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1.
The blue crab, Callinectes sapidus, is an ecologically and economically valuable species in Chesapeake Bay. Field surveys and laboratory experiments indicate that blue crab mortality is significant during severe winters. We applied a temperature and salinity-dependent survival model to empirical temperature and salinity data to explore spatial and interannual patterns in overwintering mortality. Harmonic regression analysis and geostatistical techniques were used to create spatially explicit maps of estimated winter duration, average temperature, average salinity, and resulting crab survival probability for the winters of 1990–2004. Predicted survival was highest in the warmer, saline waters of the lower Bay and decreased with increasing latitude up bay. There was also significant interannual variation with survival being lowest after the severe winters of 1996 and 2003. We combine the survival probability maps with maps of blue crab abundance to show how winter mortality may reduce blue crab abundance prior to the start of the harvesting season. 相似文献
2.
Habitat use,temporal abundance variability,and diet of blue crabs from a New Jersey estuarine system
In a long-term, spatially comprehensive beam trawl survey of the Navesink River-Sandy Hook Bay estuary, the blue crabCallinectes sapidus was one of the most abundant species. Seasonal changes in abundance were evident, with low abundances in summer followed
by peak abundances in the fall, after juveniles recruited to the estuary. We saw no long-term trends in abundance during the
5 yr study. Location in the navesink River or Sandy Hook Bay explained most of the variance in abundance within any one survey.
In diet analyses, we found evidence of cannibalism in all seasons, but in the size range of crabs caught in this study (10–180
mm), we did not find a relationship between cannibalism and juvenile crab abundance. Within surveys, crabs divided into 20
mm size categories showed no sizerelated differences in location within the estuary or among 7 habitat types examined (algae
bed, amphipod bed, beach, channel, marsh edge, mid-depth, and sandbar). Channels and sandbars tended to exhibit lower crab
abundance than other habitats. Shallow habitats with and without cover were equally preferred by juvenile blue crabs, implying
that the presence of structure was not critical. Spatial models of crab abundance (<- 80 mm carapace width) to environmental
data were fit from several seasons of intensive sampling in the Navesink River-Sandy Hook Bay estuary between summer 1996
and spring 1998. These models indicated that fine-grained sediments, tmmperature, depth, and salinity were good indicators
of crab abundance in spring, summer, and fall. Using these spatial models and environmental data collected in subsequent seasons
(summer 1998−fall 1999), we were able to predict blue crab abundance in the river as evidenced by significant correlations
between predicted and observed abundances. For the size range of crabs examined here, physical conditions may be as important
as structural habitat types or cannibalism in determining habitat use in northerly estuaries. 相似文献
3.
A study was conducted to define winter distribution patterns of blue crabs,Callinectes sapidus, in the lower Chesapeake Bay and to relate these patterns to environmental variation. During February 1986 a stratified random survey was conducted to examine the distribution of blue crabs with respect to three major habitat types: 1) high energy, wave- and tide-dominated, spits and shoals; 2) moderate energy, tide-dominated basins; and 3) variable energy, tide-dominated or quiescent channels (natural or cut). Each major habitat type was further stratified on the basis of location (to account for possible salinity effects), resulting in a total of 17 habitat-stratum combinations. Blue crabs exhibited significant differences in abundance among habitats. Crabs were most abundant in the basin habitat and least abundant in the shoal and spit habitat. A posteriori evaluations of abundance patterns in relation to sediment type and depth showed that crabs were significantly more abundant where sediments contained between 41 and 60% sand and at depths exceeding 9 m. The sampled population of blue crabs was dominated by mature females. There were no significant differences in crab sex ratios between habitats, but significant differences between two fixed sites sampled through the winter showed that there were proportionately more male crabs at the western site than there were at the eastern site. The observed patterns indicate that some differential habitat utilization occurs and that overwintering female crabs are found preferentially in areas characterized by moderate energy regimes and fine, but sandy sediments. 相似文献
4.
Atlantic horseshoe crabs,Limulus polyphemus, are currently harvested for biomedical, scientific, and bait purposes. In recent years, changes in population abundance
and magnitude of harvesting have raised concerns about the status of this resource. We found horseshoe crab harvest in Pleasant
Bay, Massachusetts, was selective by sex and size. Biomedical harvest preferred larger individuals and females, the scientific
harvest preferred smaller individuals and males, and the bait harvest preferred females. Total 2001 harvest for all purposes
accounted for the mortality of ∼1–2% the adult population. Biomedical harvest accounted for the greatest loss of horseshoe
crabs from Pleasant Bay, ∼1–1.6% of the total population. Although biomedical harvest had the lowest associated mortality
rate (∼10–15%), many more crabs were harvested from Pleasant Bay for biomedical purposes than for other uses. The scientific
harvest accounted for the mortality of ∼0.4% of the population, and bait harvest accounted for the smallest mortality at ∼0.06%
of the population. Harvest mortality rate was estimated to be lower in Pleasant Bay than in other Cape Cod areas and may be
lower than natural mortality in the population. This study is the first qualitative investigation of commercial harvest on
horseshoe crab populations and emphasizes that harvest pressures on different populations need to be individually evaluated. 相似文献
5.
Estuarine salinity distributions reflect a dynamic balance between the processes that control estuarine circulation. At seasonal and longer time scales, freshwater inputs into estuaries represent the primary control on salinity distribution and estuarine circulation. El Niño-Southern Oscillation (ENSO) conditions influence seasonal rainfall and stream discharge patterns in the Tampa Bay, Florida region. The resulting variability in freshwater input to Tampa Bay influences its seasonal salinity distribution. During El Niño events, ENSO sea surface temperature anomalies (SSTAs) are significantly and inversely correlated with salinity in the bay during winter and spring. These patterns reflect the elevated rainfall over the drainage basin and the resulting elevated stream discharge and runoff, which depress salinity levels. Spatially, the correlations are strongest at the head of the bay, especially in bay sections with long residence times. During La Niña conditions, significant inverse correlations between ENSO SSTAs and salinity occur during spring. Dry conditions and depressed stream discharge characterize La Niña winters and springs, and the higher salinity levels during La Niña springs reflect the lower freshwater input levels. 相似文献
6.
Trotline blue crab (Callinectes sapidus) fishermen in the Patuxent, Chester, and Choptank tributaries of Chesapeake Bay set their gear in areas where the water quality,
characterized by average mid-channel bottom dissolved oxygen, varies across the river systems and over the fishing season.
Two harvest production models are developed to capture the potential effects of this source of environmental stress. One model
treats the impact of water quality as influencing the availability of crabs to the gear, while the second treats the impact
as another source of mortality. Both models are estimated assuming that dissolved oxygen has no effect on crab harvests above
an upper threshold of 5 mg I−1. Contrary to the mortality model, the availability model produces estimates that are consistent with our prior beliefs that
productivity will be negatively impacted by poor water quality. To determine the percentage of the available crab stock in
an area that will be harvested by a given amount of gear under different water quality conditions a simulation of the availability
model is developed. The simulations show that a decline in average mid-channel bottom dissolved oxygen in the Patuxent River
to 4 mg I−1 may lead to a 48% decline in the percentage of the blue crab population in the area that will be harvested with the same
amount of fishing effort. 相似文献
7.
Thomas J. Miller 《Estuaries and Coasts》2001,24(4):535-544
Blue crab (Callinectes sapidus) plays an important ecological and economic role in estuaries from South America to New England. It supports a large commercial fishery in the United States with approximately one third of the landings taken from Chesapeake Bay. I developed a stage-based matrix model of the blue crab population to address three key questions: What is the ability of blue crab populations to support sustainable exploitations? What stages of the life cycle are most important in regulating the dynamics of the populations? And specific of the Chesapeake Bay, what is the importance of a winter dredge fishery in determining long-term sustainability of the crab population? The model indicated that with the current pattern of exploitation blue crab populations are able to sustain a total instantaneous mortality rate (Z)～0.7. If the natural mortality rate is estimated for a maximum life expectancy of 8 yr, this translates to moderate levels of exploitation (F<0.32). This value is less than the current estimate of exploitation in Chesapeake Bay (0.9–1.1) indicating that the level of exploitation in this system needs to be reduced to avoid overfishing. Transitions to and from small age-1 crabs were shown to be important in regulating the overall dynamics of the population. The egg production realized by large adults was also shown to be an important regulatory process. The model indicated that reductions in the winter dredge fishery would have a substantial role in ensuring the long-term sustainability of the population. Reductions in other sectors of the fishery are also required to ensure sustainability. 相似文献
8.
Valeria A. Guinder Juan Carlos Molinero Celeste M. López Abbate Anabela A. Berasategui Cecilia A. Popovich Carla V. Spetter Jorge E. Marcovecchio Rubén H. Freije 《Estuaries and Coasts》2017,40(1):95-104
Understanding phytoplankton species-specific responses to multiple biotic and abiotic stressors is fundamental to assess phenological and structural shifts at the community level. Here, we present the case of Thalassiosira curviseriata, a winter-blooming diatom in the Bahía Blanca Estuary, Argentina, which displayed a noticeable decrease in the past decade along with conspicuous changes in phenology. We compiled interannual field data to assess compound effects of environmental variations and grazing by the invasive copepod Eurytemora americana. The two species displayed opposite trends over the period examined. The diatom decreased toward the last years, mainly during the winters, and remained relatively constant over the other seasons, while the copepod increased toward the last years, with an occurrence restricted to winter and early spring. A quantitative assessment by structural equation modeling unveiled that the observed long-term trend of T. curviseriata resulted from the synergistic effects of environmental changes driven by water temperature, salinity, and grazing. These results suggest that the shift in the abundance distribution of T. curviseriata toward higher annual ranges of temperature and salinity—as displayed by habitat association curves—constitutes a functional response to avoid seasonal overlapping with its predator in late winters. The observed changes in the timing and abundance of the blooming species resulted in conspicuous shifts in primary production pulses. Our results provide insights on mechanistic processes shaping the phenology and structure of phytoplankton blooms. 相似文献
9.
Much effort has been directed recently at restoring marshes, by the removal of the invasive common reed,Phragmites australis, yet it is not clear how fish and invertebrates have responded either to the invasion ofPhragmites or to marsh restoration. The blue crab,Callinectes sapidus, uses marsh habitats during much of its benthic life. We investigated the response of blue crabs toPhragmites invasion and restoration efforts by comparing crab abundance (catch per unit effort), mean size and size frequency distribution,
sex ratio, and molting of crabs in three physically similar areas differing in marsh vegetation;Spartina-dominated,Phragmites-dominated, and a treated area (Phragmites removed and now dominated bySpartina) in one marsh in the upper portion of Delaware Bay. Field sampling occurred monthly (April to November) from 1999 to 2001
using replicate daytime otter trawls in large marsh creeks. Crabs were categorized by carapace width into recruits (<30 mm),
juveniles (30–115 mm), and adults (>115 mm). Juveniles dominated the system, representing 69.4% of all crabs. Similar monthly
increases in mean size and molting patterns during the growing season (May–August) occurred inSpartina (natural and treated sites) andPhragmites sites suggesting that, subtidal habitats, used for molting, in these areas do not differ. More juveniles in the feeding molt
stage (i.e., intermolt) than in other molt stages and more recruits predominantly in the feeding molt stage than adults were
inSpartina, suggesting differences in the marsh surfaces used as feeding habitats withSpartina being preferred. Sex ratios of each life history stage were skewed towards males, but this was related to the low salinity
of Alloway Creek, rather than marsh surface vegetation. Our results suggest that marsh surface vegetation influences the way
blue crabs use marsh surface habitats, thus restoration efforts focusing on changing vegetation type may have a positive influence
on blue crabs. 相似文献
10.
Marshes are important habitats for various life history stages of many fish and invertebrates. Much effort has been directed at restoring marshes, yet it is not clear how fish and invertebrates have responded to marsh restoration. The blue crab,Callinectes sapidus, uses marsh habitats during much of its benthic life. We investigated the response of blue crabs to marsh restoration by comparing crab abundance (catch per unit effort), mean size and size frequency distribution, sex ratio, and molt stages of crabs in recently restored marshes that were former salt hay farms to that of adjacent reference marshes with similar physical characteristics in the mesohaline portion of Delaware Bay. Field sampling occurred monthly (April–November) in 1997 and 1998 using replicate daytime otter trawls in large marsh creeks and weirs in smaller intertidal marsh creeks. Blue crabs were either equal or more abundant, the incidence of molting was in most months similar, and population sex ratios were indistinguishable in restored and reference marshes, suggesting that the restored areas attract crabs and support their growth. Site location had a greater effect on the sex ratio of crabs such that marshes closer to the mouth of the bay contained a higher percentage of adult female crabs. In each annual growing season (April–July), the monthly increase in crab size and, in some months (June–July), the incidence of molting at the restored sites was greater than the reference sites, suggesting that the restored sites may provide areas for enhanced growth of crabs. These results suggest that blue crabs have responded positively to restoration of former salt hay farms in the mesohaline portion of Delaware Bay. 相似文献
11.
We examined relative abundance of juvenile weakfish,Cynoscion regalis, collected during 1986 and 1987 and tested for spatial differences in growth and survival within Delaware Bay. Juvenile weakfish recruit to all areas of Delaware Bay, and two cohorts were present during each year of the study. Although catch per unit effort (CPUE) varied among areas within the bay, there was a general trend of higher CPUE at lower salinities; abundance quickly declined near the end of September in all areas of the bay. Estimated growth rates from otolith increment analysis of juvenile weakfish ranged from 0.69 mm d−1 to 0.97 mm d−1. Spatial and temporal patterns in recent growth rate followed a general pattern: highest in the middle bay, lowest in the upper bay, and intermediate in the lower bay. Mortality rates were usually lowest in the low salinity region of the middle and upper bay during both years. There was no difference in mortality between cohorts in the middle bay, while in the upper bay the later-spawned fish had lower mortality and in the lower bay the early-spawned fish had lower mortality. Analysis of spatial and temporal patterns in growth and mortality suggests that there is a seasonal trade-off between habitat usage and resource availability for juvenile weakfish. The function of oligohaline and mesohaline waters as optimal nursery areas (in terms of growth and survival) changes due to the seasonally dynamic physicochemical characteristics in Delaware Bay. 相似文献
12.
As part of the Microbial Exchanges and Coupling in Coastal Atlantic Systems (MECCAS) Project, crab larvae were collected in the shelf waters off Chesapeake Bay in June and August 1985 and April 1986. We conducted hydrographic (temperature, salinity, nutrients) and biological (chlorophyll, copepods) mapping in conjunction with Eulerian and Lagrangian time studies of the vertical distribution of crab larvae in the Chesapeake Bay plume. These abundance estimates are used with current meter records and drifter trajectories to infer mechanisms of larval crab dispersion to the shelf waters and recruitment back into Chesapeake Bay. The highest numbers of crab larvae were usually associated with the Chesapeake Bay plume, suggesting that it was the dominant source of crab larvae to shelf waters. Patches of crab larvae also were found in the higher salinity shelf waters, and possibly were remnants of previous plume discharge events. The distribution of crab larvae in the shelf waters changed on 1–2 d time scales as a consequence of both variations in the discharge rate of the Chesapeake Bay plume and local wind-driven currents. Downwelling-favorable winds (NW) intensified the coastal jet and confined the plume and crab larvae along the coast. In April during a downwelling event (when northwesterly winds predominated), crab zoeae were transported southward along the coast at speeds that at times exceeded 168 km d−1. During June and August the upwelling-favorable winds (S, SW) opposed the anticyclonic turn of the plume and, via Ekman circulation, forced the plume and crab larvae to spread seaward. Plume velocities during these conditions generally were less than 48 km d−1. The recruitment of crab larvae to Chesapeake Bay is facilitated in late summer by the dominance of southerly winds, which can reverse the southward flow of shelf waters. Periodic downwelling-favorable winds can result in surface waters and crab larvae moving toward the entrance of Chesapeake Bay. Approximately 27% of the larval crabs spend at least part of the day in bottom waters, which have a residual drift toward the bay mouth. There appears to be a variety of physical transport mechanisms that can enhance the recruitment of crab larvae into Chesapeake Bay. 相似文献
13.
FABIEN DURAND FABRICE PAPA ATIQUR RAHMAN SUJIT KUMAR BALA 《Journal of Earth System Science》2011,120(5):859-872
This study investigates the impact of monthly Ganges–Brahmaputra river discharge variations on Bay of Bengal salinity and
temperature during the period 1992–1999. The Ganges–Brahmaputra river discharge is characterized by a well-defined seasonal
cycle with strong interannual variations. The highest/lowest yearly peak discharge occurs in summer 1998/summer 1992, with
1998 value amounting to twice that of 1992. This river discharge is then used to force an ocean general circulation model.
Our main result is that the impact of these rivers on the variability of Bay of Bengal sea surface salinity is strong in the
northern part, with excess run-off forcing fresh anomalies, and vice versa. Most of the years, the influence of the interannual variability of river discharge on the Bay salinity does not extend south
of ~10°N. This stands in contrast with the available observations and is probably linked to the relatively coarse resolution
of our model. However, the extreme discharge anomaly of 1998 is exported through the southern boundary of the Bay and penetrates
the south-eastern Arabian Sea a few months after the discharge peak. In response to the discharge anomalies, the model simulates
significant mixed-layer temperature anomalies in the northern Bay of Bengal. This has the potential to influence the climate
of the area. From our conclusions, it appears necessary to use a numerical model with higher resolution (both on the horizontal
and vertical) to quantitatively investigate the upper Bay of Bengal salinity structure. 相似文献
14.
Paul R. Jivoff Jennifer M. Smith Valerie L. Sodi Stacy M. VanMorter Kathryn M. Faugno Amy L. Werda Margaret J. Shaw 《Estuaries and Coasts》2017,40(1):235-250
Blue crabs (Callinectes sapidus) are an important species in coastal or lagoonal estuaries where adult population characteristics may differ as compared to drowned-river estuaries. Barnegat Bay, in southern New Jersey, is composed of two large embayments: one without and one with a salinity gradient. We tested the influence of physical characteristics on the abundance, sex ratio, and size of adult blue crabs and examined variation in measures of reproductive potential (e.g., sperm stores) in both sexes in Barnegat Bay from June to September, 2008–2009. Population structure was distinct between the embayments due to sex-specific responses to salinity: male abundance was negatively correlated with salinity whereas adult females were more abundant in high salinity because of proximity to Barnegat Inlet. This produced high sex ratios in low salinity areas and low sex ratios in high salinity areas. Summer was a growing season for adult males while in late summer-early fall, juvenile males recruited to the adult size class. The spawning season lasted from May to August and ovigerous females were concentrated near the inlets. Information on female sperm stores and ovarian development identified two cohorts of adult females: females that will spawn in the current summer and females that will not spawn until the following summer. Thus, not all adult females near the spawning grounds were members of the current spawning stock. This suggests that annual estimates of spawning stock size which overlook the proximity of females to spawning are overestimating the current spawning stock in Barnegat Bay and other estuaries. 相似文献
15.
The present study focused on detecting variations in trophic relationships among blue crab (Callinectes sapidus) consumers according to water quality along two estuaries in North Carolina. Stable isotope (δ15N and δ13C) analyses of particulate organic matter and bivalve(Rangia cuneata andCorbicula fluminea) food sources were examined in combination with an Isosource mixing model. Results suggest that blue crab δ13C values increased significantly with increasing salinity from upper to lower sites along the Neuse River estuary (NRE; R2
= 0.87, p < 0.01) and Alligator River estuary (R2 = 0.92, p < 0.01). There was a positive relationship between blue crab δ15N values and nitrate concentrations for the NRE (R2 = 0.48, p = 0.12). This study found that blue crab δ13C values increased with salinity from upper to lower regions along both estuaries. Results suggest that blue crab production
may have used alternative food sources that were isotopically (δ13C) depleted, especially in the upper NRE, and enriched sources in the mid to lower regions of both estuaries. Consumers sampled
from the upper NRE may be influenced by higher nitrogen input from urban land use and municipal wastewater. 相似文献
16.
Ronald M. Thom Amy B. Borde Steven Rumrill Dana L. Woodruff Gregory D. Williams John A. Southard Susan L. Sargeant 《Estuaries and Coasts》2003,26(4):1117-1129
Environmental factors that influence annual variability and spatial differences (within and between estuaries) in eelgrass meadows (Zostera marine L.) were examined within Willapa Bay, Washington, and Coos Bay, Oregon, over a period of 4 years (1998–2001). A suite of eelgrass metrics were recorded annually at field sites that spanned the estuarine gradient from the marine-dominated to mesohaline region of each estuary. Plant density (shoots m?2) of eelgrass was positively correlated with summer estuarine salinity and inversely correlated with water temperature gradients in the estuaries. Eelgrass density, biomass, and the incidence of flowering plants all increased substantially in Willapa Bay, and less so in Coos Bay, over the duration of the study. Warmer winters and cooler summers associated with the transition from El Niño to La Niña ocean conditions during the study period corresponded with this increase in eelgrass abundance and flowering. Large-scale changes in climate and nearshore ocean conditions may exert a strong regional influence on eelgrass abundance that can vary annually by as much as 700% in Willapa Bay. Lower levels of annual variability observed in Coos Bay may be due to the stronger and more direct influence of the nearshore Pacific Ocean on the Coos Bay study sites. The results suggest profound effects of climate variation on the abundance and flowering of eelgrass in Pacific Northwest coastal estuaries. 相似文献
17.
Joan A. Browder Victor R. Restrepo Jason K. Rice Michael B. Robblee Zoula Zein-Eldin 《Estuaries and Coasts》1999,22(2):484-499
Two modeling approaches were used to explore the basis for variation in recruitment of pink shrimp,Farfantepenaeus duorarum, to the Tortugas fishing grounds. Emphasis was on development and juvenile densities on the nursery grounds. An exploratory
simulation modeling exercise demonstrated large year-to-year variations in recruitment contributions to the Tortugas pink
shrimp fishery may occur on some nursery grounds, and production may differ considerably among nursery grounds within the
same year, simply on the basis of differences in temperature and salinity. We used a growth and survival model to simulate
cumulative harvests from a July-centered cohort of early-settlementstage postlarvae from two parts of Florida Bay (western
Florida Bay and northcentral Florida Bay), using historic temperature and salinity data from these areas. Very large year-to-year
differences in simulated cumulative harvests were found for recruits from Whipray Basin. Year-to-year differences in simulated
harvests of recruits from Johnson Key Basin were much smaller. In a complementary activity, generalized linear and additive
models and intermittent, historic density records were used to develop an uninterrupted multi-year time series of monthly
density estimates for juvenile pink shrimp in the Johnson Key Basin. The developed data series was based on relationships
of density with environmental variables. The strongest relationship was with sea-surface temperature. Three other environmental
variables (rainfall, water level at Everglades National Park Well P35, and mean wind speed) also contributed significantly
to explaining variation in juvenile densities. Results of the simulation model and two of the three statistical models yielded
similar interannual patterns for Johnson Key Basin. While it is not possible to say that one result validates the other, the
concordance of the annual patterns from the two models is supportive of both approaches. 相似文献
18.
T. Dale Bishop Harlan L. MillerIII Randal L. Walker Dorset H. Hurley Theron Menken Charles E. Tilburg 《Estuaries and Coasts》2010,33(3):688-698
The blue crab, Callinectes sapidus Rathbun, 1896, represents the second most important fishery for coastal Georgia; yet, little is known about environmental
forces that affect planktonic postlarval settlement in the region. Here, we describe a study to examine the physical mechanisms
responsible for blue crab settlement in the extensive salt marsh system of coastal Georgia. Bottom and surface samplers were
placed at three sites along a salinity gradient from a low-salinity site in the Altamaha River to a high-salinity area of
the Duplin River, Sapelo Island, GA, USA during 2005. Megalopae and juvenile monitoring occurred from July through December.
The majority of both megalopae (86.8%) and juvenile (89.3%) blue crabs were recovered in bottom samplers at the low-salinity
Altamaha River site during August and early September. Few megalopae were collected at the surface of the Altamaha River or
at the two higher-salinity sites in the Duplin and North Rivers. Downwelling winds were unable to explain all settlement events;
however, winds with an onshore component regularly preceded settlement events. The use of a multiple-regression model revealed
a lagged relationship (r = 0.5461, $ lag = 0–2 days $ lag = 0–2 days ) between wind events, temperature, salinity, maximum tidal height, and settlement. 相似文献
19.
A 16-yr (1985–2000) time series of calanoid copepod (Acartia tonsa andEurytemora affinis) abundance in the upper Chesapeake Bay was examined for links to winter weather variability. A synthesis of sea level pressure
data revealed ten dominant, winter weather patterns. Weather patterns differed in frequency of occurrence as well as associated
precipitation and temperature. The two dominant copepod species responded differently to winter weather variability.A. tonsa abundance showed little response to winter weather and did not vary in abundance during wet or dry springs.E affinis responded strongly to winter weather patterns that produced springs with high freshwater discharge and low salinities. During
wet springs,E. affinis abundance increased overall and its area of dominance extended further down estuary. The different response of the two species
is likely related to several factors including residence time, development time, salinity tolerance, food limitation, and
life history strategy. Important fish species that rely on zo oplankton as food resources were also related to winter weather
variability and spring zooplankton abundance.Morone saxatilis (striped bass) andAnchoa mitchilli (bay anchovy) juvenile indices were positively and negatively correlated toE. affinis abundance, respectively. *** DIRECT SUPPORT *** A02BY003 00004 相似文献
20.
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