FISHWAY CAPACITY EXPERIMENT, 1956

iMarine Biological Laboratory!

JUL.:-. 1959

WOODS HOLE, MASS.

SPECIAL SCIENTIFIC REPORT- FISHERIES Na 299

UNITED STATES DEPARTMENT OF THE INTERIOR

FISH AND WILDLIFE SERVICE

EXPLANATORY NOTE

The series embodies results of Investigations, usually of restricted

scope, intended to aid or direct management or utilization practices and as

guides for administrative or legislative action. It is Issued in limited quantities

for Official use of Federal, State or cooperating agencies and in processed formfor economy and to avoid delay in publication

.

United States Department of the Interior, Fred A. Seaton, SecretciryFish and Wildlife Service, Arnie J, Suomela, Conanissioner

FISHWAY CAPACITY EXPERIMENT, 1956

by

Carl H. filling and Howard L. RaymondFishery Research Biologists

Bureau of Commercial Fisheries

United States Fish and Wildlife ServiceSpecial Scientific Report—Fisheries No. 299

Washington, D. C.

May 1959

The Library of Congress catalogue card for this publicationis as follows:

EUing, Carl HFishway capacity experiment, 1956, by Carl H. Elling and

Howard L. Eaymond. "Washington, U. S. Dept. of the In-

terior, Fish and Wildlife Service, 1959.

iii, 26 p. illus., diagrs., tables. 27 cm. ( U. S. Fish and WildlifeService. Special scientific report—fisheries, no. 299)

Bibliography : p. 18.

1. Fishways. i. Raymond, Howard L., joint author. (Series)

[SH11.A335 no. 299] Int 59-67

U. S. Dept. of the Interior. Libraryfor Library of Congress

The Fish and Wildlife Service series, Special ScientificReport—Fisheries, is catalogued as follows:

U. S. Fish and Wildlife Service.

Special scientific report : fisheries, no. 1-

iWashington, 1949-

no. Illus., maps, diagrs. 27 cm.

Supersedes in part the Service's Special scientific report

1. Fisheries—Research.

SH11.A335 639.2072 59-60217

Library of Congress (2]

11

TABLE OF CONTENTS

Page

Introduction 1

Materials

Description of Fisheries-Engineering Research Facility . . 2

Assembly and dimensions of experimental fishway 3

Collection, introductory and flow introduction pools ... 4

Fishway hydraulics 6

Lighting 6

Methods

Experimental approach 6

Fish collection 7

Preparations for release of fish 7

Release of fish into fishway 7

Observation and recording procedure 7

Size and species considerations 9

Species identification 10

Test duration 10

Measurement of passage time in fishway 11

Observations

List of capacity tests 11

Effect of changing hydraulics on fish passage 12

Examination of entry rate into fishway 13

Pool residence per minute, September 7 test 15

Fallbacks 16

Discussion 16

Summary 17

Acknowledgments 18

Literature cited 18

Appendix 19

111

FISHWAY CAPACITY EXPERIMENT, 1956 -i'1/

by

Cjtrl H. Elling and Howard L. RaymondU. S. Fish and Wildlife Service

Seattle, Washington

ABSTRACT

Prom May 22 to September 7, 1956, eight tests were made involvingthe passage of varying numbers of fish through an overfall-type fish-way. The fishway, which was 6 feet wide, consisted of 6 pools (1 footrise between pools) each 16 feet long with an average depth of 6.3feet. In the tests, from 70 to 2886 fish entered the fishway during1-hour periods. The median passage time for fish to ascend the 6-poolfishway ranged from 12 to 35 minutes. The effect of pattern of flowand other criteria on fish passage is discussed.

INTRODUCTION

Fishery and water development interestsshare a mutual concern over the high costs

of fishways and fish protection devices at

dams and water diversion projects. As an

example, the fish passage facilities at TheDalles Dam, completed in 1957, cost in

excess of 18 million dollars. Outlays forfish protection structures in some instancesamount to as much as 15 percent of the total

cost of dam construction exclusive of fish-ways (U. S. Fish and Wildlife Service1953).£/ The question arises then, "How maywe seek to reduce these expenditures with-out impairing the safety of fish passage?"A plausible approach lies in the study offish behavior and the principles involvingin fish passage with emphasis on the appli-cation of this knowledge toward the designand construction of more efficient fish-passage facilities.

Modern fishways on the Columbia Riverare undoubtedly the largest £Uid most ela-

borate to be found anywhere in the world.They contain a host of features which their

designers felt were necessary to insuresafe passage of fish beyond the man-madeobstacles. There was good reason for this.

Before the construction of Bonneville Dam,

some people expressed serious doubt that

runs of the magnitude known to migrate upthe Columbia River could be effectivelypassed. As a result, special precautionswere taken to provide ample saifeguards formeeting a number of conceivable conditions(Holmes 1940). Accordingly, the total

facilities finally installed may have beenfar more elaborate than necessary. We findthat dual pasfage facilities (i.e., fishladders and elevators) were provided in the

event one or the other failed to passmigrants effectively. Elaborate collectionsystems and a complex network of auxiliary

W Research financed by the U. S. Army Corpsof Engineers as a part of a broad programof fisheries-engineering research for the

purpose of providing design criteria formore economical and more efficient fish-passage facilities at Corps' projects onthe Columbia River.

2/ A statement by the Fish and Wildlife Ser-vice in response to the request, dated

November 20, 1953, of Senator StylesBridges, Chairman, Senate AppropriationsCommittee, for information on the abun-

dance, distribution, and value of the

Columbia River fish runs, the effect ofdams on these runs, and certain otherrelated information. U. S. Fish and

Wildlife Service, Office of the RegionalDirector (Region 1, Portland, Oregon),41 pp., tables, mimeo.

water conduits were installed to providethe best known attraction and transportationfacilities for fish as they approached and

began their ascent over the dam. Specialfeatures were also added to assist the out-migrating f ingerlings in descending fromforebay to tailrace areas in their journeyto the sea.

Notwithstanding early fears of possiblefailure, the Bonneville fishways immediatelydemonstrated their worthiness. Lessonslearned here played an important part in the

subsequent design of fishways at McNary andThe Dalles Dams which are located upstreamfrom Bonneville Dam. Despite the satisfac-tory operationjil records of the Bonnevilleand McNary fishways, much needs to be doneto achieve increased efficiency.

Heretofore, much of our knowledge offishway design has been derived empirically.Recently, however, various agencies and in-stitutions have initiated vigorous researchprograms designed to provide basic dataapplicable to the solution of the many prob-lems associated with fish passage facilities.One of the more recent developments in thisnew research era is the construction of theFisheries-Engineering Research Facility,located on the Washington side of BonnevilleDam. Here, under controlled Ijiboratory con-ditions, prototype fishways and alliedstructures can be installed and fish behav-ior critically examined by experimentalprocesses.

One of the fundamental questions infishway design which has yet to be speci-fically answered is "How large should afishway be to pass effectively a known orconceivaible maximum number of fish?" If weare presently constructing our fishways farlarger than the maximum demand requires,then it is obvious a considerable savingmight be realized merely through a reductionin their size. Not only may constructioncosts be reduced, but concomitant watereconomies may also be expected.

Initial research, seeking a basis forthe solution of the problem of fishway size,began at the Bonneville facility in thespring of 1956 and was continued intermit-tently until early September of that yeair.

The term "fishway capacity" was used todescribe the object of these experimentsand may be defined as the "maximum numberof fish (size and species considered) that

a fishway of given dimensions and hydraulicconditions can pass per unit time."

The purpose of this study is (1) todetermine experimentEilly the specific capa-city of a prototype overfall fishway and(2) to note factors which may influencethis capacity.

The following is a report of the ini-tial phase of our work which was confinedprimarily to the development of proceduresand techniques whereby capsicity might bemeasured. No attempt is made to consolidatethese initial endeavors into a final deter-mination of capacity. Several observationsare made and the significance of each is

discussed as it affects a measure of fish-way capacity. These have been included sothat they may become readily available forexamination and study by those immediatelyconcerned with the problem.

As this work is essentially preliminary,we emphasize that interpretation of therecent observations can be only tentative,pending further examination of the specificrelationships which may control fishwayc apacity.

MATERIALS

Description of Fisheries-EngineeringResearch Facility

A detailed description of the Fisheries-Engineering Research Facility is in prepara-tion by Collins .2' Essentially the structureis a rectangualr flume 200 feet long by 24feet wide with a maximum depth of 24 feet.

The flume is a unit of a by-pass structureconnecting with the Washington shore fishway.Various prefabricated structures may be in-

stalled in the flume to simulate a varietyof experimental fishway conditions. Anoverhead traveling crane is used to installand remove the heavier structures used inthe studies.

Fish for experimental purposes, di-verted from the Washington shore fishway,ascend an entrance fishway to a collection

3/ Collins, Gerald B. Research in fishpassage problems, U. S. Fish and Wild-life Service. Manuscript in preparation.

pool inside the facility. From this pointthey are released into the experimental area

where their movements are observed and re-

corded. They then pass into a large upper

pool (flow introduction pool) and leave this

area by means of an exit fishway which again

joins the main ladder. A unique feature ofthe present experiments is that the fish are

never bandied or removed from their fishwayenvironment.

Assembly and Dimensions ofExperimental Fishway

The established width of experimentalfishways in the Bonneville facility is

11 1/2 feet. To reduce the number of fishnecessary to demonstrate c«ipacity, the orig-

inal fishway width was cut to 6 feet by

installing a partition approximately in the

middle of the fishway (figure 1). Thiscreated an experiaiental area comprised ofsix pools, each 16 feet long (weir center

to weir center), 6 feet wide, and with an

average depth of 6.3 feet. There was a onefoot rise between pools (1:16 slope). Totallength of the fishway was 96 feet. Weirswere 6 feet high and 7 1/2 inches thick.

Weir crests were square and painted whiteto aid in the observation of fish duringturbid water periods. All other structureswere painted camouflage brown. There wereno orifices in the weirs although smalldrains (closed during tests) were provided.A cross section view of a weir is shown in

figure 2. Diagrammatic pi tin and side viewsof the experimental fishway are given in

WOOD

WOOD

CONCRETE

I

^6.0'

64i"

37"

i i i i

FIGURE 1 .-- INSTALLING PARTITION WALL TO CREATEA 6-FOOT WIDE FISHWAY FOR THE CAPACITy TESTS,

FIGURE 2. --CROSS SECTION OF WEIR USED IN TESTFISHWAY.

EntryTunnel^

Entrance Fishway ^Norfh Fishway

Exit Fishway

cCOLLECTION

POOL

MeshBorrier /

Center Wall

JCrowder Well

Te S I F i s h w y ^

FLOWINTRODUCTION

POOL

i«- Finger Trap

Brail Release Cote,

54' 55

Introductory Pool

56' 57

PLAN VIEW

58 59 60'

40.0

Collection Pool Broi

SIDE VIEW

- €0.8

Flow Introduction —-^

Pool Brail

FIGURE 3. --DIAGRAMMATIC PLAN AND SIDE VIEWS OF THE TEST FISHWAY AND ASSOCIATEDPOOLS IN THE EXPERIMENTAL FACILITY.

figure 3. Elevations noted are relative to

comparable points at Bonneville Dam. Allelevations are expressed in height (feet)

above mean sea level.

Collection, Introductory and

Flow Introduction Pools

In addition to the test fishway proper,the flume was partitioned into severalaccessory pools to accommodate the fishbefore and after their passage through thetest area. These were the collection pool,the introductory pool, and the flow intro-duction pool (figure 3).

Fish ascending the entrance fishwayentered the flume by means of a portableentry "tunnel", passing through this struc-ture into the collection pool. This tunnel(figure 4) was simply an extension of theentrance fishway. Its V-shaped exit wasequipped with a finger trap which preventedfish from backing down into the entrancefishway after having entered the collectionpool.

The collection pool provided an areain which to contain the fish prior to theirrelease into the fishway. Pool dimensionswere 30 feet by 24 feet with a water depth

of 14 feet. A brail, which could be raisedas desired, covered the pool bottom. Apicketed barrier marked the upstream limit

of the collection pool. This structureextended 8 feet above the water surface to

prevent fish from jumping from the collec-tion pool into the fishway introductorypool. A 5-foot release gate in the barrierprovided access to the experimental area.

Water depth at the gate entrjince was 2 feet.

After fish paissed through the releasegate they entered cin introductory poolbefore beginning their ascent in the test

fishway. This pool was 7 feet deep, 13 feetlong, and varied in width from 11 feet at

the downstream end to 6 feet at its juncturewith the partition wall at the first weirin the fishway.

When the fish had completed their pas-

sage through the experimental fishway, they

entered the flow introduction pool whichwas 37 feet long and 24 feet wide. A fingertrap on the upstream face of the final weir(elevation 60) permitted exit but preventedfish from drifting or swimming back into the

test area once their movements had been re-

corded (figure 5). Water 3 to 4 inches in

depth flowed over the upper surface of the

finger trap.

FIGURE 4 --VIEW OF ENTRY TUNNEL THROUGH WHICH FISH PASS FROM*

THE ENTRANCE FISHWAY TO ENTER THE COLLECTION POOL.

FINGER TRAP AT EXIT PREVENTS FISH FROM LEAVING THE

COLLECT ION AREA

.

FIGURE 5. --VIEW OF FINAL WEIR IN TEST FISHWAY SHOWING FINGERTRAP ON UPSTREAM FACE OF WEIR. NOTE STREAMINGFLOW IN VICINITY OF SALMON.

A fixed brail was installed in the flowintroduction pool to limit fish movement to

the upper 5 feet of this pool which has a

depth of 14 feet. Reduction of the pooldepth served to discourage the fish fromlingering unnecessarily in this area beforepassing outward into the exit section and

back into the Washington shore fishway.

Fishway Hydraulics

Total water fall in the 96-foot fishwaywas 6 feet (elevation 60 feet to elevation54 feet). Standard water flows were con-trolled to allow for 0.8-foot head (measured4 feet upstream of weir) on the weir crestwhich was the approximate upper limit at

which plunging flow could be maintained onthe Square-crested weir. When the fishwaywas filled with water, the approximate watervolume per pool (accounting for the areadisplaced by weirs) was 585 cubic feet.Calculated discharge of the test fishway was15.9 c.f.s.

Two sources provided water for theexperiments: (1) a water supply systemoriginating in the Bonneville Dam forebay,and (2) the exit fishway which received its

water from the Washington shore fishway.Water balance within the facility was main-tained by manual control of water intakeand discharge valves.

Lighting

A constant light condition was estab-lished for all experiments. Sixteen 1000-watt fluorescent mercury vapor lamps werehung directly over the area in the testfishway. As a standard, all light assem-blies were set arbitrarily at 6 feet abovethe water surface. This provided an averagelight intensity comparable to that whichmight be found in an outside fishway on a

bright, cloudy day. Readings obtaineddirectly under lights at the water surfaceaveraged 850 foot candles. The range ofincident light was 350 to 1000 foot candles.

METHODS

Experimental Approach

Our approach to the solution of thequestion, "What is the capacity of a fish-way?" has been based on the belief thatthe condition can be physically demonstrated

by the introduction of varying quantitiesof fish into a given fishway. Thus, bygradually increasing the numbers of fishintroduced in each experiment, eventuallyan end point or boundary indicating maximumpassage per unit time would be reached.Since there is no way to anticipate the par-ticular point at which this will occur, it

will be necessary, therefore, to extend thefishway beyond a hypothetical capacity in

order to examine the particulair reactionswhich might develop as a result of an over-crowded condition, if such develops. Todemonstrate this condition, the first andmost importEint requirement will be to main-tain a constant supply of fish in excess ofthe maximum the fishway would be capable ofpassing per unit time— at least for a periodlong enough to establish that certain funda-mental relationships are characteristic ofa saturated or possible overcrowded fishway.

The foregoing approach will lead to the

examination of the following concepts as

they are applicable to the determination ofcapacity in an overfall, pool-type fishway:

1. The initial factor limiting the

capacity of any fishway is the maximum num-

ber of fish that may enter per unit time.Among the factors which may affect maximumentry are (a) passage space, (b) entrancehydraulics, and (c) differential motivationamong the fish on different days and withinthe same day.

2. Maximum exit per unit time (capa-

ity) can equal maximum entry per unit time.

3. Once a maximum entry is reached and

maintained, the rate at which fish ascendthe fishway will govern the extent to whichthey will accumulate in the fishway per unittime. This accumulation will mount arithme-tically as the rate of movement decreases.For instance, if entry is established at a

maximum of 40 fish per minute and fish ascend

the fishway at an average rate of one poolper minute, then 40 fish will be the averagenumber present in each pool. If the averagerate of movement decreases to an ascent of

one pool every two minutes or one pool everythree minutes, then the accumulation in eachat a given minute will be 80 and 120 fishrespectively. Exit in each instance will

be 40 fish per minute. As long as the accu-

mulation resulting from a particular rate

of movement in combination with a fixed

maximum entry rate does not impair "free"

movement in the fishway, exit per unit time

should equal entry per unit time.

4. There may be a point at which the

meiximum entry per unit time in combination

with a particularly slow rate of movement

will produce an excessive accumulation of

fish in the fishway. Once this condition

is reached, the following may result: (a)

maximum exit per unit time will decline

below maximum entry per unit time, (b) entry

per unit time may also decline (i.e., a

given number may enter a pool each minute,

but of these a certain number may drop back

out of the pool, presumably because of lack

of sufficient space in the pool), or (c) a

further decrease in rate of movement. The

latter may be difficult to define, but an

excessively slow movement coupled with high

density could be indicative of a crowdedcondition impairing movement.

Fish Collection

To accumulate a supply of fish for the

capacity test, fish ascending the entrance

fishway were contained in the collectionpool until such time as it was felt that

sufficient numbers were on hand to conduct

the experiment. At the outset of these

experiments, our estimates of the number offish that would be required to fill the

fishway to capacity were necesszirily arbi-

trary. The only way to determine the number

was to conduct several experiments, eachtime increasing the numbers collected (withdue consideration for size and species offish passed), if previous experimentationindicated that capacity had not been reached.

As the experiments progressed, it becameevident that sever jd thousand or more fishwould be necessary to create or exceed a

capacity situation in the test fishway. Acollection of this magnitude occasionallyrequired that some fish be held in excessof 48 hours prior to release.

Sample counts were made on the hourbetween 8:00 A.M. to 4:00 P.M. to obtainrelative estimates of the number of fish in

the collection pool. These were taken byobserving the fish as they passed from theentry tunnel into the collection pool.

Preparations for Release of Fish

Just before the beginning of a test,the entry tunnel was removed and a screenwas inserted in its place to prevent fish

from backing out of the pool. Then the

collection pool brail was raised approxi-mately 11 feet. This confined all fishwithin a 3-foot surface layer of the pool.

The view in figure 6 (page 8) shows the

concentrattion of fish in the collectionpool following this operation. The purposeof the above maneuver was to create a con-centration of fish similar to that whichmight exist in an actual fishway duringjjeriods of peak migration.

Release of Fish into Fishway

Shortly after the collection pool brail

was raised, the release gate in the picketedbarrier was opened to provide access to the

test fishway. This was considered the start

of the test. As the fish moved through the

entry gate into the introductory pool and

then up into the fishway, the downstream end

of the brail was gradually raised higher to

concentrate further the remaining fish in

the vicinity of the fishway entrance. Fig-

ure 7 (page 8) presents a view of the col-lection pool showing the entry gate in openposition and with the brail tilted.

Observation and Recording Procedure

Immediately prior to the release offish from the collection pool, observerswere stationed along the walkways at pointsoverlooking the various weirs. Each observ-er was provided with a push button limit

switch which recorded the passage of fishon an operations recorder (figure 8, page 9).

This provided a convenient means of record-ing the number of fish and the time at which

each passed a particular weir while the

experiment was in progress.

One of our major problems in the fish-way capacity experiments was to obtain an

accurate tally of fish passage at eachobservation station. Counting errors wereparticularly evident in some of the initial

tests before our observers had acquiredproficiency in counting procedure. As the

season progressed and the observers gainedexperience, discrepancies in counts at

individual stations became less evident.

The most difficult counting periodgenerally occurred immediately follcwingthe release of fish from the collection pool

and for a period of 10 to 15 minutes there-after. During this time, observers occa-sionailly had to tally over 100 fish per

FIGURE 6. --VIEW OF COLLECTION POOL PRIOR TO RELEASE OF FISHINTO TEST FISHWAY. BRAIL HAS BEEN RAISED TO CON-FINE FISH TO SURFACE OF POOL AND INDUCE MOVEMENTINTO FISHWAY.

FIGURE 7. --LOOKING UPSTREAM OVER COLLECTION POOL WITH ENTRYGATE IN OPEN POSITION. POOL BRAIL HAS BEENRAISED AND Tl LTED.

minute. To simplify counting, the observers

were instructed to tally in groups of five

until the numbers passing decreased suffi-

ciently to permit individual tally of fish.

Size and Species Considerations

In a study of fishway capacity we must

necesscLrily give consideration to the size

and species composition of a fish population

which may be expected to pass a fishway

located in a given area of a river system.

For instance, if a fishway is limited

size, we may logically expect to pass great-

er numbers (per unit time) of a run in which

species average 5 pounds in weight than of

another run in which species average 10

pounds, other factors being equal. Further,

if the smaller of the two species is capable

of ascending the fishway twice as fast as the

larger, then the potential difference in

total numbers capable of passage per unit

time may become even greater when we compare

the capacity of the fishway with respect to

the two species. Conversely, the oppositemight be true if the larger of the two spe-

cies proves to be the better swimmer. Clearlywe must recognize . the possible effect ofthese two factors—size and species perform-

tince— in our measure of fishway capacity.

The three most common salmon passingBonneville Dam in order of abundance are (1)

Chinook (Oncorhynchus tschawytscha Walbaum),

(2) blueback (0. nerka Walbaum), and (3)

silver (0. kisutch Walbaum). Two other spe-

cies, chum salmon (0. keta Walbaum) and pink

salmon (0. gorbuscha Walbaum) are alsoknown to pass the dam, the latter rarely.

Except for chinook salmon, the steel-

head (Salrao gairdneri Richardson) is usually

the most abundant salmonoid appearing at

Bonneville Dam.

For comparative purposes, the averageweights of the various species will be usedas a measure of size. Weights of the above-mentioned species, particularly chinooksalmon (Silliman e_t al. 1947) may vary con-siderably between and within years. The fol-

lowing average weights (Cleaver 1951) are

presented to demonstrate characteristic sizedifferences among salmonoids present in the

Columbia River: chinook salmon, 17 — to

FIGURE 8.--0PERATiONS RECORDER USED TO RECORD

FISH PASSAGE IN NUMBERS PER UNIT TIME.

EACH PASSAGE IS NOTED IN THE FORM OF A

BLIP ON THE RECORDER TAPE AT THE EXACT

MOMENT OF OCCURRENCE.

20- pounds; steelhead, 9 pounds; blueback,

3 pounds; and silver salmon, 10 pounds.

Average weights obtained during Septem-ber 1949 (Schoning et al. 1951) at CeliloFalls (now inundated), which was approxi-mately 50 miles above Bonneville Dam on the

Columbia River, showed that chinook salmonaverage 15.7 pounds; steelhead, 9.25 pounds;

and silver, 7.1 pounds.

Average weights listed above apply to

fish taken in commercial catches and maynot, therefore, be directly applicable to

the salmonoid population passing Bonneville

_4/ "Spring" run average. ArbitrarilyJanuary 1 - July 31.

5/ "Fall" run average. ArbitrarilyAugust 1 - December 31.

Dam. In the recent capacity experiments it

was not possible to obtain a series of aver-

age weights of species passed. To have doneso would have entailed considerable handlingof the fish, a situation we particularlysought to avoid.

Therefore, in the absence of actualfield measurements applicable to these tests,

estimated weights were assigned to each spe-cies with respect to season, based in parton the information contained in the fore-going reports. For the tests conducted on

July 13 and September 7, the average weightper fish (all species) was estimated at 3

and 13 pounds respectively.

In addition to salmonoids considerablenumbers of miscellaneous species pass Bonne-ville Dam each year. The term "scrap" fishhas come to be applied locally to the non-salmonoid fishes which have limited or nocommercial value. They are generally inpeak abundance during early summer, as a

rule, shortly after the high water run off.Among those most frequently observed in thefishways at Bonneville Dam are the ColumbiaRiver sucker ( Catostomus microcheilus )

,

common carp ( Cyprinus carpio ) , squawfish(Ptyocheilus oregonenis ) and chiselmouthchub (Achrocheilus alutaceus ). Also present,in addition to the so-called scrap fish, are

the shad (Alosa sapidissima ) , Oregon white-fish (Prosopium oregonium ) , white sturgeon(Ancipenser transmontanus ) , asid a fish-likevertebrate, the lamprey (Entosphenus triden-

tatus )

.

Scrap fish were estimated to range inweight from several ounces (small suckersand squawfish) to over 10 pounds (carp).The majority, however, probably averagedless than 1 pound. As a group they mayoccasionally be as abundant or more so thanthe salmonoids. In this regard their pre-sence must not be overlooked since they arein competition with the salmonoids for spacein the fishway.

Species Identification

As a wide variety of fish could havebeen present for a given test, it was impor-tant to develop a simple and yet effectivemethod by which to identify the variousspecies. Since all fish generally werevisible only momentarily as they passed aweir crest, identification was necessarilyconfined to a rapid sight recognition of a

salient feature. Use of the conventionalfish identification key was, therefore, oflittle value under these circumstances,while body conformation and color were occa-sionally useful, we eventually found thatdorsal markings provided the most reliablemeans for rapid field identification of theSalmonoids. For instance, markings on theChinook salmon were generally large (5 to10 mm.), oblong, blotch-like and numerous.Steelhead dorsal marks were much smaller(2 to 3 mm.), ovoid or nearly so, and numer-ous to very few. On the blueback salmon,dorsal markings were generally absent orextremely rare. The silver salmon moreclosely resembles the steelhead than any ofthe other species. Its markings, however,were more rectangular than ovoid, about 3

to 4 mm. long and generally quite numerous.The above descriptions apply to the ColumbiaRiver salmonoids as we observed them at

Bonneville Dam and are not necessary appli-cable to other watersheds frequented by thePacific salmon and steelhead. Fish otherthan salmonoids were summarily listed as

scrap fish.

During several initial capacity trials,attempts were made to identify the speciescomposition at each weir. This was soonfound to be impracticable as water turbu-lence in the downstream sections of the

fishway either prevented or limited the pos-sibility of accurate identification. Thecrest of the last weir in the fishway waseventually chosen as the site at which to

identify the various species. Here rela-tively smooth water flows allowed a moreaccurate identification. Two observers were

always stationed at the final weir, one to

record total count and the other to tallyspecies. Total count by minutes was trans-mitted to the operations recorder whilespecies counts were kept manually on a

multiple hand-tally array.

Test Duration

Following the release of fish from the

collection pool, observations at the fishwayweirs were generally continued for a periodof 60 minutes. The length of the testingperiod was again arbitrary and as the exper-iments progressed, we occasionally deviatedfrom the assigned one hour test period.

However, in general, the 60-minute observa-tion period was established as a standardfor comparative purposes.

10

Ideally, assuming that a constant,

abundant supply of fish would be available

for each experiment, tests might be run for

continuous periods of perhaps 10 to 14 hours

and thus provide us with a basis upon whichto measure possible diurnal fluctuations in

fishway capacity. As conditions developedexperimentally, our supply generally becameexhausted—or nearly so—within periods ofless than 60 minutes.

Measurement of Passage Timein Fishway

Several means of measuring rate ofascent in a fishway are possible. Tautiand Miyoshi (1934) expressed rate of ascentin terms of "the number of fishes whichreach the top of the fishway in unit time

expressed as a percent cLge of the total num-ber of fishes." While this method allowsfor a convenient comparison between trials,

a measure expressing passage in terms ofan average time required to ascend the fish-way (or in time per pool) is perhaps moreappropriate for the intent of these experi-ments. This may be conveniently expressedas minutes per pool or in minutes requiredto ascend the 6-pool test fishway.

The measure established for the pur-pose of comparing passage time in the recentcapacity experiments was median elapsedtime. This was derived by subtracting thetime at which half of the total release hadpassed the lower weir (elevation 54) fromthe time at which half of the total enteredhas passed the upper weir (elevation 60).For example, in a given test the releaseover weir 54 in a 1-hour period is 1525fish; the median time (763rd fish) at weir54 is observed at minute 15; median time(763rd fish) at weir 60 occurs at minute 35;

median elapsed time is 20 minutes (35- 15 =

20) for the 6-pool fishway. This mightalso be expressed as a rate of one pool per3.3 minutes.

Use of the median was psurticularlyadvantageous as applied to these experi-ments. For instance, it was not necessaryto continue jui experiment until all fishentering had completed passage through thefishway. Only an excess of 50 percent pas-sage was necessary. Had the mean time beenused as a measure of rate of ascent, allfish entering would have to be accounted for

in the exit. Also, preliminary examinationof passage time frequency curves (unpub-

lished data based on the passage time ofindividual fish) suggests a marked skewnessto the right with the majority of indivi-duals (central values) falling in the lefthand portion of the curve. Use of themedicin will, therefore, more adequatelyrepresent the central tendency of a ssimple

since it is not distorted by unusual valuesto the right of the point of maximum fre-quency on the curve.

We recognize that while the median is

useful from a comparative standpoint, it

is open to the criticism that in praticeone is concerned with all the fish leavinga fishway, not only the first 50 percent.In these experiments from 61 to 92 percentof those entering actually left the testfishway within the test interval.

OBSERVATIONS

List of Capacity Tests

As has been noted, our measure of capa-city was to be based on a series of testsbeginning with trials involving relativelysmall numbers of fish and continuing withgradually increasing numbers introduced in

each trial until capacity was reached and

could be effectively demonstrated. Much ofour initial effort (trials 1 through 6) wasconfined to the development and refinementof experimental procedure and techniques.Data obtained during these early tests were,

therefore, subject to a variety of condi-tions which were not always comparable.However, the data are included for examina-tion, since they provide a fund of back-ground information which may be basic tothe examination of fishway capacity.

In all, eight capacity tests were con-ducted during the period May 22 throughSeptember 7, 1956. A summary of these tests

is given in table 1 (page 12). Total num-bers released in an individual test rangedfrom 70 to nearly 3000 fish during a 1-hourperiod. The test involving the largestnumber of fish (July 13) was not, however,the leirgest when considered in terms oftotal weight. A conversion to estimatedpoundage shows the weight of the fish inthe September 7 test was more than doublethat in the July 13 test (13 pounds x 1515=19,695 pounds as compared to 3 pounds x2886 = 8,658 pounds).

11

Table 1.—Surnnar;' of fishway capacity tests, 1956

40

20

Slreoming Flow^Developed

rin ^n |"EDIAN( 22'26)

I40r

120-

100

g 80

60

40

20-

MEOIAN (5U8)

u^raj\ i-JLrw^ n n-TS.ri,,20 30 40

Minutes offer Release50 60

FIGURE 9. --COMPARISON OF FISH PASSAGE AT UPPER ANDLOWER WEIRS OF FISHWAY IN THE JULY 5, 1956 CAPA-CITY TEST. STREAMING FLOW DEVELOPED AT UPPERWEIR (60) AT END OF MINUTE 3. PLUNGING FLOW IN

EFFECT DURING ENTIRE 60-MINUTE PERIOD AT LOWERWEIR (54)

.

60-minute test period. By contrast, the

passage curve at weir 60 is clearly bimodal.The abrupt decline in numbers passing perunit time directly coincides with the incep-tion of streeiming flow at this weir.

In measuring the possible effect ofstrccuning flow on rate of movement, we mayexajnine the position of the median psissage

time at the two weirs (54 and 60). At the

lower weir (54) half of the group hadentered the fishway in approximately 5.3minutes (figure 9) while half had ascendedthe fishway at 22.4 minutes aifter the startof the test. Thus, the median elapsed time

in the fishway was 17.1 minutes (22.4- 5.3).

Conceivcibly, had streaming flow failed to

develop at weir 60, the medicin time at thisweir might have been reached several min-utes earlier with a resultant decrease in

the median elapsed time. This is based onthe assumption that all passage to the right

of minute 9 would be proportionately reposi-tioned to the left, filling in the depres-sion in the passage curve caused by stream-ing flow.

Comparison of the capacity trials heldon July 2 and 5 (table 1) gives interestingsupport to the above. These trials werevirtually identical as regards species com-position. A principal difference in the

tests is that streaming flows did not devel-op in the July 2 trial. Significantly, the

median elapsed time for the July 5 trial

(streaming flows in effect) was approximately

4.5 minutes in excess of that observed inthe July 2 test (17.1-12.6).

Examination of Entry Rateinto Fishway

One of the means by which we expectedto recognize whether capacity were reachedor exceeded was to examine the entry rate —

'

into the fishway. Conceivably a peak entryrate (the maximum number of a given sizewhich could enter a fishway 6 feet wide inunit time) would be reached, and providedthat the supply could be maintained at thispoint, we would expect the net entry to

stablize at a given level (assuming fishsize remained constant). During the firstseven experiments (May 22 to July 13

6/

The striking feature in the passage offish at weir 60 is that movement was virtu-ally halted for approximately 5 minutes(minute 4 through 8) during the initialperiod that streaiming flow was in effect.(See table 2 in the Appendix.) Thereafter,the migrcints apparently gradually becameconditioned to the change in flow and con-tinued their ascent out of the fishway.

_6/ As applied here, the entry rate is netentry per minute; i.e., the total numberof fish entering a pool in a given min-ute minus the number of fish droppingdownstream out of the pool in the sameminute. A subsequent section will bedevoted to "fallbacks" which we havetermed those fish which move downstreamfrom one pool to another.

13

inclusive) this condition was never clearly

demonstrated.

Chief among the difficulties in pro-

ducing and maintaining a maximum entry was

our inability to provide an ample, sustained

supply of fish for the tests. A typical

entry rate achieved in the initial tests is

shown in figure 10. Depicted is the passage

of fish over the various weirs in the July13 experiment. The entry into the fishway

is shown in the passage over weir 54. This

may be seen to rise rapidly to a peak (350

fish per minute) shortly after the release

and then decline almost as rapidly as it

had risen. At this stage of the investiga-

tions the assumption is that the supply was

not adequate to sustain a constant maximum

entry. Also, a major portion of the initial

supply would always be required to saturate

the fishway which was void of fish at the

start of a test. By the time a point of

saturation was being approached, the supply

had become virtually exhausted. Thus, it

was becoming apparent that the presentexperimental condition of limited supplywas to be an obvious deterrent to a realis-

tic determination of capacity.

Realization of the existing experimen-tal limitations led us to conclude that ourinitial approach to a determination of capa-city would undoubtedly have to come from an

examination of conditions in the lower pools

of the fishway. This reasoning was beised

on the belief that the greatest surge offish would undoubtedly occur at the point

of entry into the fishway and that the lowerpools would be the first and perhaps the

only areas in the fishway which would becomesufficiently saturated for any period oftime. The approach may not appear to be in

keeping with our stated purpose of determin-ing the maximum number of fish that a fish-way can pass since passage implies that the

measure should be based on the exit fromthe fishway (last pool). It is probable,however, that capacity may in fact be con-trolled at a particular point in the fish-way, and that this point might well be in

the first pool or one of the lower pools.Later in the text, data will be presentedwhich lend some support to this assumption.

In the final test of the season (Sep-

tember 7) there is indication that a sus-tained entry rate finally may have beenachieved. Figure 11 presents the numbersof fish passing per unit time at 5 of 7

lOOrWEIR 60

WEIR 58

WEIR 56

WEIR 54

Minutes After Release

FIGURE 10. --PASSAGE PER MINUTE OVER WEIRS54, 55, 56, 58 AND 60 DURING CAPACITYTEST OF JULY 13, 1956.

weirs in the fishway. Entry rate into the

fishway is given in the passage curve shown

at weir 54. The maximum observed entry per

minute was 75 fish and this occurred in both

the 2nd and 5th minute after release. From

the 6th to the 22nd minute, the entry held

relatively constant, fluctuating between 40

14

AAA^^^^A^

40 60 ^' 80Minutes After Release

FIGURE 11.- PASSAGE PER MINUTE OVER WEIRS 54 55,56, 57 AND 60 DURING CAPACITY TEST OFSEPTEMBER 7, 1956.

and 60 fish per minute. The average for the

17-ininute period was 51 fish per minute.(Table 3, Appendix.)

The fact that the entry rate in theSeptember 7 trial did not appreciably de-cline after rising to a peak as was typicalin all previous tests, but instead rose toand then sustained a maximum level for a

number of minute, leads us to believe thatwe may have achieved a condition (maximumentry) which might demonstrate the existenceof capacity. Since this was the only testin which a sustained entry wzts demonstrated,a conclusion regarding the foregoing mustawait the conduct of further tests in whichconditions of maximum entry can again berepeated for a sustained period.

Pool Residence Per Minute,

September 7 Test

Given in figure 12 are curves showingthe number of fish present in each of the

10 20 30 40 50 60 70 80 90 100 110 120

Minutes After Release

FIGURE 12. --NUMBERS OF FISH PRESENT IN POOLS 55,56 AND 57 DURING A GIVEN MINUTE IN THESEPTEMBER 7, 1956 CAPACITY TEST.

three lower pools (55, 56, and 57) in a

given minute during the September 7 capacitytest. During the test, it became evidentthat fish were not moving through the fish-way as rapidly as they had in previous tests.For this reason, the usual 60-minute trialperiod was extended for an additional hourto allow for a continued observation ofmovement in the fishway. The maximum numberof fish observed in a single pool in a givenminute was 239. This occurred in both pools55 and 56, reaching a maximum in minute 35in the former, and minute 21 in the latter.The maximum number of fish in the fishway(6 pools) was 948, reached 28 minutes afterrelease. (For complete data on the fore-going, refer to table 4 in the Appendix.)

A striking feature in the comparisonof pool residence in the three lower poolsis the continued long residence in pool 55,the first pool in the fishway. After reach-ing a peak of 239 fish in the 35th minute,numbers present in this pool did not fallbelow 200 fish until the 80th minute. Bycontrast, residence in pools 56 and 57,after reaching a peak density, declined farmore rapidly than in pool 55. At the con-clusion of the 2-hour test a total of 82

fish remained in pools 56 and 57. Almostdouble this number was present in pool 55

at the end of the test.

15

From the foregoing it may be concludedthat there must have been an accumulation of

slow fish in the lower pool of the fishway.

If there is a tendency for slow-moving fishto accumulate in the lower pool(s) of the

fishway (further experimentation will be

necessary to verify this) then the restric-tion on capacity will be determined by the

residence in a single pool and not on an

average residence for all pools.

Whether the phenomenon was a naturaloccurrence or the result of experimentalprocedure remains to be determined. Shouldthe relationship persist in subsequentexperiments in which varying release tech-

niques are employed, it may be possible to

demonstrate that a natural accumulation ofslow fish develops in the lower section ofa fishway under crowded conditions, and

that resultant spatial restrictions willundoubtedly influence passage (capacity)through the fishway. If this be true, the

suggestion has been made that some of the

lower fishway pools could be constructedconsiderably larger than succeeding upstreampools to provide additional space for the

slow fish and at the same time allow suffi-cient passage area for the other migrantswhich proceed up the fishway more rapidly.

Fallbacks

In some of the initial capacity testsinvolving the release of relatively smallnumbers of fish, a few fish in each trialwere observed to enter a pool and then driftback downstream into the pool below. Fishexhibiting this particular behavior werecalled "fallbacks". As the number of fishintroduced in each test was increased, thenumber of fallbacks also increased. Thefrequency leads us to speculate that thephenomenon might be a possible indicator ofa capacity condition.

first observed at the lowermost weir andwere subsequently noted at successive up-stream weirs with respect to time (table 3,

Appendix). Initial fallback activity ineach pool aippeared to commence at about thetime considerjjjle numbers of fish had col-lected in that pool (tables 3 and 4, Appen-dix).

However, aside from the actual numberof fish involved in a given test, otherfactors may have influenced the frequencyof fallback activity. For instance, weobserved that streaming flows could verywell have been responsible for a consider-able number of feillbacks since the fishwould orient to the surface area of thepool rather than in the subsurface levelsas was generally the case when plungingflows prevailed. This surface alignment offish during streaming flows increases thepossibility of drifting back downstreamover the weir crest and into the pool below.

We also observed that steelheadappeared to be more inclined to fallbackactivity than the other salmonoids. Conse-quently, the species composition in a giventest might well affect the number of fall-backs.

Fallbacks were also observed in otherexperiments at the Bonneville facility in

which individual fish or small groups (30 or

less) of fish were being timed up the fish-

way. Here the implication was that fallbackactivity was not the result of crowding but

due to some other factor. Continued studyon the nature of fallback activity will be

necessary to establish the import of thisphenomenon as it may be related to fishwaycapacity.

DISCUSSION

In the September 7 trial, fallbackswere recorded at each of the four lowerweirs with respect to time. The followingtotals were observed during the 2-hour testperiod: at weir 54-566 fish, weir 55-392,weir 56-82, and weir 57-35. Total numbersof fallbacks observed do not necessarilyimply the actual number of individual fishinvolved since a single fish may have beenresponsible for several fallback observa-tions. Apparent in these observations isthe progresfive decline in fallbacks as thefishway is ascended. Also, fallbacks were

Certain limitations must be consideredwhen using results obtained under the pre-

sent experimental technique. The verynature of the experiments requires that

large numbers of fish be readily availablefor use in the tests. Since it was not

possible to supply sufficient numbers in-

stantaneously, the method required that

fish be collected and held until a presumedample supply was on hand for an experiment.It is not known what effect the collectionperiod may have had on the eventual motiva-tion of the fish once they were released.

16

Due consideration must also be givento the fact that our experimental subjectswere diverted from a large 1:16 slope fish-way approximately 35 feet wide into a narrowby-pass fishway 6 feet wide having a 1:8

slope. From this point they entered a largecollection pool and were then released to

enter a 1:16 slope test fishway of a 6-footwidth. We assumed that performance in the

test fishway was independent of the changingentry conditions.

Plans for succeeding experiments call

for reduction in fishway width and a changein weir crest design. By decreasing the

present fishway width to 4 feet we expect to

reduce the total fish requirement necessaryto measure capacity. The change in weircrest is intended to eliminate the unstablehydraulic condition which developed in therecent tests due to use of a 7 1/2-inchsquare-crested weir.

SUNWARY

Initial experiments were undertaken to

measure the capacity (maximum number of fishpassed per unit time) in an overfall-typefishway which was 6 feet wide and consistedof 6 pools, each 16 feet long (weir centerto weir center) with an average depth of 6.3

feet. There was a 1-foot rise between poolsand approximately 0.8-foot head on the weirswhich were square crested cUid 7 1/2 inchesthick. The calculated dischcirge was 15.9c.f.s.

The following is a summary of opera-tions and observations made in the 1956capacity tests:

1. Eight tests in which releasesvaried in magnitude from 70 to2886 fish in a 1-hour period wereconducted from May 22 throughSeptember 7, 1956.

2. In numbers, the Icirgest releaseduring a 1-hour period totalled2886 fish. Estimated averageweight of fish in this test was3 pounds. The total estimatedweight of all fish in the test was8658 pounds.

3. In a test adjudged to be the larg-est release in terms of grossweight, 1515 fish, averaging an

estimated 13 pounds per fish,entered the test fishway in a 1-

hour period. The total estimatedweight of fish in this release was19,700 pounds.

4. A maximum entry rate of 350 fishper minute was observed in the

test in which fish averaged appro-ximately 3 pounds in weight. Thishigh entry level could not be sus-tained, possibly because of rapiddepletion of the original supplyof fish.

5. Maximum entry in the test in whichfish averaged 13 pounds, was 75

fish per minute. For a period of17 minutes (minute 6 through 22)the entry ranged from 40 to 60fish per minute, averaging 51 fishper minute. This was the onlytried among the eight conducted in

which a sustained entry was observ-ed, suggesting that a limitinglevel may have been reached.

6. Among the eight trials, the medianelapsed passcige time required to

ascend the 6-pool test fishwayranged from 12 to 35 minutes.

7. During some tests the action offish in the fishway appeared tocause the flow pattern to cheuige

from plunging to streaming. Thechange in flow markedly deterredfish passage. While the delaysin passage were temporary, thereis evidence that the overall pas-sage time in the fishway wasmaterially affected, possiblyslowed as much as 5 minutes orlonger

.

8. Numbers present each minute in a

given pool were obtained for the

three lower pools (55, 56, and 57)

in the season's final test whenthe estimated average weight was13 pounds per fish. A maximumresidence of 239 fish was observedin each of the two lower pools.Maximum residence in the thirdpool was 189 fish. The maximumnumber present in the 6-pool fish-way was 948 fish. Residence in

the first pool (55) remained at a

high level while residence in

17

succeeding upstream pools declinedrather markedly as the experiment

progressed in time.

Fallbacks were observed to occur

in greatest numbers at the dovm-

stream weir of the fishway and

become progressively less numerous

as the fishway was ascended.

ACKNOWLEDGMENTS

LITERATURE CITED

CLEAVER, F. C.

1951 Fisheries statistics of Oregon.Oregon Fish Comm. , Contrib. fflb,

176 pp. , illus.

HOLMES, HARLAN B.

1940 The passage of fish at BonnevilleDam. Oregon Fish Comm. , Contrib.#2— Dams and problem of migratoryfishes, pp. 182-192, illus.

The authors wish to express their

thanks to the following staff members for

their conscientious and industrious efforts

during the conducl of these experiments:

J. R. Gauley, C. R. Weaver, R. S. Rupp,

E. F. Roby, R. J. Holcomb, J. S. Johnson,and R. Foust. Members of the BiometricsUnit of Pacific Salmon Investigations gave

valuable assistance in the review of certainrelationships appearing in the cuialysis of

the experiments. We are also indebted to

Ivan Donaldson, Harry Theus, and Al Chanda(U. S. Army Corps of Enginee/rs) for theirsuggestions and aid in varicus aspects ofthe experiments. Those contributing to the

review of the manuscript included Milo C.

Bell, Joseph A. Craig, Dr. Gerald B. Col-lins, and Clifford J. Burner. Dr. G. B.

Collins was instrumental in much of the

original design of the experiment.

SCHONING, R. W. , T. R. MERRELL, JR.,AND D. R. JOHNSON

1951 The Indian dip net fishery at

Celilo Falls on the ColumbiaRiver. Oregon Fish Comm., Con-trib. #17, 43 pp. , illus.

SILLIMAN, RALPH P. , WILLIS H. RICH,

AND FLOYD G. BRYANT1947 Intraseasonal and interseasonal

variations in average weight ofColumbia River chinook salmon(Oncorhynchus tschawytscha )

,

1939-1945. U. S. Fish and Wild-life Service, Specitil ScientificReport—Fisheries No. 34, 11 pp.,illus.

TAUTI, KCRISABURG, AND KIYOTERU MIYOSI1934 Rate of ascent of fishways by

fishes. Proc. Pac. Sci. Congress(Canada), vol. 5, pp. 3623-3631,illus.

18

APPEIIDIX

Table 2 #—Salmonoid passare by minutes over weirs 54and 60 during July 5, 1956 capacity test,Streaning flov/ developed on v;eir 60 r.t endof minute 3 and continued for remainder oftest.

Table 3,—Count over v/eirs and fallbacks per minute.Capacity test Septenber 7, 1956.

Table 3 (cont'd.) Capacity test September 7, 1956.

Table 3 (oont'd,) Capacity test September 7 , 1956,

Table 3 (cont'd.) Capaoity test September 7, 1956.

Table 4e"llumber of fish in pools by minutes.Capacity test, September 7, 1956-,

Table 4.— (cont'd.) Ccpaoity test, September 7, 1956,

Table 4,— (cont'd) Capacity test, September 7, 1955

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