Fish distribution and behaviour with regard to the time of day and the anthropogenic structural modification of the shallow littoral

Abstract

The shallow littoral zone is under a variety of environmental drivers and anthropogenic pressures. As these factors are highly dynamic, they may affect the distribution and behaviour of littoral fish. The present study investigates the effect of the time of day and the benthic habitat type on the shallow littoral fish community. Diel variations in total fish abundance, community composition, species abundance and behaviour were studied in two neighbouring stations in the Patraikos Gulf (Greece): one with cobble seabed cover and another with anthropogenic habitat structural modifications, like large artificial blocks, rocks and other objects. Visual census revealed that community composition differed depending on both the time of day and the habitat type. Total abundance was highest in the morning, whereas both diel abundance and habitat use were found to be taxon specific, with most species showing a preference for the artificial rocky habitat. Diel differences in species behavioural patterns were also observed, with a greater percentage of fish being active during the day (morning and noon) rather than in the afternoon. Although the fish community does not change entirely within a day or between adjacent locations, it is significantly variable in even small spatial and temporal scales. Consequently, there are implications for the design and implementation of sampling designs and monitoring plans that should be consistent in time of day throughout the sampling period and include locations structurally modified by humans. Furthermore, the management of the shallow littoral zone should consider the small-scale variability and alternate anthropogenic habitat with natural unaltered patches.

Comparing the Structure of Fish Assemblage among Natural and Artificial Shallow Rocky Habitats

“…However, these constructions tend to generate significant environmental impacts, changing the gentler substrate slopes of natural environments to the predominance of vertically structured habitats, as occurs in marinas and ports. Also, the introduction of non-natural building material, the reduction in the complexity of microhabitats, and the modification of water flow can create a radically new environment for marine biota [1]. It has been proven that these changes in the marine ecosystem cause the alteration of local biodiversity, with changes in the taxonomic and functional structure of biological communities [2], and change their distribution [3].…”

“…To carry out this evaluation, the specific objectives of this study were as follows: (1) to identify the differences in terms of complexity and heterogeneity of the natural and artificial habitat; (2) to establish the differences of the fish assemblage structures associated with the artificial and natural habitat, in terms of total abundance, biomass, richness, and diversity; and (3) to compare the abundances of the most relevant fish species at the two habitats in different seasons. To carry out this evaluation, the specific objectives of this study were as follows: (1) to identify the differences in terms of complexity and heterogeneity of the natural and artificial habitat; (2) to establish the differences of the fish assemblage structures associated with the artificial and natural habitat, in terms of total abundance, biomass, richness, and diversity; and (3) to compare the abundances of the most relevant fish species at the two habitats in different seasons.…”