Using the "mean temperature of the catch" to assess fish community responses to warming in a temperate lake

This contribution applies the "mean temperature of the catch" (MTC) concept of Cheung et al. (Nature 497:365-368, 2013) to fish catch data for Lake Peipsi, Estonia/Russia, covering the years 1931 to 2019. The preferred temperature of each of the ten target fish species was obtained from the literature, and combined with the species-specific catch data to obtain MTC values for each year. The analysis of the MTC time series thus obtained with a segmented regression yielded two trend lines, one horizontal at 14.5 degrees C (1931-1986), and the other (1987-2019) ascending with a slope 0.85 degrees C center dot decade(-1). Overall, the segmented regression model explains over half of the variance of the MTC data set (multiple R-2 = 0.53; adjusted R-2 = 0.51). Lake surface water temperatures correlate with MTC, even though weakly (r = 0.30), when considering a 2-year time lag. The fish community of the shallow Lake Peipsi reacts more strongly to temperature changes than marine ecosystems so far studied using the MTC.