Mark-recapture surveys implementing photographic identification techniques were used to estimate the abundance of bottlenose dolphins in an area of the Big Bend of Florida, stretching from St. Vincent Sound to Alligator Harbor, in the summer of 2007 and winter of 2008. The current population size of individuals in this region is unknown as the most recent abundance estimates were calculated based on aerial surveys conducted in 1993. Recent large scale mortality events, together with an increasing potential for human impacts in this area, warrant an updated and increased understanding of the abundance and stock structure of dolphins in this region. Because the region is large and recent work here suggests that at least two distinct communities exist in these waters, the region was divided into the two areas in which these communities appear to reside (St. Vincent Sound/Apalachicola Bay and St. George Sound/Alligator Harbor) and independent estimates of abundance were calculated for each area and each season. Closed-population models in the program CAPTURE were used to derive the estimates of abundance and the assumptions underlying each model were examined. The estimates calculated from the models selected as being the most appropriate for each data set were similar for each survey area for each season: in the St. Vincent Sound/Apalachicola Bay survey area 182 ± 58 animals inhabited the survey area in the summer and 178 ± 77 animals in the winter; in the St. George Sound/Alligator Harbor survey area 365 ± 164 animals inhabited the survey area in the summer and 359 ± 87 animals in the winter. Results from this study also provided further evidence that at least two communities reside in these waters as only 2.4% of animals captured during the study were captured in both survey areas. If indeed two communities exist in these waters, it appears that site-fidelity and/or residence patterns of individuals may differ between them; in the St. Vincent Sound/Apalachicola Bay survey area 49.6% of the total animals captured were captured more than once and 29.6% were captured both seasons, while in the St. George Sound/Alligator Harbor survey area 35.3% were captured more than once and 13.8% of animals were captured both seasons. In addition, it appears that the St. George Sound/Alligator Harbor survey area supports a greater number of transient animals than the St. Vincent Sound/Apalachicola survey area (46.1% of distinctive animals were seen only once versus 29.9% respectively). This may be due in part to this survey area being more accessible to the open waters of the Gulf of Mexico than the St. Vincent Sound/Apalachicola Bay survey area, which is more protected by barrier islands. The results provided here can be used by the National Marine Fisheries Service to aid in their stock-assessment process and help in the management of the animals in this region. / A Thesis submitted to the Department of Oceanography in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Fall Semester, 2008. / Date of Defense: August 5, 2008. / Abundance Estimate, Mark-Recapture, Photo-Identification, Bottlenose Dolphin / Includes bibliographical references. / Douglas Nowacek, Professor Co-Directing Thesis; William Dewar, Professor Co-Directing Thesis; Randy Wells, Outside Committee Member; Jeffrey Chanton, Committee Member.

No description available.

The distribution of Antarctic Intermediate Water in the South Pacific has been examined using a model of horizontal advection, along the Sigma-t surface 27.10, with three point vertical mixing. The core of the Antarctic Intermediate Water mass was traced from the Antarctic Convergence northward. The charts used to describe the distribution were those of core depth, salinity, percentage composition, Equivalent Thickness, and acceleration potential. The percentage composition of Antarctic Intermediate Water in the entire water column for all stations was computed and the Equivalent Thickness determined. Intermediate water volume for the South Pacific was then calculated. North-South geostrophic velocities and transports were computed for two zonal sections. The model agreed quite well with the flow patterns reported by other investigators. The broad counterclockwise gyre in the central South Pacific, the flow into the Tasman and Coral Seas, the localized flow near New Zealand, and the suggestion of southward flow near the South American Coast are all indicated by the model. A previously unreported small, counterclockwise gyre in the southeast South Pacific was detected. The circulation within the small gyre is consistent wity flow over a variable bottom in the Southern Hemisphere. Antarctic Intermediate Water transport across selected sections indicate a northward flow of 10 x 10⁶ m³ sec⁻¹. A low salinity tongue was found on the salinity chart. This tongue extended northward, then westward, into the northern Tasman Sea. The salinity was over 34.50°/₀₀ in the center of this counterclockwise motion east of New Zealand. The isohalines in the southeast Pacific suggest the presence of the small counterclockwise gyre. A 20 percent drop in core percentage composition was noted in the 10 degrees north of the Antarctic Convergence. A large uniform area between 80 percent and 70 percent over the central portion of the central South Pacific was bounded on the north by a 20 percent drop near the equator, again supporting the general counterclockwise circulation. The Equivalent Thickness distribution showed a general lenticular shape, the thickest part lying in the center of the counterclockwise gyre east of New Zealand. The Equivalent Thickness distribution, as well as the core percentage, supported the hypothesis of little or no flow into the Tasman Sea from the south. The volume of intermediate water obtained from surface area integration of the Equivalent Thickness distribution was 59.44 x 10⁶ km³. This is approximately 16% of the water volume in the South Pacific. / Graduation date: 1972

Thesis (M.S.)--Oregon State University, 1977. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.in Physical Oceanography)--Naval Postgraduate School, September 2003. / Dissertation supervisor: Mary L. Batteen. Includes bibliographical references (p. 109-123). Also available online.

Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, March 2003. / Thesis advisor(s): Peter C. Chu, Steve Haeger. Includes bibliographical references (p. 79). Also available online.

Fish otoliths are composed of inorganic calcium carbonate that aid in gravity and auditory reception. Substances permanently accrete to otolith surfaces in distinct temporal patterns of alternating opaque and translucent rings; these rings are direct proxies for a fishs age. The objective of my research is to demonstrate how otoliths can be used through time and space to estimate both age and growth of fish. I investigated the spatial differences in age distributions and growth models for red snapper, Lutjanus campechanus, at four natural shelf-edge reefs in the northwestern Gulf of Mexico. Red snapper cohorts ranged 1987-2010 cohorts, with the majority (91.69%) of individuals between 4 to 9 years (2001-2009 cohorts) of age. The mean age across all sites was 7.2 years, and the modal age was 6 years. The 2006-year class dominated the distribution (22.98%) and the modal cohort was 2005. Differences in the von Bertalanffy growth parameter k were not detected despite significant differences in mean-size-at age in older age classes. Results suggest that habitat quality may be paramount in investigating red snapper demographics at shelf reefs. In addition, I investigated the temporal differences in freshwater drum Aplodinotus grunniens, age and growth estimates between ancient and modern freshwater drum populations. Ancient otoliths were recovered from shell middens associated with the Tchefuncte culture and the modern otoliths were collected from the commercial fishery in southeastern Louisiana between 1987-1989. Ancient otoliths were radiocarbon dated to 650 BCE, separating the two populations by ~2,600 years. Both populations exhibited a truncated age structure but significantly differed in age frequency distributions and mean age estimates. Mean otolith weight-at-age estimates were similar when plotted against biological age. Estimates of growth rates were difficult to obtain due to low sample sizes in young and older freshwater drum age-classes and the interment of ancient otoliths. Results suggest that mean otolith weight-at-age may be the most appropriate method for modeling growth. Furthermore, fishery exploitation and fisher gear selectivity may have been similar between the Tchefuncte and modern commercial fishers, despite the common assumption that ancient fish populations reached greater sizes-at-age and exhibited faster growth rates.

There has been relatively little study of the efficacy of decommissioned oil and gas platforms as artificial reef habitats for fish assemblages in the northern Gulf of Mexico (GOM). A variety of fish species have been reported on these structures, but the species biomass distribution and community structure has not been studied thoroughly. Hydroacoustic and video surveys were conducted quarterly from June 2013 to June 2014 at three standing and two toppled oil and gas platforms located approximately 130 km off the coast of Louisiana at 90 m depth; to gain information about the spatial biomass distribution and community structure at standing and toppled platforms. The toppled platforms in our study became a part of the Louisiana Artificial Reef Program in 2002. Stereo and Go-Pro® cameras were utilized for video surveys, allowing us to record counts and lengths of fishes. Hydroacoustic surveys were used to define the spatial distribution of fish biomass (MVBS, SV) in relation to distance to 500 m from the center of each site and the depth distribution of the observed biomass. MVBS of fishes was highest when near the structure and declined rapidly as distance from the structure increased, leveling off to a background-noise level at 100 m from the structure. Additionally, fish MVBS was highest in the lower water column (>60 m) compared to the upper and middle water columns. The fish communities differed between depth layers in the water column, seasonally, and between structure types (standing/toppled), with red snapper (Lutjanus campechanus) as a dominant species present at both site types. Coupling the data from these methods revealed that even though fish MVBS remained consistent throughout all seasons, different species comprise the MVBS observed during different seasons and between different layers in the water column. Coupling non-destructive methods allows for rapid monitoring which can be helpful in determining how to effectively manage both the fishes around the structure and the structures themselves.

Spotted seatrout (Cynoscion nebulosus) are a highly sought after sportfish, making up over 90% of the recreational fishery in Louisiana. As a significant portion of every life history stage is spent within its natal estuary, it is an ideal bio-indicator of estuarine health. As one of the largest estuaries in Louisiana, Lake Pontchartrain represents one such supporting ecosystem. From November 2012 to April 2014 acoustic tagging of individual fish, a lake-wide receiver array, and ArcGIS mapping software were utilized to determine the spatial distribution of spotted seatrout within the lake. Receivers were placed in representative locations including man-made and natural structures. The prevalence of fish hot spots, between these locations were compared and thus bottom habitat preferences examined. Water quality parameters, including water temperature, dissolved oxygen, salinity, turbidity, colored dissolved organic matter, chlorophyll a, and hydrocarbons are biochemical factors with the potential to drive the species distribution. As such, a flow-through water sampling system was used to obtain monthly snapshots of conditions across the lake. Combined with presence/absence receiver data, any water quality preferences were examined. Overall, spotted seatrout showed a distinct preference for the central, central-north, and northeastern areas of the lake. It was also noted, however, that the species showed no distinct preference for a single bottom type, but utilized every habitat in the lake. With respect to water quality, salinity and temperature were determined to be the most important features for the species distribution. According to the generalized linear model produced, every unit increase in salinity (ppt) improved the odds of observing a spotted seatrout by almost five times while a unit increase in temperature improved the odds by approximately 11 percent. The above results are in agreement with the extensive literature on the species and its relationship to bottom types and water chemistry, but still leave questions of habitat use/preference in relation to the potential influences of life stage adaptations, availability of food resources, food web dynamics, or major environmental events. Future research in these areas will serve as important additions to the ecosystem-based strategy of management for this valuable Louisiana fishery.

Nearshore Louisiana has experienced substantial changes within the last half-century, including the annual formation of the worlds second largest hypoxic zone and the construction of thousands of oil and gas platforms (rigs). Ship Shoal and its rigs may provide important substrate in nearshore Louisiana because rigs act as de facto artificial reefs and the shoals bottom waters were well oxygenated on 43% of days when surrounding areas were hypoxic. From July to September of 2014, fish assemblages and hydrography were compared at shoal rigs, rigs inshore of the shoal, and rigs offshore of the shoal, and stone crab populations were compared at rigs on and off the shoal. A camera array and YSI sonde were used to characterize fish assemblages and hydrography at shoal rigs, rigs inshore, and offshore of the shoal. Stone crab densities were estimated with visual counts, and their life history was characterized by removing a subsample of stone crabs for identification and measurements. Fish assemblage composition was significantly different between shoal rigs, rigs inshore, and rigs offshore of the shoal (P<0.05). The most notable difference between assemblages was greater contribution of demersal fishes at shoal rigs than rigs inshore and offshore of the shoal. Hypoxia was intermittent at shoal rigs and persistent at rigs inshore and offshore of the shoal. Mean hypoxia thickness (meters of hypoxic water) was significantly greater (P<0.05) at rigs inshore (2.6 m) and offshore of the shoal (3.1 m) than it was at shoal rigs (0.6 m). Crab densities were roughly twice as high on as they were off the shoal (mean 4.0 vs. 1.8 stone crabs/m2; P<0.05), and the carapace width where 50% of females were ovigerous was 26.4 mm smaller for females off than on the shoal (P=0.057). Shoal rigs and rigs in surrounding waters provide important substrate for reef- associated organisms, although higher contribution of demersal fishes and densities of SCs at shoal rigs than rigs in surrounding waters suggest that shoal rigs are of higher relative importance. These findings suggest that further mining of Ship Shoal and removal of rigs may be detrimental to reef-associated organisms in nearshore Louisiana.