Reductions in cold-water habitat owing to anthropogenic stressors are focusing attention on indicator fish species. We investigated an apparent range expansion in Connecticut of a native cold-water fish, Slimy Sculpin (Cottus cognatus). Unexpectedly, genetic and morphological analyses identified the new population as a non-native cottid from the Ozark region, the Knobfin Sculpin (C. immaculatus). This is the first record of C. immaculatus outside of its native range. The new occurrences were not recognized for over a decade despite comprehensive watershed inventories by state natural resource managers. The mechanism by which the non-native Knobfin Sculpin first arrived in Connecticut is currently unknown. Our findings suggest that unintentional species introductions may occur more frequently than is currently recognized and highlight the need for more comprehensive assessments of non-native species distributions.

Invasive species threaten ecosystems with destruction of native habitat, introduction of novel diseases, and enhanced competition with native wildlife subsequent to reduced predator control, leading, in many cases, towards efforts to actively remove individuals. While these effects are frequently studied, minimal research has investigated the individual or population health of the invasive species themselves. In this study, we describe multiple health outcomes of Silver Carp (Hypophthalmichthys molitrix), an invasive species in the Illinois River, as a component of a long-term monitoring and removal program using electrofishing, gillnets, and trammel nets. Between April–October 2018, Silver Carp were collected from two reaches of the Illinois River, examined, blood was collected for hematologic measurements, and cranial kidneys collected for histologic examination of melanomacrophage centers. Collection location impacted body condition, as Silver Carp closer to the leading edge of invasion were heavier than those from more established populations. Silver Carp caught by nets had lower packed cell volumes than those caught by electrofishing. The Health Assessment Index (HAI) showed that 52% of livers and 53% of kidneys were grossly abnormal. The HAI comes with a caveat that validation protocols are required to implement this technique effectively. Hematology and histology are more likely to be useful in species for which reference ranges exist. Overall, invasive species contain a wealth of information on health outcomes that could be used to monitor ecosystem health, but techniques used for monitoring must be adapted to the species, management needs, and removal methods.

Habitat loss and degradation affect populations in isolation while also modifying the intensity of interspecific interactions, which may be especially relevant for species of conservation concern coexisting with more common species. We explored habitat preferences and potential interspecific resource competition in the endangered Spotted Turtle (Clemmys guttata). For habitat data, water quality measurements were recorded once per trapping session, while canopy cover and vegetation data were recorded once per field season. We also investigated niche overlap in habitat and food resources between C. guttata and other, more common, turtle species. Our data indicated that the abundance of C. guttata was negatively correlated with dissolved O₂ and pH levels and positively correlated with body of water depth and canopy cover. The investigation of niche overlap revealed that Mud Turtles (Kinosternon subrubrum) and Painted Turtles (Chrysemys picta), but not Snapping Turtles (Chelydra serpentina), were negatively correlated with the abundance of C. guttata despite differences in characteristics of bodies of water used by each species. We used structural equation modeling to better understand if the relationships between C. guttata and other turtles were due to direct interactions or simply reflected environmental influences. We then used stable isotope analyses to compare similarities in δ¹³C and δ¹⁵N isotopes as proxies for diet overlap between C. guttata and other turtles and ultimately found that all species had similar, broad diets. The inverse relationship between abundance of C. guttata and other species, paired with the overlap in dietary niche space, suggests there is potential for interspecific interactions to negatively impact the abundance of C. guttata within turtle communities on the Atlantic Coastal Plain. The results of this study highlight that management efforts may need to consider that species of conservation concern coexist with more common species, especially as habitat loss decreases the breadth of habitat available.

Hemidactylus turcicus and Tarentola annularis are occasionally sympatric and are ecologically similar in vertical wall microhabitat. For this reason, I studied their sexual, fat-body, and liver cycles for three years. All morphological variables are male-biased in T. annularis, unlike male H. turcicus, which showed significant differences in head sizes only. Females exhibited a spring to summer vitellogenic period with ovulation occurring during mid-spring to mid-summer in T. annularis and from late spring to late summer in H. turcicus. The mean clutch size of oviductal eggs (1.86) and relative clutch mass (0.188) was higher in H. turcicus than in T. annularis (1.67 and 0.132). Relative clutch mass was negatively correlated with snout–vent length in T. annularis but was not in H. turcicus. Sperm were present in the epididymis for eight months in H. turcicus while year-round in T. annularis. Post-breeding, masses of liver and fat body increased in both sexes of both species. There were significant differences in fat body and liver masses between the sexes of both species. Based on the liver-mass cycle, the energy expenditure on reproduction in male and female T. annularis was high compared with the corresponding sexes of H. turcicus. Testicular recrudescence began in late fall or early winter corresponding to lower temperatures, photoperiod, and precipitation. Testicular regression occurred at the highest temperatures in late summer and early fall.

The stable flow and temperature regimes of spring-fed streams are expected to provide unique foraging habitats and thermal refuges for fishes, but little is known about the seasonal utilization of spring-fed streams by fishes. Here, we investigated the seasonal changes in population density and stomach contents of juvenile Oncorhynchus masou masou in adjacent clastic lowland spring-fed and runoff tributaries in northern Japan. The results suggested two ecosystem functions of spring-fed streams. First, the stable flow regime of spring-fed streams can create depositional habitats and harbor abundant detritivores, and these macroinvertebrates, in turn, provide a significant food resource for juvenile fishes. Second, the stable temperature regime of spring-fed streams provides thermal refuges during hot and cold weather. Thus, the cooler spring-fed tributary abundant in aquatic prey forms a peak of juveniles' population density in August (1.3 individuals/m²). In November, the juvenile population increased four-fold (5.2 individuals/m²), perhaps affected by the warm environment of the spring-fed tributary. The abundance of eggs spawned by both wild and hatchery-reared O. keta may have also contributed to this increase in population through the provision of a nutritious food resource. We concluded that two ecosystem functions were identified in spring-fed streams in the summer, but additional investigation is required to examine the ecosystem functions in winter. Nevertheless, the results highlight that the heterogeneous environment formed by spring and runoff waters may strongly influence the spatiotemporal predator–prey interactions in river networks.

Two new species of snailfishes are described from the Aleutian Islands. Both are similar to Careproctus candidus, described originally from four specimens, here redescribed on the basis of 67 specimens in addition to the types. All three species are allocated to the Careproctus subgenus Temnocora. Careproctus candidus is distinguished from all other species of Careproctus by the combination of an anterior dorsal-fin lobe formed by a distinct notch, pupil a horizontal slit, and variegated reddish coloration. It is redescribed to note the presence of prickles, a variable pectoral-girdle morphology, and variable exsertions of the fin rays of the dorsal-fin lobe. Careproctus klisi, new species, is distinguished by having an anterior dorsal fin uniquely of five to seven short anterior dorsal-fin rays nearly equal in length preceding distinctly longer succeeding rays, pupil a horizontal slit, a variegated reddish coloration, and a relatively deep body. Careproctus bromius, new species, is distinguished by having low vertebral and median-fin ray counts, pupil a horizontal slit, a variegated light brown and pale coloration, and in lacking an anterior dorsal-fin lobe. Careproctus candidus ranges across the Aleutian Islands from Attu Island to the northern Gulf of Alaska at depths from 88 to 432 m. Careproctus klisi, new species, is found in the central and western Aleutian Islands from off Buldir Island in the west to Amlia Island in the east at depths from 134 to 180 m. Careproctus bromius, new species, is found in the central and eastern Aleutian Islands from Amchitka Pass to off Akutan Island at depths from 80 to 232 m.

We used data from a five-year study at two focal breeding wetlands of a single Crawfish Frog (Rana areolata) population to demonstrate the relative importance and potential of tadpole survival as a target for population management. We concurrently estimated 11 vital rates in the field and used a females-only matrix projection model to estimate elasticities of demographic rates. We then simulated stochastic population dynamics at each wetland with and without immigration to estimate the intrinsic capacity for each focal breeding wetland to sustain a Crawfish Frog breeding population and the likelihood of breeding population persistence at each wetland. Elasticity of tadpole survival was second only to juvenile survival elasticity and 1.34–2.04 times greater than adult survival elasticity. Projections indicated that the Crawfish Frog population was not at risk of extinction but only one breeding site was capable of self-sustaining a breeding population. Because of low tadpole survival, the other breeding site was completely dependent on immigration to persist and was functioning as a population sink. Despite higher variability compared to terrestrial vital rates, larval survival did have a strong effect on population growth. Tadpole survival at the more productive breeding site was density dependent and likely related to wetland vegetation and predator and competitor abundance. Two additional findings were that annual survival of frogs following their first known breeding event was 48% lower compared to survival of frogs that had bred in two or more prior years, and adult temporary emigration from the breeding population was moderately high. Our study demonstrates the benefits of using population models that integrate density-dependent processes, temporary emigration from the breeding population, and state-specific adult survival, to identify larval habitats that function as population sinks and limit current population size and persistence probability. We contend that tadpole survival is an important and feasible habitat management target within broader conservation strategies for Crawfish Frogs and other amphibian species.

The genus Eulophias, which is an enigmatic group of the suborder Zoarcoidei, previously comprised two rare species: Eulophias tanneri Smith, 1902 (type species and a senior synonym of Eulophias owashii Okada and Suzuki, 1954) and Eulophias koreanus Kwun and Kim, 2012. Here we describe a new species, Eulophias spinosior, based on 71 specimens (94.9–182.3 mm in standard length, SL) collected from the upper slope of the northwestern Pacific off southern Japan at depths of 257–555 m. It readily differs from its two congeners in having 133–143 dorsal-fin spines, 109–116 anal-fin soft rays, 5–6 pectoral-fin rays, and 146–156 total vertebrae, and in lacking a dark band posterior to the eye and a series of dark blotches midlaterally on the trunk and tail. Regarding bathymetric distribution, the new species occurs much deeper than E. koreanus and E. tanneri. Eulophias spinosior, new species, is sexually dimorphic, with males having large, stout, modified canines at the tips of the premaxillary and dentary (vs. only slightly enlarged in females). Dentition of males also differs from that of females in that most teeth are uniserially arranged in each jaw (vs. distinct two rows anteriorly).

From dissuading predators to gaining an edge on intraspecific rivals, animals have evolved weapons to meet various needs. Those with the most extreme weapons often use them to battle conspecifics, but some weapons defend against predation and others signal prowess to prospective mates and rivals. Many fishes have evolved armaments, but humans rarely observe these structures in action due to the inaccessibility of many weapon-bearing fish species. For example, how sculpins use the diverse horn-like spines that project from their head remains a mystery. We deduced the function of the weaponized preopercle in the 16 species of sculpins in the subfamily Oligocottinae by determining whether they exhibit three well-documented hallmarks of offensive weapons in terrestrial animals: ontogenetic change, sexual dimorphism, and fluctuating asymmetry. Geometric morphometrics of micro-computed tomography (lCT) scans show no sexual dimorphism in preopercular spine shape but reveal phylogenetically widespread ontogenetic shape change. Fluctuating asymmetry is low to moderate across species. Taken together, these results suggest that despite their varied reproductive habits, frequent territoriality, and possession of weapons that resemble bovid horns, oligocottine sculpins evolved their spines primarily to defend against predators.

Movement can act as an effective strategy used by amphibians to avoid detrimental environmental conditions, particularly drought. However, due to the unpredictable nature of droughts, evaluating the patterns and consequences of movement has rarely been investigated. In 2007–2008, the southeastern United States experienced a supraseasonal drought that resulted in 110 yr low flow levels among the first-order streams. In this study, 61 months of mark–recapture data collected from one first-order stream were used to examine the effects of drought on the movement frequency distribution, survival, and growth rates of adult Desmognathus fuscus (Northern Dusky Salamander). We hypothesized that salamanders would demonstrate a higher propensity to move during supraseasonal drought conditions and that moving salamanders would experience higher survival and growth rates. We found that salamanders were more likely to move immediately after the drought compared to the pre-drought and drought conditions. Although movement frequency was low during the drought, survival was higher for individuals who moved during drought conditions in comparison to individuals who remained in their original capture location. Although our model did not detect a trend, salamanders experienced slightly higher growth in the post-drought conditions compared to drought and pre-drought conditions. In addition, during the post-drought, salamanders that moved had slightly higher growth rates compared to salamanders who remained in their original capture location. Our results suggest that adult salamanders were potentially displaying an adaptive movement strategy to resist drought conditions by moving away from affected (i.e., dry) areas within the study stream. In addition, movement was likely utilized to access replenished resources in other areas after the severe effects of the drought ended. Therefore, both in-stream and riparian barriers that impede movement may inhibit resilience of stream amphibians during severe droughts.

Vitellogenesis is the process in which female oviparous vertebrates synthesize the protein vitellogenin to develop egg yolk. In some species, vitellogenin has been used to investigate reproductive status, as a biomarker of clutch size and nesting frequency, and as a biomarker of exposure to endocrine-disruptive chemicals. The Diamond-backed Terrapin (Malaclemys terrapin) is an obligate coastal species that in the northern extent of its range nests in the spring and summer months. Diamond-backed Terrapins serve as a key indicator species of coastal ecosystem health; thus, furthering our understanding of the endocrine control of reproduction may inform biologists of the health and status of coastal ecosystems. The objective of this study was to quantify baseline values of vitellogenin and testosterone in Diamond-backed Terrapins during the nesting season, in the northern part of their range. Blood samples were taken from adult female terrapins from two populations in coastal New Jersey from June–August. Enzyme-linked immunosorbent assays (ELISAs) were used to quantify vitellogenin (VTG) and testosterone (T) across the nesting season. VTG concentrations showed peak values in the earliest part of the nesting season, significantly declining through the summer before reaching basal values in August, with T showing a similar trend. This suggests that terrapins in New Jersey follow a similar reproductive cycle to other turtle species from temperate latitudes. Additionally, we found that larger females exhibited higher concentration of T and VTG than smaller females. This suggests that VTG and T are useful biomarkers of reproductive output in these animals. Lastly, we also noted that larger females tended to nest earlier in the nesting season than smaller females. We hypothesize that larger females may compete for resources more effectively and efficiently than smaller females, which may confer larger individuals a fitness advantage.

Acidification can have broad effects on forest ecosystems, ranging from consequences for individual organisms to alterations in trophic dynamics. While the effects of acidification on certain aspects of forest ecosystems have been well studied, less is known about the influence of soil acidification on the forest floor food web that includes amphibians and invertebrates. We investigated the effects of acidification on the American Toad (Anaxyrus americanus) and its interaction with the forest floor invertebrate community. We evaluated survival, growth, and diet of newly metamorphosed toads placed in terrestrial enclosures in forest plots with either experimentally elevated soil pH or untreated, acidified soils. We also conducted invertebrate pitfall sampling in these two soil pH types to evaluate the trophic interactions between toads and invertebrates. Toad mass after 90 days tended to be larger in plots with elevated soil pH, although survival and diet did not differ between soil pH types. We found no effect of soil pH on invertebrate abundances nor overall invertebrate diversity. We also found no evidence that toads exhibited top-down control of the invertebrate community. Collectively, our results indicate that acidified soils did not affect forest floor trophic dynamics. The presence of temporary enclosures we constructed, however, significantly reduced invertebrate abundances and overall diversity. Thus, the strong effect these structures can have on invertebrate communities should be considered when used in future studies.

Researchers frequently encounter turtle nests after the nest has been raided, finding only eggshell fragments that are difficult to identify. Valuable information on the breeding biology and needs of different species might still be collected from these nests if remains could be confidently assigned to a particular species. However, this can be difficult if there are multiple turtle species nesting within an area at a given time, and gross-scale characteristics such as egg size and shape are no longer available due to damage. This study examined eggshell microstructure, by scanning electron microscopy (SEM), among multiple species of freshwater turtle eggshell fragments, with the aim of potentially developing a diagnostic tool for species identification. Eggshell fragments were collected from known sources of four species of turtle native to eastern Australia: Eastern Long-necked Turtle (Chelodina longicollis), Murray River Turtle (Emydura macquarii), Bell's Turtle (Myuchelys bellii), and Bellinger River Turtle (M. georgesi). Fragments were scanned and analyzed for microstructural and ultrastructural features, and measured for differences in feature size across species. Central plaque diameter emerged as a potential diagnostic feature for separating species, with longneck turtle eggshells having no visible plaques, Murray River Turtle eggshells having relatively small mean plaque size (19.8 µm ± 10.28 SD), while Bell's Turtle (43.5 µm ± 14.16 SD) and Bellinger River Turtle eggshells (41.9 µm ± 15.41 SD) had relatively large plaques with little overlap between genera. Other measured features (shell unit size, basal knob size, and shell unit density) significantly differed in means among species but overlapped in range, or showed a lack of statistical difference, likely preventing the technique being definitive with a single measure. Some of this variance may be due to inherent confounding factors, such as the replicability of fragment preparation, condition of eggshells, and stage of embryonic development at the time of collection. These results suggest that use of measurements of microstructural features has promise as a means for distinguishing the provenance of eggshell fragments, and further investigation is warranted to develop site-specific protocols for use as a diagnostic tool for turtle ootaxonomy.