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1.
Riverine populations of shortnose sturgeon (Acipenser brevirostrum) once occurred in rivers and estuaries along the east coast of North America from the St. John River, New Brunswick, to the St. Johns River, Florida. Within this range, 19 population segments were identified by the U.S. Federal Shortnose Sturgeon Recovery Team; empirical data supporting this structure is limited. We obtained samples from 11 (12 including a small sample from the Cape Fear River, North Carolina) of these population segments and used PCR and direct sequence analysis of 440 base pairs of the mitochondrial DNA (mtDNA) control region to define the coast-wide genetic population structure of shortnose sturgeon. Collections from most population segments exhibited significant differences in haplotype frequencies with their nearest neighbors, including from the Ogeechee and Savannah Rivers, Georgia (despite the known movement of hatchery-reared offspring from the Savannah into the Ogeechee River). Collections from the Chesapeake Bay and Delaware River exhibited similar haplotype frequencies, suggesting that specimens collected in the Chesapeake Bay had dispersed from the Delaware River. Collections from the Kennebec River and Androscoggin River within a hypothesized single population segment did not exhibit significant differentiation of mtDNA haplotype frequencies. Haplotype frequencies were almost identical between collections from above and below the Holyoke Dam on the Connecticut River, indicating that these aggregations should be managed as a single unit. Our results support the population segment status afforded to shortnose sturgeon in at least the following 9 systems; St. John River, Kennebec-Androscoggin Rivers, upper-lower Connecticut River, Hudson River, Delaware River-Chesapeake Bay, Pee Dee River, Cooper River, Savannah River, and Ogeechee-Altamaha Rivers.  相似文献   

2.
During a reward program for Atlantic sturgeon (Acipenser oxyrinchus), 40 federally endangered shortnose sturgeon (Acipenser brevirostrum) were captured and reported by commercial fishers between January 1996 and January 2000 from the Chesapeake Bay. Since this is more than double the number of published records of shortnose sturgeon in the Chesapeake Bay between 1876 and 1995, little information has been available on distributions and movement. We used fishery dependent data collected during the reward program to determine the distribution of shortnose sturgeon in the Chesapeake Bay. Sonically-tagged shortnose sturgeon in the Chesapeake Bay and Delaware River were tracked to determine if individuals swim through the Chesapeake and Delaware Canal. Shortnose sturgeon were primarily distributed within the upper Chesapeake Bay. The movements of one individual, tagged within the Chesapeake Bay and later relocated in the canal and Delaware River, indicated that individuals traverse the Chesapeake and Delaware Canal.  相似文献   

3.
Large, recreationally or commercially important populations of Atlantic sturgeon (Acipenser oxyrinchus), American shad (Alosa sapidissima), and striped bass (Morone saxatilis) occur in the Hudson River. Members of the Hudson River populations of these fishes also occur over a broad range along the Atlantic coast where they mix with conspecifics from other anadromous populations. For management purposes, it is imperative to be able to discriminate among individual stocks so that weak stocks may be protected and harvest may be allocated equitably. Because of their sensitivity and resistance to environmentally-induced temporal variation, molecular approaches have been increasingly employed in stock identification studies. However, post-Pleistocene recolonization of the Hudson River must have occurred less than 10,000 years ago—a relatively brief period for genetic divergence among populations. We tested whether various measures of DNA variation between Hudson River populations and adjacent populations of Atlantic sturgeon, American shad, and striped bass were sufficient to discriminate among their conspecific populations. American shad populations surveyed for mtDNA variation were highly diverse genotypically, but genotypic frequencies among the populations of the Connecticut, Hudson, and Delaware rivers were statistically homogenous (p>0.05). In contrast, Atlantic sturgeon (surveyed for mtDNA variation) and striped bass (surveyed for mtDNA and nuclear DNA variation) populations of the Hudson River were not genotypically diverse, but they were differentiated from northern and southern populations. Our results suggest higher gene flow (and lesser homing fidelity) among American shad populations in comparison with the two other species.  相似文献   

4.
All available capture records of the endangered shortnose sturgeon,Acipenser brevirostrum, for the Delaware River Estuary from the early nineteeth century to the present were compiled. During 1817 through 1913 some 1,949 captures were reported, most as a bycatch of the shad gill net fishery. No documented captures during 1913 to 1954 were reported in the literature. Thirty-seven shortnose sturgeon were reported captured from 1954 through 1979, mostly incidental to fishery and ecological studies. Most specimens were taken in the upper tidal freshwater portion of the estuary (rkm 200–214). Seasonal-spatial distribution appeared similar to that observed for northern shortnose sturgeon populations. Taxonomic data obtained from seven specimens generally agreed with those from other drainages.  相似文献   

5.
The anadromous acipenserid Atlantic sturgeon Acipenser oxyrinchus was listed in 2012 under the U.S. Endangered Species Act as having four endangered and one threatened distinct population segment (DPS) in American waters. Anthropogenic activities outside of natal estuaries, particularly bycatch, may hinder the abilities of some populations to rebuild. Most Atlantic sturgeon are residential for their first 2–6 years within their natal estuaries, whereas older subadults and adults may migrate to non-natal estuaries and coastal locations. Previous studies demonstrated that subadults and adults aggregate during summer at locations in Long Island Sound (LIS) and its tributary, the Connecticut River; however, the population origin of these fish is unknown. Because of its geographic proximity and relatively robust population, we hypothesized that the LIS and Connecticut River aggregations were almost solely derived from the Hudson River. We used microsatellite nuclear DNA analysis at 11 loci and mitochondrial DNA control region sequence analyses to estimate the relative contributions of nine Atlantic sturgeon populations and the five DPS to these aggregations using individual-based assignment tests and mixed-stock analysis. From 64 to 73 % of specimens from LIS were estimated to be of Hudson origin. Similarly, 66–76 % of specimens from the Connecticut River were of Hudson origin. However, moderate numbers of specimens were detected from distant spawning populations in the southeastern DPS and from two populations once thought to be extirpated or nearly so, the James River (6–7.3 %), and the Delaware River (7.6–12 %). Additionally, specimens were detected from all five DPS in both the LIS and Connecticut River collections. These results highlight the difficulty of evaluating the status of individual Atlantic sturgeon populations because of the propensity of subadults and adults to migrate for extended duration to distant sites where they may be vulnerable to anthropogenic disturbances.  相似文献   

6.
Sampling in the upper tidal Delaware River between Trenton, New Jersey, and Philadelphia, Pennsylvania, from July 1981 through December 1984 demonstrated the existence of a significant population of shortnose sturgeon. The sturgeon aggregate in the river channel during daylight hours, especially in the area between Trenton and Florence, New Jersey (river km 211.8 to 198.8). Occurrence in the river downstream of Florence appears to be restricted by poor water quality during summer months. Sturgeon were present in the study area throughout the year, but largest numbers were collected from May though November. No spawning was observed during this study, but presence of males with milt suggests that spawning possibly occurs in the Trenton area. Preliminary population estimates (Peterson, Schnabel and Seber-Jolly) indicate an adult population of approximately 6,000–14,000 shortnose sturgeon occupying the upper tidal Delaware River.  相似文献   

7.
A turbidity maximum has been observed in the Kennebec estuary during mode rate and low flow conditions near the upstream limit of salinity intrusion. Hydrographic, ADCP, and transmissometer data were collected at different river flow levels and seasons during 1995–1998. The location of the tip of the salt intrusion changes dramatically and during high runoff may be flushed from the channel of the estuary along with the accumulated particles in the turbidity maximum. It is hypothesized that the estuarine turbidity maximum (ETM) was absent 18% of the time with occurrences in all seasons during 1993–1999 based on river flow volumes from the Kennebec and Androscoggin Rivers throughout the study period. When the flow is moderate and low, which occurred 73% of the time on average, a region of high turbidity can be found as far as 40 km upstream of the mouth. Suspended particulate loads are low in the ETM, on the order of tens of mg l−1 and may vary with the length of time that the ETM has been present.  相似文献   

8.
We evaluated the prevalence of partial migration, coexisting resident and migratory life history types, within six white perch (Morone americana) populations in sub-estuaries (Upper Bay, and Potomac, Choptank, Nanticoke, James, and York Rivers) of the Chesapeake Bay. Otolith stable isotope (δ18O) values were used to resolve fish habitat use along an estuarine salinity gradient and define resident or migratory behavior. The majority of adults within Upper Bay and Potomac River populations were resident, whereas individuals from the Choptank, Nanticoke, James, and York Rivers were predominantly migratory. Beyond population differences, large interannual variability in life history types was observed, likely due to differences in estuarine conditions that influence growth rate of individuals (e.g., temperature, zooplankton density). Because we observed partial migration in all study populations, we suggest that this trait is characteristic of this species, permitting plastic responses to variation in the estuarine environment.  相似文献   

9.
Long Island Sound (LIS), a large urban estuary in the northeastern USA, receives freshwater from many rivers along its northern shore. The size of these rivers varies widely in terms of basin area and discharge. The Regional Ocean Modeling System (ROMS) was applied with conservative passive tracers to identify the distribution, mixing, freshwater residence times, and storm response for all of LIS’s river systems during the summer of 2013. A watershed model was applied to overcome the lack of adequate river discharge observations for coastal watersheds. The Connecticut River was the largest contributor to riverine freshwater throughout the estuary despite its entry point near the mouth. The Connecticut River strengthened bulk stratification in the eastern LIS the most but acted to weaken stratification near the mouths of other rivers and in far western LIS by freshening waters at depth. The Housatonic and Hudson Rivers had the strongest influence on stratification in central and western LIS, respectively. Smaller coastal rivers were the most influential in strengthening stratification near the southwestern Connecticut shoreline. The influence of small coastal rivers was amplified after a major storm due to shorter storm response times relative to the larger rivers. Overall, river water was close to a well-mixed state throughout LIS, but more stratified near river mouths. Freshwater residence time estimates, meanwhile, indicated monthly to multi-seasonal time scales (43 to 180 days) and grew longer with greater distance from the LIS mouth.  相似文献   

10.
Data from sonic tracking during the period 1983–1987 enabled us to define the areas used and the seasonal pattern of movement by adult shortnose sturgeon (Acipenser brevirostrum) in the Delaware River. Tagged adults (n=28) ranged from 544 mm to 871 mm fork length and 1,510 g to 7,125 g. Twenty-six tags were carried for 7–225 d. Most of the tagged sturgeon were relocated in the tidal portion of the river. Sturgeon that overwintered in the upper tidal river near Trenton, New Jersey, began traveling upstream in late March to the nontidal river above Trenton where spawning presumably occurred from late March through April. After spawning, sturgeon traveled rapidly downstream into the tidal portion of the river near Philadelphia, Pennsylvania, where they remained through the end of May. Before the end of June, most sturgeon returned upstream and re-entered the upper tidal river near Trenton, where most apparently remained for the summer and winter. In general, the same pattern was apparent for both sexes. As a result of the intensive use of the river between Philadelphia to just above Trenton, any alterations or additional insults to the river should consider the impact on this endangered species.  相似文献   

11.
Ninety-four prespawning adult Atlantic sturgeon (Acipenser oxyrinchus) were sampled in the Hudson River for age, sex, body size, gonad weight, fecundity, mature oocyte size, and plasma concentrations of gonadotropins, sex steroids, and vitellogenin during the spring spawning migrations in 1992 and 1993. In males, the age and total length ranged from 12 yr to 19 yr and from 133 cm to 204 cm and in females from 14 yr to 36 yr and from 197 cm to 254 cm. The majority of males were 13–16 yr old, and females were 16–20 yr old. Some females had residual atretic ovarian bodies, presumably remaining from a previous spawning and indicating iteroparity. Pre-ovulatory condition was recognized by migration of the germinal vesicle or by germinal vesicle breakdown and by significantly elevated plasma gonadotropins, progesterone, and vitellogenin. All pre-ovulatory females were captured upriver from Hudson River kilometer 136. Individual fecundity ranged from 0.4 million to 2.0 million eggs and oocyte diameter from 2.4 mm to 2.9 mm, and both characters exhibited a significant (p<0.05) positive relationship with female body size. Iteroparous females, tentatively identified by the presence of atretic bodies remaining in the ovary from a previous spawning, had significantly (p<0.05) higher fecundity and produced larger eggs, compared with females spawning presumably for the first time.  相似文献   

12.
We quantified temporal and spatial variability in diets of 950 juvenile (age-0) striped bass in the Hudson River estuary. We used canonical correspondence analysis to assess the roles of temporal and spatial habitat variability in juvenile diet variation. We found that juvenile striped bass diets in the Hudson River were only modestly comparable to diets in other east coast estuaries. Among-year differences (51.4%) and spatial differences (41.9%) were substantially associated with juvenile striped bass diet. We found ontogeny (2.8%) and within-season variation (9.5%) to only weakly associate with diet variation. Our results indicate that an understanding of the temporal and spatial variation within the Hudson River estuary is vital in understanding variation in feeding by resident juvenile fish.  相似文献   

13.
This study examined the genetic diversity and composition of 15 populations of Zostera japonica in the Hii River system, Japan. Genetic and genotypic diversity were consistently higher in populations in the Ohashi River than those in Lake Nakaumi, and the local tidal movements may explain the observed patterns of genetic diversity. Pairwise fixation index values among the populations in Lake Nakaumi were higher than among those in the Ohashi River, even though the ranges of the distances among the populations in the two locations were almost the same. The gene flow from the Ohashi River populations was important for some populations in Lake Nakaumi. The low genotypic diversity and gene flow in Lake Nakaumi seemed similar to those of marginal populations. If this low genotypic diversity and genetic differentiation were partly caused by human activities, the promotion of gene flow should be taken into account in conserving the populations in Lake Nakaumi.  相似文献   

14.
The European sturgeon (Acipenser sturio) is an endangered diadromous fish species that spawns in the rivers in late spring and early summer. The juveniles spend their first years in the brackish waters (5‰ to 25‰) of the estuary zone before moving out to sea. This study describes the downstream migration pattern of juvenile sturgeon, belonging to the 1994 cohort, the only one born naturally in the Gironde basin, France since the end of the 1980s. During October 1994 to December 1996 the inland section of the Gironde estuary was sampled monthly by trawl (n=818 tows) and all European sturgeon caught (n=381) were marked and released. The first sturgeon of the 1994 cohort (TL=27 cm) were caught in early March 1995 in the zones furthest upstream. During their second fall of life, juveniles gradually acclimatized, and spread over a wide range of salinity conditions. A first incursion into marine water was also observed (at least for a few fish) by the end of the second winter. During this second period, sturgeon showed preference for two particular zones situated at 18 and 38 km, respectively, from the mouth of the estuary. These zones, belonging to two different salinity sectors of the estuary, did not appear to be any different to their neighbors with regards to depth and type of substrate. There were no significant size differences among estuarine zones. Seasonal movements of sturgeon seem to be motivated by a search for warmer temperatures. After a period of early acclimatization of 15 months, juvenile European sturgeon appear to be highly tolerant of salinity variations.  相似文献   

15.
We compiled information about the distribution of exotic organisms in the fresh waters of the Hudson River basin. At least 113 nonindigenous species of vertebrates, vascular plants, and large invertebrates have established populations in the basin. Too little was known about the past or present distributions of algae and most small invertebrates to identify exotic species in these groups. Most established exotic species in the Hudson River basin originated from Eurasia or the Mississippi-Great Lakes basins, and were associated with vectors such as unintentional, releases (especially escapes from cultivation), shipping activities (especially, solid ballast or ballast water), canals, or intentional releases. Rates of species invasions of fresh and oligohaline waters in the basin have been high (ca. one new species per year) since about 1840. For many well-studied groups, introduced species constitute 4% to nearly 60% of the species now in the basin. Although the ecological impacts of the invaders in the Hudson River basin have not been well studied, we believe that about 10% of the exotic species, have had major ecological impacts in the basin. Since, the rates, of entry and composition of exotic species in the Hudson basin are similar to those observed., previously for the Laurentian Great Lakes, invasions tended to occur earlier in the Hudson basin, probably reflecting the earlier history of human commerce. While most exotics have had negative impacts on local flora and fauna, some fish species have provided unique angling opportunities and important economic benefits.  相似文献   

16.
Although density-dependent growth and mortality are understood to play a large role in regulating populations of some young fish, many investigators report associations between striped bass population fluctuations and environmental variation, not density. One explanation is that mortality is primarily determined by size, which responds through growth to environmental conditions. Mathematically relating mortality to inverse size explains several aspects of striped bass biology. Numerical decline of the 1975 Hudson River cohort is well predicted. Simulated year-class strength responds more strongly to changes in growth and length at hatch than to direct mortality of eggs. The effect of changes in length at hatch and growth, rate on subsequent population size decreases as fish grow. Small changes in temperature or food density early in life could cause the reported association of year-class strength and environmental variation. Disappearance of larvae from an early spawning in the Hudson River in 1976 is attributed to decreasing water temperature, which decreased growth rate. Increased mortality of young striped bass may also result from sublethal exposure to toxicants that decrease growth rate and size at hatch. The approach to modeling population dynamics developed here should be valid for other estuarine and marine species.  相似文献   

17.
Gulf sturgeon are anadromous, spawning in freshwater and returning to the marine environment to feed. Herein, we document the marine distribution and timing of movement in and out of the marine environment of Gulf sturgeon natal to the Pascagoula and Pearl rivers (MS and LA). From 1999 to 2004, we attached sonic transmitters to 194 fish averaging 151 (MS) to 160 (LA) cm in fork length. We located 56 different Gulf sturgeon in the estuarine or marine environments, some multiple times. Fish were distributed nonrandomly, being found primarily in shallow water (mean = 3.9 m) in barrier island passes. Benthic samples taken at Gulf sturgeon telemetry location sites were dominated by Florida lancelets, sand dollars, annelids, haustoriid amphipods, and mollusks—all documented prey of Gulf sturgeon. Movement into salt water consistently occurred in October and November; movement back into rivers or low salinity estuaries was complete by the end of March.  相似文献   

18.
We investigated the geochemical characteristics of major, trace and rare earth elements and Sr–Nd isotope patterns of bed sediments from the headwaters and upper reaches of the six large rivers draining the Tibetan Plateau (the Jinsha River—Yangtze, Lancang River—Mekong, Nujiang River—Salween, Huang He—Yellow, Indus, and Yarlung Tsangpo—Brahmaputra). By using Ca/Al versus Mg/Al, La/Sc versus Co/Th, and 87Sr/86Sr versus εNd (0) binary differentiation diagrams of provenance, some typical contributors to the different catchment sediments can be identified. In the Three-River (the Jinsha, Lancang, and Nujiang Rivers) tectonomagmatic belt, acidic–intermediate-acidic volcanic rocks are very important provenance of sediments. Carbonate rocks and Permian Emeishan basalts are dominant in the Jinsha River. The Yellow River sediments have similar geochemical characteristics with loess in catchments. The Indus and Yarlung Tsangpo Rivers sediments are mainly from ultra-K volcanic rocks and Cenozoic granitoids widely distributed in the Indus–Yarlung suture. The intensity of chemical weathering in these river catchments is evaluated by calculating the chemical indices of alteration (CIA) of sediments and comparing them with bedrocks. The CIA values of the six river sediments are from 46.5 to 69.6, closing to those of bedrocks in the corresponding catchment, which indicates relatively weak chemical weathering intensity. Lithology, climate, and topography affect the chemical weathering intensity in these river catchments.  相似文献   

19.
Phylogeographic patterns of the SW Atlantic estuarine crab Neohelice granulata were examined using mitochondrial DNA cytochrome oxidase I sequences and analyzed together with morphometric data. Specimens were sampled during a 4-year period (2001?C2004) from 11 localities encompassing the full distributional range of this species along the SW Atlantic (22°57?? S to 42°25?? S). DNA sequences were obtained from 69 individuals belonging to seven localities, and morphometric variation in 12 continuous characters was analyzed for 646 crabs from ten localities. Strong genetic differentiation, consistent with a pattern of isolation-by-distance, was detected among all localities indicating that gene flow occurs mainly between neighboring populations. Analyses of molecular variance showed genetic subdivision between the southern (Argentina) and the northern (Brazil) sites, suggesting restricted gene flow at a regional scale. The genetic structure of this species could be divided into two distinct groups due to a limited gene flow between southern and northern regions as a consequence of larval dispersal patterns. Coastal currents in the vicinity of the Rio de la Plata likely act as a barrier to dispersal within the species range. Moreover, genetic data indicate that populations of N. granulata might have undergone a northward demographic expansion since the late Pleistocene. The morphometric analysis showed no geographical pattern of morphological differentiation, although there were differences among sampling sites.  相似文献   

20.
2008年塔里木河四条源流出山口天然径流量241.8×108m3,比多年平均值216.4×108m3多24.9×108m3,偏多11.5%,属偏丰水年;塔里木河阿拉尔站以上3条源流出山口天然径流量202.5×108m3,比多年平均值多19.6×108m3,偏多10.7%,属偏丰水年;开都河-孔雀河为38.83×108m3,比正常年份多5.33×108m3,属偏丰水年.四条源流入塔里木河总水量为29.52×108m3,占四条源流出山口天然径流总量的12.2%.其中,阿拉尔站以上3条源流入塔里木河水量为24.74×108m3,占三条源流出山口天然径流总量的12.2%.2008年塔里木河干流上游段耗水量21.11×108m3,占阿拉尔站年径流量的72.3%,是塔里木河干流最大的耗水区段;中游段耗水量7.63×108m3,占阿拉尔站年径流量的26.1%;下游段耗水量0.46×108m3,占阿拉尔站年径流量的1.6%.四条源流出山口来水量为偏丰水年,但由于源流耗水严重,入塔里木河水量减少成为特枯水年,2008年暂不向干流下游应急生态输水.  相似文献   

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