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1.
Estuarine nursery areas are critical for successful recruitment of tautog (Tautoga onitis), yet they have not been studied over most of this species' range. Distribution, abundance and habitat characteristics of young-of-the-year (YOY, age 0) and age 1+juvenile tautog were evaluated during 1988–1992 in the Narragansett Bay estuary, Rhode Island, using a 16-station, beach-seine survey. Estuary-wide abundance was similar among years. Greatest numbers of juveniles were collected at northern Narragansett Bay stations between July and September. Juvenile abundances varied with density of macroalgal and eelgrass cover; abundances ranged from 0.03 fish per 100 m2 to 8.1 fish per 100 m2. Although juveniles use eelgrass, macroalgae is the dominant vegetative cover in Narragansett Bay. Macroalgal habitats play a previously unrealized, important role and contribute to successful recruitment of juvenile tautog in Narragansett Bay. Juvenile abundances did not vary with sediment type or salinity, but were correlated with surface water temperature. Fish collected in June were age 1+ juveniles from the previous year-class (50–167 mm TL) and these declined in number after July or August. The appearance of YOY (25–30 mm TL) in July and August was coincident with the period of their greatest abundances. A precipitous decline in abundance occurred by October because of the individual or combined effects of mortality and movement to alternative habitats. Based on juvenile abundance, a previously unidentified spawning area was noted in Mount Hope Bay, a smaller embayment attached to the northeastern portion of Narragansett Bay. In August 1991, Hurricane Bob disrupted juvenile sise distribution and abundance, resulting in reduced numbers of YOY collected after the storm and few 1+ juveniles in 1992.  相似文献   

2.
Seasonality and abundance of ichthyoplankton in great South Bay,New York   总被引：1，自引：0，他引：1  
The seasonality and abundance patterns of ichthyoplankton were investigated during 1985–1986 in Great South Bay, New York, USA. Eggs representing 17 species and larvae representing 23 species of fish were identified. Bay anchovy, Anchoa mitchilli, was the most abundant ichthyoplankter, comprising >96% of the eggs and >69% of the larvae collected. Bay anchovy spawned throughout the bay from late May through August, with peak baywide densities of >200 eggs and 6 larvae m?3. Eggs of windowpane flounder (Scophthalmus aquosus) ranked second in abundance and were present in both spring and fall. Other dominant larvae were winter flounder (Pleuronectes americanus) and American sand lance (Ammodytes americanus). Their combined density reached 8 m?3 and accounted for the winter peak in larvae. The seasonality of abundance of larval fish was strongly correlated with reported densities of copepod nauplii prey.  相似文献   

3.
We used two methods and existing field survey data to link juvenile fish and their habitats. The first method used seine survey data collected monthly from July to October 1988–1996 at fixed stations in Narragansett Bay, Rhode Island. Thirteen fish species making up 1% or more of the catch were analyzed by principal components analysis for two time periods: July–August and September–October. The stations were then plotted by their principal component scores to identify station groupings and habitat types. The second method used environmental data collected in July and August 1996 at the established survey stations in a principal components analysis. The stations and 13 most abundant species were plotted by principal components scores resulting from the environmental data. For the environmental data, the first two principal components explained 59% of the variance. The first principal component described the amount of energy shaping the habitat and was positively correlated with salinity, dissolved oxygen, current flow, and slope, and negatively correlated with silt. The second component was positively correlated with depth and silt, and negatively correlated with dissolved oxygen. The environmental data grouped the stations according to their distance from the ocean and three habitat types emerged. The uppermost station was a silty barren having low salinities and dissolved oxygen. Three other stations grouped together as low energy, protected habitats with sandy substrates. Lower bay stations had higher salinities, higher dissolved oxygen, higher flow rates, greater slopes, and larger size substrates, mostly cobble and gravel. Results from the fish data grouped the stations similarly. Combining results from both datasets revealed the uppermost station had the highest catches, most species, and greatest number of winter flounder (Pseudopleuronectes americanus) juveniles. Plots of winter flounder catches with principal component scores from the environmental data indicated the winter flounder distribution in the bay has shrunk from baywide to mostly the upper estuary near their primary spawning grounds. Results illustrate the value of coupling historic fish survey data with environmental measurements for identifying previously undervalued habitats important to fish.  相似文献   

4.
Liver sections of winter flounder (Pseudopleuronectes americanus) collected from Jamaica Bay and Shinnecock Bay, New York, in 1989, were examined microscopically to determine the pervasiveness of liver lesions observed previously in Jamaica Bay winter flounder. Neoplastic lesions were not detected in fish from Jamaica Bay or the Shinnecock Bay reference site. Twenty-two percent of Jamaica Bay winter flounder examined (n=103) had unusual vacuolization of hepatocytes and biliary pre-ductal and ductal cells (referred to hereafter as the vacuolated cell lesion). The lesion, identical to that found in 25% of Jamaica Bay winter flounder examined in 1988, has previously been identified in fishes taken from highly polluted regions of the Atlantic coast (e.g., Boston Harbor, Massachusetts, and Black Rock Harbor, Connecticut). Prevalence of the vacuolated cell lesion in winter flounder from Jamaica Bay was significantly greater (p<0.0001) than in 102 specimens collected from Shinnecock Bay. Current scientific literature indicates vacuolated hepatocytes and cholangiocytes are chronically injured and that the extent of their deformity is consistent with the action of a hepatotoxicant. The high prevalence of vacuolated hepatocytes in Jamaica Bay winter flounder and absence of the lesion in flounder from reference sites strongly supports the hypothesis that this impairment is a manifestation of a toxic condition in at least some portions of Jamaica Bay.  相似文献   

5.
Collections of winter flounder (Pseudopleuronectes americanus) larvae were made biweekly from March to May in 1999 and 2000 in the Navesink River-Sandy Hook Bay estuarine system, New Jersey, to determine stage-specific spatial and temporal variability in diets. Relatively high percentages of larvae with empty guts were found at low water temperatures. Percentages of empty guts did not differ by larval stage (preflexion and postflexion) or region of collection (river and bay). There was high intraregional variability in percentages of larvae with empty guts. Nauplii, invertebrate eggs, and polychaete larvae were dominant prey items followed by tintinnids, bivalve and gastropod veligers, and diatoms. Ontogenetic dietary shifts were evident in both years. Preflexion winter flounder largely consumed nauplii, invertebrate eggs, and tintinnids; postflexion winter flounder consumed the largest prey (polychaete larvae) but also retained small prey items in their diets. Water temperature significantly affected the percentages of larvae feeding on nauplii (p<0.05) and tintinnids (p<0.08) in 2000. Region of collection was not significantly related to diets because of high intraregional variability. Fine scale spatial (within regions, stations were approximately 3 km apart) and temporal (weeks) dietary variation of larval winter flounder could result in accompanying variation in development, growth stage duration, and survival.  相似文献   

6.
The benthic amphipod Ampelisca abdita dominates mudbottom benthic communities in Jamaica Bay (New York). In this study, we investigated the trophic role of Ampelisca in relation to winter flounder (Pleuronectes americanus) populations—the most frequently trawled fish species in Jamaica Bay. Flounders collected by trawl during summer 1989 were primarily juveniles. Stomach analyses indicated that amphipod crustaceans contributed >99% of prey individuals, with A. abdita making up 88%. Density and size frequency analyses of Ampelisca at three sites indicated two overlapping cohorts: a spring cohort released in June and a summer cohort released in late summer. Most overwintering survivors come from the summer cohort. Secondary production of Ampelisca was estimated at three sites using the cohort summation of biomass method. Estimates of annual production ranged from 25 g DW to 47 g DW m?2 (mortality + residual biomass); production due to growth ranged from 20 g DW to 26 g DW. Simulations of spring cohort production using a range of plausible growth and mortality schedules suggested that P∶B may be more sensitive to variability in survivorship than growth. Ampelisca secondary production in Jamaica Bay is compared with other amphipod species and with macrobenthic production in other coastal and estuarine systems. We conclude that observed amphipod production is probably more than sufficient to support local winter flounder populations in Jamaica Bay, and we speculate that high nutrient loadings may indirectly stimulate amphipod production. *** DIRECT SUPPORT *** A01BY058 00010  相似文献   

7.
Six synoptic samplings of nutrient concentrations of the water column and point-source inputs (rivers, sewage treatment plants) were conducted in the Seekonk-Providence River region of Narragansett Bay. Concentrations of nutrients (NH4 +, NO2 ?+NO3 ?, PO4 ?3, dissolved silicon, particulate N, particulate C) were predicted using a conservative, two-layer box model in order to assess the relative influence of external inputs and internal processes on observed concentrations. Although most nutrients were clearly affected by processes internal to the system, external input and mixing explained most of the variability in and absolute magnitude of observed concentrations, especially for dissolved constituents. In the bay as a whole, two functionally distinct regions can now be identified: the Seekonk-Providence River, where dissolved nutrient concentrations are externally controlled and lower Narragansett Bay where internal processes regulate the behavior of nutrients. A preliminary nitrogen budget suggests that the Seekonk-Providence River exports some 95% of the nitrogen entering the system via point sources and bottom water from upper Narragansett Bay.  相似文献   

8.
The distribution, hatching dates, growth, and food habits of larval and juvenile red drum (Sciaenops ocellatus) in Tampa Bay, Florida, are described. From September 1981 through November 1983, 800 larvae and 7,536 juveniles (98%<100 mm SL) were collected, primarily with plankton nets and bag seines. Analysis of otoliths and length-frequency distributions indicate that spawning took place from mid-August through late November with a major peak during October in 1981 and 1982. Larvae became less abundant, but increased in size, from the mouth to the upper bay, indicating that spawning took place in the bay mouth or nearshore waters. At about 8 mm SL (17 days old) larvae settled out along the bay shore before migrating toward low salinity backwater areas. Juveniles grew to about 55 mm SL by the end of December and 303 mm SL by the end of their first year. Young red drum gradually moved back into the bay with increased size and age. Eighty-five percent of larval stomachs, examined were empty; those with food contained copepods almost exclusively. Fewer than 7% of juvenile stomachs were empty. Small juveniles fed primarily on mysids, amphipods, and shrimp, whereas larger juveniles fed more on crabs and fish. Changes in diet were noted with growth, but few differences were seen among areas or habitat types.  相似文献   

9.
A long-term (2002–2011), spatially robust, ichthyoplankton sampling program conducted in the New York/New Jersey Harbor produced 3,033 epibenthic samples from which the relationships between winter flounder egg and larval distributions and environmental parameters were examined. Variations in water temperature, sediment characteristics, and tidal phase were all significantly associated with egg distributions. Inferences about spawning habitats were based on the presence of early-stage eggs (ES1 and ES2). In the Lower Bay (LB), these habitats were primarily non-channel and characterized by more sandy substrates, averaging 96.5 % sand, 2.3 % silt/clay, 0.2 % total organic carbon (TOC), and shallower water (average depths of 5.3 m) compared to LB non-channel stations without ES1 and ES2 eggs (50.2 % sand, 42.0 % silt/clay, 2.1 % TOC, and 7.9 m depths). Occurrences of all stages of eggs in channels were associated with strong tides and severe cold winter water temperatures. These conditions increase the probability of egg transport from shallow spawning sites through increased vertical mixing (strong tides) and delayed development that prolongs the risk of displacement (cold temperatures). Yolk-sac (YS) and Stage-2 larvae were smaller in 2010 when spring water temperatures were highest. Overall, YS larval size decreased with warmer winters (cumulative degree-days for the month preceding peak YS larval collections, r 2?=?0.82, p?<?0.05). In all years, YS larvae collected in LB were smaller and Stage-3 larvae collected in channels were larger and possibly older than those from non-channel habitat. Because estuarine winter flounder populations are highly localized, adverse effects experienced during egg and larval stages are likely to propagate resulting in detrimental consequences for the year class in the natal estuary.  相似文献   

10.
The objective of this study was to gain baseline population data on the genetic diversity and differentiation of eelgrass (Zostera marïna L.) populations in the Chesapeake and Chincoteague bays. Natural and transplanted eelgrass beds were compared using starch gel electrophoresis of allozymes. Transplanted eelgrass beds were not reduced in genetic diversity compared with natural beds. Inbreeding coefficients (FIS) indicated that transplanted eelgrass beds had theoretically higher levels of outcrossing than natural beds, suggesting the significance of use of seeds as donor material and of seedling recruitment following transplantation diebacks. Natural populations exhibited very great genetic structure (FST=0.335), but transplanted beds were genetically similar to the donor bed and each other. Genetic diversity was lowest in Chincoteague Bay, reflecting recent restoration history since the 1930s wasting disease and geographical isolation from other east coast populations. These data provide a basis for developing a management plan for conserving eelgrass genetic diversity in the Chesapeake Bay and for guiding estuary-wide restoration efforts. It will be important to recognize that the natural genetic diversity of eelgrass in the estuary is distributed among various populations and is not well represented by single populations.  相似文献   

11.
This study evaluated the relative importance of the Narragansett Bay estuary (RI and MA, USA), and associated tidal rivers and coastal lagoons, as nurseries for juvenile winter flounder, Pseudopleuronectes americanus, and summer flounder, Paralichthys dentatus. Winter flounder (WF) and summer flounder (SF) abundance and growth were measured from May to October (2009–2013) and served as indicators for the use and quality of shallow-water habitats (water depth <1.5–3.0 m). These bioindicators were then analyzed with respect to physiochemical conditions to determine the mechanisms underlying intraspecific habitat selection. WF and SF abundances were greatest in late May and June (maximum monthly mean?=?4.9 and 0.55 flounder/m2 for WF and SF, respectively) and were significantly higher in the tidal rivers relative to the bay and lagoons. Habitat-related patterns in WF and SF abundance were primarily governed by their preferences for oligohaline (0.1–5 ppt) and mesohaline (6–18 ppt) waters, but also their respective avoidance of hypoxic conditions (<4 mg DO/L) and warm water temperatures (>25 °C). Flounder habitat usage was also positively related to sediment organic content, which may be due to these substrates having sufficiently high prey densities. WF growth rates (mean?=?0.25?±?0.14 mm/day) were negatively correlated with the abundance of conspecifics, whereas SF growth (mean?=?1.39?±?0.46 mm/day) was positively related to temperature and salinity. Also, contrary to expectations, flounder occupied habitats that offered no ostensible advantage in intraspecific growth rates. WF and SF exposed to low salinities in certain rivers likely experienced increased osmoregulatory costs, thereby reducing energy for somatic growth. Low-salinity habitats, however, may benefit flounder by providing refugia from predation or reduced competition with other estuarine fishes and macroinvertebrates. Examining WF and SF abundance and growth across each species’ broader geographic distribution revealed that southern New England habitats may constitute functionally significant nurseries. These results also indicated that juvenile SF have a geographic range extending further north than previously recognized.  相似文献   

12.
In a 3-yr study, late prespawning winter flounder were collected from various stations in Long Island Sound (three of them heavily urbanized) and spawned in the laboratory. For comparative purposes, flounder from two sites in the Boston Harbor area were similarly treated in 1987 and 1988. Of the stations in Long Island Sound, New Haven Harbor alone consistently produced low percent viable hatch and small larvae. Boston Harbor produced the smallest larvae of all sites. There were no significant station-to-station differences in lipid utilization during larval development; yolk reserves at stations showing a low percent viable hatch, small larvae, and low embryonic development rate were probably used in part for stress metabolism. No significant differences in concentrations of polychlorinated biphenyls for collections from Long Island Sound were found either in livers of spawned fish, in sediments, or in eggs of winter flounder. The very low metal concentrations in winter flounder eggs showed no relation to the degree of metal contamination found at stations in Long Island Sound and Boston Harbor.  相似文献   

13.
To determine the genetic structure of the bay anchovy (Anchoa mitchilli) within Chesapeake Bay, 16 isozyme systems encoding 21 loci for 20 population were examined using horizontal starch gel electrophoresis. Contingency Chisquare analysis revealed significant allelic frequency differences at nine loci (AAT-1, AAT-2, ALD-1, CPK-2, GAP-1, GLY-1, LDH-1, MDH-1, and MDH-2). Two loci, ALD-1 and MDH-1, were responsible for nine of 14 tests not conforming to Hardy-Weinberg expectations, with some of these deviations attributed to possible scoring and/or sampling error. Estimates for mean average heterozygosity were relatively high, ranging from 0.40 to 0.096, with 33–57% of the loci polymorphic. A low Fst value (0.041) along with high genetic identity estimates (I=0.997) indicated little substructuring of bay anchovy populations within Chesapeake Bay.  相似文献   

14.
During two years of sampling, 747 larval and 1,379 juvenile spotted seatrout,Cynoscion nebulosus, were collected in Tampa Bay, Florida; 93% were less than 75 mm SL. Length-frequency distributions and otolith analysis showed that spawning took place from early April until late October. Two seasonal spawning peaks (spring and summer) were made up of many smaller peaks, apparently timed with moon phases. Plankton samples contained larvae that measured up to about 7 mm SL (17 d old). Larvae collected from an upper bay station were less numerous and larger than those collected at other stations. The presence of small larvae from middle and lower bay stations indicated that spawning probably took place from the middle bay to nearshore Gulf waters. Juveniles used seagrass beds as their major habitat, but they were also found in unvegetated backwaters. Spotted seatrout grew to about 35 mm SL in 2 months, 84 mm SL in 4 months, and 140 mm SL in 6 months. Eighty-five percent of the alimentary tracts in larvae were empty; those with food contained primarily copepods. Eleven percent of the stomachs of juveniles were empty. Fish and shrimp were the most important food groups in the diets of fish >15 mm SL. Intraspecific comparisons of diets showed high dietary overlap between larval fish and those measuring 8–15 mm SL and among size classes >15 mm SL.  相似文献   

15.
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.  相似文献   

16.
Seagrass populations are in decline worldwide. Eelgrass (Zostera marina L.), one of California’s native seagrasses, is no exception to this trend. In the last 8 years, the estuary in Morro Bay, California, has lost 95% of its eelgrass. Population bottlenecks like this one often result in severe reductions in genetic diversity; however, this is not always the case. The decline of eelgrass in Morro Bay provides an opportunity to better understand the effects of population decline on population genetics. Furthermore, the failure of recent restoration efforts necessitates a better understanding of the genetic underpinnings of the population. Previous research on eelgrass in California has demonstrated a link between population genetic diversity and eelgrass bed health, ecosystem functioning, and resilience to disturbance and extreme climatic events. The genetic diversity and population structure of Morro Bay eelgrass have not been assessed until this study. We also compare Morro Bay eelgrass to Bodega Bay eelgrass in Northern California. We conducted fragment length analysis of nine microsatellite loci on 133 Morro Bay samples, and 20 Bodega Bay samples. We found no population differentiation between the remaining beds in Morro Bay and no difference among samples growing at different tidal depths. Comparisons with Bodega Bay revealed that Morro Bay eelgrass contains three first-generation migrants from the north, but Morro Bay remains considerably genetically differentiated from Bodega Bay. Despite the precipitous loss of eelgrass in Morro Bay between 2008 and 2017, genetic diversity remains relatively high and comparable to other populations on the west coast.  相似文献   

17.
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18.
A length-based model for calculating growth and mortality of juvenile winter flounder (Pseudopleuronectes americanus) populations has been developed. This model is based on work by Sullivan et al. (1990) and incorporates the von Bertalanffy growth equation, including stochasticity in growth, and a mortality rate that decreases exponentially with size. The length-based model was fit to observed size-frequency distributions, and model likelihood profiles were generated to produce 95% confidence intervals about parameter estimates. We analyzed size-frequency distributions of 3 to 15 cm juvenile winter flounder, collected with a 1-m beam trawl, at monthly intervals from June to October during 1993 and 1994. Growth rates were higher at a contaminated site, New Haven Harbor, than at a clean site, the Connecticut River estuary, however, the parameter estimates had overlapping 95% confidence intervals. Mortality rates were similar at the two sites.  相似文献   

19.
We evaluated nekton habitat quality at 5 shallow-water sites in 2 Rhode Island systems by comparing nekton densities and biomass, number of species, prey availability and feeding, and abundance of winter flounderPseudopleuronectes americanus. Nekton density and biomass were compared with a 1.75-m2 drop ring at 3 sites (marsh, intertidal, and subtidal) in Coggeshall Cove in Narragansett Bay and two subtidal sites (eelgrass and macroalgae) in Ninigret Pond, a coastal lagoon. We collected benthic core samples and examined nekton stomach contents in Coggeshall Cove. We identified 16 species of fish, 16 species of crabs, and 3 species of shrimp in our drop ring samples. A multivariate analysis of variance indicated differences in total nekton, invertebrates, fish, and winter flounder across the five sites. Relative abundance of benthic invertebrate taxa did not match relative abundance of prey taxa identified in the stomachs. Nonmetric multidimensional scaling plots showed groupings in nekton and benthic invertebrate prey assemblages among subtidal, intertidal, and marsh sites in Coggeshall Cove. Stepwise multiple regression indicated that biomass of macroalgae was the most important variable predicting abundance of nekton in Coggeshall Cove, followed by elevation and depth. In Rhode Island systems that do not experience chronic hypoxia, macroalgae adds structure to unvegetated areas and provides refuge for small nekton. All sites sampled were characterized by high abundance and diversity of nekton pointing to the importance of shallow inshore areas for production of fishes and decapods. Measurements of habitat quality should include assessment of the functional significance of a habitat (this can be done by comparing nekton numbers and biomass), some measure of habitat diversity, and a consideration of how habitat quality varies in time and space.  相似文献   

20.
Sampling theC. septemspinosa population of the Mystic River Estuary simultaneously in deep water and along the shoreline indicated that this population has two major reproductive periods. Berried females move into the estuary in early spring and late autumn to hatch their eggs. Two-and three-year-old females produce the larvae in the spring and 1.0- to 1.5-year-old females give rise to the larvae in winter. All larvae are carried seaward by the tidal currents and eventually settle as juveniles in the deep water near the mouth of the estuary or on the continental shelf. Juveniles from the spring hatch migrate to the shallow shoreline where they grow, rapidly, 0.15 mg/day. Those that hatch during the late autumn do not migrate shoreward. A model of this life cycle and evidence to support two recruitment mechanisms that involve inshore migration of adults and the offshore drift of the larvae are presented.  相似文献   

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