Olav Moberg

Effects of early experience on group behaviour in fish

Animal Behaviour, Oct 1, 2007

Animals that undergo a habitat shift face a number of challenges as they move between habitats; f... more Animals that undergo a habitat shift face a number of challenges as they move between habitats; for example, they may encounter new predator species and may be vulnerable as they adapt to their new surroundings. An ability to adapt quickly to the new environment is likely to influence post-transition survival, and an understanding of the development of this ability is important in species that we rear for conservation and reintroduction programmes. Juvenile cod, Gadus morhua, undergo a habitat shift during their development, and they are also a species where reintroduction work has been tried. Here, we describe an experiment that investigated the effects that rearing environment has on cod shoaling behaviour. Cod were tested just after they had undergone the transition from a pelagic to a more benthic existence. We found that cod reared in either an enriched or in a plain, standard hatchery environment differed in terms of their shoaling responses; the shoaling tendency of fish reared in enriched tanks varied between testing environments, but fish reared in plain environments responded in the same way across the testing conditions. We discuss the influence of early experience on the development of appropriate behavioural responses and the importance of this for captive-reared species that are released into the wild.

Download

Evolution of virulence under intensive farming: salmon lice increase skin lesions and reduce host growth in salmon farms

Journal of Evolutionary Biology, 2017

Parasites rely on resources from a host and are selected to achieve an optimal combination of tra... more Parasites rely on resources from a host and are selected to achieve an optimal combination of transmission and virulence. Human‐induced changes in parasite ecology, such as intensive farming of hosts, might not only favour increased parasite abundances, but also alter the selection acting on parasites and lead to life‐history evolution. The trade‐off between transmission and virulence could be affected by intensive farming practices such as high host density and the use of antiparasitic drugs, which might lead to increased virulence in some host–parasite systems. To test this, we therefore infected Atlantic salmon (Salmo salar) smolts with salmon lice (Lepeophtheirus salmonis) sampled either from wild or farmed hosts in a laboratory experiment. We compared growth and skin damage (i.e. proxies for virulence) of hosts infected with either wild or farmed lice and found that, compared to lice sampled from wild hosts in unfarmed areas, those originating from farmed fish were more harmful...

Download

The drivers of sea lice management policies and how best to integrate them into a risk management strategy: An ecosystem approach to sea lice management

Journal of Fish Diseases, 2017

The control of sea lice infestations on cultivated Atlantic salmon is a major issue in many regio... more The control of sea lice infestations on cultivated Atlantic salmon is a major issue in many regions of the world. The numerous drivers which shape the priorities and objectives of the control strategies vary for different regions/jurisdictions. These range from the animal welfare and economic priorities of the producers, to the mitigation of any potential impacts on wild stocks. Veterinary ethics, environmental impacts of therapeutants, and impacts for organic certification of the produce are, amongst others, additional sets of factors which should be considered. Current best practice in both EU and international environmental law advocates a holistic ecosystem approach to assessment of impacts and risks. The issues of biosecurity and ethics, including the impacts on the stocks of species used as cleaner fish, are areas for inclusion in such a holistic ecosystem assessment. The Drivers, Pressures, State, Impacts, Responses (DPSIR) process is examined as a decision-making framework and potential applications to sea lice management are outlined. It is argued that this is required to underpin any integrated sea lice management (ISLM) strategy to balance pressures and outcomes and ensure a holistic approach to managing the issue of sea lice infestations on farmed stock on a medium to long-term basis.

Download

JEBvirulencedata

Data from: Evolution of virulence under intensive farming: salmon lice increase skin lesions and reduce host growth in salmon farms

Parasites rely on resources from a host and are selected to achieve an optimal combination of tra... more Parasites rely on resources from a host and are selected to achieve an optimal combination of transmission and virulence. Human-induced changes in parasite ecology, such as intensive farming of hosts, might not only favor increased parasite abundances, but also alter the selection acting on parasites and lead to life history evolution. The trade-off between transmission and virulence could be affected by intensive farming practices such as high host density and the use of anti-parasitic drugs, which might lead to increased virulence in some host-parasite systems. To test this we therefore infected Atlantic salmon (Salmo salar) smolts with salmon lice (Lepeophtheirus salmonis) sampled either from wild or farmed hosts in a laboratory experiment. We compared growth and skin damage (i.e. proxies for virulence) of hosts infected with either wild or farmed lice and found that, compared to lice sampled from wild hosts in unfarmed areas, those originating from farmed fish were more harmful; they inflicted more skin damage to their hosts and reduced relative host weight gain to a greater extent. We advocate that more evolutionary studies should be done using farmed animals as study species, given the current increase in intensive food production practices that might be compared to a global experiment in parasite evolution

Second Interim Report of the Working Group on Aquaculture (WGAQUA)

Download

Determinants of sperm competition and the role of cryptic female choice in the broadcast spawning Atlantic cod (Gadus morhua)

Effects of light intensity on visual prey detection by juvenile Atlantic cod (Gadus morhuaL.)

Marine and Freshwater Behaviour and Physiology, 2010

Despite the research on this important fish species for more than a century, surprisingly little ... more Despite the research on this important fish species for more than a century, surprisingly little is known of some fundamental aspects of the biology of Atlantic cod, such as how light affects foraging behaviour. We measured the reactive distances of juvenile cod (age 1) over light intensities from 0.01 to 64 µmol m s in a controlled laboratory environment, and

Hypoxic avoidance behaviour in cod (Gadus morhua L.): The effect of temperature and haemoglobin genotype

Journal of Experimental Marine Biology and Ecology, 2008

Hypoxia can influence fish growth, survival and on larger scales, population structure. These eff... more Hypoxia can influence fish growth, survival and on larger scales, population structure. These effects may be influenced by water temperature, and may vary intra-specifically with genotype. In Atlantic cod (Gadus morhua L.), the two haemoglobin homozygotes (Hb-I⁎11 and Hb-I⁎22) vary in oxygen affinity at different temperatures, which is thought to correspond to variation in hypoxia tolerance. We therefore tested if hypoxic avoidance behaviour in cod 1) depends on ambient temperature and 2) is modified by haemoglobin genotype. In a laminar flow choice box, we subjected juvenile cod to an initial phase of non-escapable hypoxia, and a subsequent recovery phase, where one habitat was kept at 20% O 2 saturation while the other was raised in steps to full saturation. The experiment was performed at 5 and 15°C with Hb-I⁎11 and Hb-I⁎22 cod. Cod responded to inescapable hypoxia by reducing their overall swimming speed and then, at the initial levels of the recovery phase, avoiding the most hypoxic habitat, irrespective of temperature or genotype. Fish recovered quickly as O 2 levels increased, as evidenced by increased swimming speed and time spent in the most hypoxic habitat. The avoidance response depended strongly on temperature: the relative reduction in speed and avoidance of the most hypoxic habitat was more pronounced at 15 than at 5°C. During the recovery phase, stressed fish initially maintained a higher swimming speed in the most hypoxic habitat. However, as O 2 increased, swimming speed in both habitats converged. This point of convergence occurred at a lower O 2 saturation at 5°C. Fish ventilation rate in inescapable hypoxia was also higher at 15°C. Haemoglobin genotype did not influence either ventilation rates or the nature of the hypoxic avoidance response at either temperature, but Hb-I⁎11 cod swam faster than Hb-I⁎22 cod in normoxia at 15°C. Our results indicate that increased temperature limits the ability of cod of both haemoglobin genotypes to exploit hypoxic habitats. This may have negative future consequences for coastal cod stocks in light of increasing global temperatures and eutrophication in coastal waters.

Download

Effects of habitat enrichment and food availability on the foraging behaviour of juvenile Atlantic Cod (Gadus morhua L)

Environmental Biology of Fishes, 2011

The environment can play an important role in shaping how an animal behaves, and how well the ani... more The environment can play an important role in shaping how an animal behaves, and how well the animal performs in a particular environment can be influenced by early experiences. The tradition of releasing captive-reared juveniles into the wild in an effort to strengthen wild fish populations has often had little success owing to high post-release mortality. Fish reared under standard hatchery conditions are provided with fewer stimuli and they receive excess quantities of pellet food that are easy to handle and consume. Captive reared fish therefore appear to be under-stimulated and overfed. Several studies have demonstrated that simple structural enrichment in the rearing facilities promotes flexible behaviour compared to fish reared in plain, standard hatchery tanks. Less attention has been given to the effects of the diet. Here we use a cross-factored design to test the relative role of food ration and spatial enrichment on foraging behaviour. Our results show that fish from enriched environments, regardless of previous food-ration size, were more reluctant to start feeding on the first day in a novel arena. On day two and three, however, fish with prior experience of a low food ration showed greater foraging activity and efficiency than fish fed on full rations. On the second and third day, prior experience with enrichment was less important. We discuss how early feeding experience in combination with structural enrichment may contribute in producing fish that are better suited for release into the wild.

Download

Effects of early experience on group behaviour in fish

Animal Behaviour, 2007

Animals that undergo a habitat shift face a number of challenges as they move between habitats; f... more Animals that undergo a habitat shift face a number of challenges as they move between habitats; for example, they may encounter new predator species and may be vulnerable as they adapt to their new surroundings. An ability to adapt quickly to the new environment is likely to influence post-transition survival, and an understanding of the development of this ability is important in species that we rear for conservation and reintroduction programmes. Juvenile cod, Gadus morhua, undergo a habitat shift during their development, and they are also a species where reintroduction work has been tried. Here, we describe an experiment that investigated the effects that rearing environment has on cod shoaling behaviour. Cod were tested just after they had undergone the transition from a pelagic to a more benthic existence. We found that cod reared in either an enriched or in a plain, standard hatchery environment differed in terms of their shoaling responses; the shoaling tendency of fish reared in enriched tanks varied between testing environments, but fish reared in plain environments responded in the same way across the testing conditions. We discuss the influence of early experience on the development of appropriate behavioural responses and the importance of this for captive-reared species that are released into the wild.

Download

Working Group on Environmental Interactions of Aquaculture (WGEIA)

Ocean Ranching

Encyclopedia of Ocean Sciences, 2019

Environmental enrichment promotes neural plasticity and cognitive ability in fish

Proceedings of the Royal Society B: Biological Sciences, 2013

Different kinds of experience during early life can play a significant role in the development of... more 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 ...

Download

Effects of habitat enrichment and food availability on the foraging behaviour of juvenile Atlantic Cod ( Gadus morhua L

Environmental Biology of Fishes, 2011

The environment can play an important role in shaping how an animal behaves, and how well the ani... more The environment can play an important role in shaping how an animal behaves, and how well the animal performs in a particular environment can be influenced by early experiences. The tradition of releasing captive-reared juveniles into the wild in an effort to strengthen wild fish populations has often had little success owing to high post-release mortality. Fish reared under standard hatchery conditions are provided with fewer stimuli and they receive excess quantities of pellet food that are easy to handle and consume. Captive reared fish therefore appear to be under-stimulated and overfed. Several studies have demonstrated that simple structural enrichment in the rearing facilities promotes flexible behaviour compared to fish reared in plain, standard hatchery tanks. Less attention has been given to the effects of the diet. Here we use a cross-factored design to test the relative role of food ration and spatial enrichment on foraging behaviour. Our results show that fish from enriched environments, regardless of previous food-ration size, were more reluctant to start feeding on the first day in a novel arena. On day two and three, however, fish with prior experience of a low food ration showed greater foraging activity and efficiency than fish fed on full rations. On the second and third day, prior experience with enrichment was less important. We discuss how early feeding experience in combination with structural enrichment may contribute in producing fish that are better suited for release into the wild.

Download

Effects of light intensity on visual prey detection by juvenile Atlantic cod (Gadus morhua L

Marine and Freshwater Behaviour and Physiology, 2010

Despite the research on this important fish species for more than a century, surprisingly little ... more Despite the research on this important fish species for more than a century, surprisingly little is known of some fundamental aspects of the biology of Atlantic cod, such as how light affects foraging behaviour. We measured the reactive distances of juvenile cod (age 1) over light intensities from 0.01 to 64 µmol m−2 s−1 in a controlled laboratory environment, and used these results to estimate the visual range and the parameters for a predictive visual model. The reactive distance at 0.01 µmol m−2 s−1 indicated high sensitivity to low light conditions. The reactive distance was less at intermediate light levels (1.5–6.5 µmol m−2 s−1) and increased thereafter. Only a model with a different set of parameters above and below 5 µmol m−2 s−1 fitted the data, but the validation of the model against another dataset indicated that the generality of the model was poor. We interpret these results as a change in foraging behaviour of juvenile cod at light intensities occurring at twilight in natural habitats, and the results illustrate how behaviour can complicate the relationship between light and reactive distance in a marine teleost.

Download

Hypoxic avoidance behaviour in cod ( Gadus morhua L.): The effect of temperature and haemoglobin genotype

Journal of Experimental Marine Biology and Ecology, 2008

Hypoxia can influence fish growth, survival and on larger scales, population structure. These eff... more Hypoxia can influence fish growth, survival and on larger scales, population structure. These effects may be influenced by water temperature, and may vary intra-specifically with genotype. In Atlantic cod (Gadus morhua L.), the two haemoglobin homozygotes (Hb-I⁎11 and Hb-I⁎22) vary in oxygen affinity at different temperatures, which is thought to correspond to variation in hypoxia tolerance. We therefore tested if hypoxic avoidance behaviour in cod 1) depends on ambient temperature and 2) is modified by haemoglobin genotype. In a laminar flow choice box, we subjected juvenile cod to an initial phase of non-escapable hypoxia, and a subsequent recovery phase, where one habitat was kept at 20% O 2 saturation while the other was raised in steps to full saturation. The experiment was performed at 5 and 15°C with Hb-I⁎11 and Hb-I⁎22 cod. Cod responded to inescapable hypoxia by reducing their overall swimming speed and then, at the initial levels of the recovery phase, avoiding the most hypoxic habitat, irrespective of temperature or genotype. Fish recovered quickly as O 2 levels increased, as evidenced by increased swimming speed and time spent in the most hypoxic habitat. The avoidance response depended strongly on temperature: the relative reduction in speed and avoidance of the most hypoxic habitat was more pronounced at 15 than at 5°C. During the recovery phase, stressed fish initially maintained a higher swimming speed in the most hypoxic habitat. However, as O 2 increased, swimming speed in both habitats converged. This point of convergence occurred at a lower O 2 saturation at 5°C. Fish ventilation rate in inescapable hypoxia was also higher at 15°C. Haemoglobin genotype did not influence either ventilation rates or the nature of the hypoxic avoidance response at either temperature, but Hb-I⁎11 cod swam faster than Hb-I⁎22 cod in normoxia at 15°C. Our results indicate that increased temperature limits the ability of cod of both haemoglobin genotypes to exploit hypoxic habitats. This may have negative future consequences for coastal cod stocks in light of increasing global temperatures and eutrophication in coastal waters.

Download

Effects of early experience on group behaviour in fish

Animal Behaviour, 2007

Animals that undergo a habitat shift face a number of challenges as they move between habitats; f... more Animals that undergo a habitat shift face a number of challenges as they move between habitats; for example, they may encounter new predator species and may be vulnerable as they adapt to their new surroundings. An ability to adapt quickly to the new environment is likely to influence post-transition survival, and an understanding of the development of this ability is important in species that we rear for conservation and reintroduction programmes. Juvenile cod, Gadus morhua, undergo a habitat shift during their development, and they are also a species where reintroduction work has been tried. Here, we describe an experiment that investigated the effects that rearing environment has on cod shoaling behaviour. Cod were tested just after they had undergone the transition from a pelagic to a more benthic existence. We found that cod reared in either an enriched or in a plain, standard hatchery environment differed in terms of their shoaling responses; the shoaling tendency of fish reared in enriched tanks varied between testing environments, but fish reared in plain environments responded in the same way across the testing conditions. We discuss the influence of early experience on the development of appropriate behavioural responses and the importance of this for captive-reared species that are released into the wild.

Download

Related Authors

Uploads

Papers by Olav Moberg

Log In