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Data from: Population variation in density-dependent growth, mortality and their trade-off in a stream fish

Citation

Matte, Jean-Michel; Fraser, Dylan; Grant, James (2019), Data from: Population variation in density-dependent growth, mortality and their trade-off in a stream fish, Dryad, Dataset, https://doi.org/10.5061/dryad.573n5tb3h

Abstract

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.

Usage Notes

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