Influence of intertidal seascape on the functional structure of fish assemblages: Implications for habitat conservation in estuarine ecosystems

Abstract

Habitat loss and fragmentation remain major threats in estuaries, particularly with respect to the erosion of intertidal areas that provide shelter and food resources for numerous fish species. Improving our understanding of the fauna–intertidal seascape relationship is thus of critical importance. Here, the seascapes of 24 tidal estuaries were compared at multiple spatial scales (from estuary to local) to determine how the spatial structure of intertidal patches affects the abundance of several fish functional groups. For the majority of fish groups, our results support the statement that a large intertidal area can support high fish abundance at both of the studied scales; however, the spatial distribution of patches within estuaries, and especially the presence of large intertidal patches close to the estuary mouth, appeared to be an important feature for both marine and estuarine‐resident fish. It was also shown that habitat fragmentation at the estuary scale is associated with a decline in the abundance of several fish groups, probably as a result of reduced intertidal suitability and accessibility. At the local scale, the area of intertidal–subtidal interface was positively related to fish densities, emphasizing the importance of fish having permanently flooded refuges close to feeding grounds. This study provides essential insights to guide conservation and restoration actions for intertidal areas at both estuary and local scales (10–100 m2), by stressing differences in species sensitivity to seascape modification.

Seascape context matters more than habitat condition for fish assemblages in coastal ecosystems

“…Restoring ecosystems nearer to the estuary mouth that provide steppingstones for migratory species is therefore an important consideration for management (Gilby et al 2018c). Intertidal flats provide unique niches for a variety of fish species (Teichert et al 2018); connectivity between intertidal flats and structurally complex natural vegetation means that species are able to benefit from the unique attributes (i.e. feeding opportunities, protection) of both habitats (Lugendo et al 2006), and this increased the abundance of fish in several ecosystems in this study.…”

“…The physical attributes of estuarine seascapes, including connectivity with physical features like the estuary mouth and intertidal flats, were the most important variables for fish assemblages in this study. Connectivity with the estuary mouth has previously been shown to be a significant predictor of the structure of fish communities, with sites nearer to the estuary mouth supporting a higher abundance and diversity of fish (Teichert et al 2018, Goodridge Gaines et al 2020), the rate of key ecological functions and the functional traits of fish species (Henderson et al 2020, Jones et al 2020). This can primarily be linked to species which undertake ontogenetic movements throughout their lifecycle between estuaries and offshore habitats (Sheaves 2009, Henderson et al 2017), and the tendency of waters at the estuary mouth to have more consistent water chemistry (Sheaves et al 2015, Henderson et al 2021).…”

Decoupling carry-over effects from environment in fish nursery grounds

“…However, these areas are subject to intense human modifications, including eutrophication, cattle grazing, urban development or harbour activities, which have caused dramatic changes in estuarine structure and functioning (Lafage et al, 2021;Lotze et al, 2006;Teichert et al, 2016a). For example, habitat loss and fragmentation remain a major threat for fish juveniles, particularly due to the erosion, and human induced vegetation shifts, of intertidal areas that provide shelter and food resources (Cattrijsse and Hampel, 2006;Laffaille et al, 2000;Teichert et al, 2018a).…”

Klimaatadaptatieplan voor de estuariene natuur in de Zeeschelde

“…Ook voor vissen en garnaalachtigen is de grootte van de intergetijden gebieden van belang. Er is immers toenemend bewijs dat deze gebieden belangrijk zijn minstens gedurende een bepaalde levensfase Elliot et al 1990;Teichert et al, 2018). Een studie van visgemeenschappen in 24 estuaria toonde aan dat de talrijkheid van vissen sterk bepaald werd door de oppervlakte en fragmentatie van intertidaal gebied, zowel op het niveau van het estuarium als lokaal (Teichert et al 2018).…”

“…Er is immers toenemend bewijs dat deze gebieden belangrijk zijn minstens gedurende een bepaalde levensfase Elliot et al 1990;Teichert et al, 2018). Een studie van visgemeenschappen in 24 estuaria toonde aan dat de talrijkheid van vissen sterk bepaald werd door de oppervlakte en fragmentatie van intertidaal gebied, zowel op het niveau van het estuarium als lokaal (Teichert et al 2018). Op de lokale schaal was de nabijheid en verbondenheid van subtidale en intertidale gebieden een belangrijk factor die visdensiteiten verklaarde.…”