My thesis aimed to use Baited Remote Underwater Video (BRUV) to quantify the impact of varying levels of anthropogenic activity and habitat complexity on the relative abundances and behaviours of wrasse and bream. I investigated the impact of the high use of the marine environment in Gibraltar both recreationally and commercially and the implications these disturbances have on wrasse and breams abundances and boldness. Boldness is the likelihood in which an individual is likely to engage in a risky behaviour, and it influences fitness and therefore abundances of species. There are not many explanations in scientific literature emphasising the importance of studying behaviour, but it is important to understand-especially in the field. Most behavioural studies are completed in a laboratory as quantification of behaviour is difficult to monitor and track in the field. I feel it is important to understand the natural behaviours of organisms without additional variables such as those present in a laboratory. My thesis also saw the production of an ethogram (a descriptor of different behaviours) of commonly observed behaviours seen in the footage. I analysed the footage using a website called BIIGLE, which allowed me to add a tag to each individual identified in the footage, which was used for the quanitification of abundances. The boldness of fish was measured with the use of a novel cue- in the form of me free diving down to the BRUV and monitoring the reactions of the fish at the various sites or habitat complexities. At each site a deployments were completed in sand patches and in patches of the invasive algae Rugulopteryx okamurae. The aim of this was to test if the abundance of wrasse was higher than the abundance of bream with the invasion of R. okamurae, which had been hypothesised through local anglers catches.