71).;79

rev. 79-

el

TCJ ~P~gB-SL

Mr. F. J. Kee

Director of Research

.. 

ontario hydro

research division

RESPONSES OF GIZZARD SHAD (DOROSOMA CEPEDIANUM)

TO DIFFERENT FLASH CHARACTERISTICS OF STROBE LIGHT

H. Patrick

The responses of gizzard shad (Dorosoma cepedianum)

to various discharge curves of strobe light were

investigated under laboratory conditions. Flash

characteristics such as rise time and peak duration appear critical in eliciting a fish avoidance

response. With increased duration of light flash

there is less of a fish avoidance response. A

blue filtered strobe, transmitting primarily bluegreen light, appears less effectve as a fish

repellant compared to that of a yellow filtered

(yellow , orange, red light) strobe and white strobe (all visible light).

INTRODUCTION

30th laboratory and field research has indicated the potential

of using strobe light alone or as part of a fish exclusion scheme

(OHRDR 81- 61-K, 81- 190-K, 82- 165-K). Although fish show an

avoidance of this light source, the actual reasons or mechanisms

involved in eliciting this response are only partly known.

Avoidance appears only partly related to light intensities

(OHRDR 79- 104-K, 81- 190-K), and probably unrelated to the

spectral composition of the strobe light source (OHRDR 82- 476-K).

Flash rate appears to be important, however , with noticeable

avoidance occurring when frequency exceeds 200 flashes/minute

(OHRDR 79- 104-K, ~, 476-K. Still, other light sources such as

incandescent and metal halide, when flashed at 200/minute and

higher, are generally ineffective as fish repellants (OHRDR

82-476-K). These light sources differ mainly from strobe in that

the duration of each flash is considerably longer. It 

possible that fish avoidance of strobe light may be related to its short flash duration. To test this hypothesis, a study was

ini tiated to determine the responses of fish to different strobe

discharge curves of varying durations.

iiOb

740634- 526- 092 837 315 July 21, 1982 82- 310-K

file date report no.
MJI_TERI;'.r.S A..'m Y~'I'HODS

Species Investigated

Adult shad , ranging in size from 25 to 40 cm, were used as test species. Fish were collected by electro- fishing techniques in

the winter of 1981 at both Pickering GS and Bruce GS. Prior 

experimentation , fish were held in either 2. 4 or 3. 6 m circular

pools under a controlled photoperiod of 10-14 h of light. Water temperatures ranged from approximately 7. 0 to 9. 5 O c throughout

the testing period.

Types of Discharge Curves

Four different discharge curves of varying rise times and peak

durations were produced by changing the inductance and capaci tance

of the strobe (Figure 1, Table 1). These modifications and curve- values are based on preliminary work conducted by Electrical

Research (OHRDR E81- 75-H). Flash characteristics were measured

using an oscilloscope (Phillips Model PM322) in conjunction with

a photocell. Wi th increased capaci tance and inductance, the

shape of the strobe discharge changed significantly as both rise

times and peak durations were altered. Rise time , de fined as the period (ms) required to achieve peak output (measured between 10- 90% of pe ak output) ranged from 0. 12 ms for curve B to 3. 0 ms for curve E, the latter being approximately 43 times slower than that of a normal strobe discharge. Peak duration , or duration of highest output (measured at 95% of peak output) ranged from 20 ms for curve B to 4. 0 ms for curve E. These peak durations

were at least one order of magnitude longer than that of a normal

strobe flash (curve A). Differences in total duration between

normal ~~d modified discharge curves were less obvious with discharge curve E' only 2. 5 times longer than the normal strobe.

Curves B and C were similar in total duration to the normal strobe (Curve A).

time

TABLE 1

CAPACITANCE k~D INDUCTANCE MODIFICATIONS

TO STROBE LIGHT

Modification Inductan ce (mH) Capaci tance (llF) Area Under Curve (V.ms)

Curve

A Normal 0 . 0

1000

355

351*

364

361*

360*

., .

Intensi ty or area under the curve has been adj usted for curves B. D. and E. by using clear filters, and by slight adj ustmen t

of strobe ' s position in the experimental chambers.

An incre ase in inductance and capaci tance to the strobe unit

resul ted in a reduced flash rate with a maximum rate of only

150 flashes/minute achieved for curves D and E. All other curves (including normal discharge) were adjusted to this flash rate. Based on preliminary observations and earlier work

(OHRDR 79- 104-K) this flash rate was probably at or near the minimum

level at which fish elicited marked avoidance.

- 2 - 82- 310
Curve A

Normal

Curve Rise Time Peak Total

(ms) : Duration (ms) Duration (ms)

Normal

078

O. 72

74. 0

'0. :::=- I

:::

Curve Curve 

~ 3 '0'

:::

Curve 

Curve E

:::

Durati on (ms)

FIGURE 

VARIOUS DISCHARGE CURVES OF STROBE LIGHT USED IN

EXPERIMENTAL DESIGN -3- 158042 RD
Spectral compositions for each modified discharge curve varied

sligh tly from that of the normal strobe (Figure 2). Generally

light was transmitted throughout the entire visible range, with

slightly higher energy output in the orange and red regions of

the spectrum (especially curves B and C). Because of an increased

orange-red content of the discharge, increased fish avoidance

could be expected for these discharge curves (OHRDR 78- 516-K) .

Chambered Experimen ts

Both short (5, 15 minutes) and long (12 h) term experiments were

used to determine the responses of gizzard shad to various discharge curves produced by strobe light. All experimen ts were

conducted in a 2. 4 m diameter circular tank which was divided

equally into three areas, each approximately 1. 5 m2 (Figure 3).

In the design , one chamber was ill umina ted with strobe source

which was the sole source of illumination during the testing period. For each experiment, the strobe light source (modified

or normal) was projected downwards in the tank producing concentric

zones of varying light intensities. Light output in curves B

D and E were higher than that of the normal strobe (Figure I,

area under curve), and had to be adjusted using clear plexiglass filters , and by slight adjustment of the strobe s position in

the experimental chamber. These fil ters had no noticeable effect

on the spectral output of the strobe. Intensity, measured as

area under each discharge curve, varied less than 10% among all discharge curves (Table 1). Strobe light intensities, for all (zlO%) ranged from approximately 333 lux (7.

llEom :) n~ar the light source to approximately l~ lux

(0. 3 llE'm 2 .S 1 ) at the edge of the light zone. Light recorded

near the outer wall was approximately 2. 0 lux (~O. l llEo

The illuminated chamber had no influence on the other two chambers

which were in darkness during the testing period.

In the long term tests, closed circuit T. V. was used to monitor

fish numbers in the lighted chamber (for each discharge curve)

at 10 minute intervals (freeze frame) over the 12 hour monitoring period. One replicate (n = 15 fish) was performed for each discharge curve (except curve E) * The number of shad that entered

the same experimental chamber (strobe source off) over a similar

12 h period under low level light (~3 lux, ~0. 01 llE'm served as a control.

Short term tests consisted of moni toring fish numbers and distribution in the lighted chamber following both 5 and 15 minute illumination periods. Ten replicates (n = 15 fish/replicate)

were performed for both modified and normal discharge curves (total 80 replicates). After each selected time period , chutes

which divided the chambers were closed and the number of shad in

each chamber recorded.

Because of technical difficulties, modified curve E could not

produce light for more than. a 30 minute period.

- 4 - 82- 310
....,

'0 20

:::

oW 15

...., :!

10 

Normal Curve A

Curve 

Curve 

Curve 

Curve E

410 430 450 470 490 510 530 550 570 590 610 630 650 670 690

Wave 1 ength (nm)

FIGURE 2

SPECTRAL COMPOSITION OF VARIOUS DISCHARGE

CURVES OF STROBE LIGHTS (C. W. - QUANTUM METER 3500)

c:- ....0""" 01'"\
2.4m CIRCULAR TANK

Light Source

0 (0) 0 (0)

0(0::1.3) 0(0::1.3)

...... ........................

1(6.

0::0, 1 (2. Chute

Opening

1(5.

0::0. 1(2,

Chamber 

FIGURE 3

LIGHT INTENSITIES MEASURED AS ILLUMINANCE

(LUX, IN BRACKET) AND QUANTUM FLUX (~E. m ':'1

FOUND IN EXPERIMENTAL CHAMBER

- 6 - 158176 RD
~ 10

~ 8-

Q..

~ 18

Q..

lue Filter

Yellow Filter

410 430 450 470 490 510 530 550 570 590 610 630 650 670 690

Wave length Cnm)

FIGURE 4

SPECTRAL COMPOSITION OF A , BLUE AND B YELLOW

FILTERED STROBE LIGHT SOURCES (C. I.W. QUANTUM METER 3500) 158044 RD
Observations were also made on the distribution of shad wi thin each chamber rela ti ve to the light source after closing the chutes. Ten control tests (15 fish/replicate) were also performed for each experimental condition (total 80 replicates)

in complete darkness to assess fish numbers in each chamber in

the absence of strobe light. Control and experimental tests

were alternated to reduce any temporal bias.

Addi tional tests were also conducted to determine the responses

of shad to a normal strobe light source covered with blue or

yellow filters. The blue filter transmitted light primarily

in the 410 and 630 nm visible range, with maxima occurring

in the blue-green region (450- 530 nm , Figure 4). The yellow filter

transmi tted all visible light beyond 470 nm , with highest output

in the yellow (577- 597 nm), orange (597- 622 nm) and red (622- 690) regions of the visible spectrum. Experimental procedure was

similar to that described above for short term (5 and 15 min) tests.

RESULTS AND DISCUSSION

Response of Shad to Various Strobe Discharge Curves

In the long term tests (12 h), an increase in the number of shad

in the lit chamber occurred with an increase in peak duration of the flash (Figure 5). Statistically, the lowest number of fish

was observed in the chamber lit with a normal strobe (curve A)

or with discharge curve B , indicating that shad showed strongest

avoidance of these light sources over the monitoring period

(F4,36o = 195 , p~0. , Appendix C). The number of shad observed

in the chamber lit with discharge curves C and D over the 12 h moni toring period are not significantly different from the control test (Multiple Range Test , Appendix C) . , There was no noticeable

evidence of a change in fish numbers in the experimental chamber

over a 12 h monitoring period for either normal or modified discharge curves (Figure 6). Generally, there appeared to be

fewer fish observed as the monitoring period progressed, suggesting

a slight avoidance of the lit area for all discharge curves.

Al though discharge curve B (rise time 0. 12 ms, peak duration 0.

ms) appeared similar in effectiveness to the normal strobe in excluding shad (averaged over a 12 h period , Figure 5), this avoidance response was not evident in the initial 5 and 15 minutes of experimentation (Figure 7). During these illumination periods,

the lowest mean number of shad was consistently recorded only for the normal strobe discharge curve (Table 2 , Multiple Range Test) .

Relative to control tests , fewest shad numbers were observed in

the chamber lit with normal strobe (curve A) and discharge curve

in the 5 minute tests, and only with the normal strobe following

15 minutes of illumination (Figure 7 , Table 3).

These results indicate that strobe flash duration is critical in elici ting an initial fish avoidance response. Distribution of

fish in the lighted chamber following 5 and 15 minute illumination periods supplemented these data. Fish were frequently

observed near the light source in all modified curve tests, whereas they were generally located near the edge of the tank where

intensi ties were lowest in the normal strobe tests.

- 8 - 82- 310
0 25

~ 20

c..

::) 10

J: 5

t'3 15

::)

25 -

)- 15

::)

u..

NORMAL

80Ws PEAK DURATION

X= 1.8 :: 1.1

CURVE B

200 )JS

CURVE C

700 lJS.

CURVE D

2 OOO~

CONTROL

1.6

NUMBER OF SHAD OBSERVED. IN LIGHTED CHAMBER

FIGURE 5

FREQUENCY OF SHAD OBSERVED IN EXPERIMENTAL LIT ZONE

OVER A 12- HOUR PERIOD

- 9 - 158094-
Normal Curve A

Curve . 'A.~J.v

~A_ NA H'

Time (hours)

11 

0400 1600

FIGURE 6

NUMBER OF SHAD RECORDED IN EXPERIMENTAL CHAMBER

10- 158045 RD
A. 5-MINUTE ILLUMINATION PERIOD

NORMAL STROBE 11 r

c::: 5 Iu.J

(;J

::2: 4 -

::( ...:..

CURVE A

t- 80 \-lS

Peak

- Duration

8 -

7 -

6 rCURVE B

200 II 5

CURVE C

700 II 5

iJ')

u: 

c::: B 15-MINUTE ILLU,\~INATION

!!J

::2:

:::::J 7

6 t5 f4 f3: -

. 

-f-- ill:

!!!!!!!!!!!I!!~!!

PERIOD

 

Ii I--

CURVE D

2 000 \-lS

- r-

-I--

::j::: 

I'"

I E I C 

FIGURE 7

RESPONSES OF GIZZARD SHAD TO

VARIOUS STROBE DISCHARGE CURVES

(E = EXPERIMENTAL , C = CONTROL)

,-- I'-

I E I C

-11-

CURVE E

4000 fl 5 -

Iii

:):E):

....

- rI E I C

158095-
TABLE 2

STATISTICAL COMPARISON OF SHAD NUMBERS RECORDED IN EXPERI~ENTAL

CHAMBER LIT WITH VARIOUS STROBE DISCHARGES

III umina tion Period (min)

F-statistic d. f. Multiple Range (S.

lowest ~ highest numbers

Discharge Curves

:lOrmal \ C 

(A) 

Discharge Curves

\'norma

l D

, C B / (A) '

P~0.

TABLE 3

STATISTICAL COMPARISON (t-VALUES) OF SHAD NUMBERS RECORDED IN

EXPERIMENTAL LIT CHAMBER RELATIVE TO CONTROL TESTS (Figure 

Illumination Discharge Curve Period (min) (Normal)

9 * 3. 7 *

(avoidance) (avoidance)

6 * 1. 0 2. 8 * 1. 9 3. 4 * (avoidance) (attraction) (attraction)

- 12 - 82- 310
Shad Response to Blue and Yellow Filtered Strobes

Shad showed an initial attraction to blue filtered strobe light

(after 5 minutes , Table 4). Mean shad numbers observed in the

experimental lit chamber were significantly higher than that

observed in control tests. In one replicate 13 of 15 fish (or

86% of total) was observed in the lighted chaIT~er (Appendix A) .

However , following 15 minutes of illumination , there was a reduction

in the number of shad recorded in the experimental Ii t chamber,

suggesting a delayed avoidance response (Table 4).

TABLE 4

COMPARISON OF MEAN SHAD NUMBERS RECORDED

IN EXPERIMENTAL LIT CHAMBER RELATIVE TO CONTROL TESTS

1.2

YELLCW F I L TER

Control IExperimental;

Responseu X S. (X~ X S. (X)!Response

! Attract-iI3. 1 1.6 ; 4. 1.9 , ion 

1.9 : avoid- 3 2. 4 2. 2* 1.7 avoidi once :ance 

Illumination

Per iod (min)

BUJE FILTER

Control i ExDerirrental X S. D. (X)! X S. D. (X)

.;,

i? ~O.

In the yellow filtered 5 minute strobe tests, there was no

significant difference between shad numbers recorded between

experimental and control tests , indicating nei ther attraction nor avoidance (Table 4). However, similar to the blue filtered strobe

resul ts, an avoidance was observed with prolonged illumination

(15 min u te s) .

Effect of Strobe Flash Duration on Shad Behaviour

Flash duration appears to significantly influence shad behaviour

wi th less of an avoidance response occurring with increased flash duration. These results confirm the speculation that fish

avoidance of strobe light may be related to the flash characteristics

of the strobe (OHRDR 82- 476-K). However , it should be emphasized

that rise time and peak duration are probab ly more critical than the total duration of the flash in elici ting this avoidance.

Although curves B and C had similar total durations as the normal strobe (curve A), thev were relatively ineffective as a fish repellant (Figures 1 7). Flashing light of short peak duration

such as that produced by a normal strobe (~lOO~s) is foreign

to most fresh-water pelagic species, and generally results i~ disorientation , confusion and avoidance (as observed under

- 13 - 82- 310
laboratory conditions). In marine environments, several

organisms (algae, vertebrates, fish) have evo Ived the ability

(bioluminescence) to repel (or escape from) potential predators

by emitting light of short duration (Herring 1978 , Morin 1982,

pers comm). It is noteworthy that the shape of the flash produced

by these organisms (ie rapid rise time, slow exponential decay)

is almost identical to the discharge curve of strobe light

(although the total duration is much longer).

In addition to flash duration, flash rate has also consistently

been found to be important in eliciting a fish avoidance response

(OHRDR 79- 104-K, OHRDR 82- 476-K). The flash rate used in these tests (150 flashes/min) is probably the minimum at which avoidance will occur. For field applications a lightly higher rate would

be recommended (200- 250 flashes/minute).

Experiments with filtered strobe light have shown that if the blue- green content of the emissions is increased there is

evidence suggesting an attraction (at least ini tially). Attraction

by fish to these wavelengths tends to override their avoidance

of a rapid flash. This can have important implications in field

situations where blue- green light penetrates far in the water

column, since a far field attraction to a strobe light source

may potentially exist when unfiltered light sources are used.

However, as fish move closer to the light source , and other

wavelengths become apparent, an avoidance response should occur.

It is expected that spectral composi tion of a strobe probably

plays a limited role in repelling fish.

SUMMARY

1. Flash characteristics of strobe light such as rise time and

peak duration appear critical in eliciting a fish avoidance

response.

2. With an increase in duration of light flash, there is less of

a fish avoidance re sponse. 3. A blue-filtered strobe light appears less effective as a

fish repellant compared to that of yellow (filtered) and white strobes.

j-A~ 

;lh

~C. H. Clark

Manager

Chemi cal

! ~ I

Approved:

,....

Research Dept

. Patrick

Research Biologist

Biological Research Section

PEP : kwk

- 14 - 82- 310
REFERENCES

Herring, P. S., 1978 (ed), Bioluminescence in Action , Academic

Press. 570 pp.

Morin, J., 1982 (per comm) University of California at Los

Ange les .

OHRDR 78- 516-K , Response of fish to light, P. H. Patrick,

December 29 , 1978.

OHRDR 79- 104-K, Response of gizzard shad to strobe light

H. Patrick, March 26 , 1979.

OHRDR 81- 190-K, Responses of fish to diversion barriers,

H. Patrick, July 29 , 1981.

6 . OHRDR 81- 61-K, American eel response to white strobe light

H. Saunders 1980 , R. S. Sheehan and B. Sim

October 14 , 1981.

OHRDR 82- 165-K, Use of filtered mercury vapour lights in association wi th a modified fish handling pump at

Nanticoke GS. G. T. Haymes, May 14 , 1982.

OHRDR 82- 4 76-K, Responses of fish to flashing lights, H. Patrick.

9 . OHRDR E81- 75-H, Extending the flash duration of strobes, M. Staelter.

- 15 - 82- 310
APPENDIX A

NUMBER OF GIZZARD SHAD KECORDED IN EXPERIMENTAL &~D CONTROL

CHAMBERS IN 5 AND 15 MINUTE TESTS

Time Replicate

Type (min)

Control Chamber 1

Normal Chamber 2

Strobe Chamber 3

Exp

Control

Normal

Strobe

Exp * 1

Control

Exp * 1

Con tro 1

Exp * 1

Control

Exp :~ 1

Control

Exp * 1

Chamber 1 lit in experimental

- 16 - 82- 310
Time

Type (min)

Control Chamber 1

Chamber 2

Chamber 3

Exp * 1

3 extra

Con trol

Exp * 1

Control

Exp * 1

Control

Exp * 1

Control

(yellow) fil ter 11 9

Exp * 1

Con tro 1

(yellow)

fil ter

Exp * 1

11 9 11 5

- 17 - 82- 310
Time Replicate

rrvpe (min)

Control Chamber 1

(Blue)

Exp

Control

Exp * 1

- 18 - 82- 310
APPENDIX 

NUMllEH OF SIIAD HECOHDED IN EXPERIMENTAL 

CIlAMllER FOR EACII 

DISCIIAHGE CUlM' OVER A 12 h PERIOD N umbe r l1trO 1

r-maT StroD

Time

(lOin) 1st 6 hr 2nd 6 hr 1sD hr 2nd 6 hr 1st 6 hr 2nd 6 hr

1st 6 hr 2nd 6 hr

1st 6 hr 2nd 6 hr

0 6

100

200

.

.

300

1 (j

400

500

tJ 0 u
APPENDIX C

ANOVA COMPARISON OF MEAN NUMBER OF SHAD RECORDED IN LIGHTED CHAMBER

OVER A 12 h MONITORING PERIOD FOR VARIOUS STROBE DISCHARGE CURVES

Analysis of Variance

Source

Sum ofSquares Degrees Of Freedom Mean Square Ratio Significance Probabili ty

GroupsWi thin GroupsTotal

6001.10

1467.

677.

8146.

360

365

6001.0959

366. 8014

1. 8825

3187

194

00000000

Mean

MULTIPLE RANGE (S 0 N . K. )

Normal Curve B Curve C Curve D Control

1. 8 1. 9

I-'
. 

, 

..,,

,

Table l. Swimming speed (Vs ) required of fish passing line of louvers for given

approach velocities (V~ and selected angles (0) of t~e line of louvers,

(Vs .. Va Sin 0)

0 f 1. 22 1.46 1.69 1. 93 I~. 02

0::: 5 I 1.13 1. 35 1.57 1. 79 III

;c. 0 I 1.04 1. 25 1.45 1. 65 1.85 3 00 "TJ "TJ

':1\

1 , 11~ 1.33 1.52 1.70 1.88

;I:

0 87 1.04 1. 21 1.38 1. 53 1. 71 :3.

Y2. 1. 24 1.39 1, 51~ 1. 90

0, 8~ 1. 24 1 , li9 ..1...lQ. l.:H

(t)

1.08 1. 20 1.48 1. 75 ~ 0

(t)"TJ

1. 03 1. 27 1.50 1. 72 1. 93

(t)

5 I

-L..Q2.. 1. 25 1.43 1. 61 1. 77

0 I

...L.QQ. .2..:l5... 1. 29

r;:- \ 0, 1.5 ..2..:.22.. .J....QQ.

1.0 42 0,

\..,

ANGLE OF LINE OF LOUVERS (degrees) 0

jo.

, 

:

:

.

:

"""~""i-")"""""""'

.

::

"""""'O"""'O

"""""""""'r"

,.,.

...........o .

, 

.. 

, ,

...,....... .,. 

, 

:

,

.

-r.c...,,,~.