From Animal Liberation
„Now more difficult questions arise. How far down the evolutionary scale shall we go? Shall we eat fish? What about shrimps? Oysters? To answer these questions we must bear in mind the central principle on which our concern for other beings is based. As I said in the first chapter, the only legitimate boundary to our concern for the interests of other beings is the point at which it is no longer accurate to say that the other being has interests. To have interests, in a strict, nonmetaphorical sense, a being must be capable of suffering or experiencing pleasure. If a being suffers, there can be no moral justification for disregarding that suffering, or for refusing to count it equally with the like suffering of any other being. But the converse is also true. If a being is not capable of suffering, or of enjoyment, there is nothing to take into account.
So the problem of drawing the line is the problem of deciding when we are justified in assuming that a being is incapable of suffering. In my earlier discussion of the evidence that nonhuman animals are capable of suffering, I suggested two indicators of this capacity: the behavior of the being, whether it writhes, utters cries, attempts to escape from the source of pain, and so on; and the similarity of the nervous system of the being to our own. As we proceed down the evolutionary scale we find that on both these grounds the strength of the evidence for a capacity to feel pain diminishes. With birds and mammals the evidence is overwhelming. Reptiles and fish have nervous systems that differ from those of mammals in some important respects but share the basic structure of centrally organized nerve pathways. Fish and reptiles show most of the pain behavior that mammals do. In most species there is even vocalization, although it is not audible to our ears. Fish, for instance, make vibratory sounds, and different „calls‰ have been distinguished by researchers, including sounds indicating „alarm‰ and „aggravation.‰ Fish also show signs of distress when that are taken out of the water and allowed to flap around in a net or on dry land until they die. Surely it is only because fish do not yelp or whimper in a way that we can hear that otherwise decent people can think it a pleasant way of spending an afternoon to sit by the water dangling a hook while previously caught fish die slowly besides them.
In 1976 the British Royal Society for the Prevention of Cruelty to Animals set up an independent panel of inquiry into shooting and angling. The panel was chaired by Lord Medway, a noted zoologist, and made up of experts outside the RSPCA. The inquiry examined in detail evidence on whether fish can feel pain, and concluded unequivocally that the evidence for pain in fish is as strong as the evidence for pain in other vertebrate animals. People more concerned about causing pain than about killing may ask: Assuming fish can suffer, how much do they actually suffer in the normal process of commercial fishing? It may seem that fish , unlike birds and mammals, are not made to suffer in the process of rearing them for our tables, since they are usually not reared at all: human beings interfere with them only to catch and kill them. Actually this is not always true: fish farming… But even with fish who are not farmed, the death of a commercially caught fish is much more drawn out than the death of, say, a chicken, since fish are simply hauled up in the air and left to die. Since their gills can extract oxygen from water but not from air, fish out of water cannot breathe. The fish on sale in your supermarket may have died slowly, from suffocation. If it was a deep-sea fish, dragged to the surface by the net of a trawler, it may have died painfully from decompression.
When fish are caught rather than farmed, the ecological argument against eating intensively reared animals does not apply to fish. We do not waste grain or soybeans by feeding them to fish in the ocean. Yet there is a different ecological argument that counts against the extensive commercial fishing of the oceans now practiced, and this is that we are rapidly fishing out the oceans. In recent years fish catches have declined dramatically. Several once-abundant species of fish, such as the herrings of Northern Europe, the California sardines, and the new England haddock, are not scarce as to be, for commercial purposes, extinct. Modern fishing fleets trawl the fishing grounds systematically with fine-gauge nets that catch everything in their way. The nontarget species – known in the industry as „trash‰ – may make up as much as half the catch. Their bodies are thrown overboard. Because trawling involves dragging a huge net along the previously undisturbed bottom of the ocean, it damages the fragile ecology of the seabed. Like other way of producing animal food, such fishing is also wasteful of fossil fuels, consuming more energy than it produces. The nets used by the tuna fishing industry, moreover, also catch thousands of dolphins every year, trapping them underwater and drowning them. In addition to the disruption of ocean ecology caused by all this overfishing there are bad consequences for humans too. Throughout the world, small coastal villages that live by fishing are finding their traditional source of food and income drying up. From the communities on Ireland‚s west coast to the Burmese and Malayan fishing villages the story is the same. The fishing industry of the developed nations has become on more form of redistribution from the poor to the rich.
So out of concern for both fish and human beings we should avoid eating fish. Certainly those who continue to eat fish while refusing to eat other animals have taken a major step away from speciesism; but those who eat neither have gone one step further.
When we go beyond fish to other forms of marine life commonly eaten by humans, we can no longer be quite so confident about the existence of a capacity for pain. Crustacea – lobster, crabs, prawns, shrimps – have nervous systems very different from our own. Nevertheless, Dr. John Baker, a zoologist at the University of Oxford and a fellow of the Royal Society, has stated that their sensory organs are highly developed, their nervous systems complex, their nerve cells very similar to our own, and their responses to certain stimuli immediate and vigorous. Dr. Baker therefore believes that lobster, for example, can feel pain. He is also clear that the standard method of killing lobster – dropping them into boiling water – can cause pain for as long as two minutes. He experimented with other methods sometimes said to be more humane, such as placing them in cold water and heating slowly, or leaving them in fresh water until they cease to move, but found that both of these led to more prolonged struggling and, apparently, suffering. If crustacea can suffer, there must be a great deal of suffering involved, not only in the method by which they are killed, but also in the ways in which they are transported and kept alive at markets. To keep them fresh they are frequently simply packed, alive, on top of each other. So even if there is some room for doubt about the capacity of these animals to feel pain, the fact that they may be suffering a great deal, combined with the absence of any need to eat them on out part, makes the verdict plain: they should receive the benefit of the doubt.
Oysters, clams, mussels, scallops, and the like are mollusks, and mollusks are in general very simple organisms. (There is an exception: the octopus is a mollusk, but far more developed, and presumably more sentient, than its distant mollusk relatives.) With creatures like oysters, doubts about a capacity for pain are considerable; and in the first edition of this book I suggested that somewhere between shrimp and an oyster seems as good a place to draw the line as any. Accordingly, I continued occasionally to eat oysters, scallops, and mussels for some time after I became in every other respect, a vegetarian. But while one cannot with any confidence say that these creatures do feel pain, so one can equally have little confidence in saying that they do not feel pain. Moreover, if they do feel pain, a meal of oysters or mussels would inflict pain on a considerable number of creatures. Since it is so easy to avoid eating them, I now think it better to do so.‰
-Peter Singer, Animal Liberation. 1990, (171-174)