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Marine Ecology Progress Series

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MEPS 540:193-201 (2015)  -  DOI:

Modelling population effects of juvenile offshore fish displacement towards adult habitat

K. E. van de Wolfshaar1,*, I. Tulp1, H. Wennhage2, J. G. Støttrup3

1Wageningen IMARES, PO Box 68, 1970 AB, IJmuiden, The Netherlands
2Institute of Marine Research, Department of Aquatic Resources, Swedish University of Agricultural Sciences, Turistgatan 5, 453 30 Lysekil, Sweden
3Technical University of Denmark, National Institute of Aquatic Resources, Charlottenlund Castle, 2920 Charlottenlund, Denmark
*Corresponding author:

ABSTRACT: Recent studies of fish distribution patterns highlight shifts in the spatial distributions of particular life-stages. Focus has thus far been on changes in habitat use and possible drivers for these changes. Yet, small-scale shifts in habitat use of certain life stages may have profound consequences on population dynamics through changes in resource use and competition. To explore this, a conceptual stage-structured model was developed with 3 stages and 2 resources and allowing a move of large juveniles from the shallow to the deep habitat. Large juveniles compete with small juveniles in shallow waters and with adults in deeper waters. Alternative stable states occur, with one state dominated by small juvenile biomass and the other dominated by adult biomass. The model results show for both states that while large juvenile biomass responds to a change in time spent in the deep habitat, the biomass of small juveniles and adults is barely affected.  Between the 2 states there is a profoundly different population response to increased fishing mortality. In the adult biomass dominated state, adult biomass is hardly affected while juvenile biomass increases until population collapse, with increased fishing. In the small juvenile dominated state, adult and small juvenile biomass decrease, and large juvenile biomass increases. This state persists at much higher fishing mortality than the adult biomass dominated state. This study highlights that safeguarding nursery functions in a changing environment requires monitoring of juvenile life-stages in a range of habitats and a spatially adaptive management strategy.

KEY WORDS: Stage-structured model · Complex life cycle · Nursery grounds · Spatial distribution · Competition

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Cite this article as: van de Wolfshaar KE, Tulp I, Wennhage H, Støttrup JG (2015) Modelling population effects of juvenile offshore fish displacement towards adult habitat. Mar Ecol Prog Ser 540:193-201.

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