REPORT SFRC-86/04 

Aspects of the Population 

Dynamics & Biology of the Stone 

Crab (Menippe mercenaria) in 

EVER & BlSC as Determined 

by Trapping 

Everglades National Park, South Florida Research Center, P.O. Box 279, Homestead, Florida 33030 
Aspects of the Population Dynamics and Biology -- of the Stone Crab (Menippe mercenaria) in 

Everglades and Biscayne National Parks 

as Determined by Trapping 

Report SFRC-86/04 

T. M. Bert, J. Tilmant, J. Dodrill, and G. E. Davis 

National Park Service 

South Florida Research Center 

Everglades National Park 

Homestead, Florida 33030 
Bert, T. M., Tilmant, J., Dodrill, J., and Davis, G. E. 1986. Aspects of 

the Population Dynamics and Biology of the Stone Crab (~eni~~e 

mercenaria) in Everglades and Biscayne National Parks as Determined by 

Trapping. South Florida Research Center Report SFRC-86/04. 
TABLE OF CONTENTS 

Page 

. . LIST OF TABLES .................................................. 11 

LIST OF FIGURES ................................................ iii 

ABSTMCT ....................................................... 1 

INTRODUCTION .............................................. 2 

AREA DESCRIPTION ................................................ 3 

Everglades National Park ................................... 3 

Gulf Coast ........................................... 3 

Florida Bay ..................................... 5 

Biscayne National Park ...................................... 6 

Southern Biscayne Bay .................................. 6 

Coral Reef Tract ....................................... 7 

PREVIOUS STUDIES ON THE STONE CRAB .............................. 7 

mTHODS ......................................................... 11 

Field Sampling .............................................. 11 

Statistical Analysis ........................................ 12 

KESULTS ......................................................... 13 

Seasonal Distribution ....................................... 13 

Relative Abundance ..................................... 13 

Adults ............................................ 13 

Juveniles ......................................... 14 

Sex Ratio ................................................... 14 

Spatial Differences .................................... 14 

Temporal Variation ..................................... 15 

Size Composition ............................................ 16 

Mean Size .............................................. 16 

Size Class Frequency ................................... 16 

Males ............................................. 16 

Females ........................................... 17 

Growth and Mortality ........................................ 17 

Molting ................................................ 17 

Mortality .............................................. 18 

Reproduction ................................................ 19 

Mating ................................................. 19 

Spawning ............................................... 20 

DISCUSSION ...................................................... 21 

Distribution and Abundance .................................. 21 

Spatial Distribution ................................... 21 

Temporal Variation ..................................... 22 

Aspects of Biology .......................................... 24 

Juveniles .............................................. 24 

Females ................................................ 24 

Males .................................................. 26 

CONCLUSIONS ..................................................... 27 

Population Biology .......................................... 27 

Life History ................................................ 29 

ACKNOWLEDGEMENTS ................................................ 30 

LITERATURE CITED ................................................ 32 
LIST OF TABLES 

Table Page 

1. Physical characterization of stations in Everglades 

National Park and Biscayne National Park used in 

this study .................................................... 42 

Outline of biological and morphological data 

recorded on stone crabs captured in this study ................ 46 

Stations with statistically similar mean numbers of 

stone crabs captured per trap as determined by the 

Wilcoxon-Mann-Whitney simultaneous test procedure ............. 47 

Stations with statistically similar numbers of juveniles 

settling on traps, based on simultaneous test 

procedure analysis of number of juvenile stone crabs 

per 5-trap line per month among stations..........,...........48 

Trapping stations having statistically similar sex 

ratios in the Gulf of Mexico, west Florida Bay, 

and Biscayne National Park tested for goodness of 

fit to 1:l sex ratio by G-test................................49 

Characteristics of station groups used for size 

class frequency analysis ...................................... 50 

Growth of male and female stone crabs from capture 

of molting crabs and their exuvia during this study... ........ 52 

Estimation of instantaneous mortality coefficient 

and total annual mortality rate for male and female 

stone crabs from Everglades ................................... 53 

Estimation of stone crab mortality rate in Everglades 

using proportion of stone crabs lost from the 

population within annual molt increments...,..................54 

Proportion of females that were found to be in gravid 

condition by area of capture within Everglades,. .............. 55 

Size of gravid females in relation to that of all 

females captured by area within Everglades .................... 56 

Growth of male stone crabs..,.................................57 
LIST OF FIGURES 

Figure Page 

la. Location of sampling stations in Everglades 

National Park.................................................58 

lb. Location of sampling stations in Biscayne 

National Park.................................................59 

2. Mean number of stone crabs captured per trap 

in monthly samples, by stations.......................... ..... 60 

3. Number of juvenile stone crabs found on adult 

stone crab traps, by month....................................bl 

4. Proportion of total catch comprised of male 

stone crabs, by month, for the Gulf of Mexico 

and western Florida Bay.. ..................................... 62 

5. Mean size (and standard deviation) of male 

and female stone crabs for each station at 

which crabs were captured, .................................... 63 

6. Mean size of male and female stone crabs 

at individual stations over time..............................64 

7. Ten millimeter size class frequencies of 

stone crabs by month.....,.................,..................65 

8. Proportion of females molting by month........................67 

9. Regression of female size on growth increment.................68 

10. Number of crabs per 2 mm size increment 

captured in nearshore southwest Florida in 

this study... ................................................. 69 

11. Proportion of female population found mating, 

by month, in the Gulf of Mexico and western 

Florida Bay... ................................................ 70 

12. Correlation between size of male and female 

stone crabs composing a mated pair ............................ 71 

13. Size of 50% maturity of male stone crabs, 

according to the method of Somerton (1980)... ................. 72 

14. Monthly variation in proportion of females in 

reproductive state in Everglades... ........................... 73 

15. Proportion of females molting, mating, and 

spawning, by age class, in Everglades........ ................. 74 

iii 
LIST OF FIGURES 

Figure Page 

16. Seasonal variation in proportion of females 

in three age categories found molting, 

mating, and spawning in Everglades..... ....................... 75 

17. Composite of percent of total trapped female 

stone crabs with eggs, by month, from all 

studies conducted in Florida..................................76 

18. Regression of growth increment on premolt 

carapace width in male stone crabs greater 

than 70 mm carapace width.....................................77 
ABSTRACT 

Stone crabs (Menippe mercenaria) were trapped on a lunar cycle (full moon) 

from June 1979 to June 1980 to investigate the population biology and life 

history of the organism in south Florida marine waters managed by the 

National Park Service. Seventeen stations, located throughout the coastal 

regions of Everglades National Park and Biscayne National Park, were 

fished for an entire year. Five additional stations were fished the last 

nine months of the study. An array of morphometric and biological data 

was taken on each crab captured. Salinity, temperature, water clarity, 

principal fouling biota, and bottom type were recorded at each station 

during sampling. 

Relative abundance, proportion of females, and number of juveniles were 

highest in Everglades National Park marine waters from Lostmans River 

northward. Also, mean size of both sexes was generally smallest in that 

region. Progressing southward along the Gulf of Mexico and east into 

Florida Bay, relative abundance of both adults and juveniles decreased, 

proportion of males increased, and mean size of both sexes became larger. 

Juveniles were never found at most stations sampled in Florida Bay. 

Biscayne National Park resembled Florida Bay in number and size of adults, 

proportion of males, and lack of juveniles. Juvenile distribution and 

abundance was directly correlated with relative abundance of adults and 

proportion of females in the trapped population. The primary source of 

adults in Florida Bay appears to be a very slow movement of crabs from the 

Gulf of Mexico progressively farther into Florida Bay. The stone crab 

population in Biscayne National Park may be dispersing from farther north 

along the Atlantic coast of Florida. 

Temporal changes in relative abundance, sex ratio, and size class 

frequency of female stone crabs captured were strongly correlated to 

various aspects of reproductive activity. Changes in values of these 

parameters for males were related to changes in water temperature and 

female reproductive activity. Differences in relative abundance and mean 

size of both sexes also corresponded to commercial fishing season near the 

seaward limits of Everglades National Park in the Gulf of Mexico, and to 

the number, proportion, and mean size of males in commercially fished 

areas of Florida Bay. Because of the simultaneous occurrence of natural 

and artificial factors affecting the trapped population over time, it is 

difficult to attribute observed variations to any particular factor. As 

determined by trapping, changes in the population biology of stone crabs 

in Everglades and Biscayne National Parks occurring during the year are 

cyclic, and the population recovers to its initial state by the onset of 

the next year. 

Female stone crabs produce eggs throughout the summer. Younger females 

peak in egg production in late summer and older females in late spring. 

Young females molt and possibly mate more frequently than older females, 

but egg production of the young segment of the female population is 

reduced. By age three, all females have apparently reached sexual 

maturity. Molting occurs from fall through spring in young females and 

molt frequency declines with increasing age until, at age four, females 

molt annually in the fall. Females increase in carapace width about 10 nun 

with each molt and can live to about age seven. 
Male stone crabs may molt throughout the year, but most appear to have 

recently molted in November. Annual molt increment in males decreases 

dramatically at about 70 mm carapace width, and averages about 16 mm 

carapace width for crabs greater than that size. Mo1.t increment in males 

shows twice as much variability as in females and decreases continuously 

with increasing size of crab. Males have a higher mortality rate than 

females, possibly due in part to their greater susceptibility to 

commercial fishing pressure. The majority of males mate in traps with 

females of their own age class, despite the discrepancy in size (males are 

larger). Evidence indicates that males reach sexual maturity at about 70 

mm carapace width, and develop a legally harvestable claw at a slightly 

larger size. 

INTRODUCTION 

The stone crab (Menippe mercenaria) supports a commercial fishery by 

virtue of its huge and delectable claws. Only the claws are harvested; 

trapped crabs are declawed in the field and returned to the water. 

Although stone cqabs are widely distributed in southeastern North America, 

by far the largest commercial fishery occurs in southwest Florida (Bert et 

al. 1978). About 80 percent of all U.S. annual landings come from the 

three southernmost counties in Florida (Dade, Monroe, and Collier), with 

Monroe and Collier counties having by far the highest production. In 

these three counties, stone crabs are the third most valuable commercial 

fish harvest after shrimp and spiny lobster (Prochaska and Cato 1974). 

Everglades Natioqal Park, spanning Monroe and Collier counties, forms the 

shorewardmost area of the large gulf fishery and may play an important 

role in maintaining the stock for that fishery (Figure 1). Biscayne 

National Park occupies approximately a fourth of Dade County's coastal 

waters and contributes to production in that county. 

Commercial stone crab fishing has been allowed in Everglades National Park 

and Biscayne National Park since their creation. Recently, the fishery in 

Everglades National Park has shown signs of stock depletion. Trap catch 

per unit of fishing effort (g claws/trap night) fell from 113 g to 29 g 

from 1972 to 1977, and economic extinction of the fishery occurred after 

two-thirds of the fishing season had expired each year from 1974 to 1976. 

While catch rate fell, the number of stone crabbers fishing the park 

increased from 35 in 1970-71 to 60 in 1975-76. 

Special park regulations governing the stone crab fishery at the time this 

study was undertaken prohibited harvest in all areas of Everglades 

National Park within 400 m of the coastline, and in the northern half of 

Florida Bay. Only males with a propodus (claw) length of 2.75 in (7 cm) 

could be taken in Everglades National Park. Outside of Everglades 

National Park, the state of Florida and the federal government allow the 

harvest of both sexes with this claw size (370.13 FL State Statutes; Fed. 

Reg. 44(65):19445-19496). Biscayne National Park allows harvest in 

accordance with state laws. Crabbers are limited to 400 traps in 

Everglades National Park and must have park permits in addition to their 

state permits. No trap limits are set for Biscayne National Park, state, 

or federal fishing grounds. Open season in the parks conforms with state 

and federal regulations (~ctober 15 through May 15). 

Depth of the inland bays and lakes in this system usually does not exceed 

2 my whereas the major streams and rivers may reach depths of 4 m or 

more. Offshore near the seaward margin of the park, water.depth increases 

from an average of 2 m at Everglades City to about 4 m at Cape Sable. 

Rainfall averages 125-135 cmjyr (Thomas 1974) and is seasonally divided 

such that 60-65 percent falls from June to August and only 8-10 percent 

from December to February (Carter et al. 19731, creating seasonal salinity 

variations that can be detected to the seaward limit of the park (Davis 

1940; Linda11 et al. 1973). The fresh water of inland bays and streams 

becomes brackish during the dry season, and oceanic influences can be seen 

several kilometers inland (Carter et al. 1973). Salinity along the gulf 

coast ranges down to 10 ppt during the rainy season, and typically 

approaches oceanic values (30-33 ppt) at the close of the dry season in 

early spring. Tidal influences on coastal salinity cause variations of 

several parts per thousand (Carter et al. 1973), but are secondary to wind 

and rain generated seasonal differences. At the seaward margin of the 

park, variations in salinity are dampened by mixing and normally range 

from 25-34 ppt, depending on season. However, isolated pockets of 

a~norrnally low or high salinity water can be encountered (up to 10 ppt 

greater or less than ambient), probably due to incomplete mixing. 

Vertical salinity stratification is usually negligible throughout the 

area. 

Water temperature drops to about 20 OC in winter, but may deviate 

substantially (Carter et al. 1973; present study), dependent upon the 

intensity of the season. Warmest temperatures are reached in July and 

August and coolest in December and January. The shallow waters of inland 

bays and streams begin to warm in February or March, earlier in the year 

than in the open gulf. Summer temperatures in July and August reach 

30-33 OC, and are commonly 1-3 OC warmer inland and along the 

coast than offshore. 

Normal tidal amplitude deviates + 40-70 cm from mean sea level, varying 

with phase of the moon. seasonal variations in level of the surrounding 

ocean (Marmer 19541, enhanced by predominant winds, greatly reduce the 

depths of inland, coastal, and offshore waters in winter and elevate them 

in late summer. 

Large amounts of organic compounds and detritus, wind mixing, and tides 

reduce visibility to nearly zero throughout most of the year in all water 

masses. Inshore waters occasionally become clear, although deep brown in 

color, at the end of the dry season. Visibility rarely exceeds 2 m 

of £shore. 

Algal components of the coastal estuarine and marine flora are composed of 

Garcilaria spp., Rhizoclonium (Carter et al. 19731, and Cladophora 

spp. in soft-bottomed localities and Udotea spp., and Batophora oerstedii 

(Schmidt and Davis 1978) on firmer substrate. The oyster shell and 

foliacious red algae accumulating in the channels provide habitat for 

large numbers of small crabs (Panopeus, Neopanope, Eurpaneopeus, 

Kithropanopeus, and Perilisthes spp.) and snapping shrimp (Alpheus spp.). 
Offshore, subtropical and warm temperate sponges and gorgonians are rooted 

to available hard substrate, interspersed with patches of turtle grass 

(Thalassia testudinum) and shoal grass (Halodule wrightii). Benthic 

filter feeders (barnacles, tunicates, sponges, worms, hydroids, and 

bryozoans) are very abundant and rapidly colonize any available substrate, 

forming dense, fast-growing colonies which shelter small mobile 

invertebrates, particularly juvenile Menippe mercenaria, isopods, and 

amphipods. 

Florida Bay 

Florida Bay, sandwiched between the upper Florida Keys and southern tip of 

mainland Florida, is a semi-enclosed triangular honeycomb of nearly 

emergent calcareous banks surrounding deeper (to 3 m) basins locally known 

as "lakes". Small islands of low elevation, called keys, appear at 

irregular intervals along the banks. Channels in the banks form avenues 

for water exchange between adjacent lakes. Water exchange with the open 

ocean is restricted except through channels between the upper Florida Keys 

and the broad banks forming the western border of the bay. As a result, 

tidal influences on water level are secondary to those generated by wind 

and seasonal fluctuations in ocean levels. Water level is generally 

higher in fall and winter, when north to northwest winds pile water into 

the bay and regional oceanic levels are higher, and lower in summer when 

south to southeast tradewinds blow water out of the bay (Ginsburg 1956; 

Tabb et al. 1961). Diurnal tidal variation of about 50 cm (McNulty et al. 

1972) is superimposed on these seasonal factors in western Florida Bay. 

Tidal influence is gradually reduced eastward in the bay. 

Florida Bay is underlain by Miami oolite (Cooke and Mossom 1929). 

Overlying sediments are chiefly fine-grained calcareous algal muds. Some 

transport of abiotic sediment occurs from the surrounding Gulf of Mexico 

into the western basins (Hoffmeister 1974). Sediment depth varies among 

basins and is generally greater in western and southern basins. 

Salinity varies greatly both seasonally and spatially in Florida Bay. The 

salinity in basins of northern and central Florida Bay changes seasonally 

and annually under the influence of freshwater runoff primarily from 

Taylor Slough (Schmidt and Davis 1978). Central Florida Bay contains 

extensive areas of very shallow (less than 1 m) water with restricted 

flushing and becomes very hypersaline during years of low rainfall (Tabb 

et al. 1961; Turney and Perkins 1972). Values of up to 70 ppt have been 

recorded (Finucane and Dragovich 1959). Proximity to the open gulf 

prevents such extremc. changes in salinity in southern and western Florida 

Bay. However, these areas commonly experience salinities of 40 ppt in 

summer despite greater flushing action. 

Recorded water temperatures in Florida Bay have a wider range than those 

in the Gulf of Mexico, extending from 10 OC (present study) to 

38 OC i ins burg 1956). In summer, temperatures are generally higher 

in shallow central Florida Bay and on mud banks than in the deeper basins 

of eastern and western Florida Bay. Restricted circulation and the 

shallow nature of the bay make it susceptible to large rapid drops in 

water temperature (to as low as 5 OC) during winter cold fronts (Tabb 

et al. 1961). 
Certain portions of Florida Bay are virtually always highly turbid: 1) 

the northern sector of the bay receiving freshwater runoff; 2) individual 

basins lacking sediment stabilizing benthic flora, and; 3) some basins at 

the southern margin of the park affected by wind and tidal mixing. 

Tabb et al. (1961) characterized the flora and fauna of Florida Bay as 

typical of the Carolinian biogeographic province. Benthic associations 

can vary substantially from basin to basin and range from vast seagrass 

communities to unconsolidated mud-dwelling complexes. Ginsburg (1956) and 

Turney-and Perkins (1972) found notable differences in the molluscan and 

foraminiferan assemblages among the basins in the bay, and Turney and 

Perkins (1972) separated the bay into four subdivisions based on 

differences in the molluscan fauna. 

Biscavne National Park 

Biscayne National Park encompasses the southern half of Biscayne Bay and 

extends seaward to the edge of the continental shelf (Figure 1). The park 

contains essentially two water masses of approximately equal size, a 

shallow tropical l'agoon and a typical Caribbean barrier reef extending to 

about 20 m depth (Schmidt and Davis 1978). Separating the two bodies of 

water are narrow islands of exposed Key Largo limestone. Several channels 

cutting between the islands connect the bay with the ocean. The deepest 

of these is about 3 m. - 

Southern Biscayne Bay 

The lagoon of southern Biscayne Bay is a semi-enclosed basin having 

restricted exchange with other water masses. The bay is bordered on the 

east and west by land masses and on the north and south by nearly emergent 

submarine banks. Freshwater flow into the bay is limited and comes mainly 

from mosquito control ditches and water management canals on the mainland. 

The western edge of the bay is lined by mangrove swamp. Seagrass flats, 

primarily turtle grass and shoal grass, extend seaward from the mangroves 

and give way to a sponge-gorgonian hard-bottomed community in places where 

the bedrock surfaces from beneath calcium carbonate biogenic sediments 

(Schmidt and Davis 1978). The deeper (to 3 m) eastern side of the bay is 

thickly overlain with calcium carbonate mud and contains sparse to dense 

beds of seagrasses mixed with calcareous green algae (Codiaceae). 

Tides range from about 50 cm near the mainland to 60 cm near the barrier 

islands (Schneider 1969). Prevailing easterly winds generate an elevated 

sea level in the western part of the bay. 

Salinity varies from nearly fresh to exceeding oceanic values within the 

bay, depending on season and location. During the rainy season, 

salinities can be much lower along the western shoreline. Severe 

rainstorms or prolonged heavy rains can lower salinity throughout the 

lagoon. For example, Voss et al. (1969) recorded a low of 5 ppt off 

Fender Point during October 1968 when salinity was lowered throughout the 

bay. In contrast, evaporation rate is very high, enhanced by east to 

southeast tradewind. Salinity in shallow portions of the bay occasionally 

reaches hypersaline values (Segar et al. 1971; Lee 1975). 
Bay waters are also susceptible to atmospheric changes in temperature. 

Water temperatures in winter frequently decline to 13-15 OC and may 

fall rapidly in response to winter cold fronts. Sumer water temperature 

usually ranges between 30-33 OC; de Sylva (1971) recorded an extreme 

of 41.7 OC near the mainland coast. 

Bay waters are normally clear except near the intercoastal water channel 

which roughly bisects the bay from north to south. However, strong 

sustained winds occasionally resuspend the fine-grained sediment sand and 

reduce visibility to essentially zero throughout the bay. 

Coral Reef Tract 

Between the barrier islands and deep waters of the Florida Straits lies a 

characteristic West Indian coral reef tract. The discontinuous outer reef 

is nearly emergent at low tide and is primarily composed of elkhorn and 

staghorn corals (Acropora spp.), and brain and star corals (~ontastraea 

diploria and Siderastrea spp.). Hawk Channel is a depression 5 to 10 m 

deep lying between the outer reef and islands. The channel is irregularly 

punctuated with patch reefs composed of heads of brain and star corals 

intermingled with staghorn coral and finger corals (Porites spp.) (Voss et 

al. 1969 lists the floral and faunal reef constituents). Sea feathers, 

whips, and fans (Alc~onaria) are frequently found topping the coral reef 

mass (Schmidt and Davis 1978). Turtle grass - beds interspersed with 

occasional patches of barren sand fill in the space between reef patches. 

Between the channel and barrier islands, seagrass flats generally give way 

to extensive areas of rocky bottom with soft corals, calcareous algae 

(Codiaceae and Corallinaceae), sponges, and small corals (Porites, 

Manicina). 

Proximity of the warm Gulf Stream ameliorates summer and winter extremes 

in temperature on the reef tract. Temperature can be 5 OC warmer on 

the seaward side of the islands than near the mainland in winter (present 

study), and temperature near the islands has a greater seasonal range 

(about 18-32 OC) than farther offshore (20-30 OC) (Smith et al. 

1950; Chew 1954; present study). 

Open ocean circulation also stabilizes salinity. Smith et al. (1950) and 

Jones (1963) reported salinity values of 37 ppt with very little 

variation. However, salinity may drop slightly near the cuts between 

barrier islands where lagoon water mixes with offshore water. 

Turbidity levels can be relatively high, particularly in winter and spring 

when strong northeast and east winds stir up bottom sediments. Visibility 

usually ranges between 10 m and 15 m. 

PREVIOUS STUDIES ON THE STONE CRAB 

Much of the early recorded information on the stone crab (Menippe 

mercenaria) is a documentation of its occurrence with some notes on 

variation in habitat with size and season (~athbun 1884, 1887; Hay and 

Shore 1918; Schroeder 1924; Rathbun 1930; Behre 1950; Parker 1959; Tabb et 

al. 1961; Tabb and Manning 1961; Bullis and Thompson 1961; Finucane and 

Campbell 1968; Powell and Gunter 1968). The stone crab has been recorded 
from Cape Hatteras southward along the Atlantic coast, throughout the Gulf 

of Mexico, in several of the leeward islands of the Caribbean, and, 

interestingly, possibly in the Black Sea (Abolmasona 1970). 

The species has recently been divided into two semi-species (~ert 1985), 

one ranging from the Florida panhandle through the northern and western 

Gulf of Mexico, and the other, in its pure form, through south Florida and 

into North Carolina. The two forms hybridize in northwest Florida and 

along the Atlantic from east central Florida into South Carolina. Four 

structural phenotypes and three hybrid phenotypes have been reported from 

Cuba, as determined by size and abundance of spots on carapace and claws 

(Ros et al. 1980). 

By far, the greatest abundance of the species is on the continental shelf 

of southwest Florida, from Naples to Key West (Bert et al. 1978). 

Detailed information on local distribution and abundance has been 

accumulated for the coasts of northwest Florida (~c~ae 1950; Bender 1971), 

southwest Florida (Sullivan 1979), southeast Florida (~oe 1967), and 

central South Carolina (Wenner and Stokes 1983). These studies also 

included various asp'ects of the life history of the organism obtained from 

direct observation and capture-recapture data. 

Six larval stages, five zoeal and one megalopal, were documented by Hyman 

(1925) and an occasional sixth zoeal stage by Porter (1960). Based on the 

number and morphology of larval stages, Scotto (1979) assigned the genus 

Menippe a primitive phylogenetic status, noting that the genus was more 

similar to cancrid c*rabs than to the Xanthidae. 

Ong and Costlow (1970) and Costlow (1970) found that larval stone crabs 

metamorphose most rapidly in warm (25-30 OC) water of near oceanic 

salinity (30-33 ppt). Stone crab larvae respond to elevated salinity (40 

ppt) by raising the levels of certain amino acids in the body (Tucker 

1978). Anger et al. (1981) calculated an increase in reaction rates for 

duration of larval development and in survival time with increasing 

temperature. Stone crab larvae exhibit a positive photo-response in high 

light intensities, a negative response in low light intensities, and 

rapidly sink if their light source is abruptly extinguished (Forward 

1977). 

The energetics involved in larval growth were calculated by Mootz and 

Epifanio (1974). Larvae starved immediately after hatching exhibit a much 

greater negative effect (stunted growth, death) than those starved after 

1-2 days of feeding (Anger et al. 1981). Feeding is critical at first 

hatching. Larvae reared on brine shrimp exhibited greater survival than 

those fed rotifers (Sulkin and van Heukelem 1980). Goy and Costlow (1980) 

determined the nutritional effects of feeding Artemia from different 

geographical locations. Details of the development and ontogeny of the 

mandibles and gastric mill (Factor 1980) and sex characteristics (Payen 

1974) have been studied in both larval and postlarval stone crabs. 

Bookhout, Costlow, and associates (Bookhout and Costlow 1972, 1974; 

Bookhout et al. 1972; Costlow 1979) found that sublethal doses of various 

pesticides and pollutants tend to increase the frequency of the sixth 

zoeal stage and reduce survivorship of the larvae. 
Juveniles in northwest Florida inhabit upper intertidal rocks singly, each 

juvenile possessing its own territory (Hazlett 1979). Savage and 

co-workers (Savage and McMahan 1968; Savage 1971b; Savage et al. 1974; 

Savage and Sullivan ms.) and Manning (1961) looked at various aspects of 

growth and molting in juvenile and adult stone crabs including rates of 

growth and effect of varying salinity and temperature on these rates. 

Cheung (1969) elucidated the relationship between endocrine control of 

growth and reproduction. 

Bender (1971), Perry et al.. (19831, and Bert (1985) have documented 

general habitat usage by stone crabs in northwest Florida, Mississippi, 

and southwest Florida, respectively. Studies on stone crab reproduction 

have included: 1) detailed accounts of the internal (Binford 1918) and 

external (Savage 1971a) fertilization process and mechanisms of its 

physiological control (Cheung 1969); 2) investigations of seasonality and 

fecundity (Noe 1967 and Bender 1971); 3) verification of transmolt sperm 

retention (Cheung 1968); and 4) mating habitat usage (Hembree 1984). Noe 

(1967) also described ten stages of female gonadal maturation, and an 

efficient precise method of conducting egg counts for fecundity 

measurements was formulated by Ros and Rojas (1978). 

An investigation of the respiration and osmoregulation of adult stone 

crabs submitted to salinity and temperature stress conditions was done by 

Karandieva and Silva Lee (1967). They found that stone crabs could 

withstand salinities of 6.0 to 7.5 ppt when gradually acclimated without 

additional oxygen consumption and could survive total oxygen deprivation 

for 17-21 hours. Bender (1971) also conducted studies on the relationship 

of temperature and salinity to osmoregulation. Stone crabs have a 

relatively low rate of oxygen consumption when compared to other crabs 

(Ayers 19381, a constant metabolic rate over a wide range of oxygen 

concentrations (Leffler 1973), and can withstand severe hypopia (Albert 

and Ellington, in press). Suarez and Diaz (1969, 1971) also conducted 

general physiological studies on stone crabs in Cuba. 

Stone crabs, voracious feeders, are known to eat mollusks of all types 

(Powell and Gunter 1968; Bender 1971). The mechanism and behavior they 

exhibit in opening various types of mollusk shells was described by 

Vermeij (1978) and Merz (1979). Vermeij (1978) and Kent (1983) discuss 

adaptations in mollusk shells to inhibit such predation. The damage they 

can inflict upon oyster beds when feeding is well documented (Menzel and 

Hopkins 1956; Menzel and Nichy 1958). They have also been reported to 

feed upon quahog clams (Mercenaria mercenaria) occasionally (Whetstone and 

Eversole 1978). Suchenia and Claro Madruga (1967) studied adult stone 

crab feeding energetics and found that stone crabs could exist for up to 

two weeks after consuming a maximum of food. 

The antagonistic disposition of the stone crab is well known among those 

who deal with the organism. Sinclair (1977), in the only behavorial study 

of the animal conducted to date, found a great deal of ritualism 

associated with intraspecific encounters, a common occurrence in agressive 

species. The ~rimary weapons of the stone crab are its large and 

formidable claws. Brown et al. (1979) measured 14,000 p.s.i. pressure 

exertion at the tip of the pincer claw in an adult stone crab. 
Stridulation, originally reported to be absent in the stone crab 

(Guinot-Dumortier and Dumortier 19601, has been observed and may serve an 

important function in territorial and mating behavior (Bender 1971; Bert 

et al. 1978). 

Electrophoretic work on the stone crab has included a single 

interpopulational study of haemocyanin (Rodriquez 1975) and a 

comprehensive investigation of geographic variation throughout the range 

of the species in the USA (Bert 1985). Protein variation with differences 

in sex, size, missing chelae, water temperature, reproductive activity, 

and ,diet were considered in Rodriquez's study. Only degree of starvation 

produced significant differences in the basic electrophoretic pattern. A 

study of the oxidative metabolism of stone crabs (Mauro and Magnum 1982) 

found that the performance of the haemocyanin-oxygen transport system was 

maximized at 15 OC, and that the gill was incompletely oxidized at 

25 OC. 

The only microhistological study conducted on stone crabs has been an 

investigation of the photoreceptor microvilli, when Eguchi and Wateman 

(1973) compared,a number of crabs. 

Several studies have shown that several common crab parasites infest stone 

crabs. Chitinoclastic bacteria cause "black spot" on the exoskeleton 

(Iversen and Beardsley 1976). Fungal parasites invade the ova (Bland ;nd 

Amerson 1975), and the goose-neck barnacle ectoparasite (Octolasmis 

auelleri) attaches to the gills of crabs in regions of hybridization 

(T. M. Bert, pefs. observ.). 

A commercial fishery is based upon the huge claws of the stone crab. If 

the crab survives the declawing process, it can regenerate its claws 

within one year (Sullivan 1979) or more. The nature of the fishery has 

generated much investigative interest in mortality and rates of 

regeneration associated with declawing. Davis et al. (1979) found that 

survivorship was greatly reduced when the basal-ischial declawing wound 

was greater than 14 mm in diameter; Schlieder (1980) found reduced 

survival after declawing following prolonged atmospheric exposure. Rates 

of claw regeneration have been documented for crabs of various sizes by 

Cheung (1973), Sullivan (19791, and Savage and Sullivan (1978). Claw 

removal at first crab stage has been shown to generate rapid growth 

(Rodriguez and Yang 1977). Cheung (19761, in a biostatistical study of 

the heteromorphic claws, deduced that "left handed" crabs (the term 

"handed" meaning the crusher claw) had developed from normal "right 

handed" crabs that had reversed crusher claws upon loss of the original 

right crusher claw. Recently, Simonson and Steele (1981) and Simonson (in 

press) have looked closely at claw reversal in all sizes of stone crabs. 

They believe that claw reversal occurs in young, but not necessarily in 

older, crabs. 

The biology and Florida fishery of the stone crab were reviewed in detail 

by Bert et al. (1978) and again by Lindberg and Marshall (1983). The 

Cuban fishery was reviewed and evaluated by Ros and Perez Perez (1979). 

Several additional reports on the economics, methods, and extent of the 

U.S. fishery have been produced by Florida Sea Grant (Prochaska and Cato 

1974, 1975; Prochaska 1976; Prochaska and Landrum 19811, the Florida 
Department of Natural Resources (Savage et al. 1975; Sullivan 1979) and 

National Marine Fisheries Service (Zuboy and Snell 1980, 1982). A fishery 

management plan for federal waters in the Gulf of Mexico has been in 

effect since 1979 (Costello et al. 1979). 

Mariculture efforts on stone crabs have met with very limited success. 

Among other problems in closed system stone crab culture, hydrozoans are 

reported to be significant pests (Sandifer et al. 1974). In the 

laboratory, stone crabs reared from eggs have reproduced successfully 

(Cook 1969; Lindner and Cook 1971; Yang 1971, 1972; Roberts 1975) and 

winter mating has been induced (McConaugha et al. 1980). Yang attempted a 

large-scale rearing experiment in outdoor tanks and ponds from egg to 

marketable adult (Yang and Krantz 1976). He experienced highly variable 

growth rates and very low survivorship. In essence, the stone crab is a 

high level cannabalistic carnivore with aggressive behavior and, thus, has 

food and space requirements which make the economic feasibility of 

mariculture questionable. Nevertheless, it has been incorporated into a 

program exploring closed system mariculture in both South Carolina 

(Sandifer and Smith 1974) and the Bahamas (Robert McConnaughey, Wallace 

Groves Aquaculture Foundation, Freeport, Bahamas, pers. comrn.). 

METHODS 

Field Sampllng 

Sampling by trapping was conducted throughout the coastal waters of 

Everglades National Park and Biscayne National Park. Seventeen stations 

were located in Everglades and five in Biscayne (Figure 1). Table 1 lists 

the physical characteristics of each station. Five plastic commercial 

stone crab traps (Isle of Capri Fisheries, Naples, Florida) were set at 

each station. Traps were placed linearly approximately 100 m apart and 

baited with processed ground herring crab bait (Atlantic and Gulf Fishing 

Supply Co., Miami, Florida). Traps were pulled on a lunar cycle on the 

full moon for a one year period. 

Traps were initially set at 16 of 22 stations during May and June 1979 

(Table 1) for acclimation to the water. All traps were pulled (taken from 

the water), cleaned of captured crabs, baited, and replaced in June to 

begin the study. Six more stations were added to the study in October. 

Traps used at these stations were not presoaked. All traps were sampled 

through June 1980. 

After a trap was pulled, an array of biological and morphological data was 

taken on each captured crab large enough to tag (about 30 mrn carapace 

width, CW) (Table 2). The crab was then tagged with a sphyrion spaghetti 

tag (Floy Tag Co., Seattle, Washington) if not previously tagged, and 

released. Additional notes were taken on biotic fouling organisms on the 

trap and on number of juveniles too small to tag found on the trap. Small 

juveniles were collected by first searching the interior of the trap, 

followed by scraping the entire exterior clean of fouling organisms and 

systematically sorting through the debris for the juveniles. The traps 

were then rebaited, tied closed with 100 lb test monofilament fishing 

line, and replaced on site. 
Surface, mid-water, and bottom salinity and temperature were taken with a 

salinometer, or surface salinity and temperature were taken with 

refractometer and thermometer. 

Statistical Analvsis 

Except where noted, statistical tests used followed procedures found in 

Steele and Torrie (1960); Snedecor and Cochran (1967); Sokal and Rohlf 

(1969). Overall spatial and temporal relative abundance for both adults 

and juveniles was evaluated by non-parametric methods. The Friedman test 

for randomized blocks was used to test for significant differences among 

months. This analysis was followed by the Kruskal-Wallis test to detect 

differences among stat2ons. The Wilcoxon-Mann-Whitney simultaneous test 

procedure (STP) was used to isolate differences when they did occur. 

Detailed analysis of relative abundance over time among individual 

stations or groups of stations was accomplished by completely random 

design analysis of variance and Student-Neuman-Kuel (SNK) range test for 

location of significant differences. 

I 

Where sample size was adequate or several stations could be logically 

pooled, the heterogeneity G-test was employed to investigate variations in 

sex ratio over time and space. The interactive capacity of this test 

allowed statistical =omparisons to be made among stations and among months 

and enabled partitioning of homogeneous sets of replicates into 

significant groupings by the STP. In cases where sample size was too 

small for the G-fest, actual probabiliiies were calculated or results were 

simply discussed. 

Statistical analysis of size, molt frequency, mating, and spawning for 

spatial and temporal variation was done using completely random design 

analysis of variance or t-test for detection of significant differences 

and SNK range test for partitioning the differences. The data from 

several months or stations were frequently pooled for an~lysis in the most 

logical and statistically meaningful manner to compensate for the 

recurring problem of small sample size. 

The Somerton (1980) method of estimating size of 50 percent sexual 

maturity was employed to estimate size of reproductive maturity in males. 

This method utilizes the shift in allometric proportions of two body 

dimensions that commonly occurs when crabs reach sexual maturity to 

estimate the size at which a randomly chosen individual has a 50 percent 

chance of being sexually mature. 

Two methods of calculating annual mortality rate were used. The Hancock 

(1965) approach involves the calculation of an instantaneous mortality 

coefficient (Z) for crabs by using annual molt increment and numbers of 

crabs in small size classes within the molt increment. The slope of the 

least squares line generatea by plotting size against the natural 

logarithm of numbers of crabs of that size is proportional to the total 

mortality rate (Nt = ~,e'~~) over the range in which growth is 

effectively constant. In this case, mortality coefficients were 

calculated for each sex and each molt increment possible. Annual 

mortality rate was also calculated for each sex and molt increment using 
proportion of animals lost (or gained) between adjacent 2-mm size 

classes. The proportions were summed for all size classes within a molt 

increment to give estimates of percent of the population lost within that 

molt increment. 

Temporal and spatial relationships among biological (relative abundance of 

adults and juveniles, sex ratio, spawning, molting) and physical 

(salinity, temperature) factors were investigated using multiple and 

simple correlations. Generally, three-factor multiple correlation was 

used to test one biological factor against either two other biological, or 

the two physical factors. 

RESULTS 

Seasonal Distribution 

Relative Abundance 

Adults: Because some stations were sampled for an entire year (13 

samples) and others for only part of the study period (9 samples), overall 

differences in relative abundance were analyzed twice using the same 

statistical methods. Only the 16 stations sampled throughout the year 

were evaluated for the entire sample period, and all 22 stations were 

analyzed for the nine samples. 

Both sampling groups showed highly significant differences among stations 

(p is less than .005). Rank analysis grouping stations with statistically 

similar means for the two periods (Table 3) showed that two stations 

sampled throughout the year (Northwest Cape and Sandy Key Channel) had a 

sufficiently lower mean number of crabs per trap line when only 9 months 

were averaged so as to change them to a grouping of lower relative 

abundance. Of the other stations sampled throughout the year, two 

(Pavilion Key and Outside Lostmans River) showed slight decreases, and six 

(Conchie Channel, Twin Key Basin, Lostmans River Channel, Pelican Bank, 

Inside Sands Cut, Tern Keys) showed slight increases, in mean relative 

abundance when averaged from only November to June. However, in no case 

was the magnitude of change great enough to change the grouping of any 

station. 

No significant differences in relative abundance among months were 

detected for either group analyzed. To further investigate changes in 

relative abundance over time, individual stations were analyzed for 

changes in average number of crabs captured per trap per month. Only four 

stations showed significant variation in mean catch over time (Northwest 

Cape, p less than .05; Conchie Channel, p less than .01; Sandy Key 

Channel, p less than .01; Inside Sands Cut, p less than .001). Figure 2 

illustrates mean catch per trap per month for each station. No overall 

patterns in catch rates over time were readily apparent, but several 

different trends were seen among the stations. Several stations had mean 

catch rates that were generally higher in summer and fall and lower in 

winter and spring (Outside Lostmans River, Northwest Cape, Sandy Key 

Channel, and Billys Point). Shark Point and Arsenicker Keys also appeared 

to follow this trend, with a delay factor of two months (however, these 
stations were not sampled i.n summer and early fall). A number of other 

stations showed a marked increase in relative abundance in spring and/or 

early summer over other times of the year (Chokoloskee Bay, Black Betsy 

Keys, Tern Keys, Blackwater Sound, and Outside Sands Cut). Bimodal peaks 

in catch rate occurred at several stations. Of the stations sampled 

throughout the year, Pavilion Key, Captain Key, and Pelican Bank had 

relatively high catch rates in fall and spring, while Lostmans River 

Channel, and Conchie Channel had winter and spring peaks. Chatham Bend 

and Twin Key Basin also had winter-spring peaks, but were not sampled 

during all fall months. Only six of the 21 stations at which stone crabs 

were captured did not show elevations in catch rates sometime between 

March and June (Shark Point, Sandy Key Channel, Arsenicker Keys, Captain 

Key, and Billys Point). Of the stations sampled throughout the year in 

the Gulf of Mexico, only'Chokoloskee Bay and Lostmans River Channel did 

not show additional fall maxima. 

Juveniles: Juvenile stone crabs were found on traps only at Gulf of 

Mexico stations and at Conchie Channel in Florida Bay, with the exception 

of one juvenile found in September at Billys Point in Biscayne Bay. The 

vast majority of juveniles were less than 5 m CW. Thus, the number of 

juveniles found on the traps was taken to be representative of the number 

settling at about that point in time. 

Similarly to the analysis of adults, spatial differences in relative 

abundance of juveniles were analyzed twice--once using only stations 

sampled throughout the year and once using all 22 stations for nine 

samples. Some0stations were significantly different from others in both 

instances (p less than .001). No stations changed groupings, as they did 

for adults. A composite of similar stations was derived from the two 

analyses (Table 4). Stations in the high number category (the offshore 

Gulf of Mexico, north of the Shark River) had 86 percent of all juveniles 

captured. Thirteen percent of the juveniles came from tbe.moderately low 

group (coastal gulf at the mouths of estuaries and offshore gulf, from the 

Shark River southward) and only one percent from all other stations 

(Lostmans River channel, Florida Bay channels and basins, and Biscayne 

National Park). 

An obvious peak in settlement from September through'~ovember occurred at 

most stations where juveniles were found (Figure 3). Only Shark Point 

displayed a notably delayed peak in recruitment. The monthly number of 

juveniles settling was significantly greater during the three peak 

settlement months than during the rest of the year (p less than .01). 

Sex Ratio 

Spatial Differences 

Overall, a significant deviation from a 1:l sex ratio (p less than .001), 

was observed due to higher capture rates of males. The proportion of 

males also varied significantly among trapping locations (p less than 

.01). In northeast Florida Bay, overall sex ratios (ma1e:female) were 1:l 

at Black Betsy Key, 1:2 at Tern Keys, and 11:4 at Blackwater Sound. At 
Conchie Channel, virtually only males were caught, while at some northern 

gulf and Florida Bay stations, sex ratios were not significantly different 

from 1:l (Pavilion Key, Outside Lostmans River, and Captain Key). The 

stations clustered into two distinct groups (Table 5). A group with very 

high proportions of males was composed of stations in the Gulf of Mexico 

below Lostmans River (except Sandy Key Channel), Lostmans River channel, 

and Biscayne National Park. Stations with significantly more females were 

located in the Gulf of Mexico from Lostmans River northward, the basins of 

Florida Bay, and at Sandy Key Channel. 

Temporal Variation 

Sex ratios (ma1e:female) differed significantly among months in the Gulf 

of Mexico and western Florida Bay (p less than .001), but not at other 

locations. A significantly higher percent of males was captured from late 

summer to early winter at these stations (p less than .001) (Figure 4). 

However, most of this monthly variation was due to changes at those 

stations falling into the statistical group with a relatively low 

proportion of males. Those stations showed an abrupt decrease in the 

proportion of males captured from March to July. The ratio again abruptly 

changed to very high proportions of males after July. The group of 

stations with relatively high proportions of males also differed 

seasonally (p less than .01), but the changes in sex ratio were not as 

distinctive. Only the month with the lowest sex ratio (February) was 

statistically different from the months with the highest ratios (August 

and December/January).' However, the percent of males was somewhat lower 

from January through June than in the remainder of the year. 

In northeast Florida Bay (Black Betsy Keys, Tern Keys, and Blackwater 

Sound), females were only captured in spring and summer. When present, 

the females greatly outnumbered males (April to August sex ratio, 3:14). 

Only males (n=8) were caught from late summer through winter (September 

to February). March was apparently a transition month with a M:F s2x 

ratio of 5:l. No crabs were captured from October to January. 

In Biscayne National park, low catch success made determinations of sex 

ratio questionable. Only January had a sex ratio approaching 1:l. Sex 

ratios varied greatly for other inonths, and no seasonal trends were 

apparent. Few females were captured in Biscayne National Park over the 

entire study period, but pooling the monthly data according to the 

seasonal pattern seen in Everglades National Park resulted in a lower sex 

ratio from January through July than from August to January (ma1e:female = 

35:4 and 60:3, respectfully). 

The greatest actual number of males per trap was captured from November 

through June at all stations in the Gulf of Mexico and channels leading 

from the gulf to Florida Bay, except at Northwest Cape and Sandy Key 

Channel, where number of males captured was highest in summer. The 

greatest number of males was captured in February and March in the basins 

of Florida Bay, and in DecemberIJanuary, March, and April in Biscayne 

National Park. 
Size Composition 

Mean Size 

Size distribution of crabs (mm CW) captured followed a normal 

distributional curve. Therefore, the mean and standard deviation of size 

was used for statistical comparisons over time and space. 

Mean size of both male and female stone crabs varied greatly among sites 

sampled (Figure 5). For males, all stations offshore in the Gulf of 

Mexico north of Shark Point, along with Lostmans River Channel had the 

smallest mean size and were statistically similar. The two remaining gulf 

stations located close to shore had small males, but significantly larger 

than the offshore stations. Northwest Cape had intermediate-sized males 

and did not fall into any group. All stations in Florida Bay and Biscayne 

National Park formed a group with large males. Northeast Florida Bay had 

substantially larger males than did the remainder of the bay. In Biscayne 

National Park, mean size of males increased from the coast to the reef. 

Although groupslof statistically similar size were not as clearly defined 

for females, inspection of the data revealed essential categories--a group 

with small females in the Gulf of Mexico and one with large females in 

Florida Bay and Biscayne National Park. Mean size of females generally 

increased with movement southward in the gulf and into Florida Bay. As 

with males, the largest females were found in northeast Florida Bay. Only 

a few females, of all sizes, were captured in Biscayne National Park. 

Monthly comparison of mean size, where sample sizes were adequate, 

revealed significant differences at three stations for males and two 

stations for females (Figure 6). All offshore Gulf of Mexico stations and 

Conchie Channel showed a decline in mean size of males during winter. 

Shark Point, Northwest Cape, and Sandy Key Channel exhibited a reduction 

in mean size of males in spring and early summer. Conchie Channel had a 

decline in mean size of males in September, a pattern not seen elsewhere. 

Females in the offshore gulf from Lostmans River northward also showed a 

winter reduction in mean size. Shark Point had a decline in female mean 

size in spring and early summer, analogous to the situation for males at 

that station. 

Size Class Frequency 

Ten millimeter size class histograms were used to further investigate 

change in size of stone crabs during the study. Three criteria were used 

to group stations for histogram comparisons; 1) statistical similarity of 

overall mean size; 2) comparability of geographical location and habitat; 

and 3) similarity of seasonal variation in mean size. A station was 

omitted from the analysis if it could not be categorized by these 

standards. In cases where a station fell into two different groups, 

overall mean size and geographical location were given priority. Table 6 

lists groups constructed for both sexes and characteristics of each group. 

Males: Figure 7 presents size class frequencies by month for the station 

groups in Table 6 that had sufficient numbers of crabs to illustrate 

general trends. In the offshore Gulf of Mexico, modal size usually ranged 
between 90-100 mm CW. Notable increases in small size classes (less than 

80 mm CW) were seen from fall to spring. The size of most crabs captured 

clustered around the mode from August through December, followed by a 

spread with all size classes more evenly represented through June. 

Largest size classes (greater than 120 mm CW) were found from February 

through June. 

Except for December, modal size of males in the nearshore Gulf of Mexico 

was 100-110 mm CW from fall through winter. Size distribution was usually 

clustered tightly about the mode. Smaller size classes (less than 80 mrn 

CW) were captured in relatively high frequencies in December, with a 

return to larger classes in January when the largest males were captured 

(to 140 mm CW). Modal size decreased to 90-100 mm CW in spring, 

influenced by a reduction in mean size of crabs captured at Shark Point. 

Modal sizes in Florida Bay were large (110-130 mm CW) most of the year. A 

shift to smaller size classes occurred in September and October, when 

modal size dropped to 100-110 mm CW. Smaller size classes were also 

collected in January when only a few males of a broad range of size 

frequencies were caught. Highest proportions of large males (greater than 

130 mm CW) were captured in February and April. 

No distinct mode was usually apparent in Biscayne National Park males. 

However, many large males (greater than 120 mm CW) were taken in the 

December/January sample and all small males (less than 80 mm CW) were 

trapped from July through December. 

Females: A distinct mode of 90-100 mm CW was observed in July and August 

for the offshore gulf (Figure 7). An increase in the proportion of 

smaller females (less than 70 mm CW) occurred from September to November, 

during which time no clearly definable modal size was present. Virtually 

all crabs collected in December and January were less than 100 mm CW and 

modal size dropped to 40-50 mm CW in January. In February, a shift back 

toward larger crabs began until modal size reached 80-90 mm CW in May and 

June. 

A distinct modal size was not evident for the nearshore Gulf of Mexico, 

possibly due to low sample sizes. However, comparatively smaller crabs 

(all less than 90 mm CW) were obtained in March, whereas larger crabs were 

captured in February and April (all greater than 60 mm CW). No influx or 

efflux of any size class was apparent. 

In Florida Bay, size frequencies could only be identified for February 

(90-100 mm CW) and March (100-110 mm CW) due to low catch rates. All 

females collected were less than 110 mm CW in the fall. Most females were 

more than 90 mm CW the remainder of the year, ranging to 130 mm CW in all 

months except January. 

Growth and Mortalitv 

Molting 

Seven males and 33 females were molting at the time of sampling during 

this study. A crab was considered to be in the molting state if it had a 
soft exoskeleton (postmolt) or was beginning to emerge from its old 

exoskeleton which had separated at the molting suture lines (premolt). 

Twenty-six molting fenlales were found at the offshore Gulf of Mexico 

stations, five at nearshore gulf stations, and two in west Florida Bay. 

Four molting males were captured offshore and one nearshore in the Gulf of 

Nexico, one in west Florida Bay, and one in Biscayne National Park. All 

molting females were observed from September to June, with bimodal peaks 

in late fall and in spring (Figure 8). Males were found molting in July, 

September, January, March, and April. Analysis of variance and 

Student-Neuman-Kuel range test determined that mean size of females 

molting in the fall (Sept.-Nov.) (x=87.3; S.D.=16.8 mm CW; N=lO) was 

significantly larger than that of females molting in winter (Dee.-Feb.) 

(x=60.6; S.D.=18.5 nun CW; N=10) or spring (~ar.-~une) (x=69.1; 

S.D.=9.7 mm CW; N=13) (p less than .01). 

Intermolt growth increments for four males and 12 females were available 

from capture of postmolt crabs and their exuviae at the time of sampling 

(Table 7). We recaptured no tagged crabs of either sex which had grown 

while at large, Growth of males, in both absolute change and percent 

increase in size, was greater than that of females. Nodel I linear 

regression of female growth showed that growth rate was constant over the 

size range available for testing (Figure 9). Curvilinear regression was 

tested by x + 1 and log x transformation, but linear regression gave the 

best fit to the data. 

Mortality , 

Mortality coefficients were computed for adult stone crabs collected from 

the western Florida coast (Gulf of Mexico plus Florida Bay). Crabs were 

separated into 2-mm size classes for estimates of age class mortality 

(Figure 10). The size class captured in the greatest proportion was used 

as 100 percent trap retention length (102-104 mm CW, males; 94-96 mm CW, 

females). Molt increments of 16 nun CW for males (Everglades National 

Park, unpublished data) and 10 mm CW for females able 7) were used to 

define year classes, with the 100 percent retention length as the starting 

point. Molt frequency was assumed to be annual over the range for which 

mortality rates were calculated (~heung 1969; Sullivan 1979; Everglades 

National Park, unpublished data). 

Table 8 presents the results of the Hancock (1965) method of estimating 

mortality rate and shows a large discrepancy for both sexes in total 

annual mortality between the two age classes examined, with the older 

class undergoing the higher rate of mortality. In addition, mortality 

rate of females for both molt increments is substantially lower than that 

of males. Table 9 gives the total mortality estimate using a second 

method which assumes a constant recruitment level for all years. Results 

closely agree with those obtained using the Hancock method. These 

estimates indicate that about 99 percent of the males alive at the start 

of the 102-104 nun CW size class died within the following two molt 

increments. Approximately 83 percent of the females alive between 
94-96 mm CW were lost by the time they reached 112-114 mm CW, also two 

molt increments. 

Mating 

Over the course of our field sampling, a number of pairs of stone crabs 

were trapped while in mating condition. A pair was classified as a mating 

pair if one or more of the following criteria were met: 

1. The female was paired with a male defending her and she was in 

the premolt or postmolt condition. 

2. The only female present in the trap was paired with her defending 

male and all other males had been killed. 

3. The female and her defending male were spatially separated from 

other crabs in the trap, as identifiable when the mating pair 

would be found in the bait cup attached to the upper corner of 

the trap. 

Although most stone crabs are typically aggressive to varying degrees, the 

type of aggressive behavior exhibited by a male defending an appare~tly 

sexually receptive female was easily distinguishable. When a stone crab 

of either sex is approached for removal from t!~e trap, its avoidance 

behavior characteristics include both presentation of the claws and 

independent movement around in the trap. A defending male presents his 

claws and is usually aggressive but does not move. Rather he will remain 

above the unresponsive female trying to maneuver her under his walking 

legs. Once the male is removed, the female generally remains relatively 

unaggressive and attempts to hide rather than defend herself against the 

intruder. Savage (1971) noted similar behavior of mating pairs in burrows 

during field observation. 

We found 34 mating pairs from September through June; 35 in the offshore 

Gulf of Mexico, 7 along the gulf coast, and 2 in wzstern Florida Ray 

channels. The highest proportion of the population found mating xas in 

the fall, notably October (Figure 111, with another lesser peak in April. 

For statistical analysis of size of mating pairs vs. time of year, and 

size of crabs composing a mated pair, the size of mating females was 

standardized to postmolt carapace width where necessary by adding 10 mm to 

the premolt measurement. The mean size of mating crabs of both sexes in 

spring (March-June) (males: ~~89.4, S.D.=12.0 mm CW; females: ~~71.9, 

S.D.=8.5 mm CW; n=23) was significantly smaller (analysis of variance, p 

less than .01) than mean size in fall (Sept.-Nov.) (males: x=106.5, 

S.D.=9.4 mm CW; females: x=87.4, S.D.=16.0 mrn CW; n=ll). A highly 

significant correlation (p less than .01) existed in size of males and 

females composing a mated pair in the traps (Figure 12). The size of 50:; 

reproductive maturity in males is 71 mm CW (Figure 13). 
Spawning 

Spawning females were observed only in Everglades National Park 

(Table 10). The largest number of gravid females was found along the gulf 

coast, but the highest relative proportion of gravid females was captured 

in northeast Florida Bay. 

Mean size of ovigerous females in both the Gulf of Mexico and Florida Bay 

was significantly larger than mean size of all females (Table 11). This 

observation would be expected in the gulf, where large numbers of small 

females were captured. However, all females captured in Florida Bay were 

well above the average reported minimum size of spawning (about 

40 mm CW). No statistically significant differences were found in mean 

size of gravid females among months in any area, due to the high 

variability in reproductive size. However, most crabs spawning in winter 

in the Gulf of Mexico were 10-20 mm CW smaller than the mean size of 

gravid females for all other months. The highest percentage of spawning 

females in the Gulf of Mexico occurred in mid-summer (Figure 14), with a 

lesser peak occurring in May. 

Females from Everglades National Park were divided into age classes to 

further investigate the variation in proportion of females among 

reproductive stages with increasing size (Figures 15 and 16). Studies on 

growth of stone crabs have shown that females reach an average size of 

about 40-60 mm CW at age one, 60-80 mrn at age two, and increase their 

carapace widths by about 10 m per year after that (Savage and McMahan 

1968; Cheung 1969; Yang and Krantz 1976; Savage and Sullivan 1978; 

Sullivan 1979; present study). 

Females of age classes 1 and 2 were found to molt twice as frequently as 

older age females (Figure 15) and molted with equal frequency during all 

seasons in which females were found molting (Figure 16). Older females 

molted essentially only after the summer spawning season, and not in 

spring. The proportion of females of age 1 found mating was not 

significantly greater than that of older age classes, but age 2 females 

mated with significantly greater frequency (p less than .05) than age 

classes 4 through 7, and age 3 females mated with significantly greater 

frequency than ages 4 and 5 (Figure 15). Females more than 3 years old 

were only observed mating in the fall, whereas smaller females mated not 

only in the fall, but in winter and spring as well (Figure 16). 

A relatively low proportion of females less than age 3 were found in the 

ovigerous condition (Figure 15). From age 3 to age 6, the proportion was 

consistently slightly under 30%. Most 7 year old females captured were 

gravid. Females of age groups 3 and older-than-3 contributed 

significantly greater proportions (p less than .01) of the spring spawning 

effort compared to that of the younger-than-3 age group (Figure 16). No 

spawning in any age group was observed in October and November, when 31 

and 46 females were captured, respectively. Winter spawning in age groups 

3 and older-than-3 was only observed in February; no females in these 

groups were found spawning from October through January. 
DISCUSSION 

Distribution and Abundance 

Spatial Distribution 

In general, the greatest number of adult stone crabs was found in the 

offshore Gulf of Mexico north of the Shark River and in the channels that 

connect Florida Bay to the gulf. The greatest number of juveniles and 

highest proportion of females were seen in the offshore Gulf of Mexico 

from Lostmans River northward. Also, stone crabs in that section of the 

gulf were smaller than those found elsewhere. Progressing southward along 

the gulf and east into Florida Bay, both adults and juveniles continuously 

declined in number, adults became larger, and the proportion of males 

generally increased. Like Florida Bay, Biscayne National Park had few, 

generally large, crabs, a high percentage of males, and no juveniles. 

With movement from the mainland coast to the reef, relative abundance 

dropped and average male size increased. 

Of the biological and physical factors considered in this study (see 

Statistical Analysis section), the distribution and abundance of adults 

was correlated solely to the distribution and abundance of juveniles (p 

less than .05). As far as is known, no unique stone crab predators or 

competitors are present in areas of low relative abundance, and habitat 

and food do not seem to be limiting resources in at least some of these 

areas (T.M. Bert, pers. observ.). Similarly to this study, Bender (1971) 

trapped his greatest catches in offshore areas of the Cedar Keys. 

Juvenile distribution and abundance was correlated with relative abundance 

of adults and also to proportion of females in the trapped population (p 

less than .05). There was a highly significant interactive component 

between the two factors in determining relative abundance of juveniles (p 

less than .005). Although a number of females was collected in the basins 

ot Florida Bay, and spawning females were present, no juveniles were ever 

collected. Plenty of juvenile habitat was available on the fouled traps. 

The fouling community was, in most cases, similar to that seen in areas of 

high levels of juvenile settlement. Juveniles have been reported to be 

relatively common in west Florida Bay in the past (Manning 1961; Tabb et 

al. 1961). However, no juveniles were sighted in 230 man-hours of -- in situ 

searching by SCUBA in the basins of west Florida Bay during a concurrent 

study to be published elsewhere. 

Environmental factors that may contribute to the absence of juveniles from 

some areas include seasonal extremes in salinity and temperature in 

Florida Bay and Biscayne Bay and rapid salinity fluctuations in coastal 

and inshore areas during the summer rainy season. Salinity and 

temperature (see Area Description) reach levels harmful or lethal to 

larvae and juveniles at these times (Ong and Costlow 1970; Bender 1971). 

Juvenile stone crabs utilize a wide variety of substrates for cover (Hay 

and Shore 1918; Powell and Gunter 1968; Bender 1971), and it is doubtful 

that substrate for settlement is limiting, particularly since some of the 

most extensive expanses of suitable substrate are found in areas where 

juveniles are rare or absent. It seems unlikely that larvae or juveniles 
would migrate from these areas. Extensive larval or juvenile migrations 

are not known for stone crabs. 

The size of a stone crab, as with most other organisms, is indicative of 

its age. The significant difference in size of both sexes over the area 

encompassed in this study indicates that stone crabs may spatially 

segregate by age, or that fishing practices have gleaned the largest crabs 

from certain areas (T.M. Bert, unpublished data). Males reach an average 

size of about 40-60 mm carapace width at one year of age, 60-90 mm at two 

years, 90-110 - at three years, 110-125 mrn at four years, and 125-140 mm 

at five years (Savage and McMahan 1968; Cheung 1969; Yang and Krantz 1976; 

Savage and Sullivan 1978; Sullivan 1979; Everglades National Park, 

unpublished capture-recapture data on 67 males). Based on this size/age 

relationship in males, and on that of females previously discussed (see 

Spawning), stone crabs of both sexes are predominately two- to three-years 

old in the Gulf of Mexico. In Florida Bay, most males are four years of 

age in the western part of the bay and five years old in the eastern part; 

most females are four to five years and six-years old in these respective 

sections of the bay. Males range from two to seven years of age in 

Biscayne NationaL Park, with the older age classes predominating seaward. 

Temporal Variation 

Several stations in the Gulf of Mexico and channels connecting Florida Bay 

to the gulf were lower in relative abundance of adults during the fishing 

season. One station south of the Shark River and one in a gulf-to-bay 

channel dropped significantly. No unusual variations in salinity or 

temperature occurred at these stations. If crabs moved from these sites, 

the movement was to waters farther offshore or to areas not sampled, 

because compensatory increases in relative abundance did not occur at 

other sites monitored within the park. Commercial fishing pressure has 

previously been attributed to the seasonal reduction of relative abundance 

(Sullivan 1979; Wenner and Stokes 1983) and mean size (Savage et al. 

1975), and may contribute to the decrease in abundance of crabs at these 

stations. 

Changes in relative abundance at other stations were related to a number 

of factors. The entry of females into traps seemed to be strongly 

influenced by seasonal molting and spawning. In the month preceeding 

spawning, a number of metabolic and physiological changes occur within the 

female (Noe 1967; Cheung 1969). These changes may have induced females to 

enter traps which, in turn, affected the sex ratio of crabs in the traps. 

The ~roportion of females in traps was correlated to percent of gravid 

females captured (p less than .05) when the latter factor was delayed by 

one month. The proportion of females trapped was negatively correlated to 

molting (p less than .05), and molting and spawning were interactive (p 

less than .05) in their influence on the ratio of females to males in 

traps. In the Gulf of Mexico, sex ratio was also highly correlated with 

salinity (p less than .01), but not with temperature. The correlation 

with salinity in the gulf may only be an autocorrelate since the rainy 

season and spawning season coincide and the rainy season strongly 

influences salinity along the open gulf coast. 
The greatest number (but not necessarily highest proportion) of females 

was captured in spring in the gulf, when large females began spawning and 

smaller females molted and mated; some elevation in numbers occurred 

coincident with the fall molting peak in the coastal gulf and the basins 

of Florida Bay. Females do appear to enter traps in greater numbers 

during molting season. The negative correlation seen between molting and 

proportion of females trapped may be the result of the combined effect of 

the inverse relationship between molting and spawning (see Aspects of 

Biology), and the fact that trapped molting females probably attract males 

to traps so that the sex tatio reflects the disproportionate entry of 

males competing for receptive females. More crabs of both sexes entered 

traps during molting season, and the increase in number of males was 

greater than that of females. In previous studies, Noe (1967) and 

Sullivan (1979) also trapped the highest proportion and number of females 

during spawning season. Noe also noted a small increase in number of 

females in traps coincident with the fall molting season and drop in water 

temperature. 

Both the proportion and number of males captured fell from January to June 

at most stations. The proportion of males could not be correlated to any 

obvious internal seasonal biological processes, as could females, but was 

negatively correlated to salinity (p less than .05). Here, as with other 

studies (Noe 1967; Bender 1971; Bert et al. 1978; Sullivan 19791, most 

males entered traps after a sudden drop in water temperature in winter, 

and when females also entered with greater frequency during their molting 

season. 

In the gulf and gulf-to-bay channels, the decline in the proportion and 

number of males observed during winter was more noticeable at fished 

stations, probably due at least in part to the removal of males from the 

park by commercial fishermen (Bert et al. 1978). Also, in the gulf and 

adjacent channels, no spring peak in number of males captured was seen, 

contrary to the situation in both the basins of Florida Bay and Biscayne 

National Park. Many commercial traps were observed at the two stations 

where the decrease in abundance of males was statistically significant. 

More males were collected during the closed season (M~Y 16 to October 15) 

at these stations than at any other time of the year. Noe (1967) and 

Bender (1971) had disproportionate numbers of female crabs throughout the 

year when stone crab fishing laws allowed only the taking of male crabs. 

During the year, sex ratio changed more dramatically in the northern gulf 

coast area above the Shark River and in the basins of Florida Bay, than it 

did in the southern gulf and gulf-to-bay channels and Biscayne National 

Park. With the exception of Sandy Key Channel, stations that dramatically 

shifted in sex ratio fell into the low proportion of males group. 

The winter-early spring decline in mean size of males and females in the 

gulf from Lostmans River northward could have been due to a number of 

factors. 1) The decline was highly correlated with temperature (males: 

p=.01; females: p less than .01). The decrease in temperature may have 

triggered a differential behavioral response among the age classes. 

Bender (1971) noted seasonal change in mean size of males in traps due to 

movement of different size classes into or out of an area. The increase 

in number of smaller males was also associated with a decline in 
proportion of males and/or relative abundance at several stations. 

Possibly small males are deterred from entering or remaining in traps 

stocked with large crabs. Size class frequency of males spread from the 

mode during this period, whereas females shifted modes and entire age 

classes disappeared. Large females may simply not enter traps during 

certain seasons. 2) Larger crabs may have been removed from the 

population through commercial harvest. The slight decline in CPUE seen 

concurrently with the decrease in mean size in this region supports this 

suggegtion. The fact that females are affected similarly to males implies 

that either the influence of the commercial fishery harvest, conducted 

outside the park boundary, is seen within the park or, alternatively, that 

the change in mean size was not due to the fishery. 3) Smaller size 

classes may have molted to a size at which they were retained in traps, 

causing an influx of small crabs in the traps. Seasonal molting and the 

growth of year classes have been previously related to changes in mean 

size and size range during the year (Sullivan 1979). However, such an 

event should result in an increase in CPUE, contrary to the observed 

decline. t 

Aspects of Biology 

Juveniles 

Laboratory studies have shown that larval stone crabs proceed through 

development to settlement in 14 to 28 days, with most observations 

centering around21 to 28 days (Ong and Costlow 1970; Bender 1971; Yang 

1971; Mootz and Epifanio 1974; Yang and Krantz 1976). Our study indicates 

that stone crab larvae may have a longer pelagic life in nature than has 

been seen in the laboratory. Correlations between peak spawning and peak 

settlement months were highest (p less than .01) when a three-month delay 

was applied to spawning time. Allowing a mean of four to seven days for 

maturation of eggs (Binford 1918) and three to four weeks for molting to 

modal size of captured juveniles (about 3.5 mm CW) (Savage and McMahan 

1968; Yang and Krantz 19761, the larval stone crabs would had to have 

spent an average of about eight weeks in the plankton. 

Ong and Costlow (1970) and Bender (1971) reported a lengthening of time 

spent in the water column at temperatures and salinities below or above 

the optimum (30 OC; 30-35 ppt). Reduced salinities associated with 

the summer rainy season may have contributed to the longer settlement time 

we observed. Nearshore Gulf of Mexico stations, which showed delayed peak 

settlement when compared to offshore stations, also exhibited reduced 

salinities later in the year than did offshore stations. 

Females 

Molting in females is closely associated with reproduction since females 

can only mate when they molt and the exoskeleton is soft. However, 

molting apparently is not always an indicator of reproduction, 

particularly in younger crabs. Females begin to reach sexual maturity at 

about age one (McRae 1950; Powell and Gunter 1968; Cheung 1969; Bender 

1971; Savage and Sullivan 1978; present study), but a substantial number 

may molt without mating. The low proportion of gravid females in this age 

class supports this idea. Similarly to age one females, females of age 
two also have a low proportion of gravid females despite equivalence in 

percentage of crabs molting and mating in that age class. Either these 

females have not matured enough to spawn (although they can mate), or they 

put forth fewer spawns during the season than do older crabs. Either the 

age at which females attain full reproductive maturity is highly variable, 

or reproductive maturation is a slow process in stone crabs. 

Previous observations (Cheung 1969; Bender 1971; Sullivan 1979) have 

indicated that large stone crabs of both sexes molt once per year, and 

smaller females more frequently. Our data show that large females molt 

only in the fall, whereas smaller females molt in all seasons except 

summer. If the fall moltings of large females are indeed annual, the 

incidence of multiple ecdyses during the year sharply declines at age 

tnree. Only a small proportion of that age group molts or mates more than 

once per year. Beyond age three, females settle into a predictable 

pattern of molting and mating only once a year, in fall. The proportion 

of gravid females in the trapped population also doubles at this age and 

reaches the value held for most remaining age groups, suggesting that all 

females have reached reproductive maturity by this age. 

Differences in timing of mating among age groups are reflected in peak 

spawning months of those groups. Bimodal peaks in April-May and 

August-September are seen when all ages are grouped. But different age 

groups contribute to those peaks. One- and two-year-old females mate in 

spring and subsequently contribute to the late summer spawning peak. They 

are the only age group to mate and spawn in mid-winter. Age three females 

have a greater proportion of females mating in fall and spawning in spring 

than younger crabs. Older age classes, mating in fall, exhibit a definite 

burst of spawning activity in spring. It is apparent that mating in fall 

promotes early synchronous spawning the following spring. Other 

researchers have also recorded similar bimodal spawning peaks for Florida 

stone crabs (Figure 17). 

Since they may molt more than once between consecutive spawning seasons, 

young female stone crabs have an increased probability of becoming 

fertilized by more than one male per spawning season. The concurrent high 

incidence of mating in two- and three-year-old crabs indicates that they 

may in fact mate more than once a year. Trans-molt sperm retention has 

been documented in the species (Cheung 1968). Details of the storage of 

sperm from more than one male are currently being investigated (D. Wilber, 

Florida State Univ., pers. corn.). 

The timing of molting and spawning necessarily oppose one another and the 

two processes are therefore negatively correlated (p less than .01, Noe 

1967; p less than .05, present study) in the stone crab. Spawning acts to 

inhibit molting at the hormonal, physiological, and physical levels (Noe 

1967 and Cheung 1969). Molting in crabs is also inhibited by cooler 

temperatures (Passano 1960). Thus, most molting is restricted to fall and 

spring when spawning is at low levels and water temperatures are not yet 

at yearly minimums. 

The initiation and cessation of spawning activity are evidently regulated 

by external factors acting on hormonal controls (Cheung 1969). All 

studies on seasonality of spawning conducted to date have indicated that 
temperature is an important factor in determining spawning season (Noe 

1967; Cheung 1969; Bender 1971; Sullivan 1979; present study (p less than 

0 However, neither the onset nor termination of spawning is 

controlled by a specific temperature, at least within the annual 

temperature range usually encountered in Florida. The incidence of gravid 

females increases notably at any time in spring (Figure 17). Temperatures 

recorded at the time of increased numbers of gravid females in past 

studies have ranged from 22-24 OC in March and April for Sullivan's 

and Noe's data, to 25-29 OC in May and June for Bender's study, and 

25-29 OC in April and May for our study. When spawning activity 

decreases abruptly in October and November, temperatures recorded have 

ranged from 26-18 OC (Bender 1971) to 28-26 OC (present study). 

Cheung (1969) has suggested that light intensity plays an additional role 

in the control of spawning season. 

Mating is also correlated to temperature (p less than .05) and, of course, 

to molting (p less than .05). However, molting is not correlated to 

temperature due to the high proportion of crabs undergoing ecdysis in 

early winter after water temperature has reached minimum values. The data 

suggest that a number of females molting late in the year may not be 

fertilized. young stone crabs would presumably have another mating 

opportunity in spring, but older crabs would not and would be forced to 

rely on sperm retained after the molt for fertilization the following 

spawning season. 

Stone crab claws are comercially harvestable at 70 mm propodus length. 

In females, this corresponds to a carapace width of approximately 87 rmn 

(Sullivan 1979; )resent study). This size is within the same size class 

at which the female population reaches 100% sexual maturity (80-90 mm CW). 

Males 

Male stone crabs evidently lack seasonal regulatory controls on growth 

comparable with those found in females. Data is scanty, but our findings 

and those of others (Bender 1971; Sullivan 1979) suggest that males molt 

at any time of the year. 

An Everglades National Park unpublished capture-recapture study suggests 

that incremental growth in males is both greater and more variable than 

that of females. In that study, time at large varied from 1 to 64 weeks 

(x=19 weeks). Molt increment did not significantly increase with time at 

large in any size class, with the exception of a single crab at large for 

64 weeks (Figure 18). Thus, we might assume that only one molt occurred 

in these animals while they were at large. Data on the 67 males show an 

average variation of about 30 percent increase in size per molt for 10 mm 

size classes, and that increment of growth declines with increasing size 

(Table 12). Similar variation in females is about 15 percent (combining 

data from Sullivan 1979 and Table 7). The young males recaptured (less 

than 70 mm CW) grew a great deal more than did larger size classes. These 

males either molted more frequently or had disproportionately larger 

increases in size at molting. These males were at large from 13 to 26 

weeks. 
The notable reduction in growth shown by the Everglades National Park data 

occurring at about 70 m CW suggests that males may undergo a shift in 

energy allocation at that size, possibly due to the onset of reproductive 

activity. The calculated size of 50% sexual maturity (71 rrnn CW) supports 

this idea (Fig. 13). 

Males seem to have higher mortality rates and shorter life spans than do 

females. At least a portion of that difference could be attributable to 

commercial fishing. Trapping may capture disproportionate numbers of 

males. Males attain a larger size than females and have a proportionately 

larger claw size to body size ratio (Sullivan 1979). Both factors 

probably contribute to a greater retention of males in traps by reducing 

agility and mobility and the probability of successful escape. In 

addition, males enter the fishery at a smaller size than females 

(78 mm CW) (Sullivan 1979; present study) and are, therefore, subject to 

removal through fishing mortality, which may be quite high 

(Bert et al. 1978; Davis et al. 1979; Schleider 1980) at an age when 

females are still protected. 

Males tend to mate with females of the same age class in traps. 

Two-thirds of the mating pairs observed were probably in the same age 

class, and all but three pairs were within plus or minus one age class. 

Circumstantial evidence (e.g. a higher incidence of male deaths in traps 

during mating season) indicates that males compete for females to serve as 

mates. Competition for mates may favor larger males (~ert 1985). Males 

were older than their mates in 75 percent of the mating pairs we collected 

with an age differential between mates. 

About 65 percent of males had claws of minimum legal size that were 

involved in mating activity. Males reach harvestable size at age two, 

coincident with the beginning of most reproductive activity in both 

sexes. We found very few male crabs with claws below legal size that were 

mating. 

CONCLUSIONS 

Po~ulation Bioloev 

The presence of relatively large numbers of young adults, newly settled 

juveniles, and a high proportion of females in traps are spatially varying 

population characteristics which seem to indicate the location of 

productive stone crab recruitment areas. Such an area exists in 

Everglades National Park marine waters from Lostmans River to the northern 

boundary of the park. High larval production apparently occurs from the 

relatively great numbers of females in this region. Juvenile settlement 

is successful, with good survivorship to adulthood. 

The relative abundance of newly settled juveniles decreases with movement 

south along the gulf' below Lostmans River and into Florida Bay until it 

reaches zero throughout much of the bay. Although gravid females are 

found throughout the bay, newly settled juveniles are found only in 

seaward channels of the bay. Mortality at either the egg or larval stage 

increases to 100 percent with movement south of Lostmans River and into 

Florida Bay. Two explanations are plausible. 1) Locally hatched larvae 
do not survive to metamorphosis in areas removed from the upper Gulf coast 

region of the park. Physiochemical or biological change in quality of the 

environment such as salinity and/or temperature extremes are likely 

contributing factors in the basins of Florida Bay, but would not account 

for the decrease in numbers of juveniles observed progressing southward in 

the gulf. Two major estuarine drainage systems flow into the gulf above 

Cape Sable. Moving southward, water characteristics become increasingly 

oceanic along the Gulf of Mexico and gulf-to-bay channels of Florida Bay. 

Alterations in environmental characteristics associated with remoteness 

from estuarine influences could reduce survival of larvae. 2) Hatching of 

eggs is unsuccessful outside of the recruitment area and larvae are 

transported south from this area along the gulf, around Cape Sable and 

into gulf-to-bay channels, where some settle. This case would suggest 

that some characteristic(s) of the environment present in the recruitment 

area and possibly associated with estuarine influences is necessary for 

egg maturation. However, we saw no overt indications of premature 

spawning or abnormal egg development in gravid females from areas where 

newly settled juveniles were rare or absent. 

Either case implies that the primary source of stone crabs in Florida Bay 

is dispersal of adults from the more northern Gulf of Mexico recruitment 

ground. Rather than a single-year migration, the movement of a stone crab 

progressively farther into Florida Bay may take years and would be 

difficult to monitor in capture-recapture studies (e.g. Sullivan 1979). 

(Unpublished data from Everglades National Park on 46 male crabs from a 

one-year capture-recapture study conducted in west Florida Bay showed 

movement of males into the basins of the bay without compensatory movement 

back into the Gulf of Mexico.) 

Biscayne National Park, like Florida Bay, appears to lack a local juvenile 

recruitment source. Adult or juvenile stone crabs do not seem to move co 

the east coast of Florida in significant numbers from either the open Gulf 

of Mexico or Florida Bay. The nearest known concentration of juvenile 

stone crabs north of the bay is in the vicinity of Indian River in east 

central Florida. Possibly a slow movement of crabs southward from the 

Indian River area accounts for a percentage of the Biscayne population, 

analogous to the situation in Florida Bay. 

Although it is possible that older age classes have been removed from the 

offshore Gulf of Mexico by years of intensive fishing, park waters close 

to shore in the gulf and in much of Florida Bay have been protected from 

fishing of both sexes, and females have always been protected throughout 

both parks. Therefore, it is doubtful that the overall pattern of 

regional distribution and abundance observed in this study could solely be 

an artifact of commercial fishing. 

Temporal changes in sex ratio occur primarily due to large shifts in 

number of females entering traps and are therefore most noticeable in 

Everglades National Park north of the Shark River and in the basins of 

Florida Bay, locations where the greatest proportion of females are found. 

The number and size of females entering traps is, in turn, evidently 

strongly influenced by their reproductive cycle. Greater numbers of 

females enter traps throughout molting (=mating) and spawning seasons. 
Mean size of females in traps tends to be largest in fall, when older 

females molt, and smallest in winter, when only very young females molt. 

Male entry into traps may be affected by female molting season. Greater 

numbers of males are found in traps when large females are also abundant 

in traps during their fall molting season; Males also enter traps in 

noticeably greater numbers during the cold season, particularly after a 

sudden drop in temperature. 

Superimposed on the physical and biological factors relating to the 

movement of stone crabs into traps is the influence of the commercial 

fishing season. Apparently, the fishing season considerably affects the 

number, sex ratio, and size of crabs of both sexes entering traps. Traps 

near the Gulf of Mexico border of the park experience decreased catch 

rates in legal-sized crabs of both sexes during fishing season, possibly 

reflecting their proximity to commercial fishery grounds governed by the 

state, where both sexes can be harvested. Larger size crabs increase in 

frequency during spring, at least in part because sublegal crabs molt and 

replenish those size classes. Commercially fished stations in Florida 

Bay, remote from the recruitment ground, exhibit declines in proportion of 

males as the fishing season progresses. Stations that are intensely 

fished can become essentially devoid of males. At the time this study was 

conducted, males had to be removed from park waters to be declawed, due to 

the nature of the laws governing the fishery, and were not available for 

trapping if they survived the declawing process. 

Previous and concurrent studies have shown that the segment of the 

population seen in traps may or may not be representative of the true 

population structure at that time. A complex interactive array of 

biological, physiological, and social factors enters into the observed 

seasonal change in number, sex, and size of stone crabs entering traps. 

Therefore, it is difficult to determine whether the changes in these 

characteristics of population biology as seen in traps actually reflects 

populational shifts occurring in nature. Even assuming that changes in 

population parameters in traps are indicative of the natural situation, 

one cannot attribute an observed change to a particular factor because the 

various influences occur simultaneously over time. 

Life Historv 

Sufficient information has been amassed from this study and others 

conducted in south Florida to synthesize a view of the life history of 

stone crabs in the region. In south Florida, most stone crabs are hatched 

in mid-summer (July through September), spend one to two months as larvae 

in the pelagic mode of life, undergo metamorphosis, and settle as very 

small (1.5-2.0 mm carapace width) juveniles in the fall (September through 

November). These crabs molt frequently and reach a size of about 30-40 mm 

carapace width by the following fall (age one) and can be easily 

differentiated sexually. 

At age one, females molt and some mate during the winter. They may molt 

and mate again the following spring. The proportion of females that are 

capable of spawning is low at this time, or if all females are capable of 

spawning, they spawn less frequently than older females. Those that spawn 
do so primarily in late summer (August and September). Most females reach 

a size of about 60-70 mm carapace width with the fall molt at the 

beginning of their second year and many mate. Winter molting and mating 

still occur, but is not prevalent as in the first year. Most females molt 

and mate again in spring and peak in spawning activity'during late 

summer. A greater percentage, but not all, are mature enough to spawn in 

the summer of their second year or, alternatively, spawning frequency 

increases. The majority of females are about 70-80 mn carapace width 

after the fall molt at the onset of their third year, and most mate during 

the molting season. Very few, if any, females molt in the winter of their 

third year, but some molt and mate the following spring. Age-three 

females probably spawn throughout summer and all are sexually mature. 

Possibly those who successfully mated the previous fall did not molt in 

spring and were early spawners. Female stone crabs molt to about 90-100 

mm carapace width and mate again in fall at the close of their third 

year. They are then available to the commercial fishery. The winter and 

spring molts are virtually eliminated by the beginning of the fourth 

year. At that age, the animals fall irkto a synchronous reproductive 

pattern which is sustained for the remainder of their lives. They 

annually molt aqd mate in fall, retain and store the sperm throughout the 

winter, and spawn the following spring through summer. Peaks in spawning 

activity occur around May and August. Females four-years old and beyond 

increase in size (carapace width) an average of approximately 10 mm per 

year and can live to be about seven years old. 

Male stone crabs below 70 mm carapace width (age one) apparently grow at 

least twice as rapidly as those greater than that size, annually 

increasing that body dimension by about 35 mm or more. Annual increase in 

carapace width for crabs larger than 70 mm ranges from approximately 19 mm 

for crabs 70-80 mm carapace width (age two) to 15 mm or less in crabs 

greater than 110 mm carapace width (age four). Growth in male stone crabs 

is both greater and more variable than in females. Males molt at any time 

ok year, but primarily in late fall. Aging a male by his size is 

undoubtedly subject to greater error than aging a female. Male stone 

crabs below 70 mm carapace width apparently rarely or never mate. This 

fact, together with the substantial reduction in annual growth increment 

and allometric shift in body proportions that occurs at about that size, 

suggests that size at which a male has a 50 percent chance of being 

reproductively mature is near 70 mm carapace width (beginning age two). 

Males tend to mate with females of their own age class in traps and rarely 

mate with females as large or larger than themselves. Males enter the 

commercial fishery shortly after most have reached sexual maturity, at a 

smaller size than females, and at least as a partial consequence, have a 

higher mortality rate. Males live to be about six-years old. 

ACKNOWLEDGEMENTS 

This research would not have been possible without the strong support of 

many individuals from the various divisions of Everglades National Park. 

In particular, we thank the park rangers at the Everglades City, Flamingo, 

and Key Largo stations for outstanding cooperation and logistical 

assistance. We are also deeply grateful to the maintenance personnel in 

the park for assistance in the mechanics of keeping the equipment 

functional, and to our fellow researchers for providing field assistance 
when needed. A project of this scale cannot be successful without the 

cooperation of many individuals. 

We appreciate the skillful assistance of Catherine Sikkema, Diane Peebles, 

and David Williams for drafting and photographing the figures, and Jessie 

Brundige and Barbara Blair for typing and editing many drafts of the 

manuscript. Finally, we thank John Stevely, Florida Sea Grant Program and 

Harriet Perry, Gulf Coast Research Laboratory for critically reviewing the 

manuscript. 
LITERATURE CITED 

lbert, J. L., and Ellington, W. R. Patterns of energy metabolism in the 

stone crab, Menippe mercenaria, during hypoxia and subsequent recovery. 

J. Expt. 2001. In press. 

Abolmasona, G. I. 1970. Size weight characteristics of some Black Sea 

crabs. Gidrobiol. Zh. 6(1):85-90. 

Anger, K., Dawirs, R. R., Anger, V., and Costis, J. D. 1981. Effects of 

early starvation periods on zoeal development of Brachyuran crabs. 

Biol. Bull. 161(2):199-212. 

Ayers, J. C. 1938. Relationship of habitat to oxygen consumption by 

certain estuarine crabs. Ecol. 19:523-527. 

Behre, E. H. 1950. Annotated list of fauna of the Grand Isle region. 

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Table 1. Physical characterization of stations in Everglades National Park and Biscayne National Park 

used in this study. (See Figure 1 for location of stations.) 

station1B2 Salinity(ppt) Temp (OC) Depth ~urb~ Bottom Predominant ~ocalit~~ 

x(SD)/Range x(SD)/Range (m) TY pe Benthos ___ -------------________________________---------------------------------------------------------------- 

AREA : 

GULF OF MEXICO 

Chokoloskee 26(5)/18-34 

Bay (CKB) 

Indian Key 29(5)/20-35 

(INK) 2 

Chatham Bend 25(8)/19-35 

( CTB) fi 7 

h) 

Pavillion Key 30(3 1/26-34 

(PVK) 1 

Lostman Second 11(7)/2-22 

Bay (LSBl1 

Lostmans River 24(4)/17-33 

Channel (LMIl1 

Outside Lost- 31(4)/20-34 

mans River 

(LMO) 1 

Shark Point 20(4)/26-36 

(SPT)~ 

26(5)/18-32 0.7 high soft mud 

16(5)/18-33 1.2 high hard sand, 

small rocky 

outcroppings 

26(6)/18-34 2.0 high oyster shell 

25(5)/18-34 3.0 high hard sand, 

small rocky 

outcroppings 

26(6)/18-33 1.0 high soft mud 

26(6)/17-34 1.7 high oyster shell 

25(5)/18-31 2.0 high hard sand, 

small rocky 

outcroppings 

25(5)/18-31 1.2 high hard mud 

oysters inshore, in bay 

sponges, offshore, near 

soft corals seaward, edge 

of park 

oysters close to shore, 

mouth of estuary 

sponges, offshore, near 

soft corals seaward edge4 

of park 

algae inshore, in bay 

oysters close to shore, 

in river channel 

sponges offshore, near 

soft corals seaward edge 

of park4 

barren close to shore, 

mouth of estuary* 
Table 1 continued. 

......................................................................................................... 

~tationl,~ Sa1inity(ppt) Temp (OC) Depth ~urb3 Bottom Predominant ~ocalit~~ 

x(SD)/~ange x(SD)/~ange (m) TY pe Benthos ......................................................................................................... 

Northwest Cape 33(3)/28-38 25(5)/18-31 3.5 mod. hard sand, sponges, offshore, near 

(NWC)~ high small rocky soft corals seaward edge4 

outcroppings of park 

AREA : 

FLORIDA BAY 

Conchie Channel 35(3 1/31-40 

(ccH) 

25(4)/19-31 3.0 high soft sand unknown west bay, 

channel to Gulf 

of Mexico 

Sandy Key 35(2)/32-38 * 

w Channe 1 

(SKC) 

25(4)/19-32 3.0 mod. 

high 

west bay, 

channel to ~ulf~ 

hard sand, 

rocky outcroppings 

sponges, 

algae 

of Mexico 

Arsenicker 34( 11/33-37 

Keys ASK)^ 

25(6)/14-31 2.3 mod. 

low 

basin, west 

bay4 

so£ t sand, 

rocky outcroppings 

sponges, 

soft corals 

Twin Key Basin 35(2)/32-39 

(TKB)~ 

25(6)/14-31 2.0 low so£ t sand, 

rocky outcroppings 

basin, west 

b ay4 

seagrass, 

sponges 

Captain Key 35(4)/26-42 25(5)/16-31 1.2 mod. 

( CPK) 1 

so£ t sand barren basin, west 

bay4 

25(6)/15-31 1.5 mod. 

high 

Black Bets P 32(6)/26-42 

Keys (BBK) 

soft mud barren basin, northeast 

bay 
Table 1 continued. 

.......................................................................................................... 

station1S2 Salinit~(~pt) Temp (OC) Depth Turb3 Bottom Predominate ~ocalit~~ 

x(s~)/Jiange x(~~)/~ange (m) Type Benthos .................................................................................................... 

Tern Keys 36(5)/30-45 25(6)/15-32 1.2 mod. hard sand barren basin, northeast 

(TNK)~ GW bay 

Blackwater 33(3)/29-38 25(5)/14-30 2.0 low soft sand seagrass basin, northeast 

Sound (BWS)~ bay 

AREA : 

BISCAYNE BAY 

Pelican Bank 31(6)/20-36 24(6)/13-31 1.5 low soft sand, sponges, mainland side 

(PLB)~ small rocky soft corals of lagoon 

outcroppings 

C 

C- Billys Point 34(2)/31-36 24(6)/13-31 2.0 low soft sand sponges, shoreward side 

(BLP)~ soft corals of barrier 

islands4 

Inside Sands 34(2)/32-36 25(6)/14-31 2.5 low soft sand seagrass shoreward side 

Cut (SCI)~ of barrier 

islands4 

AREA : 

BISCAYNE REEF 

Outside Sands 34(2)/32-36 25(5)/18-30 1.5 low hard sand, seagrass, seaward side of 

Cut ( SCO) small rocky sponge, barrier islands4 

outcroppings algae 
Table 1 continued. 

_---___ ..................................................................................... 

~tationl,~ Salinity(ppt) Temp (OC) Depth ~urb~ Bottom Predominant ~ocalit~~ 

x( s~)/~ange x(~~)/Range (m) TY pe Benthos ......................................................................................................... 

Sands Cut 34(1)/32-36 25(3)/20-29 5.0 low soft sand, seagrass, offshore, patch 

Reef (SCR)~ coral reef corals reef4 .................................................................................................... 

*commercially fished very late in the season 

lstations sampled from June 1979 to June 1980 

2stations sampled from October 1979 to June 1980 

3turbidity is a qualitative judgement based on average color and clarity of the water 

4stations in zone open to commercial fishing 
Table 2. Outline of biological and morphological data recorded on stone 

crabs captured in this study. 

........................................................................ I. Biological Data 

A. Capture Category 

1. New capture 

2. Recapture 

3. Dead 

4. Molt 

B. Sex 

C. Claw Type 

1. Crusher 

2. Pincer 

3. Regenerated crusher 

4. Regenerated pincer 

D. Molt state 

E. Degree of fouling and principal fouling organisms . 

'3. Reproductive status (females only) 

G. Injuries 

11. Morphological Data 

A. Carapace width 

B. Carapace length 

C. Propodus width 

D. Propodus length 

E. Dactyl length 
Table 3, Stations with statistically similar mean numbers of stone crabs 

captured per trap as determined by the Wilcoxon-Mann-Whitney 

simultaneous test procedure. Statistical differences among stations 

were determined by Kruskal-Wallis test (H3149.2*, 15 df, for 

stations sampled throughout the year; H=43.57*, 21 df, for stations 

sampled October through June). (Note: The Wilcoxon-Mann-Whitney 

procedure is a rank analysis test and does not necessarily imply 

that stations in the various groups are all significantly different 

from each other in.the parametric sense.) 

Dates High Moderate Low Zero 

Sampled Relative Relative Relative Relative 

Abundance1 Abundance2 Abundance3 Abundance4 .............................................................................. 

June 1979- Pavilion Key Lostmans River Chokoloskee Bay Lostmans 

June 1980 Outside Lostmans Channel Blackwater Sound Second 

River Twin Key Basin Black Betsy Keys Bay 

Northwest Cape Captain Key Tern Keys 

Conchie Channel Pelican Bank 

Sandy Key Channel Billys Point 

Inside Sands Cut 

Oct. 1979- Indian Key Lostmans River 

June 1980 Chatham Bend Channel 

Pavilion Key Northwest Cape 

Outside Lostmans Sandy Key 

River Channel 

Shark Point Twin Key Basin 

Conchie Channel Arsenicker Keys 

Captain Key 

Chokoloskee Bay Sands Cut 

Blackwater Sound Reef 

Tern Keys Los tmans 

Black Betsy Keys Second 

Pelican Bank Bay 

Billys Point 

Inside Sands Cut 

Outside Sands Cut 

From June 1979 - June 1980, "high" ranged from means of 10-21 crabs per 

trap line; from Oct. 1979 - June 1980, "high" ranged from means of 18-26 crabs 

per trap line. 

From June 1979 - June 1980, "moderate" ranged from means of 6-8 crabs per 

trap line; from Oct. 1979 - June 1980, "moderate" ranged from means of 6-9 

crabs per trap line. 

From June 1979 - June 1980, "low" ranged from means of 1-4 crabs per trap 

line; from Oct. 1979 - June 1980, "low" ranged from means of 1-5 crabs per 

trap line, 

From June 1979 - June 1980, "zero1' equaled 0 crabs per trap line; from 

Oct. 1979 - June 1980, "zero" ranged from means of 0-1 crabs per trap line. 
Table 4. Stations with statistically similar numbers of juveniles 

settling on traps, based on simultaneous test procedure 

analysis of number of juvenile stone crabs per 5-trap line per 

month among stations. Kruskal-Wallis nonparametric analysis 

for significant differences among stations was highly 

significant (H=132.8*, 21 df). 

- - - - - - - - - - - - - 

Stations High Number Moderately low Few or no 

of Juveniles Number of Juveniles 

(35-46 per (4-10 per (0-3 per 

trap line) trap line) trap line) ........................................................................ 

Gulf of Mexico 

Outside Lostmans River 

Indian Key 

Pavilion Key 

Chatham Bend 

Shark Point 

Northwest Cape 

Lostmans River Channel 

Lostmans Second Bay 

Chokoloskee Bay 

Florida Bav 

Conchie Channel 

Sandy Key Channel 

Twin Key Basin 

Arsenicker Keys 

Captain Key 

Black Betsy Keys 

Tern Keys 

Blackwater Sound 

Biscayne Bay 

Pelican Bank 

Inside Sands Cut 

Billys Point 

Biscayne Reef 

Outside Sands Cut 

Sands Cut Reef 
Table 5. Trapping stations having statistically similar sex ratios (as 

determined by simultaneous test procedure) in the Gulf of 

Mexico, west Florida Bay, and Biscayne National Park (all 

stations summed) tested for goodness of fit to 1:l sex ratio 

(ma1e:female) by G-test (GH=38.28*, 13 df). (Note: The STP 

is a non-parametric rank analysis test, see note on Table 1). 

.............................................................. Station % male .............................................................. 

Stations with relatively Conchie Channel 95.5 

high proportion of males Biscayne National Park 92.8 

Arsenicker Keys 91.4 

Northwest Cape 88.8 

Shark Point 83.2 

Lostmans River Channel 80.0 

Stations with relatively Sandy Key Channel 78.0 

low proportion of males Twin Key Basin 70.7 

Chatham Bend 64.4 

Indian Key 61.0 

Captain Key 58.9 

Outside Lostmans River 51.3 

Pavilion Key 46.9 ............................................................. 
Table 6. Characteristics of station groups used for size class 

frequency analysis. Stations were grouped on basis of 

similarity in annual mean size, seasonal variations in mean 

size, and habitat at the station location. See Table 1 for 

station names. 

........................................................................ 

Station Group Group Characteristics ........................................................................ 

Offshore Gulf of Mexico 

Males (INK, PVK, LMO) 

Females (INK, PVK, LMC) 

Nearshore Gulf of Mexico 

Males (C'TB, SP'T) 

Females (CTb, LMI, SPT) 

Florida Bay 

No significant difference in mean 

size. 

Located offshore in Gulf of Mexico; 

same habitat characteristics. 

No significant difference in mean 

size. 

Located offshore in Gulf of Mexico; 

same habitat characteristics. 

Same seasonal trends in variation in 

mean size. 

No significant difference in mean 

size. 

Located on Gulf of Mexico at mouth of 

fresh water outflow; same habitat 

characteristics. 

No significant difference in mean 

size. 

Located in Gulf of Mexico at mouth of 

fresh water outflow. 

Some similarity in seasonal variation 

in mean size. 

Males (CCH, SKC, TKB, ASK, No significant difference in mean 

CPK, BBK, TNK, BWS) size. 

Located in Florida Bay; some similar 

habitat characteristics. 
Table 6 continued. 

........................................................................ 

Station Group Group Characteristics ........................................................................ 

Females (SKC, ASK, TKB, CPK, No significant differences in mean 

BBK, TNK, BWS) size. 

Located in Florida Bay; some similar 

habitat characteristics. 

No seasonal trends in variation in 

mean size seen at any station. 

Few female crabs at each station. 

Biscavne National Park 

Males (PLB, BLP, SCI, 

SCO, SCR) 

No significant differences in mean 

size. 

Located on the Atlantic Ocean; 

geographically separated from gulf 

stations. 
Table 7. Growth of male and female stone crabs (mm carapace width, CW) 

from capture of molting crabs and their exuvia during this - 

study. Females are divided into 10 nun size classes. Males 

are individually listed. Standard deviation in parentheses. 

Sex & Size Number Change in CW % Increase 

(mm) (mm) in CW 

Males 

79.0 

81.4 

90.2 

91.8 

Females 

50-60 

60-70 

70-80 

80-90 

90-;100 

Average: 10.1 (2.2) 15.0 (4.2) 
Table 8. Estimation of instantaneous mortality coefficient (2) and total annual mortality rate (~~'~~e-2~) for male and female 

stone crabs from Everglades National Park, using the average 

annual grown increment method of Hancock (1965). 

Sex Size Group N Z e-zt Total Annual 

(m CW) Mortality ........................................................................ 

Male 102-117.9 35 7 0.76 0.468 54.3% 

118-133.9 181 1.47 0.230 77.0% 

Female 94-103.9 8 7 0.35 0.704 29.6% 

104-113.9 4 1 0.70 0.498 50.2% 
Table 9. Estimation of stone crab mortality rate in Everglades National 

Park, using proportion of stone crabs lost from the population 

within annual molt increments (calculated from percent lost or 

gained between adjacent 2 mm carapace width size class intervals). 

........................................................................ 

Sex Size Interval N % Lost Sex Size Interval N % Lost 

Ma 1 e 102-103.9 62 Female 94-95.9 22 

104-105.3 54 13 96-97.9 18 18 

106-107.9 48 10 98-99.9 17 5 

108-109.9 4 6 3 100-101.9 14 14 

110-111.9 4 8 - 3 102-103.9 16 9 

112-113.9 3 7 18 

114-115.9 33 6 Total: 28% 

116-117.9 11 29 - 

Total: 582 

Elale 118-119.9 3 4 Female 104-105.9 11 

120-121.9 3 1 9 106-107.9 10 9 

122-123.9 2 6 15 108-109.9 3 64 

124-125.9 2 0 18 110-111.9 12 -8 1 

126-127..9 2 7 -20 112-113.9 5 - 6 3 

128-129.9 24 9 

130-131.9 14 3 2 Total: 5 5% 

132-133.9 6 2 0 

Total: 83% 
Table 10. Proportion of females that were found to be in gravid condition by 

area of capture within Everglades National Park. 

Area Number Percent Percent Number Percent 

Females Total of Gravid Gravid Total 

Captured Females Gravid 

Captured Females ............................................................................... 

Gulf of Mexico 394 83.8 16.8 6 6 80.7 

Western Florida 

Bay 67 14.3 

Northeast 

Florida Bay 9 1.9 66.7 6 7.2 
Table 11. Size of gravid females in relation to that of all females 

captured by area within Everglades National Park. 

........................................................................ 

Area Class Mean Size SD Range N ........................................................................ 

Gulf of Mexico gravid 89.5*** (12.9) 48.4-112.4 6 6 

all 80.9 (19.3) 33.4-116.3 394 

Florida Bay gravid 107.3* (12.0) 83.1-123.9 17 

all 99.4 (14.4) 76.7-126.2 5 8 

*Significantly larger than all (p less than .05). 

***Significantly larger than all (p less than .001). 
Table 12. Growth of male stone crabs (from an unpublished capture - 

recapture study conducted in Everglades National Park from 

March 1978 to March 1979). Standard deviation in 

parentheses. 

Premolt Size N Weeks at Mean Change Mean Percent 

Range (nun CW) Large In Size (mm CWj Increase in Size 

Total (all crabs): 19.2 (7.2) 20.9 (10.3) 
FLORIDA 

? 

I CCH FLO"O, bar bgm,, ! \ SKC 

, . '\ ASK,,,' ' '\Z, , 

. 1. 

Figure la. Location of sampling stations in Everglades National Park. See 

Table 1 for names of stations. 
Figure lb. Location of sampling stations in Biscayne National Park. See 

Table 1 for names of stations. 
CHOKOLOSKEE MY 

L - - - - - - - -r=o I 

INDIAN KEY 

T PAVILION KLY 

CHATHAM BEND 

8 

4 

8 C ouTsloE LOTSTMAN'S RIVER 

8 I- WSTMAN'S RIVER CHANNEL 

SHARK POINT 

n 

NORTHWEST CAPE 

8 I- SANDY KEY CHANNEL 

MONTH 

ARSENICKER KEYS 

- - 

8 I TWIN KEY BASIN 

CAPTAIN KEY 

- 

at BLACK BETSY KEYS 

TERN KEYS 

4 

2 

PELICAN BANK 

BILLY'S POINT 

INSIDE SANDS CUT 

T 

OUTSIDE SANDS CUT 

- -i=oo J AS 0 NDD/JJ F MAM J 

MONTH 

Figure 2. Mean number of stone crabs captured per trap in monthly samples 

by station. Hars and lines sl~ow standard deviation and range, 

respectively. No crabs were ever captured at station LSB. 
\ INDIAN KEY LOSTMAN'S RIVER 

CHANNEL 

PAVILION KEY SHARK POINT 

OUTSIDE LOSTMAN'S 20 NORTHWEST CAPE 

CHATHAM BEND 

10 

CONCHlE CHANNEL 

0 

79J A S ON DD/JJ FM AM J80 79J A S 0 N D D/J J F M A M J80 

MONTH MONTH 

Figure 3. Number of juvenile stone crabs found on adult stone crab traps, by month. 

Each data point represents number of juveniles per 5-trap line. NOTE: change of 

scale in graphs in last four stations. 
50~ I 

I I I I I I I I I I I I 

J ASONDDIJJ FMAM J 

MONTH 

Figure 4. Proportion of total catch comprised of male stone crabs, by month, for the 

Gulf of Mexico and western Florida Bay. Statistical differences in sex ratio 

(ma1e:female) among months were established by G-test (GH=76.56**,12 df). 

Statistically similar groups of months (illustrated) were determined by simultaneous 

test procedure. N=total number of crabs captured each sampling interval. 
EVERGLADES NATIONAL PARK 

125- 

- I00 - 

KNTVMMPWCKSKPBNWLLCCC 

8KBKIOTCHCKBKKKSlBPI OR 

EVERGLADES NATIONAL PARK I BISCAYNE NAT'L PARK 

Figure 5. Mean size (and standard {eviation) of male and female stone 

crabs for each station at which crdbs were captured. Statistically 

similar stations, as determined by analysis of variance and 

Student-Neuman-Kuel rank analysis, are illustrated. 
I2Or Femole N= 78. Mole N.132 - - - - - 

I00 - 

80 - 

60 - 

40 INDIAN KEY 

I20r Fernole N = 92, Male N =80 Males: F(11,66,=2.35' 

120 Femole N = 69. Male N = 124 

- 

5 I00 

- 80 W 

N 

CJ-I 60 I 

I2Or Femole N= 96. Mole N =99 

120r Mole N =53 n(n = 1) 

/ LO~TMAN'S RIVER CHANNEL 

4011'1~11~~ 11 

79J A S 0 N DD/J J F M A M J80 

MONTH 

Male N = 131 

60 

SHARK POINT 1 

40 

140 Male N= 93 r T 

40 NORTHWEST CAPE 

60 - 

CONCHIE CHANNEL 

40 

, "OF MO" N = 64 

140 -r T 

80 - 

60 SANDY .KEY ,CHANNEL , 8 n , j , 

79J A S 0 N D D/J J F M A M JBO 

MONTH 

Figure 6. Mean size (mm carapace width and standard deviation) of inale (solid lines) and 

female (dashed lines) stone crabs at individual stations over tirne. Only those statiohs with 

sufficient numbers of crabs of either sex were included. F values are given for stations 

shown by analysis of variance to be significantly difEerent in mean size of one or both sexes 

over time. 
MALES 

OFFSHORE GULF OF MEXICO 

Jul 

4 - 

Oct 

N = ll 

SlZE CLASS (mm CW) 

Jan 

SlZE CLASS (mm CW) 

MALES 

NEARSHORE GULF OF MEXICO 

Mar 

N=IO 

Feb 

N-7 

Jun 

N.21 

SIZE CLASS (mm CW I SIZE CLASS lmm CW I 

Figure 7. Ten millimeter size class frequencies (carapace width) of stone crabs 

by month. Stations were grouped according to criteria discussed in the text. 

Station groups, and characteristics of each group, are listed in Table 6. 

Station groups with insufficient numbers of crabs of one or both sexes are no$ 

shown. 
MALES 

SlZE CLASS lmm CWI 

1 Jul 

N=24 

8 - N ='12 

V) W 

J 4- a 

I 

W Oct 

0 N=8 

8 

m 

N.18 

4 

88 Dec N= 16 

FLOR~~A BY 

d r Jan 

I Jun 

SlZE CLASS Imm CW 1 

FEMALES 

OFFSHORE GULF OF MEXICO 

Mar 

N= 18 

8 - Jun 

N=29 4 - 

l.,, 0 

~~000~40'D~?40;,, , 

R4,,,$?20O 2 0 moSgS?$ 0 ' 

SIZE CLASS lmm CW) SIZE CLASS (mm CW) 

Figure 7 continued. 

6 6 

n al H G 

.A . dd 0 

al $4 

a al al 

OC N 

ZBW c> C 

oual 

.r( c a 

malo 

rn Ed 

a,aw 

Li Li 

MU (d 

a, c 

d .A G 

u . C .4 

mu 3 

3 

aloal LiLic 

3 bO.4 

M 4 

-4 c 

h 0 
MALES N.1041 

FEMALES N = 483 

Figure 10. Number of crabs per 2 mm size increment captured in nearshore 

southwest Florida in this study (Gulf of Mexico and Florida Bay). One 

hundred percent retention size increments used in calculation of mortality 

coefficients are shown. 
Llou 

3u aar o 

MA 0 a, u .d 3 Ll rn ~rru a- II 
SIZE OF MALE STONE CRABS (mm CW) 

Figure 12. Correlation between size of male and female stone crabs composing :I 

mated pair. 

S 
CARAPACE WIDTH CW (mm) 

CARAPACE WIDTH CW (mm) 

Figure 13. Size of 50% maturity of male stone crabs, according to the method of 

Somerton (1980). Figure A represents the regression line of adult and juvenile 

male crabs, as determined by non-heirarchial cluster analysis. The size of 50% 

maturity (Figure B) is estimated by using non-linear regression to fit a 

logistic function to percent maturity and size estimates. Only males with 

unregenerated (original) right crusher claws were used in the analysis. 
id' c 

E 2 

PERCENT OF FEMALES CARRING EGGS 
LEGEND 

....... SPAWNING 

..!;;.;,':: M AT 1 N G El MOLTING 

AGE CLASS 

Figure 15. Proportion of females molting, mating, and spawning, by age class 

(number in specified state/total number within age class), in Everglades 

National Park. Age classes are defined in the text. No females considered to 

be less than one year of age (less than LO mm CW) were collected in any of 

these three character states. N = total n~lmber of females in each age class. 
SUMMER 

LEGEND 

SPAWNING 

MOLTING 

<3 3>3 

FALL 

<3 3>3 <3 3>3 

WINTER . SPRING 

AGE CATEGORY (YRS) SEASON 

Figure 16. Seasonal variation in proportion of females in three age categories 

found molting, mating, and spawning in Everglades National Park. N = total 

number of females captured in each age category. The seasons are defined as 

follows: summer--July-hug; fall--Sept.-Nov.; winter--Dec.-Feb.; 

spring--Mar.-June. 
JFMAMJ JASONDDIJ 

MONTH 

Biscayne Bay (Noe 1967) 

Biscayne Bay (Cheung 1969) 

- Ceder Keys (Bender 1971 ) 

-.-. Southwest Florida, Gulf of Mexico (Sullivan 1979) 

. . . . . . . . Southwest Florida, Everglades National Park ( This Study) 

Figure 17. Composite of percent of total trapped female stone crabs with eggs, 

by month, from all studies conducted in Florida. 
PREMOLT CARAPACE WIDTH (mm) 

Figure 18. Regression of growth increment on premolt carapace width in male stone crabs 

greater than 70 mm carapace width. Dots represent capture-recapture data from an unpublished 

study conducted by Everglades National Park personnel in western Florida Bay from March 1978 

to March 1979. X's represent data from crhbs captured while molting during this study. The 

regression line generated is not significantly different from a line with a slope of zero 

(P1.86, 60df). The starred point deviates significantly (t-3.56, 60 df; p less than .001) 

from the line and may represent a crab that molted twice while at large. (This crab was at 

large longer than all other crabs.) Crabs less than 70 mm carapace width were omitted from 

calculation of the regression equation due to obvious differences in growth increment.