The Plecoptera of a Headwater Stream - Native Fish Lab of Marsh

Arch. Hydrobiol. I " I 4 1 494-514 I Stuttgart, Februar 1969

The Plecoptera of a Headwater Stream

(Gaitscale Gill, English Lake District)

ByG.Wayne Minshall

Freshwater Biological Association, Far Sawrey, Ambleside, Westmorland

With 4 figures and 6 tables in the text

As part of an ecological survey of the invertebrate fauna in the River Duddon ( MmrsuALL and KUEHNE in preparation) it seemed worthwhile to study in greater detail one of the major headwater streams. The stream selected was Gaitscale Gill, a stony, cascading, mountain brook situated near the source of the River Duddon. Gaitscale Gill was chosen because it arises at a relatively high elevation, descends rapidly, and is fairly short. It was felt that these characteristics would provide an insight into the distribution of the benthic invertebrates with respect to altitude.

It has long been recognized (Dorms and HISAW 1925, HYNES 1941, AUBERT 1946, KNIGHT and GAUFIN 1966) that a general relationship exists between altitude and the distribution of aquatic insects. Furthermore, it generally is acknowledged that temperature is the prime factor in determining altitudinal zonation. However, the role of temperature has not yet been proven and little is known concerning the mechanisms which bring about such distributions. More studies are needed there-fore before generalizations can be made.

Investigation of Gaitscale Gill revealed a fauna composed primarily of Diptera, Plecoptera, and some Tridioptera (A complete faunal list will be given by MINSHALL and KUEHNE.); there was a striking absence of Ephemeroptera and Gammarus, 2 taxa frequently taken in benthic collections from streams. In this report some findings of the study are given and a comparison is made with other similar streams in the area and with the remainder of the River Duddon drainage. Special attention is given here to the Plecoptera because they are the predominant group in the stream and because their taxonomy is well known (HYNEs 1941, 1958).

The general ecology and distribution of the Plecoptera of the Lake District has been relatively well studied. HYNES (1941) surveyed the stoneflies of the region, particularly in those streams draining into Windermere, and provided a sound base of information on their ecology. MACKERETH (1957) summarized the data on faunal composition, distribution, and food habits of the Plecoptera following 3 years of collecting in Ford Wood Beck. GLEDHILL (1960) made comparisons of the adult stoneflies collected from a high altitude stream (VVhelpside Ghyll) and from a stream at a lower altitude (Ford Wood Beck). Several particularly good studies involving plecopterans have been made elsewhere in Great Britain: these include the investigations by HYNES (1961, 1962); BROWN, CRAGG, and CRISP (1964); and ELLiorr (1967).

The Plecoptera of a Headwater Stream 495

Description of the Stream

Gaitscale Gill (NY 257021-043) lies in the southeast portion of the

English Lake District. It is one of the principal headwater tributaries of the

River Duddon (Fig. 1 b) and is one of several streams emanating from the

METERS

Fig. I. Location of collecting sites. A. Streams in the radial drainage system of which Gaitscale Gill (II) and the River Duddon are a part. B. River Duddon

drainage. C. Gaitscale Gill, elevations given in meters.

496 G. Wayne Minshall

central Cumbrian Mountains to form a radial drainage pattern (Fig. 1 a). The latter condition provides an ideal situation for comparative work, since the result has been a number of streams with similar environmental charac-teristics.

Gaitscale Gill (Fig. 1 c) is a small, rocky stream located on the south-facing slope of Ulpha Fell. The stream originates in a series of bog pools near the base of Crinkle Crags and flows in stair-step fashion to the floor of the Duddon Valley, approximately 2.2 km away (Fig. 2). The locations of the collecting sites are given in Figs. 1 c and 2. Station 18, located on the River Duddon immediately below the entrance of Gaitscale Gill, will also be included in this discussion. The station nearest the source is station 24, located just below the outflow of the lowermost bog pool.

Table 1. Water temperature and discharge at station 21, Gaitscale Gill in 1965/66.

. g g >, bb ca, cv a c) 4 4 cn 0

00 00 CO CO c0 r- CD to CNI 04 1-1 r-4 1-1 v-I

Temperature (°C) 9.2 8.8 0.7 4.2 0.4 0.0 6.3 4.5 7.9 14.1 11.2 12.3 Discharge (ms/sec X 10- ) — — — — 46 35 — 46 58 58 70 46

Except for station 24, all of the stations have similar substratum and flow characteristics. Under normal conditions Gaitscale Gill ranges from 15 cm to 1 m in width and from 2.5 to 10 cm in depth. Average discharge near the mouth (station 21) is about 0.05 m3/sec (Table 1). The substratum consists mainly of bedrock and medium-sized boulders (25 to 40 cm across, although some as large as several meters across are present). The bottom is relatively stable, but appreciable amounts of aquatic vegetation were present at only 2 of the stations: Homeothrix sp., Microspora sp., and Tabel-laria fenestrata (LYNGB.) laITZ at station 20 and Nardia cornpressa GRAY at station 23. The predominant forms of vegetation in the stream are dead grasses (Festuca ovina L., Agrostis spp., Nardus stricta L.) and bracken (Pteridium aquilinium [L.] KuHN), which are blown or washed in from the surrounding watershed and collect in packets beneath the stones. Many of the invertebrates in the stream tend to congregate in these packets of debris.

Station 24 differs from the other collecting sites in substratum and flow characteristics and type of organic matter. The substratum consists of closely packed, broken stones. The water moves almost imperceptibly as it drains out of the bog pool and trickles between the stones. A great deal of finely divided peat, originating in the pools, is interspersed among the stones. Station 18, located below the confluence of Gaitscale Gill and the River Duddon, has a width of about 3.3 m, an average depth of about 23 cm, and an average discharge of about 0.4 ms/sec. The substratum in the Duddon is similar to that in Gaitscale Gill.


Methods Stations 20, 21, and 23 in Gaitscale Gill and station 18 in the River Duddon

were sampled each month from September 1965 through July 1966. However, no collections were made at Station 23 in January or at any of the stations in February due to ice and snow cover. Stations 22 and 24 and the remaining locations in the River Duddon were sampled less frequently, but relatively complete series were obtained for the autumn (October—November), spring (March), and summer (July). Samples of the benthos were taken in timed collections of 5-min duration in Sep-tember, October, and November and of 2-min duration thereafter. All of the results are expressed as numbers per 2-min sample. All collections were taken with a long-handled net having a mesh of 265 p, (25 threads per cm) and attached to a 25-cm square frame. The stream bottom was disturbed by kicking. Collections were preserved in the field with formalin, hand sorted in the laboratory, and transferred to 700/0 ethanol. Total lengths, exclusive of cerci, were determined from preserved specimens placed on a millimeter grid. All measurements were to the nearest 0.5 mm.

Collections of invertebrates from surrounding headwater streams were taken for comparative purposes in late March — early April 1966; these were of 1-min

duration, using a coarse-mesh net (8 threads per cm). Species taken during this period are representative of species present during the autumn and winter but not of those primarily restricted to the summer months (see later).

Two emergence traps were used to obtain an impression of emergence pat-terns at different elevations. A "pyramid" emergence trap (MuNDIE 1956, Fig. 3)

was installed at station 23, and a floating box trap (MuNDIE 1956, p. 9) was used at station 21. Because of the difficulty of reaching station 23, the traps were emptied only after rather long intervals (usually about 1 month) and considerable loss of specimens undoubtedly resulted. In addition, the net at station 21 was torn from its float several times and the entire catch was swept away. The nets were first installed 8 March 1966, after emergence had already begun, and maintained through 19 July.

Water temperatures were recorded with a centigrade mercury thermometer each time the stream was visited. Beginning in January maximum-minimum record-

Table 2. Total numbers of Plecoptera collected at monthly intervals from 3 sites in Gaitscale Gill, Sept. 1965—July 1966. Values for the months of January and February are excluded because some or all of the stations were not sampled during

those months. Station

23 21 20

Leuctra inermis ICEMPNY 2000 1913 1856

Amphinemura su/cico//is (STENTENs) 7 841 854

Capnia vidua KLApALEK 1326 59 34

Leuctra hippopus (KEmpny) 402 109 84

Protonemura meyeri (PicrEr) 19 221 129

Chloroperla torrentium (Pic-rEr) 113 87 91

Brachyptera risi (MowroN) 0 57 26

Diura bicaudata (L.) 11 0 0 Nemurella picteti ICApALEK 0 2 5

Leuctra nigra (OraviER) 5 1 0

Nemoura cambrica (STEPHENs) 3 0 0

Arch. f. Hydrobiologie, Bd. 65 32

800

70O

60

0

500-

III

400..

300-

905

323

1633

1. Leuctra inermis 2.Capnia vidua 3,Leuctra hippopus 4.Amphinemura sulcicoll s 5.Protonemura meyeri 6.Nemoura cambrica 7.Leuctra nigra a Brachyptera risi 0 300

9.Chloroperia torrentium DISTANCE trn,

1 0,Diura bicaudata 11. Isoperla grammatica

1089

1548 526


ing thermometers were buried in the stream at stations 18, 20, and 23 and maintained throughout the remainder of the study. Current velocities were measured by means of a small Ott current meter.

The Species Collected Of the 11 species of Plecoptera collected from Gaitscale Gill (Table 2),

3 were abundant, 4 common, and the remainder rare. These represent nearly half of the species (25) previously recorded from the Lake District (HYNEs 1941), a somewhat surprising situation in view of the apparently monotonous and rigorous conditions found within the stream.

Leuctra inermis was by far the most abundant and uniformly distributed species. Except for Brachyptera risi, the abundant and common forms were collected from all of the stations regularly visited. In contrast the rare forms all were absent from one or more of the collecting sites.

Distribution

The distribution of Plecoptera at all of the stations in Gaitscale Gill and in the River Duddon immediately below the confluence is given in Fig. 2. The histograms are based on percentages in order to stress the relative importance of the various species at each station. The November collections

22 21 20 118 ST A T I ON

Fig. 2. Spatial distribution of Plecoptera nymphs in Gaitscale Gill, November 1965.

were used because they form a series in which all stations and all but one species (Nemurella picteti) are represented. This series also illustrates con-ditions as they existed prior to any losses from emergence.

8 sta 23

6 ( 710)

54

A sta 23 6 (1084)

D sta 23 (128)


Of the 6 sites, station 24 supported the most dissimilar fauna. Capnia vidua and Nemoura cambrica were the predominant forms and only 4 species were present. At the remaining stations there was more uniformity both in species composition and relative abundance of the Plecoptera present. Leuctra inermis always was the most abundant. Capnia vidua and Leuctra hippopus maintained the same rank relative to each other downstream to station 20. There the situation became reversed and at station 18, in the mainstream, Capnia vidua was absent. Amphinemura sulcicollis and Proto-nemura meyeri were present at all stations but their numerical importance varied. Both were rare at station 23. At all of the remaining downstream stations A. suicicollis was the more abundant of the two and made up over 10 percent of the Plecoptera at stations 20 and 21. Protonemura meyeri made up a significant part of the fauna only at station 21. Of the remaining spe-cies, the eventual elimination of Nemoura cambrica below station 22, the possible replacement of Diura bicaudata by Isoperla grammatica (PoDA) in the mainstream, and the isolated occurrence of Brachyptera risi are noteworthy.

Life Histories

The general pattern of the life cycles for most of the Plecoptera occur-ring in Gaitscale Gill is known from previous studies (see especially HYNES

if, a 6

4-

sta 21 (100) II

4

2

S a 20— (211)

S OND JFMAM S ONDJFMAMJJ 1 965 1966 1 965 1 966

Fig. 3. Seasonal size-distributions of plecopteran nymphs from Gaitscale Gill. A. Capnia vidua, B. Leuctra inermis, C. Leuctra hippopus, D. Chloroperla torren-tium. In each life history diagram the mode and size range of nymphs are shown for each month. When a distribution was bimodal, the point was placed midway between the two values. The total number of specimens measured is given in

parenthesis.


1941, 1962; ELLIOTT 1967; and MAITLAND 1966). Notable exceptions are Capnia vidua, Leuctra nigra, and Nemoura cambrica, for which insufficient published information is available. Of these, adequate material was obtained during the present study to provide information on the life cycle of only Capnia vidua (Fig. 3 a).

Data on the life histories of 3 other selected species, Leuctra inermis, L. hippo pus, and Chloroperla torrentium, also are given in Fig. 3. These 3 species were chosen for detailed analysis because they are the only ones which regularly were present in appreciable numbers and at both high (640 m) and low (260 m) elevations (stations 23 and 20, respectively).

Measurements made of specimens of Capnia vidua collected at stations 23 and 21 showed the pattern of development was similar at both stations. Some difference in the modes and ranges of sizes is apparent, but this probably is due to the small sample size at station 21 rather than to any real differences. Recruitment of newly hatched nymphs occurred from September through December, with the smaller nymphs growing rapidly during that period. From the size range of the nymphs taken in September (as opposed to that of October), as well as the absence of nymphs in early August 1966, it appears that hatching of the eggs does not begin until the latter part of August. No further recruitment occurred after December but growth con-tinued through the winter and full-grown nymphs and adults were first taken in March. Adults were collected in March, April, and May at both stations. No adults or nymphs were taken during the summer.

Hatching of Leuctra inermis appears to have begun about the same time at both elevations since recruits (1.5 mm or less) were present in Sep-tember but absent in July at both sites (Fig. 3 b). However, recruitment ended a month earlier at the lower elevation. The bimodal size distribution of nymphs at station 23 is similar to that found by ELLIOTT (1967) following a severe winter. Apparently there were 2 peaks in hatching and the nymphs from the first hatch were always larger than the nymphs from the second hatch. There was some increase in size during the winter but the mode at both stations showed a marked increase between March and April. The first adults were collected in April at both stations and mature nymphs were collected in May, June, and July at station 23 (6, 28, and 31 nymphs, respectively) and April, May, and June at station 20 (2, 13, and 9 nymphs, respectively). The nymphs generally were larger at station 20 than at station 23. The maximum size attained at station 23 was 7.0 mm, whereas at station 20 it was 8.0 mm.

Leuctra hippo pus may have begun hatching earlier at station 20 than at station 23. No recruits were taken at station 20, but they were present in collections at station 23 from September through December (Fig. 3 c). However, it would appear that hatching did not occur at either station


before August. The pattern of development of L. hippopus at station 23 is

similar to that described for Capnia vidua. Individuals of L. hippopus appar-ently grew during the winter and reached a peak in size in March and April.

At station 20, growth had almost terminated by the onset of winter.

Generalizations about the life history of Chloroperla torrentium are less

certain than for the 3 previous species due to the small number of specimens

available for any given month. The life histories apparently were similar at

the 2 stations except that the nymphs matured earlier and disappeared a

month sooner from station 20 (Fig. 3 d). A slight increase in size took place

at both stations during the winter. However, the apparent increase in size

at station 20 between January and March is inconsistent and probably is

accounted for by the small numbers taken.

An apparent anomaly exists in relation to the winter growth of the

species examined. Capnia vidua and Chloroperla torrentium increased in

size during the winter at both locations. Leuctra inermis and L. hippopus,

however, apparently grew during the winter only at the upper station. In

other streams of the Lake District HYNES (1941) found that, in general, the

growth rate of stonefly nymphs was not greatly affected by the cold of the

winter months. Leuctra inermis was an exception to this generalization (HYNES 1941, Fig. 22 c), its growth being similar to that of L. inermis at

station 20 in Gaitscale Gill. In the Walla Brook, Dartmoor, ELLiorr (1967)

noted that growth slowed down in winter for all species with an over-

wintering generation, although the period of slow growth varied from one

to several months depending on the species. He also observed that most of

those with an overwintering generation grew rapidly in November, Decem-

ber, and March, a feature which in general is also common to most of the

Plecoptera of Gaitscale Gill.

Life Histories and Seasonal Abundance

Many of the changes in seasonal abundance are related to life history phenomena, so the 2 topics are best considered together. All of the plecopte-

ram in Gaitscale Gill are species which grow mainly during the cool months

of the year and emerge and complete their flight period by August. Most

of the nymphs present during August are newly hatched. Hatching continues

throughout autumn and into winter and is responsible for the progressive

increase in numbers during that period (Fig. 4). After recruitment ceases or

tapers off, the size of the population remains relatively stable from one to

several months until emergence begins. HYNES (1961) has suggested that

any losses which occur between the cessation of recruitment and the begin-

ning of emergence are attributable to mortality factors. However, he did not

consider the possibility of further recruitment due to drift or non-mortality losses due to drift. All 3 factors could account for some of the irregularities

23

I 000—

320—

201

I SO SO—L2 0

2 1 I I 11111 n5,0-• 1 I I 11 .12 3 I I I

2-1•11111 Chloroperla tocrentium

0 1 I nzs01_21 I. a

0 —111111

:1;1811

36

0

18

71-2: I I I I

3. 1 18 • n. • — _

SONDJFMAMJJA SONDJFMAMJJ A SONDJFMAMJJA

*80— 300

23 4311 i Leuctra Leuctra

inermis hippopus 400—,

o - I 1 1 n. n. ii V MIIV l■

320—

0

n . n . . _ 3n0H

1 04 240—

80— 1 . 40120 . I

1 60—

5121

c = • I 0 " I 1 _ I

1; 400— •0

0 1 I. n. I . -61 8 111

Kio-

246

160 sulcicollis Amphinemur"a 1

00

.40 I

1 4:1211 a_1111^.•

Protonemura S71 III 10121 meyeri

0 2 "

o 1111111.I.

21

Capnia V i dua

320—

240—

1 60—

13 0—

502 G. Wayne Minsball

in the pattern of seasonal abundance for the Plecoptera in Gaitscale Gill. It is known (aim= and MINSHALL 1968) that all of the more abundant Plecoptera in the stream occur in the drift, several in relatively large num-bers; and allow (1967) has shown that the stage in the life history is one

Fig. 4. Seasonal abundance of Plecoptera in Gaitscale Gill (n. s. indicates no sample).

of the most important factors determining the concentration in the drift, the latter being greatest during periods of rapid growth.

Individuals of Capnia vidua, Chloroperla torrentium, Leuctra hippopus, L. inermis, and Protonemura meyeri declined in abundance or disappeared from the collections (or both) sooner at the lower elevations than at the


higher ones. This is in general agreement with certain of the differences in life histories at the various elevations mentioned earlier. The seasonal pattern for Amphinemura sulcicollis was essentially the same for the 3 stations at

which it was common. Individuals of Brachyptera risi, Diura bicaudata, Iso-

perla grammatica, Leuctra nigra, Nemoura cambrica, and Nemurella picteti

were taken too sporadically to provide any insight into the seasonal pattern of their occurrence.

Comparison with other Streams

Other Localities in the Same Drainage System

A detailed description of the Duddon drainage and of the collecting sites is to be published elsewhere (MINSHALL and KUEHNE) and a brief account is given by ELLIOTT and MINSHALL (1968). The location of the

sampling stations is given in Fig. 1 b and a few representative temperatures

are given in Table 3.

Table 3. Minimum-maximum recordings (° C) illustrating temperature extremes at selected stations in the River Duddon drainage.

Mainstream 18 14 13 U**

7 March-29 April° 0-10.6 0-12.2 0-11.7 0.9-11.9 21 June —19 July 10.0-22.8 10.5-18.3

7 Mardi-29 April* 21 June —19 July

Tributaries 17 8 6 5

0.6-12.2 1.1-12.8 1.7-14.4 2.2-12.8 9.4-20.0 10.6-17.2 8.9-19.4 11.7-20.0

" Thermometer at station 14 installed 13 April. *0 Data for Ulpha Water Works, probably representative of stations 2, 4,

and 9.

The Duddon drainage may be separated into 2 distinct basins on the basis of faunal composition: an upper basin, in which Plecoptera are predom-inant and Ephemeroptera and Gammarus rare; and a lower basin, in which Ephemeroptera are predominant and Plecoptera and Gammarus common. Of the stations located along the mainstream of the River Duddon, station 13 serves as a convenient dividing point between the 2 areas. Gaitscale Gill is situated in the upper basin and joins the River Duddon between stations 18 and 19.

The plecopteran fauna of Gaitscale Gill is compared with that of local-ities elsewhere in the Duddon drainage system in Table 4. The species are listed in order of their frequency of occurrence at the various stations. Data are given for autumn, spring, and summer collections in order to

Table 4. Numbers of Plecoptera per 2-minute sample in the River Duddon drainage, including Gaitscale Gill, during November 1965 and March c8 and Ju y 1966. The number in parenthesis indicates the number of stations at which a species was present out of a possible 23.

Station 24°) Gaitscale Gill 23 22 21 20 19

R. Duddon — Mainstream 18 14 13 9 4 2

Upper Duddon Tributaries

15 16 17 12 Lower Duddon Tributaries

11 10 8 7 3 6 5

Altitude (m) 732 641 488 275 260 247 244 190 99 84 53 3 244 214 214 107 114 84 69 236 130 236 53

Leuctra Nov. 378 149 274 422 46 167 90 69 1 3 1 13 83 92 7 9 2 24 5 12 inermis March 1 250 606 370 139 90 162 122 75 12 74 81 99 310 114 12 120 54 3 23 54 49 59

(23) July 68 36 10 4 12 9 2 1 1 1

Leuctra Nov. 183 78 83 10 20 19 21 60 17 3 5 2 34 117 21 13 2 4 7 12 27 hippopus March 12 75 76 43 16 19 43 4 4 1 5 36 12 37 10 1 41 3 7 20 3 8

(23) July 1 2 2 1

Amphinemura Nov. 1 20 61 149 7 9 35 89 13 83 132 1 29 150 20 21 2 16 11 170 5 1 su/cicol/is Mardi 48 246 20 14 53 133 180 75 164 490 20 109 38 120 132 22 329 105 320 38 24

(22) July 1 21 79 24 1 6 24 10 1 1 11 3 1

Protonemura Nov. 6 1 48 4 2 2 11 33 3 16 10 1 23 12 12 4 13 2 5 12 2 7 meyeri March 3 4 33 12 6 7 18 27 2 3 9 4 43 6 3 6 4 5 13 34 1 11

(22) July 2 27 7 1 12 1

Chloroperla Nov. 6 15 9 9 6 3 6 3 2 1 1 8 8 1 1 1 13 1 torrent/um Mardi 5 13 16 9 4 5 10 1 11 17 3 9 12 3 2 3 20 10 1

(21) July 27 7 2 1 2 2 2

Isoperla Nov. 4 6 1 2 1 1 3 16 10 6 22 grammatica March 6 3 1 2 15 12 17 17 14 27

(13) July 4 1 1

Nemoura Nov. 100 1 1 25 cambrica March 68 1 1 2 19 1 1 1 12

(11) July 4

REqs

um a

uAvm

.0

Station 24°) Gaitseale Gill 23 22 21 20 19

R. Duddon — Mainstream 18 14 13 9 4 2

Upper Duddon Tributaries

15 18 17 12 Lower Duddon Tributaries

11 10 8 7 3 6 5

Leuctra Nov. 14 2 1 1 1 2 2 nigra March 2 1 1 1 3

(10) July 1

Brachyptera Nov. 10 6 1 risi March 1 10 6 1 1 3 23 1 3

(10) July

Chloroperla Nov. 5 2 7 1 3 1 1 3 tripunctata March 3 3 5 3

(8) July 2

Capnia Nov. 25 177 94 22 8 vidua March 4 345 65 11 6 3

(6) July

Protonemura Nov. 1 1 2 18 praecox March 9

(5) July 1

Perlodes Nov. 1 1 1 1 microcephala March 1

(4) July

Leuctra moselyi July 1 8 28 2 9 5 1 18 5

Protonemura montana July 1 14 1

Leuctra fusca July 23 11 1 29 26 15 15

°) The November values for station 24 actually are an average of the October and December collections.

The Plecoptera of a Headw

ater Stream

crt 0 crt


emphasize seasonal differences in distribution. In addition to those listed, Dinocras cephalotes (CuRns), Diura bicaudata, Nemoura avicularis MORTON, Nemurella picteti, Perla bipunctata Pic-rET, and Taeniopteryx nebulosa (L.) also were taken but were of such restricted occurrence that they will not be considered further. Of this group, D. bicaudata and N. avicularis were con-fined to the upper basin, N. picteti occurred in both regions, and the remain-der were collected only in the lower basin.

Only 2 of the species listed in Table 4 (Leuctra inermis and L. hippo-pus) were found throughout the Duddon drainage, but 3 others (Amphine-mura sulcicollis, Protonemura meyeri, Chloroperla torrentium) were rather widely distributed. The remainder occurred at less than half of the collecting sites. Of the 7 species absent from Gaitscale Gill but collected elsewhere, all except Protonemura montana were absent from all of the Upper Duddon tributaries examined; all but Isoperla grammatica were absent from the Upper Duddon mainstream. Capnia vidua primarily was restricted to Gaitscale Gill. Leuctra nigra and Nemoura cambrica both had their greatest abundance at station 24 in Gaitscale Gill but, together with Brachyptera risi, occurred sporadically throughout the Duddon drainage. Perlodes micro-cephala, although never abundant, was taken at 4 localities, all in the Lower Duddon basin.

In general, species collected in November were equally abundant and widespread in the March collections. Notable exceptions were Brachyptera risi and Nemoura cambrica, both of which were found at more stations in March. A majority of the species were represented in all 3 series of samples. However, all of these were reduced in numbers in the July collections and only Leuctra inermis, Amphinemura sulcicollis, Protonemura meyeri, and Chloroperla torrentium were represented by more than 10 specimens each. Three species, Brachyptera risi, Capnia vidua, and Perlodes microcephala, were entirely absent from the summer series, while 3 others, Protonemura montana, Leuctra fusca, and L. moselyi, were persent only during the summer.

Other Headwater Streams in the Lake District The fact that Gaitscale Gill forms part of a radial drainage pattern led

to a series of collections designed to test the applicability of conclusions reached for Gaitscale Gill to local headwater streams in general. The results tend to support the conclusion that the composition and dynamics of the invertebrate community in Gaitscale Gill are similar for a number of local headwater streams and may even be common to cool-temperate headwater streams over a much larger area. However, because of the limited nature of the collections, only those species present in the headwater streams and absent from Gaitscale Gill can be listed with certainty; therefore, further collecting will be necessary before any firm generalizations are established.


Pertinent physiographic information for the streams surveyed is included in Table 5, and the relative position of these streams in the radial drainage pattern is shown in Fig. 1 a. For the most part, the streams were

Table 5. A. Plecoptera from streams in the same radial drainage as Gaitscale Gill. The number in parenthesis indicates the number of stations at which a species was present out of a possible 11.B. Location and date of collection of the sampling sites.

A. Station III IV V VI VII VIII IX X XI XII XIII

Leuctra inermis 20 58 6 37 41 4 34 8 36 66 33 (11)

Leuctra hippopus 7 1 — — 1 5 — — 7 — 11 (6)

Amphinemura sulcicollis 5 1 4 6 1 17 22 — 1 — (8)

Protonemura meyeri 6 4 1 1 2 8 2 — 4 4 5 (10)

Chloroperla torrentium 4 3 — 2 4 — 1 1 1 2 2 (9)

Isoperla grammatica — 1 1 2 — 1 9 — — — (5)

Nemoura cambrica — 13 — 3 4 — — 7 — 3 — (5)

Leuctra nigra 1 (1)

Brachyptera risi 1 1 (2)

Chloroperla tripunctata 4 — 1 — 2 — — — — (3)

Capnia vidua 6 (1)

B. Station

Number Stream Drainage

Collecting Site') (Nat. Grid. Ref.)

Elevation') Date (m) (1966)

III Lingcove Beck Esk NY235046 366 29 March IV Upper R. Esk Esk NY224063 390 29 March V Lingmell Gill Irt NY189077 229 19 April VI Lingmell Beck Irt NY197092 122 19 April VII Mosedale Beck Irt NY184094 122 19 April VIII Upper R. Liza Liza NY205114 381 1 April IX Upper R. Cocker Cocker NY196139 92 1 April X Gatesgarthdale BeckCocker NY218143 183 1 April XI Longstrath Beck Derwent NY247085 387 31 March XII Rossett Gill Brathay NY253074 381 31 March XIII Buscoe Sike Brathay NY260054 381 31 March

1) From Ordnance Survey, Lake District 1-inch tourist map 1963.


all similar to Gaitscale Gill in physical characteristics, including origin, elevation, substratum, and flow. By inference one may assume that chemical conditions and temperatures also were similar. In all streams studied the Plecoptera were the predominant forms and Gammarus and Ephemeroptera were absent from all sites except 3. Gammarus pulex (L.), Baetis rhodani (PicrET), and Rhithrogena semicolorata (Curris) were present in Gatesgarth-dale Beck. One specimen of Heptagenia lateralis (Cum.'s) was taken from Lingmell Gill and one of B. rhodani from Mosedale Beck.

Data on the Plecoptera from the headwater stream collections are given in Table 5; for easier comparison the species are listed in the same order as in Table 4. All of the species that occurred regularly in the Gaitscale Gill collections also were taken from the headwater streams, although none of the headwater streams yielded as many as found in Gaitscale Gill. Lingcove Beck supported 7 of the 11 species found in Gaitscale Gill and 3 others (Upper River Esk, Mosedale Beck, and Rossett Gill) had 6 each. The remainder all had 5 or less of the 11 species. Diura bicaudata was absent or rare in all of the streams examined. It was collected at only 1 site other than station 23 (Roughcrags Gill, station I, Fig. 1 a; elev. 490 m). The only species not found in Gaitscale Gill, but which occurred in 5 of the 11 headwater streams, was Isoperla grammatica. The species most frequently absent from the headwater stream collections were Capnia vidua, Leuctra nigra, Brachyptera risi, and Chloroperla tripunctata, all of which were of limited distribution in the Duddon drainage too.

The species which were widespread in the Duddon streams also occurred in the greatest number of headwater streams. Only Leuctra inermis

was found in all 11 of the headwater streams, but Protonemura meyeri was present in all except Gatesgarthdale Beck. Leuctra hippopus, which was universally present in the River Duddon and its tributaries, was found in only slightly over half of the headwater localities.

Discussion There are several features of the findings for Gaitscale Gill which stand

out and, when considered in perspective, appear to be interrelated. The first of these is the predominance of stoneflies over all other forms of aquatic invertebrates, a feature common to all of the streams in the Upper Duddon

basin as well as most of the other headwater streams examined. Apparently there is some factor (or factors) which is limiting to groups such as the Ephemeroptera but favorable to or neutral in its effect on the Plecoptera. KAMLER (1965) noted a similar phenomenon during a study of mountain streams in Poland. She found that the streams which varied most in temperature over a 24-hr period had more Ephemeroptera in relation to Plecoptera in terms of both numbers of species and density. Similar conclu-


sions were reached for the River Duddon (MINSHALL and KUEHNE in prepa-

ration), where it was concluded that temperature differences were one of

the chief causes of the pronounced dissimilarity in community composition

between the upper and lower basins.

A second important finding has to do with the composition of the

plecopteran fauna in Gaitscale Gill. Most of the species which occurred in

Gaitscale Gill were widely distributed throughout the entire Duddon

drainage, indicating a wide range of tolerance for these species. On the

other hand, Capnia vidua, which was found only in Gaitscale Gill and a few

other headwater streams, generally is considered to be a cold-water steno-

therm (AuBERT 1946). Finally it is significant that the summer-growing

forms (e. g., Leuctra fusca and L. moselyi) were absent from Gaitscale Gill

and the remainder of the Upper Duddon. These facts suggest that temper-

ature may play an important role in determining the community compo-

sition of Gaitscale Gill. However, temperature is not the only important

factor, as attested by the presence, in relatively large numbers, of Nemoura

cambrica at station 24 only and the absence of such potential high altitude

or cool temperature forms as Chloroperla tripunctata, Perlodes microcephala,

and Protonemura praecox (MowroN) (see BROWN, et al. 1964). This suggests

that factors such as food, substratum, and flow characteristics also can be

critical.

It is also of interest to compare the plecopteran fauna of Gaitscale Gill

with that of another Lake District stream: Ford Wood Beck. The two provide

a good contrast between a typical cool mountain stream draining an unpro-

ductive hinterland and a typical warm lowland stream flowing for most of

its length through agricultural land. The Plecoptera of the 2 streams are

listed in Table 6. Due to variations in sampling, number of stations, and so

forth, the chief differences that can be accorded significance are those

concerning species diversity. Sixteen species of Plecoptera were collected

from Ford Wood Beck (MACKERETH 1957) as opposed to 11 from Gaitscale

Gill. Six of the 8 species which occurred in Ford Wood Beck and not in

Gaitscale Gill were restricted to the lower basin of the River Duddon. Only

3 species were found in Gaitscale Gill and not in Ford Wood Beck; these

same species did not occur in the Lower Duddon drainage. Although it is

impossible to determine from the present data what factors are responsible

for the differences between the 2 streams, it seems likely that temperature

and food are among the most important. The similarity of the Ford Wood

Beck fauna to that of the Lower Duddon and of the Gaitscale Gill fauna to

that of the Upper Duddon is striking and further supports the contention

that temperature and food may be prime factors in determining the distri-

bution of the Plecoptera.


The "within stream" differences in distribution of the Plecoptera of Gaitscale Gill are another important aspect of the present study. In spite of the fact that most of the species present in Gaitscale Gill were widely distributed throughout the Duddon drainage, there was pronounced local variation in abundance within the stream. Some of these variations appear to be progressive changes primarily associated with differences in altitude.

Table 6. Comparison of the plecopteran fauna in 2 Lake District streams: Ford Wood Beck, a lowland stream, and Gaitscale Gill, a mountain stream. The data are expressed as percentages of the total numbers collected. Values for Ford Wood Beck were calculated from data given by MACICERETH (1957: Table 3; fine net only, exclusive of station 4); those for Gaitscale Gill were determined from Table 2 of this paper. A plus (+) indicates that the species was taken at some time other than the period represented here.

Ford Wood Bedc Gaitscale Gill

Nemoura cambrica 45.1 <1 Leuctra hippopus 13.6 5.8 Isoperla grammatica 8.9 Leuctra inermis 7.3 56.3 Chloroperla torrentium 6.5 2.8 Amphinemura sulcicollis 5.9 16.5 Leuctra fusca 5.2 Perla bipunctata 3.0 Protonemura meyeri 2.7 3.6 Leuctra nigra <1 <1 Perlodes microcephala <1 Protonemura praecox <1 Chloroperla tripunctata <1 Brachyptera risi <1 <1 Leuctra moselyi Nemoura erratica Capnia vidua 13.9 Diura bicaudata <1 Nemurella picteti <1

Total number 4073 10,245

For example, Leuctra hippopus and Chloroperla torrentium were most abundant at station 23, indicating that conditions at the higher elevations were most suitable in spite of the apparent wide range of tolerance of the 2 species. Incidentally, both species were most abundant at the higher elevations (440 m) in the Af on Hirnant (HYNEs 1961). Other species, such as Amphinemura sulcicollis and Protonemura meyeri attained their greatest abundance within Gaitscale Gill at the lower elevations. The distribution of A. sulcicollis seems to indicate that this species is near the limits of its range as far as altitude and associated factors in the River Duddon are


concerned. On the other hand, P. meyeri appears to have the potential to exist at elevations higher than station 23, even though the most suitable conditions for it exist at station 21. It occurs up to the sources of other streams at 610 m in the Lake District (HYNES 1941). In the Afon Himant HYNES (1961) found it most abundant at 235 m, the lowermost collecting site; A. su/cico//is decreased in abundance above an elevation of 280 m in the same stream. It should be noted however, that Gledhill (1960) collected adults of A. su/cico//is from Whelpside Ghyll at an elevation of 670 m.

Capnia vidua was restricted to Gaitscale Gill and was most abundant at station 23. As mentioned earlier, C. vidua is considered to be a cold-water stenotherm. It is characterized as being a true boreo-alpine species (AuRERT 1946) and is common in streams of the Moor House National Nature Reserve at elevations above 490 m (BROWN, et al. 1964). Capnia vidua has not been reported from any of the 3 British streams that have been adequately studied ( MACKERETH 1957, HYNES 1961, ELLIOTT 1967). GLEDHILL (1960) records it as being rare in Whelpside Ghyll.

Leuctra inermis was fairly evenly distributed throughout Gaitscale Gill. HYNES (1941) records this species from small stony streams and stony rivers in the Lake District, with the nymphs occurring up to the sources of streams above 610 m.

One other topic that bears further consideration is the variation in life histories exhibited by Capnia vidua, Chloroperla torrentium, Leuctra hippo-pus, and L. inermis at different elevations in Gaitscale Gill. Leuctra inermis is the only one of the group that was equally abundant at both the upper and lower altitudes. Perhaps in keeping with this, L. inermis was also the only one which persisted at both sites for the same length of time. In contrast, the nymphs of the 3 remaining species, all of which were most abundant at the higher altitudes, persisted longer (by at least a month) at station 23 than at the lower elevations. Near the mouth of Gaitscale Gill their peak in numbers became reduced sooner, the nymphs disappeared from the collections earlier, or both.

Two of the species studied, C. torrentium and L. inermis, were collected during mid-summer (July). It is interesting to note, that except at station 10 (C. torrentium) and station 4 (L. inermis), all of the nymphs found in the Duddon drainage during July were restricted to the upper basin and the greatest numbers were found at the highest elevations. Furthermore, it is known (ELLIOTT and MINSHALL 1968) that the emergence periods of C. tor-rentium and L. inermis (as well as those of Amphinemura sulcicollis, Leuctra hippopus, and Protonemura meyeri), were later in the Upper Duddon basin than in the lower basin. &Lion' (1967) found full grown nymphs of C. torrentium late into the summer, following a severe winter which apparently


retarded their growth. He concluded that their absence in other summers therefore was not due to the lethal effect of high water temperature.

Other workers also have noted the apparent effect of altitude on the life cycle and in general the present findings agree with their data. GLEDHILL

(1960) determined that Leuctra hippopus, L. inermis, and Chloroperla torrentium emerged earlier and over a shorter period in a warm lowland stream (Ford Wood Beck: elevation about 45 m) than in a high mountain stream (Whelpside Ghyll: elevation about 669 m). MAITLAND (1966) reported that the development of Amphinemura sulcicollis in the River Endridc, Scotland, takes longer in the upper reaches of the river, and most of the nymphs do not emerge until after June. He suggested that both this variation and, to some extent, the distribution of the nymphs were related to temperature requirements.

That temperature is intimately related to the differences in life cycles is supported by the findings of ELLIOTT (1967). He discovered that the emergence of A. sulcicollis, C. torrentium, Isoperla grammatica, L. hippopus, L. inermis, and Protonemura meyeri was much later following a severe winter than in other years. Apparently the growth of nymphs was retarded by the low temperatures and development took longer, resulting in a later emergence. BRINCK (1949) found that many species of stoneflies are affected by climatic conditions. For many species he recorded a progressively later emergence associated with increasing severity of the winter from southern to northern Sweden. Further studies in northern Sweden (SvENssox 1966) support BRINCK'S findings and indicate that the growth of nearly all of the species observed (including Protonemura meyeri and Leuctra hippopus) declines with a decrease in temperature in the autumn and stops completely at temperatures slightly above 0° C.

Acknowledgments I would like to acknowledge the help and facilities provided me by the Direc-

tor and staff of the Freshwater Biological Association. I am particularly indebted to Dr. T. T. MACAN, who suggested the study and helped with it in a number of ways. Special thanks also are due to Dr. R. A. KUEHNE, Dr. J. M. ELLIOTT, P. BARNES, and my wife, J. N. MINSHALL, for their assistance. The study was made possible by a NATO Post-doctoral Fellowship in science.

Summary Standard (timed) collections were made at monthly intervals from 3 sites

located at different elevations in Gaitscale Gill, a small headwater tributary of the River Duddon. Other, less frequent collections were made elsewhere in the stream, throughout the adjacent (Duddon) drainage system, and in surrounding headwater streams.

Of a total of 11 species of Plecoptera collected from Gaitscale Gill, Leuctra inermis, Amphinemura sulcicollis, and Capnia vidua were abundant and Leuctra


hippopus, Protonemura meyeri, Chloroperla torrentium, and Brachyptera risi were common. A similar fauna occupied the other headwater streams examined, but there were notable faunal differences between the upper and lower basins of the River Duddon. Most of the species which occurred in Gaitscale Gill were widely distributed throughout the entire Duddon drainage. Seven species found elsewhere in the Duddon did not occur in Gaitscale Gill; all but 2 of these were confined to the Lower Duddon. Only one species (Capnia vidua) appeared to be restricted primarily to Gaitscale Gill.

Leuctra inermis and Protonemura meyeri were widespread both in the headwater streams and in the Duddon. Leuctra hippopus, which was universally present in the River Duddon and its tributaries, was found in only slightly over half of the headwater streams. Data on seasonal abundance of the more common species in Gaitscale Gill are considered in light of life history phenomena. Informa-tion on the life histories of Capnia vidua, Leuctra hippopus, L. inermis, and Chloroperla torrentium are given for both an upper (640 m) and a lower (260 m) collecting site. Some differences in life histories were noted which appear to be related to differences in altitude. A consideration of the species present and their abundance at the various collecting sites, life history data, and the results of other workers suggests that the principal factors affecting the distribution and abundance of the Plecoptera in the streams studied may be temperature and (or) food.

Zusammenfassung Zeitlich standardisierte Aufsammlungen wurden in monatlichen Abstanden an

3 Probestellen unterschiedlicher Hohenlage im Gaitscale Gill, einem kleinen ZufluB des Flusses Duddon, vorgenommen. Weitere weniger haufige Aufsammlungen wurden an anderen Stellen des Bathes, im angrenzenden (Duddon) AbfluBsystem und in Zufliissen in der Umgebung durchgefiihrt.

Von insgesamt 11 im Gaitscale Gill gesammelten Plecopterenarten waren Leuctra inermis, Amphinemura sulcicollis und Capnia vidua haufig, Leuctra hippo-pus, Protonemura meyeri, Chloroperla torrentium und Brachyptera risi allgemein vorhanden.

Die anderen untersuchten Zuflasse besaBen die gleiche Fauna. Bemerkens-werte faunistische Unterschiede wiesen das obere und untere FluBgebiet des Dud-don auf.

Die meisten der Arten, welche im Gaitscale Gill auftraten, waren auch im Ab-iluBsystem des Duddon weit verbreitet. Sieben Arten, vvelche an verschiedenen Stel-len im Duddon gefunden wurden, waren im Gaitscale Gill nicht vorhanden. Alle diese Arten, bis auf zwei, waren auf den unteren Duddon beschrankt. Nur eine Art (Capnia vidua) schien vor allem auf den Gaitscale Gill beschrankt zu sein.

Leuctra inermis und Protonemura meyeri waren sowohl in den Zufliissen als auch im Duddon weit verbreitet. Leuctra hippopus, welche iiberall im Duddon und semen Zuflassen vorhanden war, kam nur in etwas iiber der Halite der Bathe des Oberlaufes vor.

Die Werte iiber die jahreszeitliche Haufigkeit der haufigeren Arten im Gaitscale Gill werden unter dem Gesichtspunkt ihrer Lebensgeschichte betrachtet. Einzelheiten iiber die Lebensgeschichte von Capnia vidua, Leuctra hippopus, L. inermis und Chloroperla torrentium werden sowohl fiir eine holier (640 m) als auch eine tiefer (260 m) gelegene Probestelle mitgeteilt. Einige Unterschiede, welche auf die unterschiedlichen Hohenlagen zuriickzugehen scheinen, wurden angemerkt.

Archiy f. Hydrobiologie. Bd. 65 33

514 G. W. Minshall, The Plecoptera of a Headwater Stream

Die Betrachtung der vorhandenen Arten und ihrer Haufigkeit an den ver-schiedenen Probestellen, ihre Lebensgeschichte und die Ergebnisse anderer Autoren weisen darauf Mn, dall die Hauptfaktoren, welche die Verteilung and HaufigIceit der Plecopteren in den untersuchten Bachen beeinilussen, die Temperatur and (oder) die Nahrung sein konnen.

Literature Cited AUBERT, J. (1946): Les Plecopteres de la Suisse Romande. — Mitt. Schweiz. Ent.

Ges. 20: 7-128. Mimic, P. (1949): Studies on Swedish stoneflies (Plecoptera). — Opusc. Ent. Suppl.

11: 1-250. BROWN, V. M., CRAGG, J. B., & CRISP, D. T. (1964): The Plecoptera of the Moor

House National Nature Reserve, Westmorland. — Trans. Soc. Brit. Ent. 16: 123-134.

DODDS, G. S., & HISAW, F. L. (1925): Ecological studies on aquatic insects. IV. Altitudinal range and zonation of mayflies, stoneflies, and caddisflies in the Colorado Rockies. — Ecology 6: 380-390.

ELLIOTT, J. M. (1967): The life histories and drifting of the Plecoptera and Ephem-eroptera in a Dartmoor stream. — J. Anim. Ecol. 36: 343-362.

ELLIOTT, J. M., & MINSHALL, G. W. (1968): The invertebrate drift in the River Duddon, English Lake District. — Oikos 19: 39-52.

GLEDHILL, T. (1960): The Ephemeroptera, Plecoptera, and Trichoptera caught by emergence traps in two streams during 1958. — Hydrobiologia 15:179-188.

HYNES, H. B. N. (1941): The taxonomy and ecology of the nymphs of British Plecoptera with notes on the adults and eggs. — Trans. R. Ent. Soc. Lond. 91: 459-557. (1958): A key to the adults and nymphs of British stoneflies (Plecoptera). — Sci. Publs. Freshwater Biol. Assoc. 17: 1-86. (1961): The invertebrate fauna of a Welsh mountain stream. — Arch. Hydro-biol. 57: 344-388.

— (1962): The hatching and growth of the nymphs of several species of Plecoptera. — Int. Kongr. Ent., Wien. Symposium 13: 269-273.

KAmLER, E. (1965): Thermal conditions in mountain waters and their influence on the distribution of Plecoptera and Ephemeroptera larvae. — Ekologia Polska 8: 377-414.

KNIGHT, A. W., & GAUFIN, A. R. (1966): Altitudinal distribution of stoneflies (Plecoptera) in a Rocky Mountain drainage system. — J. Kansas Ent. Soc. 39: 668-675.

MACKERETH, J. C. (1957): Notes on the Plecoptera from a stony stream. — J. Anim. Ecol. 26: 343-351.

MAITLAND, P. S. (1966): The distribution, life cycle, and predators of Amphinemura suleicollis (SrEpHENs) (Plecoptera) in the River Endridc, Scotland. — Ento-mologist 99: 72-81.

MUNDIE, J. H. (1956): Emergence traps for aquatic insects. — Mitt. in Ver. Limnol. 7: 1-13.

SVENSSON, P.-0. (1966): Growth of nymphs of stream living stoneflies (Plecoptera) in northern Sweden. — Oikos 17: 197-206.

The address of the author: G. WAYNE MINSHALL, Asst. Professor of Zoology Department of Biology, Idaho State University, Pocatello, Idaho 83201, USA

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