEY,M. C., AND L. A. HOBSON.1978. Medusa predation ZELICKMAN,E. A., V. 1. GELFAND,AND M. A. SHIFKIN.1969. and plankton dynamics in a temperate fjord, British Growth, reproduction and nutrition of some Barents Sea Columbia. J. Fish. Kes. Board Can. 35: 257-261. hydromedusae in natural aggregations. Mar. Biol. (Berl.) HUSING,J. 0. 1956. Zur Frage der Ernahrung der Ohrenclualle 4: 167-173.

Leaf Litter Processing in a Regulated Rocky Mountain Stream

Depurtnzet~tof Zoology and en tor no log^, Coloru~loState Umivtlrsity, Fort Collins, CCd 80523, USA

Snron~,W. A., AND J. V. WARD.1980. Leaf litter processing in a regulated Rocky Mountain stream. Can. J. Fish. Aquat. Sci. 37:123-127. Processing of alder (Alrurs tenuijbliu) was investigated during autumn and winter to determine the influence of stream regulation on leaf litter processing. Study sites were the River below Granby and the Frasei. River, an unregulated tributary. Alder leaves (5-g units) were attached to bricks and placed in riffles. Lcaching controls were re- trieved after 48 h; thereafter five replicates were collected from each site after 17, 38, 52, and 66 d. There were significant differences (P < 0.05) in processing rates B-xtween sites. The loss rate coetiticient (X:) was much higher (X: = 0.0462) for leaves incubated in the regulated section

'Present address: Departmeiat of Biological Sciences, North 'Texas State University, Denton, TX 76203, USA. Printed in Canada (55676) Imprim6 au Canada (55676) CAN. J. FISH. AQUAT. SCI., VOL. 37, 1080

of the than for those in the unregulated tributary (k = 0.0235 1. The hypothesis that reductions in macroinvertebrate shredders would decrease processing rates of leaf litter in regulated streams was not supported by the results. The "winter warm" thermal regime below the reservoir seems to compensate for the virtual absence of shredder species apparently by enhanced microbial processing.

Kej, words: Colorado River. leaf litter, macroinvertebrates, , stream regula- tion, temperature

SHORT,R. A., AND J. V. WAI~D.1980. Leaf litter processing in a regulated Rocky Mountain stream. Can. J. Fish. Aquat. Sci. 37: 123-127 Dans le but de determiner l'influence du contrdle d'un cours d'eau sur la transformation de la litikre de feuilles dans un cours d'eau des montagnes Kocheuses, nous avons 6tudiC la transformation de l'aulne (Alnus terrrl{f'oliu) en automne et en hiver. Les recherches ont Ctl eb'fectuCes sur le fleuve Colorado, en aval du barrage Granby et sur la rivikre Fraser, un tribu- taire non contrale. Bes feuilles d'aulne (unites de 5 g) furent attachees h des briques et plackes dans des .maigres)) le 29 septembre. Des temoins de lessivage furent enleves aprks 48 h; par la suite, 5 reproductions furent recueillies h chaque site aprks 17, 38, 52 et 66 jours. 11 y a des differences signiticatives (P < 0,05) de taux de transformation entre les sites. Le coeficient de taux de perte (k) est beaucoup plus Cleve (k - 0,0462) pour des feuilles incubees dans la section contrdlee du fleuve Colorado que celles placees dans le tributaire non contr816 (k = 0,0235). Les resultats de cette etude n'appuient donc pas l'hypothkse que la diminution des macroinver- tCbrCs dechiqueteurs ralentit la transformation de la litikre vCg6tale dans des cours d'eau con- trdlCs. LC regime thermique de xchaleur hivernale. en aval du reservoir semble compenser l'absence virtuelle d'espkces dechiqueteuses par une transformation microbienne plus active. Received June 15, 1979 Re~ule 15 juin 1979 Accepted October 4, 1979 Accept6 le 4 octobre 1979 DETERMINATIONSof leaf litter processing rates have stream bottom was predominantlgl rubble in both study generated a great deal of information concerning stream sections. During the study period, discharge averaged 0.54 ecosystem strrlcture and function (e.g. Petersen and m"/sin the Colorado River and 0.53 m.'/s in the . Total dissolved solids (35.7 mdL: 65.4 mg/L) and Cumnlins 1974; et al. g75; Benfield et 1977) sedell methyl orange a1 kalinity ( I1.0 mg/L; 22.5 mg/L) values and have provided an experimental means to test vari- ,ere somewhat in the River. ous hypotheses (Reice 1974, 1977)- 'The leaf pack (53 .g/L; 43 rg/L) and pH (7.6: 7.4) exhibited similar method has also been used as a bioassay to determine values at both locations. There were, however, collsider- the effects of man's activities on streams (Triska and able differencs in water tenlperature (discused later) be- Sedell 1976; Gelroth and Marzolf 1978). One signifi- tween the regulated and unregulated streams. cant anthropogenic impact has been the construction Experimental procedures - Alder (Alties tenuifolia) leaves of numerous reservoirs on previously free-flowing were collected in September 1978 immediately prior to streams. Large may greatly physic'- abscissioll. The leaves were air-dried then oven-dried at chemical conditions of downstream reaches with re- 60°C for 48 h and weighed into 5-g units and strung on sultant changes in the diversity, density, and composi- monofilament line. A single- leaf nack was lashed to each tisn of the nlacrsinvertebrate fauna (Ward 1976a; brick and placed into a rime area of each stream on Sep- Ward and Stanford 1979). Since there is a selective tember 29. After 48 h, three replicate lcaf packs were re- elimination sf certain taxonomic and functional groups trieved from each site to serve as leaching controls. There- (Ward and short 19781, it was hypothesized that leaf after five replicates were collected from each site aAer 17, litter processing would be altered by stream regulation. 38, 52, and 66 d in the stream. At the time of collection the leaf pack was cut free of the brick and placed into a leaf pack The method was to determine the in- plastic bag containing 5% formalin. In the laboratory the fluence of stream regulation by dams on leaf litter pro- leaf Dack was thoroughlv rinsed with ta~water to remove cessing rate. accuiulated sedimen;, dried at 60°C for.48 h, and weighed (k0.1 g). Macroinvertebrates associated with the leaf pack Materials and nlethods - Study area - Study sites were were placed into 80% EtOH until identified and enumerated. on the Colorado River below and on the Dry weight of macroinvertebrates was determined follow- Fraser River, a major tributary unregulated by dams. Lake ing drying to constant weight at 60°C. No attempt was Granby is a large storage reservoir located 10 km northeast made to correct for weight loss during preservation. Water of Granby in the Rocky Mountains of northern Colorado. temperatures were monitored using maximum-minimum The dam is 91 m high and impounds 666 >i; 10"mm"of water. thermometers at each site. The confluence of the Fraser and Colorado rivers is 12 km below Granby Dam. A site on the Fraser River was selected Re,srrlrr- There were clear difference in pro- immediately upstream from Granby. Stlldy locations were at comparable elevations (2460 and cessing rates (Fig. On each date leaf 2420 a.s.l.) and exhibited generally similar conditions. packs from the Colorado River had less weight remain- woody vegetation consisted predominantly of wil- ing than those from the Fraser River. Analysis of lows (Salix spp.) and alder (Alnus tenuifolia) and the variance showed these differences to be significant (P < NOTES 125

followirlg log, trarlsforrnatian of the percent remaining Fraser River data in Fig. IA. This assumes that leaf pack processing Q Colorado River in streams follows an expc~nentialdecay model (Peter- sen and Carmmins 1974). These estimates are pre- sented below along with calculated times for 50 and 90% processing.

Site k 50', , 90' , Colorado River 0.0462 15 50 Fraser River 0.0235 30 98

The k values for both sites indicate rapid processing of alder leaf packs with the Colorado River loss rate coeficient approximately twice that of the Fraser River. Leaves with k values abovc 0.010 are considered "fast" species (Petersell and Charnrnins 1974). Alder leaf

8 Fraser River packs woalld be 90% processed in just 50 d at the o Colorado River Colorac%oRiver site, a rate of processing nearly equal to that obtained by Hart and Hawnliller (1975) for Alnu,~rllornhifolia leaves in a much warnner southern stream. Although numbers of macroinvertebrates per leaf pack were generally similar at the two sites (Fig. 1B), there were obvious differences in the species composi- tion (Table 1). Eight of the tam collected in the Frraser River leaf packs were not found in the Colorado River samples. Six traxa were ccdllected only from the Coloracls River. These diaerences undoubtedly relate to the effects of stream regulation (Ward and Short - 1978). 'Fhe most abundant species collected at both 2 17 38 52 66 sites was the mayfly Epb~cjrncrelluSnfreqzlens which ac- BAYS IN PLACE counted for 76% of the total nulllber of macroin- vertebrates in the Colorado Rives leaf packs and 34% FBC.I. A) Decornpc~sitionof alder Iaf packs in the Fraser in the Fraser River samples. Many taxa in the Colorado River and Colorado River, Colorado, September 29 thl-ough River leaf packs were present in very low numbers December 3, 1978. Mcan value e 1 s~:B) Colonization of (Table 1); often only 1 or 2 individuals were collected leaf packs by nlacroinvertekrates plotted as organisms per during the entire study period (e.g. Trl"coryt/zodes sp., dry weight of leaf pack remaining. Mean value 1 1 sn. Sk~zyal~rpnrallcln, PteronurceBlu ho8ia. Lepidostsma ~p.).This occurred to a much lesser degree in the 0.05) on each sampling date except day 38 (0.05 < Fraser River leaf packs. P < 0.10). Even losses due to Beaching exhibited sig- ,4ssignmcnt of the n-iacroinvertebrates to functional nificant differences between sites. Gelrsth and Marzolf groups (klerritt ant1 Cumr-ni~-ns1978) also reveals (1998) found that leaf packs apparently lost weight by drastic differences between the sites (Table 2). Col- leaching to a greater degree in a natural stream than a lectors were by far the dominant group in the Colorado channelized stream. These results are difficult tcd re- River leaf packs, m'linly due to the presence of large concile since leaching is thought to be a purely physical numbers of Eprhrmcrc~llu infrc.qaleras. Shredders were process unrelated to variables such as temperature much less important at the location below Granby Dam. (Petersen and Cun~mins1974). In the Fraser River loaf packs, the collectors formed Leaf packs collected from the Colorado River site the bulk of the biomass, but the shredder biomass value were >90% processed alter 52 d in the stream (Fig. was 10~that found in the Coloriido River samples. IA). Thus leaf packs were not again collected at this Alder leaves incubated in a small headwater stream in site. The Fraser River sarnples collected on January 7 Colorado (Short et al. 1980) had an even greater (day 100) co~lsistedonly of monofilament line as either shredder biot-a~iissthan the Fraser River s;amp%es,yet tho leaf packs had been cor-npletcly processed or were the 103s rate coeficient (k 0.0308) was less than that damaged by ice action. The leaf packs collected an this of the Colorado River below Granby Dan1 where date were therefore not included in the analysis. shredders were virtually absent. After accounting for leaching losses, linear regres- Minimum and maximum water temperatures recorded sion was used to estimate the loss rate ccbeficient (kb at intervals over the sampling period are shown below. 126 C.4N. J. FlSfl. AQUAT. SCI., VOL. 37, 1980

Time interval Colorado River Fraser River TABL~,2. Mean biomass of macroinvertebrate functional groups (mg/g leaf pack) collected in leaf packs over thc entire Oct. 1-0ct. 15 9.4-13.3 1.1-13.1 sampling period. + denotes ec.3 4.6-7.8 0 Functional group Colorado River Fraser River Dec. 3-Jan. 7 1.7-5.3 0 Coilectors Shredders The effect of impoundrncnt was to elevate fall and Predators winter temperatures and to increase thermal constancy Grazers (see Ward 1976b). Total Disctis.sio~-The results of this study do not support our hypothesis that reduction of shredders would re- sult in a slower processing of leaf litter in the regulated may be attributed. Weight loss of leaf litter often is stream. directly proportional to stream temperature (Anderson Temperate~reappears to be one factor to which the and Sedell 1979). The elevated fall and winter water differences in leaf processilag rates between the streams temperatures resulting from Lake Grantpy thus appear to provide an cxplanation for the higher loss rate co- efficient in the Colorado River. The '"winter warnl" TABLL1. Mean nurnbers of macroinvertebrater per leaf pack thermal regime below the reservoir seems to cornpen- over the entire sampling period. Functional group cla5sitication sate for the virtual absence of shredder species. Inputs based on ,Merritt and Cumrnins (1978): S = shredder, C = of coarse particulate organic matter (CPBhI) are nor- collector, G = grazer, and P = predator. + denotes <0.1. mally reduced below darns (which accounts for re- duced shredder populations) since instream transport Colorado Fraser Functional fro111 upper reaches is eliminated (Ward 1976a). There- Taxon River River group fore, CPBM prob~~blyplays a minor rolc in the encr- getics of regulated stream reaches. Regulated streams Ephemeroptera are characterized by large standing crops of autotrophs Bartis sp. (Ward B 976a) which likely provide the major portion Eplzemerelkc grunciis Ep/~ernerellainfrrqriens of the food base. What then accounts for the rapid Parralt~ptophlebirrsp. processing of leaf litter below Granby Darn'! Enhanced Rlzifhrogentr sp. microbial processing at higher temperatures provides Tricoryfhodes sp. at least a partial explanation. It is also possible that I'lecoptera surficial scraping by the large numbers of E. i~lfrequens All47perIu sp. significantly contributed to weight loss of Colorado Skwrrla purrrllela River leaf packs. Elcvated temperature may increase CLII~USsp. leaf weight loss by increasing fecditag activities of Clausseniu sakulosa rnacroinvertebrates. Preronarcys c~zl$idrnica It is not known whether the findings of the present Ptercmurcellu h~dicc study are applicable to regulated streams in other e'rlpt7ia sp. regions or even to other Botic systems in the Rocky Trichoptera Mountains. Thc proliferation of dams necessitates a Arcropsy:yc./r~sp. fuller understanding of the effects of strearn regulation Hyciropsychr sp. and provides a setting for testing and developing basic Brucllycerlrrus sp. Giossosoma sp. theories of stream ecology. Lc./zidostonra sp. A/zyacop/zila ~tlge'lif~ Acknowledgtnents - The authors wish to thank Dr J. A. Stanford, Worth Texas State University, for reading the Diptera manuscript. Chironomidae Sirnuli~trnsp. At/zerix pacIypus ANDERSCJN,N. H., AND J. R. SEDELL.1979. Detritus processing Coleoptera by rnacroinvertebrates in streams. Pal-snu. Rev. Entomol. 0ptio.servu.s sp. 24: 351-377. BENF~FLD,E. F., P). S. JONES,AND M. F. PATTERSON.1977. Leaf Gastropoda pack processing in a pastureland stream. Oikos 29: P/zJ*s~sp. 99-103. Turbellaria GELROTII,J. V., AND 6.K. MARZQLF.1978. Primary produc- IBolycelis coronoru tion and leaf-litter decomposition in natural and chan- nelized portions of a Kansas stream. Amer. Midl. Nat. Total 99: 238-233. NOTES ]1 27

HART, S. D., AND W. P. HOWMILLER.1975. Studies On the SIIORT,R. A., S. 19. CANTON,AND J. V. WARD.1980. Detrital decomposition of allochthonous detritus in two southern processiilg and associated macroinvertebrates in a California streams. Verh. Tnt. Verein. Lininol. 19: Colorado mountain stream. Ecology. (In press) 1665-1 674. TRISKA,F. J., AND J. R. SEDELL.1976. Decomposition of four MERRIT.~,K. W., AND K. W. CUMMHNS.1978. An introduction species of leaf litter in response to nitrate manipulation. to the aquatic insects of North America. Kendall/Hunt, Ecology 57: 783-792. Dubuque, Iowa. WARD,J. V. 1976a. Comparative litnnology of differentially PETERSEN,W. C., AND K. W. CUMMINS.1974. Leaf processing regulated sections of a Colorado mountain river. Arch. in a woodland stream. Freshwater Biol. 4: 343-368. Hydrobiol. 78 : 310-342. REICE,S. R. 1974. Environmental patchiness and the break- 1976b. Effects of thermal constancy and seasonal down of leaf litter in a woodland stream. Ecology 55: temperature displacement on community structure of 1271-1282. stream macroinvertebrates, p. 302-307.111 G. W. Esch and REICE,S. K. 1977. The role of anirnal associations and current R. W. McFarlane [ed.], Thermal ecology 11, ERDA velocity in sediment specific leaf litter decon~position. Symposium Series (SONF-740425). Oikos 29: 357-365. WARD,J. V., AND W. A. SHOIIT.1978. Macroinvertebrate com- SEDELL,J. K., F. J. TRISKA,AND N. S. TRISKA.1975. The pro- munity structure of four special lotic habitats in Colorado, cessing of conifer and hardwood leaves in two coniferous U.S.A. Verh. Int. Verein. Limnol. 20: 1382-2387. forest streams: 1. Weight loss and associated invertebrates. WARD,J. V., AND J. A. Stanford [ed.] 1970. The ecology of Verh. Int. Verein. Limnol. 19: 1617-1 627. regulated streams. Plenum Publishing Corp., New York, N.Y. (In press)

A Motion for the Retirement of the Von Bertalanffy Function

Dcp.purfm~.t2foj Fisheries and Ocearls, Fislzeries mzd A'MurineService, P.O. Box 5667, Sf. Jolzn's, Nfld. AIC 5x2

ROI:F, D. A. 1980. A motion for the retirernent of the von Bertalanffy function. Can. 9. Fish. Acluat. Sci. 37: 127-129. The reasons for the continued use of the von Bertalanffy equation are examined. It is suggested that these reasons are insutticient to overcome the drawbacks of this function and alternative procedures are recommended.

Key words: von Bertalanffy, growth, yield per recruit

RUFF,D. A. 1980. A motion for the retirement of the von BertalantTy function. Can. J. Fish. Acluat. Sci. 37: 127-129. Nous analysons les raisons pour lesquelles on continue d'utiliser l'kquation de von BertalanfTy. Nous suggkrons que ces raisons sont insuffisantes pour l'emporter sur les dksavan- tages de cette formction, et rmous recornmandons d'autres methodeb. Received June 18, 1979 Re~ule 18 juin 1979 Accepted October 4, 1979 Accept6 le 4 octobre 1979

ONE of the most ubiquitous equations in the fisheries In this note I examine the reasons for this and suggest literat~lreis the von Bcrtalanffy function. Historically it that they do nut outweigh the disadvantages of the von gained wide currency because it claimed to be developed Bertalanffy equation. from bioenergetic principles. However, as pointed out Probably the most general reason for the continued by several authors (Parker and Larkin 1959; Paloheirno use of this equation is that it is a convenient statistical and Dickie 1964; Ursin 1967) this equation, from a description of the data. But is it so convenient'? There bioenergetic perspective, iq at best a special case and at are principally two statistical reasons for selecting a worst noilsense (Knight 1968). Given that the equation particular equation: firstly, the equation may be very can no longer be justified on the grounds upon which flexible and fit a wide range of data and secondly the it was developed. why has it remained so much in use'? equation may be easily fitted to the data. The first is certainly true of the von Bertalanffy function but the Printed in Canada (55680) second is decidely not true, as testified by the recur- Imprim6 au Canada (55688) rence of papers providing methods of fitting it and other