The invasive Indo-Pacific Lionfish Pterois volitans has been recognized as a severe threat to indigenous fish species on Caribbean reefs. Previous studies have identified an extensive variety of Caribbean fishes in the stomachs of lionfish, but few have tried to quantify the impact these invaders could have on endemic or threatened species. The threatened Labrid fish Halichoeres socialis has been identified as the primary component of lionfish diet in Belizean lagoonal reef systems. This study aims to answer two questions: what is the average maximum number of prey-fish a lionfish can consume in one sitting, and at what rate can these lionfish pass a meal of three prey fish completely? To test lionfish satiation, the subjects were fed as many Pseudohemiculter dispar (a commercially available surrogate) as they could eat within a fifteen-minute window. During the digestion rate experiment, lionfish were fed three similarly sized P. dispar and allowed to digest in 3, 6, 9, 12, 15, 19, and 24 hour blocks. From observing prey throughput under near optimal laboratory conditions, the maximum potential impact of lionfish on native populations of Caribbean reef dwelling fishes can be estimated. Given the volume and mass of prey items consumed in this study between 593 and 4658 individual H. socialis could be consumed by a single lionfish in one year. Coupled with further investigation into H. socialis stock numbers, lionfish (P. volitans) could be considered a potentially immanent threat to fishes that exhibit body morphometrics like those of H. socialis at any stage of their life-history.

Understanding and predicting the way in which species interactions may change under the uncertain climatic future is imperative if the management of important resources is to be successful. Consumer – resource interactions underlie population dynamics and distribution, yet there is little known about how these interactions will respond to increasing temperature. Temperature increase can facilitate the movement and settlement of alien species into new ranges. Introduced species can often be ecologically damaging and unpredictable due to novel predator-prey interactions. Comparative functional response analysis has been used to gain insight into resource dependent behaviour and population dynamics. This study is an assessment of the way in which predicted temperature changes can affect resource consumption in three predators. The red lionfish Pterois volitans (Linnaeus, 1758) is a successful and hugely damaging invader in the Western Atlantic and sources point to an ongoing Mediterranean invasion. Through a series of laboratory experiments I assessed how temperature, habitat complexity, and light wavelength affect the functional response of lionfish towards a crustacean prey. I establish that lionfish have a persistent Type II functional response and that lower temperature decreased the magnitude of the functional response, suggesting that movement into the comparatively colder waters of the Mediterranean and British Isles could reduce the per capita response. Further, I found that red light reduced the maximum feeding rate of lionfish, compared to blue and white light, by dampening the attack rate. I assessed how temperature increase affects the proportional consumption of an amphipod prey by an intertidal predator, the bleniid, Lipophrys pholis (Linnaeus, 1758). Functional response analysis revealed that the shanny has a hump shaped relationship with increasing temperature wherein maximum feeding rate decreased at the highest temperature. Two prey supply models, where prey density was allowed to deplete, and where prey were replaced after consumption were compared and found to have differential results due to model choice. I used gut content data to assess the abundance, prey selection, degree of dietary overlap, in a commercial predator, cod (Gadhus morhua; Linnaeus, 1758) and a non-commercial predator, dogfish (Sycliorhinus canicula; Linnaeus, 1758) with regards to substrate type. While there were no significant conclusions to be made about habitat use, I found significantly larger populations of S. canicula and higher consumption of commercial invertebrates by S. canicula. I vi used this field data to inform further experiments, having highlighted S. canicula as a potential threat to commercial fisheries. A two-by-two experimental design was used to understand how differential acclimation of predator (S. canicula) and amphipod prey species (Echinogammarus marinus; Leach, 1815) affects the functional response of the predator. Increasing temperature concomitantly increased the magnitude functional response of S. canicula, however raised temperature caused a shift in functional response type, from Type II to Type III, conferring low prey density protection. Handling time was shorter when both predator and prey were acclimated to the raised temperature and as a result there was a significant interaction effect where maximum feeding rate was significantly higher when both predator and prey were acclimated. This increase in predation impact by S. canicula has the potential to affect valuable fisheries stocks due to the increasing populations of Scyliorhinus canicula and the additive effects of acclimation to raised temperature. Having highlighted the differential ways in which temperature can affect the per capita response of consumers I postulate a new metric wherein “Relative Impact Potential” of a consumer can be predicted under a set of environmental variables. This metric takes into account the per capita response, numerical response, and the potential change in predator and prey populations under the proposed conditions. I suggest the use of this metric as a rapid way of assessing and predicting potential threats to sustainability of fisheries under predicted climatic change. Overall, this thesis identifies species and scenarios wherein sustainability of important fisheries could be threatened. While this work focuses mainly on thermal responses, it demonstrates: (i) the utility of functional response analysis in assessing relative change in ecological impact under climate change scenarios; (ii) the species specificity of thermal responses and provides empiricle evidence of a hump shaped thermal response; (iii) the importance of considering both predator and prey when assessing ecological change, with reference to acclimation and population dynamics; and (iv) a metric with which to assess potential threats and ecological impact in a way that is standardized and easily accessible by managers and stakeholders alike.

Invasive species are becoming more common as human interactions within coastal waters and the aquarium trade continues to increase. The establishment of the invasive lionfish complex Pterois volitans and P. miles from the Indo-Pacific to the Western Atlantic, Gulf of Mexico, and the Caribbean Sea has had significant negative effects on reef fish biodiversity and economically important species. Their rapid colonization and success has been attributed to their biological and ecological life history traits as well as their absence of predation. Past research has highlighted these characteristics; however, there is a knowledge gap in lionfish parasitism. This research explored the enemy release hypothesis as a key success factor in rapid establishment in the invaded range on a biogeographical scale. The diversity of lionfish parasitism was compared among 15 geographically diverse sites within the invaded range, incorporating the time of introduction at each site. Eight new parasites are described for the first time in the invasive lionfish: (1) a Cymothoid isopod: Rocinela stignata, (2) four nematodes: Raphidascais sp., Contraceacum sp., Paracuria adunca and Hysterothylaceum sp., (3) one digenean: Tergestia sp., (4) two acanthacephalans: Serracentis sp. and Dollfusentis sp., and (5) two cestodes: Nybelinia sp. and Tentacularia sp. Lionfish from the east coast of Florida exhibited the highest abundance in parasite fauna while other invaded areas yielded low abundance and diversity. Comparisons between lionfish parasitism from the past native range studies and the invaded range suggest that vectors of time, life history traits, and trophic interactions structure the lionfish parasite community. Lionfish in the Western Atlantic and Caribbean were found to be host for generalists parasite species within the coastal ecosystem. Consequently, lionfish have relatively low parasite abundance, supporting the enemy release hypothesis and its direct relation to their invasion success.

The present thesis deals with the related themes of mortality and growth in coral reef fishes. In the first chapter, a nine-year dataset from Bermuda is used to quantify how reef fish populations respond to the introduction of a trap-fishing ban, finding that herbivores exhibit extremely strong recovery, but that stock-recruitment relationships may be decoupled by a numerical response in a meso-predator. In the second chapter, a dataset from Bonaire is used to test the efficacy of the widely-used coefficient of natural mortality, M, in modelling a population of stoplight parrotfish (Sparisoma viride). As determined from simulation models, this statistical coefficient performs considerably less well than a novel mechanistic function that partitions mortality into size- and age-based processes and achieves extremely good fits to the field data. The third chapter presents a new approach to estimating growth parameters of reef fish from tagging data that exploits the disproportionate response of certain parameters to misestimates in the true age of the tagged individuals. The method works considerably better than the most widely used method when sample sizes are small, as is commonly the case in reef fish tagging studies where recapture rates tend to be low. The fourth and final chapter uses non-lethal stable isotope techniques to tease apart the invasion dynamics of Indo Pacific lionfish (Pterois spp.) that are currently colonising the wider Caribbean. The results show that lionfish exhibit habitat-specific ontogenetic shifts in prey selection, inflicting elevated mortality on small, bommie-dwelling fishes on forereefs but switching to seagrass-foraging invertivores as they grow. Lionfish also display ontogenetically shifting competition with native Nassau grouper (Epinephelus striatus), which may provide a greater barrier to invasion success on patch reefs than on fore reefs, where competitive overlap is diminished. The thesis concludes with a discussion of some lines of enquiry that could not be undertaken owing to time or data limitations, but which may hold as much interest for the reader as they do for the author.

Temperature preference, behavioral tolerance, and physiological tolerances were determined for locally captured, invasive juvenile lionfish at four different acclimation temperatures (13°C, 20°C, 25 °C and 32°C). Temperature preferences and avoidance temperatures were evaluated using an automated shuttlebox system that presents subject-driven temperature stimuli to subjects, who control the temperature with their movement throughout the tank for 12 hours. Subjects are tracked by a computer system, with data output approximately every second. Acute preference was calculated from the archived data as the mean temperature that the fish occupied during the first two hours of dynamic experimentation. Acute preference measurements were used to determine final temperature preferendum and avoidance temperatures were used to determine behavioral tolerance. Critical thermal methodology (CTM) determined the CTmin and CTmax of the lionfish with loss of equilibrium (LOE) as the endpoint. It is assumed that beyond this temperature, the fish would be unable to survive. Temperature was increased or decreased by 0.33°C per minute until the end point was reached. Thermal tolerance polygons provide a visual representation of the lower and upper thermal avoidance temperatures, delineating the thermal range of the species. Their CTmin and CTmax (acclimated to 25°C) were compared experimentally with two other Florida reef fish species (Cephalopholis cruentata and Lutjanus apodus). Acute preferences of juvenile invasive lionfish showed a final preferendum at 28.7 ± 1°C, but with no significant difference between acclimation temperatures. The thermal tolerance polygon of invasive lionfish shows a strong correlation between CTM and acclimation temperature, with the highest CTmax at 39.5°C and the lowest CTmin at 9.5°C. The thermal polygon, preference, and avoidance data describes the thermal niche of the lionfish. Lionfish CTM (24.61°C) is narrower than those of C. cruentata (25.25°C) and L. apodus (26.87°C).

Throughout the western North Atlantic Ocean, Caribbean Sea, and the Gulf of Mexico, invasive Indo-Pacific lionfish (Pterois volitans/miles) have established dense populations, greatly impacting their host environments. Lionfish tournaments have been an important tool for resource managers and other concerned stakeholders in suppressing local populations of lionfish. Tournaments can also bring economic benefits to the communities where they are held, despite this not being the primary purpose. Five derby events in Florida and the Bahamas were surveyed and 119 participants were interviewed on site, using a survey asking them to describe (1) the lionfish derby experience; (2) non-derby related lionfish removal effort; (3) derby expenditures; and (4) personal characteristics. Response rates of event participants were between 35% and 82%. Respondents spent an average of approximately $820 per person, potentially creating a net economic benefit to the communities where they were held. Total expenditures reported ranged from $5,000 to over $60,000 per tournament, with events drawing a high number of out of town participants reporting the highest amounts spent. Participants surveyed were largely males who resided in Florida and had a reported income of over $100,000 with 29% indicating an annual income of more than $200,000. In addition, lionfish tournaments have the effect of educating the public about the lionfish invasion, including greater targeting and consumption of lionfish, showing that tournaments are effective at their conservation mission as well as contributing to the economy of their host community.

Biological invasions by new species can potentially cause widespread changes in the ecological structure of a reef community including competition with indigenous species. Although their native ranges occur in the western Pacific and Indian Oceans, the red lionfish (Pterois volitans) and the devil firefish (Pterois miles) currently comprise an invasive lionfish species complex ranging from the Greater Caribbean seasonally to Maine. We focused on dietary description of Pterois sp. in Broward County, Florida due to limited information on the current invasion in the southeastern Florida reef system. Stomach contents were collected from individuals collected within a 6 km area off the coast. Dietary preference was determined using percent number, percent occurrence and percent weight, as well as the composite index of relative abundance. A shift in depth preference of lionfish was also recorded. Seasonal variance was studied and a shift in prey preference was discovered throughout the four quarterly sampling periods. A high percent teleost diet was documented during the third quarter (July-September) and a high crustacean diet in the fourth quarter (October-December). There was a 38% change in the amount of teleost prey present between the sampling events. We observed an ontogenetic shift from a mainly crustacean diet to one consisting of mainly teleost fishes: the smallest size group (5-10 cm) had a 100% crustacean diet, whereas the largest size group (35-40 cm) had a 77% teleost and 23% crustacean diet. This trend was also found to be independent of depth. This change in trophic preference in relation to size was the first documentation of this trend in Broward County, Florida.

The red lionfish, Pterois volitans, has arguably become the most successful marine invasive species to date. Yet, despite the invasion success of P. volitans, little is known about the morphology, physiology, and ecology of this species in their native and invaded habitats. The majority of recent studies have focused on the migration of P. volitans into new regions, digestion, and bacterial infections. Knowledge is lacking on the body plan of the invasive lionfish, specifically the numerous venomous spines that are protruding outward, making the body less streamlined. In this study we quantified the mechanical properties (bending and puncture) of the venomous spines of P. volitans, and related these properties to the cross-sectional morphology. We also documented variation in the cross-sectional morphology of spines from other lionfish species in their native regions. Lastly, we documented the dorsal spine joint morphology of the first three dorsal spines and the in situ range of motion as tissues were removed. We found that the long, numerous dorsal spines absorb more energy but are less stiff than the pelvic and anal spines. In addition, we found that the anal and pelvic spines are more effective at puncturing buccal skin from sharks and grouper. We found that the removal of connective tissue significantly changes lateral movement (abduction) for the first three dorsal spines. The removal of the fin sheath significantly alters forward movement (extension) for the first two dorsal spines. From morphology, mechanical property, and range of motion data for P. volitans, we propose that the numerous long dorsal spines are primarily used for intimidation, and are not as effective defense structures as the pelvic and anal spines. Having a substantial amount of intimidating, venomous spines may allow for the lionfish to conserve energy for other highly metabolically costly activities other than warding off predators, such as digestion and reproduction. Future studies could focus on the amount of venom in each spine, how long it takes for the venom to be made and replaced, how the venomous spines affect hydrodynamic flow, and in vivo range of motion during swimming and striking. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

Lionfish (Pterois spp.), an invasive species native to the Indo-Pacific, have permanently established themselves throughout the greater Caribbean, Gulf of Mexico, and regions of the Western Atlantic ranging from as far north as North Carolina to central Brazil. As their fundamental range expands, lionfish threaten to migrate into estuarine environments as they have been found to tolerate low salinities and an eclectic range of temperatures. The physiological capacity of invasion was assessed by quantifying the visual ecology of lionfish utilizing corneal electroretinography (ERG) as well as their metabolic scope and hypoxia tolerances under various temperature-oxygen-regimes utilizing intermittent-flow respirometry. Seasonal changes in temperature-dissolved oxygen levels consistent with Atlantic/Gulf of Mexico inshore estuaries not only exceed the physiological tolerances of lionfish, but also constrain metabolic scope at sub-lethal levels by significantly limiting maximum metabolic rate across all temperatures. Median Scrit values were 33%, 39%, 46%, and 54% at 15, 20, 25, and 30℃ respectively. Luminous sensitivities, temporal resolutions (Flicker fusion frequency), and spectral sensitivities scaled similarly with other estuarine piscivores indicating lionfish possess a visual system that can function effectively within estuarine photic conditions. Overall, visual characteristics of estuaries will not pose as a significant barrier to lionfish, but minimum winter temperatures and hypoxia will pose controlling and limiting factors substantially preventing further inshore invasion. However, caution should still be advised as lionfish may capitalize on specific temporal and spatial scales that provide suitable habitat quality and abundance of prey items. Further insight is needed to forecast the effects of temperature-dissolved oxygen on lionfish metabolic-scope.

With the majority of Earth’s population living in coastal areas, estuarine ecosystems have been particularly affected by anthropogenic disturbances. My dissertation research focused on three interrelated types of human disturbance that affect estuaries: Anthropogenic alteration of freshwater inflow, the introduction of invasive species, and habitat alteration. Using the LoxahatcheeRiver(Jupiter, FL) as a model system, my goal was to understand how these disturbances affect estuarine organisms, particularly fishes. One of the most ecologically harmful disturbances affecting estuaries is anthropogenic alteration of freshwater inflow (and resulting changes in salinity patterns). To identify effects of freshwater inflow on the behavior of an ecologically and economically important fish (common snook Centropomus undecimalis), I conducted a 19-month acoustic telemetry study. Common snook were more abundant and made more frequent upstream migrations during the wet season, but freshwater inflow did not appear to be the proximate cause for these behaviors. Increased estuarine salinity resulting from anthropogenic flow alteration may have facilitated the second type of disturbance that I address in this dissertation; the invasion of non-native Indo-Pacific lionfish into estuarine habitats. During the course of my dissertation research, I documented the first ever estuarine invasion by non-native lionfish. Using mark-recapture, I identified high site fidelity in lionfish, a trait that may aid future control efforts. The extremely low minimum salinity tolerance that I identified in lionfish appears to have allowed the species to colonize far upriver in estuaries with anthropogenically modified salinity patterns. Anthropogenic salinity alteration has also led to a severe degradation of oyster reef habitats in theLoxahatcheeRiver. As a foundation species, oysters provide food, shelter, and nursery habitat for a wide variety of estuarine organisms, including many ecologically and economically important fishes. Increasingly, degraded oyster reef habitats have been the focus of restoration efforts. I identified a relatively rapid (< 2 years) convergence between restored and natural oyster reef communities, and documented the importance of vertical relief in restoration success. My dissertation research is critical for the management and conservation of coastal rivers inFlorida, while more broadly informing restoration and management decisions in many other estuarine and coastal ecosystems.