Kepone®: Toxicity and bioaccumulation in blue crabs

Two long-term studies were conducted to determine toxicity, uptake and depuration of Kepone in blue crabs (Callinectes sapidus). In the first, Kepone was administered to crabs in seawater (0.03 or 0.3 μg Kepone/I) or food (eastern oyster,Crassostrea virginica, containing 0.25 μg/g Kepone). Uptake of Kepone in 28 days was primarily through the contaminated oysters. When these crabs were held in Kepone-free seawater and fed Kepone-free oysters for 28 days, no loss of the insecticide was evident. There were adverse effects on molting and survival in crabs fed oysters that contained 0.25 μg/g Kepone. A second study was conducted to determine: (1) the depuration of Kepone over a 90-day period in blue crabs fed oysters from the James River, Virginia (containing 0.15 μg/g Kepone); and (2) the effects of Kepone on molting and survival of blue crabs fed James River oysters or laboratory-contaminated oysters that contained 0.15 or 1.9 μg/g Kepone. Crabs fed Kepone-contaminated oysters followed by a diet of Kepone-free oysters for 90 days had detectable concentrations of the insecticide in tissues. Also, blue crabs that ate oysters containing Kepone in concentrations similar to those found in oysters from the James River, died or molted less frequently than crabs fed Kepone-free oysters meats.     

Recruitment of the Crabs Eurypanopeus depressus, Rhithropanopeus harrisii, and Petrolisthes armatus to Oyster Reefs: the Influence of Freshwater Inflow

Oyster reefs provide structural habitat for resident crabs and fishes, most of which have planktonic larvae that are dependent upon transport/retention processes for successful settlement. High rates of freshwater inflow have the potential to disrupt these processes, creating spatial gaps between larval distribution and settlement habitat. To investigate whether inflow can impact subsequent recruitment to oyster reefs, densities of crab larvae and post-settlement juveniles and adults were compared in Estero Bay, Florida, over 22 months (2005–2006). Three species were selected for comparison: Petrolisthes armatus, Eurypanopeus depressus, and Rhithropanopeus harrisii. All are important members of oyster reef communities in Southwest Florida; all exhibit protracted spawning, with larvae present throughout the year; and each is distributed unevenly on reefs in different salinity regimes. Recruitment to oyster reefs was positively correlated with bay-wide larval supply at all five reefs examined. Species-specific larval connectivity to settlement sites was altered by inflow: where connectivity was enhanced by increased inflow, stock–recruitment curves were linear; where connectivity was reduced by high inflows, stock–recruitment curves were asymptotic at higher larval densities. Maximum recruit density varied by an order of magnitude among reefs. Although live oyster density was a good indicator of habitat quality in regard to crab density, it did not account for the high variability in recruit densities. Variation in recruit density at higher levels of larval supply may primarily be caused by inflow-induced variation in larval connectivity, creating an abiotic simulation of what has widely been regarded as density dependence in stock–recruitment curves.     

Low incidence and limited effect of the oyster pathogen dermo (<Emphasis Type="Italic">Perkinsus marinus</Emphasis>) on an artificial reef in Delaware's Inland Bays

Delaware's Inland Bays comprise a large estuarine system with a restricted access to the Atlantic Ocean (Indian River Inlet). As part of a local oyster stock enhancement and restoration effort, we conducted a survey for the protozoan pathogenPerkinsus marinus (Dermo) in oysters from a newly established reef. Using standardized methods for the polymerase chain reaction (PCR) amplification of the non-transcribed spacer (NTS) region, we were surprised to find no detectable titers of this pathogen in the 30 oysters sampled in the first year of the project. The detection threshold of the PCR coupled with chemiluminescent detection was 30 fgP. marinus NTS DNA. We were able to detect a trace presence of this pathogen in a few hard clams (Mercenaria mercenaria) from the same locale, indicating that aPerkinsus sp. was present in the Inland Bay system. Subsequent monitoring of the reef system using a fluid thioglycollate assay over 3 yr revealed no epizootic outbreaks of this pathogen within the planted oyster population. Two large mortality episodes that did appear in the oyster population were attributable to abiotic conditions and not pathogen exposure. This study emphasizes that all potential sources of mortality in the environment are important to consider when designing oyster seeding projects. In the Delaware Inland Bays,P. marinus does not appear to have a large enough oyster host population to become a significant disease threat at present. Because of the low parasite incidence levels in the Inland Bay system in 2000, the James Farm oyster reef restoration project presents an ideal model system to follow the population dynamics between an oyster-host population and a latent or reservoir pathogen population.     

Asiatic clam (Corbicula manilensis) and other foods used by waterfowl in the James River,Virginia

Corbicula manilensis was found in the gizzards of 24 ducks of 5 species taken from the James River, Virginia, between 1973 and 1976. Percent average volume in these species ranged from trace to 6%. This is the first known occurrence of this exotic clam in the food of duck in Chesapeake Bay. A total of 135 other food items was identified from the 116 gizzards of 9 species that were examined. Food that predominated includedCyperus spp.,Leersia oryzoides, Polygonum spp., andZea mays. The great diversity of food consumed in this fresh tidal section of the James River indicates the high value of these wetlands to waterfowl. *** DIRECT SUPPORT *** A01BY015 00008     

Aspects of the population dynamics of the polychaeteSabellaria vulgaris Verrill,in the Delaware Bay

Aspects of the population dynamics of the polychaeteSabellaria vulgaris Verrill 1874 were studied by observing the temporal occurrence of larvae in the plankton of Delaware Bay. Vertical plankton samples were collected monthly from July 1970 to October 1971. Four 25-hour plankton studies were conducted within this time period, and on one occasion samples were collected on a transect across the mouth of the bay.Sabellaria vulgaris larvae were present in the bay only from mid-April through October. July (1970) and August (1971) 25-hour plankton studies showed larvae present in the water column at virtually all times of the day and night. Horizontal dispersion of larvae in the plankton was clearly aggregated. However, correlation of larval presence, absence or abundance with the measured physical factors in the estuary was not apparent except on a seasonal scale. Six developmental stages were defined based upon observation of laboratory-reared larvae. Young larvae appeared in the plankton on numerous occasions, indicating that spawning occurred repeatedly during the April–October time period in Delaware Bay. Relative to other habitats within the geographic range ofS. vulgaris, Delaware Bay is a particularly well-suited environment for the construction of massive colonies by the species. Adults living in large aggregates would exhibit greater fitness because of the higher probability of eggs being fertilized. Indications are that a portion of the larvae produced in the Bay are retained in the estuary and undergo settlement there. Delaware Bay may be a population center for the species. A comparison of reproductive phenomena among sabellariid species is presented. It is apparent that the species,S. vulgaris, consists of several physiologically distinct populations, and that this is true of certain other sabellariid species as well.     

Dinosaur eggshells from the Santonian Milk River Formation of Alberta,Canada

The North American fossil record of dinosaur eggshells for the Cretaceous is primarily restricted to formations of the middle (Albian–Cenomanian) and uppermost (Campanian–Maastrichtian) stages, with a large gap in the record for intermediate stages. Here we describe a dinosaur eggshell assemblage from a formation that represents an intermediate and poorly fossiliferous stage of the Upper Cretaceous, the Santonian Milk River Formation of southern Alberta, Canada. The Milk River eggshell assemblage contains five eggshell taxa: Continuoolithus, Porituberoolithus, Prismatoolithus, Spheroolithus, and Triprismatoolithus. These ootaxa are most similar to those reported from younger Campanian–Maastrichtian formations of the northern Western Interior than they are to ootaxa reported from older middle Cretaceous formations (i.e., predominantly Macroelongatoolithus). Characteristics of the Milk River ootaxa indicate that they are ascribable to at least one ornithopod and four small theropod species. The taxonomic affinity of the eggshell assemblage is consistent with the dinosaur fauna known based on isolated teeth and fragmentary skeletal remains from the formation, although most ornithischians and large theropods are not represented by eggshell. Relative to the Milk River Formation eggshell, similar oospecies occurring in younger Cretaceous deposits tend to be somewhat thicker, which may reflect an increase in body size of various dinosaur lineages during the Late Cretaceous.     

Oysters and the Chesapeake Bay ecosystem: A case for exotic species introduction to improve environmental quality?

Restoration of the Chesapeake Bay ecosystem has been a priority for residents and governments of the bay watershed for the past decade. One obstacle in the efforts to “save the bay” has been continuing nutrient enrichment from agricultural and sewer runoff. The attainability of a mandated 40% nutrient reduction goal has yet to be seen. Furthermore, disappearance of certain organisms may have had an adverse effect on the resilience of the ecosystem. The Eastern oyster (Crassostrea virginica), once abundant in Chesapeake Bay, was a vital part of the food web, processing excess phytoplankton and depositing materials on the bottom. Over harvesting and disease have decimated the native oyster population. The introduction of an exotic species, the Japanese oyster (Crassostrea gigas), may be a way to reestablish a robust oyster community in the bay. The literature on the role of bivalve molluscs in estuarine ecosystems shows that they are an essential part of healthy estuaries around the world. A comparison ofC. virginica andC. gigas in terms of temperature and salinity tolerance and resistance to disease shows thatC. virginica is ideally adapted to conditions in Chesapeake Bay, but it is unable to stave off the endemic diseases, whereasC. gigas is adapted to conditions in the lower bay only but is much less susceptible to the same diseases. We conclude that the potential introduction ofC. gigas to Chesapeake Bay would be limited by the Japanese species’ physiological requirements but that the revitalization of a bivalve population is imperative to the restoration of ecosystem function.     

Neoichnology and implications for stratigraphy of reworked Upper Oligocene oysters,Antigua, West Indies

The Late Oligocene oyster Hyotissa antiguensis (Brown) is locally common in the Antigua Formation of Hughes Point, eastern Antigua, Lesser Antilles; it was not commonly bored at that time. Its valves and shells are robust, and reworked into the shallow water near-shore environment in Antigua; it could potentially be incorporated into younger rocks. Its neoichnology includes clues that would facilitate identification of these oysters as reworked fossils. The suite of modern borings found in these specimens includes common Caulostrepsis taeniola Clarke, Gastrochaenolites isp. cf. G. turbinatus Kelly and Bromley and Entobia isp., and rare Oichnus simplex Bromley and Rogerella? isp. The latter three taxa are limited to oyster shell substrates. Of the common ichnotaxa, Caulostrepsis and Gastrochaenolites are particularly prominent in limestone clasts and limestone cemented to oyster shells, which would be an indicator of reworking if found in a post-Oligocene lithified deposit. Caulostrepsis and Gastrochaenolites are relatively less common in oyster shells and valves, and in many specimens are seen to terminate against the shell. Entobia is the only common boring limited to the shell substrate. The fidelity of preservation of modern borings is also superior in limestone clasts. This suite of borings is comparable with those found in the Neogene of the Antillean region.     

The distribution of shallow water juvenile fishes in an urban estuary: The effects of manmade structures in the lower Hudson River

The objective of this study was to determine what effect, if any, large pile-supported platforms (piers) have on the habitat distribution and abundance of juvenile fishes. Trapping techniques were used in 1993 and 1994 under piers, in pile fields, and in open-water habitat types in shallow areas (<5 m) in the lower Hudson River estuary (40°44′N, 70°01′W). Nearly 1500 fishes, mostly juveniles, representing 24 species were collected in 1865 trap-days from May through October in the 2-yr study. The presence of relatively large numbers of young-of-the-year (YOY) fish during both years lends support to the idea that shallow areas in the lower Hudson River estuary currently function as nursery habitats for a variety of fishes. Two seasonal assemblages were apparent, but their composition varied somewhat between years.Microgadus tomcod andPseudopleuronectes americanus YOY dominated an early summer assemblage (May–July) while large numbers of YOYMorone saxatilis were collected as part of a late summer assemblage (August–September). The effects of habitat type on fish assemblage structure were significant during both years. Fish abundance and species richness were typically low under piers; YOY fishes were rare andAnguilla rostrata accounted for a large proportion of the total catch. In contrast, YOY fishes dominated collections at pile field and open-water stations, where abundance and species richness were high. These results indicate that habitat quality under the platforms of large piers (>20,000 m²) is probably poor for YOY fishes when compared with nearby pile field and open-water habitat types.     

The relationship between trends in a condition index of the American oyster,Crassostrea virginica,and environmental parameters in three Virginia estuaries

Oyster Condition Index (CI) was partitioned, using a moving average filter, into seasonal cycles and long-term trends in the James, York, and Rappahannock rivers for the period 1970–1983. Seasonal cyclic fluctuations in CI could be explained partially by changes in salinity and number of days within various temperature regimes. Long-term trends in the James River show a steady increase in CI over the study period, while a concurrent decline was noted in the Rappahannock River. Superimposed on these trends is a 4 to 5 yr cycle that is in synchrony with river discharge (salinity). In the York River, CI peaked in 1975–1976 at all stations. Measured environmental parameters do not sufficiently explain the trends. We speculate that the differences in the Rappahannock and James rivers may be due to a decline in bottom oxygen as a result of gravitational circulation differences.     

Genetic variation in the oyster,Crassostrea virginica (Gmelin), in relation to environmental variation

Four polymorphic loci in seven natural oyster (Crassostrea virginica Gmelin) populations of the Chesapeake Bay were analyzed by protein-gel electrophoresis for genetic variation. Samples of about 100 each were taken in 1977 along environmental gradients from stations in the James and Potomac rivers. The distribution of genotypes at four loci for each of the stations was nog significantly different from Hardy-Weinberg expectations. At two loci (Pgi andLap-2), a pool of all seven stations was also in equilibrium. Significant genetic differentiation between rivers was detected for two other loci (Pgm-1 andLap-1), and frequency of one genotype (Lap-1 ^95/95) was significantly correlated with mean temperature over the water monitoring period (1972–1977).     

The distribution of heavy metals in the hard clam,Mercenaria mercenaria,in the lower Chesapeake Bay region

Populations of the hard clam,Mercenaria mercenaria, were sampled at thirty sites in the lower Chesapeake Bay region in 1972 and 1973. Subsamples were taken for analysis for the trace metals cadmium, copper and zinc. Emphasis was placed on samples from the York and James rivers, two very productive and commercially utilized clam grounds. The levels of metals determined were comparable to those reported from other regions except Southampton Water in the United Kingdom. Differences in levels between the York and James rivers were statistically significant (P<0.001) which indicates that the James River probably suffers from contamination by these metals. One metal, copper, varied significantly with the age of the organism whereas the other two, cadmium and zinc, varied with salinity. InMercenaria the salinity of the sampling site must be considered before cadmium and zinc data can be interpreted. A standard action-level to denote pollution from copper would be adequate in this species.     

The geomorphic development of wreck shoal,a subtidal oyster reef of the James River,Virginia

Wreck Shoal is a subtidal oyster reef located in the James River estuary, Virginia. This estuary has moved upstream and landward in response to rising sea level. The recent geomorphic history of Wreck Shoal is analyzed based on bathymetric records from the 1850’s to the 1980’s. The data indicate that the shallow oyster reef areas have lost elevation in the last 130 yr. This is attributed to intense harvesting activity during the last century. The late Holocene evolution of Wreck Shoal is developed based on the results of sub-bottom profiles and coring data. These suggest that the Wreck Shoal oyster reef has developed on the ridge and swale topography of a point-bar formed during the late Pleistocene epoch. Contemporary biodeposition processes on Wreck Shoal are evaluated. The results indicate that sediments of biogenic origin (fecal and shell material) potentially accumulate at rates in excess of 50 cm 100 years^?1. A model for subtidal oyster reef development is proposed that accounts for sea level rise, biodeposition, and the harvesting activity of man. The model is verified with field observations of reef elevation and radiocarbon dates of oyster shell material. The implications of these results are that oyster reefs should be considered a renewable natural resource, and therefore managed accordingly in concert with the oysters.     

Determination of Trophic Transfer at a Created Intertidal Oyster (<Emphasis Type="Italic">Crassostrea ariakensis</Emphasis>) Reef in the Yangtze River Estuary Using Stable Isotope Analyses

Oysters can create reefs that provide habitat for associated species resulting in elevated resident abundances, lower mortality rates, and increased growth and survivorship compared to other estuarine habitats. However, there is a need to quantify trophic relationships and transfer at created oyster reefs to provide a better understanding of their potential in creating suitable nekton habitat. Stable isotope analyses (δ¹³C and δ¹⁵N) were conducted to examine the organic matter sources and potential energy flow pathways at a created intertidal oyster (Crassostrea ariakensis; hereinafter, oyster) reef and adjacent salt marsh in the Yangtze River estuary, China. The δ¹³C values of most reef-associated species (22 of 37) were intermediate between those of suspended particle organic matter (POM) and benthic microalgae (BMI), indicating that both POM and BMI are the major organic matter sources at the created oyster reef. The sessile and motile macrofauna colonizing the reef make up the main prey of transient nekton (e.g., spotted sea bass, Asian paddle crab, and green mud crab), thus suggesting that the associated community was most important in supporting higher trophic levels as opposed to the direct dietary subsidy of oysters. The created oyster reef consistently supported higher trophic levels than the adjacent salt marsh habitat due to the dominance of secondary consumers. These results indicate that through the provision of habitat for associated species, created oyster reefs provide suitable habitat and support a higher average trophic level than adjacent salt marsh in the Yangtze River estuary.     

Habitat partitioning between the xanthid crabsPanopeus herbstii andEurypanopeus depressus on intertidal oyster reefs (Crassostrea virginica) in southeastern North Carolina

The abundances of the xanthid crabsPanopeus herbstii andEurypanopeus depressus were examined relative to surface oyster shell cover, surface oyster cluster volume, subsurface shell content, substrate sand and silt composition, and oyster reef elevation. During August 1986 through July 1987, xanthid crabs were collected monthly from twelve 0.25 m²×15 cm deep quadrats, during low tide, from intertidal oyster reefs in Mill Creek, Pender County, North Carolina, USA, with respective quadrat details recorded. The abundance ofP. herbstii, and to a lesser degreeE. depressus, was positively correlated with surface shell cover. The abundance ofE. depressus, and to a lesser degreeP. herbstii, was positively correlated with surface cluster volume. The majority ofP. herbstii inhabited the subsurface stratum of the oyster reef, whereas the majority ofE. depressus inhabited the cluster stratum. Seasonality (i.e., temperature) appeared to influence the strata habitation of both species, with a higher incidence of cluster habitation during warmer months and a lower incidence during colder months. Crab abundance was not related to other factors examined, such as subsurface shell, substrate sand and silt composition, or elevation within the oyster reef. The analyses show thatP. herbstii andE. depressus have partitioned the intertidal oyster reef habitat, withE. depressus exploiting surface shell clusters andP. herbstii the subsurface stratum.     

Tidal Habitats Support Large Numbers of Invasive Blue Catfish in a Chesapeake Bay Subestuary

The introduction of a non-native freshwater fish, blue catfish Ictalurus furcatus, in tributaries of Chesapeake Bay resulted in the establishment of fisheries and in the expansion of the population into brackish habitats. Blue catfish are an invasive species in the Chesapeake Bay region, and efforts are underway to limit their impacts on native communities. Key characteristics of the population (population size, survival rates) are unknown, but such knowledge is useful in understanding the impact of blue catfish in estuarine systems. We estimated population size and survival rates of blue catfish in tidal habitats of the James River subestuary. We tagged 34,252 blue catfish during July–August 2012 and 2013; information from live recaptures (n = 1177) and dead recoveries (n = 279) were used to estimate annual survival rates and population size using Barker’s Model in a Robust Design and allowing for heterogeneity in detection probabilities. The blue catfish population in the 12-km study area was estimated to be 1.6 million fish in 2013 (95% confidence interval [CI] adjusted for overdispersion: 926,307–2,914,208 fish). Annual apparent survival rate estimates were low: 0.16 (95% CI 0.10–0.24) in 2012–2013 and 0.44 (95% CI 0.31–0.58) in 2013–2014 and represent losses from the population through mortality, permanent emigration, or both. The tagged fish included individuals that were large enough to exhibit piscivory and represented size classes that are likely to colonize estuarine habitats. The large population size that we estimated was unexpected for a freshwater fish in tidal habitats and highlights the need to effectively manage such species.     

Egg extrusion as a kepone-clearance route in the blue crab,Callinectes sapidus

The concentration of Kepone in extruded egg masses and the backfin muscles of the blue crab,Callinectes sapidus, collected from seven stations in the lower James River and lower Chesapeake Bay was determined. Crabs from the lower James River were generally more contaminated than those from the lower Chesapeake Bay. Extruded eggs contain approximately three times more Kepone than backfin muscle. Egg extrusion is concluded to be a major route of Kepone clearance from female blue crabs.     

Temporal and spatial variations of trace metal concentrations in oysters from the Patuxent River, Maryland

Concentrations of copper (Cu), silver (Ag), and cadmium (Cd) in eastern oysters (Crassostrea virginica) from the upper Patuxent River estuary analyzed since 1986 (Cd since 1991) were high relative to concentrations in other sites in the United States analyzed by the National Oceanic and Atmospheric Administration National Status and Trends program. Patuxent River oysters had above average concentrations of Ag and Cu, and unusually high concentrations of Cd. Metal concentrations were highest in summer, a period in which oyster meat condition index was relatively low. Copper values were highest in 1986–1987, likely elevated by erosion from Cu-Ni alloy condensers at a local power plant. Silver and Cd values exhibited more year-to-year variation. A number of factors were examined as candidates to explain the interannual differences, including river flow, salinity, and oyster condition, but none was able to explain the high and low years. Samples collected in spring and late summer of 1996 at a number of oyster bars located along the length of the Patuxent River showed that concentrations of all three metals increased with distance up-river. For Cd, the upstream increase was linear with distance, while for Ag and Cu, there was a secondary maximum near river km 16. A close correlation was observed between Ag and Cu for individuals at each site, with a poorer correlation between Cd and either Ag or Cu.     

Nekton use of subtidal oyster shell habitat in a Southeastern U.S. estuary

Subtidal accumulations of oyster shell have been largely overlooked as essential habitat for estuarine nekton. In southeastern U.S. estuaries, where oyster reef development is mostly confined to the intertidal zone, eastern oyster (Crassostrea virginica) shell covered bottoms are often the only significant source of hard subtidal structure. We characterized and quantified nekton use of submerged shell rubble bottoms, and compared it to use of intertidal reefs and other subtidal bottoms in the North Inlet estuary, South Carolina. Replicate trays (0.8 m²) filled with shell rubble were deployed in shallow salt marsh creeks, and were retrieved after soak times of 1 to 25 days from May 1998 to March 2000. Thirty six species of fishes, representing 21 families, were identified from the 455 tray collections. Water temperature, salinity, soak time and the presence of a shell substrate all affected the catch of fishes in the trays. Catches during the warmer months were two to five times greater than those during the winter. Fishes were present in 98% of the trays with an overall average of 5.7 fish m^?2. The assemblage was numerically dominated by small resident species including naked goby (Gobiosoma bose), oyster toadfish (Opsanus tau), and crested blenny (Hypleurochilus geminatus). Transient species accounted for 23% of all individuals and 62% of the total biomass due to the presence of relatively large sheepshead (Archosargus probatocephalus) and black sea bass (Centropristis striata). Both the transient and resident species displayed distinct periods of recruitment and rapid growth from April to October. Lower abundances of juvenile gobies and blennies during 1998 were attributed to long periods of depressed salinity caused by high rainfall associated with El Niño conditions in spring. Crabs and shrimps, which were often more abundant than the fishes, accounted for comparable biomass in the tray collections. In comparisons of subtidal tray and trawl catches, trays yielded 10 to 1,000 fold higher densities of some demersal fish groups. Comparisons of intertidal and subtidal gear catches indicated that many species remain in the subtidal shell bottom at all stages of the tide. This study suggests that subtidal shell bottom may be essential fish habitat for juvenile seabass, groupers, and snappers and that it may be the primary habitat for a diverse assemblage of ecologically important resident fishes and crustaceans. Given the high levels of nekton use and the areal extent of oyster shell bottoms in eastern U.S. and Gulf estuaries, increased attention to protection and restoration of these areas appears justified.     

The Afro–Asian labeonine genus Garra Hamilton, 1822 (Teleostei,Cyprinidae) in the Pliocene of Central Armenia: Palaeoecological and palaeobiogeographical implications

Fossil skeletal remains of the Afro–Asian labeonine genus Garra are described on the basis of more than 300 specimens from the Pliocene diatomites of Jradzor, Central Armenia. Extant species of the genus Garra exhibit a wide distribution ranging from China, South Asia, and Borneo, through Middle East, the Arabian Peninsula, and Africa, where these fishes inhabit a variety of freshwater biotopes. The Pliocene fossils from the Jradzor site provide the first evidence of Garra in the fossil record. The inadequate preservation of the available material did not allow a detailed taxonomic attribution at the species level. Remains of Garra sp. were found associated to a moderately diverse assemblage, which includes also remains of additional freshwater fishes (Capoeta sp., Leuciscus cf. souffia, Leuciscus sp.), amphibians (Pelophylax cf. ridibundus), and large mammals (Rhinocerotidae indet.), as well as of monocotyledon plants. According to the diatom flora, the diatomites of Jradzor can be assigned to the Pliocene and were deposited in a freshwater lacustrine setting that was characterized by high productivity, eutrophic conditions, and standing macrophyte vegetation along the littoral zone. The presence of abundant resorptive pharyngeal teeth suggests that the Pliocene palaeolake of Jradzor was characterized by resident populations of Garra. Extant species of this genus are currently absent in the freshwaters of Armenia. The record of the genus Garra from Jradzor suggests that the Araks–Kura River drainage was connected, at least in part, with the Euphrates and Tigris River drainage during the Pliocene. The extinction of Garra (and other thermophilous taxa) from Araks and Kura River drainage was probably due to Plio-Pleistocene tectonic uplift of the Armenian Highland and consequent progressive climate cooling.