• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.28 no.6
• /
• pp.708-719
• /
• 1995

This study is to estimate abundance of the Chesapeake Bay blue crab stock. Using 823 dredge tows which were conducted during the 1991 winter survey, blue crab abundance was estimated on the basis of newly developed methods which account for unequal dredge tow distances, size- and sex-specific heterogeneous overwintering spatial distributions, wintertime exploitation, the time period of quasi-hibernation, and dredge capture efficiency. The estimate of total abundance before correction by gear efficiency was 131.8 million crabs $(95\%\;C.I.\;=\;118.2\;million\;crabs\;to\;145.4\;million\;crabs),$ Dredge capture efficiency was estimated to be 0.474. Thus, the estimate of total abundance was calculated as 278.1 million crabs after correction by the efficiency factor.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.28 no.6
• /
• pp.720-727
• /
• 1995

A Monte Carlo computer simulation study was conducted to determine the most efficient sampling design for the blue crab dredge capture efficiency experiment performed in Chesapeake Bay, Maryland, U. S. A. The input values were the number of dredge tracks in each experimental area, the number of tows per experiment, the number of experiments, the mean density of crabs per unit area, the negative binomial coefficient, the gear capture efficiency, and the tow error. As a result of the study, a four-track experiment with twenty to twenty-eight tows was estimated to be the best in terms of precision and accuracy of the gear capture efficiency.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.58 no.2
• /
• pp.28-33
• /
• 2016

• Journal of the korean society of oceanography
• /
• v.32 no.3
• /
• pp.145-155
• /
• 1997

The distribution of microzooplankton and hydrographic variables were measured in the Virginia portion of Chesapeake Bay and its major rivers. Samples were collected at 14 locations at monthly interval from September 1993 through December 1995. Ciliates were numerically dominated (>90%) and copepod nauplii comprised highest proportion of the total microzooplankton biomass (>77%). Copepod nauplii and ciliates were the most abundant at oligohaline water and rotifers at freshwater. Total microzooplankton density and biomass were usually higher at oligohaline stations than fresh water and polyhaline stations. Despite high nutrient concentration and phytoplankton density at eutrophic water, micro- and mesozooplankton biomass were low. Mesozooplankton were relatively abundant at polyhaline stations. The comparison between annual mean biomass of ciliates (12.7 ${\mu$}gC/1) and that of autotrophic picoplankton (13.5 {$\mu$}gC/1) revealed that ciliates were a major consumer of picoplankton production. The secondary production by ciliates was 12.7 ${\mu}$gC/1/day, representing 5% of the annual mean primary production in Chesapeake Bay, Total microzooplankton comprised 84% of the total zooplankton carbon content, representing five times higher than mesozooplankton biomass.

• Animal cells and systems
• /
• v.2 no.2
• /
• pp.165-176
• /
• 1998

Seasonal changes in microzooplankton abundance were identified in the mesohaline Chesapeake Bay and several tributaries from July 1992 through December 1995. Ciliates numerically dominated, comprising over 90% of the total microzooplankton density and aloricate ciliates usually outnumbered loricate ciliates. Copepod nauplii accounted for the highest microzooplankton biomass (>75% in dry weight). Rotifers made small contributions to the total microzooplankton density and biomass (<5%). Time series analysis indicated a twelve month cycle in microzooplankton abundance, and mid-summer(August) peaks for copepod nauplii, and a spring through fall peaks (May-October) for ciliates. Rotifers showed two seasonal peaks: one in mid-summer(August) at the river stations and the other in mid-winter(February) at the mesohaline stations. Seasonal peaks of copepod nauplii and rotifers coincided with the mesozooplankton abundance peak. On the other hand, ciliate maximum usually occurred between the phytoplankton and mesozooplankton peaks. This pattern of microzooplankton seasonality suggests the intermediate trophic role of microzooplankton (especially ciliates) between the phytoplankton(especially picophytoplankton) and mesozooplankton in Chesapeake Bay and its tributaries.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.26 no.4
• /
• pp.369-379
• /
• 1993

Using a successive removal approach the mechanism of sampling capture efficiency of blue crabs by dredges was studied in Chesapeake Bay during winter 1992. For the twenty-six field experiments no significant statistical differences were detected in dredge efficiency using general linear model analysis by factors including bottom sediments, water depths, and sampling vessels. Dredge efficiency (i.e., catchability) was estimated by two methods, Leslie (Leslie and Davis, 1939) and a simple revised method. Mean catchability was estimated at 0.26 (SE=0.03), indicating that only $26\%$($95\%\;C. I.=20{\sim}32\%$) of crabs present in the path of the dredge of a given sampling area are caught with a single dredge tow. Dredge efficiency declined exponentially as crab density increased.

• Korean Journal of Remote Sensing
• /
• v.33 no.1
• /
• pp.15-24
• /
• 2017

Jellyfish (cnidarian) are conspicuous in many marine ecosystems when in bloom. Despite their importance for the ecosystem structure and function, very few sampling programs are dedicated to sample jellyfish because they are patchily distributed and easily clogged plankton net. Although satellite remote sensing is an excellent observing tool for many phenomena in the ocean, their uses for monitoring jellyfish are not possible due to the coarse spatial resolutions. Hence, we developed the low altitude remote sensing platform to detect jellyfish in high resolutions, which allow us to monitor not only horizontal, but also vertical migration of them. Using low altitude remote sensing platform,we measured the jellyfish from the pier at the Chesapeake Biological Laboratory in Chesapeake Bay. The patterns observed included discrete patches, in rows that were aligned with waves that propagated from deeper regions, and aggregation around physical objects. The corresponding areas of exposed jellyfish on the sea surface were $0.1{\times}10^4pixel^2$, $0.3{\times}10^4pixel^2$, and $2.75{\times}10^4pixel^2$, respectively. Thus, the research result suggested that the migration of the jellyfish was related to the physical forcing in the sea surface.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.30 no.6
• /
• pp.964-973
• /
• 1997

A tidal prism eutrophication model, an one-dimensional intertidal model, is developed to study water quality conditions at small coastal basins and tidal creeks. The model simulates the physical transport processes using the concept of tidal flushing. The concept is simple and straightforward, and thus is ideal for small coastal basins with complex geometry. The model, having twenty-four state variables in the water column, simulates salinity, temperature, dissolved oxygen, three algal groups, and the cycles of carbon, nitrogen, phosphorus and silica. The model is applied to the Lynnhaven Bay, a small coastal basin of Chesapeake Bay in U.S.A. The model is calibrated using the field data collected in 1994, and then is verified using the independently collected data in 1980. The model overall gives a good reproduction of the field data, partly owing to the data collected from the field surveys specifically designed for the model application. This paper presents the procedure, and the results of the model calibration and verification.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
• /
• 1995.10a
• /
• pp.108-109
• /
• 1995

Hypoxia has persisted during summer in the bottom water of the lower portion of the Rappahannock Estuary, a western shore tributary of Chesapeake Bay. A laterally integrated two-dimensional, real-time model, consisting of linked hydrodynamic and water quality models, was developed to study the contributing processes for hypoxia. The hydrodynamic model gives the information of physical transport processes, both advective and diffusive, to the water quality model, which simulates the spatial and temporal distributions of eight water quality state variables. (omitted)

• Ocean and Polar Research
• /
• v.26 no.4
• /
• pp.679-684
• /
• 2004

To determine if Antarctic krill employ body shrinkage as one of its overwintering mechanisms in the field, Euphauia superba and Euphausia crystallorophias were collected during fall and winter in and around Marguerite Bay through US Southern Ocean GLOBEC field programs during fall and winter 2001 and 2002. The relationships between the body length and weight of both krill species were exponentially correlated with no significant differences between the two species (p>0.05). The ratio between eye diameter and body length of individual krill was examined in an expectation that it could be used as an indicator of the body shrinkage as previously suggested by Shin and Nicol (2002). These ratios were significantly different between the two krill species. Especially, E . crystallorophias had bigger eyes than E. superba. In both krill species, eye diameters were highly correlated with body lengths (regression coefficients ${\geq}0.70$). For E. crystallorophias, no significant differences of the ratio of eye diameter/body length were detected between fall and winter. Even though the ratios for E. superba were seasonally varied, it was not clear whether body shrinkage was an actual and critical overwintering mechanism for the krill population found in this study area. These results suggest that some individuals of E. superba might experience the body shrinkage during a part of their liff, but this morphological index alone (eye diameter/body length) may be insufficient to unambiguously separate the shrunk krill from the non-shrunk ones in the field-collected animals.