Spatial association of nest construction by brown trout Salmo trutta.

Spawning patterns in female brown trout Salmo trutta were examined by documenting the construction of nests in a small stream and later excavating them to recover progeny. The maternal provenance of nests was determined by genetic typing of embryos using microsatellite markers. Seventy-two nests, for which position and date of construction were known, were made by 59 individuals. Position and date of construction were known for a further 35 nests, comprising 11 Atlantic salmon Salmo salar nests and 24 nests which contained few or no progeny. Salmo trutta showed a behavioural preference for spawning near (≤ 1 m) prior nests; nests made by different individuals tended to accumulate in a spatial sequence that progressed upstream. The directionality of the association between prior and new nests suggests that later spawners use the residual depressions created by previous spawners as the first element of their own nests.

A critical review of adaptive genetic variation in Atlantic salmon: implications for conservation.

Here we critically review the scale and extent of adaptive genetic variation in Atlantic salmon (Salmo salar L.), an important model system in evolutionary and conservation biology that provides fundamental insights into population persistence, adaptive response and the effects of anthropogenic change. We consider the process of adaptation as the end product of natural selection, one that can best be viewed as the degree of matching between phenotype and environment. We recognise three potential sources of adaptive variation: heritable variation in phenotypic traits related to fitness, variation at the molecular level in genes influenced by selection, and variation in the way genes interact with the environment to produce phenotypes of varying plasticity. Of all phenotypic traits examined, variation in body size (or in correlated characters such as growth rates, age of seaward migration or age at sexual maturity) generally shows the highest heritability, as well as a strong effect on fitness. Thus, body size in Atlantic salmon tends to be positively correlated with freshwater and marine survival, as well as with fecundity, egg size, reproductive success, and offspring survival. By contrast, the fitness implications of variation in behavioural traits such as aggression, sheltering behaviour, or timing of migration are largely unknown. The adaptive significance of molecular variation in salmonids is also scant and largely circumstantial, despite extensive molecular screening on these species. Adaptive variation can result in local adaptations (LA) when, among other necessary conditions, populations live in patchy environments, exchange few or no migrants, and are subjected to differential selective pressures. Evidence for LA in Atlantic salmon is indirect and comes mostly from ecological correlates in fitness-related traits, the failure of many translocations, the poor performance of domesticated stocks, results of a few common-garden experiments (where different populations were raised in a common environment in an attempt to dissociate heritable from environmentally induced phenotypic variation), and the pattern of inherited resistance to some parasites and diseases. Genotype x environment interactions occurr for many fitness traits, suggesting that LA might be important. However, the scale and extent of adaptive variation remains poorly understood and probably varies, depending on habitat heterogeneity, environmental stability and the relative roles of selection and drift. As maladaptation often results from phenotype-environment mismatch, we argue that acting as if populations are not locally adapted carries a much greater risk of mismanagement than acting under the assumption for local adaptations when there are none. As such, an evolutionary approach to salmon conservation is required, aimed at maintaining the conditions necessary for natural selection to operate most efficiently and unhindered. This may require minimising alterations to native genotypes and habitats to which populations have likely become adapted, but also allowing for population size to reach or extend beyond carrying capacity to encourage competition and other sources of natural mortality.

Odorant receptor gene expression changes during the parr-smolt transformation in Atlantic salmon.

The ability of salmon to home accurately to their natal stream to spawn has long intrigued biologists and has important consequences for the maintenance of population structure in these species. It is known that olfaction is crucial to homing, and that the transition from the freshwater to the marine environment (the parr-smolt transformation; PST) is a period of increased olfactory sensitivity and learning, resulting in a permanent memory of natal site odours that is retained, at least in part, in peripheral sensory neurones. These odours are then used as cues by sexually maturing fish on their homeward migration. We used quantitative polymerase chain reaction techniques to demonstrate transient increases in expression of odorant receptor transcripts (of up to fifty-fold over pre-PST levels) coincident with PST. Both olfactory (SORB) and vomeronasal receptors (SVRA and SVRC) are involved, which suggests that the fish learn both environmental odours and semiochemicals (pheromones). Receptor expression varies between families and changes over time indicating both genetic differences in odour stimuli and multiple periods of olfactory sensitivity. We suggest that changes in OR gene expression may have a role in homing behaviour and thus the maintenance of population structure in Atlantic salmon.

Hydrological controls on nutrient concentrations and fluxes in agricultural catchments.

Like many streams draining intensively farmed parts of lowland Scotland, water quality in the Newmills burn, Aberdeenshire, is characterized by relatively high nutrient levels; mean concentrations of NO3-N and NH3-N are 6.09 mg l(-1) and 0.28 mg l(-1), respectively, whilst average PO4-P concentrations reach 0.06 mg l(-1). Nutrient concentrations vary spatially and temporally with levels being highest under arable farming during the autumn and winter. Annual fluxes from the 14.5 km2 catchment are estimated at 25.67 and 1.26 kg ha(-1) a(-1) for NO3-N and NH3-N, respectively, and 0.26 kg ha(-1) a(-1) for PO4-P. Hydrological controls exert a strong influence on both nutrient concentrations and fluxes. Over short timescales nutrient concentrations and fluxes are greatest during storm events when P04-P and NH3-N are mobilized by overland flow in riparian areas, particularly where the soils have been compacted by livestock or farm machinery. Delivery of deeper soil water in subsurface storm flow, facilitated by agricultural under-drainage, provide large contributions of NO3-N on the recession limb of hydrological events. In contrast, groundwater inputs generally have lower NO3 concentrations implying that denitrification may be a pathway of N loss in the saturated zone. Approximately 75% of the N loss for the catchment occurs during the autumn and early winter when high flows dominate the hydrological regime. The close coupling of hydrological pathways and biogeochemical processes has major implications for catchment management strategies such as Nitrate Vulnerable Zones (NVZs) as it is likely that significant groundwater stores with long residence times will continue to cause N losses before water quality improvements become apparent.

Spawning success in Atlantic salmon (Salmo salar L.): a long-term DNA profiling-based study conducted in a natural stream.

Spawning success of Atlantic salmon (Salmo salar L.) was investigated, under near-natural conditions, in the Girnock Burn, an 8-km long tributary of the River Dee in Scotland. Employing minisatellite-based DNA profiling, mating outcomes were resolved over three spawning seasons by assigning parentage to progeny samples removed from spawning nests ('redds'). While individual spawning patterns differed markedly, consistent trends were present over the 3 years studied. Multiple spawning was found to be prevalent. More than 50% of anadromous spawners of both sexes contributed to more than one redd. Up to six redds for a single female and seven for a single male were detected. Both sexes ranged extensively. Distance between redds involving the same parent varied from a few metres to > 5 km. Distances > 1 km were common. Both males and females ranged to a similar extent. Range limit was not correlated to fish size. Pairs were not monogamous, both males and females mating with different partners at different sites. Size assortative mating was apparent among 1991 spawners but was not detected for 1992 or 1995. Redd superimposition was found to be common (17-22% of redds over the 3 years), although it was not correlated to the number of anadromous spawners present. High levels of nonanadromous mature parr mating success (40-50% of total progeny sampled) were recorded, and these likely contribute greatly to the effective population size. The relevance of these findings at the individual and population level is discussed, with particular reference to management implications.

Variation in river water temperatures in an upland stream over a 30-year period.

Stream water temperature data from the Girnock burn, a 30-km2 catchment in Scotland were examined for systematic variation across 30 years of record (1968-1997). The data suggest that there has been no change in mean annual temperature with time, but at a seasonal level there is some indication of an increase in mean daily maximum temperatures during the winter (December to February) and spring (March to May) seasons. For the spring season, there is also evidence that mean temperature has increased. There are no apparent or obvious changes in stream flow to account for this. The strong relationship between air and stream temperatures (r2 = 0.96) implies that changes in the stream are the result of changes in the climate. It is possible that this may occur as a result of the effect of increasing air temperatures which may have also reduced the influence of snow and snowmelt on the catchment during the winter and spring seasons.

Fine sediment influence on salmonid spawning habitat in a lowland agricultural stream: a preliminary assessment.

Spawning habitat utilized by Atlantic Salmon (Salmo salar) and Sea Trout (Salmo trutta) was characterized in a 1.6-km reach of the Newmills Burn, a small, highly canalized tributary of the River Don in Aberdeenshire. The Newmills Burn is typical of the intensively farmed lower sub-catchments of the major salmon rivers on the east coast of Scotland. Such streams have substantial potential in providing spawning and juvenile habitat for salmonids, with high redd densities resulting in egg deposition rates of > 5 m2. However, in comparison with upland spawning tributaries draining less intensively managed catchments, canalization and intensive cultivation has seriously degraded the physical characteristics of aquatic habitats in many streams. In the Newmills Burn, spawning gravels have a relatively high (> 20% by mass) fine sediment (< 2 mm in size) content. The burn is characterized by hydraulic conditions that are suitable for salmonid spawning, with modal velocities of 0.50-0.65 m s(-1) and depths of 0.20-0.25 m. However, infiltration of fine sediments into gravels is rapid during hydrological events in the winter months. Thus, complete siltation of open gravel matrices (simulated redds) can occur within a week, and probably within a single moderate to large storm event. Appreciable, but small, deposition of organic and silt/clay particles can also affect spawning gravels. Egg mortalities in redds following spawning are variable, but can be as high as 86% in the Newmills Burn. This may be related to fine sediment infiltration, reduced permeability of spawning gravels and reduced oxygen supply to ova. It appears that the main cause of high influx is sediment loads mobilized from intensively managed land. It is suggested that fundamental changes to the management of agricultural land is required if fish habitats are to be improved and degraded streams are allowed to re-naturalize. The need for closely focused investigations of the causal relationships between fine sediment infiltration and egg survival is stressed.

Medical education in the later 19th century: the science take-over.

Established in 1858, the General Medical Council was responsible, inter alia, for improving the standard of medical education in Britain. It was agreed on all hands that there were serious deficiencies: there was far too much book-learning and not enough practical knowledge; students graduated who were wholly ignorant of important areas of medicine; there were 19 licensing bodies and the criteria for admission to practise differed widely. Debate continued from 1860 to 1890. A major question was, What sort of education should the student have received before he entered medical school? There were four common answers: (1) he should have received the preliminary education of 'a well-educated gentleman'; (2) he should know a good deal about everything; (3) he should have a better knowledge of science--but how to define science?; (4) he should have done well at school, never mind what he had studied. A second major question was, How should science and practical instruction be combined in the medical curriculum? Many defended the old and not quite dead apprenticeship system; a practical 'sandwich course' was even suggested. The debate ended with the Report of the GMC's Education Committee in 1890, which increased the length of the medical course from 4 years to 5 and brought chemistry, physics and biology into the early years. The amount of clinical work, however, although it was supposed to increase, remained very small.

Capacity of the European eel (Anguilla anguilla) to elongate and desaturate dietary linoleic acid.

The ability of eels (Anguilla anguilla) to further desaturate and chain elongate linoleic acid, 18:2n-6, was studied by feeding diets containing either corn oil or a fish oil to groups of elvers for 12 wk and analyzing proportions of fatty acids in tissue lipids. Over the 12-wk period elvers given both dietary treatments increased in weight by fourfold. The proportion of arachidonic acid, 20:4n-6, present in polar lipids of elvers fed the diet containing corn oil increased from an initial value of 5% by weight to 12% by weight; the corresponding value for elvers given a diet containing fish oil, with little linoleic acid in it, was less than 4% by weight. The capacity of this fish to modify dietary linoleic acid metabolically was confirmed by examining the metabolic fate of radioactive carbon after giving [1-14C]linoleic acid orally to eels. Seven days after administration of the linoleic acid approximately 10% of the radioactivity recovered in liver fatty acids was present in trienes and tetraenes with about 4% occurring in arachidonic acid. Compositional analyses from the feeding experiment also indicated that dietary docosaenoic acid, 22:1n-11, is preferentially oxidized by eels.

Rainbow trout liver microsomal lipid peroxidation. The effect of purified glutathione peroxidase, glutathione S-transferase and other factors.

Glutathione peroxidase (glutathione: hydrogen-peroxide oxidoreductase, EC 1.11.1.9) was purified approximately 600-fold from rainbow trout liver soluble fraction and its activity in the NADPH microsomal lipid peroxidation system tested. The enzyme has an approximate molecular weight of 100 000, contains four subunits and four atoms of selenium per mol protein. No selenium-independent glutathione peroxidase activity could be attributed to glutathione S-transferase (EC 2.5.1.18) in trout liver. Glutathione peroxidase together with glutathione (GSH) did not provide any additional protection in the in vitro liver microsomal lipid peroxidation system over and above that provided by GSH alone. Microsomal lipid peroxidation was, however, reduced by a partially purified glutathione S-transferase together with GSH. The protection provided by dialysed liver cytosol in this system was not GSH-dependent, showing that other factors in addition to glutathione S-transferase are involved. Of other possible factors, vitamin E reduced lipid peroxidation in this system. Concentrations of vitamin E in microsomes before and after peroxidation in vitro indicated that protective cytosolic factor(s) act prior to the termination of the free radical chain reactions effected by vitamin E. A GSH-dependent protective factor was present in microsomal protein, malondialdehyde formation in the in vitro microsomal system being markedly reduced in the presence of 5 mM GSH but not significantly lowered by 1 mM GSH.

The effect of vitamin E and oxidized fish oil on the nutrition of rainbow trout (Salmo gairdneri) grown at natural, varying water temperatures.

Groups of rainbow trout (Salmo gairdneri) of approximate mean initial weight 8 g were grown in outdoor tanks over a 14-week period at water temperatures between 12 degrees (start) and 6 degrees (end). Four diets were used. Two contained non-oxidized fish oil (120 g/kg) with or without supplementary DL-alpha tocopheryl acetate and two contained moderately oxidized fish oil again with or without DL-alpha-tocopheryl acetate. The measured selenium content of the diets was 0.10 mg/kg. No significant differences occurred as a consequence of the use of moderately oxidized oil compared with the corresponding treatments using non-oxidized oil. Significant differences did occur between dietary treatments that contained supplementary DL-alpha-tocopheryl acetate and those that did not. These differences applied to weight gain, haematocrit, erythrocyte fragility, mortalities, liver and muscle tocopherol concentrations and lipid peroxidation of liver mitochondria in vitro. Liver glutathione peroxidase (EC 1.11.1.9) activity was unaffected by the dietary treatments used and the proportions of fatty acids in polar lipids of liver and muscle were little changed by the diets used. Severe muscle damage occurred in trout given diets lacking supplementary DL-alpha-tocopheryl acetate. Previous experiments carried out on rainbow trout at a constant water temperature of 15 degrees ( Hung et al. 1981; Cowey et al. 1981, 1983), using diets lacking supplementary vitamin E, did not lead to differences in weight gain, pathological changes or mortalities. Vitamin E requirement may increase as water temperature decreases; minimum dietary requirements for vitamin E measured at a constant water temperature of 15 degrees may not be valid under practical conditions where water temperatures vary over the year.

Characterization of C-reactive protein from the eggs of the marine teleost. Cyclopterus lumpus L.

Further evidence is presented for the existence in teleost fish of proteins homologous with mammalian C-reactive protein. The amino acid composition is given for a C-reactive protein isolated from the eggs of a marine teleost, Cyclopterus lumpus, by extraction with lecithin in the presence of Ca2+, followed by electrofocusing. A molecular weight of 150,000 was calculated from gel filtration and electrophoresis at different polyacrylamide gel concentrations, while the s20,w was 7.4 S. The 1.5-S subunit had an apparent Mr of 20,000 by SDS-polyacrylamide gel electrophoresis and 21,000 by computer analysis based on amino acid composition. Comparison is made with the physicochemical properties of mammalian C-reactive protein.

Tissue distribution, uptake, and requirement for alpha-tocopherol of rainbow trout (Salmo gairdneri) fed diets with a minimal content of unsaturated fatty acids.

The metabolism of and requirements for alpha-tocopherol in rainbow trout fed diets containing 1% linolenic acid as sole source of unsaturated fat and graded levels of tocopherol (0.06-10 mg/100 g) were examined. Fish grew 5-fold over a 16-week period. In liver, tocopherol was concentrated in mitochondria with little in cytosol. Orally administered [3H]-tocopherol was rapidly taken up by plasma and liver but uptake into erythrocytes and white muscle was much slower; in most tissues radioactivity reached a plateau after about 3 days but in red muscle radioactivity increased over a 10-day period. Activities of enzymes that prevent free radical initiated tissue damage did not change in tocopherol deficiency. Tocopherol-deficient trout had no gross or subcellular pathologies even though liver and muscle were severely depleted of the vitamin. Ascorbic acid-stimulated lipid peroxidation in liver organelles indicated a tocopherol requirement of 2-3 mg/100 g diet; the molar ratios of polyunsaturated fatty acids to tocopherol in livers of trout fed diets lacking or supplemented with tocopherol (100 mg/100 g) were 980 and 170, respectively.

Characterisation of cadmium-binding proteins from mussels, Mytilus edulis (L), exposed to cadmium.

Three Cd2+-binding proteins have been purified and partially characterised from the digestive gland of the bivalve mollusc, Mytilus edulis, after exposure to Cd2+. The major protein, which was judged to be pure on polyacrylamide gel electrophoresis, showed many of the characteristics of mammalian metallothionein; having a high -SH content, few aromatic amino acids and a high A250/A280 nm ratio which disappears on acidification. It also contains Zn and Cu, but differs in its higher apparent molecular weight of about 25 000 and high glycine content (12-19%). The two additional Cd2+-binding proteins had lower cysteine contents and different molar proportions of Cd2+, Zn2+ and Cu2+.

The sequence of amino acids in insulin isolated from islet tissue of the cod (Gadus callarias).

1. S-Aminoethylcysteinyl derivatives of the A and B chains of cod insulin were prepared from the individual S-sulpho chains. 2. Studies on small peptides derived from the S-aminoethylated peptide chains by treatment with trypsin allowed the amino acid sequences in the region of the cysteinyl residues of the A and B peptide chains to be defined. 3. The six amide groups in cod insulin were located by complete digestion of small peptides from the A and B chains with aminopeptidase followed by amino acid analyses. 4. The results, together with previous studies on the oxidized A and B chains, define the sequences of the 51 amino acids that constitute cod insulin.