Abstract
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. While it is known that density-dependent somatic growth can be present too, its general importance remains 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. 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 standardized to enable a direct comparison within and among populations, and estimated parameters were used to quantify the impact of density regulation on population biomass. 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 in 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. 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. Furthermore, 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.
Highlights
Density dependence is a key concept in population ecology (Hassell, 1975; Hixon, Pacala, & Sandin, 2002; May, Conway, Hassell, & Southwood, 1974; Turchin, 1995)
The results reaffirm the importance of density-dependent recruitment in marine fishes, yet they show that density dependence in somatic growth is not
These findings suggest that density dependence early in life may dominate in marine fish, density-dependent body growth may still be relevant, as has been established by case studies in several populations of marine fish (Ivanov & Beverton, 1985; Kovalev & Yaragina, 2009; Olafsdottir et al, 2015; Rijnsdorp & Van Leeuwen, 1992; Rindorf, Jensen, & Schrum, 2008)
Summary
Density dependence is a key concept in population ecology (Hassell, 1975; Hixon, Pacala, & Sandin, 2002; May, Conway, Hassell, & Southwood, 1974; Turchin, 1995). The presence of density dependence is deeply ingrained in the thinking of fisheries scientists because some form of density-dependent compensation is necessary for fish populations to sustain the additional mortality caused by exploitation (Shepherd, Cushing, & Beverton, 1990) Against this background, it would be natural to expect that the nature of density regulation in fish populations would be well understood, but this is not the case (Andersen, Jacobsen, Jansen, & Beyer, 2017). The spatial component of habitat size may be of particular importance in this context (Andersen et al, 2017) These findings suggest that density dependence early in life may dominate in marine fish, density-dependent body growth may still be relevant, as has been established by case studies in several populations of marine fish (Ivanov & Beverton, 1985; Kovalev & Yaragina, 2009; Olafsdottir et al, 2015; Rijnsdorp & Van Leeuwen, 1992; Rindorf, Jensen, & Schrum, 2008). | Journal of Animal Ecolo gy 3 the current paradigm that marine fish populations are primarily regulated by density-dependent recruitment? In this study, we performed the first comprehensive quantitative assessment of density dependence in growth and recruitment and their relative importance for a wide range of marine fish populations and species using data from commercially exploited fish populations from the Northeast Atlantic Ocean
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
