Search

Analgesics are an integral part of routine pain management in mammals, yet their use in fish is still limited. Some recommendations on the use of analgesics in fish are currently in the literature; however, information on the properties of analgesic drugs in most fish species is still scarce and sometimes misleading. The present review of information on the use of analgesics in fish was thus compiled to help clinicians make an informed decision as to which drug and dose to use. The main agents that have been investigated are opioids, NSAID, and local anesthetics, primarily in rainbow trout and zebrafish. There is presently no overwhelming evidence of efficacy for most analgesics in fish, although beneficial effects on behavior and physiologic parameters have been reported in many instances, especially associated with morphine administration. Furthermore, most analgesics did not result in significant adverse side effects. Thus, analgesics could be administered whenever it is considered that an animal might experience pain, given that the drugs appear not to cause harm and may be beneficial. However, caution must be advised because 1) important interspecies variation has been reported and 2) unforeseen effects could affect experimental results. Further research is needed to investigate analgesic use in fish. This should be accompanied by research aimed at improving our knowledge of the various species of fish. The current lack of a validated approach to assessing pain in fish limits our ability to evaluate the efficacy of analgesics in fish.

Local anesthetics are an integral part of routine pain management in mammals, yet their use is relatively limited in fish, amphibians and reptiles. These animals frequently undergo potentially painful surgical procedures and therefore could possibly benefit from those drugs. Some recommendations are currently available in the literature concerning analgesic use in these animals. However the pharmacological properties, safety and often efficacy of local anesthetic drugs have not been investigated yet in fish, amphibians, or reptiles. This review compiled current information concerning the use of those agents in fish, reptiles and amphibians to help clinicians make an informed decision as to which dose and drug to use. The resulting literature search showed that the literature concerning use of local analgesics in fish and amphibians is very limited while the literature for reptiles is more extensive. We found few experimental studies evaluating the efficacy of local anesthetics. Further studies would provide additional information for developing guidelines to improve the welfare of fish, amphibians and reptiles.

The relative amounts of the different forms of morphine, and many other pharmacologic agents, depend on temperature and pH. Some forms are more efficacious because they are uncharged and can penetrate lipid membranes more easily than the charged forms. Persons who administer pharmacologic agents to ectotherms (that is, cold-blooded animals) should consider the effect of temperature on the relative amounts of the different forms of drugs. For example, the fraction of morphine present in the uncharged form is twice as high in a fish or frog at 5 degrees C as in a mammal at 37 degrees C. Moreover, because the pH of blood, plasma, and tissues of ectotherms is higher when they are held at lower temperatures, the combined effect of temperature and pH on the speciation of pharmacologic agents also should be considered. In addition, the total solubility of morphine and other pharmacologic agents depends on temperature and pH. The purpose of this overview is to describe how temperature and pH influence the solubility and speciation of morphine.

Tunas are unusual among fish in that they are warm bodied. In the present essay we argue that one adaptive advantage to being warm is that the warmth increases the rate of delivery of oxygen from the cell boundary to the mitochondria by myoglobin. This argument is supported by the following. 1) Tuna have extremely high rates of oxygen uptake, much higher than other fish and close to the rates achieved by mammals. 2) Tuna have an extraordinary capacity to maintain high cruising speeds for a long time. 3) Tuna have much red muscle that contains a high concentration of myoglobin. 4) The effect of temperature on simple diffusion of oxygen is very small whereas the potential affect on facilitated diffusion by myoglobin is large.

Giant bluefin tuna warm their viscera during and after a meal. The cecum of a 500-kg bluefin weighs about 9 kg and contains about 20,000 pyloric ceca, each about 10 cm long and 1.5 mm diam. Trypsin was assayed with alpha-benzoyl-DL-arginine-p-nitroanilide HCl and chymotrypsin with glutaryl-L-phenylalanine-p-nitroaniline. The effects of pH on specific activity over the range 7.5-9.5 were negligible relative to temperature effects. Specific activity and maximal reaction velocity extrapolated from a Lineweaver-Burke plot (Vmax) increased with an increase in temperature in a similar fashion (Q10 ca. 2 over temperature range of physiological significance), whereas Km was constant over the same temperature range. The advantage of the warm cecum is that protein is digested in about one-third the time, so that these tuna can process about three times as much food per day.

1. The ability of fish gills to transfer heat was measured by applying a heat pulse to blood in the ventral aorta and measuring it before and after passing through the gills of a teleost, Hemitripterus americanus. 2. 80-90% of heat contained in the blood is lost during passage through the gills. 3. The fraction of heat not lost during passage through the gills is due to direct transfer of heat between the afferent and efferent artery within the gill bar. 4. The major fraction of metabolic heat (70 - 90%) is lost through the body wall and fins of the sea raven in sea water at 5 degrees C; the remainder is lost through the gills.

We review studies claiming that fish feel pain and find deficiencies in the methods used for pain identification, particularly for distinguishing unconscious detection of injurious stimuli (nociception) from conscious pain. Results were also frequently misinterpreted and not replicable, so claims that fish feel pain remain unsubstantiated. Comparable problems exist in studies of invertebrates. In contrast, an extensive literature involving surgeries with fishes shows normal feeding and activity immediately or soon after surgery. C fiber nociceptors, the most prevalent type in mammals and responsible for excruciating pain in humans, are rare in teleosts and absent in elasmobranchs studied to date. A-delta nociceptors, not yet found in elasmobranchs, but relatively common in teleosts, likely serve rapid, less noxious injury signaling, triggering escape and avoidance responses. Clearly, fishes have survived well without the full range of nociception typical of humans or other mammals, a circumstance according well with the absence of the specialized cortical regions necessary for pain in humans. We evaluate recent claims for consciousness in fishes, but find these claims lack adequate supporting evidence, neurological feasibility, or the likelihood that consciousness would be adaptive. Even if fishes were conscious, it is unwarranted to assume that they possess a human-like capacity for pain. Overall, the behavioral and neurobiological evidence reviewed shows fish responses to nociceptive stimuli are limited and fishes are unlikely to experience pain. [ABSTRACT FROM AUTHOR]

Growth hormone transgenic coho salmonOncorhynchus kisutchfed at the same ration level as non-transgenic controls(Tc) had the same growth rate as non-transgenic controls(Nt). In contrast, growth hormone transgenic coho salmon(Tf) fedad libitumate about twice as much and had much higher growth rates than the other two groups. The most obvious result was the significantly larger caeca in the Tf group relative to both Nt or pair-fed Tc. The Tf fish had more caeca that were longer. The results suggested that the effect was indirect and the enlarged caeca required both the GHtransgene and hyperphagia to cause enlarged caecal capacity. A small part of the results, however, also suggested that there was a direct effect of the GHtransgene on some gut tissues, particularly the intestine. [ABSTRACT FROM AUTHOR]

In a previous study we showed that many of the morphological features of the respiratory system of GH (growth hormone) transgenic Atlantic salmon are greater than similarly sized control salmon. Here we show that the manifestation of GH transgene is similar in two different lines of GH transgenic Pacific coho salmon, but that it is very different from that in the GH transgenic Atlantic salmon. The GH transgenic Pacific coho salmon do not have a larger gill surface area than similarly sized control fish. [ABSTRACT FROM AUTHOR]

As a result of growing demand for immediate‐release sedatives in fisheries research, electroimmobilization has been receiving increasing attention due to its superior induction and recovery times and practicality, particularly under field conditions. However, a review of electroimmobilization and its role in fisheries science has not been previously conducted. Here we describe and differentiate the various forms of electroimmobilization and attempt to standardize relevant terminology. We review the known efficacy of electroimmobilization of fish and summarize the current available knowledge on this topic while identifying major knowledge gaps. Although more information is needed to determine optimal forms and settings for different species, life history stages, and environmental variables, electroimmobilization is a useful tool for fish handling that equals or surpasses the capabilities of chemical sedatives without exacerbating (and sometimes reducing) the negative consequences associated with chemical sedatives and fish handling practices more generally. [ABSTRACT FROM AUTHOR]