Geology topics

Colin P. Shea

Publications and source records attributed to Colin P. Shea.

6 recordsLinked to original sources

USGS2025

Evaluating detection of temporal trends in long-term freshwater fisheries data to inform future monitoring efforts

Objective Florida’s Freshwater Fisheries Long-Term Monitoring Program was implemented in 2006 to track changes in freshwater fish populations and communities. As part of an evaluation of the program, this study used a simulation framework to assess trend detection for fish abundance and biomass indices and how sampling intensity (number of samples per year) and frequency (number of years) can influence detection of these trends. Methods Using count and weight data from fall electrofishing samples collected between 2006 and 2021 from 21 lakes, trends were simulated for annual mean count and weight over a 10-year period that ranged from −70% to +200%. In all, simulations were performed for seven game fish species and three management-relevant groups (large nongame, nonnative, and prey species). For sampling intensity, data were simulated with a range of sample sizes, from 10 to 40 electrofishing transects or the maximum number available for a given lake. For sampling frequency, data were simulated for different sampling schedules that included sampling 1 year followed by 1- or 2-year breaks (4–5 years of sampling in a 10-year period), sampling two consecutive years followed by 1- or 2-year breaks (6–7 years of sampling in a 10-year period), and sampling the first 5 years only. Results Simulations based on weight and count data yielded similar results, but the effect of sampling frequency and sampling schedule varied by species, management group, and lake. Trend detection was lower and more variable when mean counts and weights of fish in electrofishing samples were low. Overall, at least a 60% increase or 40% decrease over a 10-year period was typically needed for trends in mean weight and count to be detected at least 80% of the time in at least half of the lakes. Increasing sampling intensity did not substantially improve trend detection for lower-magnitude changes, but reducing sample intensity to a minimum of 10 electrofishing transects per year would have a large negative effect on trend detection in almost all lakes. Detection of trends improved as the number of years sampled increased, but ideally, sampling should be spaced throughout the entire 10-year period to capture the full magnitude of change. Sampling every year generally resulted in better trend detection and for many species and groups was the only sampling schedule that resulted in all study lakes achieving the 80% target detection level. Of the alternative schedules considered, those involving 2 years of consecutive sampling outperformed those with only 1 year of sampling followed by a 1- or 2-year break. Conclusions Relatively large changes in mean count and weight were required to detect trends over a 10-year period, but there was no clear advantage of using count or weight data for monitoring purposes. Further, study results support the current sampling intensity, but trend detection is optimized at higher mean catch and weight values. Although sampling every year is ideal, an alternative schedule involving sampling two consecutive years with 1- or 2-year breaks could be considered in certain situations. These results will be important for informing future decisions regarding Florida’s Freshwater Fisheries Long-Term Monitoring Program and other monitoring initiatives.

North American Journal of Fisheries Management.↗

USGS2021

Regional-scale variability in the movement ecology of marine fishes revealed by an integrative acoustic tracking network

Marine fish movement plays a critical role in ecosystem functioning and is increasingly studied with acoustic telemetry. Traditionally, this research has focused on single species and small spatial scales. However, integrated tracking networks, such as the Integrated Tracking of Aquatic Animals in the Gulf of Mexico (iTAG) network, are building the capacity to monitor multiple species over larger spatial scales. We conducted a synthesis of passive acoustic monitoring data for 29 species (889 transmitters), ranging from large top predators to small consumers, monitored along the west coast of Florida, USA, over 3 yr (2016-2018). Space use was highly variable, with some groups using all monitored areas and others using only the area where they were tagged. The most extensive space use was found for Atlantic tarpon Megalops atlanticus and bull sharks Carcharhinus leucas . Individual detection patterns clustered into 4 groups, ranging from occasionally detected long-distance movers to frequently detected juvenile or adult residents. Synchronized, alongshore, long-distance movements were found for Atlantic tarpon, cobia Rachycentron canadum , and several elasmobranch species. These movements were predominantly northbound in spring and southbound in fall. Detections of top predators were highest in summer, except for nearshore Tampa Bay where the most detections occurred in fall, coinciding with large red drum Sciaenops ocellatus spawning aggregations. We discuss the future of collaborative telemetry research, including current limitations and potential solutions to maximize its impact for understanding movement ecology, conducting ecosystem monitoring, and supporting fisheries management.

Marine Ecology Progress Series↗

USGS2019

Implementation of an occupancy-based monitoring protocol for a wide-spread and cryptic species, the New England cottontail Sylvilagus transitionalis

Designing effective long-term monitoring strategies is essential for managing wildlife populations. Implementing a cost-effective, practical monitoring program is especially challenging for widespread but locally rare species. Early successional habitat preferred by the New England cottontail (NEC) has become increasingly rare and fragmented, resulting in substantial declines from their peak distribution in the mid-1900s. The introduction of a possible competitor species, the eastern cottontail (EC), may also have played a role. Uncertainty surrounding how these factors have contributed to NEC declines has complicated management and necessitated development of an appropriate monitoring framework to understand possible drivers of distribution and dynamics.

Wildlife Research↗

USGS2018

Cumulative spring discharge and survey effort influence occupancy and detection of a threatened freshwater mussel, the Suwannee Moccasinshell

Freshwater mussels (Unionidae) are among the most imperiled groups of organisms in the world, and the lack of information regarding species distributions, life-history characteristics, and ecological and biological requirements may limit the protection of remaining mussel populations. We examined the influence of hydrologic factors on the occurrence of the Suwannee Moccasinshell Medionidus walkeri, a federally threatened freshwater mussel species, endemic to the Suwannee River Basin in Georgia and Florida. We also evaluated the influence of survey effort on detection of Suwannee Moccasinshell during field surveys. We compiled all recent (2013–2016) mussel survey records in the Suwannee River Basin. We calculated cumulative discharge contributed by upstream springs for each of 220 survey locations. We combined the spring discharge predictor variable with Suwannee Moccasinshell detection and nondetection data from each survey location to develop a suite of occupancy models. Modeling results indicated that detection of Suwannee Moccasinshell during surveys was strongly and positively related to survey effort. Modeling results also indicated that sites with cumulative spring discharge inputs exceeding ∼28 cubic meters per second were most likely (i.e., predicted occupancy probabilities >0.5) to support Suwannee Moccasinshell populations. However, occupancy declined in the lowermost reaches of the Suwannee mainstem despite high spring discharge inputs, presumably due to greater tidal influences and differences in physicochemical habitat conditions. Historical localities where Suwannee Moccasinshell has presumably been extirpated are all devoid of springs in their upstream watersheds. We hypothesize that springs may buffer extremely tannic, and at times polluted, surface waters, in addition to maintaining adequate flows during periods of drought, thereby promoting the persistence of Suwannee Moccasinshell populations. Our study suggests that springs are a critical resource for Suwannee Moccasinshell and may be more important for conservation planning than was previously recognized.

Florida↗

USGS2016

Multispecies cccupancy modeling as a tool for evaluating the status and distribution of Darters in the Elk River, Tennessee

Sixteen darter species, including the federally endangered Boulder Darter Etheostoma wapiti , are known to occur in the Elk River, a large, flow-regulated tributary of the Tennessee River, Tennessee–Alabama. Since the construction of Tims Ford Dam (TFD) in 1970, habitat modification caused by cold, hypolimnetic water releases and peak-demand hydropower generation has contributed to population declines and range reductions for numerous aquatic species in the main-stem Elk River. We developed Bayesian hierarchical multispecies occupancy models to determine the influence of site- and species-level characteristics on darter occurrence by using presence–absence data for 15 species collected from 39 study sites. Modeling results indicated that large-river obligate species, such as the Boulder Darter, were 6.92 times more likely to occur for every 37-km increase in the distance downstream from TFD. In contrast, small-stream species were 2.35 times less likely and cosmopolitan species were 1.88 times less likely to occur for every 37-km increase in distance downstream from TFD. The probability of occurrence for darter species also had a strong negative relationship with the absence of cobble and boulder substrates and the presence of high silt levels, particularly for species that require boulder substrates during spawning. Although total darter species richness was similar across all 39 sample sites, the composition of darter assemblages varied substantially among locations, presumably due in part to species-specific habitat affinities and hydrothermal conditions. The use of multispecies occupancy models allowed us to account for the incomplete detection of species while estimating the influence of physical habitat characteristics and species traits on darter occurrences, including rarely observed species that would have been difficult to model individually.

Tennessee↗

USGS2011

Misidentification of freshwater mussel species (Bivalvia:Unionidae): Contributing factors, management implications, and potential solutions

Surveys of freshwater mussel populations are used frequently to inform conservation decisions by providing information about the status and distribution of species. It is generally accepted that not all mussels or species are collected during surveys, and incomplete detection of individuals and species can bias data and can affect inferences. However, considerably less attention has been given to the potential effects of species misidentification. To evaluate the prevalence of and potential reasons for species misidentification, we conducted a laboratory-based identification exercise and quantified the relationships between mussel species characteristics, observer experience, and misidentification rate. We estimated that misidentification was fairly common, with rates averaging 27% across all species and ranging from 0 to 56%, and was related to mussel shell characteristics and observer experience. Most notably, species with shell texturing were 6.09× less likely than smooth-shelled species to be misidentified. Misidentification rates declined with observer experience, but for many species the risk of misidentification averaged >10% even for observers with moderate levels of experience (5–6 y). In addition, misidentification rates among observers showed substantial variability after controlling for experience. Our results suggest that species misidentification may be common in field surveys of freshwater mussels and could potentially bias estimates of population status and trends. Misidentification rates possibly could be reduced through use of regional workshops, testing and certification programs, and the availability of archived specimens and tissue samples in museum collections.

Journal of the North American Benthological Societ↗