J . Fish Biol. (1986) 29 (Supplement A), 189-197

Migrational swimming speeds of the American shad, Alosa sapidissima, in the Connecticut River, Massachusetts, U.S.A.

H. M. KATZ Great Swamp Research Institute, 49 Lyons Road, Basking Ridge, N.J. 07920, U.S.A.

Of 91 sonic-tagged American shad, 78 were tracked upriver to their spawning grounds. The remaining 13 tagged shad dropped back downstream over a dam or moved downstream through the adjacent canal system. Sonic-tagged shad swam upstream individually. ' Apparent ' swimming speeds (the time to travel between two points) during daylight hours ranged from 1 1 to 93 cm s- when water temperatures were below 20" C and from 9.8 to 64 cm s- when water temperatures exceeded 20" C. Swimming speeds at night ranged from 8 to 53 cm s-'. As the flow rate increased, shad swam faster. A major flood, producing flows reaching 300 cm s- ',flushed all sonic-tagged shad away.

I. INTRODUCTION

The American shad, Alosa sapidissima, has interested United States federal, state, academic, and commercial fisheries scientists for over 130 years (Katz, 1972). In 1966 the Massachusetts Co-operative Fishery Research Unit, University of Massachusetts initiated research into the life history of the American shad in the Connecticut River. The U.S. Fish and Wildlife Service, through the Anadromous Fish Conservation Act, determined that a major effort should be made to use the Connecticut River as a demonstration river to show that anadromous fish (Atlantic salmon, American shad, blueback, and alewife) can be re-established in the river.

I t has long been known that upriver-migrating shad orient into flowing water. However, little is known of how they react to differing currents, or of any preferences for particular velocities. Most variations in swimming speeds have been associated with the migratory season or have been attributed to changes in water temperatures.

By the early 1800s a number of dams had been built across the Connecticut River. Their construction appears to be the primary factor causing major declines in anadromous herring, such as shad, and the elimination of Atlantic salmon from this river (Moffitt, et al., 1982). The Holyoke Dam is the second dam upstream. The first, the Enfield, is not high enough during high water to block upriver- migrating shad. The 9-m high Holyoke Dam requires fish-passage facilities in order to allow shad access to upriver spawning areas. The 57.3-km pool formed by the Holyoke Dam continues upstream to the next dam, the Turners Falls Dam (Fig. 1).

The work reported here is part of the effort to study the migratory behaviour of shad in a section of the Connecticut River known as the Holyoke pool. The purpose of this study was to determine swimming speeds of shad at various times during the migration and to relate these speeds to water velocity.

0022 1 112/86/29A189+09 %03.00/0 189

0 1986 The Fisheries Society of the British Isles

190 H. M. KATZ

FIG. 1.

Turners Falls Dams

U.S.G.A. Montague Gaging Station Fourth Island

4 N

+I90 km - Flow Station 189.1 km Oeerfield River --f

A Flow Station 185-5 km -

I 180 k m d

.

/-

I70 km

Flow Station 161.5 km

Connecticut River, Holyoke Pool in Massachusetts. Holyoke Dam is downstream of Dam.

Turners Falls

11. MATERIALS AND METHODS American shad were obtained at the Holyoke Dam fish lift facility. This elevator-like

device has been in use since the 1960s and is described by Watson (1970) and Katz (1972). Ninety-one shad were sonic-tagged in 1970 (29 tags), 1971 (22), 1972 (17), and 1973 (23), with an ultrasonic tag passed through the mouth into the stomach (details, Katz, 1972). Thirty-one females, 35 males, and 25 shad of unknown sex were sonic-tagged; their annual mean lengths (total length) ranged from 493 to 500 mm in males and from 509 to 583 mm in

MIGRATIONAL SWIMMING SPEED OF SHAD 191

females. On 27 occasions single shad were sonic-tagged and released; on 32 occasions sonic-tagged pairs were released simultaneously. Paired releases reduced the chance of wasted crew time and allowed observation of any shad schooling or swimming in a group. Tagged fish were released at the dam into the upper fishway release channel (UFRC) from which the fish could swim out into the main part of the river and continue upriver migration.

Sonic-tagged fish were monitored with hydrophones used by two-person teams in small, outboard-powered, flat-bottomed boats. The boat crew stayed 200-300 m downstream of the monitored fish. The fish's location was plotted on river maps about every 30 min. Fish were tracked without interruption for up to 58 h. Each sonic tag emitted a different pulse-rate signal, allowing up to 12 to be identified at any one time. A second boat crew surveyed the Holyoke pool each day for shad previously sonic-tagged (Fig. 1).

Water temperatures were obtained with mercury-stemmed thermometers readable to 0.05" C, a continuously-recording thermistor located at the Holyoke Dam, and/or a port- able thermistor. Water velocities were obtained at five locations along the river with a Gurly pigmy flow-meter or a digital flow-meter (General Oceanics model 2031).

Two measurements of shad swimming are examined in this study. The first is apparent speed, a measure of the time it takes fish to travel from one point to another. The second is absolute speed, and includes an estimate of the current that fish must overcome.

111. RESULTS INITIAL DISTRIBU7'iuh

Seventy-eight of the 91 sonic-tagged fish were tracked for varying distances along the river. The remaining 13 fish were believed to have gone below the dam. This could occur if the fish were carried over the dam or entered the adjacent canal system, which was used to divert river water to industrial users nearby, in Holyoke. In 1972 one of the missing tagged fish was discovered c. 2 km downstream of the Holyoke Dam; six were eventually discovered in the canal. In 1973 eight of 23 sonic-tagged fish placed in the upriver Turners Falls Dam pool were detected by survey teams in the Holyoke Pool downstream. Of the 32 paired-tagged fish, none paired with another sonic-tagged individual.

SWIMMING SPEEDS Positive rheotactic response of migrating shad ensures upriver movement.

Connecticut River water velocity varies according to channel configuration, gradient, time of day, and month. Rain and melting snow account for most of the variation, but manipulations of flow for hydroelectricity and flood control also contribute. At non-flood levels, river flows can vary from < 1 cm s-' to 100 cm s- '; a t flood levels flows can reach 300 cm s- '.

Thirteen of the sonic-tagged shad released in 1972 swam upstream during day- light a t apparent speeds of 11-67 cm s- ' (median 44 cm s - '). In 1970 and 1971, as long as water temperature did not exceed 20" C, apparent swimming speeds ranged from 33.3 to 93.0 cm s- and 26.7 to 84.6 cm s- ', respectively. When water tem- perature exceeded 20' C, shad swimming speeds ranged from 23.0 to 44.4 cm s-' (1970) and 9-8 to 64.2cm s-' (1971). Night-time upriver apparent swimming speeds for tagged shad in 1972 ranged from 8 to 53 cm s - '. Water temperatures were much cooler during the 1972 migration period with >20° C temperatures occurring on only 4 days.

EFFECTS OF WATER VELOCITY ON SWIMMING SPEEDS The relationship for 1972 between absolute swimming speed and water velocity

is clear (Fig. 2). At the slower absolute swimming speed of 60.0 cm s- ' shad

192 H. M. KATZ

are swimming against water velocities of 14.8 cm s-'. When the swimming rate increases to 150.0cms-', the fish are swimming against water velocities of 91.7 cm s-'. The relationship between absolute swimming speed (y) and water velocity (x) is described ( r = 0-48) by the least squares regression equation:

y = 50.339 exp (0.012 x) (1) More than 95% of the recorded shad absolute swimming speeds fall within f 40 cm s- of the regression line. For example, at a water velocity of 30 cm s- ' mean observed shad absolute swimming speeds are 72cms-' but can fall any- where within the range 32-1 12 cm s-' (Fig. 2). A linear regression for these data is a poorer fit ( r = 0.07) than the exponential regression.

IV. DISCUSSION

TAGGING SHAD No paired sonic-tagged shad swam with other tagged shad. These fish might

have moved upriver together with untagged fish, but shad that have been observed from bridges appear to swim as individuals (pers. obs.). Leggett & Jones (1973) released four tagged shad simultaneously and reported that these fish moved inde- pendently, with no shoaling. Exceptions to this individual swimming were observed in the pool adjacent to the Holyoke Dam and in the canal next to the dam: in both cases, groups of up to 75 shad shoaled and swam in large circles, moving neither up- nor downstream.

About as many female shad as males were sonic-tagged. Observations gave no reason to believe that males and females differed in migratory behaviour although, in general, female shad entering the Holyoke system were 5 years old and larger than the 4-year-old males.

EFFECTS OF WATER VELOCITY ON SWIMMING SPEEDS Water currents influence swimming speed and travel direction of brook trout,

Salvelinus funtinulis, sockeye salmon, Oncorhynchus nerka, coho salmon, 0. kisutch, and European eel, Anguillu anguilla (Elson, 1939; Lowe, 1952; Ellis, 1966). There are two potential ways to explain how shad respond to water velocity during upriver migration. First, shad, as they migrate upriver, might cue visually on a series of fixed points. Fishes that live in running water apparently maintain their positions by reference to fixed objects (Hynes, 1970), perhaps on the river bottom. Shad could be programmed to swim upriver within some appropriate range of swimming speeds in relation to these fixed points. In this case the fish would alter their speed in direct relationship to the changing water velocity, so as to move upriver within their preferred rates of movement. Cessation of upriver movement would occur only if the fish reached the spawning area, or became disoriented or disabled.

An alternative possibility is that shad react only to the force of the water against which they swim: visual cues would not be needed. Swimming progress could take one of two forms, either a linear or a curvilinear function. If a linear relationship between swimming effort and current were to exist, then the fish would swim harder as the velocity increased. As the water velocity surpassed the fish's ability to

MIGRATIONAL SWIMMING SPEED OF SHAD 193

TABLE I. Effect of water velocity on apparent swimming speed of American shad, Connecticut River (derived from Leggett &

Jones, 1973)

Apparent Change in swimming apparent

speed speed (cm s- ') (cm s- ')

Water velocity (cm s-')

Absolute swimming

speed (cm s- l )

1 .o 1 *o 1 -0 1 .o

40.0 15.2 24.8 50.0 26.2 23.8 60.0 37.2 22.8 70.0 48.2 21.8 80.0 59.2 20.8

overcome the force, it would still swim vigorously against the current, but would be pushed downriver. Such a system could be disadvantageous to the species.

There would be no problem of open-ended energy expenditure if a curvilinear relationship were to exist between swimming effort and water velocity. Shad would offset increasing velocity by swimming harder, but only until an optimum effort level was reached, whereupon effort would decrease in response to additional increases in current. If the current became great enough to push the shad down- stream, the fish might seek slower-flowing waters or swim with a sudden, but short, burst of speed.

Shad may seek the slower-moving water likely to exist near shoreline and bottom. Upriver-migrating, sonic-tagged shad did not move from the main part of the river to the shoreline. It is not known whether shad swim within a few cm of the bottom to avoid the faster currents. The five flow stations at which water velocities were measured (Fig. 1) represented the five characteristic bottom types resulting from the flow regime (Katz, 1972). Measurements were made at particular places where current would be expected to be substantially uniform, and, therefore, it was assumed that any variation in the instantaneous current experienced by a fish was unimportant in this study.

Leggett & Jones (1973) reported a linear relationship between shad absolute swimming speed and river water velocity (Table I). However, their data are limited to a maximum current speed of c. 60cms-'. The curvilinear form becomes apparent when currents in excess of 60 cm s - are included (Fig. 2).

Two factors support the concept of a non-visually cued, curvilinear relationship. First, shad swim at about the same speed both day and night. Unless these fish have night-adapted vision, this suggests that they are using something besides visual cues during upriver migration. Work with young-of-the-year shad under night-time light levels indicates no night-adapted vision (Katz, 1978). In addition, water clarity in the Connecticut River rarely exceeds 2 m while depth can reach 13 m. Second, comparisons of absolute swimming speeds and increasing water velocity show a changing, rather than a fixed, apparent swimming speed rate (Table 11).

For any given Connecticut River water velocity, shad exhibit a wide range of absolute swimming speeds (Fig. 2). The reasons for this may include differences in

194 H. M. KATZ

* a ..

/ I / / / / /

1 /

ooe

0..

e m

I . I I I 50 I00

Water velocity (cm s")

FIG. 2. Relationship in 1972 between absolute swimming speed (cm s- ') and water velocity (cm s- ') in upriver migrating American shad, AIosu supidissima (Wilson). Regression line equation: y = 50~339e0~012x.

fish size, hence possible swimming speed performance, and water temperature, although in this case its influence appears to be small below 20" C (Katz, 1972). Therefore, the swimming speed variation appears to be inherent in the individual fish. Speed differences are thus most likely to be associated with physical and physiological differences among fish.

It is difficult to predict how an individual fish will react to a given current. Shad swimming speed can be predicted from equation (1) (Fig. 2), but the low corre- lation (r=0.48) may restrict its use. The low r supports the idea that swimming speeds are highly variable with respect to the water velocities shad swim against.

Within the water velocity range 15-80 cm s-', equation (1) predicts absolute swimming speeds of 60-130 cm s- '. With the f40 cm s - * variation observed, absolute swimming speeds could vary from 20 to 170 cm s- '. It is unlikely, how- ever, that speeds in the upper part of this range can be sustained because of aerobic

MIGRATIONAL SWIMMING SPEED OF SHAD 195

TABLE 11. Effect of water velocity on apparent swimming speed of American shad, Connecticut River 1972*

Apparent Change in swimming apparent

speed speed (cm s- ') (cm s - l)

Water velocity (cm s- ')

Absolute swimming

speed (cm s - ')

- 2.9 - 1.2

0.1 1 *2 2.0 2.6 3.3 3.8 4.2

60.0 14.8 45.2 70.0 27.7 42.3 80.0 38.9 41.1 90.0 48.8 41.2

100.0 57-6 42.4 1 10.0 65.6 44.4 120.0 73.0 47.0 130.0 79.7 50.3 140.0 85.9 54.1 150.0 91-7 58.3

*Table based on Fig. 2 and equation (1) .

exhaustion, even though Weaver (1965) has shown that shad can swim at 347 cm s- for at least 20 m.

As water velocity increases, so too does absolute swimming speed (Fig. 2). If water velocity remains between 15 and 60 cm s- l , only a minimal variation in apparent swimming speed results (Table I), whereas changes in water velocity above 60 cm s- ' result in substantially-increased apparent swimming speeds (Table 11).

From 30 June to 8 July 1973 a large flood occurred in the Connecticut River (U.S. Geological Survey, 1974). Peak flows at the Montague flow control gauge (Fig. 1) were 2760 m3 s- ' on 1 July. Applying this water volume to regressions previously developed (Katz, 1976) yields water velocities from 125 to 303 cm s-' (Table 111).

Prior to the flood, nine ultrasonic-tagged shad were known to be moving about at different locations in the Holyoke pool. Following the heavy rains, water levels and currents were of such intense magnitude that survey operations were curtailed from 30 June to 6 July. As the water level receded, survey teams were again placed on the river to locate and identify the shad previously known to be active. Four days of searching (7-10 July) revealed none of these fish. Shad catches by gill- netting after recession of flood waters indicated that a few shad were able to circumvent the strong water flow. Of the nine sonic tags functioning when flood conditions occurred, five were expected to run out of power prior to 7 July, when surveys resumed, In view of the mean sonic-tag life for 1973, the sonic tags in the four remaining fish should still have been functioning on 7 July. Since none of the tagged shad was detected after the flood (assuming that the tags were still working), some of the fish may have been pushed out of the Holyoke pool by the unusually fast currents. If a tag went undetected for at least 3 days, it was assumed to be no longer functioning, or it was assumed that the tagged fish had left the Holyoke pool. As water velocity increases, shad increase their swimming effort until they

196 H. M . KATZ

TABLE 111. Water velocity regressions (Katz, 1976) and calculated 1973 flood water velocities at five flow-monitoring stations in the

Holyoke Pool (Fig. 1) ~~

Flood water Station (km)* Water velocity? velocity

(cm s- ')$

146.5 y = 2.6228 + 0-044278~ 125 161.5 y = 15.6090 + 0.038629~ 122 181.5 y = 13.6375 + 0.067920~ 20 1 185-5 y= 9.351 1 +0-071973~ 208 189.1 y = 3.8577+0.108489~ 303

*km from mouth of the Connecticut River (defined by the State of

t y = water velocity (cm s- l); x = water volume (m3 s- ') $calculated with the regressions from a peak flow of 2760 m3 s-

Massachusetts Division of Fisheries and Wildlife)

reach some upper effort limit. During high water the flow rate at 189.1 km was calculated to be 303 cm s- (Table 111). This current speed may have exceeded the shad's ability to counter it.

This research was partly funded by the Northeast Utilities Service Company with additional support from the Massachusetts Cooperative Fishery Research Unit. The Unit is jointly sponsored by the Massachusetts Division of Fisheries and Wildlife, the Massachusetts Division of Marine Fisheries, the U.S. Fish and Wildlife Service, and the University of Massachusetts. More than 50 people from the University of Massachusetts, Holyoke Water Power Company, Essex Marine Laboratory, Massachusetts Division of Fisheries and Wildlife, and several Marinas and fishermen along the Connecticut River offered assistance to this project. Anne Harris Katz aided in field efforts and was particu- larly helpful with editing this paper. This paper is dedicated to the memory of Roger J. Reed, in appreciation of his guidance and support during the field investigation.

References

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MIGRATIONAL SWIMMING SPEED OF S H A D 197

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Watson, J. F. (1970). Distribution and population dynamics of American shad, Alosa sapidissima (Wilson) in the Conneciicut River above Holyoke Dam, Massachusetts. Ph.D. Thesis. Univ. of Massachusetts, Amherst. (Libr. Congr. Card No. Mic. 71-8021). 105 pp. Univ. Microfilms, Ann Arbor, Mich (Diss. Abstr. 31B: 5742-B).

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