Honours Project: Abundance of Large Substrate and Pool Size Predict Rockpool Fish Assemblage Structu

Habitat complexity is a term that has been used for decades, although its definition has constantly been adapted to correspond with advances in knowledge and technology. Currently, it is seen as a multifaceted concept that involves considerations of scale, diversity, spatial arrangement, size, and density of structural features within the habitat.

Rockpools are a complex and ecologically dynamic environment, making them ideal for studying the influences of complexity. The aim of the study was to investigate the relationship between habitat complexity and the fish assemblages that inhabit rockpools in south-eastern Australia, comparing the two main methods of quantifying complexity: manual and remote sensing.

Fish assemblages were recorded in a total of 54 pools at 5 sites along south-eastern Australia using a mini baited remote underwater video (BRUV) system. One location (Bellambi) was sampled twice to enable temporal comparisons. Manual metrics of complexity were measured, and remote sensing was used to generate a three-dimensional model of each pool.

Maximum depth, maximum width, and number of rocks equal or greater than 10 cm in diameter were significant predictors of species richness and total abundance, with abundance of rock substrate also interacting with the fish assemblage structure. In addition, the remote sensing metrics were not a predictor of assemblage, therefore differed from the manual measuring metrics. There was a significant influence of the season of sampling on the assemblage and its relationship with complexity.

These results are contributing to a greater understanding of how complexity can influence the fish assemblages observed and is the initial step in understanding the key differences between measuring techniques.