Net-biting and escape behaviour in farmed Atlantic cod Gadus morhua: effects of feed stimulants and net traits (original) (raw)
Related papers
Applied Animal Behaviour Science, 2012
The escape of fish from aquaculture is a persistent economic problem for farmers as well as an environmental problem that threatens wild fish population as a consequence of potential negative ecological and genetic interactions. Farmed Atlantic cod (Gadus morhua) cause significant damage by biting the net and creating holes through which they escape. We determined the role of food, cage enrichment, net damage, and individual temperament on net biting behavior. During four separate trials, net interactions by fish were observed in relation to combinations of the above treatments. Fish with no access to food and in plain (not enriched) cages interacted the most with the net wall, with 7.5 and 12.6 more interactions per h, respectively, than fish with food that were in enriched cages (food P = 0.01; enrichment P < 0.01). Of the stimulating objects used to enrich cages, 97% of interactions were with the tubes that provided refuge (P < 0.01). Cod were attracted to damaged areas of net, interacting 0.12 more times per h than at undamaged areas (P < 0.01). Individuals showed consistent behavior over time, but there was no relationship between temperament and net interactions (P = 0.17). The results indicate that appropriate feeding levels and cage enrichment may lead to reduced net interactions and thus fewer holes, reducing the potential for fish to escape.
Aquaculture, 2009
A self-contained data collection system is described that was used to investigate the behavior of Atlantic cod (Gadus morhua) in an offshore net pen (Sea Station 3000) located 13 km off the coast of New Hampshire, USA. The entire system was housed inside a modified U.S. Coast Guard (USCG) navigational buoy that was retrofitted for this purpose. Power was provided by a combination of eight 12 V batteries, two solar panels and a wind generator. The behavior of the population of cod as a whole, during daylight hours, was monitored using four waterproof cameras connected to a four channel digital video recorder. The behavior of 4-12 individual fish implanted with ultrasonic transmitters was continuously recorded, during each of four study periods, using a HTI model 291 ultrasonic telemetry system. Laboratory studies showed no influence of transmitter implantation on swimming or feeding behavior. Transmitters were programmed to "ping" at intervals between 1.7 and 3.3 s and they typically lasted for about one month. The system successfully detected and plotted 84.9 ± 6.0% of transmissions, resulting in an average of 1283.4 ± 252.5 positional fixes for each animal, during each hour of the study. This preliminary evaluation of cod behavior in a net pen demonstrated that they are diurnally active and have a tendency to mill about, rather than school. Cod predominately used the lower half of the cage, except when rising to the feeding area during periods when feed was delivered. The system that was developed proved to be ideal for investigating the behavior of fish within a net pen, and it can be used by both inshore and offshore farms to gather behavioral data that can lead to improvements in the efficiency of aquaculture operations.
The behavior of cod (Gadus morhua) in an offshore aquaculture net pen
Aquaculture, 2011
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Behavioural indicators of welfare in farmed fish
Fish physiology and …, 2012
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.
Escape-related behaviour of Atlantic cod, Gadus morhua L., in a simulated farm situation
Aquaculture Research, 2008
Cultured ¢sh escaping from farms represent an economic loss as well as a potential problem for wild ¢sh populations. This study investigated the escape-related behaviour of farmed Norwegian coastal and northeast Arctic cod (NEAC), Gadus morhua L. Six groups of ¢sh were observed during three replicate trials in a large tank that was split into two equal parts by a net wall. The ¢sh could move freely through an opening in the net during the trials. Three groups were not fed during the trials. The ¢rst escape occurred shortly after producing the net opening (11 AE 10.5 min; mean AE standard deviation). Norwegian coastal cod were more prone to escape than the NEAC. A starvation period of 9 days increased the number of ¢sh on the escape side of the tank. Net biting and net inspection by the ¢sh were frequently observed, irrespective of whether the ¢sh were fed or not. The same ¢sh were repeatedly found on the escape side of the tank, but the propensity for recurrent escape behaviour was not related to genotype, feeding status or size. The results suggest that other factors, such as individual variation in boldness or exploration behaviour, could a¡ect the willingness to escape.
Canadian Journal of Fisheries and Aquatic Sciences, 2017
We tested the ability of stimulators to improve the release efficiency of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) through the meshes of a square mesh section installed in a trawl. The section was tested in three different configurations: without any stimulation device, with a mechanical stimulation device, and with LED light stimulation devices. We analysed and compared the behaviour of cod and haddock in all three configurations based on release results and underwater recordings. Parallel to the fishing trials, we carried out fall-through tests to determine the upper physical size limits for cod and haddock to be able to escape through the square meshes in the section. This enabled us to infer whether lack of release efficiency was due to fish behaviour or release potential of the square meshes in the section. The results showed that the escape behaviour of haddock can be triggered by mechanical stimulation. In contrast, cod did not react significantly to the pres...
Introduction: aquaculture and behaviour
This chapter starts by providing a review of what aquaculture is, which finfish are farmed, for what purposes and in what kinds of culture systems. It then considers what behaviour is, why biologists are interested in behaviour and how they study and explain it. The question of the complexity of fish behaviour is addressed, leading into a discussion of fish welfare and how it can be defined, identified and measured. The issues of domestication, selective breeding and the extent to which fish are domesticated animals are then covered, as are the effects of captive rearing; in both cases, effects on behaviour are given special consideration. The criteria for effective, sustainable fish culture are then spelled out; these include efficient production, environmental protection (with respect to land, water and feed resources and to impacts on wild fish populations) and fish welfare. Possible strategies for improving the welfare of farmed fish are discussed and consideration given to what is required of the behaviour of fish cultured for food, for science and the ornamental trade and for release. Finally, an outline is given of the structure and content of the remaining 10 chapters of this book.
Response of captive seabass and seabream as behavioural indicator in aquaculture
Italian Journal of Animal Science, 2010
Welfare of cultivate fish at high-density represents an important concern for modern aquaculture. The behaviour of European seabass (Dicentrarchus labrax) and seabream (Sparus aurata) reared in cages was studied in a fish farm of northern Sardinia (Italy) in autumn 2006 to test whether captive condition had an effect on the movement patterns of these two species. Video images recorded before, during and after the manual feeding distribution allowed us to collect data on different behaviours of captive fish. Thus, behaviours indicating the position of fish in the water column, swimming direction and possible aggressive behaviours (aggression, direction change and collision) showed juveniles and adults of seabass and seabream were overall affected by feeding rhythms and captive overcrowding. Seabream had a major tendency to swim towards the bottom and higher frequency of horizontal swimming and collisions than seabass. The overall behavioural difference between two species was explained in terms of their differences in ecological features in the wild.
Aquaculture Research, 2013
Atlantic cod and other teleosts with closed swimbladders have slow gas resorption rates and are therefore vulnerable to sudden pressure reductions that lead to swimbladder expansion and possible loss of behavioural control. This problem is of particular relevance to fish farmers, who require safe protocols for lifting of cages containing cod that account for swimbladder expansion. To recommend a limit for pressure reduction, we experimentally determined the maximum pressure reduction, relative to neutral buoyancy pressure, free-swimming farmed cod would expose themselves to. Classical reward conditioning was used to motivate cod that were neutrally buoyant at 2-3.3 ATM (10-23 m depth) to respond to a sound signal by swimming rapidly upwards to a feeding station positioned at 1.5 ATM (5 m depth). Sixteen cod were implanted with data storage tags (DSTs) that registered their ambient pressure throughout the experiment. The DST data showed that cod voluntarily stopped rapid ascents before they reached the feeding station at an average maximum pressure reduction of about 41% relative to their neutral buoyancy pressure. This was equivalent to a 70% swimbladder expansion relative to neutral volume. During the experiment, cod seldom remained above their neutral buoyancy depths, except when feeding, indicating a behavioural aversion to positive buoyancy. To avoid the loss of buoyancy control in cod, we conclude that single lifting events of seacages, which forces swimbladder expansion, should never exceed a 70% expansion of the swimbladder above the pre-existing neutral buoyancy volume.