General
Studying
behavioural responses of animals in experimental conditions, ethologists have
found relatively simple stimuli that could be more effective than the natural
objects. Single spots (called also eye-spots) and two horizontally arranged
spots, rectangular longitudinal stripes,
periodic gratings and other stimuli (Fig.1) belong to them. Because the foregoing
stimuli are not exact imitations of the natural objects, we will call them amimetic stimuli. In several articles,
we will group the main visual amimetic stimuli and describe how they are used
in the ethological research, whether they occur in the nature as well as their application
in the fishing lure industry.
In
the framework of applied ethology, we will address to the fishing lure
industry. It is that only sphere of the human activites, where artificial
stimuli and models of the various animals are used in the largest scale.
Figure
1. The basic visual amimetic stimuli
Names
of the basic visual amimetic stimuli used in this article:
01.
Concentric spots
02. Two horizontal spots 03. 2D & 3D roundish stimuli 04. Rectangular stripes 05. Periodic gratings 06. Chains 07. Vibrators 08. Spinners (rotating stimuli) 09. Flutters 10. Undulators 11. Pulsators 12. Mechanical & light flashers
Note,
stimuli 05 and 06 are periodic spatial, whereas stimuli 07, 08, 09, 10, 11, and
12 are periodic spatiotemporal
In
the terminology of early ethologists, some of the amimetic stimuli shown above called
the sign stimuli (e.g., Manning &
Dawkins, 1998). Generally, using simple stimuli and changing parts of complex
stimuli, scientists were able to find the so called supernormal stimuli that induced in animals the more strong
behavioural responses than the modelling natural objects.
For
example, the giant cane toads, Bufo
marinus, respond to the horizontally moving rectangular longitudinal stripes (20
mm long x 2.5 mm high) much more actively (on average of 10 times) than to live
crickets and insect plastic models (Robins & Rogers, 2004). Similarly,
reproductive males of the common toad, Bufo
bufo, prefer (in four cases against one) to form sexual pairs (Fig.2) with the
fixed blue discs (5 cm diameter) than with the live mobile females (Gnyubkin
& Kondrashev, 1978).
Figure 2. Reproductive males of toads prefer to congregate sexual pairs with blue discs than with live females
Manning
and Dawkins (1998) give many other examples of this kind.
Neuroethology
Visual
amimetic stimuli induce numerous behavioural responses in many animals and do
not imitate, as
mentioned above, the
concrete natural objects. The effectiveness of these stimuli is grounded on the common mechanisms of visual
perception, common for all visually guided animals. Among visual amimetic
stimuli, the nature of spots, stripes and gratings, both static and moving, as
well as rotating striped drums is most studied.
For example,
in fish and other
vertebrate animals, spots are detected at the level of ganglion cells of
retina, which have the more or less distinct concentric receptive fields with the
antagonistic center and periphery. According to Horn (1962; see Fig. 6.5 b,c), the boundaries of some spot are distinguished
depending on its size by one or several ganglion cells with the foregoing
receptive fields. Rectangular stripes and periodic gratings appeared in the
field of view are detected by the so called orientation selective ganglion
cells (e.g., Damjanović et. al., 2009). It is shown in numerous
electrophysiological tests that the cells of this type are represented by two
relatively distinct units called,
respectively, the detectors of horizontal lines and the detectors of vertical
lines.
In addition, on an example of developing larval
zebrafish, Brachydanio (Danio) rerio,
as an usable model object, neuromotor grounds of the behavioural responses to
artificial and natural visual stimuli are studied, in the larva development
(for review, see Portugues & Engert, 2009):
1) responses to large-filed moving
vertical gratings, called optomotor responses
2) responses to live parameciums and small
moving spots, called prey tracking
3) responses to large moving spots and
other large objects, called escape responses
Among other
mechanisms of adjusted effectiveness of amimetic visual stimuli matched with
the corresponding receptive fields, bilateral symmetry of spots and spatial
symmetry of gratings play an exceptionally inportant role (e.g., Kenward et
al., 2004). The effectiveness of pair stimuli is determined by the bilateral
symmetry of visual system and visual perception evolving during millions of
years in the field of the
Earth gravitation, but
the causes of the evolution of repetitive stilmuli and the corresponding
receptive fields are unclear. Kenward et al. (2004) consider about ten
factors that might lead to the evolution of repetitive visual stimuli and the
corresponding receptive fields, including the highest detectableness of
repetitive stimuli on the background of environmental optic noises.
In addition
to spatial amimetic visual stimuli, there are more complex spatiotemporal
amimetic visual stimuli (for review, see, e.g., Rothental, 2007). In
fish, responses to such spatiotemporal stimuli as rhythmic (temporal symmetric)
pulsations, vibrations and (worm-like) undulations are innate. In contrast to the spatial periodic gratings (Damjanović et al., 2009),
there are not distinct receptive units to detect these complex stimuli.
Basic References
Damjanović
I., Maximova E.M., Maximov V.V.
2009. On the organization of receptive fields of orientation-selective units
recorded in the fish tectum. Journal of Integrative Neuroscience 8, 323–344
Gnyubkin
V.F., Kondrashev C.L. 1978. Pair aggregation in the common toad, Bufo bufo L., in the reproductive
period. In: Mechanisms of animal vision. Moscow,
Science, 40-75
Horn
G. 1962. Some neural correlates of perception. Viewpoints in Biology.
Butterworth & Co. Publishers, London, p. 240-285
Kenward B.,
Wachtmeister C. A., Ghirlanda S., Enquist M. 2004. Spots and stripes: the
evolution of repetition in visual signal form. Journal of Theoretical Biology
230, 407-419
Manning
A., Dawkins M.S. 1998. An introduction to animal behaviour. 5th editon. UK, Camdridge
University Press
Portugues
R., Engert F. 2009. The neural basis of visual behaviors in the larval
zebrafish. Current Opinion in Neurobiology 19, 1–4
Robins A., Rogers L.J. 2004. Lateralized prey-catching responses
in the cane toad, Bufo marinus:
analysis of complex visual stimuli. Animal Behaviour 68, 567-575
Rothental G.G. 2007. Spatiotemporal dimensions of visual
signals in animal communication. Annual Review of Ecology, Evolution and
Systematics 38, 155–78
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Saturday, July 28, 2018
Visual amimetic stimuli: An antroduction
Friday, July 27, 2018
Ultraviolet colors in fishing lures
Rapala VMC Corporation manufactures and
sells artificial fishing lures with the ultraviolet (UV) finishes that
combine fluorescent paints, reflective surfaces and optical brighteners
(see http://rapala.fishing/lure-finishes).
Lures with theses finishes are marked by signs “UV BRIGHT” or simply
“UV”. However, Rapala does not understand the abilities of ultraviolet
(with the wavelength below 400 nm) vision in fish and its role in their
responses to UV reflected objects in the nature and fishing.
Fig. 1. The sigh used by Rapala (brands Rapala, Storm, Blue Fox and Luhr Jenssen) to mark the lures with the UV finishes.
UV finishes in mafacturing fishing lures are also used by other companies like Lakeland Inc., USA (see http://lakelandinc.com/UFI/UFI_vibrant.html).
Ultraviolet vision
Freshwater fish
Numerous freshwater small-sized fish like three-spined stickleback, Gasterosteus aculeatus,
reflect (Rick et al., 2004) radiation in the ultraviolet part of the
electromagnetic spectrum and have UV vision. In particular, three-spined
stickleback use UV vision in schooling (Modarressie et al., 2006),
sexual (Rick & Bakker, 2008) and foraging (Rick et al., 2012) behavioural responses. The similar results are found for guppy, Poecilia reticulata (Smith et al., 2002), sailfin molly, P. latipinna (Palmer & Hankison, 2015), and other freshwater small-sized fish in the adult age.
However, UV reflection by some body does not provide the success per se.
For example, during the nest decoration in artificial conditions males
of three-spined stickleback choose rather red foil strips which absorb
UV radiation than silvery or blue foil strips which reflect UV radiation
(Östlund-Nilsson & Holmlund, 2003).
In turn, yearlings of predatory brown trout, Salmo trutta,
use UV reflection of three-spined stickleback to hunt these prey
(Modarressie et al., 2013). However, only young trout are sensitive to
UV (see data by Bowmaker & Kunz, 1987, for Salmo trutta; Hawryshyn et al., 1989, for Salmo gairdneri), while older (over two years) fish lose this ability.
The same ontogeny of UV vision is
typical for other freshwater predatory fish like perch and others (see
Bowmaker, 1990). With the age, the ocular structures change radically
and do not allow the fish to perceive UV radiation.
Saltwater fish
Great care must be taken in relation to
marine fish and invertebrates (like crustaceans) many of which have UV
vision (Losey & Cronin, 1997; Siebeck & Marshall, 2001; Losey et
al., 2003).
According to Fritsches et al. (2000),
marine predatory fish of the younger age groups and medium-sized fish
(like slimy mackerel, Scomber australasicus, and others) are sensitive to UV, while marine predatory fish of the older age groups and large-sized fish (like blue marlin, Makaira nigricans, black marlin, Makaira indica, sailfish, Istiophorus platypterus, and others) are UV blind.
In general, UV signals are mainly used
by small-sized and juvenile fish (both freshwater and saltwater) to form
private communuication channels that are relatively inaccessible for
potential predators (Siebeck, 2014).
Thus, UV finishes of Rapala’s lures and
lures of other companies are useless for freshwater and saltwater
predatory fish of the older age groups which lose UV vision with the
age.
Optical brighteners
In addition to reflective
surfaces, Rapala uses optical brighteners. The use of optical
brighteners complicates the description of the optical properties of UV
fishishes.
It is well known that optical
brighteners are fluorescent substances which absorb UV radiation and
immediately re-emit it in the visible part of the spectrum with the
maximun of re-emission in violet and blue parts of the spectrum. White
covers with optical brightners reflect partly the falling sun light
which is mixed with the light of fluorescence, so the human’s eye
perceives these covers as “more bright” and “more white” (well known as
“snow white”) than white covers without optical brighteners.
In the pure form, fluorescent white
finishes are used, for example, by Lakeland Inc. to cover its metal
spoons and spinners (see http://www.lakelandinc.com/finishes.html).
In general, white and fluorescent white
colors are most visible in the freshwater and saltwater environments
(Kenney et al., 1967, 1968). But the great visibility of white and fluorescent white colors does not guarantee their attractiveness for fish.
For example, Dooley (1989) has studied using trolling technique the responses of rainbow trout, Salmo gairdneri,
to wobblers, spoons and spinners of various colors and found that lures
of the solid white color were less effective than lures of blue, green,
yellow and red colors. Moraga et al. (2015) have studied using
sink-and-retrieving technique the responses of largemouth bass, Micropterus salmoides,
to soft plastic worms (of 12.7 cm length) of various colors and found
that worms of the “pearl white” color were less effective than worms of
natural and dark colors.
The same results were obtained in
marine fishing. For example, according to Hsieh et al. (2001), in
mackerel longline fishing white lures were slightly more effective than
blue, purple and transparent lures (cryptic on the background of marine
column) but less effective than black and red lures.
Psychological perception of white objects
It is known that relatively large
objects of white color may scare fish. So, Moraga et al. (2015) have
found that white soft plastic worms of 12.7 cm length allow to catch
largemouth bass of greater sizes than the same worms of darker colors.
It means that white lures warn of danger or scare largemouth bass of
smaller sizes.
In general, white objects are perceived greater in size than the same dark objects (e.g., Kremkow et al., 2014).
On the other hand, because the natural
sun light contains all the chromatic colors, which may be detected with
the assistance of Newton’s lens, we perceive the sun light as “white”.
In the same manner, we perceive any white surfaces (like white clouds,
snow, paper, etc.) as “white” because these surfaces reflect more or
less evently all components of the sun light.
However, our perceptions can not be automatically transferred to fish perceptions!
It is known that fresh water absorbs
short-wavelength rays and transmits long-wavelength rays, so the maximum
of spectral sensitivity of eyes of freshwater fish is shifted to the
orange and red parts of the optical spectrum (e.g., Tamura & Niwa,
1967). Therefore, the “white light” for freshwater fish is enriched with
the long-wavelength rays (we name this light as “worm light” or “warm
white”). In contrast, marine water absorbs long-wavelength rays and
transmits short-wavelength rays, so the maximum of spectral sensitivity
of eyes of saltwater fish is shifted to the blue and green parts of the
optical spectrum (Tamura & Niwa, 1967). Therefore, the “white light”
for saltwater fish is enriched with the short-wavelength rays (we name
this light as “cool light” or “cool white”).
How fish perceive colors, see Vorobyev et al. (2001).
In addition, for small-sized and
juvenile freshwater and salwater fish the “white light” is enriched with
UV rays (see above), which are invisible for the human’s eye.
Numerous freshwater and saltwater fish
have white or whitish with the different tints belly (or the lower side
in flat fish) that masks them on the backgrounds of the bright water
surface illuminated with the sun light. Subjected to the conditions of
crypsis in the water environment, boldly white fish (like arctic animals
in winter) are absent in this environment, excepting white morphs.
In order to estimate roughly the
composition of the underwater light, you must check first of all the
ventral coloration in fish, that is the coloration of their bellies. For
example, in such fish as carp, Cyprinis carpio, tench, Tinca tinca,
and other ecologically close fish, which live in the strongly
eutrophicated and colored fresh waters, the ventral coloration is
characterized by yellowish, olivish, orangish, brownish or even reddish
tints (e.g., see colored images of freshwater peacock bass, Cichla temensis:
Reiss et al., 2012). Namely these colors and tints define at the first
approach the composition of the underwater light under the foregoing
optical conditions.
Because for freshwater fish red color
is most lighter than all others, red colors and tints occur widely in
coloration of their lower fins (this phenomenon is called colored countershading).
Whitish ventral coloration is observed
only in pelagic and, partly, in demersal freshwater fish. Snow white
ventral coloration occurs only in pelagic saltwater fish.
In conclusion, Rapala and Lakeland
companies do not give the reflectance spectra of their finishes. There
not any statistic data confirmed the effectiveness of lures with these
finishes to catch more fish.
Basic references
Bowmaker J.K. 1990. Visual pigments of fishes. In: The visual system of fishes. Edited by Douglas R.H. & Djamgoz M.B.A. Chapman & Hall, London, 81–107
Bowmaker J.K., Kunz Y.W. 1987. Ultraviolet receptors, tetrachromatic colour vision and retinal mosaics in the brown trout (Salmo trutta): Age-dependent changes. Vision research 27, 2101-2108
Dooley R.H.A. 1989. The response of rainbow trout (Salmo gairdneri) to lures with special reference to color preference. Master’s Thesis. University of British Columbia, Canada, 1-76
Fritsches K.A, Partridge J.C., Pettigrew J.D., Marshall N.J. 2000. Colour vision in billfish. Philosophical Transactions of the Royal Society B: Biological Sciences 29, 1253-1256
Hawryshyn C.W., Arnold M.G., Chaisson D.J., Martin P.C. 1989. The ontogeny of ultraviolet photosensitivity in rainbow trout (Salmo gairdneri). Visual Neuroscience 2, 247-254
Hsieh K.Y., Huang B.Q., Wu R.L., Chen C.T. 2001. Color effects of lures on the hooking rates of mackerel longline fishing. Fisheries Science 67, 408-414
Kinney J.A.S., Luria S.M., Weitzman
D.O. 1967. Visibility of colors underwater. U.S. Naval Submarine Medical
Center. Report Number 503
Kinney J.A.S., Luria S.M., Weitzman
D.O. 1968. The underwater visibility of colors with artificial
illumination. U.S. Naval Submarine Medical Center. Report Number 551
Kremkow J., Jin J., Komban S.J., Wang
Y., Lashgari R., Li X., Jansen M., Zaidi Q., Alonso J.M. 2014. Neuronal
nonlinearity explains greater visual spatial resolution for darks than
lights. Proceedings of the National Academy of Sciences 111, 3170-3175
Losey G.S., Cronin T.W. 1997. The UV visual world of fishes. Proceedings of the 5th Indo-Pacific Fish Conference: Noumea, New Caledonia, 819-826
Losey G.S., McFarland W.N., Loew E.R.,
Zanzow J.P., Nelson P.A., Marshall N.J. 2003. Visual biology of Hawaiian
coral reef fishes. I. Ocular transmission and visual pigments. Copeia 2003, 433-454
Modarressie R., Rick I.P., Bakker T.C.M. 2006. UV matters in shoaling decisions. Proceedings of the Royal Society B273, 849-854
Modarressie R., Rick I.P., Bakker T.C.M. 2013. Ultraviolet reflection enhances the risk of predation in a vertebrate. Current Zoology 59, 151-159
Moraga A.D., Wilson A.D.M., Cooke S.J.
2015. Does lure colour influence catch per unit effort, fish capture
size and hooking injury in angled largemouth bass? Fisheries Research 172, 1–6
Östlund-Nilsson S., Holmlund M. 2003. The artistic three-spined stickleback (Gasterosteus aculeatus). Behavioral Ecology and Sociobiology 53, 214-220
Palmer M.S., Hankison S.J. 2015. Use of ultraviolet cues in female mate preference in the sailfin molly, Poecilia latipinna. Acta Ethologica 18, 153–160
Reiss P., Kenneth W. Able K.W., Nunes M.S., Hrbek T. 2012. Color pattern variation in Cichla temensis (Perciformes: Cichlidae): Resolution based on morphological, molecular, and reproductive data. Neotropical Ichthyology 10, 59-70
Rick I. P., Bakker T.C.M. 2008. UV wavelengths make female three-spined sticklebacks (Gasterosteus aculeatus) more attractive for males. Behavioral Ecology and Sociobiology 62, 439-445
Rick I.P., Bloemker D., Bakker T.C.M.
2012. Spectral composition and visual foraging in the threespine
stickleback (Gasterosteidae: Gasterosteus aculeatus L.): Elucidating the role of ultraviolet wavelengths. Biological Journal of the Linnean Society105, 359-368
Rick I.P., Modarressie R., Bakker T.C.M. 2004. Male three-spined sticklebacks reflect in ultraviolet light. Behaviour 141, 1531-1541
Siebeck U.E., Marshall N.J. 2001. Ocular media transmission of coral reef fish can coral reef fish see ultraviolet light? Vision research 41, 133-149
Siebeck U.E. 2014. Communication in the ultraviolet: Unravelling the secret language of fish. In: Biocommunication of animals. Edited by Guenther Witzany, Springer, 299-320
Smith E.J., Partridge J.C., Parsons
K.N., White E.M., Cuthill I.C., Bennett A.T.D., Church S.C. 2002.
Ultraviolet vision and mate choice in the guppy (Poecilia reticulata). Behavioral Ecology 13, 11-19
Tamura T., Niwa H. 1967. Spectral sensitivity and color vision of fish as indicated by S-potential. Comparative Biochemistry and Physiology 22, 745-754
Vorobyev M., Marshall J., Osorio D., de Ibarra N.H., Menzel R. 2001. Colourful objects through animal eyes. Color Research & Application 26, S214-S217
Responses of freshwater fish to fluorescent lures at daylight
Many companies manufacture fishing
lures and baits of bright fluorescent colors and position these products
in the consumer markets as effective tools to attract and catch fish.
However, numerous scientific, technical and applied investigations and
recreational fishing practice show that these assertions are, as
minimum, exaggerated.
In general case, fluorescence is an
optical phenomenon when molecules of some substances absorb light in the
ultraviolet or visual parts of the electromagnetic spectrum and
immediately re-emit it with the longer wavelength. Because the falling
light is partly reflected by these substances and the reflected light is
mixed with the light of fluorescence, the eyes of human and animals (if
they have color vision) perceive the total colors of these substances
as “more bright”.
Spectral sensitivity
Fresh waters are optically more turbid
than sea waters, so the maximum of spectral sensitivity in freshwater
fish is shifted to the red part of the visual spectrum. In bluegill
sunfish, Lepomis macrochirus, for example, the maximum
of spectral sensitivity is shifted to 620-640 nm (orange part of the
spectrum) (Hawryshyn et al., 1988). According to Kawamura &
Kishimoto (2002), the maximum of spectral sensitivity in largemouth
bass, Micropterus salmoides, is shifted even to 673 nm (red
part of the spectrum). It means that for freshwater fish red and orange
colors are brighter than other colors, in full contradiction with the
perception of saltwater fish and human.
This red or orange shift of the maximum of spectral sensitivity is typical for other freshwater fish (Protasov, 1978).
Turbidity
Turbid waters decrease overall
intensity of ambient light, decrease via scattering an ability of
receivers to resolve silhouettes and more (for review, see Utne-Palm,
2002). In particular, turbidity affects color perception of freshwater
fish, their color patterns and communication with the assistance of
color signals.
For example, with an increase in turbidity of habitat males of red shiners, Cyprinella lutrensis, develop more intensive red fins (Dugas & Franssen, 2011). According to Kelley et al. (2012), rainbowfish, Melanotaenia australis, in the dissolved organic matter treatment show an increase in the area and brightness of their orange striped patterns.
More generally, turbidity weakens color
signals in inter-sexual selection (Seehausen et al. 1997), even
limiting species recognition in mate choice.
Fluorescent colors underwater
Overall, fluorescent colors are
brighter than ordinary colors and are more visible underwater (Kinney et
al., 1967). In turbid water (like Thames river), orange fluorescent
color is most visible for the human’s eye than other colors.
Other animals
For fruit fly, Anastrepha suspensa, traps of orange fluorescent color are more attractive than traps of ordinary orange color (Greany et al., 1978).
Dull males versus bright males
Accustomed to think that females, in
fish and other animals with the sexual dimorphism, prefer to mate with
bright males than with dull males. In turn, generally recognized that
bright males are more vulnerable to predation risks than dull males.
However, special and most detailed investigations of these questions
reveal that these “generally accepted rules” are not universal.
For example, Breden & Stoner (1987) have shown that females of guppy, Poecilia reticulata,
from high-predation populations show genetically determined, lower
preference for brightly colored males than do females from areas of low
predation. In turn, predatory pike cichlid, Crenicichla alta,
prefer to attack in sex-mixed schools of guppy dull and most profitable
females than bright and less profitable males (Pocklington & Dill,
1995).
In other words, detection of potential
prey even from the longer distance and the real attack on prey need the
different decisions making and are separated in time.
The development of transgenic zebrafish, Danio rerio,
and other fish with green, yellow, orange, red and other fluorescent
colors has opened an opportunity to study the role of fluorescence in
intraspecific and interspecific relations in fish and their predators
under the control conditions. Note that under the day light transgenic
zebrafish have slightly more intensive colors than wildtype zebrafish
(usually with the longitudinal bluish and yellowish stripes), but under
the special ultraviolet illumination (invisible for human) they become
extremely bright (for example, see photos given by Gong et al., 2003).
In our context, Cortemeglia & Beitinger (2006) have found that under the day light predatory largemouth bass, M. salmodes,
consume red fluorescent zebrafish and wildtype zebrafish approximately
in an equal proportion. According to Jha (2010), snakehead, Channa striatus,
consume under the day conditions both red fluorescent zebrafish and
wildtype zebrafish, but try to avoid red fluorescent zebrafish. However,
Hill et al. (2011) have found that largemouth bass consume under the
day conditions about two times more red fluorescent zebrafish than
wildtype zebrafish and concluded that transgenic fish are more
susceptible to predation.
In boreal countries (like Ukraine),
wildtype and transgenic zebrafish are not survive in the nature due to
the cold winters. So, in our experiments we used common perch, Perca fluviatilis, as native predators (about 5-7 cm total length) and aquarium forms of wildtype and red fluorescent zebrafish as popetial prey.
An experimental aquarium was located
near the large laboratory windows and was illuminated with the ambient
light, which varied from daylight to twilight and nightlight. Because
perch were not familiar with both forms of zebrafish, they learnt to
hunt novel prey (note, perch are diurnal and crepuscular predators).
Briefly, perch passed from the first observations for prey to
approaches, chases and the first prey captures (about mutual learning in
predators and prey, see Lescheva & Zhuykov, 1989). Under the day
and crepuscular illuminations, no preferences of perch towards wildtype
or red fluorescent zebrafish (relatively dull under these illuminations)
were observed. However, under additional ultraviolet illumination red
fluorescent zebrafish became very bright, and perch avoided them (during
3 days of observations none of bright prey were eaten).
Fig. 1. Transgenic fluorescent danios (http://shop.glofish.com/products/glofish-danio-package).
According to our abservations, pike, Esox lucius,
another diurnal and crepuscular predator, does not avoid dull red
fluorescent zebrafish but avoid bright (UV illuminated) prey.
In the wild nature, visually guided
fish may include in their diets new and brightly colored prey but only
after long-term testing of these prey and formation of search image in
respect to these prey. For example, Hope (1984) has informed that wild
trout included in their diet an invasive species of beetles with bright
coloration only through about month of acquaintance with this new prey
and their testing.
Large fluorescent objects versus small fluorescent implants
It is necessary to distinguish large
fluorescent objects and small fluorescent implants used to tag fish. It
is shown (e.g., Catalano et al., 2001; Roberts & Kilpatrick, 2004)
that small but bright fluorescent implants may attract predators and
thus decrease the recapture rate of tagged fish in the nature.
Fluorescent fishing lines
It is shown that largemouth bass may
distiguish white, yellow and green fluorescent fishing lines but only
after several trials with attached worms to these lines (Miller &
Janzow, 1979).
Fishing practice. Part 1
There are fish habitats that allow to
confirm the attractiveness of red or orange fluorescent lures at the
statistic level. These habitats are rivers with clayish banks, clay pits
or clay ponds in which water may be very turbid especially under wind
and after rains.
Using one of these localities, we
tested soft plastic lures of red fluorescent color and ordinary red
color. Lures, namely curly tails of 3 cm length, were rigged in pairs at
the distance of 10-12 cm between each other. Fish could observe both
lures simultaneuosly for free choice, so the sign test for paired
comparisons was used for statistics.
Tests were carried out in summer in
clayish locality of Goryn river (Belarus). According to visual guide,
turbidity of the water was about 90 NTU (nephelometric turbidity units)
and more under wind. Red fluorescent lures were illuminated naturally in
the air under the sun light.
During 2 days of experiments, overall 39 fish were caught using standard spinning technique. They were adult perch, P. fluviatilis, and Donets ruffe, Gymnocephalus acerina, as well as juvenile pike, E. lucius, zander, Stizostedion lucioperca, asp, Aspius aspius, and chub, Leuciscus cephalus. Of these 39 fish, 28 fish preferred red fluorescent lures over ordinary red lures (sign test, P < 0.01).
However, in more or less clear waters
red or orange fluorescent lures may seem too bright and thus they may
deter or scare predatory fish.
It is known that mature males of three-spined sticklebacks, Gasterosteus aculeatus,
with the red breast aggresively attack other mature males and
artificial wooden red models (Darkov, 1980). According to our
observations in the nature, nest guarding males of sticklebacks attack
in the same manner approaching soft plastic shads (3 cm length) of
ordinary red color but avoid much more conspicuous red fluorescent shads
(additionally to sun light illuminated by LED lantern).
Fishing practice. Part 2
Other fish habitats suitable to use red
or orange fluorescent lures are river back waters, lakes and ponds in
which water is saturated with the soluble organic substances and
suspensions (like algae). In these habitats, for example, some natural
white maggots with one red fluorescent maggot can be more attractive for
carp, Cyprinus carpio, tench, Tinca tinca, and other
cyprinids than the same natural white maggots without one very visible
red fluorescent maggot. However, preferences of cyprinid fish to red or
orange fluorescent lures are not widespread, stable and suitable for
statistic confirmations because colors of baits are not prefered stimuli
for these fish.
Foraging carps and other large
bentivorous fish increase turbidity of water bodies (e.g., Richardson et
al., 1995; Roberts et al., 1995; Drenner et al., 1997; Sidorkewicj et
al., 1998) thus making these habitats suitable to use red or orange
fluorescent lures.
According to Sidorkewicj et al. (1998), tubidity induced by carps may achieve 100-140 NTU.
Note also, turbidity induced by carps decreases angler catch rates of other sport fish (Drenner et al., 1997).
Basic references
Breden F., Stoner G. 1987. Male predation risk determines female preference in the Trinidad guppy. Nature 329, 831-833
Catalano M.J., Chipps S.R., Bouchard
M.A., Wahl D.Y. 2001. Evaluation of injectable fluorescent tags for
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Animal responses to holographic patterns
In ethological literature, little is
known about responses of fish and other animals to holographic foils
which may be used in decoration of nests, sexual and schoolmate dummies,
artificial fishing lures and other objects.
To our knowledge, Östlund-Nilsson &
Holmlund (2003) offered colored metal foil sticks (15 mm length) to
males of three-spined stickleback, Gasterosteus aculeatus, to
decorate their nests and found that males preferred sticks of red color.
Even earlier, Darkov (1980) studied schooling behaviour of sunbleak, Leucaspius delineatus, and found that fish preferred to school with the silvery models than with the black models.
However, in both these works the influence of holographic patterns on the behavioural responses of fish has not been studied.
Experimental procedure
Our experiments were carried out in an
aquarium of 30 x 30 x 60 cm sizes under the daylight illumination. The
aquarium bottom was covered with the pebbles of medium size (10-15 mm).
At the distance of 3 cm from the side wall the lifting transparent glass
was located. This glass was used to stick holographic models (see
below). At the distance of 10 cm from this glass the frosted lifting
glass was located. When animals moved near this glass, this glass was
lifted and animals could see models.
This tank was used as aquarium to study fish and as terrarium to study lizards.
The experimental fish were wild perch, Perca fluviatilis (5-7 cm total length), wild roach, Rutilus rutilus (5-7 cm total length), and wild sunbleak, L. delineatus (about 4 cm total length). Fish were fed live bloodworms. The experimental lizards were sand lizards, Lacerta agilis (6-8 cm total length), which were fed live room flies and small grasshoppers (without one wing or one hind leg).
When animals discovered models, they
usually moved towards these models. Three types of responses were
fixated: 1) the first movement to the left or right model, 2) staying
near the left or right model during 30 min, and 3) the first attempt to
bite the left or right model. As animals observed both models at the
same time for free choice, the method of paired comparisons (sign test)
was used for statistics.
To make models, holographic foils produced by WTP Inc., USA (http://www.wtp-inc.com/color-card) were used.
Small holograpic fieldsFish
The sizes of models were 20 x 5 mm. Two
models were placed horizontally at the distance of 10 cm from each
other, at the height of 5 cm from the bottom and at the distance about
12-14 cm from the fish.
In the experiments of this type with
perch and roach, the left model made of red plain foil, WTP 45, and the
right model made of red holographic foil with large horizontal streaks,
WTP 825, were compared. In all experiments with permutation models from
left to right and vice versa, perch and roach preferred to approach,
stay and bite without hesitations the holographic model over the plain
model (sign test, P < 0,01).
However, fish were no able to
discriminate models with the similar holographic patterns like red prism
glitter, WTP 355, and red mini scale, WTP 185.
In general, fish can be trained to
discriminate visual abstract patterns (for review, see Northmore et al.,
1978), illusory patterns (Wyzisk & Neumeyer; 2007; Sovrano &
Bisazza, 2009; Agrillo et al., 2013), mirror patterns (Gierszewski et
al., 2013) and naturalistic forms (Schluessel et al., 2012). However, in
our experiments wild perch and roach were untrained for the aims of
visual discriminations and generalized similar holograpic patterns.
Lizards
Because lizards are more sensitive to
the light of shorter wavelengths, models of blue color were used. Models
made of blue plain foil, WTP 43, and blue holographic foil with large
horizontal streaks, WTP 823, were compared. In all cases, lizards
preferred the holographic model over the plain model (sign test, P <
0,01).
However, lizards were no able to
discriminate models with the similar holographic patterns like blue
prism glitter, WTP 353, and blue mini scale, WTP 183.
Basic wooden decoys
In this part of the experiments, we
considered how predatory fish responded in the field to the plain foils
and holographic foils with the different patterns.
Basic wooden decoys are lathed
practically of any timber, including an imported balsa, and have not any
concavities. Commonly, lures have an usable cylindric shape (with the
flat or roundish ends), an elongated oval shape, an elongated
barrel-like shape (with the flat ends) and an elongated drop-like shape
(with the most diameter in the tail, near to the hook). Decoys do not
equipped with self-righting ventral hooks, so their rostrums have not
skews for sinking or lifting.
To use 2D & 3D artificial eyes, recesses with the flat bottom are milled in the decoy bodies.
Each decoy has the central longitudinal
hole and is strung directly on the fishing line, resting on the treble
hook. To fish pike, Esox lucius, with sharp teeth, steel
leaders are used. The treble hook is decorated with the woolen or
synthetic material, commonly of white or light grey colors.
In our experiments, waterproof
cylindric wooden decoys of 5.0 cm length and 1.0 cm diameter were used.
Their bodies were enveloped with silvery plain foils and sivery
holographic foils described below. In addition, 2D eyes 7/32” with the
red iris, WTP 405, were sticked bilaterally in the head part of all
decoys.
Compared decoys were tested in pairs
using standard trolling technique on the two sides of the boat at the
same time. Trolling was carried out in daytime at the depth 2.5-3.0 m.
The distance between moving decoys was about 2 m. Visibility in the
water was 0.6-0.8 m for Secchi disk. Thus fish could not see both
compared lures simultaneously and therefore independent samples were
used for statistics.
The most abundant predatory fish like perch, P. fluviatilis, pikes, E. lucius, zanders, Stizostedion lucioperca, and asps, Aspius aspius, were catched and considered in the general pool.
In an aquarium when two flat foil
stripes (20 x 5 mm) are static, perch have enough time to study both
models and prefer (sign test, P < 0,01) the silvery holographic foil
with prism glitter, WTP 351, over the silvery plain foil, WTP 41.
In the field, however, perch and other
predatory fish are forced to attack potential prey very quickly (during
split second) and thus they have not enough time to study their visual
features. So approximately the same number of perch, pike, zander and
asp (Table 1) were caught on decoys enveloped with the plain and
holographic foils or with the different holographic foils.
In general (see Curio, 1976), the
process of prey-recognition (seconds, minutes, hours) and the process of
prey-attack (split second) are the different processes that are
separated in time.
Dodgers and flashers
Oscillating dodgers and rotating
flashers are special trolling devices. They have large sizes (up to 30
cm) and are frequently equiped with the holographic foils (Fig 1).
 Fig. 1. Trolling flashers with the holographic foils.
Trolling gears with dodgers allow to
catch predatory fish of larger sizes than gears without dodgers (Dooley,
1989). It means that strongly vibrating and shining dodgers and flahers
repel relatively small predatory fish.
Nothing is known about the effect of holographic patterns.
Medium holographic fields
In the experiments of this type,
rectangular models, 4 x 1 cm, and sunbleak (about 4 cm length) had
approximately equal sizes to study schooling responses of fish. Three
randomly placed horizontal models made of silvery plain foil, WTP 41,
and three randomly placed horizontal models made of silvery holographic
foils with prism glitter, WTP 351, were compared. In all cases, highly
schooling sunbleak (1, 2 and 3 individuals) preferred to approach and to
stay near the holographic models over the plain models (sign test, P
< 0,01).
However, sunbleak were no able to
discriminate models with the similar holographic patterns like silvery
prism glitter, WTP 351, and silvery mini scale, WTP 181.
Large holographic fields
In these cases, the sizes of
holographic objects are much more than the sizes of the experimental
animals. The rectangular photos (20 x 10 cm) of underwater plants and
rectangular photos of grass at the level of sand on the one hand, and
the holographic panels (20 x 10 cm) of the various types on the second
hand were used to study the responses of fish and lizards, respectively.
Fish and lizards were introduced
individually in aquarium or terrarium in the center between photos and
holographic panels and released. In all cases, fish and lizards moved
immediately or after short confusion towards the natural backgrounds
avoiding thus the large holographic panels (sign test, P < 0,01).
All holographic patterns scare. In other words, fish and lizards are not able to distinguish scared holographic patterns.
These results are not new. It is known,
for example, that holographic foils are repellents for birds and
produced on an industrial scale (see https://www.shopwtp-inc.com/index.php?cPath=34).
Basic references
Agrillo C., Petrazzini M.E.M., Dadda M. 2013. Illusory patterns are fishy for fish, too. Frontiers in Neural Circuits 7, doi: 10.3389/fncir.2013.00137
Curio E. 1976. Ethology of predation. Zoophysiology and Ecology 7. Berlin, Springer
Darkov A.A. 1980. Ecological features of visual signalling in fishes. Moscow, Science Publishing
Dooley R.H.A. 1989. The response of rainbow trout (Salmo gairdneri) to lures with special reference to color preference. Master’s Thesis. University of British Columbia, Canada, 1-76
Gierszewski S., Bleckmann H., Schluessel V. 2013. Cognitive abilities in malawi cichlids (Pseudotropheus sp.): matching-to-sample and image/mirror-image discriminations. PLoS ONE 8: e57363. doi:10.1371/journal.pone.0057363
Northmore D., Volkmann F.C., Yager D. 1978. Vision in fishes: color and pattern. The Behavior of Fish and Other Aquatic Animals. Edited by D.I. Mostofsky. Academic Press, New York
Östlund-Nilsson S., Holmlund M. 2003. The artistic three-spined stickleback (Gasterosteus aculeatus). Behavioral Ecology and Sociobiology 53, 214-220
Schluessel V., Fricke G., Bleckmann H. 2012. Visual discrimination and object categorization in the cichlid Pseudotropheus sp. Animal Cognition 15:525-537
Siebeck U.E., Litherland L., Wallis G.M. 2009. Shape learning and discrimination in reef fish. Journal of Experimental Biology 212, 2113-2119
Sovrano V.A., Bisazza A. 2009. Perception of subjective contours in fish. Perception 38, 579-590
Wyzisk K., Neumeyer C. 2007. Perception of illusory surfaces and contours in goldfish. Visual neuroscience 24, 291-298
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