Microhabitat partitioning between sympatric intertidal fish species
highlights the importance of sediment composition in gravel beach
conservation
Abstract
1 Gravel beaches in the Mediterranean ecoregion represent an
economically important and unique habitat type. Yet, burgeoning tourism,
intensive coastal development and artificial nourishment of beaches may
jeopardize their ecological communities. To date, species that reside on
gravel beaches and the consequences of beach alterations are poorly
understood, which hampers the development of a sustainable coastal
tourism industry along the region’s shorelines. 2 Using a simple
collection method based on dredging buckets through the intertidal
section of beaches, we quantified the microhabitat association of two
sympatric clingfish species in the genus Gouania at seven natural and an
artificial gravel beach based on sediment characteristics. We
hypothesized that slender (G. pigra) and stout (G. adriatica)
morphotypes would partition interstitial niche space based on sediment
size, which may affect the vulnerability of the species to changes in
gravel beach composition due to coastal development. 3 We detected
substantial differences in gravel composition within and among the
sampled beaches which suggests scope for microhabitat partitioning in
Gouania. Indeed, we found significant relationships between species
identity and the presence/absence and abundance of individuals in hauls
based on their positioning on PC1. 4 Our results suggest that
modifications of gravel beaches through coastal development, including
beach nourishment, intensifying coastal erosion, or artificial beach
creation, may have detrimental consequences for the two species if
sediment types or sizes are altered. We posit that, given the simplicity
and efficacy of our sampling method and the sensitivity of Gouania
species to prevailing gravel composition, the genus could serve as an
important indicator for gravel beach management in the Mediterranean
ecoregion.