scholarly journals The helminth fauna of brown trout (Salmo trutta) from a sub-alpine lake revisited after 40 years with introduced European minnow (Phoxinus phoxinus)

2021 ◽  
Vol 41 ◽  
pp. 15-26
Author(s):  
Reidar Borgstrøm ◽  
Øyvind Hatleli Mestrand ◽  
John E. Brittain ◽  
Leif Lien
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Helminth Fauna ◽  
Helminth Species ◽  
Population Increase ◽  
Intermediate Hosts ◽  
Phoxinus Phoxinus ◽  
Piscivorous Birds ◽  
European Minnow ◽  
Brown Trout Salmo Trutta

The helminth fauna of brown trout (Salmo trutta) in the Norwegian subalpine lake, Øvre Heimdalsvatn was studied by examination of gills, eyes, body cavity, kidney, stomach, pyloric region and intestine in a total of 112 brown trout randomly sampled in June, July, and September 2011. Ten helminth species, Discocotyle sagittata, Phyllodistomum umblae, Crepidostomum farionis, C. metoecus, Diplostomum sp., Proteocephalus sp., Cyathocephalus truncatus, Dibothriocephalus ditremus, D. dendriticus, and Capillaria sp. were identified. These data were compared to data from the period 1969 to 1972, just after the first record of the European minnow (Phoxinus phoxinus) in 1969. All ten helminth species, except D. dendriticus, were also present in 1969–72. However, a few major changes in infection intensities have occurred. The cestode D. ditremus and the trematode Diplostomum sp., both with piscivorous birds as final hosts, had markedly higher relative densities (abundance) in brown trout in 2011 compared to 1969–72, while the two Crepidostomum species showed a substantial decline in relative densities. We suggest that these changes may be indirectly related to the establishment and subsequent population increase of European minnow in the lake. The abundance of minnows may have increased the food basis for the piscivorous birds, primarily mergansers and the black-throated diver that now regularly forage in the lake. In addition, there have been changes in the littoral invertebrate community, including species serving as intermediate hosts of some of the brown trout parasites.

scholarly journals Associations and interactions among intestinal helminths of the brown trout, Salmo trutta, in northern Italy

2001 ◽  
Vol 75 (4) ◽  
pp. 331-336 ◽  
Author(s):  
B.S. Dezfuli ◽  
L. Giari ◽  
S. De Biaggi ◽  
R. Poulin
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Null Model ◽  
Fish Population ◽  
Northern Italy ◽  
Helminth Species ◽  
Intermediate Hosts ◽  
Intensity Of Infection ◽  
Interspecific Associations ◽  
Brown Trout Salmo Trutta

Species co-occurrences and interspecific associations between intensity of infection were studied in helminth communities of three populations of brown trout,Salmo trutta, from northern Italy. Of the eight helminth species, only four were common enough to be included in the analyses:Pomphorhynchus laevis, Acanthocephalus anguillae, Echinorhynchus truttaeandCyathocephalus truncatus. The observed frequencies of co-occurrences of the different species, based on presence/absence data, did not differ from those predicted by a null model derived from prevalence data. However, the intensity of infection (number of individuals per fish) of different helminth species were generally, but not always significantly, negatively correlated in tests of pairwise associations. Variation in fish sizes and its effect on infection levels, and whether or not two helminth species used the same or different intermediate hosts, had no influence on these findings. Of the few significant negative associations found between pairs of helminth species, none was found in more than one fish population. This suggests that interspecific associations may be condition-dependent: even in apparently similar localities, the same combinations of helminth species show different associations. Without evidence of replicability, it is almost impossible to conclude to the consistent role of competition between any pair of helminth species in the field.

scholarly journals Introduced European minnow Phoxinus phoxinus in alpine lakes may increase total mercury concentration in brown trout Salmo trutta

2021 ◽  
Vol 41 ◽  
pp. 41-49
Author(s):  
Reidar Borgstrøm ◽  
Sigurd Rognerud ◽  
Sondre Meland ◽  
Bjørn Olav Rosseland
Keyword(s):  
Brown Trout ◽  
Fish Species ◽  
Salmo Trutta ◽  
Total Mercury ◽  
Trophic Position ◽  
Distribution Area ◽  
Phoxinus Phoxinus ◽  
Allopatric Populations ◽  
European Minnow ◽  
Brown Trout Salmo Trutta

In Norway, the cyprinid European minnow Phoxinus phoxinus has been spread far outside its previous natural distribution area, with lots of establishments in mountain lakes where brown trout Salmo trutta originally was the only fish species. We have analysed δ15N and total mercury (THg) concentration in brown trout from eight lakes, situated between 1031 and 1244 m a.s.l. on the Hardangervidda mountain plateau, southern Norway. One of the lakes is inhabited by brown trout and European minnow, while in the other seven lakes, brown trout is the only fish species. δ15N of brown trout were significantly higher in the population with co-existing European minnow, indicating a higher trophic position of brown trout in this population than in the allopatric populations, probably caused by piscivory, as indicated by frequent occurrence of European minnow in brown trout diet. The mercury concentrations in brown trout from this lake had values up to around 0.4 mg THg per kg wet weight. The concentrations were significantly higher than in the lakes without European minnow, and together with the δ15N values, indicating that translocation and establishment of European minnow may increase the trophic position of brown trout in previously allopatric populations, and thereby also increase the mercury level. 

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