► Species-environment model for juvenile spotted seatrout
Cynoscion nebulous was developed. ► Fish occurrence was linked to salinity, temperature, and distance from tidal inlets. ► Frequency of ...occurrence was highest from May to October.
Long-term, fisheries-independent bag seine surveys conducted in TX, USA estuaries from 1977 to 2009 were used to develop a spatio-temporal species-environment model for juvenile spotted seatrout,
Cynoscion nebulous. Relationships between environmental predictors and juvenile spotted seatrout distribution were investigated using boosted regression trees (BRTs). Results showed good model performance and suggested that, in relation to environmental factors, juvenile spotted seatrout distribution is most closely linked to salinity, temperature, and distance from tidal inlets. There was also a strong seasonal pattern where abundance increased from May to October and declined precipitously after November. Juveniles were rarely captured between January and April. By interpolating the environmental predictors, monthly maps of the probability of capture were produced using ordinary kriging. Spatial patterns were also evident. Probability of occurrence began increasing first in Upper Laguna Madre peaking in Baffin Bay. Probability of occurrence was consistently higher in this region than other regions within the study area. Predicted occurrence was also high in portions of Corpus Christi, Aransas, San Antonio Bays, and the southern portion of Galveston Bay. Overall, probability of occurrence increased with increasing distance from tidal inlets. The development of spatially explicit models allows for prioritization and conservation of areas in a region that has great potential for human disturbance and climate change impacts.
Increases in standardized catch per unit effort (CPUE) and mean length of bull shark (Carcharhinus leucas) were observed in coastal estuaries over a 35-year period (1976-2010). Trends in abundance ...and size were examined using fisheries- independent data from a long-term monitoring survey in Texas, USA. Catch, effort, and environmental covariates that affect bull shark distribution were used to create a standardized index of abundance. Increases in abundance and mean length were detected, potentially due to the initiation of federal management and restrictions on the use of gill nets in nearby Louisiana, USA, waters in 1995. This study provides a long-term perspective of two important demographic indicators (abundance and mean size) of bull shark and provides an encouraging signal in the Gulf of Mexico for a species whose stock status is unknown yet considered near threatened on the International Union for Conservation of Nature red list. Continuing research is needed to gauge effects of management and environmental impacts on shark resources as well as investigations into ecosystem effects of increasing predatory density in coastal waters.
Microbial monitoring in marine recreational waterways often overlooks environmental variables associated with pathogen occurrence. This study employs a predictive boosted regression trees (BRT) model ...to predict Staphylococcus aureus abundance in the Tampa Bay estuary and identify related environmental variables associated with the microbial pathogen’s occurrence. We provide evidence that the BRT model’s adaptability and ability to capture complex interactions among predictors make it invaluable for research on microbial indicator research. Over 18 months, water samples from 7 recreational sites underwent microbial quantitation and S. aureus isolation, followed by genetic validation. BRT analysis of S. aureus occurrence and environmental variables revealed month, precipitation, salinity, site, temperature, and year as relevant predictors. In addition, the BRT model accurately predicted S. aureus occurrence, setting a precedent for pathogen–environment research. The approach described here is novel and informs proactive management strategies and community health initiatives in marine recreational waterways.
Linking trends in fish population abundance to environmental characteristics is often difficult because fish use avariety of habitats throughout their ontogeny and may exhibit large interannual ...fluctuations in abundance. Wedeveloped a two-stage boosted regression tree model to investigate spatiotemporal patterns of Southern Flounder Paralichthys lethostigma abundance and distribution in Texas estuaries. We used a 36-year fishery-independent data set (1977–2012) to correlate distribution with environmental conditions and seasonal or long-term changes in abundance. Adult Southern Flounder were sampled with gill nets using a random-stratified design. Predictions of abundance were made to grids of environmental data to identify “hot spots” as well as seasonal or decadal shifts in distribution. Models were fit using cross validation, and variance was estimated using nonparametric bootstrapping. Depth, temperature, distance to a tidal inlet, and salinity were the primary environmental determinants of Southern Flounder distribution and abundance. Because distribution and response to environmental conditions can depend on population abundance, we also developed a standardized index of annual abundance using the same two-stage boosted regression tree model. The index identifies a long-term decline in abundance punctuated by recent recovery (possibly in response to management actions). Mapped results identify a coastwide decline in abundance between 1980–1984 and 2005–2009 but the magnitude varied substantially, suggesting disproportionate changes in abundance across the study area.
An increase in infections from non-fecal coliforms worldwide has caused concern that monitoring fecal coliforms overlooks pathogens that are not primarily associated with feces. A potential ...alternative to fecal coliforms is Staphylococcus aureus and methicillin resistant S. aureus (MRSA). The overall goal of the project was to quantify spatial patterns of an important opportunistic pathogen species of bacteria (S. aureus and MRSA) and to examine antibiotic susceptibility related to discharge into the Hillsborough River. There was a high presence of S. aureus and MRSA from all sites. Of the seven sites sampled, the site closest to Tampa General Hospital (site seven) had the lowest quantity of S. aureus but the highest percentage of MRSA. Whereas the site closest to The University of Tampa (site one) had the highest quantity of S. aureus and the lowest amount of MRSA. While Staphylococcus aureus was detected at significantly higher amounts during wet (rain) events, there was no correlation between these events and higher amounts of MRSA. These results suggest there is a potential correlation in the relationship of the quantity of S. aureus and antibiotic susceptibility (MRSA) of the isolates by location of discharge into the Hillsborough River. The results from this study are a good starting point to understanding the spatial patterns of S. aureus and MRSA in the Hillsborough River and gives us a platform for continued work.
Southern Flounder Paralichthys lethostigma supports a multimillion dollar commercial and recreational fishery in the Gulf of Mexico. Despite its economic importance, the Southern Flounder population ...has been declining for decades. To improve the management of this fishery, both population trends and changes in environmental conditions need to be considered. Using two different statistical modeling techniques, boosted regression tree (BRT) and artificial neural network (ANN), a 29-year fisheries-independent record of juvenile Southern Flounder abundance in Texas was examined to illustrate how environmental factors influence the temporal and spatial distribution of juvenile Southern Flounder. Boosted regression trees show the presence of juvenile Southern Flounder is closely associated with relatively low temperatures, low salinity levels, and high dissolved oxygen concentrations. Both ANN and BRT models resulted in high predictive performance with slight spatial differences in predicted distribution. Both models suggested high probability of occurrence in Galveston Bay and East Matagorda Bay. The ANN accurately predicted higher probability of occurrence in Sabine Lake compared with the BRT model. Our results will provide tools for fisheries managers to enhance management and sustainability of the Southern Flounder population. Moreover, these results also identify a predictive framework for proactive approaches to ecosystem management by providing more data to identify essential habitat features and understanding relationships between abiotic and biotic factors within those habitats.
A long-term fisheries independent data set (1975–2008) was used to assess population trends of juvenile and adult southern flounder (
Paralichthys lethostigma) along the Texas coast in the northern ...Gulf of Mexico, USA. The dataset contained a total of 46,784 sites that were sampled with bag seines to monitor small nekton abundance and 22,870 sites that were sampled with gill nets to assess adult fisheries trends. These data were examined for age-specific population trends using generalized least squares and extended with non-parametric bootstrapping to obtain interval estimates of regression parameters (juveniles) and linear regression (adults). These data showed long-term declines in juvenile southern flounder abundance (1.3% per year). For adult southern flounder, rate of decline was much more rapid (2.5% per year). Results suggest that survival of post-juvenile flounder has decreased during the time series. This precipitous decline has prompted increasingly stricter harvest restrictions along the Texas coast. However, these management measures have been insufficient to curb declines.
The goal of this study was to use an ecosystem-based approach to consider the effect of environmental conditions on the distribution and abundance of juvenile bay whiff and southern flounder within ...the Aransas Bay Complex, TX, USA. Species habitat models for both species were developed using boosted regression trees. Juvenile bay whiff were associated with low temperatures (<15 °C, 20–23 °C), moderate percent dry weight of sediments (25–60 %), salinity >10, and moderate to high dissolved oxygen (6–9 mg O 2 /l, 10–14 mg/l). Juvenile southern flounder were associated with low temperatures (<15 °C), low percent dry weight of sediment (<25 %), seagrass habitat, shallow depths (<1.2 m), and high dissolved oxygen (>8 mg O 2 /l). Our results indicate that conservation measures should focus along the eastern side of Aransas Bay and the north corner of Copano Bay to protect essential fish habitat. These findings provide a valuable new tool for fisheries managers to aid in the sustainable management of bay whiff and southern flounder and provide crucial information needed to prioritize areas for habitat conservation.
Microbial monitoring in marine recreational waterways often overlooks environmental variables associated with pathogen occurrence. This study employs a predictive boosted regression trees (BRT) model ...to predict Staphylococcus aureus abundance in the Tampa Bay estuary and identify related environmental variables associated with the microbial pathogen’s occurrence. We provide evidence that the BRT model’s adaptability and ability to capture complex interactions among predictors make it invaluable for research on microbial indicator research. Over 18 months, water samples from 7 recreational sites underwent microbial quantitation and S. aureus isolation, followed by genetic validation. BRT analysis of S. aureus occurrence and environmental variables revealed month, precipitation, salinity, site, temperature, and year as relevant predictors. In addition, the BRT model accurately predicted S. aureus occurrence, setting a precedent for pathogen–environment research. The approach described here is novel and informs proactive management strategies and community health initiatives in marine recreational waterways.
Declines of important fish species such as southern flounder, Paralichthys lethostigma, in the Gulf of Mexico underscore the importance of defining critical habitats as well as the processes ...contributing to habitat value. Southern flounder is a valuable commercial and recreational fishery, distributed from North Carolina to Florida on the Atlantic Coast and from Florida to Northern Mexico on the Gulf Coast. Despite the economic and ecological importance of southern flounder, current management efforts failed to recover a sharp population decline and restore back to a historical level. Therefore, it is important for resource managers to understand and predict the future status of juvenile southern flounder. The overall purpose of this study was to provide research data and decision tools needed for development of a fishery management plan for flounders by using statistical modeling techniques. A long-term fisheries independent data set (1975–2008) from Texas Parks and Wildlife Department fisheries monitoring program was used to assess population trends of juvenile and adult southern flounder along the Texas coast in the northern Gulf of Mexico, USA. These data were examined for age-specific population trends using generalized least squares and extended with non-parametric bootstrapping to obtain interval estimates of regression parameters (juveniles) and linear regression (adults) and showed long-term declines in juvenile southern flounder abundance. For adult southern flounder, rate of decline was much more rapid. Results suggest that survival of post-juvenile flounder have decreased during the time series. This precipitous decline has prompted increasingly stricter harvest restrictions along the Texas coast. However, past management measures have been insufficient to curb declines, and it is too early to assess the recent regulations. To develop a predictive species habitat model delineating critical areas for nursery habitat field collections of juvenile bay whiff and southern flounder were collected from February to May 2010 within the Aransas Bay Complex. To determine the mechanism of habitat selection the "best" species habitat model for both species was identified using BRT. Ten predictors were included in the model: habitat type, dry weight, depth (m), dissolved oxygen (mg O 2/L), temperature (°C), turbidity (cm), salinity, pH, distance to the inlet, and month. Species habitat model for juvenile bay whiff indicated that bay whiff were not associated with any particular habitat type, but were associated with low temperatures (< 15°C), moderate percent dry weight of sediments (25–60%), salinity >10 psu, and moderate to high dissolved oxygen (6–9 mg/L, 10–14 mg/L). Species habitat model for juvenile southern flounder indicated that southern flounder were associated with low temperatures (<15°C), low percent dry weight of sediment (<30 mg/L), seagrass habitats, shallow depths (<1.2 m), and high dissolved oxygen (>8 mg/L). Results suggest EFH within the Aransas Bay Complex needs to occur among all habitat types along the eastern side of Aransas Bay, and the north corner of Copano Bay. The findings will provide a valuable new tool for fisheries managers to aid sustainable management of bay whiff and southern flounder and the Mission-Aransas Reserve ecosystem and provides crucial information needed to prioritize areas for habitat conservation and management in the Gulf of Mexico. Modeling approaches using BRT and ANN were constructed to understand how environmental factors influence the temporal and spatial patterns of juvenile southern flounder throughout all of the major Texas bays. Data were acquired from the Resource and Sport Harvest Monitoring Program conducted by Texas Parks and Wildlife Department. The BRT model indicated juvenile southern flounder were associated with low temperatures, low salinity levels, and high dissolved oxygen. Both spatio-temporal models (BRT and ANN) consisted of high predictive performance with slight spatial differences. Both models suggest high probability of occurrence in Galveston Bay and East Matagorda Bay whereas the Artificial Neural Network also indicated high probability of occurrence in Sabine Lake. (Abstract shortened by UMI.)
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