Raw underwater videos 'Baited Remote Underwater Video' (BRUV). The video material is many Terabytes large.
Please contact the DCBD administrator for access to video material.
Sababank sample videos provided by Jelmer Pander (2013).
When overly abundant, macroalgae can be a major threat to the health of a coral reef ecosystem due to its capability to smother live coral and reduce the rates of recruitment. Several factors can contribute to macroalgal growth, one of the controlling elements being a lack of herbivorous grazing. When grazing pressure is high the ecosystem remains balanced, but when grazing pressure is low reefs can experience macroalgal blooms that have a lasting negative effect. This study examined the indirect causes of macroalgal cover change through assessing damselfish aggression. Stegastes planifrons, also known as the Three Spot Damselfish, are highly aggressive and territorial fish that will defend their territories against a number of intruding species. This study looked at the relationship between damselfish abundance and aggression and the grazing behavior of parrotfish, as well as the relationship between damselfish abundance and macroalgal cover on Bonaire, Dutch Caribbean. Video transects were implemented over the chosen study stations and then analyzed with Coral Point Count (CPCe) software to attain the percentages of macroalgae cover at each station. Aggressive behavior of the three spot damselfish as well as the grazing behavior of parrotfish were observed and recorded using SCUBA diving. It was found that damselfish aggression and parrotfish grazing were negatively correlated, and that parrotfish grazing followed the same trend line as the macroalgae cover. Based on the findings of this study it was concluded that S. planifrons aggression has no considerable effect on the grazing behavior of parrotfish,and it can be assumed that it does not contribute to increased macroalgal cover.
This student research was retrieved from Physis: Journal of Marine Science XIX (Spring 2016)19: 16-21 from CIEE Bonaire.
Many environmental variables may influence fish assemblage structures in terms of abundance, biomass and mean size. The aim of this study is to provide a baseline survey on reef fish assemblages and shark presence covering the whole Saba bank (Dutch Caribbean). Hereby determining the influence of habitat, depth and fishing pressure on the structure of reef fish assemblages and shark presence. Baited Remote Underwater Video (BRUV) survey was used to describe reef fish assemblage structures on the Saba bank. Between 2012-2014, a total of 165 60 min BRUV deployments were conducted on locations varying in habitat complexity (0-4, Polunin and Roberts, 1993), depth (15-40m) and fisheries. The eleven most abundant fish species observed on the Saba bank represented eight families and accounted for nearly 50% of the total number of individual fish observed. Labridae was the most abundant fish family observed with a relative abundance of 22%. Most abundant fish species by number of individuals were Thalassoma bifasciatum (N=849 (9.8%)) Stegastus partitus (N=725 (8.4%)) and Acanthurus bahianus (N=430 (5.0%)).
Habitat complexity was positively correlated with species richness (Nsp), fish abundance (MaxN), and mean biomass, and negatively correlated with mean fish length. Strongly developed vertical relief habitats were found to support high numbers of fish species (N=19.1±0.6SE) of relatively low mean lengths (22.4cm±0.3SE), whereas less complex habitats were characterized by low numbers of species (N=8.3±0.8SE) with relatively high mean lengths (24.6cm ±0.81SE). Depth was negatively correlated with Nsp, MaxN and mean biomass and positively correlated with mean fish length. These relationships were all according to expectations based on earlier studies.
A minor part of the variability in the structure of reef fish assemblages was explained by differences in fisheries activity, indicating that no clear fisheries effect was observed in fish assemblages in this study. Furthermore, no significant differences in average size of target species were observed between areas with different fishing pressure. However, the general absence of piscivores such as large snappers and groupers was an indication of the indelible effects of past fisheries on the Saba bank.
A total of 85 shark observations were made with Ginglymostoma cirratum as most abundant species (N=41), followed by Carcharhinus perezii (N=36), Galeocerdo cuvier (N=5) and Carcharhinus limbatus (N=3). Relatively high shark abundances (0.20 sharks hour-1) were observed on the Saba bank compared with other Caribbean regions (The Bahamas: 0.14 sharks hour-1, Belize, 0.17 sharks hour-1). Shark abundance (CPUE) was positively correlated with habitat complexity, whereas depth exerted a negative influence on shark abundances. High shark numbers are a good sign for the health of the Saba Bank ecosystem, since sharks are apex predators, making them a prime indicator for ecosystem health.
Besides ‘traditional’ measures, ecomorphology was presented as an alternative measure in explaining variation in reef fish assemblages. For ecomorphological analysis insight in trophic morphology was obtained by using a Fish Food Model (FFM). The FFM in this study quantitatively related properties of 14 marine food types to morphological characterics of 15 common fish species on the Saba bank and predicted the capacity of utilizing these food types for each species. Strong differences in morphology and little overlap was observed for all different fish species in the FFM-analysis, which was mainly explained by two sets of variables involving predatory and herbivorous lifestyle. By multiplying each species’ capacity of using food types with its abundance an ecomorphological profile of each fish assemblage was calculated. On a functional level reef fish assemblages showed less variability than on species composition level, this possibly is an indication for high levels of robustness in niche differentiation in reef fish communities on the Saba bank.