Threadfin Shad Research Articles

First records of threadfin shad (Dorosoma petenense Günther, 1867) in the upper Delaware River estuary indicate northward range expansion

First records of threadfin shad (Dorosoma petenense Günther, 1867) in the upper Delaware River estuary indicate northward range expansion

A Spatiotemporal History of Key Pelagic Fish Species in the San Francisco Estuary, CA

Estuaries across the globe have been subject to extensive abiotic and biotic changes and are often monitored to track trends in species abundance. The San Francisco Estuary has been deeply altered by anthropogenic factors, which is reflected in substantial declines in some native and introduced fishes. To track trends in fish abundance, a multitude of monitoring programs have conducted regular fish surveys, some dating back to the late 1950s. While these surveys are all designed to track population-scale changes in fish abundance, they are methodologically distinct, with different target species, varying spatial coverage and sampling frequency, and different gear types. To compensate for individual survey limitations, we modeled pelagic fish distributions with integrated data from many sampling programs. We fit binomial generalized linear mixed models with spatial and spatiotemporal random effects to map annual trends in the spatially explicit detection probabilities of striped bass, Delta smelt, longfin smelt, threadfin shad, and American shad for the years 1980 to 2017. Overall, detection probability has declined by approximately 50% for striped bass and is now near zero for the two smelt species, while threadfin shad and American shad have both experienced fluctuations with only slightly reduced detection probabilities by 2017. Detection probabilities decreased dramatically for these fishes in the Central and South Delta, especially after the year 2000. In contrast, Suisun Marsh and the North Delta acted as refuge habitats with reduced levels of decline or even increased detection probabilities for some species. Our modeling approach, using disparate datasets, demonstrates the simultaneous spatially driven decline of pelagic fish species in a highly altered estuary.

Does invasion by armored catfish shift trophic ecology of native fishes? Evidence from stable isotope analysis.

Popular as aquarium fish, armored catfishes from South America (Pterygoplichthys spp.) have been introduced and become invasive in tropical and subtropical regions worldwide. These ecosystem engineers can deplete basal resources (e.g., periphyton and detritus), with potential negative effects for native fauna. We studied the trophic ecology of fishes in the Usumacinta River Basin, Guatemala, where Pterygoplichthys is now widespread and locally abundant. We analyzed stable isotopes (δ13 C, δ15 N) in fish tissues and basal resources to assess the potential impact of Pterygoplichthys on the trophic ecology of six co-occurring native fishes that feed at a similar trophic level (Astyanax aeneus, Dorosoma petenense, Thorichthys pasionis, Oscura heterospila, Poecilia mexicana, and Gambusia sexradiata). The study was conducted during the dry season in the La Pasion (LPR; high invasion) and San Pedro (SPR; low invasion) rivers. We compared isotopic spaces occupied by native fish and Pterygoplichthys, estimated isotopic overlap, and evaluated the trophic displacement of native species. We also evaluated the relationships of environmental factors, including the relative biomass of the invasive catfish, with δ13 C and δ15 N signatures. Except for P. mexicana, native species had lower isotopic overlap with the catfish in LPR. Native fish isotopic spaces were compressed and shifted toward higher trophic positions in LPR relative to SPR. Benthic food resources were important for Pterygoplichthys in both rivers, and water-column resources had greater relative importance (RI) for native species in LPR. Native fish δ13 C was significantly associated with Pterygoplichthys biomass, conductivity, and water flow velocity; and water depth and sedimentation had a significant association with native fish δ15 N. Findings provide evidence that invasive Pterygoplichthys, along with environmental factors, impact the trophic ecology of native fish in the Usumacinta Basin. Additional field research conducted over longer time periods and mesocosm experiments that account for fish assemblage and environmental variation could elucidate Pterygoplichthys impacts via food resource depletion or habitat alteration.

Incorporating expanded sampling into an alternative abundance index for the Fall Midwater Trawl survey

The Fall Midwater Trawl (FMWT) Survey has been conducted near continuously since 1967 to assess the abundance and distribution of pelagic fish species throughout the San Francisco Bay/Sacramento-San Joaquin estuary (Bay Delta). For most of this period, sampling 100 core stations provided data for abundance and distribution analyses. Another 22 (non-core) stations were added to the FMWT 8 to 28 years ago to supplement the original 100 (core) stations. However, relative abundance indices are published annually from only the data collected at the core stations. Here we incorporate data from non-core stations along with core station data to calculate an alternative index that also integrates modern estimates of water volume within the Bay Delta into an index calculation. The use of data from non-core stations in calculating the alternative index was particularly useful for American Shad (Alosa sapidissima) and Threadfin Shad (Dorosoma petenense). Consistently high catches at non-core stations for a couple species and modest catches for a couple additional species highlight the value of these additional catch data for our understanding of how fishes are distributed in the estuary.

Isotopic niches of Silver Carp and two native planktivores in a large reservoir

Human-mediated biological invasions can greatly reduce native species diversity. More than 138 nonnative fishes have been introduced to the United States. Many of these nonnative species can alter ecosystem dynamics and compete with native species. The planktivorous Silver Carp (Hypophthalmichthys molitrix Valenciennes in Cuvier and Valenciennes, 1844) is a nonnative species of concern that is currently expanding its range across the Greater Mississippi River Basin in the Midwestern United States. The objective of our study was to determine the degree of potential competition among invasive Silver Carp and the native planktivores, Gizzard Shad (Dorosoma cepedianum Lesueur, 1818) and Threadfin Shad (Dorosoma petenense Günther, 1867), in Kentucky Lake, a large reservoir located in western Kentucky and Tennessee. We used data derived from N and C isotopes to model isotopic niches, calculate quantitative metrics to describe variability within and among isotopic niches and trophic positions, and qualitatively assess seasonal shifts in trophic positions. Our results suggest that in the spring, older (≥1 y old) Silver Carp share resources with older and young-of-year (YOY; <1 y old) Gizzard Shad, whereas YOY Silver Carp only share resources with YOY Gizzard Shad. Additionally, our analyses showed that older Silver Carp and older Gizzard Shad share resources in the summer. In contrast, we found no overlap in resource use between YOY Threadfin Shad and YOY or older Silver Carp. Furthermore, we provide evidence of intraspecific ontogenetic shifts in isotopic niche area and overlap between invasive and native fishes (measured by sample-size corrected standard ellipse area). If resources become limiting, invasive Silver Carp may compete with multiple life stages of Gizzard Shad in Kentucky Lake and alter foodweb dynamics.

Intraspecific morphological variation in shads, Dorosoma anale and D. petenense (Actinopterygii: Clupeiformes: Clupeidae), in the Mexican Grijalva and Usumacinta river basins

Historical hydrological changes and the environmental characteristics of northern Middle America have promoted diversification and determined the distribution of fishes in the Grijalva and Usumacinta river basins of Mexico. In several taxa with wide distributions, cryptic diversity has been identified through molecular and morphological analyses. This study evaluated the intraspecific morphological variation of Dorosoma anale Meek, 1904 and Dorosoma petenense (Günther, 1867) along the Grijalva and Usumacinta river basins through geometric morphometric and linear biometric analyses. Little intraspecific differentiation was detected for either species. However, differences were identified between populations in the Grijalva basin and those from the upper Usumacinta River basins with respect to body height, head size, pelvic fin position, and anal fin size. The phenotypic expression of these attributes appears to be closely related to habitat type and geographic isolation. The morphological differences within D. petenense support the molecular hypothesis of two lineages existing in the Usumacinta River basin.

Influence of blueback herring, Alosa aestivalis, on zooplankton in a southeastern US reservoir

Grove L, Stell EG, Grove LJW, Wright RA, DeVries DR. 2022. Influence of blueback herring, Alosa aestivalis, on zooplankton in a southeastern US reservoir. Lake Reserv Manage. 38:256–267. Forage fishes like blueback herring (Alosa aestivalis) have been widely introduced, sometimes without careful consideration of potential ecological consequences. We compared biotic and abiotic factors before and after blueback herring introduction into Lewis Smith Lake, Alabama (United States), and tested for diet overlap among planktivorous species to quantify their potential ecological influences. Abiotic and biotic factors varied among regions of the lake, consistent with differences in agricultural practices and nutrient input within each region. Secchi depth increased and zooplankton density decreased, while chlorophyll a remained unchanged relative to before blueback herring introduction. Juvenile and adult blueback herring and threadfin shad (Dorosoma petenense) consumed the same zooplankton taxa; however, blueback herring consumed significantly larger individuals and significantly greater numbers of zooplankton than threadfin shad. Blueback herring also selectively consumed larger zooplankton than the average size in the reservoir population, while threadfin shad did not. Threadfin shad and blueback herring positively selected Bosmina and cyclopoid copepods. The taxonomic overlap and size selectivity in prey choice suggest that if blueback herring reduce larger zooplankton, threadfin shad and blueback herring diets are likely to increasingly overlap. Because of their differences in feeding strategies (i.e., related to zooplankton size differences) and habitat preferences, current evidence for potential competitive interactions between these planktivores appears limited; however, longer term concerns are that blueback herring could eventually reduce larger zooplankton to the extent where they would increasingly compete with threadfin shad as the most abundant forage fish in Lewis Smith Lake.

Molecular data elucidate cryptic diversity within the widespread Threadfin Shad (Dorosoma petenense: Clupeidae) across the Nearctic and Northern Neotropics

Molecular data elucidate cryptic diversity within the widespread Threadfin Shad (Dorosoma petenense: Clupeidae) across the Nearctic and Northern Neotropics

Change in Piscivore Growth Potential after the Introduction of a Nonnative Prey Fish: a Bioenergetics Analysis

AbstractThe introduction of additional forage fish species to enhance sport fisheries is a common management strategy in lakes and reservoirs. However, illegal introductions occur without consideration of all potential ecological consequences. Introduction of Blueback Herring Alosa aestivalis as a forage fish to enhance recreational fisheries has been controversial, with several illegal introductions documented in the southeastern United States. We quantified the caloric density of introduced Blueback Herring and native Threadfin Shad Dorosoma petenense in Lewis Smith Lake, Alabama, to determine their potential values as prey to piscivorous fish. Caloric density estimates were then incorporated into bioenergetics simulations for Largemouth Bass Micropterus salmoides, Alabama Bass Micropterus henshalli, and Striped Bass Morone saxatilis to estimate their growth potential given different diet compositions. Piscivore diet composition from before the introduction of Blueback Herring was also incorporated into bioenergetics simulations for comparison with post‐introduction scenarios. Caloric density of Blueback Herring was higher than that of Threadfin Shad across all seasons, and consequently, bioenergetics simulations predicted increased growth potential for Largemouth Bass, Alabama Bass, and Striped Bass with increased proportions of Blueback Herring in their diets. The simulated growth effect of shifting consumption from Threadfin Shad to Blueback Herring was smaller for Largemouth Bass versus Striped Bass because Striped Bass were far more piscivorous than Largemouth Bass, with Alabama Bass intermediate. Simulated pre‐Blueback Herring piscivore diets resulted in less growth relative to what was observed for all post‐introduction simulations. Although Blueback Herring had higher caloric density values than Threadfin Shad, overall ecological impacts of their introduction are not yet fully understood and could likely also include negative impacts on these piscivores. As such, our findings represent one aspect of the overall, potentially complex effect of introduced Blueback Herring as an additional forage fish for piscivores.

Examining Retention-at-Length of Pelagic Fishes Caught in the Fall Midwater Trawl Survey

The Fall Midwater Trawl Survey has provided data on aquatic organisms in the San Francisco Estuary for over five decades. In 2014–2015, a study was conducted to investigate and quantify the efficiency of this trawl for catching the endangered fish species Delta Smelt (Hypomesus transpacificus). In an analysis based on that study, we calculated retention probability—the probability that a Delta Smelt is retained in the cod end of the trawl—as a function of fish length and fit a selectivity curve reflecting the relationship between size and retention. Here we return to the same gear efficiency study and further utilize the data set by (1) fitting selectivity curves for three additional pelagic fish species: Threadfin Shad (Dorosoma petenense), American Shad (Alosa sapidissima), and Mississippi Silverside (Menidia beryllina), (2) refitting the selectivity curve for Delta Smelt to incorporate between-haul variability, and (3) calculating the lengths of 50% and 95% retention in order to characterize and compare the resulting selectivity curves. We also present retention data on age-0 Striped Bass (Morone saxatilis), all of which were retained in the cod end. We found that Threadfin Shad, American Shad, and Delta Smelt are 95% retained at 45, 49, and 61 mm fork length, respectively. Because data were limited for Mississippi Silverside, American Shad, and age-0 Striped Bass, we used body shape, in conjunction with retention data, to develop hypotheses about selectivity based on whether each species’ body shape resembles that of Threadfin Shad, which are more deep-bodied and laterally compressed, or Delta Smelt, which are more fusiform. We also found that retention-at-length was more variable for Delta Smelt than for Threadfin Shad, potentially because length is a good predictor of retention in deep-bodied, laterally compressed fish whereas maximum girth is a better predictor of retention in fusiform fish.

Determining the Exposure Pathway and Impacts of Microcystis on Threadfin Shad, Dorosoma petenense, in San Francisco Estuary.

Blooms of the cyanobacterium Microcystis spp. could affect fish health through the ingestion of colonies as well as exposure to dissolved microcystins in the water column. The goal of the present study was to evaluate the dietary exposure pathway through which Microcystis spp. blooms may affect liver function and nutritional status using a novel approach involving multiple analytical methods to assess the potential risk. Our study was conducted using threadfin shad, Dorosoma petenense, which is a pelagic fish commonly exposed to Microcystis spp. blooms in the upper San Francisco Estuary. The approach incorporated published and optimized methods that offer multiple lines of evidence including in situ hybridization, immunohistochemistry, histopathology, condition factor indices, and nutritional profiles. Measurements of threadfin shad health and tissue condition were conducted at sites where Microcystis was present or absent during the 2007 bloom season. The results showed that dietary exposure to fish from Microcystis blooms resulted in the accumulation of microcystin in the gut and liver tissues of threadfin shad collected from the sites with blooms. Although toxicity endpoints were likely confounded by antecedent conditions, our findings demonstrate dietary exposure of Microcystis toxins to fish using a novel approach with multiple lines of evidence. Environ Toxicol Chem 2020;39:787–798. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Community Patterns and Environmental Associations for Pelagic Fishes in a Highly Modified Estuary

AbstractUnderstanding how natural and human‐induced processes interact to influence ecosystem responses is essential for their effective management and conservation. Long‐term environmental degradation of the upper San Francisco Estuary, California, has resulted in numerous species declines. In this study, we used pelagic fish monitoring and hydrodynamic data during winter–spring 2002–2014 to evaluate how natural and human‐induced environmental changes in the upper San Francisco Estuary may have influenced the distribution, abundance, and community structure of the pelagic fishes. Delta outflow and turbidity tended to decline and salinity tended to increase since the early 2000s. Twelve of the 27 pelagic fish species sampled were introduced, most of which were freshwater‐dominant species in highly altered upstream areas. Overall mean relative abundance was similar between native and introduced fishes across all study areas. The upstream distribution of the eight most abundant pelagic fishes was generally associated with their salinity habitat components. Among these species, the Delta Smelt Hypomesus transpacificus and the introduced Threadfin Shad Dorosoma petenense had the highest rates of population decline over the period 2002–2014 and the largest relative increase in salinity predicted in their habitats due to hydrological alteration. Community structure was significantly related to abiotic factors (water temperature, salinity, and turbidity) and spatiotemporal variation (longitude and month), which accounted for 30–33% of the variation. Low to intermediate outflows due to droughts and water diversions since the early 2000s likely interacted synergistically with multiple factors, decreasing the abundance of several pelagic species. Management actions linking ecologic, hydrologic, and geomorphic processes with multiple stressors could help to reverse the long‐term decline of Delta Smelt and other threatened and endangered fishes in the San Francisco Estuary.

GONADAL HISTOPATHOLOGY OF FISH FROM LA PÓLVORA URBAN LAGOON IN THE GRIJALVA BASIN, MEXICO

Studies on environmental pollution in Mexican freshwater ecosystems by means of fish histopathology are extremely scarce. In that view, this research analyzed the gonad histopathology of four teleost fish species from a hyper-eutrophicated fragmented urban lagoon, in order to determine possible harmful effects of water pollutants on their reproductive fitness. Gonads were processed by histological conventional techniques. The gonadal alterations detected in both, the clupeid Dorosoma petenense and the cichlid Thorichthys meeki expose the need to clarify the connection of these alterations to the presence of specific pollutants.

Pelagic Nekton Abundance and Distribution in the Northern Sacramento–San Joaquin Delta, California

AbstractKnowledge of the habitats occupied by species is fundamental for the development of effective conservation and management actions. The collapse of pelagic fish species in the Sacramento–San Joaquin Delta, California, has triggered a need to better understand factors that drive their distribution and abundance. A study was conducted in summer–fall 2014 in an attempt to identify physical and biological habitat conditions that drive the abundance and distribution of pelagic species in the northern region of the system. The study was conducted in the three largest channels in the northern Sacramento–San Joaquin Delta by dimension, volume, and flow capacity. The pelagic community was dominated by three nonnative species, Siberian prawn Exopalaemon modestus, which comprised 56% of the total number of organisms, and two fish species, Threadfin Shad Dorosoma petenense and Mississippi Silversides Menidia audens, which together comprised 43% of the total number of organisms. Total fish and total shrimp abundance were sensitive to the most extreme values of turbidity and temperature encountered and positively associated with total zooplankton biomass. The results suggested that habitat conditions in terminal channels, historically a common feature on the landscape, support higher abundances of pelagic species and zooplankton than open‐ended channels. These results provide resource managers with useful information on the habitat associations of pelagic species and on how the future distribution and abundance of pelagic species will likely change in response to climate or other ecological factors.Received March 8, 2016; accepted September 22, 2016 Published online December 9, 2016

Description and Comparison of the Canals and Canal Branching Pattern of the Lateral Line Canal System ofDorosoma petenense(Günther) [Clupeomorpha: Clupeoidei

The lateral line canals, canal neuromasts, dermal canal carrying bones and scales, and canal branches of Dorosoma petenense are described and compared with those of clupeids Dorosoma cepedianum, Brevoortia patronus, Brevoortia tyrannus, Caspialosa pontica, Chirocentrus dorab, Clupea harengus, Clupeonella cultriventris, and Sardina pilchardus. The first trunk lateral line canal carrying scale is narrower than the second in Denticeps clupeoides, Dorosoma petenense, Dorosoma cepedianum, and Sardina pilchardus. Although the clupeoid lateral line canal system is complex, information from its branching pattern, with or without information from other systems of the body, could provide significant justification for a fully resolved phylogeny of clupeoids.

Explaining Patterns of Pelagic Fish Abundance in the Sacramento-San Joaquin Delta

Investigating the effects of environmental, biological, and anthropogenic covariates on fish populations can aid interpretation of abundance and distribution patterns, contribute to understanding ecosystem functioning, and assist with management. Studies have documented declines in survey catch per unit effort (CPUE) of several fishes in the Sacramento-San Joaquin Delta, a highly altered estuary on the US west coast. This paper extends previous research by applying statistical models to 45 years (1967–2012) of trawl survey data to quantify the effects of covariates measured at different temporal scales on the CPUE of four species (delta smelt, Hypomesus transpacificus; longfin smelt, Spirinchus thaleichthys; age-0 striped bass, Morone saxatilis; and threadfin shad, Dorosoma petenense). Model comparisons showed that along with year, the covariates month, region, and Secchi depth measured synoptically with sampling were all statistically important, particularly in explaining patterns in zero observations. Secchi depth and predicted CPUE were inversely related for all species indicating that water clarity mediates CPUE. Model comparisons when the year covariate was replaced with annualized biotic and abiotic covariates indicated total suspended solids (TSS) best explained CPUE trends for all species, which extends the importance of water clarity on CPUE to an annual timescale. Comparatively, there was no empirical support for any other annualized covariates, which included metrics of prey abundance, other water quality parameters, and water flow. Top-down and bottom-up forcing remain important issues for understanding delta ecosystem functioning; however, the results of this study raise new questions about the effects of changing survey catchability in explaining patterns in pelagic fish CPUE.

Importance of Resident and Seasonally Transient Prey to Largemouth Bass in the St. Johns River, Florida

AbstractWe examined seasonal dynamics of prey availability and diets of Largemouth Bass Micropterus salmoides in the St. Johns River, Florida. The four most common prey species were Threadfin Shad Dorosoma petenense, Bay Anchovy Anchoa mitchilli, Atlantic Croaker Micropogonias undulatus, and Atlantic Menhaden Brevoortia tyrannus. The number of prey found in Largemouth Bass varied significantly by month (year‐round) and predator size (“small,” &lt;356 mm TL, n = 267; “medium,” 356–432 mm TL, n = 205; “large,” &gt;432 mm TL, n = 114). Atlantic Menhaden were most energetically beneficial to predators when available. Of the four most common prey species collected in trawls, only menhaden trawl catch was positively correlated with its appearance in bass diets. Menhaden were eaten by bass of all sizes, but were found only from September through November. Largemouth Bass did not feed heavily on juvenile anadromous shads Alosa spp. during their autumn migration, but this likely reflected low abundance of these clupeid species. The seasonal diversity of prey available in the St. Johns River may contribute to its being one of the most productive Largemouth Bass fisheries in Florida.Received June 23, 2014; accepted October 22, 2014

Use of Mini‐Fyke Nets for Sampling Shallow‐Water Fish Communities in Florida Lakes

AbstractWe evaluated mini‐fyke nets for sampling shore‐based (SB; &lt;1 m deep) fish communities in Florida lakes. Specifically, we wanted to determine the most effective deployment method and sample size required for adequately characterizing fish communities in these habitats. Shallow SB (0.15–0.6 m) net sets, in which nets were not completely submersed, collected significantly more individuals and a larger proportion of poeciliids. However, deep SB (0.6–1.0 m) net sets, in which nets were completely submersed, collected a larger proportion of centrarchids, cyprinids, and cyprinidontids. Net placement also significantly affected the overall catch and composition of samples. Nets placed in locations away from the lake boundary tended to collect actively schooling fishes such as Threadfin Shad Dorosoma petenense and cyprinids. Nets placed next to the lake boundary tended to collect species associated with shallow, vegetated habitats, particularly poeciliids, at greater frequencies. In some cases, the collection of these fishes was unique to a particular deployment method. Our results suggest that in long‐term monitoring of Florida's shore‐based lentic fish communities, nets should be placed in SB waters with the lead extending to the lake boundary. Although long‐term sampling objectives may vary, we determined that a sampling target of 30 net sets was sufficient for characterizing the fish community in terms of percentage composition, species richness, and species diversity. Furthermore, we recommend the continued use of additional gears to fully characterize littoral fish communities.Received December 19, 2013; accepted March 1, 2014

The late summer crustacean zooplankton in western U.S.A reservoirs reflects ecoregion, temperature and latitude

Summary We tested whether the crustacean zooplankton species composition and size structure (which are important determinants of energy flow in plankton food webs) during late summer in reservoirs would be related to ecoregional designations, catchment land use, temperature and latitude. We also examined whether the predictions of decreasing cladoceran body size with decreasing latitude (as observed for natural lakes) would be valid for reservoirs. Zooplankton samples were collected in late summer 2010 from 102 western U.S. reservoirs distributed over three major ecoregions from 32.5 to 48.6°N latitude. Large‐bodied cladocerans (Daphnia pulex complex) and cyclopoid copepods (Diacyclops thomasi) were found in deeper, cooler reservoirs with forested catchments (Northwestern Forested Mountains). Small‐bodied cladocerans (Daphnia retrocurva, Diaphanosoma spp. and Chydorus sphaericus) and cyclopoid copepods (Tropocyclops prasinus) were more common in productive reservoirs in catchments influenced by agriculture (Great Plains). Small‐bodied cladocerans (Bosmina longirostris) dominated the otherwise modest crustacean zooplankton in reservoirs located in catchments dominated by evergreen shrub vegetation with limited forestation (Western Xeric). Calanoid copepods also displayed clear distribution by ecoregion. Increasing water temperature and decreasing latitude were associated with smaller mean Daphnia and cladoceran body lengths and lower absolute biomass of daphniids. Daphniids were rare or absent in warm waters (i.e. below 36o N latitude and/or from sites located &lt;500 m altitude). Species composition and mean body size of the cladoceran zooplankton were consistent with the feeding habits of the common planktivorous fish – salmon (Oncorhynchus spp.) and lake trout (Salvelinus spp.) in the Northwestern Forested Mountains, gizzard shad (Dorosoma cepedianum) in the Great Plains and threadfin shad (Dorosoma petenense) in the Western Xeric ecoregion. Our study indicates that the taxonomic composition and size structure of the cladoceran zooplankton in reservoirs are highly connected to ecoregional attributes such as catchment land use, temperature and latitude as has been observed for natural lakes.

Roof-Nesting Least Terns Travel to Forage in Brackish/Marine Waters

Sternula antillarum (Least Tern) are small, migratory seabirds that are listed as threatened or endangered in every state in which they occur. While their natural nesting habitat is open beach, Least Terns have adapted to nest on flat tar and gravel roofs, sometimes many kilometers inland. We used the “fish drop” technique to collect fish that birds dropped around a roof colony in Pinellas County, FL to assess use of fresh and saltwater fish species as prey. We collected 37 fish from 12 different species. The most common (n = 11) was Dorosoma petenense (Threadfin Shad), a species found primarily in marine/brackish waters, but often stocked in man-made freshwater ponds to supplement piscivorous fish prey. Eighteen of the remaining 26 fish, encompassing 7 of the remaining 11 species, are marine/brackish species, 5 individuals are freshwater species, and 3 are freshwater/brackish species. Roof-nesting Least Terns appeared to forage in stormwater ponds and a lake found near the colony, but they also traveled a minimum of 4.8 km to forage in marine/brackish waters. Roof nesters may face greater challenges than beach nesters, because they are potentially exposed to more pollutants in stormwater ponds and expend more energy and time to travel farther to forage at saltwater sites.