One of the most interesting parts of Ode to a Large Tuna in the Market is its portrayal of a cross-species connection, or, to be more specific, a human's attempt to empathize with and understand a creature very different from himself. The tuna seems doubly mysterious to the speaker not merely because it is not human, but because it is a fish. The fact that it comes from the sea, in particular, makes the fish seem strange—revealingly, even stranger than the market vegetables surrounding it. To the human speaker, a fish is not merely harder to fully understand than other animals: it may be even harder to understand than some plants. The poem's speaker, while unsure what exactly to make of the tuna, certainly believes that it had consciousness when it was alive. But for many humans, both scientists and artists, the question of fish consciousness has been a difficult one, leading to a great deal of research and imaginative speculation exploring whether and in what ways fish experience pain and other human feelings and sensations.
The specific issue of fish consciousness fits within a broader scientific conversation around animal consciousness generally. Throughout scientific history, an obvious obstacle to those attempting to understand animal experience has been the impossibility of direct communication with non-humans. The science writer Carl Safina, an advocate for the view that animals do experience human-like mental lives, laments that historically "scientists [have] said, 'All we can know about animals is based on what they do. We can only describe what they do. We can’t know anything about their minds.' Unfortunately, that hardened into a straightjacket assumption that if we can’t know anything about their minds, we can’t confirm consciousness." Indeed, many generations of philosophers and scientists argued that animals' abilities to react to stimuli were far from constituting hard-and-fast evidence of inner lives. Augustine argued that animals "lack understanding, sensation, and life altogether," while Descartes suggested that animal behavior was more akin to that of a machine than that of a human.
Today, however, scientific consensus generally agrees with Safina that animals are capable of experiencing pain and consciousness generally. In 2012, a group of scientists released what is known as the Cambridge Declaration on Consciousness, which unequivocally stated that animals including but not limited to mammals and birds experience human-like consciousness. A good deal of evidence suggests that, at least to some extent, fish also have internal experiences not dissimilar to human ones. They appear to feel something resembling the human sensation of pain—and by extension, a human-like consciousness more generally. When subjected to potentially painful stimuli, such as being poked with a pin, fish's brains react physiologically much like human ones. They experience a surge in activity in nociceptors, neurons geared towards registering dangerous physical conditions. In other studies, fish injected with irritating substances such as acetic acid and vinegar have acted in ways indicating that they are experiencing discomfort: they fail to exercise caution around new objects that they would typically avoid, or they perform unusual movements such as rocking back and forth.
While some scientists and philosophers argue that animal consciousness in general is impossible to study because of the subjective or illusory nature of consciousness itself, others have specifically put forth that fish consciousness is impossible because of fish physiology—namely, the relatively small brains and underdeveloped cerebral cortexes of fish relative to humans and other mammals. Others counter that to associate consciousness entirely with a human-like brain is both a rejection of experimental evidence and a failure of imagination; the Cambridge Declaration reads "The absence of a neocortex does not appear to preclude an organism from experiencing affective states." Still others propose that, while fish and other animals may have some degree of subjectivity and sensation, their lack of language inherently limits the reach of that subjectivity by making it impossible for them to mentally organize, analyze, and categorize feeling. Indeed, the question of fish consciousness and animal consciousness more broadly is not merely relevant to questions of animal rights, but to wide-ranging questions concerning the nature of experience itself.
Pablo Neruda is far from the only writer to delve into the question of animals' affective experience, or to dwell on the resulting tensions in human/animal interactions. Some of the best-known writing on this question has come from children's literature: beloved books like Charlotte's Web are propelled by the conflicts arising out of animal subjectivity and human clumsiness decoding it. Meanwhile, the poet Elizabeth Bishop, a contemporary of Neruda's, is perhaps most famous for her poem "The Fish," which portrays a moment of connection between a human and a fish as the speaker attempts to understand the fish's inner life. Though quite different tonally, Ted Hughes's poem "Pike" also examines the points of connection and alienation between fish and human. As the twentieth century continued, with animal consciousness increasingly a topic of scientific experimentation, the era's poets chronicled the urge to sympathize with animals and the struggle to understand them.
