Use of Path Analysis to Investigate Mercury Accumulation in Brown Trout (Salmo trutta) in Norway and the Influence of Environmental Factors

1993 ◽  
Vol 50 (6) ◽  
pp. 1158-1167 ◽  
Author(s):  
Eirik Fjeld ◽  
Sigurd Rognerud
Keyword(s):  
Environmental Factors ◽  
Organic Carbon ◽  
Path Analysis ◽  
Total Organic Carbon ◽  
Brown Trout ◽  
Salmo Trutta ◽  
Mercury Accumulation ◽  
Humic Matter ◽  
Atmospheric Depositions ◽  
Brown Trout Salmo Trutta

We studied relationships between environmental factors and mercury accumulation in resident brown trout (Salmo trutta) in 25 lakes in Norway. Our survey showed that mercury concentrations in fish are elevated in areas receiving high atmospheric depositions of mercury. A path analysis revealed that the concentrations of total organic carbon had a critical influence on the bioaccumulation of mercury. This reflects the role of humic matter in the transportation of mercury to lake water and sediments, and perhaps also a stimulating effect on the microbial methylation of mercury. Lake depth influenced the concentration of mercury in sediments, probably due to the complexation of mercury with sedimenting humic matter. The effect of such sediment on mercury concentrations in fish indicated that there exists a concentration-dependent production and release of methyl mercury to the biota. Selenium deposited from the atmosphere seemed to lower the bioavailability of mercury to fish. No effect of pH could be detected. The strong effect of total organic carbon implies that even moderate atmospheric deposition rates may result in relatively high mercury levels in fish, if other local environmental factors favour this.

Recruitment and survival rate variability in fish populations: density-dependent regulation or further evidence of environmental determinants?

2014 ◽  
Vol 71 (2) ◽  
pp. 290-300 ◽  
Author(s):  
Javier Lobón-Cerviá
Keyword(s):  
Environmental Factors ◽  
Brown Trout ◽  
Salmo Trutta ◽  
Survival Rates ◽  
Fish Populations ◽  
Data Set ◽  
Site Specific ◽  
Density Dependent ◽  
Long Term Study ◽  
Brown Trout Salmo Trutta

Recently, Minto et al. (2008) , based on a fishery data set including marine, estuarine, and freshwater fishes, described higher variability in the survival rates of juveniles at low rather than at high parental density in an inversely density-dependent fashion and suggested density-dependent mechanisms underpinning those patterns. This study, based on a long-term study of brown trout (Salmo trutta; a species and habitat not included in the Minto et al. (2008) analysis), documents that survival rates in these stream-living populations exhibit a pattern that matches exactly those reported by Minto et al. (2008) . Nevertheless, hypothesis testing rejected the occurrence of stock–recruitment relationships and the operation of density-dependent recruitment regulation. The patterns elucidated for these brown trout populations can be entirely explained by the operation of two single environmental factors, namely, stream discharge in March determining annual survival rates across streams and sites and site-specific depth determining site-specific survival rates. It is open to question that exactly the same patterns can be generated by two sets of opposing factors, density-dependent (i.e., Minto et al. 2008 ) and environmental factors (i.e., this study). The consistency of this pattern suggests that survival rates and recruitment are probably determined by environmental factors across fish populations and habitats.

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