Experimental evidence for juvenile Chinook salmon, Oncorhynchus tschawytscha Walbaum, orientation at night and in sunlight after a 7° change in latitude

A group of eighteen young chinook salmon, Oncorhynchus tschawytscha Walbaum, trained to orientate in the direction 270°, showed a unimodal orientation of 264° and a mean bimodal axis of orientation of 258°/078° (magnetic) within confidence limits of 218°←→285°: 038°←→105° when tested under controlled conditions in Auckland. Two years later 12 of these fish were transferred to a new test arena in Christchurch, south (7° latitude) of the original location, for individual re-testing at night in a light-proof room and also in sunlight; in the absence of ‘local’ Auckland cues/clues. These fish had been kept in artificial light but six fish were exposed to sunlight in Auckland 2 weeks before moving to Christchurch. At night each fish showed consistent non-random orientation and nine out of 10 fish showed a mean bimodal orientation that fell within the confidence limit established in Auckland; the mean of means axis of orientation for 10 fish was 270°/090°. In sunlight each individual fish showed a consistent, non-random mean bimodal orientation that fell outside the confidence limits established in Auckland and, at night, in Christchurch. The mean of means axis of orientation was 001°/181° (magnetic); the map direction from Christchurch to Auckland is 15°. The principal findings in this study were: (a) ‘Local’ Auckland cues were not essential for location of the learnt direction. (b) A non-visual ‘universal’ cue was used as a reference for location of direction at night. (c) Daylight orientation was influenced by anisotropic radiance, even though the sun image was obscured by the test arena cover. (d) The concentration of data at midday and sunset in artificial light and perhaps at midnight, may indicate the presence of a non-visual zeitgeber. (e) A correlation between time and direction, in light and in darkness, which by implication involves a co-ordination process. (f) The fish under test apparently imprinted on some aspect of the sun (in Auckland) within a 2-day period at the age of 2 years. (g) Displacement, by 7° in latitude, may have been detected by both visual and non-visual means. It is proposed that directional information from the geomagnetic field and the anisotropic radiance of sunlight provides a complementary cross reference which would be sufficient for positional orientation, in relation to some fixed landmark, within coastal waters; but would not suffice for spatial orientation in mid-ocean.     

Experimental evidence for geomagnetic orientation in juvenile salmon, Oncorhynchus tschawytscha Walbaum

Juvenile chinook salmon, Oncorhynchus tschawytscha , kept under artificial light in a rectangular holding tank aligned east/west for 18 months, showed a preferred temporal and directional orientation of 270° with respect to water flow and the source of food.
Individual fish transferred from the holding/training tank to an unfamiliar circular test arena in another room devoid of local directional cues showed a mean of means preferred unimodal orientation of 264°.
Controlled re-introduction of individual stimuli revealed a hierarchy of orientation cues; one of these was a response to magnetism. A 90° clockwise shift in the horizontal component of the earth's magnetic field was followed by a significant change in the mean of means axial orientation, for the fish under test, from 258°/78° to 354°/174°. After restoration of the normal magnetic field the mean of means axial orientation reverted to 274°/94°.     

Effects of anaesthesia on the chemosensory behaviour of Pacific salmon

As Lewis et al . reported in J. Fish Biol. 26 , 355–358 (1985) that the anaesthetic tricaine methanosulphate (MS 222) damaged the olfactory epithelium of channel catfish, two assays were used to determine whether MS 222 or 2-phenoxyethanol (an alternative anaesthetic) influenced subsequent olfaction-mediated behaviour. Tests revealed that the homing of adult chinook salmon, Oncorhynchus tshawytscha , and the l-serine avoidance response of juvenile coho salmon, O. kisutch , were not altered by anaesthesia.     

Cardiovascular responses of Chinook salmon (Oncorhynchus tshawytscha) during rapid anaesthetic induction and recovery

The effects of three anaesthetics on induction and recovery were compared in Chinook salmon (Oncorhynchus tshawytscha). Heart rate (HR), cardiac output (Q), dorsal aortic pressure (DAP) and stroke volume (SV) were measured in minimally disturbed salmon during 5 min anaesthetic inductions with approximately equi-potent concentrations of MS222 (100 ppm), metomidate (6-10 ppm) and AQUI-S (60 ppm). MS222 induction caused a steady decline in DAP only, while metomidate induction did not affect any cardiovascular variable. AQUI-S caused a biphasic response, and within 2 min had depressed HR, Q, DAP and SV by between 20 and 50%. In the final 3 min HR returned to pre-anaesthesia levels, and Q and SV climbed to greater than pre-anaesthesia levels. Blood samples taken pre- and post-anaesthesia showed all inductions caused hypoxaemia (oxygen partial pressure of dorsal aortic blood (PaO2): MS222 47 mmHg, metomidate 35 mmHg, AQUI-S 21 mmHg). Haematocrit and plasma adrenaline and noradrenaline levels increased slightly in AQUI-S treated fish only. Recovery was monitored for 6 h post-anaesthesia, and was similar for each anaesthetic. All cardiovascular variables had returned to control levels within 5 min with the exception of DAP, which was initially slightly elevated (up to 20%) but returned to control values within 30 min. Anaesthesia is usually preceded by handling. Netting prior to anaesthesia caused significant increases in HR, Q and SV, which masked any anaesthetic dependent effects. Recovery from anaesthesia combined with surgery was also generally anaesthetic independent and recovery was prolonged, compared to anaesthesia alone. These data suggest limiting fish handling/manipulation is more important in minimising cardiovascular disturbance than the choice of anaesthetic.     

Effects of anaesthesia with MS 222, neutralized MS 222 and benzocaine on the blood constituents of rainbow trout,Salmo gairdneri†

Rainbow trout (Salmo gairdneri Richardson) were subjected to 15 min anaesthesia with unbuffered MS 222, neutralized MS 222 and benzocaine with and without physical stress. Blood samples were taken through cannulae inserted into the dorsal aorta. The Hct values and Hb concentrations increased with all the anaesthetics, which also caused swelling of erythrocytes. The initial values were restored within 4–12 h of recovery. Each anaesthetic elevated the blood lactate concentration, but the initial level was regained within 12 h. The blood glucose level decreased the most during anaesthesia with unbuffered MS 222, but the initial level was rapidly restored. Benzocaine caused the least hypoglycaemia during anaesthesia, but the subsequent hyperglycaemia, as in the fish anaesthetized with neutralized MS 222, lasted 24 h. Neutralized MS 222 and benzocaine elevated the plasma K + concentration more rapidly than unbuffered MS 222. The initial levels were regained in 4 days. All anaesthetics raised the Mg ⁺⁺ concentration. The Po₂ in the dorsal aorta decreased during anaesthesia with unbuffered MS 222 by about 85 mmHg, while the Pco₂ increased by about 1.5 mmHg. Their initial levels were regained within 20 min. During anaesthesia the pH value decreased by 0.3 units and returned to the initial value within 2–4 h of recovery. MS 222 seemed to be an asphyxiant.     

Effect of tricainemethanesulfonate (MS222), clove oil and electro-anaesthesia on respiratory burst activity in whole blood and serum alternative complement response in rainbow trout (Oncorhynchus mykiss), during the narcosis stage

There is a little available information on the suppressive effect of anaesthesia on immune response in fish, especially electro-anaesthesia. In the present study, two anaesthetics, MS222 (50 ppm), clove oil (25 ppm), and electro-anaesthesia were tested in rainbow trout (Oncorhynchus mykiss) during the narcosis stage in order to observe their effects on the innate immune system. The results showed that electro-anaesthesia reduces light emission in chemiluminescence assay both 1 and 24 h post anaesthesia. Clove oil and MS222 decreased light emission 24 h post anaesthesia. In addition, clove oil, MS222 and electro-anaesthesia had no effect on alternative complement (ACH50) response. From the perspective of aquaculture practice, these data show that the type of anaesthesia should be taken into account to avoid possible immunosuppression in rainbow trout.     

Laboratory studies on the effects of thermal change on the behaviour and distribution of juvenile chum salmon in sea water

Schooling chum salmon Oncorhynchus keta were biased towards the water surface (median position <1 m) under isothermal conditions (10° C) in a water column simulator (WCS). Thermal stratification (24/10° C) inhibited upward movement with fish congregating at the thermocline and displaying a clear avoidance of potentially lethal surface waters. A tri-phase model based on piece-wise nonlinear regression was used to describe the distribution shifts of chum salmon during a change from isothermal to thermally stratified conditions. Fish distribution was consistent with thermoregulatory behaviour and exhibited 'attraction', 'preference' and 'avoidance' phases. The thermal preference of 50% of the fish lay between 12·2 and 20·2° C, however, >83·5% of the fish occupied a 'preferred' temperature range of 13·7–17·9° C. The mean temperature at which 50% of chum salmon avoided rising temperature by shifting deeper in the water column and using the cooler thermocline was 20·2° C, and 90% avoidance occurred at 22·9° C. Behavioural responses to thermal stratification were consistent amongst underyearling fish of differing size and age.     

Haematological assessment of the effects of the anaesthetic MS 222 in natural and neutralized form in three fresh water fish species: haemoglobin electrophoresis, ATP levels and corpuscular fragility curves

The effects of MS 222 and neutralized MS 222 anaesthesia on haemoglobin electrophoresis, erythrocyte adenosine triphosphate (ATP) levels and corpuscular fragility curves were studied in Cyprinus carpio, Sarotherodon mossambicus and Salmo gairdneri . Haemoglobin electrophoresis showed no significant intra-species differences in the percentage composition of the various fractions for any concentration of MS 222 and neutralized MS 222 used. Significant interspecies differences were, however, still observed. ATP levels showed intra and interspecies differences ascribed to the response of the fish species to MS 222-induced stress and not to actual changes in erythrocyte ATP concentrations. Differences were also observed in corpuscular fragility curves for all three species when using MS 222 or neutralized MS 222 compared to curves obtained without the use of the anaesthetic, but the mechanisms involved are not clear.     

Effects of sampling conditions on selected blood variables of rainbow trout, Salmo gairdneri Richardson

The effects of two methods of specimen immobilization (MS 222 anaesthesia and stunning), two types of anticoagulant (EDTA and heparin), two storage temperature ranges (0–2°C and 22–25°C) and four sample storage periods (0, 1, 3, and 24 h) on the haemoglobin, haematocrit, plasma and packed cell sodium, potassium and chloride ion concentrations and packed cell ATP levels of rainbow trout were examined. Stored samples exhibited increases in cell volume, net transfer of sodium and chloride from plasma into cells, net loss of potassium to plasma and rapid depletion of ATP. Room temperature conditions and prolonged storage exacerbated these changes. Use of EDTA, particularly in combination with MS 222, frequently led to haemolysis. Least change in most variables was observed in samples drawn from stunned specimens, treated with heparin and refrigerated before use or preparation for deep cold storage.     

Tricaine methane‐sulfonate (MS‐222) application in fish anaesthesia

Tricaine methane‐sulfonate (MS‐222) is one of the most widely used anaesthetics for poikilotherms worldwide. This paper outlines its anaesthetic efficacy and dosage in fish and legislation for its use, fish stress responses to MS‐222 anaesthesia and its effect on fish physiology and blood properties, pharmacokinetics, genotoxicity, immune response, potential interference with fish hepatic cytochrome P450 spectra, and its impact on nerve sensitivity. Key questions arising from the available data are analysed, such as regulatory constraints on its use, the need for the standardization of buffering protocols, and interdependencies of the factors impacting the specific applicative efficacy of MS‐222. Current research has provided an abundance of data on MS‐222 use in fish, although the applications within these studies are often impractical at the farming level. Specific emphasis is therefore placed on highlighting application strategies on a practical basis, presenting potential future research on topics that require in‐depth analysis (preparation and storage of anaesthetic solutions, pre‐anaesthetic sedation and stress reduction, cortisol response in aquarium fish, toxicity of MS‐222 metabolites, and possible immunodepressive properties). Additionally, both from a scientific and practical perspective, it is necessary to have a better understanding of safety margins, induction, immersion and recovery times for many (marine and freshwater, farmed and ornamental) fish species in order to achieve optimal utilization.     

Plasma cortisol stress response in fingerling rainbow trout, Salmo gairdneri Richardson, to various transport conditions, anaesthesia, and cold shock

Plasma cortisol levels of fingerling rainbow trout were measured as an index of the stress resulting from various procedures used for transport of the fish for stocking. When transported under 'normal' conditions, which included water at the hatchery acclimation temperature (10–11°C), O₂ saturation or supersaturation, and neutral pH, there was a marked increase in plasma cortisol levels within 0.5 h, which was maintained over the next 4 h of transport; there was a significant decrease in plasma cortisol by 8 h of transport. It was found that the plasma cortisol levels at 4 and 8 h were not appreciably altered by transport under partial O₂ desaturation, O₂ saturation, O₂ supersaturation, or 0.5% NaCl, or by anaesthesia with tricaine methanesulfonate (MS 222) prior to capture and transport in MS 222-free water or 0.5% NaCl. A 15 min exposure to an immobilizing dose of buffered or unbuffered MS 222, or 2-phenoxyethanol, caused an increase in plasma cortisol of about 2 h duration, indicating that anaesthetics are themselves stressful. Exposure to chilled water (1° C) caused a large increase in plasma cortisol levels by 4 h after initiation of exposure; plasma cortisol had decreased at 1 day, and by 2 days a constant level was reached which was above the level in fingerling trout under 'normal' hatchery conditions. Trout acclimated to chilled water for 24 h and transported in chilled water had an increase in plasma cortisol during transport. Anaesthesia prior to transport or addition of salt did not reduce the stress of transport as judged by plasma cortisol levels. The results indicate that stress from capture and transport during stocking cannot be avoided using present methods.     

Haematological assessment of the effects of the anaesthetic MS 222 in natural and neutralized form in three freshwater fish species: interspecies differences

Interspecies haematological differences to MS 222 and neutralized MS 222 anaesthesia were investigated in Sarotherodon mossambicus, Cyprinus carpio and Salmo gairdneri acclimated under identical laboratory conditions. Anaesthesia with MS 222 resulted in a 'chemical stress' in all fish, as was evident from changes in the haematological profiles of the animals. Such species specific variations in the haematology persisted throughout the whole experiment protocol which employed different concentrations of the anaesthetic. The use of neutralized MS 222, whereby aquarium water quality remained unchanged, improved the haematological profile. Possible reasons for the interspecies differences observed are discussed.     

Diet of post-smolt and one-sea-winter Atlantic salmon in the Bothnian Sea, Northern Baltic

Until July, post-smolt salmon Salmo salar ( n =337; 129–375 mm L _T, mean 225 mm) in the Bothnian Sea relied largely on surface fauna (mainly terrestrial insects). From August onwards, fish was the principal food type. The smallest piscivorous post-smolts were <200 mm, but the main shift to piscivory occurred at sizes of 240–320 mm. Piscivory was promoted by a large smolt size. Almost all one-sea-winter (1-SW) salmon ( n =316; 278–524 mm, mean 397 mm) were piscivorous. Over 70% of the post-smolt and 96% of the 1-SW salmon with identifiable fish species in their stomachs had preyed on herring Clupea harengus. Other fish prey included the ten-spined Pungitius pungitius and three-spined sticklebacks Gasterosteusaculeatus but no sprats Sprattus sprattus. The results support earlier observations of a close relationship between recruitment of herring and production of salmon in the Bothnian Sea, and of the crucial role of smolt size in determining the ability of feeding salmon for utilizing the food resources of the area.     

Bimodal length frequency distribution in 0+aged masu salmon,Oncorhynchus masou,in a natural stream of southern Hokkaido

The frequency distribution of the fork length of 0⁺ aged masu salmon,Oncorhynchus masou, changed from unimodal to bimodal distribution in autumn of the years from 1982 to 1984 in the Mogusa River of southern Hokkaido, Japan. The bimodal distribution consists of two (upper and lower) modal groups. These two groups resulted from a difference in growth rate of 0⁺ aged individuals in autumn. Fish belonging to the upper modal group are assumed to be potential 1⁺ smolts. Whether 0⁺ aged parr transform into smolt or remain as parr in the following spring may be related to the growth rate of fish in the first autumn.     

Haematological assessment of the effects of the anaesthetic MS 222 in natural and neutralized form in three freshwater fish species: intraspecies differences

The effects of different concentrations of natural MS 222 and neutralized MS 222 were studied on the haematology of Cyprinus carpio, Sarotherodon mossambicus and Salmo gairdneri . As judged from the results, MS 222, which is acidic in nature, produced haemo-concentration effects in all species studied, being least in the trout followed by carp and Sarotherodon mossambicus . These differences are ascribed to acid-base regulatory functions and metabolic activities of the fish species investigated. The use of neutralized MS 222 improved the haematological profiles markedly and resulted in stabilization of acid-base parameters and red blood cells sizes and numbers. Haemoconcentration effects, however, still persisted. Trout were found to be more susceptible to the stress of MS 222 anaesthesia than carp and Sarotherodon mossambicus .     

The glucose and lactate kinetics of American eels, Anguilla rostrata (LeSueur), under MS 222 anaesthesia

Glucose and lactate kinetics were examined in fed and food-deprived American eels, Anguilla rostrata (LeSueur), under MS 222 anaesthesia (AE). These values are compared to free-swimming, non-anaesthetized animals (FSE) reported previously (Cornish & Moon, 1985). The AE group demonstrated a steady but minor hyperglycemia during the 5-h experiment and significant decreases in both glucose turnover and metabolic clearance rates compared to the FSE groups. Food-deprivation further depressed these kinetic parameters.
Blood lactate continuously increased during the experiment, reaching values 300 times (fed) and 100 times (food-deprived) higher than the similar FSE groups. Consistent with these higher concentrations, rates of lactate appearance in and disappearance from the blood generally increased with anaesthesia.
This study supports the view of Soivio et at. (1977) that MS 222 acts as an asphyxiant. The associated metabolic disruptions are consistent with a reduction in oxidative in favour of anaerobic tissue metabolism. The specific changes in glucose and lactate parameters reflect the nervous and hormonal disruptions occurring with anaesthesia. These studies urge caution in the interpretation of data using an anaesthetized fish preparation.     

The histopathology of salmon tagging

Hatchery reared Atlantic salmon ( Salmo salar L.) parr were tagged with the standard I.C.E.S./I.C.N.A.F. salmon tag at water temperatures of 15°C and 6°C. They were then subjected to swimming trials in a tunnel respirometer. Following this treatment the 15°C fish developed necrotic infarcts around the tag insertions. Provided they did not become infected these lesions healed, but if the fish were retested 9 days later, the wound enlarged, became extremely inflamed, and the fish died soon after. This effect was not seen in 6°C fish.     

Effects of four anaesthetics on the innate immune response of gilthead seabream (Sparus aurata L.)

Anaesthesia may depress the immune system in mammals, but there is no available information on this topic in fish. In the present work, four anaesthetics that are used in aquaculture, MS222 (0 19 mM), benzocaine (0.21 mM), 2-phenoxyethanol (16 mM) and quinaldine sulphate (0.083 mM), were tested in order to observe their effects on the gilthead seabream (Sparus aurata L.) innate immune system. The results showed that the four anaesthetics produced increased blood glucose levels after an hour. In addition, benzocaine and 2-phenoxyethanol depressed complement activity and phagocytosis, while MS222 and quinaldine sulphate did not. Some anaesthesia is a common practice in aquaculture, the data obtained should be taken into account to avoid possible immunodepression in farmed fish.     

Factors affecting river entry of adult Atlantic salmon in a small river

In this study, effects of stock origin, fish size, water flow and temperature on time of river ascent of adult Atlantic salmon Salmo salar were tested. Brood stocks were collected in eight Norwegian rivers situated between 59 and 69° N. The fish were reared to smolts, individually tagged and released in the River Imsa, south-west Norway (59° N). Adults from all stocks approached the Norwegian coast concurrently, but Atlantic salmon ≥70 cm in natural tip length entered coastal water slightly earlier during summer than smaller fish. Atlantic salmon <70 cm, however, ascended the river significantly earlier and at lower water flow and higher water temperature than larger fish. Although largest in size, the fish from the northern populations (62–69° N) ascended the River Imsa almost 1 month earlier than those from the south (59–60° N). They seemed less restricted by the environmental factors than the fish originating from the more southern rivers. There was no apparent trend among years in time of river ascent. Maximum ascent per day occurred at water discharges between 12·5 and 15 m³ s⁻¹ and at water temperatures between 10 and 12·5° C. There was a significant positive correlation between water flow and river ascent during the first part of the upstream run from July to September with best correlation for September, when multiple regression analysis indicated that water temperature had an additional positive effect. Stock origin, fish size and water discharge were important variables influencing the upstream migration of Atlantic salmon in small rivers.     

The efficacy of eugenol and tricaine methanesulphonate as anaesthetics for juvenile Chinese sea bass (Lateolabrax maculatus) during simulated transport

The purpose of this study was to evaluate the anaesthesia effects of eugenol and MS‐222 sedatives applied on juvenile Lateolabrax maculatus during simulated transport. In experiment 1, the juveniles were divided into two groups, with seven concentrations tested on each group (eugenol [4, 6, 8, 10, 12, 14 and 16 mg/L] and MS‐222 [20, 30, 40, 50, 60, 70 and 80 mg/L]). Induction and recovery times were recorded. The time for anaesthesia was shortened, and the time for complete recovery was prolonged as the anaesthetic concentration increased. The optimal transport concentration for each anaesthetic tested was 6 mg/L of eugenol and 30 mg/L for MS‐222. In experiment 2, the 5‐hr simulated transport test showed that the survival rate of L. maculatus juveniles with anaesthesia was 100%, and without anaesthesia, survival was 60%. After 24 hr of recovery following transport, the fish showed 100% survival for the group with added anaesthetic and 40% for the group without added anaesthetic. Compared to the non‐anaesthetized groups, the anaesthetized transport groups showed significant increases in the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) (p < 0.05). The levels of AST, ALT and alkaline phosphatase (AKP) were significantly higher in the MS‐222 transport group than in the eugenol transport group (p < 0.05). The levels of AKP were significantly higher in the non‐anaesthetized transport group than in the anaesthetized group (p < 0.05). According to the present experiment results, eugenol was an efficient anaesthetic in L. maculatus, and we recommend eugenol instead of MS‐222 as an anaesthetic for the short‐time transport of L. maculatus.