Kristiansen Trond

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Kristiansen
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Trond
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  • Preprint
    Does fish larval dispersal differ between high and low latitudes?
    ( 2013-02) Leis, Jeffrey M. ; Caselle, Jennifer E. ; Bradbury, Ian R. ; Kristiansen, Trond ; Llopiz, Joel K. ; Miller, Michael J. ; O'Connor, Mary I. ; Paris, Claire B. ; Shanks, Alan L. ; Sogard, Susan M. ; Swearer, Stephen E. ; Treml, Eric A. ; Vetter, Russell D. ; Warner, Robert R.
    Several factors lead to expectations that the scale of larval dispersal and population connectivity of marine animals differs with latitude. We examine this expectation for demersal shorefishes, including relevant mechanisms, assumptions, and evidence. We explore latitudinal differences in: 1) biological (e.g., species composition, spawning mode, pelagic larval duration (PLD)), 2) physical (e.g., water movement, habitat fragmentation), and 3) biophysical factors (primarily temperature, which could strongly affect development, swimming ability, or feeding). Latitudinal differences exist in taxonomic composition, habitat fragmentation, temperature, and larval swimming, and each could influence larval dispersal. Nevertheless, clear evidence for latitudinal differences in larval dispersal at the level of broad faunas is lacking. For example, PLD is strongly influenced by taxon, habitat, and geographic region, but no independent latitudinal trend is present in published PLD values. Any trends in larval dispersal may be obscured by a lack of appropriate information, or use of ‘off the shelf’ information that is biased with regard to the species assemblages in areas of concern. Biases may also be introduced from latitudinal differences in taxa or spawning modes, as well as limited latitudinal sampling. We suggest research to make progress on the question of latitudinal trends in larval dispersal.
  • Article
    Influence of larval transport and temperature on recruitment dynamics of North Sea cod (Gadus morhua) across spatial scales of observation
    (Wiley, 2020-04-12) Romagnoni, Giovanni ; Kvile, Kristina Øie ; Dagestad, Knut‐Frode ; Eikeset, Anne Maria ; Kristiansen, Trond ; Stenseth, Nils Christian ; Langangen, Øystein
    The survival of fish eggs and larvae, and therefore recruitment success, can be critically affected by transport in ocean currents. Combining a model of early‐life stage dispersal with statistical stock–recruitment models, we investigated the role of larval transport for recruitment variability across spatial scales for the population complex of North Sea cod (Gadus morhua ). By using a coupled physical–biological model, we estimated the egg and larval transport over a 44‐year period. The oceanographic component of the model, capable of capturing the interannual variability of temperature and ocean current patterns, was coupled to the biological component, an individual‐based model (IBM) that simulated the cod eggs and larvae development and mortality. This study proposes a novel method to account for larval transport and success in stock–recruitment models: weighting the spawning stock biomass by retention rate and, in the case of multiple populations, their connectivity. Our method provides an estimate of the stock biomass contributing to recruitment and the effect of larval transport on recruitment variability. Our results indicate an effect, albeit small, in some populations at the local level. Including transport anomaly as an environmental covariate in traditional stock–recruitment models in turn captures recruitment variability at larger scales. Our study aims to quantify the role of larval transport for recruitment across spatial scales, and disentangle the roles of temperature and larval transport on effective connectivity between populations, thus informing about the potential impacts of climate change on the cod population structure in the North Sea.