Differences in coral reef fish assemblages were investigated on six South African and one southern Mozambican reef under varying management regimes. All of the South African reefs fall within marine protected areas (MPA) but are zoned for differing types and intensities of human activity. Reefs where no human activities are allowed were termed Sanctuaries, while those on which restricted fishing and SCUBA diving are permitted were termed Protected. The reef in southern Mozambique is subjected to unrestricted fishing and SCUBA diving and was consequently termed Open. This study consists of two parts. The first dealt with a community assessment which investigated and provided baseline data on the trophic structure, density, and species diversity of fish assemblages on each of the seven study reefs. The objective was to compare the aforementioned metrics between reefs and thereafter compare them between the different protection zones. The second part of this study focused on assessing the impacts of human activities using 25 fish indicator species. These species were selected a priori based on their ecological importance and sensitivity to human activity (fishing and diving). The selection process was then guided by the results of the community assessment. The objective was to use these species as indicators of recreational diving and fishing pressure in the different protection zones. Density, biomass and size frequency analyses comprised the primary metrics in this assessment. Randomly stratified underwater visual censuses (UVC) were used to collect the fish data and these were conducted on reefs inhabited by a coral community considered to be the core community on South Africa’s reefs in terms of biodiversity and coral cover. The fish community assessment consisted of timed counts in which all non-cryptic fish species were quantified. Indicator species counts employed the point count technique with a radius of 10 m. An average of 11 community counts and an average of 62 point counts were conducted per reef. Various environmental variables and habitat characteritics were recorded during the UVCs. Multivariate analysis of the fish assemblages indicated that the fish community structure differed significantly according to reef protection status. Sanctuary reefs were significantly different from the Open reef in Southern Mozambique. Mean fish abundance was highest on Sanctuary reefs and lowest on the Open reef. In terms of overall species diversity, a total of 284 species belonging to 50 families were recorded, this being comparable to other reefs in the WIO region. Six families contributed more than 50% towards the fish community composition: Labridae, Acanthuridae, Chaetodontidae, Lutjanidae, Pomacentridae and Serranidae. All predator categories were well represented on Sanctuary reefs, while top-level predators were scarce on the High-Diving and the Open reef. Generalised linear model (GLM) regression analysis indicated that human activities were significant variables in accounting for the variance in fish community structure. The total fish abundance and biomass of the selected indicator species were significantly higher in Sanctuary zones and lowest in the Open zone. In addition, Sanctuary zones were characterised by high numbers of large predators, while non-Sanctuary zones were characterised by higher abundances of prey species. Target species were also larger and more abundant in Sanctuary zones. The data revealed that recreational fishing and high diving intensity may be influencing the fish community structure on southern African coral reefs, which was confirmed by GLM regression analysis. Long-term monitoring of these fish communities is recommended to confirm the trends observed in this data set. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2010.

This study used trapping and visual census surveys to assess whether a marine reserve in Barbados effectively protected coral reef fish stocks and whether there was evidence of emigration from the reserve. Fish abundance and sizes were higher in the reserve than in surrounding non-reserve areas. Relative differences in abundance and size between reserve and non-reserve of different taxa were positively correlated to vulnerability to traps (the most common fishing method) but not to mobility of fish. Gradients of abundance across the reserve boundaries (decreasing abundance with distance from the reserve center) were apparent for total abundance but not for individual taxa. These patterns suggest that the reserve does protect fish stocks and that emigration is of minor importance.

Thesis (M.A.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains vi, 36 p. : ill. (some col.), col. map. Includes abstract. Includes bibliographical references (p. 31-36).

Coastal infrastructure has replaced many vital fish nursery habitats with structures designed without fully mitigating for the loss of the natural ecosystems. This thesis details research focused on the use of small, inexpensive, artificial reef modules as replacement juvenile fish habitat within marinas. My research hypothesis was that the placement of small, structurally complex artificial reef modules would increase fish abundance and species richness relative to unmodified marina seawalls. Non-destructive visual surveys of fishes were completed monthly for 14 months for 12 artificial reef sites and 12 control (unmodified) sites within the Nova Southeastern University Guy Harvey Oceanographic Center (NSU-GHOC) marina. Divers recorded species, abundance, and size class (0-2 cm, >2-5 cm, >5-10 cm, >10-20 cm, >20-30 cm, >30-50 cm, >50 cm) for all sites. Data was statistically analyzed using analysis of variance (ANOVA) and post-hoc Student Newman-Keuls (SNK) tests to explore differences in mean abundance, mean species richness, and mean abundance and species richness by size class and month. Total mean fish abundance and mean species richness (all months and sizes combined) were both significantly higher at artificial reef sites than at control sites. Artificial reef sites were consistently higher in total abundance and species richness when analyzed by month. Analysis of mean abundance by size class found the >2-5 cm, >5-10 cm, >10-20 cm and >20-30 cm classes were significantly higher for artificial reef sites. Species richness analysis by size class found classes >2-5 cm, >5-10 cm, >10-20 cm, and >20-30 cm were significantly higher at artificial reef sites. Fishes from the grunt (Haemulidae) and snapper (Lutjanidae) families contributed the most to the total abundance for both types of sites. These results support my hypothesis and have important implications for mitigating ecological impact to coastal fish nursery areas with the use of artificial structure.

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Ecologists have long questioned why fluctuating populations tend to persist rather than go extinct. Populations that persist indefinitely are regulated by mechanisms that cause demographic density dependence, which works to bound fluctuation above zero. In a series of studies, I have sought to determine the processes and mechanisms that regulate local populations of coral-reef fish. In the Exuma Keys, Bahamas, fairy basslets (Gramma loreto) live in aggregations on the undersides of coral-reef ledges. These aggregations often constitute local populations because movement between aggregations is rare. The largest individuals occupy prime feeding positions near the front of ledges and force smaller individuals remain near the back where they have lower feeding rates. Based on these initial observations, I designed two experimental studies of the demographic consequences of variation in basslet density. In the first study, I manipulated the density of newly-settled fish to explore the effects of high recruitment on population size. Populations with experimentally elevated recruitment converged in density with unmanipulated populations, primarily due to density-dependent mortality. I found no evidence that density dependence was caused by intraspecific competition; rather it appeared to be due to a short-term behavioral response by predators (aggregative and/or type 3 functional response). In a second study, I manipulated the densities of adults among populations with a standard average density of newly-settled fish. Two measures indicated that the intensity of competition increased at higher densities of adults, which likely made small fish more susceptible to predation, thereby causing density-dependent mortality. Long-term observations indicated that basslet populations were regulated at temporal scales exceeding two generations. At Lizard Island on the Great Barrier Reef, I also examined how patterns of recruitment of coral-reef fishes were modified across a range of natural recruit densities in the presence and absence of resident predators. Predators decreased recruitment and increased mortality for all species, but these effects varied considerably among species. The results of each of these studies stress the importance of both competitive and predatory mechanisms in modifying patterns of abundance established at the time of larval settlement, as well as regulating local population size. / Graduation date: 2002

Herbivory is a key process that mediates the abundance of primary producers and community composition in both terrestrial and aquatic ecosystems. On tropical coral reefs, changes in herbivory are often related to phase shifts between coral-dominance and dominance by seaweeds, or foliose macroalgae. Resilience or capacity to resist and reverse such phase shifts is, therefore, viewed as a critical function on coral reefs. This thesis used grazer exclusion and assay experiments at six sites within three different fisheries management regimes in Kenya to identify the impacts of herbivores (sea urchins and fishes) on algal dynamics in the context of coral reef resilience. First, I examined the grazing rates necessary to prevent phase shifts by quantifying consumption and algal production. Here, I found that, over a 390-day experiment, at least 50 percent of algal production must be consumed to avoid accumulation of algal biomass. Using video observations, I also showed that scraping parrotfishes remove more algae (per unit of fish biomass) than previously assumed, and that sea urchins, if released from predation, have similar impacts to fishes. Then I focused on algal succession, and found that sea urchins and fishes have different effects that are mediated by their abundances and species composition. Where sea urchins were less abundant and parrotfishes absent (e.g. young fisheries closures), progression of algae from turfs to early and then late successional macroalgae occurred rapidly and within 100 days. I then turned my focus to the removal of already established macroalgae (grown for > 1 yr in the absence of herbivores) and showed that sea urchins and browsing fishes were able to remove significant amounts of macroalgae where either herbivore was abundant. However, using multiple-choice selectivity assays and in situ video recordings, I found that browsing fishes fed very selectively with low overlap in diet among species, leading to low functional redundancy within a high diversity system. Finally, using long-term survey data (from 28 sites) to build a 43-year chronosequence, I showed that it is possible that the effects of herbivory will not be constant across transitions from open fishing to fishery closures through non-linear grazing intensity. Therefore, increases in herbivory within fisheries closures may not be immediate and may allow a window of opportunity for algae to go from turf to unpalatable macroalgae until scraping and browsing fishes fully recover from fishing (~ 20 years). The findings in this thesis are novel and raise concern over the potential implications of the slow recovery of parrotfishes or, given lower than expected functional redundancy in grazing effects, the absence of even one browsing fish species in fisheries closures. Overall, this thesis highlights the importance of herbivore community dynamics in mediating interactions among algae, and provides new insights for conservation and management actions that attempt to bolster the resilience of coral reefs.

Coral reefs around the world are threatened by a variety of sources, from localized impacts, including overfishing and coastal development, to global temperature increases and ocean acidification. Conserving these marine biodiversity havens requires both global and local action informed by scientific research. In this thesis, I use data collected from the coral reefs around Kiritimati atoll (Republic of Kiribati) in the central equatorial Pacific, first to assess the applicability of two common metrics used in passive underwater acoustic research, and second to examine the effects of a marine heatwave and local human disturbance on an assemblage of corallivorous fish. Using acoustic data recorded in 2017 and 2018 on reefs around Kiritimati, I assess how sound pressure level (SPL) and the acoustic complexity index (ACI) respond to changes in fish sounds in a low frequency band (160 Hz – 1 kHz) and snapping shrimp snaps in a high frequency band (1 kHz – 22 kHz). I found that while SPL was positively correlated with increases in fish sounds and snap density, changes in ACI were dependent upon the settings chosen for its calculation, with the density of snaps negatively correlated with ACI across all settings. These findings provide evidence that despite its quick and prolific adoption, acoustic metrics like ACI should be thoroughly field-tested and standardized before they are applied to new ecosystems like coral reefs. Next, using underwater visual censuses (UVCs) of reef fish assemblages, I quantified how two functional groups of corallivores, obligate and facultative, responded to a mass coral mortality event created by the 2015-2016 El Niño. Declines in abundance of both groups were largely driven by the response of coral-associated damselfishes, Plectroglyphidodon johnstonianus in the obligate group and Plectroglyphidodon dickii in the facultative group, to heat stress and subsequent coral mortality. I also observed a significant decline in the species richness of obligate corallivores, and a continued decline in the abundance of obligate corallivores three years after the mass coral mortality event. Additionally, facultative corallivore abundance increased with disturbance, although the effect was modulated by year, likely due to their more adaptable diets. Corallivore assemblage structure was also influenced by the heat stress event, recovery, and local human disturbance. These results detail how an entire corallivorous assemblage is impacted by a coral mortality event and incidentally provide a timeline for corallivore decline. Together, these results provide information about new ways of monitoring coral reefs, and the ways in which two components of the reef fish community, obligate and facultative corallivores, respond to a mass coral mortality event. / Graduate / 2022-01-15

Coral reefs are being negatively impacted by various causes worldwide, and direct intervention is often warranted following disturbance to restore or replace lost ecosystem structure and function. An experimental coral reef restoration study involving standardized artificial reef modules (ReefballsTM) was conducted in Mexico’s Yucatan Peninsula in the towns of Puerto Morelos and Akumal. The purpose was to explore the use of artificial structure for restoration and mitigation applications in a highly diverse and dynamic Caribbean coral reef environment by applying and evaluating the performance of select experimental treatments hypothesized to accelerate development of the associated biota. The first treatment consisted of invertebrate enhancing artificial substrate padding material, which provided structurally complex refuge space for mobile epifaunal/infaunal invertebrates and other benthic organisms. The second treatment consisted of coral transplants, intended to provide additional structural complexity and kick-start development of stony coral populations. The third treatment consisted of settlement plates which were intended to provide data on coral recruitment and survival rates. Multiple hypotheses relating to the interactions between experimental treatments and the resulting macroalgal, non-coral invertebrate, stony coral, and coral reef fish assemblages were examined, and comparisons were made between natural and artificial substrates. In Puerto Morelos there were 40 modules; 10 controls and 10 of each of 3 treatments: substrate pads, coral transplants, and settlement plates. In Akumal there were 12 modules; 6 controls and 3 of each of 2 treatments: substrate pads and settlement plates. Following module deployment, 6 biannual monitoring trips were made over the course of three years to assess the development of the biota, with a final 7th trip made six years post-deployment. Divers conducted non-destructive visual surveys to evaluate total abundance, species richness, size class distribution, and assemblage structure of coral reef fishes. Other monitoring work included coral recruit surveys, mobile epifaunal invertebrate collections from substrate pads, and digital imaging of coral transplants, natural reef reference corals, and benthic quadrat areas. Hurricane Dean compromised the Akumal study site during the first year of the study, but Puerto Morelos was unaffected. There the modules developed biotic assemblages that differed from what was found on the natural reef, and the data suggests that the substrate pads may have had an effect on the development of faunal assemblages. Lobophora variegata macroaglae and Desmapsamma anchorata sponge were the major contributors to benthic community composition, and both had significantly greater coverage on the substrate pads treatment modules. Lobophora grew rapidly and peaked within the first year, while sponges increased steadily throughout the first three years of the study, surpassing the coverage of macroalgae before the end of the second year, much to the detriment of coral transplants and many coral recruits. By the end of the study, over 75% of the transplants were overgrown by D. anchorata, and density of new coral recruits on the Pads treatment modules was lower than the other treatments and controls. Coral recruitment was dominated by Porites astreoides on all treatments and controls, and the number of corals increased steadily throughout the study. The controls had consistently greater numbers of corals than the treatments, as well as lower percent coverage of macroalgae and sponges. Total abundance and species richness of reef fishes was generally unaffected by the treatments. However, at the family and species level, several differences were detected, particularly for the substrate pads treatment and to a lesser extent for the coral transplants treatment. For future restoration or mitigation efforts utilizing similar or identical treatments to artificial substrates, this study suggests that, in the absence of routine maintenance, greater success may be achieved after waiting several years post-deployment for the initial wave of unchecked growth by benthic organisms (i.e., macroalgae and sponges) to reach a balance point before a large investment of resources is devoted to coral transplanting. Further recommendations include routine monthly or quarterly on-site maintenance to enhance transplant survival, as well as a longer monitoring window to assess community development in response to experimental treatments. The results of this study suggest that the experimental treatments did indeed have an effect on the biota, but whether or not the effect was beneficial largely depends upon perspective. The Pads treatment in particular had the greatest effect on both reef fish and benthic community development, however, it was not beneficial for stony coral recruitment. Additional research is needed to fully understand the long-term performance and effects of the padding material on biotic assemblage development for future restoration or mitigation projects.