Atlantic cod (Gadus morhua L.) is one of the most important commercial fish species in Norway and... more Atlantic cod (Gadus morhua L.) is one of the most important commercial fish species in Norway and the peak fishing season coincides with spawning from January to April. Live-storage of cod may extend the marketing season for fresh cod products. Cod can be held for up to 12 weeks after capture, and current regulations allow the fish to be held without feeding for four weeks. We investigated whether the response to long-term feed deprivation differed between mature males and females. The fish, caught off Andenes (Norway) in March 2015 using Danish seine, were held without feeding for 82 days, and samples were taken 2, 26, 54 and 82 days after capture. At each sampling, the weights of whole and gutted fish (head on), liver and gonads were measured. Additionally, fillet protein concentrations were analysed. Females lost total weight, gutted weight and liver mass more rapidly than males, but the reduction in gonad mass was significantly higher in males than in females. At termination, after 82 days, fillet protein concentration in males was higher (16.3% ± 0.4) than in females (14.9% ± 0.4). With regard to loss of gutted weight and reduction in muscle protein concentration, the tolerable fasting period of mature spawning Atlantic cod of good biological condition is 54 days, but this can vary depending on upon the initial condition of the fish
The purpose of the current study was to examine seasonal changes in seawater tolerance and growth... more The purpose of the current study was to examine seasonal changes in seawater tolerance and growth performance of anadromous Arctic charr (Salvelinus alpinus L.) held at the same temperature (8°C) during winter and summer. Charr (20-27 cm), previously reared in freshwater under natural photoperiod, were transferred either directly (DT) from freshwater to seawater (35 ppt), from freshwater to brackish water (20 ppt), or were gradually adapted (GT) to seawater over a period of 10 days. Control fish were held in freshwater. Feed intake and osmoregulatory ability were then monitored on three occasions during the following 59 days. Two experiments were carried out, one during winter (December-January) and the other during summer (June-July). In both experiments fish mortality was low. Plasma osmolalities recorded in fish transferred to seawater were within normal ranges, but osmolalities on day 10, were significantly lower in summer (313 mOsm/kg (DT), 328 mOsm/kg (GT)) than in winter (323 mOsm/kg (DT), 352 mOsm/kg (GT)). In winter, feed intake and growth rates were high in fish kept in fresh and brackish water, but charr transferred directly to seawater ate little and lost weight. Fish that were gradually adapted to seawater occupied an intermediate position. During summer the observed differences in feed intake were small and all fish had relatively high growth rates. These results suggest that Arctic charr display seasonal changes in feed intake and growth performance that parallel seasonal changes in hypoosmoregulatory capacity. The ability to survive and hypoosmoregulate in full strength seawater does not, however, seem to be a particularly good indicator of successful seawater adaptation with respect to the ability to display high rates of feed intake and growth. During winter, a gradual transfer to seawater appeared to lead to improved feeding and growth compared to direct transfer.
The effects of long-term moderate exercise on the behaviour and the food intake – growth relation... more The effects of long-term moderate exercise on the behaviour and the food intake – growth relationship of individually marked Arctic charr, Salvelinus alpinus L., were examined. Direct monitoring of food intake of individual fish was carried out using an X-radiographic method. Growth (weight gain) was significantly improved with increasing swimming speed, and a maximum specific growth rate was obtained at a swimming speed of approximately 1.75 body lengths/s. Growth appeared to be suppressed by high levels of aggressive interactions, and an increase in swimming speed caused a marked increase in schooling behaviour, with a concomitant reduction in agonistic activity. The exercising fish did not consume more food than controls, and moderately exercised Arctic charr showed improved growth – food intake ratios at all levels of food intake compared with fish held in standing water. Furthermore, the proportions of nonfeeding fish were significantly reduced at increasing water velocities. Thus, the relationship between food intake and growth may be strongly influenced by agonistic activity, which appears to be most prevalent in fish subjected to low water velocities.
Following feeding, the rate of oxygen consumption of fishes increases to a peak and then slowly d... more Following feeding, the rate of oxygen consumption of fishes increases to a peak and then slowly declines to the pre-feeding level. Many factors have been shown to influence the magnitude and duration of post-prandial oxygen consumption and these include quantity and/or quality of ration and environmental temperature. The effects of the various factors are described and the phenomenon of the post-prandial increase in metabolic rate of fish is discussed in relation to work with other species of animals.
Preface. Fish: an introduction. Environmental links - sensory systems. Foodstuffs and feeding. Va... more Preface. Fish: an introduction. Environmental links - sensory systems. Foodstuffs and feeding. Vascular transport and gaseous exchange: the circulatory and respiratory systems. Physiological integration - nervous and endocrine systems. Digestion and absorption. Osmotic and ionic regulation - water and salt balance. Body form, swimming and movement through the water. Reproduction. Development of eggs and larvae. Recruitment and population fluctuations. Human impacts on aquatic envionments. Index.
... Amundsen, P.-A., Knudsen, R. & Klemetsen, A. (2008). Seasonal and ont... more ... Amundsen, P.-A., Knudsen, R. & Klemetsen, A. (2008). Seasonal and ontogenetic variation in resource use by two sympatric Arctic charr morphs. Environmental Biology of Fishes. doi: 10.1007/s10641-007-9262-1 (in press). ... Curtis, MA, Bèrubè, M. & Stenzel, A. (1995). ...
The main objective of this study was to compare the development of seawater adaptation and change... more The main objective of this study was to compare the development of seawater adaptation and changes in body composition of smolt produced using three different strategies, and to investigate growth during the first month in seawater. Smolt released at different times of the year experience different environmental conditions. In northern Norway there are large annual variations in seawater temperature and photoperiod, and both are known to influence growth rates of salmonids. Three groups of smolts were raised and released 15 April (Group 1, large 1+ smolt), 15 June (Group 2, medium sized 1+ smolt) and 15 September (Group 3, medium sized 0+ smolt). The 0+ out-of-season smolt (group 3) transferred to seawater in September had the best hypo-osmoregulatory ability of the three groups after one month in seawater. These fish also had the highest growth rate (assessed using TGC), and deposited body fat during their first month in seawater. By contrast large 1+ salmon released in April had poorer hypoosmoregulatory ability, failed to grow during their first month in the sea, and appeared to mobilise body fat stores to support metabolism during this critical phase. The medium-sized 1+ smolt, transferred to seawater in June, occupied an intermediate position. Although they appeared to experience some problems with hypo-osmotic regulation, the fish grew during their first month in seawater, and they were able to maintain their concentration of body fat. Our findings conclude that the 0+ out-of-season smolt were not disadvantaged during the early phase of seawater rearing compared to the smolt that were produced by a 'traditional' strategy and transferred to seawater in spring. Indications were that the 0+ smolt fared better following
The relationship between growth rate and fish size is described by the equation log, G,=a-0.4 log... more The relationship between growth rate and fish size is described by the equation log, G,=a-0.4 log, W , where G, is the specific growth rate and W is fish weight. Since the intercept (a) represents the log, G , of a fish unit size, the relationship presents a method allowing comparison of data from experiments involving fish of different sizes. The application of the method is demonstrated by examining the effects ofenvironmental temperature on growth rates of cod, Gadus morhua, and it is suggested that the optimum temperature for growth of cod is 13-1 5" C.
Following feeding, the rate of oxygen consumption of fishes increases to a peak and then slowly d... more Following feeding, the rate of oxygen consumption of fishes increases to a peak and then slowly declines to the pre-feeding level. Many factors have been shown to influence the magnitude and duration of post-prandial oxygen consumption and these include quantity and/or quality of ration and environmental temperature. The effects of the various factors are described and the phenomenon of the post-prandial increase in metabolic rate of fish is discussed in relation to work with other species of animals.
Rates of food consumption are notoriously difficult to measure under field conditions and indirec... more Rates of food consumption are notoriously difficult to measure under field conditions and indirect methods must be used. Using data for cod collected from three different areas (North Sea, Faroes & Balsfjorden), food consumption was estimated from stomach fullness and rates of gastric evacuation. These estimates were then compared with estimates given by analysis of food-growth relationships. Although estimates were ofthe same order of magnitude there were differences. These differences were suggested to be largely due to insufficient knowledge relating to feeding rhythms of wild fish and lack of data regarding the ' costs of reproduction '. Differences between the annual energy budgets of cod from the three stocks are discussed.
When reared for a period of 6 months at a temperature of lo" C Arctic charr, Salvelinus alpinus, ... more When reared for a period of 6 months at a temperature of lo" C Arctic charr, Salvelinus alpinus, increased in weight from 18 g to approximately 135 g. Specific growth rates decreased as the fish increased in size and the relationship between size and growth rate could be described by the equation: where G, is specific growth rate and W is fish weight in grams. Temperature effects upon growth were examined using previously published data. Below the optimum growth temperature, the growth rate of a fish of given size could be predicted using the equation: where T is the rearing temperature. Rates of growth of Arctic charr were as high as those reported for other salmonid species reared under similar conditions. Preliminary results suggested that growth rates of cham may be lower in salt water than in fresh water.
Social interactions and dominance hierarchy effects are important factors governing rates of grow... more Social interactions and dominance hierarchy effects are important factors governing rates of growth of Arctic charr, Sulvelinus alpinus L. The effects of hierarchy were increased as access to food became more restricted, i.e. feeding frequency was reduced, but these effects could not be attributed to direct competition for food since fish were fed to satiation at each feeding period. The results suggest that, whilst some fish on the restricted feeding regime were able to maintain good rates of growth, feeding by the majority of the fish was inhibited by the presence of larger individuals. Due to the importance of these hierarchy effects it was not possible to demonstrate physiological adaptations in fish allowed infrequent access to food.
List of Contributors. Preface. Feed Composition and Analysis (Malcolm Jobling). Feed Types, Manuf... more List of Contributors. Preface. Feed Composition and Analysis (Malcolm Jobling). Feed Types, Manufacture and Ingredients (Malcolm Jobling, Emidio Gomes and Jorges Dias). Techniques for Measuring Feed Intake (Malcolm Jobling, Denis Coves, Borge Damsgard, Henrik R. Kristiansen, Juha Koskela, Thuridur E. Petursdottir, Sunil Kadri and Olafur Gudmundsson). Experimental Design in Feeding Experiments (Kari Ruohonen, Juhani Kettunen and Jonathan King). Gustation and Feeding Behaviour (Charles F. Lamb). Environmental Factors and Feed Intake: Mechanisms and Interactions (Patrick Kestemont and Etienne Baras). Environmental Factors and Feed Intake: Rearing Systems (Marie--Laure Begout Anras, Marilyn Beauchaud, Jon--Erik Juell, Deniks Coves and Jean--Paul Lagardere). Feeding Rhythms (Juan Antonio Madrid, Thierry Boujard and F. Javier Sanchez--Vazquez). Feeding Anticipatory Activity (F. Javier Sanchez--Vazquez and Juan Antonio Madrid). Effects of Feeding Time on Feed Intake and Growth (Valerie Bolliet, Mezian Azzaydi and Thierry Boujard). Effects of Nutritional Factors and Feed Characteristics on Feed Intake (Manuel de la Higuera). Regulation of Food Intake by Neuropeptides and Hormones (Nuria de Pedro and Bjorn Thrandur Bjornsson). Physiological Effects of Feeding (Chris Carter, Dominic Houlihan, Anders Kiessling, Francoise Medale and Malcolm Jobling). Feeding Management (Anders Alanara, Sunil Kadri and Mihalis Paspatis). Nutrient Partitioning and the Influence of Feed Composition on Body Composition (Malcolm Jobling). Glossary of Terms. Index
Jobling, M., 1985. Physiological and social constraints on growth of fish with special reference ... more Jobling, M., 1985. Physiological and social constraints on growth of fish with special reference to Arctic charr, Salvelinus alpinus L. Aquaculture, 44: 83-90. Physiological studies of growth in animals predict that growth rates should decrease with increasing size, but when Arctic charr, Salvelinus alpinus, were reared together in large groups there was often a positive correlation between initial body size and the growth rate of an individual fish. This suggested that social interactions were important determinants of growth rates and, in the absence of the establishment of direct linear hierarchies, it is suggested that growth suppression is the result of short-term bouts of aggression associated with feeding periods leading to reduced food intake by certain fish. Evidence is presented to show that growth suppression can be reduced by increasing the frequency of feeding.
A number of the techniques commonly employed in fish growth and nutrition studies are evaluated a... more A number of the techniques commonly employed in fish growth and nutrition studies are evaluated and limitations imposed by their use are indicated. Total and digestible energy values of dietary formulations should be measured directly and the use of caloric conversion coefficients and assumed digestibility values may lead to serious error. There is considerable misunderstanding relating to the term metabolizable energy and metabolizable energy has been estimated in a number of ways, all of which are unreliable. In view of this, it is suggested that there is a good case to be made for ceasing to use the term.
Feeding rates (food intake per hour) during night and day, feeding modes under different light co... more Feeding rates (food intake per hour) during night and day, feeding modes under different light conditions and the effects of the length of the daily feeding period on growth have been studied in Atlantic salmon, Safmo salar. In autumn ( 12L: 12D), winter (4L:20D) and spring ( 14L: lOD), feeding rates were 3.1 to 7.5 times higher during daylight hours than at night. All food was taken in the water column during light conditions, but juvenile salmon did take food lying on the tank bottom during the hours of darkness. Different feeding regimes (foad offered 3 h per day, during the light period of the day only, and continuously) appereed to have no effect on growth and Parr-smelt transformation.
The workshop in Reykjavik attracted about 100 participants to three days of formal sessions of or... more The workshop in Reykjavik attracted about 100 participants to three days of formal sessions of oral and poster presentations interspersed with informal `round-table' discussions and ad hoc presentations. This special issue is not a proceedings volume in the usual sense, but it contains a cross-section of papers from the range of topics discussed at the workshop. The themes selected for focus at the workshop were: Methods, models and techniques Competition and cannibalism Feeding strategies and tactics Physiological signalling and integration Environmental quality: requirements and influences.
Atlantic cod (Gadus morhua L.) is one of the most important commercial fish species in Norway and... more Atlantic cod (Gadus morhua L.) is one of the most important commercial fish species in Norway and the peak fishing season coincides with spawning from January to April. Live-storage of cod may extend the marketing season for fresh cod products. Cod can be held for up to 12 weeks after capture, and current regulations allow the fish to be held without feeding for four weeks. We investigated whether the response to long-term feed deprivation differed between mature males and females. The fish, caught off Andenes (Norway) in March 2015 using Danish seine, were held without feeding for 82 days, and samples were taken 2, 26, 54 and 82 days after capture. At each sampling, the weights of whole and gutted fish (head on), liver and gonads were measured. Additionally, fillet protein concentrations were analysed. Females lost total weight, gutted weight and liver mass more rapidly than males, but the reduction in gonad mass was significantly higher in males than in females. At termination, after 82 days, fillet protein concentration in males was higher (16.3% ± 0.4) than in females (14.9% ± 0.4). With regard to loss of gutted weight and reduction in muscle protein concentration, the tolerable fasting period of mature spawning Atlantic cod of good biological condition is 54 days, but this can vary depending on upon the initial condition of the fish
The purpose of the current study was to examine seasonal changes in seawater tolerance and growth... more The purpose of the current study was to examine seasonal changes in seawater tolerance and growth performance of anadromous Arctic charr (Salvelinus alpinus L.) held at the same temperature (8°C) during winter and summer. Charr (20-27 cm), previously reared in freshwater under natural photoperiod, were transferred either directly (DT) from freshwater to seawater (35 ppt), from freshwater to brackish water (20 ppt), or were gradually adapted (GT) to seawater over a period of 10 days. Control fish were held in freshwater. Feed intake and osmoregulatory ability were then monitored on three occasions during the following 59 days. Two experiments were carried out, one during winter (December-January) and the other during summer (June-July). In both experiments fish mortality was low. Plasma osmolalities recorded in fish transferred to seawater were within normal ranges, but osmolalities on day 10, were significantly lower in summer (313 mOsm/kg (DT), 328 mOsm/kg (GT)) than in winter (323 mOsm/kg (DT), 352 mOsm/kg (GT)). In winter, feed intake and growth rates were high in fish kept in fresh and brackish water, but charr transferred directly to seawater ate little and lost weight. Fish that were gradually adapted to seawater occupied an intermediate position. During summer the observed differences in feed intake were small and all fish had relatively high growth rates. These results suggest that Arctic charr display seasonal changes in feed intake and growth performance that parallel seasonal changes in hypoosmoregulatory capacity. The ability to survive and hypoosmoregulate in full strength seawater does not, however, seem to be a particularly good indicator of successful seawater adaptation with respect to the ability to display high rates of feed intake and growth. During winter, a gradual transfer to seawater appeared to lead to improved feeding and growth compared to direct transfer.
The effects of long-term moderate exercise on the behaviour and the food intake – growth relation... more The effects of long-term moderate exercise on the behaviour and the food intake – growth relationship of individually marked Arctic charr, Salvelinus alpinus L., were examined. Direct monitoring of food intake of individual fish was carried out using an X-radiographic method. Growth (weight gain) was significantly improved with increasing swimming speed, and a maximum specific growth rate was obtained at a swimming speed of approximately 1.75 body lengths/s. Growth appeared to be suppressed by high levels of aggressive interactions, and an increase in swimming speed caused a marked increase in schooling behaviour, with a concomitant reduction in agonistic activity. The exercising fish did not consume more food than controls, and moderately exercised Arctic charr showed improved growth – food intake ratios at all levels of food intake compared with fish held in standing water. Furthermore, the proportions of nonfeeding fish were significantly reduced at increasing water velocities. Thus, the relationship between food intake and growth may be strongly influenced by agonistic activity, which appears to be most prevalent in fish subjected to low water velocities.
Following feeding, the rate of oxygen consumption of fishes increases to a peak and then slowly d... more Following feeding, the rate of oxygen consumption of fishes increases to a peak and then slowly declines to the pre-feeding level. Many factors have been shown to influence the magnitude and duration of post-prandial oxygen consumption and these include quantity and/or quality of ration and environmental temperature. The effects of the various factors are described and the phenomenon of the post-prandial increase in metabolic rate of fish is discussed in relation to work with other species of animals.
Preface. Fish: an introduction. Environmental links - sensory systems. Foodstuffs and feeding. Va... more Preface. Fish: an introduction. Environmental links - sensory systems. Foodstuffs and feeding. Vascular transport and gaseous exchange: the circulatory and respiratory systems. Physiological integration - nervous and endocrine systems. Digestion and absorption. Osmotic and ionic regulation - water and salt balance. Body form, swimming and movement through the water. Reproduction. Development of eggs and larvae. Recruitment and population fluctuations. Human impacts on aquatic envionments. Index.
... Amundsen, P.-A., Knudsen, R. & Klemetsen, A. (2008). Seasonal and ont... more ... Amundsen, P.-A., Knudsen, R. & Klemetsen, A. (2008). Seasonal and ontogenetic variation in resource use by two sympatric Arctic charr morphs. Environmental Biology of Fishes. doi: 10.1007/s10641-007-9262-1 (in press). ... Curtis, MA, Bèrubè, M. & Stenzel, A. (1995). ...
The main objective of this study was to compare the development of seawater adaptation and change... more The main objective of this study was to compare the development of seawater adaptation and changes in body composition of smolt produced using three different strategies, and to investigate growth during the first month in seawater. Smolt released at different times of the year experience different environmental conditions. In northern Norway there are large annual variations in seawater temperature and photoperiod, and both are known to influence growth rates of salmonids. Three groups of smolts were raised and released 15 April (Group 1, large 1+ smolt), 15 June (Group 2, medium sized 1+ smolt) and 15 September (Group 3, medium sized 0+ smolt). The 0+ out-of-season smolt (group 3) transferred to seawater in September had the best hypo-osmoregulatory ability of the three groups after one month in seawater. These fish also had the highest growth rate (assessed using TGC), and deposited body fat during their first month in seawater. By contrast large 1+ salmon released in April had poorer hypoosmoregulatory ability, failed to grow during their first month in the sea, and appeared to mobilise body fat stores to support metabolism during this critical phase. The medium-sized 1+ smolt, transferred to seawater in June, occupied an intermediate position. Although they appeared to experience some problems with hypo-osmotic regulation, the fish grew during their first month in seawater, and they were able to maintain their concentration of body fat. Our findings conclude that the 0+ out-of-season smolt were not disadvantaged during the early phase of seawater rearing compared to the smolt that were produced by a 'traditional' strategy and transferred to seawater in spring. Indications were that the 0+ smolt fared better following
The relationship between growth rate and fish size is described by the equation log, G,=a-0.4 log... more The relationship between growth rate and fish size is described by the equation log, G,=a-0.4 log, W , where G, is the specific growth rate and W is fish weight. Since the intercept (a) represents the log, G , of a fish unit size, the relationship presents a method allowing comparison of data from experiments involving fish of different sizes. The application of the method is demonstrated by examining the effects ofenvironmental temperature on growth rates of cod, Gadus morhua, and it is suggested that the optimum temperature for growth of cod is 13-1 5" C.
Following feeding, the rate of oxygen consumption of fishes increases to a peak and then slowly d... more Following feeding, the rate of oxygen consumption of fishes increases to a peak and then slowly declines to the pre-feeding level. Many factors have been shown to influence the magnitude and duration of post-prandial oxygen consumption and these include quantity and/or quality of ration and environmental temperature. The effects of the various factors are described and the phenomenon of the post-prandial increase in metabolic rate of fish is discussed in relation to work with other species of animals.
Rates of food consumption are notoriously difficult to measure under field conditions and indirec... more Rates of food consumption are notoriously difficult to measure under field conditions and indirect methods must be used. Using data for cod collected from three different areas (North Sea, Faroes & Balsfjorden), food consumption was estimated from stomach fullness and rates of gastric evacuation. These estimates were then compared with estimates given by analysis of food-growth relationships. Although estimates were ofthe same order of magnitude there were differences. These differences were suggested to be largely due to insufficient knowledge relating to feeding rhythms of wild fish and lack of data regarding the ' costs of reproduction '. Differences between the annual energy budgets of cod from the three stocks are discussed.
When reared for a period of 6 months at a temperature of lo" C Arctic charr, Salvelinus alpinus, ... more When reared for a period of 6 months at a temperature of lo" C Arctic charr, Salvelinus alpinus, increased in weight from 18 g to approximately 135 g. Specific growth rates decreased as the fish increased in size and the relationship between size and growth rate could be described by the equation: where G, is specific growth rate and W is fish weight in grams. Temperature effects upon growth were examined using previously published data. Below the optimum growth temperature, the growth rate of a fish of given size could be predicted using the equation: where T is the rearing temperature. Rates of growth of Arctic charr were as high as those reported for other salmonid species reared under similar conditions. Preliminary results suggested that growth rates of cham may be lower in salt water than in fresh water.
Social interactions and dominance hierarchy effects are important factors governing rates of grow... more Social interactions and dominance hierarchy effects are important factors governing rates of growth of Arctic charr, Sulvelinus alpinus L. The effects of hierarchy were increased as access to food became more restricted, i.e. feeding frequency was reduced, but these effects could not be attributed to direct competition for food since fish were fed to satiation at each feeding period. The results suggest that, whilst some fish on the restricted feeding regime were able to maintain good rates of growth, feeding by the majority of the fish was inhibited by the presence of larger individuals. Due to the importance of these hierarchy effects it was not possible to demonstrate physiological adaptations in fish allowed infrequent access to food.
List of Contributors. Preface. Feed Composition and Analysis (Malcolm Jobling). Feed Types, Manuf... more List of Contributors. Preface. Feed Composition and Analysis (Malcolm Jobling). Feed Types, Manufacture and Ingredients (Malcolm Jobling, Emidio Gomes and Jorges Dias). Techniques for Measuring Feed Intake (Malcolm Jobling, Denis Coves, Borge Damsgard, Henrik R. Kristiansen, Juha Koskela, Thuridur E. Petursdottir, Sunil Kadri and Olafur Gudmundsson). Experimental Design in Feeding Experiments (Kari Ruohonen, Juhani Kettunen and Jonathan King). Gustation and Feeding Behaviour (Charles F. Lamb). Environmental Factors and Feed Intake: Mechanisms and Interactions (Patrick Kestemont and Etienne Baras). Environmental Factors and Feed Intake: Rearing Systems (Marie--Laure Begout Anras, Marilyn Beauchaud, Jon--Erik Juell, Deniks Coves and Jean--Paul Lagardere). Feeding Rhythms (Juan Antonio Madrid, Thierry Boujard and F. Javier Sanchez--Vazquez). Feeding Anticipatory Activity (F. Javier Sanchez--Vazquez and Juan Antonio Madrid). Effects of Feeding Time on Feed Intake and Growth (Valerie Bolliet, Mezian Azzaydi and Thierry Boujard). Effects of Nutritional Factors and Feed Characteristics on Feed Intake (Manuel de la Higuera). Regulation of Food Intake by Neuropeptides and Hormones (Nuria de Pedro and Bjorn Thrandur Bjornsson). Physiological Effects of Feeding (Chris Carter, Dominic Houlihan, Anders Kiessling, Francoise Medale and Malcolm Jobling). Feeding Management (Anders Alanara, Sunil Kadri and Mihalis Paspatis). Nutrient Partitioning and the Influence of Feed Composition on Body Composition (Malcolm Jobling). Glossary of Terms. Index
Jobling, M., 1985. Physiological and social constraints on growth of fish with special reference ... more Jobling, M., 1985. Physiological and social constraints on growth of fish with special reference to Arctic charr, Salvelinus alpinus L. Aquaculture, 44: 83-90. Physiological studies of growth in animals predict that growth rates should decrease with increasing size, but when Arctic charr, Salvelinus alpinus, were reared together in large groups there was often a positive correlation between initial body size and the growth rate of an individual fish. This suggested that social interactions were important determinants of growth rates and, in the absence of the establishment of direct linear hierarchies, it is suggested that growth suppression is the result of short-term bouts of aggression associated with feeding periods leading to reduced food intake by certain fish. Evidence is presented to show that growth suppression can be reduced by increasing the frequency of feeding.
A number of the techniques commonly employed in fish growth and nutrition studies are evaluated a... more A number of the techniques commonly employed in fish growth and nutrition studies are evaluated and limitations imposed by their use are indicated. Total and digestible energy values of dietary formulations should be measured directly and the use of caloric conversion coefficients and assumed digestibility values may lead to serious error. There is considerable misunderstanding relating to the term metabolizable energy and metabolizable energy has been estimated in a number of ways, all of which are unreliable. In view of this, it is suggested that there is a good case to be made for ceasing to use the term.
Feeding rates (food intake per hour) during night and day, feeding modes under different light co... more Feeding rates (food intake per hour) during night and day, feeding modes under different light conditions and the effects of the length of the daily feeding period on growth have been studied in Atlantic salmon, Safmo salar. In autumn ( 12L: 12D), winter (4L:20D) and spring ( 14L: lOD), feeding rates were 3.1 to 7.5 times higher during daylight hours than at night. All food was taken in the water column during light conditions, but juvenile salmon did take food lying on the tank bottom during the hours of darkness. Different feeding regimes (foad offered 3 h per day, during the light period of the day only, and continuously) appereed to have no effect on growth and Parr-smelt transformation.
The workshop in Reykjavik attracted about 100 participants to three days of formal sessions of or... more The workshop in Reykjavik attracted about 100 participants to three days of formal sessions of oral and poster presentations interspersed with informal `round-table' discussions and ad hoc presentations. This special issue is not a proceedings volume in the usual sense, but it contains a cross-section of papers from the range of topics discussed at the workshop. The themes selected for focus at the workshop were: Methods, models and techniques Competition and cannibalism Feeding strategies and tactics Physiological signalling and integration Environmental quality: requirements and influences.
Uploads
Papers by Malcolm Jobling