Coupling hydrodynamic and individual‐based models to simulate long‐term larval supply to coastal nursery areas

Abstract

For many marine fish species, recruitment is strongly related to larval survival and dispersal to nursery areas. Simulating larval drift should help assessing the sensitivity of recruitment variability to early life history. An individual‐based model (IBM) coupled to a hydrodynamic model was used to simulate common sole larval supply from spawning areas to coastal and estuarine nursery grounds at the population scale in the eastern Channel on a 14‐yr time series, from 1991 to 2004. The IBM allowed each particle released to be transported by currents from the hydrodynamic model, to grow with temperature, to migrate vertically giving stage development, and possibly to die according to drift duration, representing the life history from spawning to metamorphosis. Despite sensitivity to the larval mortality rate, the model provided realistic simulations of cohort decline and spatio‐temporal variability of larval supply. The model outputs were analysed to explore the effects of hydrodynamics and life history on the interannual variability of settled sole larvae in coastal nurseries. Different hypotheses of the spawning spatial distribution were also tested, comparing homogeneous egg distribution to observation and potential larval survival (PLS) maps. The sensitivity analyses demonstrated that larval supply is more sensitive to the life history along larval drift than to the phenology and volume of spawning, providing explanations for the lack of significant stock–recruitment relationship. Nevertheless, larval supply is sensitive to spawning distribution. Results also suggested a very low connectivity between supposed different sub‐populations in the eastern Channel.

Sole larval supply to coastal nurseries: Interannual variability and connectivity at interregional and interpopulation scales

“…The development (growth), swimming behaviour, benthic settlement and survival of each particle were modelled in parallel with its transport in the hydrodynamic model. As the present model relies mainly on a previous approach on a restricted spatiotemporal scale in the Eastern English Channel (Rochette et al, 2012), the explanations about model structure and parametrization were summarized. Details are provided only when the model options have been modified, especially with regards to the extent of the study area and the input of new data.…”

“…With variations along its latitudinal range, the common sole spawns from winter to spring, pelagic larvae dwell during several weeks (≈ 1-2 months; Rochette et al, 2012) and newly metamorphosed individuals settle in coastal and estuarine areas, which act as exclusive nursery grounds for about 2 years, before sexual maturity (Dorel et al, 1991;Riou et al, 2001). Recruitment variability, although moderate with regard to many marine fish species, is high for the common sole (Le Pape et al, 2003a, b), with a high influence of hydro-climate on larval transport and larval supply (Savina et al, 2010;Rochette et al, 2012).…”

“…Indeed, larval drift individual based models (IBM) have proved useful to investigate the influence of hydrodynamics on ecology of flatfish larvae. They have been used to study the effects of spawning dynamics (Rochette et al, 2012), hydrodynamics and larval behaviour (Fox et al, 2006;Sentchev and Korotenko, 2007;Bolle et al, 2009), dispersal kernels Sentchev and Korotenko, 2005) or connectivity within a population (Rochette et al, 2012) or a meta-population (Savina et al, 2010). However, most of these studies were conducted on relatively short periods of time and/or limited spatial scales.…”

Numerical modelling of physical processes governing larval transport in the southern North Sea

“…With regards to vertical migration of larvae, Savina et al (2010) showed that for 2 examined years (1995 and 1996) the impact of inter-annual variability in the hydrodynamic conditions on the drift of sole exceeded the influence of various vertical migration regimes. Rochette et al (2012) showed that for sole the settlement success in the English Channel area shows significant inter-annual variability. This is in contrast to the limited variability in settlement figures for the English Channel presented here.…”

Coupling Environmental, Social and Economic Models to Understand Land-Use Change Dynamics in the Mekong Delta

“…There is a need, then, to provide a form of translation (Moreira et al, 2009 calls it a "coupler") that takes into account the peculiarities of each model, often linked to the formalism in which it is described (e.g., agent-based modeling, discrete event, continuous equations). Numerous works have therefore addressed the problem of combining or coupling models described using different paradigms, like for example Rochette et al (2012) on the coupling of hydrodynamic continuous models and individual-based models, Quesnel (2005) on the coupling of physical and social models, Rousseaux et al (2012) on the coupling of continuous and discrete formalisms in ecological modeling or Nguyen et al (2008) on the coupling between agent-based models and equation-based models through the use of intermediate graph-based representations.…”