Biophysical modelling of snapper Pagrus auratus larval dispersal from a temperate MPA

Abstract

A high-resolution 3D biophysical model was used to investigate the patterns of larval transport for an important commercial and recreational temperate fish, snapper Pagrus auratus, from a well-established marine reserve (Cape Rodney to Okakari Point marine reserve, CROP), and spawning ground. Our focus was to study the effects of local hydrodynamics, contrasting larval vertical behaviours and changing El Niño-Southern Oscillation (ENSO) cycles (via their effect on wind forcing) on the potential larval supply to adjacent non-protected areas. The model suggests the CROP marine reserve provides significant larval subsidies within a relatively small scale (≤40 km), the details of which depend on larval behaviour and ENSO patterns. Changing ENSO patterns mostly affected the dispersal direction of larvae, while larval behaviour was a strong driver only under La Niña conditions. Modelling suggests that under El Niño conditions, snapper larvae are more likely to settle successfully and hence make a strong contribution to surrounding fished stocks. Understanding the contribution of MPAs to fisheries management will require multiple approaches. Modelling will help identify the strength of contributing physical and biological factors, and in due course enable site-and time-specific examples of larval subsidy to be generalised.

Patterns and trends in marine population connectivity research

“…Many important questions in MPC, such as the influence of pelagic larval duration on connectivity metrics, will be broadly applicable across many taxa (see Selkoe & Toonen 2011). However, some questions will be influenced by taxonomic classification (such as the scale of post-larval movements, Acosta 2002) or the influence of swimming capabilities on planktonic dispersal (Chia et al 1984, Le Port et al 2014. In this review we find that the proportional dominance of larval or post-larval dispersive stages reflects how often those stages are studied in the literature (see Fig.…”

“…In the marine realm, population connectivity has been studied intensively, with many research articles assessing the factors which influence marine population connectivity (MPC) (e.g. Le Port et al 2014, D'Aloia et al 2015 as well as the importance and practical application of MPC (e.g. Roberts et al 2003, McCook et al 2009, Boero et al 2016, Magris et al 2016.…”

Using a biophysical model to investigate connectivity between spawning grounds and nursery areas of King George whiting (Sillaginodes punctatus: Perciformes) in South Australia’s gulfs

“…temperature and salinity) and suitable benthic spawning substratum, which inhibited the development of a statistical egg production model. Nevertheless, temporally limited dispersal models still provide valuable insight into connectivity when the predictions can be interpreted concurrently with empirical biological data (Le Port, Montgomery, & Croucher, 2014; Swearer et al., 2019).…”

Marine reserves indirectly affect fine‐scale habitat associations, but not overall densities, of small benthic fishes

“…Other potential sources of variation in densities of small fishes include larval supply, the availability of food (primarily microinvertebrates), or densities of predators other than snapper. Larval supply is unlikely to differ inside versus outside these reserves, due to tidal currents regularly moving water back and forth along these coasts (e.g., Le Port, Montgomery, & Croucher, ). We see no reason to suspect differences in food availability and predators as surveys were standardized to a single broad habitat type (kelp forest around 10 m depth).…”