Human beings may affect the welfare of fish through fisheries, aquaculture and a number of other activities. There is no agreement on just how to weigh the concern for welfare of fish against the human interests involved, but ethical frameworks exist that suggest how this might be approached.Different definitions of animal welfare focus on an animal's condition, on its subjective experience of that condition and/or on whether it can lead a natural life. These provide different, legitimate, perspectives, but the approach taken in this paper is to focus on welfare as the absence of suffering.An unresolved and controversial issue in discussions about animal welfare is whether nonhuman animals exposed to adverse experiences such as physical injury or confinement experience what humans would call suffering. The neocortex, which in humans is an important part of the neural mechanism that generates the subjective experience of suffering, is lacking in fish and non-mammalian animals, and it has been argued that its absence in fish indicates that fish cannot suffer. A strong alternative view, however, is that complex animals with sophisticated behaviour, such as fish, probably have the capacity for suffering, though this may be different in degree and kind from the human experience of this state.Recent empirical studies support this view and show that painful stimuli are, at least, strongly aversive to fish. Consequently, injury or experience of other harmful conditions is a cause for concern in terms of welfare of individual fish. There is also growing evidence that fish can experience fear-like states and that they avoid situations in which they have experienced adverse conditions. Human activities that potentially compromise fish welfare include anthropogenic changes to the environment, commercial fisheries, recreational angling, aquaculture, ornamental fish keeping and scientific research. The resulting harm to fish welfare is a cost that must be minimized and weighed against the benefits of the activity concerned.Wild fish naturally experience a variety of adverse conditions, from attack by predators or conspecifics to starvation or exposure to poor environmental conditions. This does not make it acceptable for humans to impose such conditions on fish, but it does suggest that fish will have †Author to whom correspondence should be addressed. Tel.: þ 44 (0) 141 330 5975; fax: þ 44 (0) 330 5971;

No abstract

Nociception is the detection of a noxious tissue-damaging stimulus and is sometimes accompanied by a reflex response such as withdrawal. Pain perception, as distinct from nociception, has been demonstrated in birds and mammals but has not been systematically studied in lower vertebrates. We assessed whether a fish possessed cutaneous nociceptors capable of detecting noxious stimuli and whether its behaviour was sufficiently adversely affected by the administration of a noxious stimulus. Electrophysiological recordings from trigeminal nerves identified polymodal nociceptors on the head of the trout with physiological properties similar to those described in higher vertebrates. These receptors responded to mechanical pressure, temperatures in the noxious range (more than 40°C) and 1% acetic acid, a noxious substance. In higher vertebrates nociceptive nerves are either A-delta or C fibres with C fibres being the predominating fibre type. However, in the rainbow trout A-delta fibres were most common, and this offers insights into the evolution of nociceptive systems. Administration of noxious substances to the lips of the trout affected both the physiology and the behaviour of the animal and resulted in a significant increase in opercular beat rate and the time taken to resume feeding, as well as anomalous behaviours. This study provides significant evidence of nociception in teleost fishes and furthermore demonstrates that behaviour and physiology are affected over a prolonged period of time, suggesting discomfort.

Many decisions in the lives of animals and humans require a fine balance between the exploration of different options and the exploitation of their rewards. Do you buy the advertised car, or do you testdrive different models? Do you continue feeding from the current patch of flowers, or do you fly off to another one? Do you marry your current partner, or try your luck with someone else? The balance required in these situations is commonly referred to as the exploration-exploitation tradeoff. It features prominently in a wide range of research traditions, including learning, foraging, and decisionmaking literatures. Here, we integrate findings from these and other often-isolated literatures in order to gain a better understanding of the possible tradeoffs between exploration and exploitation, and we propose new theoretical insights that might guide future research. Specifically, we explore how potential tradeoffs depend on (1) the conceptualization of exploration and exploitation; (2) the influencing environmental, social, and individual factors; (3) the scale at which exploration and exploitation are considered; (4) the relationship and types of transitions between the two behaviors; and (5) the goals of the decision maker. We conclude that exploration and exploitation are best conceptualized as points on a continuum, and that the extent to which an agent's behavior can be interpreted as exploratory or exploitative depends upon the level of abstraction at which it is considered.

Explaining consistent variation in the behaviour of individuals in terms of personality differences is one of the cornerstones of understanding human behaviour but is seldom discussed in behavioural ecology for fear of invoking anthropomorphism. Recently, however, interest has begun to focus on identifying personality traits in animals and examining their possible evolutionary consequences. One major axis used to define personality traits is the shyness-boldness continuum. We examined boldness in an in situ experiment using fish from eight populations of the poeciliid Brachyraphis episcopi (also referred to as Brachyrhaphis episcopi). Fish from high-and low-predation regions within four streams that run independently into the Panama Canal were tested. Boldness scores were strongly influenced by standard length and the relative level of predation pressure in the rivers. In all four rivers, fish from high-predation areas were bolder than those from low-predation areas. Fish became increasingly shy as they grew. Animals are expected to titrate energy intake closely with predation risk and hundreds of studies support this notion (reviewed in Lima 1998). For example, when a risky patch had four times the amount of food available than a low-risk patch, fish accepted the higher risk in return for a higher foraging reward (Pitcher et al. 1988). Not all individuals in a population solve the problem in the same way, however. In laboratory assays of foraging behaviour under predation risk, there is a continuum of responses within a population of prey species, from complete recklessness to complete predator avoidance (Fraser & Huntingford 1986). These behavioural extremes correspond closely to the shyness-boldness spectrum, recognizable psychological states that exist in a diverse suite of taxa, from crustaceans to humans (Wilson et al. 1994; Gosling 2001). Although many studies have concentrated on the heritability of individual differences in temperament (Goddard & Bilharz 1985), this range of responses is also determined by life experiences (van Gestel & van Broeckhoven 2003), and, as such, should be influenced by environmental variables during ontogeny. While the two mechanisms are by no means mutually exclusive, the manner in which the environment shapes and maintains shyness-boldness traits over both evolutionary and ontogenetic timeframes has received little attention from behavioural ecologists. Comparative analyses are frequently used to address potential differences in animal behaviour caused by variable exposure to selection pressures that result from the occupation of different environments (Kamil & Balda 1990). Testing populations of the same species that occupy different habitats allows us to examine how the environment affects the determination of personality traits while minimizing the possible confounds of phylogeny.

Rokeach's (1973) Value Survey has received widespread use in the past decade, but little attempt has been made to examine the extent to which the 36 items provide comprehensive and representative coverage of the value domain. Our data provide qualified support for the comprehensiveness of the instrument. The major weaknesses in sampling involve the facets of physical well-being and individual rights. Other areas not represented are thriftiness and carefreeness. The need for multi-item indexes for value constructs are discussed, as are the advantages of a rating procedure over a ranking procedure from both psychometric and empirically valid perspectives. An alternative instrument based on the work of Rokeach is proposed.

Individual variation in behaviour within populations may be explained in part by demographics and longterm, stable individual psychological differences. We examined the relation between boldness (taken as the time to emerge from a shelter and explore a novel environment) and body size in eight populations of the poeciliid Brachyraphis episcopi originating from sites upstream and downstream of waterfalls in four rivers that run into the Panama Canal. The relation between body size and time to emerge from a shelter was positive, with larger fish taking longer to emerge. This relation differed between downstream and upstream sites, being significant in the upstream populations only. These results are best explained by a metabolic hypothesis whereby juvenile fish are compelled to emerge earlier in order to resume feeding. In the downstream sites this effect was slightly offset by the relatively greater predation threat for smaller fish, such that they delayed their emergence from cover. We discuss the underlying importance of variation in boldness and its effects on other behavioural and life history traits.

Different kinds of experience during early life can play a significant role in the development of an animal's behavioural phenotype. In natural contexts, this influences behaviours from anti-predator responses to navigation abilities. By contrast, for animals reared in captive environments, the homogeneous nature of their experience tends to reduce behavioural flexibility. Studies with cage-reared rodents indicate that captivity often compromises neural development and neural plasticity. Such neural and behavioural deficits can be problematic if captive-bred animals are being reared with the intention of releasing them as part of a conservation strategy. Over the last decade, there has been growing interest in the use of environmental enrichment to promote behavioural flexibility in animals that are bred for release. Here, we describe the positive effects of environmental enrichment on neural plasticity and cognition in juvenile Atlantic salmon (Salmo salar). Exposing fish to enriched conditions upregulated the forebrain expression of NeuroD1 mRNA and improved learning ability assessed in a spatial task. The addition of enrichment to the captive environment thus promotes neural and behavioural changes that are likely to promote behavioural flexibility and improve post-release survival.