Loss of muscle fibres in a landlocked dwarf Atlantic salmon population

Growth of fast myotomal muscle in teleosts involves the continuous production of muscle fibres until some genetically pre-determined length. The dwarf landlocked (Bleke) population of Atlantic salmon (Salmo salar L.) from Byglands-fjord, Southern Norway mature at about 25 cm fork length and reach a maximum size of only 30 cm in the wild. The maximum diameter (D(max)) of fast muscle fibres in 4-year-old Bleke salmon (25-28 cm fork length) was 118 microm and not significantly different from that found in immature migratory salmon of a similar size. In contrast no evidence for active fibre recruitment was found in the Bleke salmon, such that the maximum fibre number, FN(max), was only 21-30% of that reported in typical farmed and wild migratory populations, respectively. We hypothesise that, once established, the physiological consequences of the dwarf condition led to rapid selection for reduced fibre number, possibly to reduce the maintenance costs associated with ionic homeostasis.     

Muscle growth in juvenile Atlantic salmon as influenced by temperature in the egg and yolk sac stages and diet protein level

Atlantic salmon Salmo salar eggs derived from a single family were incubated at two different water temperature regimes, with a mean temperature between fertilization and first feeding differing between 6 and 10° C (HT) and 2–6° C (LT). From first feed the fry were kept under the same rearing conditions and fed either high (50%) or low (45%) protein diet level of equivalent energy content until smoltification. All treatments were carried out in duplicate tanks. At first feeding the groups were similar in mass, but thereafter the HT‐fish were heavier and longer compared to the LT‐fish throughout the experiment. The groups fed the high protein diet were significantly heavier and longer compared with the corresponding low protein diet. A strong positive relationship was observed between L_F and total white muscle cross‐sectional area (CSA), white muscle fibre diameter and fibre number. There were also equivalent relationships with body mass. There were no significant differences in CSA, the mean diameter or the number of white muscle fibres per CSA between groups at first feed. Muscle fibre number and CSA increased in all groups during the experiment, whereas fibre diameter reached a plateau when the fish reached > 9 cm L_F. There were only minor effects of pre‐hatch and yolk sac stage temperature on CSA and fibre number per CSA during the juvenile stage. In short periods the LT‐group had larger CSA and higher fibre number than the HT‐groups, but this differences had disappeared by the end of the juvenile stage. No differences in mean fibre diameter were found between groups, except at the time of smoltification. When the fish approached smoltification a decrease in mean fibre diameter and an increase in muscle fibres <25 µm was seen and taken as an indication of recruitment of new fibres (hyperplasia). Only minor differences in CSA, fibre number or fibre diameter was observed between high and low protein diet groups.     

Plasticity in response to feed availability: Does feeding regime influence the relative growth performance of domesticated,wild and hybrid Atlantic salmon Salmo salar parr?

Growth of farmed, wild and F1 hybrid Atlantic salmon parr Salmo salar was investigated under three contrasting feeding regimes in order to understand how varying levels of food availability affects relative growth. Treatments consisted of standard hatchery feeding (ad libitum), access to feed for 4 h every day, and access to feed for 24 h on three alternate days weekly. Mortality was low in all treatments, and food availability had no effect on survival of all groups. The offspring of farmed S. salar significantly outgrew the wild S. salar, while hybrids displayed intermediate growth. Furthermore, the relative growth differences between the farmed and wild S. salar did not change across feeding treatments, indicating a similar plasticity in response to feed availability. Although undertaken in a hatchery setting, these results suggest that food availability may not be the sole driver behind the observed reduced growth differences found between farmed and wild fishes under natural conditions.     

Farmed Atlantic salmon Salmo salar L. parr may reduce early survival of wild fish

The study examined the density‐mediated effects on growth, survival and dispersal of wild and farmed Atlantic salmon Salmo salar offspring in the period immediately following emergence, using a substitutive design. In small confined stream channels, wild parr coexisting with farmed parr had a significantly poorer survival, than wild parr alone. Density did not affect this relationship. In larger unconfined stream channels, wild parr coexisting with farmed parr entered a downstream trap in higher numbers than wild parr in allopatry. The results suggests that during the earliest life stages, farmed S. salar can outcompete wild S. salar, resulting in a reduced survival of wild S. salar.     

Effect of ration size and feeding frequency on growth, size distribution and survival of juvenile clownfish, Amphiprion percula

This study describes the growth of juvenile clownfish, Amphiprion percula Lacépède 1802, fed with an artificial diet at six ration sizes of 2, 4, 6, 8, 10 and 12% of body mass per day (BM day^?1) each at a feeding frequency of once, twice and three times per day. The effect of ration size on growth depended on the feeding frequency. In fish fed once a day growth did not improve above a ration size of 8% BM day^?1. At two feedings per day fish required a ration size of at least 6% BM day^?1 to achieve good growth, and fish fed three times per day grew at similar rates above a ration size of 4% BM day^?1. A model to estimate the combined effect of ration size and feeding frequency is presented. The results lead to the suggestion of a simple length‐based feeding regimen that could be tested in future studies on this species or adapted for use in other species.     

Sperm traits in farmed and wild Atlantic salmon Salmo salar

Differences in sperm metabolism and morphology between wild and non‐local farmed Atlantic salmon Salmo salar were assessed by measuring metabolic enzyme activities and length of sperm flagella. No differences were observed between wild and farmed S. salar sperm with regards to cell counts or any of the biochemical variables assessed. Flagella of sperm cells were significantly longer in wild than farmed S. salar; however, this did not result in higher energy levels or different fertilization rates.     

Vertebral deformities in interspecific diploid and triploid salmonid hybrids

Vertebral deformities in salmonid interspecific hybrids, some of which were triploidised, were assessed across three separate year classes during the freshwater life stage. Initially, eggs from a farmed Atlantic salmon Salmo salar were crossed with the sperm from a S. salar, arctic char Salvelinus alpinus or brown trout Salmo trutta. For S. salar × S. trutta, half the eggs were triploidised. In a second- and third-year class, the eggs from a farmed S. salar were crossed with the sperm from either a S. salar or a S. trutta, and half of each group was triploidised. In the two initial-year classes, all hybrids were larger than the S. salar controls, and triploid S. salar × S. trutta were larger than diploid counterparts. In the third-year class, the S. salar × S. trutta were smaller than the S. salar, in contrast to the initial 2 year classes, although the triploid hybrids were still larger than the diploids. In the third-year class, a high degree of spontaneous triploidy was also observed in the putative diploid groups (between 16 and 39%). Vertebral deformities were consistently higher in pressure-shocked triploids than diploids, irrespective of hybridisation, but there was no consistent effect of hybridisation among experiments. Although this study was not able to explain the contrasting results for vertebral deformities between year classes, triploid S. salar × S. trutta can demonstrate impressive freshwater growth that could be of interest for future farming programmes.     

Growth and muscle cellularity of diploid and triploid Atlantic cod (Gadus morhua Linnaeus, 1758) larvae

The aim of this study was to compare somatic growth and muscle fibre development in diploid and triploid siblings of Atlantic cod (Gadus morhua Linnaeus, 1758) during the larval stage. Newly hatched larvae were transferred into 200‐L tanks, three tanks per ploidy group (70 larvae L^?1, continuous light, gradually increasing seawater temperature 7–11°C and flow rates 50–117 L h^?1). Larvae were fed rotifers from 2 to 22 days post hatch (dph), Artemia 19–31 dph and weaned onto a microparticulate diet from 26 dph until the end of the experiment. Measurements of growth (dry weight, standard length) and muscle cellullarity were taken at intervals between 1 and 44 dph. Ploidy groups showed a similar performance throughout the trial, although a marked stagnation in growth was observed for triploids during the weaning from Artemia onto dry feed. Overall, diploid and triploid cod larvae showed a similar development in muscle fibre growth pattern during the experimental period. For both groups, the total number of fast muscle fibres showed a 10‐fold increase (from 384 to 3462), whereas the diameter of fast fibre increased from 8.9 to 13.3 μm (mean number from all treatments). Thus, a temporary but significant effect of triploidy on fast muscle fibre growth pattern was observed in 19 dph larvae in terms of fibre size and number, with triploids showing larger mean fast fibre diameter (11.62 ± 0.63 vs. 10.05 ± 0.34) and a lower number of fibres with a diameter <5 μm than their diploid siblings. Thus, this was found to be related to larvae size and to the differences in total fast fibre cross sectional areas rather than to ploidy status. Overall, our results suggest possible deficiencies in nutrients’ digestion and absorption of triploid cod larvae particularly during the transitional period from live food to inert diets.     

Change in food ingestion induces rapid shifts in the diversity of microbiota associated with cutaneous mucus of Atlantic salmon Salmo salar

To test the hypothesis that a switch in diet might cause changes in the abundance and composition of mucous‐dwelling microorganisms, a short‐term experiment was conducted with Atlantic salmon Salmo salar. Fish were fed on three different diets: pelleted S. salar feed, macroinvertebrates or pellets supplemented with an antibiotic. A fourth group of fish was deprived of food throughout the trial. Seven days after manipulating diets, significant differences were found in microbial density and community composition (quantified by different morphologically distinct colonies), particularly between fed and unfed animals. Moreover, food deprivation caused a rapid decrease in the number of epidermal mucous cells of the lateral skin, which may indicate a decrease in mucous secretion and explain differences in the diversity of mucous‐dwelling microbiota observed in the fish. This is the first report of an effect of feeding regime on the abundance of microbial communities associated with cutaneous mucus of fishes.     

Environmental change influences the life history of salmon Salmo salar in the North Atlantic Ocean

Annual mean total length (L_T) of wild one‐sea‐winter (1SW) Atlantic salmon Salmo salar of the Norwegian River Imsa decreased from 63 to 54 cm with a corresponding decrease in condition factor (K) for cohorts migrating to sea from 1976 to 2010. The reduction in L_T is associated with a 40% decline in mean individual mass, from 2 to 1·2 kg. Hatchery fish reared from parental fish of the same population exhibited similar changes from 1981 onwards. The decrease in L_T correlated negatively with near‐surface temperatures in the eastern Norwegian Sea, thought to be the main feeding area of the present stock. Furthermore, S. salar exhibited significant variations in the proportion of cohorts attaining maturity after only one winter in the ocean. The proportion of S. salar spawning as 1SW fish was lower both in the 1970s and after 2000 than in the 1980s and 1990s associated with a gradual decline in post‐smolt growth and smaller amounts of reserve energy in the fish. In wild S. salar, there was a positive association between post‐smolt growth and the sea survival back to the River Imsa for spawning. In addition, among smolt year‐classes, there were significant positive correlations between wild and hatchery S. salar in L_T, K and age at maturity. The present changes may be caused by ecosystem changes following the collapse and rebuilding of the pelagic fish abundance in the North Atlantic Ocean, a gradual decrease in zooplankton abundance and climate change with increasing surface temperature in the Norwegian Sea. Thus, the observed variation in the life‐history traits of S. salar appears primarily associated with major changes in the pelagic food web in the ocean.     

A primary phosphorus‐deficient skeletal phenotype in juvenile Atlantic salmon Salmo salar: the uncoupling of bone formation and mineralization

To understand the effect of low dietary phosphorus (P) intake on the vertebral column of Atlantic salmon Salmo salar, a primary P deficiency was induced in post‐smolts. The dietary P provision was reduced by 50% for a period of 10 weeks under controlled conditions. The animal's skeleton was subsequently analysed by radiology, histological examination, histochemical detection of minerals in bones and scales and chemical mineral analysis. This is the first account of how a primary P deficiency affects the skeleton in S. salar at the cellular and at the micro‐anatomical level. Animals that received the P‐deficient diet displayed known signs of P deficiency including reduced growth and soft, pliable opercula. Bone and scale mineral content decreased by c. 50%. On radiographs, vertebral bodies appear small, undersized and with enlarged intervertebral spaces. Contrary to the X‐ray‐based diagnosis, the histological examination revealed that vertebral bodies had a regular size and regular internal bone structures; intervertebral spaces were not enlarged. Bone matrix formation was continuous and uninterrupted, albeit without traces of mineralization. Likewise, scale growth continues with regular annuli formation, but new scale matrix remains without minerals. The 10 week long experiment generated a homogeneous osteomalacia of vertebral bodies without apparent induction of skeletal malformations. The experiment shows that bone formation and bone mineralization are, to a large degree, independent processes in the fish examined. Therefore, a deficit in mineralization must not be the only cause of the alterations of the vertebral bone structure observed in farmed S. salar. It is discussed how the observed uncoupling of bone formation and mineralization helps to better diagnose, understand and prevent P deficiency‐related malformations in farmed S. salar.     

Growth dynamics of white myotomal muscle fibres in the bluntnose minnow, Pimephales notatus Rafinesque, and comparison with rainbow trout, Salmo gairdneri Richardson

The dynamics of increase of the predominant white muscle fibres of the myotomal bulk in bluntnose minnow, Pimephales notatus , ranging from 2.0 to 9.1 cm f.l. have been analysed by examination of modal progression of fibre diameter frequency classes in fish fed to satiation and growing at different rates at 15, 25 or 30°C. Recruitment of new fibres appeared to contribute little to increase in muscle bulk above 4 cm f.l. , and nothing beyond 6 cm. The dominant means of increase was increase in fibre diameter. The limiting fibre diameter seemed to be 120 μ. These dynamics, which result in an approximately 1: 1 ratio between mean fibre diameter and f.l. , are in contrast to those of the myotomal white muscle of rainbow trout, Salmo gairdneri , in which, regardless of differences in somatic growth produced by temperature, ration size or growth hormone administration, mean fibre diameter does not exceed that in bluntnose minnow until trout exceed 30 cm f.l. In trout there is, moreover, input of new fibres up to approximately 50 cm f.l. , when subsequent growth, as in the minnow, is by means of fibre diameter increase. The bluntnose minnow is a small, slow growing species; the rainbow trout is a large, fast growing species. The discussion links these facts with the observed differences in fibre growth dynamics in relation to a hypothesis of interspecific differences in fish growth capability.     

Influence of sea temperature and initial marine feeding on survival of Atlantic salmon Salmo salar post-smolts from the Rivers Orkla and Hals, Norway

The abundance of returning adult Atlantic salmon Salmo salar, in the River Orkla in mid‐norway (1 sea‐winter, SW, fish) and River Hals in north Norway (1–3 SW fish), was tested against the early marine feeding and the seawater temperature experienced by their corresponding year classes of post‐smolts immediately after entry into the Trondheimsfjord (Orkla smolts, 22 years of data) and Altafjord (Hals smolts, 17 years of data). In both river–fjord systems, there was a significant positive correlation between the abundance of returning S. salar and the mean seawater temperature at the time of smolts descending to the sea. The number of 1SW fish reported caught in River Orkla was positively correlated to the proportion of fish larvae in the post‐smolt stomachs in Trondheimsfjord. The abundance of returning S.salar was, however, neither correlated to forage ratio (R_F) nor other prey groups in post‐smolt stomachs in the two fjord systems. In the Altafjord, the post‐smolts fed mainly on pelagic fish larva (70–98%) and had a stable R_F (0·009–0·023) over the 6 years analysed. In the Trondheimsfjord, however, there was a higher variation in R_F (0·003–0·036), and pelagic fish larvae were dominant prey in only two (50 and 91%) of the 8 years analysed. These 2 years also showed the highest return rates of S. salar in River Orkla. These results demonstrate that the thermal conditions experienced by post‐smolts during their early sea migration may be crucial for the subsequent return rate of adults after 1–3 years at sea. Pelagic marine fish larvae seem to be the preferred initial prey for S. salar post‐smolts. As the annual variation in abundance of fish larvae is related to seawater temperature, it is proposed that seawater temperature at sea entry and the subsequent abundance of returning adult S. salar may be indirectly linked through variation in annual availability of pelagic fish larvae or other suitable food items in the early post‐smolt phase.     

Effects of various environmental conditions on growth and reproduction of the sea hareAplysia oculifera (Adams and Reeve, 1850)

We studied the influences of food type, food quantity, water currents, starvation and light on growth and reproduction of the sea hareaplysia oculifera (Adams and Reeve, 1850) under laboratory conditions. Out of five species of algae served as food,Enteromorpha intestinalis promoted the fastest growth ofA. oculifera, Ulva spp. slower growth,Cladophora sp. allowed maintenance spp. slower growth,Cladophora sp. allowed maintenance of steady body mass, and the brown algaeColpomenia sp. andPadina pavonia were rejected by the sea hares. When sea hares were exposed to four levels of water currents, growth rates decreased as water currents increased. Sea hares fed on 50% ration grew slower than those fed on 100% ration (ad libitum). During 10 days of starvation sea hares lost weight, but when subsequently fed 100% ration they recovered and grew at a rate similar to those fed continuously with 100% ration. Under shade and under natural sunlight sea hares grew at the same rates. Whenever growth rates decreased, sea hares began to spawn at a smaller body size.A. oculifera demonstrated physiological plasticity that adapted them to varied and unpredictable environmental conditions. At different conditions of food availability they applied different tactics of resource allocation between growth and reproduction.     

The effect of stocking with 0+ year age‐class Atlantic salmon Salmo salar fry: a case study from the River Bush,Northern Ireland

An enhancement programme based on stocking 0+ year age‐class Atlantic salmon Salmo salar, conducted in the River Bush, Northern Ireland, U.K. over the period 1996–2005, was reviewed with reference to the performance and biological characteristics of wild fish. Wild ova to 0+ year fry (summer) survival was c. 8% with subsequent wild 0+ year fry‐to‐smolt survival c. 9%. Stocked unfed 0+ year juveniles gave c. 1% survival to smolt whilst fed 0+ year S. salar stocked in late summer exhibited survival at c. 5%. Stocking with unfed and fed fry contributed to increased smolt production and helped attain local management objectives between 2001 and 2005. Significant differences in biological characteristics were observed between wild and stocked‐origin fish. Wild‐smolt cohorts were dominated by 2+ year age‐class fish on the River Bush whilst smolts originating from fed fry mostly comprised younger 1+ year individuals. The mean mass of 1+ year smolts derived from stocked fed fry was significantly lower than that of wild 1+ year smolts, although these differences were not evident between older age classes. Differences in run timing between wild smolts and smolts derived from stocked fry were also apparent with the stocked‐origin fish tending to run earlier than wild fish. Although the stocking exercise was useful in terms of maximizing freshwater production, concerns over the quality of stocked‐origin recruits and the long term consequences for productivity are highlighted.     

Long‐term effects of photoperiod,temperature and their interaction on growth,gill Na+, K+‐ATPase activity,seawater tolerance and plasma growth‐hormone levels in Atlantic salmon Salmo salar

This study was undertaken to examine the long‐term effects of photoperiod, temperature and their interaction on growth, gill Na⁺,K⁺‐ATPase (NKA) activity, seawater tolerance and plasma growth‐hormone levels in Atlantic salmon Salmo salar pre‐smolts and smolts. The fish (mean ± s.e . initial body mass = 15·9 ± 0·4 g) were reared on two photoperiods (continuous light, LL, and simulated natural photoperiod, LDN, 60° 25′ N) and two temperatures (8·3 and 12·7° C) from June to May of the following year. Mean body mass was affected by photoperiod, temperature and their interactions. Both temperature groups on LL developed peak levels in gill NKA activity from October to November, 4–5 months prior to the natural season for the parr–smolt transformation. Fish at 12° C showed peak levels in NKA activity 4–6 weeks before the fish at 8° C. Fish in all four experimental groups showed maximum NKA activity within a similar size range (113–162 g). The present findings further indicate that smoltification in S. salar is to some extent driven by size, and that S. salar will develop smolt characteristics, e.g. a marked increase in NKA activity, within a similar size range. Faster‐growing S. salar will, thus, reach this size threshold at a relatively younger age.     

The influence of aquaculture unit proximity on the pattern of Lepeophtheirus salmonis infection of anadromous Salmo trutta populations on the isle of Skye,Scotland

A total of 230 anadromous Salmo trutta (brown trout) were sampled in five sheltered coastal fjords (or sea lochs) on the Isle of Skye, Scotland, U.K., in 2016 at varying distances from active Atlantic salmon Salmo salar farms. Statistical models were developed to investigate potential correlations between salmon lice Lepeophtheirus salmonis burdens on S. trutta hosts and their proximity to S. salar farm cages. Significant correlations were found between lice burdens and fish fork length and proximity to the nearest S. salar farm. The probability of the presence of L. salmonis on fish hosts increased with fish host size and with distance from the nearest S. salar farm, but total lice burdens were highest in fish sampled near S. salar farms and decreased with distance. The proportion of different life‐cycle stages of L. salmonis were also dependent on S. salar farm proximity, with higher juvenile lice numbers recorded at sites near S. salar farm cages. These results highlight the complexity of the relationship between S. trutta and L. salmonis infections on wild fish and emphasize the requirement of further research to quantify these effects to better inform conservation and management strategies, particularly in areas of active S. salar farm facilities.     

Chronic consumption of farmed salmon containing persistent organic pollutants causes insulin resistance and obesity in mice

Background

Dietary interventions are critical in the prevention of metabolic diseases. Yet, the effects of fatty fish consumption on type 2 diabetes remain unclear. The aim of this study was to investigate whether a diet containing farmed salmon prevents or contributes to insulin resistance in mice.

Methodology/Principal Findings

Adult male C57BL/6J mice were fed control diet (C), a very high-fat diet without or with farmed Atlantic salmon fillet (VHF and VHF/S, respectively), and Western diet without or with farmed Atlantic salmon fillet (WD and WD/S, respectively). Other mice were fed VHF containing farmed salmon fillet with reduced concentrations of persistent organic pollutants (VHF/S_-POPs). We assessed body weight gain, fat mass, insulin sensitivity, glucose tolerance, ex vivo muscle glucose uptake, performed histology and immunohistochemistry analysis, and investigated gene and protein expression. In comparison with animals fed VHF and WD, consumption of both VHF/S and WD/S exaggerated insulin resistance, visceral obesity, and glucose intolerance. In addition, the ability of insulin to stimulate Akt phosphorylation and muscle glucose uptake was impaired in mice fed farmed salmon. Relative to VHF/S-fed mice, animals fed VHF/S_-POPs had less body burdens of POPs, accumulated less visceral fat, and had reduced mRNA levels of TNFα as well as macrophage infiltration in adipose tissue. VHF/S_-POPs-fed mice further exhibited better insulin sensitivity and glucose tolerance than mice fed VHF/S.

Conclusions/Significance

Our data indicate that intake of farmed salmon fillet contributes to several metabolic disorders linked to type 2 diabetes and obesity, and suggest a role of POPs in these deleterious effects. Overall, these findings may participate to improve nutritional strategies for the prevention and therapy of insulin resistance.     

Experimental investigation of the effects of temperature and feeding regime on scale growth in Atlantic salmon Salmo salar post-smolts

Salmo salar post-smolts were reared in seawater under controlled laboratory conditions for 12 weeks. The fish were exposed to three constant temperature treatments (15, 10.5 and 6°C) and four feeding treatments (constant feeding, food withheld for 7 days, food withheld for 14 days and food withheld intermittently for four periods of 7 days). Scale growth was proportional to fish growth across all treatments, justifying the use of scale measurements as a proxy for growth during the early marine phase. The rate of circuli deposition was dependant on temperature and feeding regime and was generally proportional to fish growth but with some decoupling of the relationship at 15°C. Deposition rates varied from 4.8 days per circulus at 15°C (constant feeding) to 15.1 days per circulus at 6°C (interrupted feeding). Cumulative degree day (^°D) was a better predictor of circuli number than age, although the rate of circuli deposition ^°D⁻¹ was significantly lower at 6°C compared with 15 and 10.5°C. Inter-circuli distances were highly variable and did not reflect growth rate; tightly packed circuli occurred during periods without food when growth was depressed, but also during periods of rapid growth at 15°C. The results further current understanding of scale growth properties and can inform investigations of declining marine growth in S. salar based on interpretations of scale growth patterns.     

Effect of alimentary deprivation on quantitative and time characteristics of nutrition of the goldfish in norm and under action of adrenalin

Effects of the intraperitoneally administered adrenalin (0.14 mg/kg) on volume and time characteristics (duration) of the individual, grouped, and summarized nutrition was studied in goldfish Carassius auratus (L.) previously kept on normal and restricted (for 10 and 15 days) ration. The fish on restricted ration demonstrated the two-phase alimentary response to the adrenalin injection similar with that in normally feeding fish: a decrease in volume and in the grouped and summarized duration of nutrition in the first phase of the hormone action and an increase-in the second phase; however, the value of the effect in the first phase was lower, while in the second phase-higher than in the fish that obtained before the experiment the sufficient amount of food. Duration of individual nutrition increased in all fish groups, including the control one, the maximal increase being observed in goldfish submitted to alimentary deprivation. The content of glycogen in hepatopancreas of the normally fed goldfish by the end of experiment exceeded that in fish restricted in nutrition 4.5–6 times. The obtained results confirm the suggestion that a decrease of level of reserved substances in the body leads to reduction of susceptibility of fish to the stress hormoneadrenalin and, hence, to a change of the value of its effects on the goldfish food-procuring activity, with preservation of dynamics of parameters.