Coastal winds and larval fish abundance indicate a recruitment mechanism for southeast Australian estuarine fisheries

Abstract

Coastal winds transport water masses and larval fish onshore or offshore which may influence estuarine recruitment, yet our understanding of the mechanism underlying this relationship is limited. Here, we combine datasets from a historical database of larval fish off southeast Australia with a high-resolution atmospheric reanalysis model to show that normalised abundance of coastally spawned larvae increased with weak to moderate upwelling favourable winds 14 days prior to sampling. The increase in abundance may reflect increased nutrient and plankton availability for larval fish.Normalised larval abundance decreased following strong upwelling favourable winds but increased after onshore (downwelling favourable) winds, due to wind-driven transport. By combining a commercial estuarine fisheries catch-rate dataset (4 species, 8 estuaries, 10 years) and the high-resolution atmospheric reanalysis model, we show that negative effects of upwelling favourable winds during the spawning period can be detected in lagged estuarine commercial fisheries catch rates (lagged by 2-8 years depending on species' growth rates), potentially representing the same mechanism proposed for larval fish. Upwelling favourable winds in the southeast Australian region have increased since 1850 while onshore winds have decreased, which may have reduced larval recruitment to estuaries. Coastal winds are likely an important factor for estuarine recruitment in the southeast Australian region and future research on the estuarine recruitment of fish should incorporate coastal winds.

Cross-jurisdictional larval supply essential for eastern Australian spanner crabs (

“…Environmental factors such as temperature and current speed have been shown to influence the catchability of spanner crabs in this region (Spencer et al 2017(Spencer et al , 2019a(Spencer et al , 2019b(Spencer et al , 2019c, and it is possible that such factors may also influence juvenile survival. Environmental variables such as onshore winds have also shown correlations with larval fish supply in this region (Schilling et al 2022). Swimming ability has also previously been demonstrated to significantly improve dispersal modelling of juvenile and larval fish, and turtles (Putman and Mansfield 2015;Leis 2021).…”

Entrainment and development of larval fish assemblages in two contrasting cold core eddies of the East Australian Current system

“…Their abundances also usually increased with distance offshore. These relationships with distance were demonstrated by Schilling et al (2022). The summation of various nearshore larval fish taxa to describe the exchange of coastal water masses with offshore has previously provided a useful metric in the region to measure the impact of upwelling (Smith & Suthers 1999), estuarine recruitment (Ford et al 2010) and coastal winds (Schilling et al 2022).…”

“…The index is only a relative index for comparison within a voyage and cannot be compared among studies unless larval abundances are standardised for each study (e.g. Schilling et al 2022). It would be interesting to compare a variety of standardised datasets, to determine how different sized or located eddies may cause different degrees of entrainment.…”

“…The sum of coastally spawned taxa is a useful characteristic of shelf water (e.g. Schilling et al 2022), while oceanic taxa are well represented by the diversity and abundance of larval Myctophidae (Mullaney et al 2011). Such an approach could also include the zooplankton community as a biological property of the larval fish habitat (e.g.…”

Frontal eddies provide an oceanographic triad for favorable larval fish habitat

“…Understanding this balance is important, as it may reveal quantitative environmental signals that could enable fisheries forecasts and facilitate the rebuilding of depleted stocks. Current strength and coastal winds are frequent correlates of fish recruitment (Schilling et al 2020(Schilling et al , 2022. Sometimes, the timing and location of spawning seems perplexing (Bakun and Broad 2003;Reglero et al 2018), but these can often be rationalized in a dynamic oceanographic context.…”