Pain in fish
Pain is a complex state, with a distinct perceptual quality but also associated with suffering, which is an emotional state. Many people believe that the only fully reliable way of determining the presence of pain is by introspection.[clarification needed] Because of this complexity, the presence of pain in an animal, or another human for that matter, cannot be determined unambiguously using observational methods, but the conclusion that animals experience pain is often inferred on the basis of comparative brain physiology and physical and behavioural reactions. Some specialists currently believe that all higher vertebrates feel pain, and that certain invertebrates, like the octopus, might too. Animal protection advocates have raised concerns about the possible suffering of fish caused by angling. In light of recent research, some countries, like Germany, have banned specific types of fishing. The idea that animals might not feel pain as human beings feel it traces back to the 17th-century French philosopher, Rene Descartes, who argued that animals do not experience pain and suffering, because they lack consciousness. Bernard Rollin of Colorado State University, the principal author of two U.S. federal laws regulating pain relief for animals, writes that researchers remained unsure into the 1980s as to whether animals experience pain, and veterinarians trained in the U.S. before 1989 were simply taught to ignore animal pain. In his interactions with scientists and other veterinarians, Rollin was regularly asked to "prove" that animals are conscious, and to provide "scientifically acceptable" grounds for claiming that they feel pain. Carbone writes that the view that animals feel pain differently is now a minority one. Academic reviews of the topic are more equivocal, noting that although the argument that animals have at least simple conscious thoughts and feelings has strong support; some critics continue to question how reliably animal mental states can be determined. Veterinary medicine uses, for actual or potential animal pain, the same analgesics and anesthetics used in humans. There is a great deal of research on anaesthesia and analgesia in fish. Experiments by William Tavolga provide evidence that fish respond to potentially noxious stimuli. For instance, in TavolgaТs experiments, toadfish grunted when electrically shocked, and over time they came to grunt at the mere sight of an electrode. Additional tests conducted
at the Roslin Institute and University of Edinburgh, in which bee venom and acetic acid was injected into the lips of rainbow trout, resulted in fish rubbing their lips along the sides and floors of their tanks, which the researchers believe was an effort to relieve themselves of pain. One researcher argues about the definition of pain used in the studies. Since this initial work Dr Lynne Sneddon and her lab have characterised alleged pain responses in rainbow trout, common carp and zebrafish. However, when these experiments were replicated by Newby and Stevens (2008, 2009), without anaesthetic, rocking and rubbing behaviour was not observed, suggesting that some of the alleged "pain" responses observed by Sneddon and co-workers were likely to be due to recovery of the fish from anaesthesia.,  Goldfish In a 2009 paper, Janicke Nordgreen from the Norwegian School of Veterinary Science, Joseph Garner from Purdue University, and others, published research which concluded that goldfish do feel pain, and that their reactions to pain are much like those of humans. "There has been an effort by some to argue that a fish's response to a noxious stimulus is merely a reflexive action, but that it didn't really feel pain," Garner said. "We wanted to see if fish responded to potentially painful stimuli in a reflexive way or a more clever way." The fish were divided into two groups, one given morphine and the other saline. They were then subjected to unpleasant temperatures. The fish that were given saline subsequently acted with defensive behaviours, indicating anxiety, wariness and fear, whereas those given morphine did not. Nordgreen said that the behavioural differences they found showed that fish feel both reflexive and cognitive pain. "The experiment shows that fish do not only respond to painful stimuli with reflexes, but change their behavior also after the event," Nordgreen said. "Together with what we know from experiments carried out by other groups, this indicates that the fish consciously perceive the test situation as painful and switch to behaviors indicative of having been through an aversive experience." In 2013 Rose et al. reviewed this and other studies which concluded that pain had been found in fish. They claimed that the results from such research are due to poor design and misinterpretation, and that the researchers were unable to distinguish unconscious detection of injurious stimuli (nociception) from conscious pain.