No description available.

No description available.

No description available.

Real-time PCR was utilised to measure the expression of several host immune genes in response to experimental infection with either ISAV or infectious pancreatic necrosis virus (IPNV). Probes targeting transcripts produced during type I and type II interferon (IFN) responses demonstrated these viruses induced both responses and peaked by day 6 post infection. The high mortality in ISAV infected fish highlighted the ineffective nature of the response and suggested the virus possesses IFN antagonistic capabilities to circumvent the host defence mechanisms. Viral proteins were studied using transfection-based methodologies to elucidate potential IFN antagonist capabilities with emphasis on the 7i protein as a putative analogue to the non-structural (NS1) protein of influenza. Results of two independent assays demonstrated the 7i protein caused a reduction induction of the interferon stimulated gene, Mx. In addition, RNA binding experiments suggested the 7i protein also possessed an RNA binding function. A surveillance programme with analysis by real-time PCR and sequencing looking for the presence of the putatively avirulent ISAV HPR0 strain, which contains an extra long highly polymorphic region (HPR) with the haemagglutinin-esterase (HE), was performed to demonstrate the extent of this strains presence in Scottish marine Atlantic salmon stocks. A transfection-based system combined with haemadsorption studies was utilised to examine differences in receptor binding and esterase activity of HE proteins obtained from an HPR0 type, a pathogenic virus and a specific combination of the two. The HPR0 HE protein was shown to be functional with respect to both receptor binding and esterase activity although no difference in function could be attributed to the presence of the full-length HPR in comparison to a protein from a pathogenic variant. This suggests the phenotypic variation of HPR0 may lie in another aspect of the viral life cycle.

Growth, feeding and metabolism in juvenile Atlantic salmon Salmo salar L. Growth, feeding and metabolism were studied during the juvenile growth phase of Atlantic salmon. Comparisons were made between the faster and slower growing members of sibling populations which formed the upper and lower modes of a bimodal growth distribution. Several new techniques were developed in order to investigate these parameters in small fish. Specific growth rates of marked individuals within the bimodal distribution followed the same pattern of development as the whole population, and appeared to be more closely related to changes in daylength than ambient water temperature. Morphometric assessment of the growth of the swimming musculature showed that both processes of cell enlargement (hypertrophy) and cellular proliferation (hyperplasia) were important. The relative importance of the two processes was dependent on developmental stage and season, although hyperplasia appeared to be more a characteristic of rapid growth than hypertrophy. Histochemical studies demonstrated the presence of "red", "white", and between them a diffuse band of "pink" muscle which appeared to become less evident during the freshwater growth period. Modal differences in food intake were found between October and March, with the upper mode fish feeding optimally whilst the lower mode fish fed at only maintenance levels. Although no differences were found in food turnover rate, upper mode fish demonstrated an elevated temperature specific food intake and gross conversion efficiency. Photoperiod was an important influence on feeding, affecting both the daily feeding pattern, which was suppressed in darkness; and evacuation rate, which was more rapid for fish experiencing an increasing rather than decreasing photoperiod. Upper mode fish and smolts had higher resting rates of oxygen consumption than lower mode fish at two of the experimental temperatures used. Smolts had larger gills than either modal group, although no differences were found between fish in the upper and lower modes. However, upper mode fish had larger hearts than those measured in the lower mode. The higher levels of metabolism usually associated with smolting appeared to be a normal characteristic of the upper growth mode. The parameters studied are discussed in relation to the energy budget, and it is concluded that the two growth modes comprise two distinct "physiological populations" within the sibling group. Photoperiod is considered to be a primary influence on growth, and it is suggested that differential responses to seasonal and daily changes in photoperiod by individuals may account for both the development of bimodality, and provide the means (through an increased daily and seasonal feeding opportunity) by which higher growth rates are sustained by the upper mode fish.

Aspects of the behaviour of adult Atlantic salmon in estuaries, while on their spawning migration has been investigated using a salinity telemetric system. Eighteen fish were tracked in total in different Scottish estuaries. Studies involving the displacement of salmon from freshwater back into higher salinities on the River North Esk, Montrose showed fast movement through the estuary back into freshwater (5h), movement being initiated by the sensing of low salinities or the start of the flood tide. Tracking in the Dornoch Firth at Bonar Bridge (a channel type estuary) showed fish maintaining one position against both flood and ebb tides, experiencing salinities fluctuating widely about the isosmotic point. The qualitative assessment of salmon on passage through the estuary of the freshwater discharge of a non-natal river was also demonstrated, repeated entries of a very brief nature (21s) being recorded. The position held by salmon whilst on suspended migration in an estuary was recorded, no sampling of the freshwater discharge being undertaken on a tidal basis. The resting metabolic rate of farmed salmon of different stages of sexual development was recorded in saltwater, and on transfer to freshwater. Maturing fish exhibited a raised metabolic rate in saltwater, suggesting increased osmoregulatory costs. This was in contrast to non-maturing fish. The cannulation of wild salmon subjected to fluctuating salinities was undertaken. Plasma electrolyte levels and osmolalities of fish subjected to cyclic salinities were intermediate between salt-adapted and freshwater-adapted values, showing only small fluctuations. An inability to osmoregulate successfully in high salinities following 'stress' events was recorded in maturing farmed and coastally caught wild salmon, suggesting a maladaption to that environment. By contrast, non-maturing farmed salmon exhibited a greater degree of euryhalinity. Examination by electron scanning microscopy of apical pit structure of gill chloride cells supports the idea that increasing maturity or freshwater exposure reduces tolerance to saltwater. It is concluded that Atlantic salmon are euryhaline during at least part of their oceanic feeding phase, and on arrival in coastal waters on the spawning migration require no period of acclimitisation to freshwater. A reduction in tolerance to high salinities linked to advancing maturation/ freshwater exposure would thus serve to ensure river entry.

No description available.

Recent legislative changes have increased the need to monitor contamination effects in Scottish waters and have consequently elevated demand for research into vertebrate and invertebrate ecotoxicological techniques. Selected invertebrate ecotoxicological techniques were used to measure the effects of two industrial contaminants found in Scottish sea lochs i) the synthetic pyrethroid cypermethrin, licensed for treatment of lice infestations in the Scottish salmon farming industry and ii) polycyclic aromatic hydrocarbons (PAHs) released into Loch Leven via the Kinlochleven aluminium smelter. Mytilus edulis accumulated cypermethrin during exposure and exhibited shell closure behaviour. Neither neutral red retention (NRR) time of lysosomes nor aerial survival were affected by concentrations £1000 mg/l. As the shell closure effect occurred at concentrations greater than typical field concentrations (i.e. within and around almost sea cages), Mytilus does not demonstrate suitability for use as a study species when monitoring the biological effects of cypermethrin exposure. Carcimus maenas exhibited 50% mortality after 96 hours of exposure to the salmon treatment dose of 5 mg cypermethrin/1. Exposed crabs exhibited a tetanus-like behaviour. Sensitivity to cypermethrin was comparatively greater inCarcinus than in Mytilus . Activity of the detoxification enzyme glutathione S-transferase (GST) was assessed as a potential biomaker of exposure. GST activity was induced in crabs after 7 days of daily exposure to cypermethrin concentrations of 50 mg/l and 500 ng/l. Although GST activity was sensitive to cypertherin exposure, the brevity of the GST response reduces scope for its use as a biomarker for cypermethrin exposure in the field. Some of the techniques investigated here offer potential for further development and possible implementation into monitoring strategies for the Scottish coastal environment.

The salmon louse (Lepeophtheirus salmonis) is recognised as a major pathogen of farmed Atlantic salmon (Salmo salar). With the growth in salmon farming in Scotland and Norway the problem of lice and the need to understand more about their biology and population dynamics has grown. The aims of this study were to examine various aspects of the reproductive biology of L. salmonis and increase fundamental knowledge of this area. It was discovered that the male reproductive system consisted of a pair of testes, vasa deferentia, spermatophore sacs and cement glands and the female reproductive system consisted of a pair of ovaries, oviducts, cement glands, and a single receptaculum seminis. The processes of spermatogenesis, cogenesis and spermatophore formation were examined and compared with those of other species of copepod. Mating in L. salmonis began with the establishment of a precopulatory pair, between an adult male and predominantly a preadult II female. Following the final moult of the female, copulation proceeded and a pair of spermatophores were transferred by the male onto the female. Details of the mating process and associated reproductive behaviour are described. The possible involvement of sex pheromones in mate location was examined. Both adult males and preadult II females were extremely mobile and freely changed host individual. Some evidence was found to suggest preadult II females produced a chemical stimulus to attract conspecifics. Reproductive output and investment by adult female L. salmonis were examined. Distinct seasonal variation in reproductive output existed in the field and under laboratory conditions. Summer generation females produced 6 batches of eggs whereas winter generation females may have produced 4 or 5 batches. Egg strings produced in summer were shorter and had fewer, larger, eggs compared to egg strings produced in winter. Summer generation females invested more protein per egg than winter generation females, which invested more protein per string. It appeared that total reproductive investment by winter and summer generation females may have been equal. Differences in reproductive output and investment were influenced by changes in environmental parameters, particularly temperature. Preliminary studies into the effect of egg size on hatching and nauplius survival were carried out. These results suggested different reproductive strategies were adopted by winter and summer generations of adult female L. salmonis under different environmental conditions. The causes and implications of these different reproductive strategies are discussed.

Whole salmon scales were analysed using inductively coupled plasma mass spectrometry (ICP-MS) to test for differences in elemental compositions between salmon stocks. The investigation was structured to address stock variation based on fish origin (wild or farmed), farm populations, river origin of wild fish and sea fishery origin (Farces or Greenland). Initial studies were conducted to determine optimal analytical methods and to quantify the effects of fish size, sex, age and interannual variability on trace element composition within a single stock. Although a large number of trace elements were measured in fish scales, only a small number were found to be important predictor elements. The trace element composition of scale samples from wild and farmed fish enabled identification of origin (wild/farmed) to a high degree of accuracy (98 %), with Mn found in significantly higher concentrations in farmed fish and identified as the most influential element. Farmed fish taken from six sites around the west coast of Scotland were also correctly classified with a surprisingly high accuracy using discriminant analysis (87 %). The ability to discriminate between wild stocks was tested using scales from returning fish caught in 12 rivers from around Scotland. Overall classification success was 59 %, but this was found to depend on sample sizes, with elimination of samples comprised of small numbers of individuals improving the classification success to 90 %. The elements showing the highest predictive power differ according to the origin of fish, Mn carries most weight distinguishing farmed from wild fish, Ba, Mn, Zn, Co, Li, Ni and V are important in distinguishing between farms, Li, Sr and Ba strongly influence classification of wild wish and U was found to be the most important predictor element separating out samples recovered from the Farces and West Greenland fisheries. It is suggested that differences in Li and Ba i Abstract contents in scales reflect natural differences in river or catchment water chemistry, Zn, Ni, Co and V are likely to reflect differences in anthropogenic loading within industrialised settings and the high levels of Mn found in farmed fish scales predominantly reflects dietary uptake from supplementation of feed.