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.

The preliminary phase of my project saw the construction of a critical literature review, which meant I had the sieve through all published research related to my topic to locate the information necessary for the thesis. Following this I had to design and build a BRUV that could incorporate a behavioural study, which required lots of testing of prototypes and trouble-shooting until it worked. The data collection phase saw me free dive six times per deployment to the BRUV in a safe manner, to act as the novel cue to the fish. After all the data was collected, I had to refine my video analysis skills as I used BIIGLE to identify behaviours which were put into an ethogram and the abundances of each species of wrasse and bream. Data analysis was also an important part of the project where I learnt to do multivariate statistics using PRIMER. To round off the project, organisational and time keeping skills were vitally important to ensure the thesis was completed in good time to be properly formatted and edited.

The public should be aware of the project to know that our behaviours and treatment of the marine environment has direct impacts on important species living just metres off the coast. Gibraltarians use the sea a lot for a range of activities, so this project aims to show the health of the populations of ecologically important species, and spread awareness of the implications of our presence on their behaviour. The public should also know to provide a sense of ownership for future marine management strategies which tend to be more effective when there is a stakeholder influence. The harbour in particular had a low complexity and abundance of fish, so management plans could be implemented and encouraged by the public to promote a healthy harbour ecosystem.

Seldom are links between behaviour of animals and their abundances cited in scientific literature. I wanted this project to emphasise that the behaviour of animals has direct consequences on the fitness and therefore populations of species. Humans have a heavy influence on the marine environment, which therefore impacts the species in ways that are currently largely unknown to us. This project hoped to create a novel methodology to promote the use of BRUVs for not only investigating populations, but also their behaviours. I wanted the methodology to be easily manipulated by other scientists to make it relevant to their studies when investigating behaviour in the field. I hope this thesis helps to promote the importance of in situ marine behaviour studies, in order to place the most relevant marine management strategy across the globe.

This dissertation undertakes research that is particularly difficult to study in the field; fish behaviour. To ascribe mechanisms for changes in animal behaviour it is important to understand the variables that may influence behaviour. The recent invasion of the algae Rugulopteryx okamurae has smothered the coastal benthic environment of the Western Mediterranean; the long-term ecological implications are still known.

This research project employs Baited Remote Underwater Video (BRUV) to study the effects of resource partitioning and anthropogenic activity on fish abundance and behaviour in two families of fish. Assessing animal behaviour in the field can be notoriously difficult but behavioural traits such as ‘Boldness’ has direct links to Darwinan fitness parameters.

This study is the first of its kind and by novelly assessing fish behaviour in situ Mike has been able to contribute to the understanding of population structure of two families of fish (Sparidae and Labridae) – the implications of which can be used to investigate fish assemblages and effectiveness of MPAs. Local Ecological Knowledge is an important oft overlooked resource, we’d therefore like to thank the local expertise provided by Charlie Carreras in aiding the identification of fish.