Intra‐ and interspecific differences in nutrient recycling by European freshwater fish

Abstract

Summary 1. We measured N and P excretion rates of 470 individuals belonging to 18 freshwater fish species widespread in Western Europe. We assessed the effect of body mass on excretion rates at both the intra‐ and interspecific levels. 2. The high variability in per capita N and P excretion rates was mainly determined by differences in body mass. The scaling coefficients of allometric relationships for both N and P excretion rates were significantly lower than 1 (mean ± SE, 0.95 ± 0.04 and 0.81 ± 0.05, respectively). 3. The slope of the allometric relationship between fish mass and nutrient excretion rate was significantly different among species. We did not detect any influence of phylogenetic conservatism on fish mass and on excretion rates. Further investigations are needed to understand the biological determinants of these differences. 4. This high intra‐ and interspecific variability in per capita excretion rates, coupled with differences in fish body mass, produce marked differences in biomass‐standardised excretion rates. These results thus indicate the necessity for further experimental and in situ investigations on the consequences of nutrient recycling by fish in freshwater ecosystems.

Introduced lake trout alter nitrogen cycling beyond Yellowstone Lake

“…We logged terms (base 10) and used ordinary least squares (OLS) regression (SPSS, version 12.0.1) to create a predictive allometric cutthroat trout and lake trout excretion model based on individual dry mass. The slope of our cutthroat trout and lake trout model (0.70 using reduced major axis linear regression for comparison only) was similar to other slopes measured for Bonneville cutthroat trout (0.71; Oncorhynchus clarkii utah), kokanee salmon (0.96; Oncorhynchus nerka; Wheeler et al 2014), rainbow trout (0.62; Oncorhynchus mykiss), brook trout (0.47; Salvelinus fontinalis; Paulson 1980, Sereda et al 2008, and brown trout (0.75; Salmo trutta; Villéger et al 2012). Reduced major axis linear regression allows biologically interpreting the slope parameter in a symmetric relationship (Warton et al 2006) whereas our predictive allometric OLS model allowed us to estimate the excretion rate based on the trout mass.…”

Diet composition affects the rate and N:P ratio of fish excretion

“…Another potential factor that may confound dietary effects on excretion is that excretion rates of N and P scale differently with body mass (Torres & Vanni, ). If consumers grow at different rates when feeding on diets of differing elemental composition, differences in body mass alone could account for differences in excretion ratios (Villéger et al ., ,b). We were unable to correct for the different allometries of N and P excretion because the units in which excretion was reported varied between studies, but all studies reported excretion as some function of fish mass.…”

Electrofishing efficiency in low conductivity neotropical streams: towards a non‐destructive fish sampling method

“…from 12 to 350 μS cm −1 ; Villéger et al . ). A 3‐m copper cathode and a 20‐cm‐diameter ring anode were used, because a large amount of the fish fauna is small sized (mean fish body size: 49 ± 55 mm, range 10–390 mm), making large anodes inefficient for the capture of a substantial part of the fish.…”