The Use of Baited Remote Underwater Video (BRUV) to Assess the influence of habitat complexity and Anthropogenic Activity on the abundance and Behaviour in Coastal Fish (Labridae & Sparidae): Implications for Marine Management
Wrasse and bream are important grazers in coastal marine ecosystems across the globe. Currently, little research has been conducted on the abundance of wrasse and bream species in the Mediterranean and none exclusively in British Gibraltar Territorial Waters (BGTW). The Western Mediterranean has experienced a recent bioinvasion of the alga Rugulopteryx okamurae, which is reported to have impacts on the benthic marine environment. Anecdotal evidence suggests that bream abundance has decreased while wrasse abundance has increased since the invasion. Behaviour has distinct links to the abundance and fitness of all animals, and understanding them is an important precursor to protect threatened or endangered species.
A lack of research has been conducted on the behavioural traits of fish species from the two families, particularly in terms of boldness. Boldness of species and individuals can be influenced by a range of variables, both natural and anthropogenic. Gibraltarians use their sea recreationally and commercially and perceive it to have a high social and economic value. Little research has investigated other anthropogenic impacts on the marine environment, comparing areas that have a high use by the public and those relatively pristine and human-free such as an MPA. In contrast, a reasonably large amount of literature has been written on the impact of anthropogenic noise on marine fishes. Anthropogenic pressures which vary between different locations around the Gibraltarian coast include swimming/bathing activity, SCUBA diving, fishing/angling, and commercial and recreational boat traffic. Gibraltar has a bathing season during the summer months, where some pressures such as swimming and SCUBA are elevated, and pressures such as fishing are smaller from summer fishing bans from beaches.
There has been an increasing trend in the use of Baited Remove Underwater Videos (BRUVs) worldwide to investigate abundances of marine animals, but they have not been utilised to quantify in situ behaviour of fishes. The present thesis employs BRUVs to investigate the impact of varying levels of anthropogenic activity and habitat complexity (algae; R. okamurae and bare sand) on the abundance and boldness of wrasse and bream species in BGTW. Boldness was measured at the species level and was tested with the presence of a novel cue (NC), in the form of a human disturbance, and corresponding fish responses recorded. Two beaches, the inner harbour, and the Marine Conservation Zone (MCZ) were the four sites investigated in this study. The results from the present study show that there are three statistically significant groupings arising from similarities of population structure (i.e. species present and their relative abundances). There was no difference between the mean boldness of wrasse (Coris julis) and bream (Oblada melanura) within algae patches at any of the sites tested. There was, however, a significant difference observed in C. julis boldness scores in algae across the sites with wrasse less bold in Rosia Bay than the MCZ or Camp Bay. Wrasse were bolder inside the MCZ and at the beach with the highest level of anthropogenic pressure. The implications of measuring behaviour (boldness) are discussed.
The data collected in this study helps to inform relevant marine management techniques to be implemented into the Marine Strategy Framework Directive (MSFD) in BGTW to monitor and maximise the success of the MCZ and populations of wrasse and bream. Learning the in situ behavioural traits such as boldness is important when determining appropriate steps in marine management. The present study is the first study to effectively quantify impacts on abundance and behaviour of two chosen fish families and niche resource utilisation. The novel methodology presented used here is transferable worldwide to investigate faunal assemblages in all coastal ecosystems. Although the target species observed in this are all least concern, the methodology can be transferred to species that are more vulnerable and susceptible to anthropogenic impacts. The methodology and outcomes of this study could be applied to test the effectiveness of MPAs (Marine Protected Areas) but ascertaining in situ behaviour and abundances measured and quantified through the use of BRUVs. The implications presented here can improve understanding and inform local governing bodies of effective marine management and conservation practices.
Read More about Michaels research here.
Keywords: Baited Remote Underwater Video (BRUV), Wrasse, Bream, Abundance, Boldness, behaviour, Anthropogenic Impacts, Habitat Complexity, Marine Management
Quantification of pelagic and benthic fish by use of BRUVs in Gibraltar
Fish are an important component of marine habitats, generating several ecosystem services that benefit humans in addition to being an economic and food resource. Human activities and global warming have caused a major drop in their population on a global scale for many years, indicating that more protocol for monitoring population dynamics is required. Conservation and fisheries management require a thorough understanding of fish distributions in both space and time. Emerging technologies are providing new options for cost-effective ecological sampling. Baited Remote Underwater Video (BRUV) are a recent technique to monitor fish biodiversity. This approach has greatly increased in recent years due to its ease to be implemented in various type of habitat. A review of the BRUV literature found that most adopted sampling designs vary greatly depending of the project type, indicating that the method needs to be standardized. The litterature included 112 publications from 17 countries with a majority of them published from Australia as most of BRUV research are conducted in this part of the world. The publications cover every form of research that may be achieved with BRUV with a clear preference for looking at fish abundance and diversity.
Gibraltar is an English territory regarded as a biodiversity hotspot due to its abundance of marine species, particularly fish. Two locations representative of the eastern and western sides of Gibraltar were investigated using BRUV in order to study fish populations.
Samplings were conducted during 3 day and 3 nights using two types of devices (pelagic and benthic) to fully assess fish biodiversity in those sites (24 samples). The aims were to quantify the fish biodiversity to acquire a better understanding of the fish assemblage occurring in Gibraltar. As part of the specific objective from the literature review and the observations from a pilot study, the best suitable field procedures to implement BRUV survey in coastal area was created and a fish list was performed based on the footage obtain from the recording that can use be for future monitoring survey.
In order to quantify fish biodiversity, the abundance, species richness and evenness was obtained for each fish identified on the recordings using BIIGLE. Day and night fish distribution patterns were investigated by multivariate and univariate analyses. A total of 24 species with a large dominance of bream (Sparidae) accounting for 80% of the fish identified. 23531 individuals have been identified during the survey divided with 12096 in Camp Bay and 11435 in Sandy Bay. For both sites, a higher species richness was observed during the day based on the diversity index. The ANOVA performed on species richness detected significant differences between diurnal and nocturnal assemblages and position in the water column of the species whereas the one performed on fish abundance detected significant differences in the water column of the species and between site. SIMPER analysis revealed that 3 species individually Saddled Bream (34,94 %) Golden Grey Mullet (33,09 %) and Rainbow Wrasse (8,7 %), contributed by more than 76,73 % to the dissimilarity between benthic diurnal and nocturnal assemblages in Camp Bay. Considering the type of BRUV as a variable, a difference was found only during the day for Sandy Bay and Camp Bay, having a dissimilarity average of 42,02 % and 46,51 %.
The analysis of similarities found significant differences in fish biodiversity between the type of sampling used and the periods of time.
This dissertation conclude that environmental factors are the most important drivers shaping the assemblage of fish in their habitat. BRUV is a monitoring tool that shows great evidence of fish biodiversity in Gibraltar’s coastal waters, and more research in this area is needed.
Key word: BRUV’s, underwater camera, biodiversity, baited, remote, video
Primary Supervisor: Dr Awantha Dissanayake
Secondary Supervisor: Dr Jaime Davis
A survey of the richness and abundance of fish species in and around the Arch, Barranco Seco, Los Gigantes, Tenerife
The aim of the project was to gather sufficient data to determine a baseline measure of the richness and abundance of fish species in and around an underwater marine feature known as the Arch, at Barranco Seco, Los Gigantes, Tenerife. The Arch is the remains of a lava tube and has formed a natural arch underwater. A basalt rock reef stretches from the west base of the lava tube, north for about 150 m. The research site is part of a SAC which does not appear to have been monitored for species and habitat change since it was set up, so it is hoped that the results will provide up-to-date information to the local authorities for policy making. Data collection was by divers using hand-held underwater cameras swimming along the reef, and by a static camera mounted on a frame situated on the south side of the Arch. Empirical observation showed that a number of fish from a few species co-exist under the Arch. It is the objective of a longer study to determine the drivers of this behaviour, since it does not seem to be a result of predator-prey reactions or traditional safe niches for individual fish. The hypothesis was that there are a consistent number of species which congregate under the Arch. Four key species frequent the location: Guelly jacks (P. dentex), African grunts (P. octolineatum) and sardines (B. boops) school in the lower section of the west side of the Arch. Trumpet fish (A. strigosus) contain themselves to the east side of the Arch. Damselfish (A. luridus), parrot fish (S. cretense), sharpnose puffers (C. capistrata), bream (family Sparidae) and ornate wrasse (T. pavo) move through the communities and structure without being molested. Functional ecology posits that habitat complexity aids biodiversity in an area. The more complex the habitat, the more opportunities there are for species to co-exist without competing for resources. Functional divergence is the degree to which abundance of species is distributed to the extreme of the research range – an interesting possibility for future research. Unique underwater environments such as the Arch can provide ‘refuge’ in a very broad definition for species, safeguarding against extinction and providing resilience to local marine communities. It is hoped that this research and a future PhD project will contribute to the understanding of local marine environments in Tenerife.
Key word: BRUV’s
Assessment of Dentex dentex abundance and prey trophic structure in a Corsican Marine Protected Area using Baited Remote Underwater Video (BRUV) sampling
The first evaluation of the baited remote underwater video (BRUV) system for monitoring the common dentex Dentex dentex was carried out in Corsica. The collaboration with the local laboratory Stella Mare allowed the deployment of BRUVs in the Gulf of Saint-Florent, on sites sampled for several years by visual underwater survey, including a site corresponding to a No-Take Zone. 60 deployments over eleven locations, in three different sites, corresponding to 60 hours of video, made it possible to observe 37 D. dentex as well as 7356 other species of prey and predators between 15 and 54 m, thus making it possible to evaluate the fish assemblage and the prey linked to the trophic structure of the apex predator that is the dentex. Statistical analyses showed that D. dentex were observed at an average depth of 40 m in habitats composed mainly of sand and rock banks. Sardines/anchovies/smelt as well as Chromis chromis and Anthias anthias were the most abundant prey and the one contributing most to dissimilarities between sites according to the SIMPER analysis. The rarefaction curves showed that the No-Take Zone at Nonza recorded two-thirds of all species observed but was the least biodiverse site according to the Shannon and Simpson indices. Finally, the UVC data from Stella Mare indicated a greater number of D. dentex observed for a smaller number of samples (transect) than the BRUV data. However, more robust replications for BRUV (sampling over time, seasonally) are needed to conclude whether one technique is more effective than the other. This study will hopefully lead to the democratisation of population monitoring by BRUV sampling in the Mediterranean Sea on vulnerable or endangered species.
Key word: Baited Remote Underwater Video (BRUV), common Dentex, Abundance, Trophic structure, Fish assemblage, No-Take Zone, Underwater Visual Census (UVC) Marine Protected Area, Habitat Complexity, Marine Management
Assessment of marine recreational fishing effort pressure at Europa Reef; Southern Waters MCZ
Xavier Villar Buzo
Marine recreational fishing (MRF) has historically not been considered a threat to the marine environment, nevertheless recent studies have proven that MRF can be as impactful to the ocean as commercial fishing. MRF has been found to have two major ways of impacting the oceans, through the direct act of fishing and recreational vessels. This project used a new technique to assess MRFE in situ by measuring the fishing effort and vessels effort separately and later adding the number of hours to have the total effort for MRF, while at the same time comparing the fishing area with a non-take zone with BRUV deployments. The research was carried out in Gibraltar’s MCZ ER and SS. The results of this study showed an increase in fishing activity as the day went by. With little activity during the morning and most activity recorded in the evening. The total MRFE for ER was 110 hours. After compering the diversity and abundance of both sites, higher overall numbers were observed in SS (n= 6396) with a higher number of species (n=18), especially in fish species targeted by anglers. The results could indicate that Gibraltar’s MRF is having a significant impact on the reef and the process of fishing down the food web could be occurring. Without proper management the local fish stocks and the reef could be at risk. Four recommendations were made to the HM Government of Gibraltar, to ensure a healthier habitat: 1) Addressing all the impacts the MRF can have on the environment. 2) Continuous research of the fish stocks and the reef. 3) Monitoring and enforcement of the MRF through different types of surveys. 4) Non-take zone at ER, with a correct zonation that allows MRF to fish outside the buffer zone.