Data from: Density regulation in Northeast Atlantic fish populations: density dependence is stronger in recruitment than in somatic growth

1. Population regulation is a central concept in ecology, yet in many
cases its presence and the underlying mechanisms are difficult to
demonstrate. The current paradigm maintains that marine fish populations
are predominantly regulated by density-dependent recruitment. 2. While it
is known that density-dependent somatic growth can be present too, its
general importance is unknown and most practical applications neglect it.
This study aimed to close this gap by for the first time quantifying and
comparing density dependence in growth and recruitment over a large set of
fish populations. 3. We fitted density-dependent models to time series
data on population size, recruitment and age-specific weight from
commercially exploited fish populations in the Northeast Atlantic Ocean
and the Baltic Sea. Data were standardised to enable a direct comparison
within and among populations, and estimated parameters were used to
quantify the impact of density regulation on population biomass. 4.
Statistically significant density dependence in recruitment was detected
in a large proportion of populations (70%) whereas for density dependence
in somatic growth the prevalence of density dependence depended heavily on
the method (26% and 69%). Despite age-dependent variability, the density
dependence in recruitment was consistently stronger among age groups and
between alternative approaches that use weight-at-age or weight increments
to assess growth. Estimates of density-dependent reduction of biomass
underlined these results: 97% of populations with statistically
significant parameters for growth and recruitment showed a larger impact
of density-dependent recruitment on population biomass. 5. The results
reaffirm the importance of density-dependent recruitment in marine fishes,
yet they also show that density dependence in somatic growth is not
uncommon. Further, the results are important from an applied perspective
because density dependence in somatic growth affects productivity and
catch composition, and therefore the benefits of maintaining fish
populations at specific densities.