Cromarty Firth Fishery Board

Habitat quality can have far-reaching effects on organismal fitness, an issue of concern given the current scale of habitat degradation. Many temperate upland streams have reduced nutrient levels due to human activity. Nutrient restoration confers benefits in terms of invertebrate food availability and subsequent fish growth rates. Here we test whether these mitigation measures also affect the rate of cellular ageing of the fish, measured in terms of the telomeres that cap the ends of eukaryotic chromosomes. We equally distributed Atlantic salmon eggs from the same 30 focal families into 10 human-impacted oligotrophic streams in northern Scotland. Nutrient levels in five of the streams were restored by simulating the deposition of a small number of adult Atlantic salmon Salmo salar carcasses at the end of the spawning period, while five reference streams were left as controls. Telomere lengths and expression of the telomerase reverse transcriptase (TERT) gene that may act to lengthen telomeres were then measured in the young fish when 15months old. While TERT expression was unrelated to any of the measured variables, telomere lengths were shorter in salmon living at higher densities and in areas with a lower availability of the preferred substrate (cobbles and boulders). However, the adverse effects of these habitat features were much reduced in the streams receiving nutrients. These results suggest that adverse environmental pressures are weakened when nutrients are restored, presumably because the resulting increase in food supply reduces levels of both competition and stress.

ABSTRACTThere is increasing evidence from endothermic vertebrates that telomeres, which cap the ends of chromosomes and play an important role in chromosome protection, decline in length during postnatal life and are a useful indicator of physiological state and expected lifespan. However, much less is currently known about telomere dynamics in ectothermic vertebrates, which are likely to differ from that of endotherms, at least in part due to the sensitivity of ectotherm physiology to environmental temperature. We report here on an experiment in which Atlantic salmon (Salmo salar) were reared through the embryonic and larval stages of development, and under differing temperatures, in order to examine the effects of environmental temperature during early life on telomere dynamics, oxidative DNA damage and cellular proliferation. Telomere length significantly increased between the embryonic and larval stages of development. Contrary to our expectations, variation in telomere length at the end of the larval stage was unrelated to either cell proliferation rate or the relative level of oxidative DNA damage, and did not vary between the temperature treatments. This study suggests that salmon are able to restore the length of their telomeres during early development, which may possibly help to buffer potentially harmful environmental effects experienced in early life.

Groups of wild-reared Atlantic salmon Salmo salar smolts were captured during their seaward migration on a tributary of the River Conon, Scotland, U.K., from 1999 to 2014 and tagged with passive integrated transponders (PIT). Fish that subsequently returned to the river after growing at sea were recorded automatically by a PIT-detector in a fish pass. Return rate was related directly to length and condition and inversely to day of the year that the smolt was tagged. Over years, as the study progressed, there was a significant increase in the proportion of smolts returning after two or more years at sea and no trend in returns of salmon having spent one winter at sea. There was no trend in the date of return of salmon across the study period. Fish that had spent more winters at sea returned earlier in the year.

In the course of developing a novel peating process it became apparent that the present methods for determining the intensity of peat smoke on distiller's malt are inadequate. While the colorimetric test for peat phenols is fairly accurate at low levels, it can give misleading results with highly peated malts. Furthermore, the 4-aminophenazone reagent used in this test is not sensitive to some of the major phenol constituents of peat smoke. New qualitative gas chromatographic techniques, which monitor a wider spectrum of peat smoke constituents, are now presented together with some suggested improvements to the existing quantitative colorometric analysis.