TOUCH
Although fishes apparently lack the specialised touch receptors of birds and mammals, they are able to register
touch sensations by means of a net of free nerve endings in
the skin. The barbels of catfishes (Families Nos. 59 & 60)
and goatfishes (Family No. 196) are equipped with taste
buds as well as numerous free nerve endings. These barbels probably function as taste and touch receptors when
the fish is foraging for prey. The enlarged free pectoral rays
of gurnards (Family No. 157), fingerfins (Family No. 215)
and hawkfishes (Family No. 214) are likely to serve the
same functions.
SMELL
The sense of smell is well developed in most fishes. The
olfactory organs are round to oval plates of folded sensory
epithelium located in nasal capsules on either side of the
snout. Sharks (and most other elasmobranchs) have a keen
sense of smell, as indicated by their well-developed olfactory organs and the large area of their brain that is concerned with olfaction. It is well known that sharks will approach a bait from downstream, following the odour trail to
its source. Pacific salmon rely on the unique odours of their
spawning stream to return home after months or years at
sea; if their nostrils are plugged, they are unable to find
their home stream.
TASTE
The taste receptors of fishes are not restricted to the
mouth; they are also found on the lips, barbels and certain
modified fin rays, and even scattered over the head and
body. (See above paragraph on the sense of touch.) Sharks
are greatly repelled by the taste of the Moses sole, Pardachirus marmoratus (No. 262.9), which secretes a milky
toxin from pores at the base of its dorsal and anal fin rays.
The soapfishes (Family No. 167, Grammistidae) also secrete a toxin from glands in their skin. The name "soapfishes" alludes to the thick slimy mucus that covers the skin
in these fishes. If a predator tries to eat a soapfish, the bitter-tasting mucus will cause the predator to spit out the
soapfish, which is usually not seriously injured. Predators
soon learn to recognise and avoid soapfishes.
ELECTRICAL DETECTION
Sharks, rays and some bony fishes (e.g. marine catfishes
of the genus Plotosus) have electroreceptors sensitive to the
minute electric fields generated by all living animals. These
receptors, called "ampullary organs" (or, in the case of elasmobranchs, "ampullae of Lorenzini" after the man who
first described them), are located mainly on the front of the
head in sharks. Each ampulla is a slender, flask-shaped
BIOLOGY OF FISHES
organ with a long canal leading to a pore at the surface of the
skin. The ampullary organs can detect the minute electric
fields caused by breathing prey buried in the substrate, and
experiments have confirmed that benthic sharks and rays
use this electrosensory ability to find their food. It has also
been hypothesised that fishes might use their e1ectroreceptors to detect the electric fields produced as the fish swims
through the magnetic field of the earth, and this sensory
input could thus be of use in navigation.
PAIN
Do fishes feel pain? J. L. B. Smith discussed this question
some twenty years ago, and we cannot improve on his cogent essay: "There is widespread interest in the matter of
pain in fishes, which stems largely from a queer antagonism
directed against anglers. Many non-anglers would like to
stop all angling because they say it is cruel. They write sentimentally about a poor frightened fish fighting in pain and
terror for its life, with a cruel hook causing intense pain in
the sensitive tissues of the mouth. Facts do not support that.
When a hooked fish breaks loose during its struggles on a
line, one would expect it immediately to get as far away as
possible from the scene of its supposed agony. Again and
again however, proof to the contrary is forthcoming, for the
supposedly terrified fish, instead of getting away, quite
often soon after takes another bait in the same place, and
the astonished angler finds his first hook stuck fast in its
mouth. There is no doubt ofthis; it has been recorded times
without number. Almost every angler has his own special
way of mounting his hooks and can recognise his trace and
hook immediately. It sometimes happens, to the discomfiture of an angler, who, having had his fish break loose, describes to his companions the monster he has lost. Quite
often another angler nearby soon catches a quite ordinary
fish and presents it to the fellow who had just lost it with unquestionably his own hook and trace in its mouth!
"It is also plain that fishes do not necessarily learn to fear
baited hooks attached to a line, for fishes which have one or
more hooks in their mouths are often caught. I once caught
a large kabeljou (kob) with six hooks of different sizes in its
mouth; most were rusted, one was quite new.
"Sharks are notoriously indifferent to wounds, presumably feeling little or no pain. When a dead whale floating at
the surface was being cut up, sharks often came to feed and
the men working on the carcass often hit the sharks with
their sharp spades, inflicting terrible gashes. Despite their
wounds, the sharks did not seem to be in any pain or distress
for they went right on tearing at the whale as if nothing had
happened. An extreme case shows this even more forcibly,
and horribly: some sailors on a ship at anchor caught a big
shark, cut it open, tore out the insides and threw the animal
overboard. They then baited the hook with the insides of
the shark, threw it out again, and the very shark from which
9
Although fishes apparently lack the specialised touch receptors of birds and mammals, they are able to register
touch sensations by means of a net of free nerve endings in
the skin. The barbels of catfishes (Families Nos. 59 & 60)
and goatfishes (Family No. 196) are equipped with taste
buds as well as numerous free nerve endings. These barbels probably function as taste and touch receptors when
the fish is foraging for prey. The enlarged free pectoral rays
of gurnards (Family No. 157), fingerfins (Family No. 215)
and hawkfishes (Family No. 214) are likely to serve the
same functions.
SMELL
The sense of smell is well developed in most fishes. The
olfactory organs are round to oval plates of folded sensory
epithelium located in nasal capsules on either side of the
snout. Sharks (and most other elasmobranchs) have a keen
sense of smell, as indicated by their well-developed olfactory organs and the large area of their brain that is concerned with olfaction. It is well known that sharks will approach a bait from downstream, following the odour trail to
its source. Pacific salmon rely on the unique odours of their
spawning stream to return home after months or years at
sea; if their nostrils are plugged, they are unable to find
their home stream.
TASTE
The taste receptors of fishes are not restricted to the
mouth; they are also found on the lips, barbels and certain
modified fin rays, and even scattered over the head and
body. (See above paragraph on the sense of touch.) Sharks
are greatly repelled by the taste of the Moses sole, Pardachirus marmoratus (No. 262.9), which secretes a milky
toxin from pores at the base of its dorsal and anal fin rays.
The soapfishes (Family No. 167, Grammistidae) also secrete a toxin from glands in their skin. The name "soapfishes" alludes to the thick slimy mucus that covers the skin
in these fishes. If a predator tries to eat a soapfish, the bitter-tasting mucus will cause the predator to spit out the
soapfish, which is usually not seriously injured. Predators
soon learn to recognise and avoid soapfishes.
ELECTRICAL DETECTION
Sharks, rays and some bony fishes (e.g. marine catfishes
of the genus Plotosus) have electroreceptors sensitive to the
minute electric fields generated by all living animals. These
receptors, called "ampullary organs" (or, in the case of elasmobranchs, "ampullae of Lorenzini" after the man who
first described them), are located mainly on the front of the
head in sharks. Each ampulla is a slender, flask-shaped
BIOLOGY OF FISHES
organ with a long canal leading to a pore at the surface of the
skin. The ampullary organs can detect the minute electric
fields caused by breathing prey buried in the substrate, and
experiments have confirmed that benthic sharks and rays
use this electrosensory ability to find their food. It has also
been hypothesised that fishes might use their e1ectroreceptors to detect the electric fields produced as the fish swims
through the magnetic field of the earth, and this sensory
input could thus be of use in navigation.
PAIN
Do fishes feel pain? J. L. B. Smith discussed this question
some twenty years ago, and we cannot improve on his cogent essay: "There is widespread interest in the matter of
pain in fishes, which stems largely from a queer antagonism
directed against anglers. Many non-anglers would like to
stop all angling because they say it is cruel. They write sentimentally about a poor frightened fish fighting in pain and
terror for its life, with a cruel hook causing intense pain in
the sensitive tissues of the mouth. Facts do not support that.
When a hooked fish breaks loose during its struggles on a
line, one would expect it immediately to get as far away as
possible from the scene of its supposed agony. Again and
again however, proof to the contrary is forthcoming, for the
supposedly terrified fish, instead of getting away, quite
often soon after takes another bait in the same place, and
the astonished angler finds his first hook stuck fast in its
mouth. There is no doubt ofthis; it has been recorded times
without number. Almost every angler has his own special
way of mounting his hooks and can recognise his trace and
hook immediately. It sometimes happens, to the discomfiture of an angler, who, having had his fish break loose, describes to his companions the monster he has lost. Quite
often another angler nearby soon catches a quite ordinary
fish and presents it to the fellow who had just lost it with unquestionably his own hook and trace in its mouth!
"It is also plain that fishes do not necessarily learn to fear
baited hooks attached to a line, for fishes which have one or
more hooks in their mouths are often caught. I once caught
a large kabeljou (kob) with six hooks of different sizes in its
mouth; most were rusted, one was quite new.
"Sharks are notoriously indifferent to wounds, presumably feeling little or no pain. When a dead whale floating at
the surface was being cut up, sharks often came to feed and
the men working on the carcass often hit the sharks with
their sharp spades, inflicting terrible gashes. Despite their
wounds, the sharks did not seem to be in any pain or distress
for they went right on tearing at the whale as if nothing had
happened. An extreme case shows this even more forcibly,
and horribly: some sailors on a ship at anchor caught a big
shark, cut it open, tore out the insides and threw the animal
overboard. They then baited the hook with the insides of
the shark, threw it out again, and the very shark from which
9