Fish: Sensitivity Beyond the Captor’s Grasp

By Joan Dunayer

Reprinted with the author's permission, September 2015

Originally published in The Animals' Agenda, July/Aug. 1991, pp. 12-13, 15-18
Copyright 1991 Joan Dunayer

As more people become aware of the sensitivity of fish, fish will begin to receive the compassion and respect they deserve.

Blackie, a severely deformed Moor goldfish, could barely swim. Big Red, a larger Oranda goldfish, sensed Blackie’s helplessness. As soon as Blackie was added to Big Red’s pet-store tank, Big Red started looking after him. “Big Red constantly watches over his sick buddy, gently picking him up on his broad back and swimming him around the tank,” a South African newspaper reported in 1985. Whenever food was sprinkled overhead, Big Red carried Blackie to the water’s surface so that both could eat. For a year, the pet-store owner said, Big Red had been showing this “compassion.”

Most humans show far less compassion for fish. Tragically and ironically, they fail to recognize sensitivity that in many ways surpasses their own.

The Perceptual World of Fish

The inner ears of fish capture an underwater world perceptible to humans only through hydrophones. Although they lack vocal cords, fish “talk.” By squeezing their swimbladder, gnashing their pharyngeal teeth, or rubbing some of their bones together, they produce sounds ranging from buzzes and clicks to yelps and sobs. Fish “vocalizations,” marine biologists have found, communicate such attitudes as courtship, alarm, or submission, along with the “speaker’s” species, size, and individual identity. The male satinfin shiner, for example, purrs when courting but “thumps” when defending his territory.

The lateral line, a series of sensory hairs running from head to tail on each side of a fish’s body, also registers vibrations. As a fish swims, the lateral line pinpoints nearby objects from the vibrations they bounce back, enabling fish to navigate and locate prey in darkness.

The sensitivity of fish to light exceeds ours. Many abyssal fishes can see in dimmer light than a cat. Shallow-water species have dual vision. As dawn approaches, the eye’s color-sensitive cones extend forward while the rods, sensitive to dim light, recede deep into the retina; at twilight, the process reverses. During the transition, an ability to perceive ultraviolet light assists many fishes; this light suffices to silhouette insects at the water’s surface. When a fish is night-adapted, sudden brightness (say, from a flashlight) startles and disorients the fish, who may flee, freeze, or sink. The light may also destroy rod cells.

In most fish, taste buds dot the lips and snout, as well as the mouth and throat. Many bottom-feeders also have taste sensors on pelvic-fin extensions or whisker-like chin barbels that act as external tongues. Covered with hundreds of thousands of taste sensors, catfish can taste food at some distance.

How sensitive are fish to odors? Salmon can migrate thousands of miles and, years later, recognize the smell of their home stream. American eels can detect alcohol at solution strengths comparable to one-billionth of a drop in 23,000 gallons of water (the size of a large swimming pool). By odor alone, some fish can determine another fish’s species, gender, sexual receptivity, or individual identity.

Fish react strongly to tactile contact. In courtship, they often gently rub against each other. Narragansett Marine Laboratory recordings have revealed that the sea robin purrs when petted. Underwater photographer Ricardo Mandojana gained the friendship of an initially wary jewfish by lightly scratching the fish’s forehead. For months after, the fish, apparently eager to be petted, approached the diver on his rounds.

With hundreds of electric sensors on their skin, fish of many species detect the shape of electric fields they generate. An object less conductive than water, such as a rock, casts an electrical shadow on the field; an object more conductive, such as prey, creates a bright spot. The fish’s electrical picture includes objects’ location, size, speed, and direction of movement. Electric fish also “read” one another’s discharges, which vary according to the signaler’s age, species, individual identity, and intentions (for example, courtship or challenge). A male banded knifefish asserts dominance with a rapid succession of pulses; his potential rival yields by falling “silent.”

Whether or not they electrically signal, many fishes sense the electricity generated by all living beings and, in this way, detect prey hiding in gravel or sand. Some sharks, neuroscientist Theodore Bullock has noted, can perceive an electrical charge of amount and distance analogous to a flashlight battery’s 1.5 volts over 900 miles away.

The Capacity of Fish to Suffer

In keeping with their other sensitivities, fish undoubtedly feel stress and pain. Chased, confined, or otherwise threatened, they react as humans do to stress: with increased heart rate, breathing rate, and adrenal hormone release. Subjected to prolonged adverse conditions such as crowding or pollution, they suffer immune deficiency and damage to internal organs. Both biochemically and structurally, the central nervous systems of fish closely resembles ours. In vertebrates, free nerve-endings register pain; fish possess these nerve-endings in abundance. Fish also produce enkephalins and endorphins, opiate-like substances known to counter pain in humans. When injured, fish writhe, gasp, and show other signs of pain.

Fish definitely feel fear, which plays a role in learned avoidance. Once minnows have been attacked by a pike, or merely seen other minnows attacked, they flee at the smell of pike odor. Having experienced a jack’s attack, fish flee at the sound of a jack’s teeth-grinding. Largemouth bass, researcher R. O. Anderson demonstrated, rapidly learn to avoid hooks simply by seeing other bass get hooked. In hundreds, perhaps thousands, of experiments, fish have performed tasks in order to avoid electric shock.

Numerous experimenters have acknowledged inducing fear in fish. Among his “observations on fear-motivated behavior of goldfish,” psychiatrist Quentin Regestein has noted, “A scared fish may dart forward, back up, or flip about, or he may simply go limp when the situation becomes too overwhelming.”

Fish cry out in both pain and fear. According to marine biologist Michael Fine, most sound-producing fishes “vocalize” when prodded, held, or chased. In experiments by William Tavolga, toadfish grunted when electrically shocked. What’s more, they soon came to grunt at the mere sight of an electrode.

Fish as “Pets”

With or without the added cruelty of experimentation, holding fish captive disregards their most basic needs. High-strung and fragile, fish are ill-suited to a glass-enclosed life; yet, in the U.S. alone, hundreds of millions are imprisoned in home aquariums.

Fish are more sensitive to temperature than any warm-blooded animal: A sudden change of only a few degrees can kill a goldfish. Nevertheless, fish are confined to small containers whose water temperature can rapidly fluctuate.

Aquarium fish cannot escape harmful chemicals that enter their water. Cigarette smoke, paint fumes, and aerosol sprays are only a few of the common indoor pollutants that can harm fish. In a bowl or tank, the ammonia that fish themselves excrete can accumulate to toxic levels. As with ammonia, minute amounts of chlorine can cause breathing difficulty and nervous spasms. The chlorine in tap water can easily prove fatal.

Human sights and sounds bombard aquarium fish. Simply switching on the light in a dark room can so startle them that they dash into their tank’s walls, and die. Vibrations from a TV, stereo, or slammed door can also cause alarm and injury. In You and Your Aquarium, Dick Mills warns that fish are “likely to be shocked and stressed by any knocking on the front glass.” Fish repeatedly exposed to loud music, researcher H. H. Reichenbach-Klinke found, develop fatal liver injury.

While assailing fish with the artificial, aquariums rob them of the natural. The fish are denied such activities as foraging over brilliantly varied coral reef. Instead they swim and re-swim the same cubic inches or feet, passively receiving the same commercial feed day after day. Aquarium fish, Mills states, often suffer from boredom.

Goldfish and other social fish require companions of their own species; otherwise, Mills comments, they “might well pine away.” At the loss of a companion, fish show signs of depression, such as lethargy, paleness, and drooping fins. In Animal Intelligence, zoologist George Romanes shares this incident: When an aquarium owner gave one of two ruffs away, the remaining ruff stopped eating until, three weeks later, the companion was returned.

Hobbyists’ harm to fish extends far beyond the home aquarium. Countless fish die before reaching the pet store, during transport from either the fish “farm” (where 80 percent of U.S. “ornamental” fish are now bred) or the wild. Capture alone injures and kills millions of fish, who are incapacitated with anesthetics, dynamite, or cyanide before being caught by hand or net. Fisheries biologist William McLarney has observed capture with cyanide spray:

A dozen bright red squirrelfish abruptly flee from their coral reef home, gasping and jerking. They make a mad dash for the surface, 25 feet above the reef, and keep going a foot into the air. Then they fall back with little sodden plops and float, exhausted, feebly circling. Below them, a three-pound grouper coughs violently, its gills suddenly on fire. It tries to swim but keels over as it goes, until it floats quietly like a grisly marker buoy.

Meanwhile, fish too “drab” to interest buyers “lie convulsing or still on the bottom.”

Commercial Fishing

Commercial fishing further decimates fish, killing untold billions each year. Generally, their deaths are neither quick nor painless.

In purse seining, a boat encircles a school of fish with a net that is then drawn tight. Once hauled up, the fish are usually dumped into liquid brine kept below freezing. If they haven’t already suffocated or been crushed, the fish die of thermal shock. Purse seining for yellowfin tuna has aroused public outrage on behalf of dolphins ensnared with the tuna swimming below them. Few people, however, have protested the death meted out to the tuna themselves. Surely, the motorboats and underwater explosives that herd the dolphins cause terror and pain to the vibration-sensitive tuna as well. Pressure waves from an underwater detonation can burst a fish’s swimbladder.

In trawling, a moving boat drags an enormous net through the water. The tow forces all fish who enter the net into the tapered, closed end. For one to four hours, the netted fish are squeezed and bounced, together with any rocks and ocean debris. “Prolonged tumbling and dragging in the net had caused the fish to rub against each other and file away their sharp scales,” author William Warner reported of one haul, in Distant Water: The Fate of the North Atlantic Fisherman. “Their flanks, in fact, were scraped entirely raw.”

When hauled up from a substantial depth, fish undergo excruciating decompression. As water pressure plummets, the volume of gas in a fish’s swimbladder increases more rapidly than the bloodstream can absorb the gas. Frequently, the intense internal pressure ruptures a fish’s swimbladder, pops out the eyes, and pushes the esophagus and stomach out through the mouth. “Many of the fish had gaping sockets where their eyes should have been,” Warner observed on one trawler. As the net was hauled up on another, he saw “a great froth of bubbles . . . emanating from the ruptured swimbladders of thousands of fish.”

Smaller fish, such as flounder, are ordinarily dumped onto chopped ice; most suffocate or are crushed to death by layers of fish who follow. Larger fish, such as cod and haddock, tumble onto deck. Eyewitness William MacLeish has described how the catch is sorted: the crew stab the fish with short, spiked rods called pickers, “throwing cod here, haddock there, yellowtail there.” Next, the fish have their throats and bellies slit (not necessarily in that order). Meanwhile, non-target (“trash”) fish, who sometimes comprise most of the catch, are thrown overboard, often by pitchfork.

On any one evening, fishers may set out some 40,000 miles of gillnets, mainly driftnets on the Pacific high seas, but also anchored nets in coastal waters, including U.S. waters. Plastic mesh with floats on top and weights at the bottom, gillnets hang like curtains, generally to a depth of 30 feet. In addition to slaughtering more than a million mammals, turtles, and birds each year, gillnets inflict enormous suffering on fish.

Unable to see the netting, fish swim into it. Unless they are smaller than the mesh size, they get no further than poking their heads through. When they try to back out, the netting catches them by their gill-plates or fins. Many of the fish suffocate. Others struggle so desperately in the sharp mesh that they bleed to death, whether or not they have managed to pull free. Because many fishers fail to tend their gillnets daily, trapped fish may survive for days, slowly dying. Journalist Clive Gammon saw cod pulled aboard after two days. Many were “eyeless, finless, and scaleless”; others had been eaten away by sand fleas. Trapped fish are helpless prey. (The predators they attract frequently become entangled as well.) When a gillnet is hauled, the fish are pulled out by hook.

Some commercial fishers still harpoon large, valuable fish (such as swordfish, tuna, and sharks) or hook them individually. Far more commonly, however, large fish are caught by longlining. In this method (also used to catch smaller fish), a ship unreels as much as 30 miles of line bristling with hundreds or thousands of baited hooks.

Sport Fishing

About 40 million Americans—16 percent—abuse fish for “sport.” Many sportfishers claim that their victims don’t suffer. All the evidence indicates otherwise.

Researcher John Verheijen and co-workers studied carps’ reaction to hook and line. When hooked, carp shake their head, spit as if to cough up food, dart, and dive. Electric shock in the roof of their mouth initially elicits the same reactions. When hooked and held on a taut line for at least several minutes, carp spit gas from the swimbladder; after the line is slackened, they sink. Subjected to severe and sustained electric shock, carp also spit gas and sink. Strikingly, they react the same way when they are confined in a small space, or smell the odor of a wounded member of their species; these situations inflict no direct injury but are well-known to cause fear. Hook and line, the experimenters concluded, cause some combination of terror and pain.

As a hooked fish struggles to escape, muscle glycogen (stored glucose) diminishes, while lactic acid rapidly accumulates in the bloodstream. Within a few minutes, strenuous exertion halves a rainbow trout’s glycogen store. In the May 1990 issue, Field and Stream columnist Bob Stearns acknowledged that lactic acid can “immobilize” a fish “in a much more rapid and intense fashion than the similar cramps and sore muscles we humans suffer from too much exercise.” The longer the fish struggles, the greater the lactic acid build-up. Yet, sportfishers take pleasure in “running” fish hard. In the July 1990 issue of Field and Stream, Stearns extolled a “diminutive lady angler” who drove a swordfish for nearly five hours: “Every time the fish would slow, she would seize the moment: pumping, pressuring, aggravating it into expending its own energy reserves, never allowing it to rest.” Before being hauled up, many fish die from exhaustion.

For many others, the worst suffering may follow being reeled in. Typically, medium-sized and larger fish are pulled on board by being stabbed with a hand-held hook. Sometimes, fish are skinned alive. Many fishers regularly string their still-living catch, for hours, on a rope or chain that hangs in the water. The rope is threaded through each fish, normally through the mouth and one gill-opening. The chain has clips like giant safety-pins on which the fish are impaled, usually through the jaw. Most fish caught in “sport” suffocate. Even out of water, they may die slowly. In October 1980, Field and Stream writer Ken Schultz described a bass left out of water for an hour: the fish had reddened fins and gills, and was “still gasping.”

Catch-and-release fishing, at a minimum, inflicts terror, pain, and temporary disability. Frequently, it permanently or fatally disables. Field and Stream associate editor Jim Bashline, in a May 1990 article, admitted that fish commonly “struggle so violently as the hook is being removed that anglers drop them on the hard bottom of a boat or a rocky bank.” Dropping, netting, handling, and other assaults remove a fish’s delicate, transparent surface skin. Mucous-coated, this outermost layer protects against infection, waterlogging, and dehydration of internal tissues—any of which can be fatal. As experiments have confirmed, fish may also die of lactic-acid poisoning several hours after overexertion, hours during which they may be completely paralyzed. Always, the hook causes injury. Severe mouth lacerations can destroy a fish’s ability to eat. Many fish are released after being hooked by the gills or internal organs, as when they swallow the hook into their stomach.

Fishing also tortures any live bait used. Minnows and other small fish are routinely hooked through the back, the lips, or even the eyes. Because injuries attract predatory “gamefish,” some anglers further maim baitfish by cutting their fins or breaking their backs.

“Managing” Fish for Sport

To provide a steady supply of catches, U.S. hatcheries annually stock angling waters with hundreds of millions of fish, especially salmon and trout. A self-described “former barker for the managers,” Ted Williams has called hatchery trout “genetic wrecks.” In a September 1987 Audubon article, he wrote, “After years of inbreeding, hatchery trout tend to be deformed. Gill covers don’t fit, jaws are bent, tails pinched.” Some harmful mutations are intentionally cultivated. Utah’s Division of Wildlife Resources, for example, has mass-produced light-sensitive albinos to serve as easily spotted catch.

Williams deplores the conditions in which hatchery trout are reared: “filthy, crowded, cement troughs that wear away scales and fins.” The fish, he adds, are ill-equipped for life in the wild. Whereas native trout flee at overhead movement, hatchery trout expectantly wait to be fed (convenient for anglers). Himself an avid fisher, Williams cut open one hatchery trout to find that the fish, accustomed to eating pellets, had been feeding on cigarette butts.

Sportfisher Mark Sosin and fisheries biologist John Clark have coauthored a book for anglers, Through the Fish’s Eye: An Angler’s Guide to Gamefish Behavior, in which they candidly identify the goal of fish management: “to provide the best sportfishing.” To thin native populations of smaller non-game fish and increase water transparency (a boon to fishers), managers often partially drain lakes or ponds, leaving the non-game species to suffer from reduced food, protective cover, and space in which to avoid predators. “When a lake or pond becomes heavily populated with undesirable species,” Sosin and Clark state coolly, “the best solution may be to annihilate all the fish and start over again. This is usually done either by draining the lake dry or by poisoning the fish. . . . After all of the fish have been killed, the basin is refilled and stocked according to the desired mix of predator and prey species.” Desired, that is, by anglers and the “wildlife managers” whose salaries derive largely from fishing-license fees.

Most humans feel little empathy for fish. Seeing fish gathered en masse, or viewing them as uniform throughout a species, people easily disregard them as individuals. Because fish dwell in an aquatic world, communicate by means hidden to our perceptions, and have a physical appearance so different from our own, many humans fail to recognize their sentience. The result is massive, socially sanctioned abuse. As more people become aware of the sensitivity of fish, fish will begin to receive the compassion and respect they deserve.

When it comes to feeling, we have much to learn from Big Red.

Joan Dunayer is the author of Animal Equality: Language and Liberation (2001) and Speciesism (2004).

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