Behavioural indicators of welfare in farmed fish

Behaviour represents a reaction to the environment as fish perceive it and is therefore a key element of fish welfare. This review summarises the main findings on how behavioural changes have been used to assess welfare in farmed fish, using both functional and feeling-based approaches. Changes in foraging behaviour, ventilatory activity, aggression, individual and group swimming behaviour, stereotypic and abnormal behaviour have been linked with acute and chronic stressors in aquaculture and can therefore be regarded as likely indicators of poor welfare. On the contrary, measurements of exploratory behaviour, feed anticipatory activity and reward-related operant behaviour are beginning to be considered as indicators of positive emotions and welfare in fish. Despite the lack of scientific agreement about the existence of sentience in fish, the possibility that they are capable of both positive and negative emotions may contribute to the development of new strategies (e. g. environmental enrichment) to promote good welfare. Numerous studies that use behavioural indicators of welfare show that behavioural changes can be interpreted as either good or poor welfare depending on the fish species. It is therefore essential to understand the species-specific biology before drawing any conclusions in relation to welfare. In addition, different individuals within the same species may exhibit divergent coping strategies towards stressors, and what is tolerated by some individuals may be detrimental to others. Therefore, the assessment of welfare in a few individuals may not represent the average welfare of a group and vice versa. This underlines the need to develop on-farm, operational behavioural welfare indicators that can be easily used to assess not only the individual welfare but also the welfare of the whole group (e. g. spatial distribution). With the ongoing development of video technology and image processing, the on-farm surveillance of behaviour may in the near future represent a low-cost, noninvasive tool to assess the welfare of farmed fish.Fundação para a Ciência e Tecnologia, Portugal [SFRH/BPD/42015/2007]info:eu-repo/semantics/publishedVersio

Behavioural responses under different feeding methods and light regimes of the African catfish (Clarias gariepinus) juveniles

Little is known about the behaviour of fish under culture conditions. Several factors may have a direct effect on fish behaviour and its variations during the day. This study assessed the effect of feeding method (continuous by self-feeders vs. twice a day hand-feeding), light intensity (15 vs. 150 1x) and photoperiod [continuous light vs. 12 h darkness and 12 h light (12D:12L)] on behaviour of juvenile African Catfish (Clarias gariepinus). Sixteen aquaria, each with 30 fish (average initial weight of 55 g) were used during a 6-week experimental period. Fish behaviour was recorded by direct observation. Fish were more active under hand-feeding regime than under self-feeding. Fish spent more time swimming under continuous light than under a 12D:12L. Furthermore, the time that fish spent swimming was higher at high light intensity (150 1x) than under low light intensity (15 1x). Aggression was affected by photoperiod and light intensity. Continuous light resulted in 41.6% more scars and wounds than the 1213:12L photoperiod, while high light intensity resulted in 2.46 times more scars and wounds than low light intensity. Fish that spent more time swimming and browsing were more aggressive, and they had more scars and wounds on the body. Fish under the hand-feeding method showed a higher activity during the morning compared to the afternoon. Fish also showed a higher activity before each meal (morning and afternoon meals) than afterwards. These activities were more evident during the mornings. The current study demonstrated that for juveniles of the African catfish, swimming activity and agonistic behaviour are strongly affected by husbandry conditions. (C) 2004 Elsevier B.V. All rights reserved

Photoperiod affects growth, behaviour and stress variables in Clarias gariepinus

Short periods of light or no light (18D : 06L and 24D : 00L) resulted in an increased growth compared to extended periods of light (06D : 18L and 12D : 12L) in African catfish Clarias gariepinus. Fish under longer periods of light (12D : 12L and 18D : 06L) showed higher swimming activity, more aggression (injuries on the body) and higher lactate, free fatty acids and cortisol levels compared to those who were reared at shorter periods of light (24D : 00L and 18D : 06L). Feeding activity during light and dark periods in this experiment showed that C. gariepinus had both night and day feeding activities, with a preference to diurnal feeding in the 12D : 12L photoperiod. The results showed that light plays an important role in the African catfish behaviour and its wellbeing. As the hours of light increased during the 24 h cycle, data suggests that the fish were more stressed and aggressive, compared to those under a reduced number of light hours

Survival and growth of Pseudoplatystoma corruscans (Pisces - Pimelodidae) larvae: effect of photoperiod Sobrevivência e crescimento de larvas de surubim, Pseudoplatystoma corruscans (Pisces, Pimelodidae): efeito do fotoperíodo

The survival and the growth of Pseudoplatystoma corruscans larvae exposed to four photoperiods: light:dark (LD) 0:24, LD 10:14, LD 14:10, and LD 24:0, in a brackish water (5&#8240;) culture were analyzed. Larvae were fed with Artemia sp. nauplii at a 500 nauplii/larvae/day ratio. Survival on day 5 was inversely related to the length of photoperiod. From days 5 to 10, intermediate photoperiods resulted in a better survival, although LD 0:24 and LD 14:10 resulted in similar survival on day 10. Larvae presented higher weight at intermediate photoperiods. The results suggested that photoperiod requirements shifted during early development of P. corruscans larvae.<br>A sobrevivência e o crescimento de larvas de surubim, Pseudoplatystoma corruscans, submetidas a quatro fotoperíodos: luz:escuro (LE) 0:24, LE 10:14, LE 14:10 e LE 24:0 em água salinizada (5&#8240;) foram avaliadas. As larvas foram alimentadas com náuplios de Artemia sp. na proporção de 500 náuplios/larva/dia. Após cinco dias de experimento, a sobrevivência apresentou relação inversa ao aumento do fotoperíodo. Entre o quinto e o 10º dia, houve tendência de maior sobrevivência nos fotoperíodos intermediários, mas foram registradas sobrevivências semelhantes no intervalo entre LE 0:24 e LE 14:10 no 10º dia. As larvas apresentaram maior peso nos fotoperíodos intermediários. Os resultados sugerem que a exigência de fotoperíodo das larvas de P. corruscans sofre mudanças durante o cultivo