Browsing by Subject "Aransas Bay"

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The Effect of Environmental Factors on Chorusing Activity of Soniferous Fishes in Aransas Bay, Texas
(2022-05-17) Saldeen, Jonathan
Several species of fish and other aquatic organisms use sound for communication, reproductive signaling and larval recruitment. Soniferous fishes can be monitored using passive acoustic monitoring (PAM). Some species of fish who use sound to reproduce take part in an activity researchers call “chorusing”, which is when a large number of individuals form spawning aggregations and emit noise for a sustained period of time. The species examined in this study are Pogonias cromis (Black Drum), Bairdiella chrysoura (Silver Perch), and Cynoscion nebulosus (Spotted Seatrout). By combining analysis of environmental data and PAM, I studied how changing environmental conditions can affect chorusing species of fish. This study used sound recordings of the aquatic environment from hydrophones mounted on the NERR SWMP station in Aransas Bay, Texas. Environmental data was also collected from the SWMP station in Aransas Bay, Texas. The environmental data collected included water temperature, conductivity, salinity, dissolved oxygen, depth, pH, turbidity, chlorophyll fluorometry, air temperature, barometric pressure, and lunar phase. The data was analyzed using generalized additive modeling (GAM) to determine the marginal effects of the environmental variables on chorusing activity. Water temperature was found to be the most significant predictor of chorusing activity for all three species, and was the only predictor all three species had in common. This finding is especially important in the face of anthropogenic climate change as rapidly changing temperatures could have a significant impact on spawning activity.
Freshwater contributions and nitrogen sources in a South Texas estuarine ecosystem : a time-integrated story from stable isotope ratios in the eastern oyster (Crassostrea virginica)
(2012-05) Bishop, Karen Anne; McClelland, James W.; Dunton, Kenneth H.; Walter, Benjamin
Changes in freshwater inputs due to water diversions and increased urbanization may alter the function and properties of estuarine ecosystems in South Texas. Freshwater and nitrogen inputs from the Mission and Aransas rivers to the federally designated Mission-Aransas National Estuarine Research Reserve (Mission-Aransas NERR) have received considerable attention in the past few years. However, freshwater inputs from two rivers (the San Antonio and Guadalupe rivers) that combine and drain into a neighboring bay (San Antonio Bay) may also provide a substantial nitrogen source to Aransas Bay, which is within the boundaries of the Mission-Aransas NERR. In order to study the influence of the San Antonio and Guadalupe rivers, an oyster species, Crassostrea virginica, was chosen to provide time-integrated information about freshwater contribution as a nitrogen source within the bays. Chapter One addresses variations in isotope values ([delta]¹⁵N and [delta]¹³C) in oyster adductor muscle tissue from 2009-2011 along a sampling transect from the head of San Antonio Bay through Aransas Bay. Stable carbon isotope values increased linearly from approximately -25 % to -17 %, while stable nitrogen isotope values decreased from approximately +16 % to +10 % along this transect. The patterns in stable carbon and nitrogen isotope values are consistent with substantial mixing of river-supplied water and nitrogen from San Antonio Bay into Aransas Bay. Variations in nitrogen isotopic signature between periods of sustained drought and flood conditions were relatively small, suggesting that riverine nitrogen contributions were similar regardless of the amount of freshwater inflow observed during the time frame of this study. Chapter Two addresses the isotopic equilibration time for adult oyster adductor muscle tissue using a year-long transplant experiment (November 2010-November 2011). Full representation of ambient water isotopic composition in oyster adductor muscle tissues was determined to occur roughly a year after transplant. Oyster adductor muscle could therefore be useful for long-term monitoring of nitrogen contribution from freshwater sources, and would be valuable to include in concert with water sampling and analysis of other tissues that have shorter integration rates for a comprehensive view of an estuarine system.
Seasonal variations and trophic relationships among concentrated populations of small fishes in seagrass meadows
(1983) Huh, Sung-Hoi; Kitting, Christopher L.; Wohlschlag, Donald E. (Donald Eugene), 1918-2007
Temporal and experimental changes in populations of potential competitors, their resources used, and their available resources can illustrate periods of competition. Dense populations and foods of small fishes were analyzed during 1982-1983 for day-night and monthly changes in an assemblage concentrated naturally in seagrass meadows of Redfish Bay, Texas. Samples totalled 10,223 fishes, in 23 families and 40 species. Fish densities averaged 15.1/m² in shoalgrass and 6.2 individuals/m² in turtlegrass meadows, which were somewhat deeper. The darter goby, pinfish, code goby, and Gulf pipefish were the most common fish species in both shoalgrass and turtlegrass meadows throughout the year. The darter goby predominated in shoalgrass, while the pinfish and code goby predominated in turtlegrass meadows. No clear day-night differences in densities of each common fish were detected during most of the year. Peak abundance of total fishes occurred during spring, with a secondary peak in fall and a minimum in winter. Each of the four common species showed its own seasonal abundance pattern, and had a different larval recruitment and peak abundance separated 1-3 months from other species, with some overlap. Seasonal feeding data for the four most abundant fish species were compared with respect to prey availability to illustrate how resource partitioning of food could mediate possible competition among these abundant consumers. When prey (mainly amphipods) were abundant, during spring, many fish species showed high overlap in food use. Regardless of food availability, the code goby and Gulf pipefish fed mainly on amphipods and copepods. The more common darter goby and pinfish were carnivorous during spring, but they showed herbivorous feeding habits during summer, when they consumed mainly epiphytic algae during periods of lower prey availability. These changes in resource use also resulted during depletion of major foods by fishes concentrated experimentally in cages. These shifts in diets reflect a temporary partitioning of available foods. Different seasonal abundance patterns with different times of peak recruitment among seagrass fish species thus seem to permit use of the seagrass meadow habitats with reduced, seasonal competition for major foods among these concentrated fishes