DOI: 10.5061/dryad.573n5tb3h
title: Data from: Population variation in density-dependent growth, mortality and their trade-off in a stream fish

description: Important variation in the shape and strength of density-dependent growth
 and mortality is observed across animal populations. Understanding this
 population variation is critical for predicting density-dependent
 relationships in natural populations, but comparisons among studies are
 challenging as studies differ in methodologies and in local environmental
 conditions. Consequently, it is unclear whether: (1) the shape and
 strength of density-dependent growth and mortality are
 population-specific; (2) the potential trade-off between density-dependent
 growth and mortality differs among populations; and (3) environmental
 characteristics can be related to population differences in
 density-dependent relationships. To elucidate these uncertainties, we
 manipulated the density (0.3-7 fish/m2) of young-of-the-year brook trout
 (Salvelinus fontinalis) simultaneously in three neighboring populations in
 a field experiment in Newfoundland, Canada. Within each population, our
 experiment included both spatial (three sites per stream) and temporal
 (three consecutive summers) replication. We detected temporally consistent
 population variation in the shape of density-dependent growth (negative
 linear and negative logarithmic), but not for mortality (positive
 logarithmic). The strength of density-dependent growth across populations
 was reduced in sections with a high percentage of boulder substrate,
 whereas density-dependent mortality increased with increasing flow, water
 temperature, and more acidic pH. Neighbouring populations exhibited
 different mortality-growth trade-offs: the ratio of mortality-to-growth
 increased linearly with increasing density at different rates across
 populations (up to 4-fold differences), but also increased with increasing
 temperature. Our results are some of the first to demonstrate temporally
 consistent, population-specific density-dependent relationships and
 trade-offs at small spatial scales that match the magnitude of
 interspecific variation observed across the globe. Furthermore, key
 environmental characteristics explain some of these differences in
 predictable ways. Such population differences merit further attention in
 models of density-dependence and in science-based management of animal
 populations.
description: Variables Section: 4 digit code
 for the experimental section (first two letters are the stream, the third
 letter is the site within stream and the last number is the section within
 site, e.g. BC-A-1 is located in site A in Bob’s Cove, and is the first
 section). Length.initial:
 Average length of fish (mm) at the start of the experiment
 Density: Fish
 density, in meter square Abundance: number of
 fish stocked Start.date (start
 date, YYYY-MM-DD) Finish.date (finish
 date, YYYY-MM-DD) Length.final: Average
 length of fish (mm) at the end of the experiment Abundance.final:
 Abundance at the end of the experiment Duration: duration of
 the experiment, in days Sp.Growth: Specific
 growth (% of length/day) Daily.Mortality:
 daily mortality (%/day) Temperature: average
 temperature of a given section in degrees Celsius pH: average pH of a
 given section Width: average width
 of a section (m Boulder: prevalence
 of boulders in the section (%) Cobble: prevalence of
 cobble in the section (%) Pebble: prevalence of
 pebbles in the section (%) Granule: prevalence
 of granule in the section (%) Sand: prevalence of
 sand in the section (%) Macrophyte: area
 covered by macrophyte (%) Total.cover: area of
 the section under cover (includes macrophytes, %) Section.length: total
 length of the experimental section (m) Avg.depth: average
 depth in the section (m) Total.undercut: the
 sum of undercuts on each side of the section