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1.
Rangia cuneata larvae were given the opportunity to settle on substrate types that differed in grain size, organic content, and bacterial abundance. Larvae settled in very fine sand (63–125 μm) and fine and medium sand (125–500 μm) more than in silt and clay (<63 μm) or on a hard substratum (empty polystyrene petri dishes). Proportionally more larvae settled onto untreated sediment from the adult habitat than onto the same sediment autoclaved, or treated with either H2O2 to remove organic material, or treated with antibiotics to reduce bacterial abundance. However, it appears that competent larvae do not delay settlement, even in the absence of “attractive” substrates. 相似文献
2.
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
3.
Increases in the antennular flicking rate indicated that blue crabs,Callinectes sapidus, detected the petroleum hydrocarbon naphthalene. A low incidence of aggressive displays but no food searching or gathering followed naphthalene detection. The results suggest that the chemosensory abilities of decapod crustaceans cover a broader range of substances than previously supposed. 相似文献
4.
Robert C. Hale 《Estuaries and Coasts》1988,11(4):255-263
The blue crab,Callinectes sapidus, is an abundant and widely distributed species in the Chesapeake Bay. It also supports a valuable fishery. Minimal information concerning concentrations of toxic organic compounds in crustaceans of the southern Chesapeake Bay is currently available. As a consequence, a study to determine the tissue burdens and behavior of lipophilic polycylic aromatic compounds (PACs) in these organisms was undertaken. Highest concentrations of PACs were detected in hepatopancreas, followed by ovarian and muscle tissues. Extractable lipid levels in the tissues were positively correlated with organic xenobiotic concentrations. The major contaminants detected in blue crabs sampled from the southern bay were alkylated PACs, as opposed to unsubstituted polynuclear aromatic hydrocarbons which have been reported to predominate in molluscs and sediments of the bay. This dichotomy may be due to differences in contaminant bioavailability or in the relative abilities of the organisms to eliminate xenobiotics. Crabs from both heavily industrialized and relatively undeveloped areas, showed evidence of exposure. These data suggest that localized areas of contamination and episodic contaminant releases may result in xenobiotic body burdens in mobile/migratory species. Crabs acutely exposed to radiolabeled benzo(a)pyrene in the laboratory were capable of rapid bioaccumulation. After transfer to clean water, the organisms efficiently eliminated this material, although at a rate slower than that observed for accumulation. Evidence that ecdysis in crustaceans may affect the disposition of PACs was also witnessed in these experiments. Differences in tissue concentrations of benzo(a)pyrene derived material were observed between crabs of various sex, maturity, and molt stages. 相似文献
5.
Morris H. Roberts 《Estuaries and Coasts》1981,4(4):313-320
Male, ovigerous female and nonovigerous female blue crabs were collected from seven stations in the lower Chesapeake Bay and lower James River, Virginia. The Kepone concentration in muscle, gonad and hepatopancreas was determined by GC analysis. All crabs from the lower Bay contained little Kepone, while many of those from the lower James River were contaminated. Male crabs contained more Kepone in the backfin muscle than females. Female crabs concentrated Kepone into the gonad, and, to a lesser extent, the hepatopancreas whereas the males did not. Ovigerous female crabs with spent ovaries, had less Kepone in the ovary than the corresponding egg masses. Further, ovigerous females, especially those with spent ovaries, had more Kepone in backfin muscle than nonovigerous females. It is concluded that the differences in Kepone partitioning among tissues of male and female crabs may explain the previously reported observation that males contain more Kepone in the backfin muscle than do females. 相似文献
6.
George R. Abbe 《Estuaries and Coasts》2002,25(1):105-114
Maryland commercial landings of the blue crab (Callinectes sapidus) and catch per unit effort (CPUE) have remained fairly stable over the past 33 yr despite occasional large deviations from the long-term average. During this time, however, significant declines in the percent of legal male crabs and the mean size of legal males caught in fishery-independent surveys near Calvert Cliffs, Maryland have become apparent. Sublegal females and two of the three legal female classes (152–177 and >178 mm CW) showed no significant trends over this 33-yr period when examined by linear regression. Males showed significant trends for all size classes. Sublegal males increased from 24% of the male population during the first 5 yr of the study (1968–1972) to 71% during 1996–2000. All classes of legal males, however, exhibited downward trends. Males 127–151 mm CW decreased from 45% of the male population in the earliest period to 22% during the last 5 yr. Males 152–177 mm decreased from 27% during 1968–1972 to only 6% during 1996–2000, and males > 178 mm declined from 4% in the earliest period to 0.5% in the recent period. These size decreases for the most valuable portion of the blue crab population are further evidence of over-exploitation. The declining trends in male size indicate that growth overfishing is occurring as intense fishing pressure removes so many male crabs from the population as they reach legal size that few remain to molt to larger size. A 3-yr data set from the Patuxent River, where commercial use of crab pots is restricted and fishing pressure is lower, suggests that legal male crabs are able to attain larger size compared to an area where the pot fishery is intense. A recommendation could be made for reducing effort where the pot fishery is intense by means of time, gear, catch limits, and/or by increasing the minimum size of legal crabs to allow larger crabs to enter the fishery. 相似文献
7.
Genetic variability of the blue crab,Callinectes sapidus, was estimated for populations in Chesapeake and Chincoteague Bays. Genetic similarity between these populations was attributed to larval intermixing in the mid-Atlantic Bight. 相似文献
8.
Diffubenzuron (Dimilin) is used as an insecticide for control of the gypsy moth. Because it is a chitin synthetase inhibitor, it can be a potential threat to other arthropods, including crustaceans. We used a static renewal testing paradigm to determine the LC50 of Dimilin WP-25 to juvenile blue crabs (carapace width: 25–60 mm). Both molt stage of dose frequency effect toxicity. When we exposed the crabs at random molt stages, LC50=3.5 mg l?1. When crabs were exposed on the day of molt, LC50=300 μg l?1. If initial exposure occurred on the day of molt and the crabs were subsequently exposed to repeated doses, LC50=18.5 μg l?1. Effects were age and molt-stage sensitive. We include a review of the data available on Dimilin effects in the marine and estuarine environments. 相似文献
9.
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. 相似文献
10.
Using behavioral criteria developed in previous studies, the threshold concentration at which the blue crab,Callinectes sapidus, detected the petroleum hydrocarbon naphthalene was found to be 10?7 mg/l. Oriented locomotor activity and defensive displaying began at 2 mg/l of naphthalene. No feeding behavior was observed up to and including the maximum naphthalene concentration of 5 mg/l. Below 2 mg/l the blue crab apparently had no active behavioral response to naphthalene exposure other than detection. 相似文献
11.
Clifford H. Ryer 《Estuaries and Coasts》1987,10(2):136-140
A 24-h study of blue crab feeding periodicity was conducted concurrently in a tidal marsh creek and adjacent seagrass meadow in the lower Chesapeake Bay. Crabs from the grassbed tended to have fuller guts than crabs from the marsh creek. In the grassbed, a weak trend toward nocturnal feeding was observed, with an apparent peak at dusk. During the day, crabs were not easily observed and were assumed to be feeding beneath the eelgrass canopy; at night crabs fed in the canopy. In the marsh creek, feeding was related to the tidal cycle, with guts being fullest at high tide and decreasing to lows just prior to the next high tide. This study suggests the potential importance of habitat on blue crab feeding patterns. 相似文献
12.
A two-year trawl study of Laguna Joyuda, Puerto Rico, a small, polyhaline lagoon with restricted oceanic exchange, yielded 803 crabs belonging to sixCallinectes species.Callinectes danae was the most abundant (35.7%), followed byC. sapidus (21%),C. ornatus (12.6%),C. bocourti (12.1%),C. exasperatus (1.2%), andC. larvatus (0.4%). Abundances of different species differed more spatially than temporally despite very homogeneous salinities.Callinectes bocourti andC. sapidus were most abundant furthest from the lagoon’s inlet, whileC. danae andC. ornatus were most abundant near the inlet and in the center of lagoon. Juveniles were least abundant in the center of the lagoon. Size frequencies of most species showed common trends with high percentages of small crabs furthest from the inlet, and high percentages of larger crabs near the inlet and central parts of the lagoon. Distributional patterns appear to be a result of complex interactions of habitat preferences and intra- and interspecific interactions among the crabs. 相似文献
13.
Habitat selection capabilities of the recruiting larval stages of marine invertebrates are limited, in part, by their ability to maneuver in flowing water. Distributional and experimental evidence suggest that blue crab (Callinectes sapidus) megalopae may preferentially settle into vegetated habitats. However, the behavior and swimming capabilities of megalopae in flowing water have not previously been investigated. Laboratory experiments were conducted in a small, recirculating seawater flume to determine the swimming response of megalopae to varying flow velocities. Nighttime trials were conducted at six flow velocities: 0, 1.9, 3.6, 4.8, 6.3, and 9.3 cm s?1. Behavior and swimming velocities of field-collected C. sapidus megalopae were video recorded. Megalopae exhibited negative phototaxis and were found in the water column at all flows in the dark. The maximum sustained swimming speed observed was 12.6 cm s?1 and the mean swimming speed in still water was 5.0 cm s?1, with short bursts in excess of 20 cm s?1. Megalopae frequently oriented into the current and were capable of swimming upstream against the current at flow speeds <4.8 cm s?1; at greater velocities they were not able to do so. The results suggest that at low to moderate current velocities C. sapidus megalopae have the ability to actively move in search of settlement sites and to maintain their positions in desirable sites rather than relying strictly on passive movements by currents. 相似文献
14.
Factors affecting Kepone uptake and lipid content of the clam,Rangia cuneata, were tested over a 12 month study. Clams obtained from the Rappahannock and James Rivers were held in submersible liver boxes at two sites in the James River estuary and were sampled monthly from September 1978 through August 1979. Clams held in the freshwater zone near the source of Kepone contamination (Hopewell, Virginia) generally had higher Kepone and lipid content than those held downstream in the oligohaline zone. Significant differences in Kepone content between test sites and months are largely, but not entirely, a function of ambient water temperature, dissolved oxygen, amount of lipid in the clam, turbidity, Kepone content of the water column and duration of exposure. Lipid content of clams varied significantly between test sites, river of origin and months and is significantly related to salinity, ambient water temperature, pH and duration of exposure. Kepone content was more closely correlated with total lipid stores of clams than any other real variable. This association may be due to lipid reserves acting as a storage site for Kepone, but may also be interpreted as the result of selection against clams lacking lipid stores that might act as reservoirs for Kepone thus protecting more delicate tissues. 相似文献
15.
A 16-month study of estuarine habitats in poly-, meso-, and oligohaline salinity regimes near Charleston Harbor assessed the distribution and abundance of megalopae and early crab stages of the blue crab,Callinectes sapidus. Blue crab were sampled with a plankton net and a cylindrical drop sampler. Blue crab were most abundant in plankton collections at night, accounting for 68% of the megalopae and over 88% of the juveniles collected in day and night tows combined. At night, densities of megalopae were greatest in surface samples, whereas densities in daylight collections were greater on the bottom. Juvenile densities were greatest on the bottom in both day and night collections, although catch rates at night were more variable than those of the megalopae. This suggests that megalopae, and possibly juvenile stages, experience a diel vertical migration. Results indicate that ingress to estuarine nursery areas occurs at the megalopal stage. Megalopal densities were highest at the polyhaline site, while juvenile blue crab were most abundant in the oligohaline area. Habitat utilization by juvenile blue crab was estimated using a cylindrical drop sampler and Venturi suction pump on three bottom types in the intertidal zone. Densities were greatest over the sandy-mud substrate, although catch rates were much lower than those reported for other geographical areas. These results suggest that juvenile blue crab do not occur in abundance on the marsh surface but remain on the creek bottom, possibly because creek physiography and large tidal amplitudes may restrict accessibility to the marsh surface. 相似文献
16.
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
17.
Small blue crabs (Callinectes sapidus Rathbun, 43–70 mm carapace width) can influence the size-distribution of the gastropod,Bittium varium, strongly reducing the contribution of snails >3 mm shell length in field enclosures. We test the hypothesis that these size-dependent effects are due to size-selective predation rather than size-dependent emigration from the field enclosures. In laboratory feeding trials, blue crabs showed negative selectivity for snails <2.5 mm and positive selectivity for snails >3.3 mm. When feeding, blue crabs crushBittium shells, but the opercula are deposited undamaged in the sediment. Sediment from a field enclosure experiment contained 6.5× moreBittium opercula from enclosures with blue crabs than from enclosures without blue crabs. We reconstructed the size distribution ofBittium killed by blue crabs from the opercula recovered from sediment. This distribution qualitatively matched those “missing” from the size frequency distribution of surviving snails. Estimates of selectivity from laboratory feeding trials predicted the pattern of size-selection fromBittium killed in the enclosures. We also estimated Strauss's linear index of selectivity and Chesson's α based on the size distribution of snails available during the field enclosure experiment. These indices predicted both the pattern of selectivity and the size distribution ofBittium killed in enclosures with blue crabs. We conclude that size-selective predation by blue crabs can explain the observed shifts inBittium size distributions. 相似文献
18.
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
19.
Kirt E. Moody 《Estuaries and Coasts》2003,26(3):759-764
Blue crabsCallinectes sapidus in lower Chesapeake Bay are subject to high rates of predation during the late summer of their first year of growth as they
migrate out of vegetated nursery habitats. Predators, potentially contributing to this pattern, were identified in video-recorded
field observations of tethered juvenile crabs (20–25 mm carapace width). Predators were also tested in large laboratory tanks
containing similarly-sized untethered crabs as prey. Seven different predators attacked tethered crabs in the field. Only
two predators, larger blue crabs and northern puffers,Sphoeroides maculatus, consistently succeeded in preying on crabs in both field and laboratory settings. These results confirm the importance of
cannibalism on juvenile blue crabs and identify puffers as a potentially overlooked source of predation pressure. 相似文献
20.
B. L. Swan 《Estuaries and Coasts》2005,28(1):28-40
Adult horseshoe crabs,Limulus polyphemus, were tagged in the Middle Atlantic Bight area, from New York to Virginia on the continental shelf and within bays, to determine
their migratory patterns and longevity. Of 30,432 horreshoe crabs that were tagged during the years 1986–2002, 1,122 were
recovered alive, and 1,027 were dead. Many of the live recoveries were observed within 30 d (54.4%) and after years (37.53%)
with one tagged animal surviving up to 10 yr. In 9 locations from Great Kills Harbor, New York, to Chesapeake Bay, Maryland,
the horseshoe crabs return to their release beach within days during the spawning season. Of the 762 (100%) recoveries from
crabs released along the Delaware Bay shoreline, 75.07% traveled 0–20 km, 21.0% traveled 20–50 km, 2.36% traveled 50–100 km,
and 1.57% traveled over 100 km. Within Delaware Bay, 327 tagged animals (43.6%) had moved away from the release points to
other locations, and 59 of these had moved out of the bay onto the continental shelf along the Mid-Atlantic Bight coastline.
Horseshoe crabs migrate into Delaware Bay from waters off Ocean City, Maryland, and adjacent coastal bays. In addition to
defining the range of the Delaware Bay spawning populations, 2 neighboring populations were identified by the tagging program.
In one, animals tagged in southern New York mingled with those in the Sandy, Hook, New Jersey area, comprising a population
that ranged from Raritan Bay across New York Harbor to Jamaica Bay. The second confirmed that a discrete population existed
in northern Chesapeake Bay in the general vicinity of the Annapolis Bay Bridge. 相似文献