Life history and habitat use of Norwegian brown trout (Salmo trutta)

SUMMARY. 1. Brown trout ( Salmo trutta) life history and habitat use were studied in two Norwegian rivers: the Vosso river system, western Norway, and the Søre Osa, eastern Norway.
2. Age-groups were partly segregated in feeding habitats, the youngest fish living mainly in running water and in the littoral zone of lakes, the older fish also exploiting pelagic waters and deeper epibenthic habitats. In a population with free access to and from the sea, some individuals smoltified and became sea-run migrants, performing yearly migrations to the coastal sea, whereas others stayed as freshwater residents throughout their entire life span.
3. Within local populations, females were larger and less variable in size than males. This was partly because females matured at an older age than males, partly because the sexes tended to exploit feeding habitats with different food and growth Conditions. Within age-groups, females were more pelagic and migrated more than males, whereas males were more confined to running water and epibenthic areas than females. In the pelagic zone, males were more abundant in near-surface water, and females more abundant in deeper areas. When exploiting the same feeding areas, the two sexes grew at the same rate. There therefore appears to be a connection between feeding habitat and the reproductive ecology of brown trout.     

Testing for ecophenotypic variation in a benthic foraminifer

A method for identifying ecophenotypic variants is tested, using two morphological variants of the benthic foraminifer Reophax dentaliniformis Brady from the Baltic Sea. Results show that the example does not correspond to the model for ecophenotypic variation. This is interpreted as showing that the two forms are genetically differentiated and that the gene flow between them is restricted by the water circulation pattern in the Baltic.     

Cambrian-Ordovician lingulate brachiopods from Scandinavia, Kazakhstan, and South Ural Mountains

Lingulate brachiopods are described from the Upper Cambrian - Lower Ordovician (Tremadoc-Arenig) of Scandinavia (Sweden, Denmark, and Norway), South Ural Mountains, northeastern Central Kazakhstan, and the southern Kendyktas Range in southern Kazakhstan. The faunas comprise a total of 56 species of which 20 are new these are assigned to 40 genera, of which the lingulids Agalatassia and Keskentassia , the siphonotretid Siphonotrerella. and the acrotretids Galinella, Longipegma, Ottenbyella, Akmolina, Mamatia, Sasyksoria , and Otariella are new. The new Subfamily Elliptoglossinae is proposed. The poorly known Cambrianardovician stratigraphy of the South Urals. northeastern Central Kazakhstan, and the southern Kendyktas Range is reviewed. Many sequences in these areas that were previously referred to the Upper Cambrian and Tremadoc can now be correlated with the lower Arenig Hunneberg Stage in Baltoscandia. Three main types of faunal assemblages can be distinguished: (1) the Broeggeria assemblage; (2) several microbrachiopod assemblages; and (3) the Leptembolon-Thysanotos assemblage. The Broeggeria assemblage is distributed world-wide in the Tremadoc of the southern Kendyktas Range, Scandinavia, Belgium, Great Britain, Canada, and Argentina, while the Leptembolon-Thysanotos assemblage is confined to the Arenig of an area surrounding the East European platform, including northern Estonia, Poland, Germany, Bohemia, Serbia, and the South Urals. The microbrachiopod assemblages are known mainly from the Upper Cambrian - Arenig of Scandinavia, South Ural Mountains, northeastern Central Kazakhstan, and the southern Kendyktas Range.     

The catchment and climate regulation of pCO2 in boreal lakes

The regulation of surface water pCO₂ was studied in a set of 33 unproductive boreal lakes of different humic content, situated along a latitudinal gradient (57°N to 64°N) in Sweden. The lakes were sampled four times during one year, and analyzed on a wide variety of water chemistry parameters. With only one exception, all lakes were supersaturated with CO₂ with respect to the atmosphere at all sampling occasions. pCO₂ was closely related to the DOC concentration in lakes, which in turn was mainly regulated by catchment characteristics. This pattern was similar along the latitudinal gradient and at different seasons of the year, indicating that it is valid for a variety of climatic conditions within the boreal forest zone. We suggest that landscape characteristics determine the accumulation and subsequent supply of allochthonous organic matter from boreal catchments to lakes, which in turn results in boreal lakes becoming net sources of atmospheric CO₂.     

Spatial summation of heat induced pain within and between dermatomes

The aim was to study spatial summation within and between ipsi- and contralateral dermatomes at different painful temperatures. For heat stimulation we used a computer controlled thermofoil based thermode. The thermode area could be varied in five discrete steps from 3.14 to 15.70 cm2. When we applied the stimuli within a dermatome, the mean heat pain threshold decreased significantly from 45.6 to 43.5 C as the area was increased from minimum (3.14 cm2) to maximum (15.70 cm2). When the areas were increased involving different dermatomes (both ipsi- or contralateral), we found similar decreases in pain threshold. Spatial summation was also found within and between dermatomes at supra-threshold temperatures (46, 48, 50 C).The study shows that spatial summation of pain is most likely a mechanism acting across segments and is existing from pain threshold to tolerance.     

Biomass and structure of planktonic communities along an air temperature gradient in subarctic Sweden

1. Air temperature will probably have pronounced effects on the composition of plankton communities in northern lake ecosystems, either via indirect effects on the export of essential elements from catchments or through direct effects of water temperature and the ice‐free period on the behaviour of planktonic organisms. 2. We assessed the role of temperature by comparing planktonic communities in 15 lakes along a 6 °C air temperature gradient in subarctic Sweden. 3. We found that the biomass of phytoplankton, bacterioplankton and the total planktonic biomass were positively related to air temperature, probably as a result of climatic controls on the export of nitrogen from the catchment (which affects phytoplankton biomass) and dissolved organic carbon (affecting bacterioplankton biomass). 4. The structure of the zooplankton community, and top down effects on phytoplankton, were apparently not related to temperature but mainly to trophic interactions ultimately dependent on the presence of fish in the lakes. 5. Our results suggest that air temperature regimes and long‐term warming can have strong effects on the planktonic biomass in high latitude lakes. Effects of temperature on the structure of the planktonic community might be less evident unless warming permits the invasion of fish into previous fishless lakes.