Micro-ando macroscale factors affecting fish assemblage structure in the rocky intertidal zone.

Abstract

Intertidal fish are adapted to live in a fluctuating environment and are considered suitable bioindicators of environmental change. Understanding the relationship between fish species distribution and environmental variables is fundamental for comparative analysis among geographical locations and identification of long-term trends predicted by global warming. Here we analysed a combination of the main micro- and macroscale factors that affect the distribution and abundance of rocky intertidal fish communities. Monthly sampling of fish assemblages at 3 sites in the rocky intertidal zone of the Gulf of Cadiz was conducted from 2008 to 2014. Fish assemblage descriptions were based on relative abundance, biomass, diversity and evenness. A canonical correspondence analysis was performed to evaluate the relationship between pool characteristics (substratum type, depth and surface area) and the abundance of fish assemblages in tidepools. The results showed differences between protected and unprotected sites, which may indicate that human pressure induces changes at all assemblage levels. At all sites, the lowest abundance was observed in the year with the greatest wave energy. The diversity at the 3 sites showed interannual variation correlated with pool complexity, wave energy and air temperature. These findings increase our understanding of the mechanisms that regulate the distribution of fish assemblages in shallow coastal waters and provide a useful baseline for future management and conservation of these areas.