In an effort to determine the optimal temperature for rearing Centropomus undecimalis larvae during the yolk resorption period, larval development was measured under four different temperature regimes (23, 25, 28 and 31 °C). The eggs were incubated at 28 °C until hatching, which occurred at about 17 hours post-fertilization. After hatching, temperatures were adjusted to the respective treatment levels. Measurements were collected from 25 individual larvae across rearing temperatures at the following pre-determined time intervals: at hatching, 24 hours post hatch (hph), 48 hph, and 72 hph. Morphometric measurements were obtained from photomicrographs, including yolk sac length and height, oil globule diameter, standard length, body height at anal pore, and eye diameter. Larvae in the 25 °C treatment had longer median standard length, body height, and more energy reserves than those larvae reared at other temperatures. The yolk sac and oil-globule were present up to 72 hph at 23 and 25°C, while these were entirely consumed after 48 hph in treatments at 28 and 31 °C. Centropomus undecimalis larvae had the highest growth rates during the first 24 hph, and this period corresponded to the highest energy consumption as determined by the decrease in yolk-sac and oil-globule volume. Survival was assessed during the third trial only. The 31 °C treatment presented the worst survival percentages, with a maximum survival of 37.2% at 24 hph, and 100% mortality at 72 hph. The 25 °C treatment featured higher survival at the end of the trial than the other treatments with 1.7% survival. Eye diameter didn't vary significantly with time and was not a useful parameter for tracking development during yolk resorption. These results led to the conclusion that 25 °C was the optimal temperature to raise snook larvae during the yolk-resorption period.

Atlantic tarpon are sought after because of their fighting ability on various tackle and support a popular, lucrative and predominantly catch-and-release recreational fishery in Florida. They are not commercially harvested or consumed by the general public, therefore assessing effects of catch-and-release angling on tarpon survival is critical to a sustainable fishery. Tarpon caught on artificial breakaway jig and traditional live bait fishing charters in Boca Grande Pass (n=42) and trips from the recreational fishery of Tampa Bay (n=40) were tagged with ultrasonic transmitters and tracked up to 6 hours immediately following release to estimate post-release mortality. Of the 82 tagged tarpon, 11 suffered mortality as inferred from movement patterns (or lack thereof) or visual confirmation (i.e. shark attacks) which yields a combined total estimated catch-and-release mortality rate of 13% (95% confidence interval: 6-21%). There was no significant difference in mortality between the two estuarine systems. Associations between tarpon mortality and angling duration, handling time, fish length, bait type (artificial versus natural), and hook type (circle versus "J") were not significant. Hook location (foul-hooking) and swimming condition at release were significant factors on tarpon mortality (P<0.05). Shark predation was the primary cause of post-release mortality (64%). Excluding predation, the overall mortality rate was estimated at 5% and attributed to poor handling and irreparable physiological damage from angling. Angling events will cause anaerobic activity resulting in physiological disruptions that may have consequences compromising the health and survival of tarpon. Both adult (mature, >70 pounds, 31.8 kg) and sub-adult (sexually immature, <20 pounds, 9 kg) tarpon support Florida's recreational fishery, so maximizing post-release survival and minimizing sub-lethal stress effects of both size classes are critical to their sustainability. In this study, stress responses after exhaustive exercise (angling) were measured using an array of blood chemistry parameters, including hematocrit, hemoglobin, and plasma glucose, lactate, sodium, potassium, chloride, calcium, phosphorus, magnesium and cortisol. Angled, adults (n=45) were compared to large tarpon in a resting state (controls, n=6). Angled, sub-adults (n=28) were compared to those in a resting state (n=9). Adult tarpon were then compared to sub-adults to determine any size-related, intra-species variation in stress responses after angling. Finally, because smaller tarpon are logistically easier to handle and may be subjected to prolonged air exposure by anglers for hook removal or photographs, we evaluated the effect of 60 seconds of air exposure with horizontal (n=9) or vertical (n=9) handling out of the water relative to non-air exposed (n=10) fish in angled sub-adult tarpon. Associations and interactions among the blood chemistry responses of tarpon from each treatment to angling duration, handling time, body size and environmental factors related to each capture event were evaluated using a non-parametric, multivariate redundancy analysis. The duration of the angling event had a positive effect on responses of some parameters, and responses were more extreme in adult tarpon than sub-adults. The exception was cortisol which was significantly higher in sub-adults. Environmental parameters were less influential than angling and handling on observed physiological responses. Sub-adults showed no difference in physiological responses among handling treatments with and without air exposure and exhibited no short term mortality. Using appropriate tackle and gear to reduce fight times and handling should help minimize metabolic and acid-base imbalances. Tagging studies coupled with physiology can be a valuable tool for estimating post-release mortality and secondary stress responses of game fish, especially for large species that might be difficult to maintain in floating pens or tanks. Yet adverse effects of catch-and-release angling could also have population level consequences. Future studies should integrate biology and fish physiology to evaluate post-release recovery windows and establish lethal thresholds to provide potential predictive capability of mortality. In general, it appears that sub-adult and adult Atlantic tarpon along the Gulf coast of Florida can recover from physiological disturbances incurred during routine catch-and-release angling events in the recreational fishery when they are released in the absence of large predators. The anglers themselves can play a key role in tarpon conservation.

The objectives of this study were to measure injuries and impairments directly observed from gags Mycteroperca microlepis caught and released within a large-scale recreational fishery, develop methods that may be used to rapidly assess the condition of reef fish discards, and estimate the total portion of discards in the fishery that suffer latent mortality. Fishery observers were placed on for-hire charter and headboat vessels operating in the Gulf of Mexico from June 2009 through December 2012 to directly observe reef fishes as they were caught by recreational anglers fishing with hook-and-line gear. Fish that were not retained by anglers were inspected and marked with conventional tags prior to release. Fish were released in multiple regions over a large geographic area throughout the year and over multiple years. The majority of recaptured fish were reported by recreational and commercial fishers, and fishing effort fluctuated both spatially and temporally over the course of this study in response to changes in recreational harvest restrictions and the Deepwater Horizon oil spill. Therefore, it could not be assumed that encounter probabilities were equal for all individual tagged fish in the population. Fish size and capture depth when fish were initially caught-and-released also varied among individuals in the study and potentially influenced recapture reporting probabilities. The Cox proportional hazards regression model was used to control for potential covariates on both the occurrence and timing of recapture reporting events so that relative survival among fish released in various conditions could be compared. A total of 3,954 gags were observed in this study, and the majority (77.26%) were released in good condition (condition category 1), defined as fish that immediately submerged without assistance from venting and had not suffered internal injuries from embedded hooks or visible damage to the gills. However, compared to gags caught in shallower depths, a greater proportion of gags caught and released from depths deeper than 30 meters were in fair or poor condition. Relative survival was significantly reduced (alpha (underline)<(/underline)0.05) for gags released in fair and poor condition after controlling for variable mark-recapture reporting rates for different sized discards among regions and across months and years when individual fish were initially captured, tagged and released. Gags released within the recreational fishery in fair and poor condition were 66.4% (95% C.I. 46.9 to 94.0%) and 50.6% (26.2 to 97.8%) as likely to be recaptured, respectively, as gags released in good condition. Overall discard mortality was calculated for gags released in all condition categories at ten meter depth intervals. There was a significant linear increase in estimated mortality from less than 15% (range of uncertainty, 0.1-25.2%) in shallow depths up to 30 meters, to 35.6% (5.6-55.7%) at depths greater than 70 meters (p < 0.001, R2 = 0.917). This analysis demonstrated the utility of the proportional hazards regression model for controlling for potential covariates on both the occurrence and timing of recapture events in a large-scale mark-recapture study and for detecting significant differences in the relative survival of fish released in various conditions measured under highly variable conditions within a large-scale fishery.

Thesis (Ph.D.)--Flinders University, School of Biological Sciences. / Typescript bound. Includes bibliographical references: (leaves 149-166) Also available online.

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.

The goal of this thesis was to adopt a reverse flow injection analysis (rFIA) technique to the fluorometric analysis of the reaction o-phthaldialdehyde (OPA) with ammonium, allowing accurate measurements of ammonium concentrations lower than the detection limit of the widely used indophenol blue (IPB) colorimetric method while accounting for the background fluorescence of seawater. Ammonium is considered an essential nutrient for primary productivity, especially in the nutrient depleted surface ocean where as the most reduced form of dissolved inorganic nitrogen, it is readily assimilated via metabolic pathways. Challenges in the quantification of ammonium require more sensitive analytical techniques for a greater understanding of the biogeochemical cycling of ammonium in the oligotrophic ocean. On-line and automated flow analysis techniques are capable of mitigating some of the challenges. Fluorescent-based methods out-perform colorimetric methods in terms of detection limits and sensitivity. Presented here is the development of an rFIA technique paired with an OPA-sulfite chemistry. For this method, a sulfite-formaldehyde reagent is mixed with the sample stream and then injected with the OPA reagent before being heated. Fluorescence is measured before and at the peak of the OPA injection, differentiating the background fluorescence from the analyte signal. Experiments to optimize reaction parameters and characterize the effects of salinity and potentially interfering species were conducted. The newly developed method offers a reasonable throughput (18 samples per hour), low limit of detection (1.1 nM) ammonium analysis technique with automatic background fluorescence correction suitable for oligotrophic seawater as a preferable alternative to the low sensitivity and high limit of detection IPB colorimetric method.

Forecasting the potential range of invasive species is a critical component for risk assessment, monitoring, and management. However, many of these invasive species are not yet at equilibrium which can be problematic for many modelling approaches. Using the climate matching method, MaxEnt, a series of species distribution models (SDMs) and risk analysis maps were created for select apple snail species in Florida: Pomacea canaliculata, P. diffusa, and P. maculata. Apple snails, freshwater gastropods in the family Ampullariidae, are native to South America and were introduced to the United States via the pet trade approximately 40 years ago. These highly invasive species have already been introduced in ten states and established in at least seven. The models and risk analysis in this study show the majority of Florida was at least moderately suitable for all apple snails modeled, with P. maculata posing the greatest threat.

Aquaponics, the integrated production of fish and hydroponic crops in a recirculating system, is an intensive cultivation method in which metabolic fish wastes fertilize plants. This study compares the effects of two aquafeeds on Red amaranth (Amaranthus tricolor) productivity and on water quality under cultivation of Blue tilapia (Oreochromis aureus), with three aquaponic units (n=3) per treatment over a 60-day trial. The fishmeal-based control feed contains higher crude protein (40%) and phosphorus (1.12%) than the plant-based alternative feed (32% and 0.40%). The alternative feed resulted in a significantly higher amaranth crop yield (p

Local ecological knowledge (LEK) is a useful method to capture environmental or resource changes when there is an absence of biological data. Since the bonefish fishery is data limited, this study aims to understand the trend of bonefish decline over the last 40 years using LEK and to assess whether varying fisher experience and fisher type would influence perception of bonefish decline. Semi-structured surveys and key informant interviews were conducted to collect LEK data. Along with perceiving an overall decline (p

Novel ecosystems emerge from alterations to historic abiotic regimes and contain new species combinations. Everglades canals offer an opportunity to understand the function of novel habitat for native and non-native fishes and how novel conditions in turn influence distribution, abundance and assembly patterns. I examined native and non-native fish assemblages collected across a gradient in novelty, defined by the loss of wetland connectivity and habitat complexity. As novelty increased, native species richness and abundance strongly declined, and the contribution of non-natives increased. Community structure vastly differed among canals and was strongly influenced by spatial factors and secondarily by hydrological factors. Natives and non-natives had opposing responses to key hydrologic and habitat parameters. This study represents the first comprehensive assessment of Everglades canal fishes, providing insight into the factors influencing native and non-native abundance and assembly patterns and contributing to our understanding of this novel but permanent habitat.