Seascape connectivity of temperate fishes between estuarine nursery areas and open coastal reefs

Abstract

1. While estuaries are considered valuable nurseries for many harvested fish species, little quantitative data exist about the spatial scales over which estuaries supply individuals to coastal reefs and how this influences coastal metapopulations. Quantifying this connectivity between estuaries and coastal reefs will assist the sustainable management of fisheries and key fish habitat. This information is particularly pertinent considering estuaries world-wide are experiencing degradation and habitat loss.2. We examine how the relative abundance and body length of three exploited fishes (Chrysophrys auratus, Pseudocaranx georgianus and Nemadactylus douglasii) varied in relation to the proximity and size of the nearest estuary, predicting that estuarine dependent species (i.e. C. auratus) would be smaller and more abundant on reefs close to large estuaries. As a network of 'no-take' marine reserves exist across the study area, we also assessed for reserve effects and if these were influenced by the proximity and size of estuaries. Fish assemblages were surveyed using baited remote underwater video systems deployed on 629 rocky reefs across 417 km of coastline in south-eastern Australia.3. As predicted, C. auratus were smaller and more abundant on reefs adjacent to estuaries (<8.5 km), which is consistent with the species being heavily reliant on estuaries as nursery habitats. Neither the length nor abundance of N. douglasii and P. georgianus were influenced by the proximity or size of estuaries. Marine reserves consistently had higher abundances and larger C. auratus, regardless of their proximity to estuaries. However, reserve effects were more variable for both N. douglasii and P. georgianus. Synthesis and applications. Our results suggest that the dispersal of subadultChrysophrys auratus from estuarine nurseries to coastal reefs occurs across relatively small spatial scales, highlighting that conserving the ecological functioning of estuaries is paramount to sustaining recruitment to nearby coastal fisheries. Estuary size and proximity had little influence on populations of both Nemadactylus douglasii and Pseudocaranx georgianus as these species are not | 1407

Habitat and humans predict the distribution of juvenile and adult snapper (Sparidae: Chrysophrys auratus) along Australia's most populated coastline

“…Rather, adult snapper were observed more frequently in the remoter areas of the region where surrounding human population density was relatively low. These findings confirm other research highlighting the importance of modelling habitat associations for snapper at different life stages (Compton et al, 2012;Galaiduk et al, 2017;Swadling et al, in review).…”

Suitability of compensatory saltmarsh habitat for feeding and diet of multiple estuarine fish species

“…However, here we demonstrate that complete biological equivalence in terms of floral diversity and density, may not be required to provide a feeding habitat for fish. In the context of broad-scale historic and contemporary habitat loss within estuaries (Stamp et al, 2022;Swadling et al, 2022), we have highlighted that re-aligned habitats do provide feeding habitats that are being exploited by a range of fish species. Continued construction of re-aligned sites is advocated; however, further study is needed to identify how variability in construction design and habitat development influences fish exploitation of re-aligned habitats, and ultimately how these sites contribute towards fish production from estuarine systems.…”

“…Globally, estuaries provide important nursery habitats for commercially and ecologically important fishes (Stamp et al, 2022; Swadling et al, 2022). In particular, saltmarshes are highly productive habitats (Bouchard & Lefeuvre, 2000; Nixon, 1980), which are known to provide predation refuge (Allen et al, 1994; West & Zedler, 2000) and critical feeding opportunities for many species (Fonseca et al, 2011; Green et al, 2012; Kelley, 1988; Kneib, 1997; Laffaille et al, 2001; Swadling et al, 2022).…”

“…Globally, estuaries provide important nursery habitats for commercially and ecologically important fishes (Stamp et al, 2022; Swadling et al, 2022). In particular, saltmarshes are highly productive habitats (Bouchard & Lefeuvre, 2000; Nixon, 1980), which are known to provide predation refuge (Allen et al, 1994; West & Zedler, 2000) and critical feeding opportunities for many species (Fonseca et al, 2011; Green et al, 2012; Kelley, 1988; Kneib, 1997; Laffaille et al, 2001; Swadling et al, 2022). The importance of saltmarsh as a feeding habitat for juvenile fish is well illustrated by Laffaille et al (2001) & Fonseca et al (2011), who reported that on average 33%–38% of juvenile European Bass ( Dicentrarchus labrax ) entering saltmarsh have empty stomachs, but only 2%–7% were empty when leaving.…”

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Swadling et al, 2022). The importance of saltmarsh as a feeding habitat for juvenile fish is well illustrated by Laffaille et al (2001) & Fonseca et al (2011, who reported that on average 33%-38% of juvenile European Bass (Dicentrarchus labrax) entering saltmarsh have empty stomachs, but only 2%-7% were empty when leaving.Similar results have also been reported for Thinlip Mullet (Chelon ramada) where it is estimated that in the brief 1-2 h tidal submersion of saltmarsh, they are capable of consuming 7%-8% of their total body weight (Laffaille et al, 2001).Despite estuaries providing important habitat for many fish species, they are often modified by anthropogenic activities (Airoldi

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