Kings Bay Research Articles

How do ambient conditions and management actions affect manatee movements and habitat use?

AbstractKings Bay in northwest Florida, USA, is an important winter home of the largest aggregation of Florida manatee (Trichechus manatus latirostris), and the only location in the United States where visitors legally swim and interact with manatees. In addition to ambient conditions, visitors to the area and management actions have the potential to influence manatee behaviors. We tracked 32 manatees with satellite‐linked global position system (GPS) telemetry tags in Kings Bay from 2006 to 2018. Also, personnel at Crystal River National Wildlife Refuge collected manatee counts at Three Sisters Springs from 2014 to 2017. Our objectives were to document the use of springs and other habitat components in Kings Bay relative to ambient water temperature, time of day, tide stage, and management actions within Three Sisters Springs and other manatee sanctuaries in the bay. Manatees that we tagged in Kings Bay spent a median 87% of the winter within the local study area, compared to 47% for animals that we tagged in the Florida Panhandle. Manatees showed preferences for King and Magnolia springs basins at low tide, indicating that they function as tidal refuges, when other locations may be less accessible; we also recorded within spring basin movements. Magnolia Spring Basin showed a significant diel pattern overall, and within basins, King Spring, Tarpon Hole, and Three Sisters Springs were used more during the night than during the day. All areas outside Kings Bay were used more at warmer ambient gulf water temperatures, while all of the springs basins were used more when gulf temperature was colder, especially Three Sisters Springs Basin. Management of Three Sisters Springs had an influence on manatee use during times of cold ambient gulf water temperatures; manatees used the springs more when the spring was closed to visitors, versus when the springs were completely open or when the spring lobes alone were closed. Manatee decisions were consistent with avoiding human interactions.

Recent Development and Field Test of CO-OPS' Real-Time, Shallow Water CURrents BuoY (CURBY)

Abstract The National Oceanic and Atmospheric Administration (NOAA) National Ocean Service Center for Operational Oceanographic Products and Services (CO-OPS) manages the National Current Observation Program (NCOP) and Physical Oceanographic Real-Time Systems (PORTS®). These programs provide tide and current predictions, as well as real-time current and meteorological information. Outdated current predictions, navigational support requirements, and incident response scenarios (e.g., oil spills, vessel accidents) have highlighted CO-OPS' need for a rapidly deployable system that provides near-surface current and meteorological observations. To address this, CO-OPS designed, developed, and tested a real-time system based on a surface buoy platform, hereinafter referred as CURrents BuoY (CURBY). This paper provides an overview of the system design, field test results, operational applications, and future plans.In 2018, CO-OPS completed the build, integration, and testing of the first prototype CURBY. A successful field test was completed during 2018 in the Chesapeake Bay, and the first operational deployment followed shortly on the Delaware River in 2019. Resulting measurements were used to improve tidal current predictions and to plan for a 2021 regional survey. Initial success with tidal current survey operations led to design enhancement and wider use. During 2020‐2021, CO-OPS partnered with the NOAA Office of Response and Restoration to build two new CURBYs to support emergency response applications in the Gulf of Mexico region. During 2022, two CURBY systems were deployed in the Columbia River, Oregon, to support additional NCOP operations. Future plans include establishing a long-term CURBY system for Kings Bay, Georgia, PORTS®.

Norwegian and Russian Mining and Mining Communities in Monica Kristensen’s Oeuvre

Monica Kristensen is a Norwegian glaciologist, meteorologist, polar explorer and author of fiction (crime novels) and nonfiction (about expeditions, Svalbard, The Kings Bay Affair, and Roald Amundsen). In her altogether five crime novels, all of which take place in Svalbard, the plot is inextricably bound to place, i.e. to the Arctic. In two of her five crime novels, Kullunge and Den døde i Barentsburg, crucial parts of the action take place in the coal mines of Longyearbyen and Barentsburg. In her documentary book about the Kings Bay Affair she investigates the terrible mining accident in 1962 at Kings Bay mines that killed 21 miners. In this article I examine the literary construction of these specific places – the Arctic and the coal mines, or, the coal mines in the Arctic – in these three books, as well as the related political, ethical and existential questions of settlement and living conditions.

High prevalence of Ichthyophonus sp. infections in Northeast Atlantic mackerel (Scomber scombrus).

High prevalence of Ichthyophonus sp. infections in Northeast Atlantic mackerel (Scomber scombrus).

The Shipwreck of the Airship “Dirigibile Italia” in the 1928 Polar Venture: A Retrospective Analysis of the Ionospheric and Geomagnetic Conditions

AbstractOn 25 May 1928 the airship “Dirigibile Italia” during its return trip to the base in NyAlesund, after overflying the North Pole, shipwrecked on the ice‐pack in a region at about 400 km northeast of Svalbard Islands. Survivors, by using a portable high frequency (HF) radio transmitter, tried unsuccessfully to send SOS messages and to establish a radio link with the ship “Città di Milano” of the Italian Navy, closely anchored at King's Bay. Only after 9 days of repeated radio‐distress transmissions, a Russian radio amateur close to the town of Arkhangelsk about 1,900 km away was able to receive the messages launched by the survivors and raise the alarm. This paper aims at giving a retrospective analysis of the ionospheric and geomagnetic conditions of that epoch in order to explain the HF radio communications problems encountered by the survivors. The International Reference Ionosphere model has been applied, and early geomagnetic measurements have been evaluated, to come up with theories explaining the events. We assert the HF transmission difficulties were associated with the “radio silent” or “dead zones” associated with F‐region propagation. These may have been exacerbated by solar and geomagnetically disturbed conditions of the days immediately following the airship wreck.

Hunting the Northern Lights

AbstractWhen a tragic accident occurred in November 1962 in the coalmine of Kings Bay Company in Ny‐Ålesund, Svalbard, (78°55´N, 11°56´E) it led to the fall of the labour government that had been ruling Norway since the Second World War. A year later the mine was closed, the infrastructure left unattended, and the community of Ny‐Ålesund evacuated. The Norwegian government was then facing a challenge as it had to establish a new activity in the village in order to keep the sovereignty over the territory. This was in the middle of the Cold War. The Russian population on Svalbard was about twice as large as the Norwegian, while the production of the Russian mines was approximately half the output of the Norwegians. An empty village with well‐developed infrastructure on Svalbard was therefore an enticement for the Soviet Union.

Shewanella polaris sp. nov., a psychrotolerant bacterium isolated from Arctic brown algae.

A Gram-stain-negative, facultatively anaerobic, flagellated and rod-shaped bacterium, designated strain SM1901T, was isolated from a brown algal sample collected from Kings Bay, Svalbard, Arctic. Strain SM1901T grew at -4‒30 °C and with 0-7.0 % (w/v) NaCl. It reduced nitrate to nitrite and hydrolysed DNA and Tween 80. Results of phylogenetic analyses based on 16S rRNA gene sequences indicated that strain SM1901T was affiliated with the genus Shewanella, showing the highest sequence similarity to the type strain of Shewanella litoralis (97.5%), followed by those of Shewanella vesiculosa, Shewanella livingstonensis and Shewanella saliphila (97.3 % for all three). The major cellular fatty acids were summed feature 3 (C16 : 1 ω7с and/or C16 : 1 ω6с), C16 : 0, C18 : 0, iso-C15 : 0 and C17 : 1 ω8с and the major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The respiratory quinones were ubiquinones Q-7, Q-8, menaquinones MK-7(H) and MK-8. The genome of strain SM1901T was 4648537 nucleotides long and encoded a variety of cold adaptation related genes, providing clues for better understanding the ecological adaptation mechanisms of polar bacteria. The genomic DNA G+C content of strain SM1901T was 40.5 mol%. Based on the polyphasic evidence presented in this paper, strain SM1901T was considered to represent a novel species, constituting a novel psychrotolerant lineage out of the known SF clade encompassed by polar Shewanella species, within the genus Shewanella, for which the name Shewanella polaris sp. nov. is proposed. The type strain is SM1901T (=KCTC 72047T=MCCC 1K03585T).

A Means to an End:: Impacting Patient Satisfaction Through Nursing Strategic Initiatives

•Improving nursing job satisfaction improves the perceived patient care experience. •Utilizing professional practice models helps to improve nursing satisfaction. •Health care leaders must advocate for nurses in order to improve patient care. Patient satisfaction is a vital metric that is reflective of the quality of care that health care organizations provide. Research studies have demonstrated a strong association between nursing and patient satisfaction scores, leading health care organizations to prioritize initiatives that positively impact nursing satisfaction. Challenges in today’s evolving health care—leadership changes, patient–nurse staffing ratios, burnout, and insufficient professional development opportunities—may negatively impact nursing satisfaction. This article calls on health care leaders to identify strategic solutions aimed at enhancing the patient experience through improving nursing satisfaction. Patient satisfaction is a vital metric that is reflective of the quality of care that health care organizations provide. Research studies have demonstrated a strong association between nursing and patient satisfaction scores, leading health care organizations to prioritize initiatives that positively impact nursing satisfaction. Challenges in today’s evolving health care—leadership changes, patient–nurse staffing ratios, burnout, and insufficient professional development opportunities—may negatively impact nursing satisfaction. This article calls on health care leaders to identify strategic solutions aimed at enhancing the patient experience through improving nursing satisfaction. Sarah Margrave, MSN, is the Occupational Health Clinic Nurse Manager at Naval Branch Health Clinic Kings Bay, GA. She can be reached at [email protected] . Dagoberto Salinas, MSN, is a Hospital Corpsman Basic Instructor at Navy Medicine Training Support Center, Joint Base San Antonio, Fort Sam Houston, Texas.

Contribution of calving to frontal ablation quantified from seismic and hydroacoustic observations calibrated with lidar volume measurements

Abstract. Frontal ablation contributes significantly to the mass balance of tidewater glaciers in Svalbard and can be recovered with high temporal resolution using continuous seismic records. Determination of the relative contribution of dynamic ice loss through calving to frontal ablation requires precise estimates of calving volumes at the same temporal resolution. We combine seismic and hydroacoustic observations close to the calving front of Kronebreen, a marine-terminating glacier in Svalbard, with repeat lidar scanning of the glacier front. Simultaneous time-lapse photography is used to assign volumes measured from lidar scans to seismically detected calving events. Empirical models derived from signal properties such as integrated amplitude are able to replicate volumes of individual calving events and cumulative subaerial ice loss over different lidar scan intervals from seismic and hydroacoustic data alone. This enables quantification of the contribution of calving to frontal ablation, which we estimate for Kronebreen to be about 18 %–30 %, slightly below the subaerially exposed area of the glacier front. We further develop a model calibrated for the permanent seismic Kings Bay station (KBS) at about 15 km distance from the glacier front, where 15 %–60 % of calving events can be detected under variable noise conditions due to reduced signal amplitudes at distance. Between 2007 and 2017, we find a 5 %–30 % contribution of calving ice blocks to frontal ablation, which emphasizes the importance of underwater melting (roughly 4–9 m d−1). This study shows the feasibility to seismically monitor not only frontal ablation rates but also the dynamic ice loss contribution continuously and at high temporal resolution.

COASTAL HABITAT CHANGE AND MARINE MEGAFAUNA BEHAVIOR: FLORIDA MANATEES ENCOUNTERING REDUCED FOOD PROVISIONS IN A PROMINENT WINTER REFUGE.

A decline in submerged aquatic vegetation (SAV) within Florida's spring-fed, thermal refuges raises questions about how these systems support winter foraging of Florida manatees (Trichechus manatus latirostris). We analyzed telemetry data for 12 manatees over seven years to assess their use of Kings Bay, a winter refuge with diminished SAV. After accounting for the effect of water temperature, we hypothesized that the number of trips out of Kings Bay would increase and the time wintering manatees spent in Kings Bay would decrease. Trips out of and into Kings Bay also were compared to assess potential influences on exiting or entering. There were no detectable differences in the number of trips out of the bay or overall time manatees spent in Kings Bay across winters. The percentage of time water temperatures were below 20°C was the single best predictor of increased time spent in Kings Bay. Trips out of Kings Bay were more likely to occur after 12:00 h and during a high but ebbing tide, compared to trips into the bay. Nine manatees tracked for longer than 75 days in winter spent 7-57% of their time in the Gulf of Mexico, and three of these manatees spent 7-65% of the winter >80 km from the mouth of Kings Bay. Results suggest the low amount of SAV in Kings Bay does not obviate its use by manatees, though there are likely tradeoffs for manatees regularly foraging elsewhere. Accounting for movements of Florida manatees through a network of habitats may improve management strategies and facilitate desirable conservation outcomes.

Observations and source investigations of the boundary layer bromine monoxide (BrO) in the Ny-Ålesund Arctic

Abstract. During polar spring, the presence of reactive bromine in the polar boundary layer is considered to be the main cause of ozone depletion and mercury deposition. However, many uncertainties still remain regarding understanding the mechanisms of the chemical process and source of the bromine. As Arctic sea ice has recently been dramatically reduced, it is critical to investigate the mechanisms using more accurate measurements with higher temporal and spatial resolution. In this study, a typical process of enhanced bromine and depleted ozone in the Ny-Ålesund boundary layer in late April 2015 was observed by applying ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) technique. The results showed that there were bromine monoxide (BrO) slant columns as high as 5.6 × 1014 molec cm−2 above the Kings Bay area on 26 April. Meanwhile, the boundary layer ozone and gaseous elemental mercury (GEM) were synchronously reduced by 85 and 90 %, respectively. Based on the meteorology, sea ice distribution and air mass history, the sea ice in the Kings Bay area, which emerged for only a very short period of time when the enhanced BrO was observed, was considered to be the major source of this bromine enhancement event. The oxidized GEM may be directly deposited onto snow/ice and thereby influence the polar ecosystem.

Hymenobacter rutilus sp. nov., isolated from marine sediment in the Arctic.

Strain K2-33028T, which appeared as a brick-red colony on an R2A plate, was isolated from a marine sediment sample from Kings Bay, Svalbard Archipelago, Norway. Phylogenetic analysis based on 16S rRNA gene sequences indicated that K2-33028T represented a member of the genus Hymenobacter. Cells were Gram-reaction-negative, non-spore-forming, aerobic, rod-shaped and without motility. Growth occurred at 4-37 °C (optimum 28 °C) and at pH 6.0-8.0 (optimum pH 7.0). Cells contained menaquinone-7 as the main respiratory quinone and iso-C15 : 0, summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c), C16 : 1ω5c, summed feature 4 (comprising anteiso-C17 : 1B and/or iso-C17 : 1I) and anteiso-C15 : 0 as the major cellular fatty acids. Phosphatidylethanolamine was predominant in the polar lipid profile. The DNA G+C content was 64.3 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain K2-33028T is considered to represent a novel species of the genus Hymenobacter, for which the name Hymenobacterrutilussp. nov. is proposed. The type strain is K2-33028T (=CCTCC AB 2016091T=KCTC 52447T).

Nitrogen Source Inventory and Loading Tool: An integrated approach toward restoration of water-quality impaired karst springs

Nitrogen (N) from anthropogenic sources has contaminated groundwater used as drinking water in addition to impairing water quality and ecosystem health of karst springs. The Nitrogen Source Inventory and Loading Tool (NSILT) was developed as an ArcGIS and spreadsheet-based approach that provides spatial estimates of current nitrogen (N) inputs to the land surface and loads to groundwater from nonpoint and point sources within the groundwater contributing area. The NSILT involves a three-step approach where local and regional land use practices and N sources are evaluated to: (1) estimate N input to the land surface, (2) quantify subsurface environmental attenuation, and (3) assess regional recharge to the aquifer. NSILT was used to assess nitrogen loading to groundwater in two karst spring areas in west-central Florida: Rainbow Springs (RS) and Kings Bay (KB). The karstic Upper Floridan aquifer (UFA) is the source of water discharging to the springs in both areas. In the KB study area (predominantly urban land use), septic systems and urban fertilizers contribute 48% and 22%, respectively, of the estimated total annual N load to groundwater 294,400 kg-N/yr. In contrast for the RS study area (predominantly agricultural land use), livestock operations and crop fertilizers contribute 50% and 13%, respectively, of the estimated N load to groundwater. Using overall groundwater N loading rates for the KB and RS study areas, 4.4 and 3.3 kg N/ha, respectively, and spatial recharge rates, the calculated groundwater nitrate-N concentration (2.1 mg/L) agreed closely with the median nitrate-N concentration (1.7 mg/L) from groundwater samples in agricultural land use areas in the RS study area for the period 2010–2014. NSILT results provide critical information for prioritizing and designing restoration efforts for water-quality impaired springs and spring runs affected by multiple sources of nitrogen loading to groundwater. The calculated groundwater N concentration for the KB study area (1.45 mg/L) was approximately three times higher than the median N concentration (0.45 mg/L) for wells located in urban land use areas.

Seasonal warm-water refuge and sanctuary usage by the Florida manatee (Trichechus manatus latirostris) in Kings Bay, Citrus County, Florida

The largest Florida manatee (Trichechus manatus latirostris) aggregation at a natural warm-water site occurs in Kings Bay, Crystal River, FL. In accordance with the Manatee Recovery Plan, manatee protection areas within Kings Bay have been created by the United States Fish and Wildlife Service (USFWS) and the State of Florida including a year-round refuge designation and seven Federal manatee sanctuaries during the winter manatee season (15 November–31 March). Over the last 30 years, an increase in manatee counts has been observed in Kings Bay which has prompted the need to review existing manatee protection measures. Aerial survey data collected between 1983 and 2012 were used to examine the seasonal change in manatee distribution within Kings Bay to assess the effectiveness of current sanctuary sizes and locations. Regression analysis suggested a significant change in manatee abundance among the winter seasons (p < 0.05). The average winter manatee counts increased by 4.81 animals per year over the 30-year period. Spatially explicit maps using geographic information system (GIS) analysis revealed a strong correlation between high manatee density and artesian springs in Kings Bay during the winter seasons. Highest abundances were identified at three locations: King Spring, Three Sisters Springs, and Magnolia Springs, which coincide with preexisting sanctuary designations. Additional coverage is advocated to support the overflow of manatees outside of sanctuary boundaries. As density patterns were not uniform across summer periods, a consideration of additional boat speed regulations is recommended.

Making friends with strangers: The Kings Bay (FL) adaptive management experiment

Making friends with strangers: The Kings Bay (FL) adaptive management experiment

Assessing carbon and nutrient inputs in a spring‐fed estuary using fluorescence spectroscopy and discriminatory classification

AbstractEnvironmental and chemical properties were investigated in water samples collected at sites in Kings Bay, Florida, within its springshed, and in the adjacent Crystal River, in an attempt to discover the cause of observed increases in nitrogen and nuisance filamentous algae over the past 40 yr. Colored dissolved organic matter (CDOM) was characterized by excitation emission matrix and absorption spectroscopy. Subsequent parallel factor analysis (PARAFAC) identified five recurring peaks: two terrestrial humic (C‐type), two marine humic (M‐type), and one protein‐like component. Optical and environmental parameters used for discriminant analysis included fluorescence maximum intensity (Fmax), emission maximum (Emmax), absorption coefficient [aCDOM (λ)], spectral slope (S), PARAFAC components, total nitrogen (TN), dissolved inorganic nitrogen, dissolved organic nitrogen, ratio of TN to Fmax (TN : F), total phosphate, and salinity. Canonical analysis of principal (CAP) coordinates indicated that 82% of the samples could be accurately categorized on the basis of their site of origin. Northern Kings Bay sites were characterized by a protein‐like component associated with wastewater, as well as DIN concentrations in excess of the United States Environmental Protection Agency limit of 0.35 mg NO3 L−1. Two distinct M‐type humic components were identified: partially photobleached component that was found in the brackish water and unbleached component found in meteoric groundwater. We propose that the latter can be utilized as a groundwater marker. Our results provide a model by which meteoric and subterranean estuary groundwater sources may be uncovered through the use of multiple environmental parameters combined with PARAFAC components in multivariate analyses.

Estimate Submarine Groundwater Discharge to Crystal River/Kings Bay in Florida with the Help of a Hydrodynamic Model

Crystal River/Kings Bay is a spring-fed estuarine system located on the west coast of the Florida peninsula. During 2008-2009, a field investigation was conducted to measure submarine groundwater discharges (SGDs) from numerous spring vents in Kings Bay. Based on directly measured real-time SGD data, an empirical relationship that links SGD with tides in Kings Bay and the groundwater level measured in a nearby Artesian well were obtained. A 3D unstructured Cartesian grid model was used to help verify the correctness of the empirical SGD formula, which was slightly adjusted for each individual vent when used in the model. The model was calibrated and verified against measured real-time data of water level, salinity, and temperature at two stations in the estuary. A successful simulation of circulations, salinity transport processes, and thermodynamics in the Crystal River/Kings Bay system proves that the empirical relationship is appropriate for estimating SGDs in Kings Bay.

Response of bacterioplankton community structure to an artificial gradient of &amp;lt;i&amp;gt;p&amp;lt;/i&amp;gt;CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; in the Arctic Ocean

Abstract. In order to test the influences of ocean acidification on the ocean pelagic ecosystem, so far the largest CO2 manipulation mesocosm study (European Project on Ocean Acidification, EPOCA) was performed in Kings Bay (Kongsfjorden), Spitsbergen. During a 30 day incubation, bacterial diversity was investigated using DNA fingerprinting and clone library analysis of bacterioplankton samples. Terminal restriction fragment length polymorphism (T-RFLP) analysis of the PCR amplicons of the 16S rRNA genes revealed that general bacterial diversity, taxonomic richness and community structure were influenced by the variation of productivity during the time of incubation, but not the degree of ocean acidification. A BIOENV analysis suggested a complex control of bacterial community structure by various biological and chemical environmental parameters. The maximum apparent diversity of bacterioplankton (i.e., the number of T-RFs) in high and low pCO2 treatments differed significantly. A negative relationship between the relative abundance of Bacteroidetes and pCO2 levels was observed for samples at the end of the experiment by the combination of T-RFLP and clone library analysis. Our study suggests that ocean acidification affects the development of bacterial assemblages and potentially impacts the ecological function of the bacterioplankton in the marine ecosystem.

Simulating hydrodynamics in a spring-fed estuary using a three-dimensional unstructured Cartesian grid model

This paper presents an application of a three-dimensional unstructured Cartesian grid model (Chen, 2011) to a real-world case, namely the Crystal River/Kings Bay system located on the Gulf coast of the Florida peninsula of the United States. Crystal River/Kings Bay is a spring-fed estuarine system which is believed to be the largest natural refuge in the United States for manatees during the coldest days in winter because of the existence of a large amount of discharge out of numerous spring vents at the bottom of Kings Bay. The unstructured Cartesian grid model was used to simulate hydrodynamics, including salinity transport processes and thermodynamics, in the estuary during a 34-month period from April 2007 to February 2010. Although there are some unidentified uncertainties in quantifying flow rates from the spring vents and salinity variations in spring flows, simulated water elevations, salinities, temperatures, and cross-sectional flux all match well or very well with measured real-time field data. This suggests that the unstructured Cartesian grid model can adequately simulate hydrodynamics in a complex shallow water system such as Crystal River/Kings Bay and the numerical theory for the unstructured Cartesian grid model works properly. The successful simulation of hydrodynamics in the estuarine system also suggests that an empirical formula that relates the spring discharge with the water level in Kings Bay and the groundwater level measured in a nearby well is reasonable.

Population Dynamics of the Western Australian Soldier Crab Mictyris Occidentalis Unno, 2008 (brachyura, Mictyridae) in the Dampier Archipelago — 30 Years of Observations

AbstractThe previously undescribed population dynamics of the Western Australian soldier crab, Mictyris occidentalis Unno, 2008, in King Bay, north-western Australia are elucidated, with annual observations and sampling over a 30-year period from 1980 to 2010. This is the longest recorded study of a single inter-tidal brachyuran population and shows long-term persistence of soldier crab populations in stable, sheltered habitats. The life cycle of M. occidentalis follows a cryptic subsurface juvenile and immature adult (= adolescent) phase and an emergent adult phase. Population densities were generally 500 crabs/m2 for the early 1980s, late 1980s, and during the early 2000s. Maximum population densities were high in the mid 1980s (800 crabs/m2). The spatial and temporal variability in the distribution of the population was consistent over the study period. Juvenile recruitment extends for up to 7 months of a given year between May and November with the main influx of juveniles usually in June and occasional minor influxes in August or October. Juvenile recruitment is followed by incremental growth of individuals at a rate of 1 mm/month reaching sexual maturity in the first year at 6.0-6.9 mm carapace length (CL). Adult males are larger than females with a maximum size of 15.0 mm CL compared to 12.0 mm CL, respectively. Ovigerous females are low in numbers throughout most of the year but reach a peak in February. During swarming, M. occidentalis populations partition not only by size class, with surface crabs being adults only and subsurface crabs mainly adult females and juveniles, but also by sex in that swarms are male-dominated in varying ratios.