Captive breeding behavior of four strombidae conch.

ABSTRACT The feasibility of a captive breeding program was examined for the protected fisheries species Strombus gigas (queen conch) and three nonprotected Caribbean Strombus conch species: S. raninus (hawk-wing conch), S. alatus (Florida fighting conch), and S. costatus (milk conch). A total of 24 adult conch were collected from the Florida Keys: five S. costatus (three females, two males), seven S. raninus (five females, two males), eight S. alatus (four females, four males), and four S. gigas (one female, three males). The conch were placed in a 4.5-m dia circular tank that was divided into four equal quadrants (4.1 [m.sup.2]). The conch were fed a prepared gelatin diet made of Mazuri[R] Koi chow blended with Ulva sp. Egg masses collected from the breeding tank were measured for size, number of eggs, and diameter of egg capsule and strand. In the 40-week study, 426 egg masses were collected, and egg laying activity appeared to be related to water temperature. A total of 341 egg masses were collected from the five S. raninus females. The four S. alatus females laid 58 egg masses, the three S. costatus females laid a total of 23 egg masses, and the single S. gigas female laid four egg masses. The viability of egg masses from all four species was confirmed by successfully hatching and culturing the larvae to the juvenile stage. All species except S. gigas laid egg masses while copulating. Mate preferences and guarding behavior was observed. The captive breeding of these species holds promise for the establishment of a commercial captive breeding program, and may provide alternative conch species for the food and aquarium market.

KEY WORDS: conch, culture, larvae, reproduction, spawning, Strombus

INTRODUCTION

Six Strombus species (1) inhabit the shallow coastal waters of Florida and the Caribbean region: Strombus gigas Linnaeus (queen conch), S. costatus Gmelin (milk conch), S. raninus Gmelin (hawk-wing conch), S. alatus Gmelin (Florida fighting conch), S. pugilis Linnaeus (West Indian fighting conch), and S. gallus Linnaeus (rooster-tail conch; Abbott 1974). Of these species, S. gigas holds the highest commercial value as a subsistence and commercial fisheries product (Berg 1976, Brownell 1977, Appeldoorn 1994). S. costatus is also a highly valued fisheries species in Mexico (Aldana-Aranda et al. 1989).

Overfishing and the decline of the S. gigas fishery began in the 1970s and led to the enactment of several regulations and management strategies to protect conch populations (Appeldoorn 1994). A statewide moratorium on queen conch harvesting in Florida began in 1986 (Florida Administration Code, Chapter 68B-16.005), and in 1992, S. gigas was added to Appendix 2 of the Convention for the International Trade of Endangered Species (CITES) legal mandate. Countries that export queen conch must possess a CITES permit, which helps to ensure that harvest rates remain low enough to maintain a viable fisheries population. In addition to employing management strategies to protect wild populations, culturing queen conch for stock enhancement and commercial markets will also offset fisheries pressure (Creswell 1994, Davis and Shawl (2004a).

Florida and Caribbean Strombus species breed in shallow waters in seagrass beds or sandy habitats (Robertson 1959, Berg 1975, Brownell 1977, Bradshaw-Hawkins 1982, Davis et al. 1984). The reproductive season is typically during the summer months; however, some species have been observed to lay eggs year-round in certain locations (Robertson 1959, Brownell 1977, Bradshaw-Hawkins 1982). Depending on the species, the sand-covered, crescent-shaped egg mass contains between 92,000 and 400,000 eggs (Robertson 1959, Randall 1964, D'Asaro 1986, Davis et al. 1993).

Commercial and research facilities that culture juvenile queen conch depend upon field collected egg masses (Davis 2000a). In some locations, it is difficult to find egg masses in the wild due to limited spawning aggregations. Establishing a captive breeding program for S. gigas and other Strombus species would alleviate the need to collect egg masses front the wild and may possibly extend the 6-month breeding season to year-round (Davis et al. 1984). Captive breeding and egg-laying has been observed for some Strombus conch species. The reproductive behavior and larval cycles of wild and captive S. pugilis have been described (Bradshaw-Hawkins 1982); captive laid egg masses from S. raninus broodstock were used to record shell morphology and larval development (Davis et al. 1993); and the reproductive behavior and anatomy of captive S. raninus, S. gallus, S, costatus, S. alatus, and S. pugilis were observed (Reed 1995a, 1995b). S. gigas have been observed to copulate in captivity (Davis, personal observation); however, there are no reports regarding egg mass laying in captivity.

Based on the available reproductive data, it is hypothesized that adult S. gigas and other Strombus species can reliably lay egg masses in captivity. Therefore, the goal of this study was to determine the feasibility of establishing a captive breeding program for Strombus species. To address this goal, the first objective of this study was to observe and describe the spawning activity of the protected fisheries species S. gigas and three nonprotected Strombus species: S. raninus, S. alatus, and S. costatus in a breeding tank. The second objective was to confirm the viability of the captive laid eggs by culturing the larvae to the juvenile stage. The results from this study will assist in developing a year-round culture program, alleviating the field collection of egg masses, and establishing alternative species for the Strombus markets.

MATERIALS AND METHODS

The captive breeding study was conducted at Harbor Branch Oceanographic Institution (Harbor Branch), Aquaculture Division in Ft. Pierce, Florida. Egg masses were collected for 40 weeks (June 15, 2000, to March 22, 2001), and breeding behavior observations were made daily during the first 7 weeks of the study (June 15 to August 2, 2000). Larvae hatched from the egg masses laid in captivity were cultured throughout the study period.

The number of conch collected for this study was based on the availability of the conch at the collection sites. Seven adult S. raninus (two males and five females) and four S. alatus (three males and one female) were collected from three sites off Plantation Key in the Upper Florida Keys on June 15, 2000. On July 12, 2000, four additional S. alatus (one male and three females) were collected from the same location (Table 1). Five S. costatus (two males and three females) were collected on June 1, 2000, from the Ligumiuti Channel in Indian Key in the Upper Florida Keys and were placed in recirculating holding tanks in the Florida Keys for 2 weeks prior to the beginning of the study. Four hatchery-reared S. gigas (three males and one female) were obtained on July 12, 2000, from the Florida Fish and Wildlife Conservation Commission laboratory in Marathon, FL.

The sex of each conch was determined by positioning them on their side and observing a verge or an egg groove when it righted itself (Davis et al. 1984; Fig. 1). A small area on the dorsal side of the shell was then scrubbed clean with sandpaper and the conch were numbered with fluorescent paint (teal for males and orange for females), which was sealed with clear epoxy glue. The conch were transported in a cooler with seawater moistened towels during the four hour drive to Harbor Branch. Before being placed into the breeding tank at Harbor Branch, all of the conch were weighed to the nearest 0.1 g, and their shell lengths (SL) were measured with calipers (mm: Table 2).

[FIGURE 1 OMITTED]

The 11,500-L breeding tank (4.5 m dia x 0.7 m depth) was on a recirculating culture system (Fig. 2). The initial and replenishment water (30 L/hr or 6.5%/d) for the system was pretreated water drawn from a shallow salt water well. For the study, the breeding tank was divided into four equal areas (4.1 [m.sup.2]) using 30-cm high polypropylene mesh (2.5-cm openings). The tank was equipped with a raised substrate comprised of approximately a 10-cm depth of sand supported 15 cm above the bottom of the tank. The crushed coral aragonite sand (1-3-mm dia) provided substrate for the broodstock to lay egg masses and served as the biofilter for the system. The water depth above the substrate was 45 cm. The recirculating water entered the tank both through angled spray bars above the water and substrate and underneath the substrate. The water filtered through the sand, drained through a center bottom drain, then flowed through a sand filter (Baker Hydro 363 kg) prior to returning to the breeding tank. The sand filter was backwashed every 2 weeks.

[FIGURE 2 OMITTED]

The conch were stocked at varying densities and sex ratios based on the availability of the adults round at the collection sites. S. raninus conch were held at 1.7 conch/10 [m.sup.2] at a 3:1 female: male ratio, S. alatus were stocked at 2.0 conch/10 [m.sup.2] at a 1:1 sex ratio, S. costatus were at 1.2 conch/10 [m.sup.2] at a 1:1 ratio, and S. gigas were held at 0.98 conch/10 [m.sup.2] at a 1:3 female:male sex ratio.

Temperature, salinity, and pH were recorded daily and ammonia was measured weekly using a HACH[R] Ammonia test kit (Model NI-SA). The breeding tank was located within a shaded greenhouse, and natural light was supplemented with artificial lighting (250 watts) for a 12-h cycle (8 am to 8 pm). In an attempt to extend the breeding season, the tank water was heated using a 4000-watt (Titanium Single Phase "L"-Shaped Bottom Heater) heater during the winter months (November 2000 to March 2001).

The conch were fed a diet of Mazuri[R] Koi pellets, which were blended with dry Ulva sp. (sea lettuce), gelatin, and seawater to create a gelatin based benthic diet (R. LeRoy Creswell, personal communication 2000). The recipe was composed of 36% Mazuri Koi pellets, 16% Ulva sp., 42% seawater, and 5% gelatin. The gelatin allowed the food to remain stable for approximately 48 h. The conch were fed to satiation once per day. On average, a total of 745-925 g of gel food was fed once daily, with approximately 145 g per day fed to all the S. raninus conch, 150 g fed to the S. alatus conch, 300 g fed to S. costatus, and 240 g fed to the S. gigas conch.

Egg mass production was recorded daily. During the first seven weeks, copulatory behavior observations were made approximately five times per 24 h. Each observation spanned 15 min to one hour and included periodic night observations. The number of copulations, mate preferences, and any territorial male behavior were recorded. When an egg mass was found, it was removed with a net or by hand and placed onto a wet table for length, width and height measurements. Several egg masses were uncoiled to estimate the total length of the egg strand (n = 13 for S. raninus, n = 10 for S. alatus, and n = 10 for S. costatus). None of the S. gigas egg masses were uncoiled because of the limited number of masses and the need for eggs for larval production. Measurements of egg strand diameter (n = 5 per egg mass), egg capsule diameter (n = 5 per egg mass), and the number of eggs per millimeter (n = 3 per egg mass) were recorded using a compound microscope (40X) equipped with an eyepiece micrometer. A total of 71 egg masses were used for this data collection; 40 for S. raninus, 20 for S. alatus, nine for S. costatus, and two for S. gigas.

Larvae of S. raninus (two egg masses), S. alatus (six egg masses), and S. costatus (one egg mass) were hatched from captive laid egg masses. The larvae were cultured at 20-50 veligers/L in two to three 5-L containers using established techniques (Davis 2000b). The culture water was 5-[micro]m filtered, UV-treated, and changed daily. The cultures were not aerated, and temperature was controlled by placing the containers in a water bath. Depending on age, the veligers were fed 3,000-20,000 cells/mL of culture water of Tahitian Isochrysis daily.

One S. gigas egg mass was cultured in a 420-L conical tank (Davis and Shawl, in press). The culture water was 5-[micro]m filtered and UV treated. An airlift provided circulation in the tank, and the water was changed every other day. The larvae were fed 5,000-25,000 cells/ml of culture water of Isochrysis, and starting on day 15, Chaetocerous gracilis or Chaetocerous muelleri was also added to the tank at a concentration of 3,000 cells/mL of culture water.

Metamorphosis was induced for all four species using diluted 3% hydrogen peroxide (Boettcher et al. 1997) or Laurencia poitei seaweed extract (Davis et al. 1987). A total of 529 larvae were tested; 305 larvae were induced with hydrogen peroxide, and 224 were induced with Laurencia extract. The SL of the newly hatched veliger ([micro]m), the number of days until metamorphosis, and the veliger SL at metamorphosis ([micro]m) was recorded along with the metamorphic success using the two inducers.

RESULTS

From June 15, 2000, to March 22, 2001 (40 weeks), a total of 426 egg masses were collected from the breeding tank. The five S. raninus females had the highest productivity with 341 masses, the four S. alatus females laid 58 masses, 23 egg masses were collected from the three S. costatus, and the single S. gigas female laid 4 egg masses. The weekly fecundity of each individual female conch was averaged. The number of egg masses per female per week per species was plotted and compared with average weekly temperature data (Fig. 3). In general, egg mass production was continuous during the warmer months, (26 - 29[degrees]C) June to September (Fig. 3). In the winter months, October to January, egg mass production slowed down or stopped when the temperature decreased (22-25[degrees]C). Egg mass laying began again in February 2001 when the temperature increased (25-29[degrees]C). By heating the breeding tank water from November 2000 to March 2001, the temperature remained 1 - 4[degrees]C above ambient water temperature (Fig. 3). This appeared to stimulate egg laying in the winter months (February to March 2001), as no other parameters were changed. Salinity, pH, ammonia, and nitrite remained relatively constant throughout the study (Table 3).

[FIGURE 3 OMITTED]

The weekly number of egg masses laid per species per week was standardized for each 10-week period of the 40-week study (Table 4). S. raninus females were the only specie to lay egg masses throughout the four 10-week sample periods, with a maximum of seven egg masses collected from one female per week. The maximum number of egg masses laid from one female per week from S. alatus and S. costatus was five and three, respectively. The single S. gigas female did not lay an egg mass until February 2001. One egg mass was collected each week during weeks 35, 36, 38, and 39.

Egg mass characteristics of the eggs laid by the captive adults were similar to those of egg masses laid in the wild (Table 5). S. raninus egg masses were long and narrow and consisted of a very thin and fragile egg strand (351 [+ or -] 24 [micro]m dia). The S. alatus egg masses were shorter and wider than S. raninus and the egg strand was slightly larger in diameter (509 [+ or -] 41 [micro]m). S. costatus and S. gigas produced the largest egg masses with the thickest egg strands (825 [+ or -] 56 [micro]m and 798 [+ or -] 18 [micro]m, respectively). The S. raninus and S. alatus egg masses contained an estimated 76,000-250,00 eggs per mass, whereas the S. costatus egg masses held up to an estimated 440,000 eggs. The egg capsule diameter and number of eggs per mm appeared to be related to the size of the egg strand diameter. S. raninus egg capsules were small, therefore, each mm of egg strand contained approximately twice as many eggs as the other three species (Table 5). Females from all three species were observed to copulate consecutively with more than one male while laying the same egg mass.

From June 16 to August 2, 2000, the first 7 weeks of the study, copulatory frequency and reproductive behavior was observed for S. raninus, S. alatus, and S. costatus. The number of observed copulations was compared with the number of egg masses collected during that time period (Fig. 4). For S. raninus, the number of egg masses collected from the female conch was higher than the number of copulations observed. However, for S. alatus and S. costatus there were less egg masses collected compared with the number of copulations observed. All three species were observed copulating while laying an egg mass (Fig. 5). S. alatus were observed to display this behavior more frequently (52%), compared with S. raninus (31%) and S. costatus (19%; Fig. 5).

[FIGURE 5 OMITTED]

Several conch showed preferences for particular mates (Fig. 6). Using the males as examples, S. raninus male 1 showed no preference; he mated approximately an equal amount of the time with each of the five females. In contrast, S. raninus male 2 demonstrated a mating preference towards females 2 and 3. S. alatus male 1 showed a preference towards females 1 and 3, and make 2 showed preference towards females 3 and 4. S. alatus male 3 showed no preference and mated with all four females, whereas male 4 only mated with female 3. S. costatus male 1 copulated with all three females with approximately the same frequency; whereas, male 2 showed a preference towards female 2.

Conch were observed to copulate from 5 minutes to 2 h. The males would approach the females with their proboscis to initiate au interaction. Several times the females would leap away from the male, rejecting copulation. During other observations the males would follow the females around the perimeter of the enclosure before copulation was successful. There appeared to be no trend in mating pairs based on the size of the copulating female or male.

The S. alatus male conch in the breeding tank demonstrated protective courting behaviors. On several occasions, two males would prop themselves halfway on the lip of an egg-laying female. Only one of the males mated with the female while the other male appeared to be "guarding" the female. Behavior similar to this was observed in S. pugilus (Bradshaw-Hawkins 1982). The guarding male almost always had their siphonal canal positioned 90[degrees] to and on top of the female's dorsal side. During one observation, an egg-laying female had three aggressive males around her. One of the males guarding her used his proboscis in an attempt to dislodge the male that was mating with her. When the guarding male was unable to remove the mating male, he proceeded to use his proboscis to "spar" with that male. After a few minutes, the males stopped and the guarding male attempted to move back into his position. However, as the two males were sparring over top of the female, another male moved in. The third male was immediately chased away by the guard male. The guarding male then attempted to dislodge the mating partner once again, but was unsuccessful and copulation continued. The S. alatus broodstock were initially stocked at a 1:1 sex ratio. A few weeks into the study, the ratio in the breeding tank was increased to 1:2.5 female: male. Once male guarding and sparring were observed, some of the males were removed to decrease the sex ratio back to 1:1 to reduce stress on the egg-laying females.

All four captive species laid viable eggs in captivity. S. alatus, S. costatus, and S. gigas larvae were competent for metamorphosis in 18-24 days, and S. raninus were competent in 48 days (Table 6). When S. alatus larvae were exposed to the hydrogen peroxide inducer, 69.3% [+ or -] 17.2 of the larvae metamorphosed, which was similar to larvae exposed to the Laurencia inducer (62.5% [+ or -] 10.8). The S. costatus larvae showed a low metamorphic success rate with hydrogen peroxide (31% [+ or -] 14.1) and an even lower rate with Laurencia (0.7% [+ or -] 1). However, the larvae that did not undergo metamorphosis with the Laurencia extract were reinduced three days later with hydrogen peroxide and 78% of these larvae completed metamorphosis. S. gigas larvae were only induced with hydrogen peroxide and demonstrated a metamorphic success rate of 69%. S. raninus larvae did not have a very high metamorphic success rate with either of the inducers (< 7%).

Veliger shell length ([micro]m) at hatch and at metamorphosis is shown in comparison with other laboratory cultured Strombus veligers (Table 6). S. raninus' veligers hatched at the smallest size (205 [+ or -] 10.5 [micro]m) and S. costatus veligers had the largest SL at hatch (370 [+ or -] 10.5 [micro]m). The S. gigas larvae hatched at a much smaller SL than previously observed (Davis et al. 1993). The two smaller Strombus species, S. raninus and S. alatus veligers, had the largest SL at metamorphosis (1438 [+ or -] 72.2 [micro]m and 1539 [+ or -] 186 [micro]m, respectively), although S. alatus larvae were competent for metamorphosis in nearly half as many days. In contrast, previous studies have reported a much larger S. costatus veliger at the time of metamorphosis (Brownell 1977; Table 6).

DISCUSSION

Culturing conch in captivity can reduce the harvest pressure that is evident in the fishery (Berg 1976, Brownell 1977, Creswell 1994). All four conch species used in this study spawned in captivity in a recirculating tank system. This significant breakthrough means that the culturing cycle for S. gigas, S. raninus, S. alatus, and S. costatus can be closed. Potential conch farms may no longer need to rely upon wild reproductively active adult conch populations for egg masses. Raising conch in a recirculating system minimizes effluent discharge and also suggests that future conch aquaculture sites may not need to be located near seawater sources.

The success of spawning conch in captivity was caused by several factors. The conch were provided with a stable breeding site that was devoid of predators, had optimal water quality conditions, a consistent supply of food, and a sand substrate. Temperature also appeared to regulate spawning activity. In wild adult populations, increasing temperatures throughout the summer months along with a 12-h photoperiod characterizes the reproductive season for S. gigas (Stoner et al. 1992). When temperature was increased artificially in early February 2001, all tour species began to lay eggs again. This is typically two months sooner than spawning occurs in the wild (Davis et al. 1984). In this study, the male and female conch had been artificially aggregated, which increased the potential for mating. Wild Strombus adult populations are usually found at a sex ratio of 1:1. The five S. raninus adults produced the majority of the egg masses with only two males. This may suggest that a breeding tank can be stocked with a higher female sex ratio while still maintaining an appropriate stocking density within the breeding tank.

The Strombus larvae hatched from the egg masses spawned in captivity were viable. Larvae from all four species became metamorphically competent and the hydrogen peroxide inducer yielded the highest percent metamorphosis. It appears that the S. gigas larvae hatched at a smaller size than previously reported, which could be a result of eggs laid in an artificial habitat. S. raninus females were the most prolific egg layers of the four species; however, the larval cycle was twice as long as the other species. S. alatus larvae had the shortest larval cycle and the highest tolerance for temperature and salinity changes.

This study has demonstrated the feasibility of establishing a captive breeding program for Strombus species. Due to the success of this study, an expanded captive breeding area and conch hatchery was developed and is in operation at Harbor Branch to culture S. alatus at a commercial scale (Davis and Shawl, 2004b), and S. gigas for conservation research.

To ensure reliable egg mass production in captivity, research must to be conducted on photoperiod, temperature, density, nutrition, and sex ratio. Determining these parameters and cultivating alternative Strombus species will assist in alleviating the need to collect egg masses from the wild, provide year round egg masses, and will ultimately relieve pressures on the S. gigas fishery.

TABLE 1.
Description of Upper Florida Keys collection sites
for Strombus species.

Site
No.        Location and Date       Depth (m)         Bottom Type

 1     Sea Oat Beach, Lower           1.5      Fine sand, Batophora,
       Matacumbe (June 15,                     Laurencia, Halimeda,
       2000                                    Thalassia,
                                               Springodium

 2     Windley Cay, Coral Club     0.16-1.5    Soft line sand, fine
       (June 15, 2000)                         diatom film,
                                               Syringodium,
                                               Halimeda

 3     Ligumuiti Channel,            2-2.5     Sandy, rocky hard
       Indian Key (a) (June 1,                 bottom
       2000)

 4     Florida Fish and Wildlife     0.75      Fiberglass holding tanks
       Conservation                            (0.75 m wide x 3.6 m
       Commission, Keys                        length)
       Marine Laboratory,
       Long Key, FL (b) (July
       16, 2000)

Site                                Water Temp    Salinity
No.        Location and Date       ([degrees]C)    (ppt)      pH

 1     Sea Oat Beach, Lower            29.7          36      8.2
       Matacumbe (June 15,
       2000

 2     Windley Cay, Coral Club         31.2          35      8.4
       (June 15, 2000)

 3     Ligumuiti Channel,              N/A          N/A      N/A
       Indian Key (a) (June 1,
       2000)

 4     Florida Fish and Wildlife      26-32         N/A      N/A
       Conservation
       Commission, Keys
       Marine Laboratory,
       Long Key, FL (b) (July
       16, 2000)

Site                               Ammonia
No.        Location and Date       (mg/L)      Species     Sex   No.

 1     Sea Oat Beach, Lower         0.06     S. raninus     M     1
       Matacumbe (June 15,
       2000

 2     Windley Cay, Coral Club      0.07     S. raninus     F     5
       (June 15, 2000)                       S. raninus     M     1
                                             S. alatus      F     1
                                             S. alatus      M     3

 3     Ligumuiti Channel,            N/A     S. costatus    F     3
       Indian Key (a) (June 1,               S. costatus    M     2
       2000)

 4     Florida Fish and Wildlife     N/A     S. gigas       F     1
       Conservation                          S. gigas       M     3
       Commission, Keys
       Marine Laboratory,
       Long Key, FL (b) (July
       16, 2000)

(a) S. costatus were collected and held in a recirculating system
for 2 weeks prior to being transported to HBOI.

(b) Hatchery reared from S. gigas eggs collected in Florida waters.

TABLE 2.
Shell length (SL) and weight of adult Strombus conch collected
from the Florida Keys.

  Species     Sex   No. of Conch   SL Range (mm)   Avg. SL (mm)

S. raninus     M         2           72.8-74.9         73.9
               F         5           77.0-86.4         82.8
S. alatus      M         4           76.0-92.7         86.7
               F         4           80.2-94.7         89
S. costatus    M         2            170-173         172
               F         3            165-195         180
S. gigas       M         3            180-190         183.3
               F         1            190             190

  Species     Sex   Weight Range (g)   Avg. Weight (g)

S. raninus     M         63-72              67.5
               F         67-102             85.8
S. alatus      M       51.1-95.4            70.2
               F       70.7-109.8           86.8
S. costatus    M        754-776              765
               F        965-1100            1030
S. gigas       M       1094-1560            1267
               F       1151                 1151

TABLE 3.
Water quality for the broodstock tank and the replenishment water

                                                       Replenishment
                                  Tank Water               Water
                           (June 2000 to March 2001)    (June 2000)

Temp ([degrees]C)           27.4 [+ or -] 2.11 (277)     28.3 (1)
Salinity (ppt)              33.5 [+ or -] 1.25 (555)       33 (1)
pH                           8.1 [+ or -] 0.28 (242)      7.7 (l)
Ammonia (mg/L)               0.1 [+ or -] 0.02 (39)      0.08 (1)
Nitrite                    0.009 [+ or -] 0.006 (6)         --
Ca+ ion Concentration
  (mg/L as CaC[O.sub.3])     429 [+ or -] 12.7 (2)        403 (1)
Dissolved oxygen                     6.2 (1)             4.09 (1)
ORP                                203.1 (1)              195 (1)

Results are expressed as average [+ or -] standard deviation
(n = samples). oxygen reduction potential

TABLE 4.
Weekly egg mass production during the 40-week study period,
standardized as egg masses per female per week.

Weeks       S. raninus           S. alatus

 1-10   3.25 [+ or -] 0.95   0.66 [+ or -] 0.57
               (7)                  (4)
11-20   2.21 [+ or -] 1.16   0.06 [+ or -] 0.10
               (6)                  (1)
21-30   0.10 [+ or -] 1.15           0
               (2)
31-40   0.08 [+ or -] 0.21   0.44 [+ or -] 0.43
               (3)                  (5)

Weeks      S. costatus            S. gigas

 1-10   0.30 [+ or -] 0.31           0
               (3)
11-20           0                    0

21-30   0.03 [+ or -] 0.08           0
               (1)
31-40   0.25 [+ or -] 0.31   0.67 [+ or -] 0.52
               (1)                  (1)

Results are expressed as average [+ or -] standard deviation. The
number in parentheses represents the maximum number of egg masses
collected from one female during a 1-week period.

TABLE 5.
Summary of egg mass data front the study (bold numbers)
compared to published data.

            Variable                       S. raninus

Length of egg mass (cm)                 8.4 [+ or -] 2.4 (315)#
                                          4-15.5 (315)#
                                          4-7 (4) (c)
Width of egg mass (cm)                 21.1 [+ or -] 0.5 (315)#
                                        1.1-3 (315)#
Length of uncoiled strand (m)             7 [+ or -] 2 (13)
                                        4.1-10 (13)#
                                           20 (1) (a)
No. eggs/mass (estimated)            91,000-250,000 (13)#
                                    206,000-245,000 (2) (c)
                                    400,000-460,000 (1) (a)
Diameter of egg strand ([micro]m)       351 [+ or -] 24 (40)#
                                        321 [+ or -] 20 (10) (c)
No. of egg capsules per mm             24.9 [+ or -] 3.1 (40)#
                                         20-23 (1) (a)
                                         21-25 (15) (c)
Egg capsule diameter ([micro]m)         123 [+ or -] 10 (40)#
                                        140 [+ or -] 4 (30) (a)

            Variable                       S. alatus

Length of egg mass (cm)                6.5 [+ or -] 1.3 (30)#
                                       4.5-9 (30)#
                                              --
Width of egg mass (cm)                 2.9 [+ or -] 0.6 (30)#
                                       1.5-4 (30)#
Length of uncoiled strand (m)         10.8 [+ or -] 1.4 (10)#
                                       7.1-11.9 (10)#
                                        10.7 (10) (b)
No. eggs/mass (estimated)           76,000-182,000 (10)#
                                        92,000 (2) (b)
Diameter of egg strand ([micro]m)      509 [+ or -] 41 (20)#
                                        600 (10) (b)
No. of egg capsules per mm            12.3 [+ or -] 1.2 (20)#
                                        8.6 (10) (b)
Egg capsule diameter ([micro]m)        181 [+ or -] 11 (20)#
                                        170 (10) (b)

            Variable                       S. costatus

Length of egg mass (cm)                  15 [+ or -] 7.1 (10)#
                                          9-21.5 (10)#
                                          6-10 (2) (c)
Width of egg mass (cm)                    4 [+ or -] 0.6 (10)#
                                        2.5-4 (10)#
Length of uncoiled strand (m)            19 [+ or -] 9.7 (9)#
                                        7.5-35.8 (9)#
                                       14.1 [+ or -] 1.3 (2) (a)
No. eggs/mass (estimated)            87,000-440,1100 (9)#
                                    185,000-210,000 (2) (a)
Diameter of egg strand ([micro]m)       825 [+ or -] 56 (9)#
                                        761 [+ or -] 18 (10) (c)
No. of egg capsules per mm               12 [+ or -] 1.4 (9)#
                                          14 (a) (a)
                                         12-14 (10) (c)
Egg capsule diameter ([micro]m)         250 [+ or -] 9 (9)#
                                        262 [+ or -] 6 (20) (c)

            Variable                        S. gigas

Length of egg mass (cm)                      9 (1)
                                               --
                                          8-15 (9) (c)
Width of egg mass (cm)                         --
                                               --
Length of uncoiled strand (m)                  --
                                               --
                                          22.6 (1) (a)
                                         24-37 (10) (d)
No. eggs/mass (estimated)                      --
                                    313,000-485,000 (10) (d)
                                    385,000-430,000 (1) (a)
Diameter of egg strand ([micro]m)       798 [+ or -] 18 (2)#
                                        785 [+ or -] 44 (10) (c)
No. of egg capsules per mm             13.4 [+ or -] 0.9 (2)#
                                         17-19 (1) (a)
                                         14-16 (10) (c)
                                         12-15 (10) (d)
Egg capsule diameter ([micro]m)         233 [+ or -] 11 (2)#
                                        225 [+ or -] 17 (20) (c)

Results are expressed as average [+ or- ] standard deviation
(n = samples) and ranges.

(a) Robertson (1959).

(b) D'Asaro (1986).

(c) Davis et al. (1993).

(d) Randall (1964).

Note: Summary of egg mass data from the study is indicated with #.

TABLE 6.
Summary of veliger and metamorphosis data from the study
(bold numbers) compared to published data.

               Variable                         S. raninus

Newly hatched veliger SL ([micro]m)       205 [+ or -] 10.5 (10)#
                                          197 [+ or -] 8 (20) (c)
No. of days to metamorphosis                      48 (1)#
                                                  40 (c)
Veliger SL at metamorphosis ([micro]m)   1438 [+ or -] 72.2 (4)#
                                         1450 [+ or -] 53 (10) (c)
Metamorphic success (%)
  Hydrogen peroxide                         5 [+ or -] 2.3 (2)#
  Laurencia                                      6.6 (1)#
  Reinduction with [H.sub.2][O.sub.2]               --
  Number of larvae per sample size                  30#

               Variable                         S. alatus

Newly hatched veliger SL ([micro]m)       298 [+ or -] 14.2 (10)#
                                                   --
No. of days to metamorphosis                     24 (1)#
                                                   --
Veliger SL at metamorphosis ([micro]m)   1539 [+ or -] 186 (55)
                                                   --
Metamorphic success (%)
  Hydrogen peroxide                      69.3 [+ or -] 17.2 (3)#
  Laurencia                              62.5 [+ or -] 10.8 (4)#
  Reinduction with [H.sub.2][O.sub.2]              --
  Number of larvae per sample size                 12#

               Variable                         S. costatus

Newly hatched veliger SL ([micro]m)       370 [+ or -] 10.5 (10)#
                                          388 [+ or -] 14 (20) (c)
No. of days to metamorphosis                      18 (1)#
                                                 15-18 (b)
                                                   32 (c)
Veliger SL at metamorphosis ([micro]m)   1306 [+ or -] 23.9 (23)#
                                               4000 (31) (b)
                                         1277 [+ or -] 101 (10) (c)
Metamorphic success (%)
  Hydrogen peroxide                        31 [+ or -] 14.1 (2)#
  Laurencia                               0.7 [+ or -] 1 (2)#
  Reinduction with [H.sub.2][O.sub.2]             78 (1)#
  Number of larvae per sample size            70, 76, and 111#

               Variable                          S. gigas

Newly hatched veliger SL ([micro]m)       221 [+ or -] 28.4 (20)#
                                          354 [+ or -] 15 (20) (c)
No. of days to metamorphosis                      18 (1)
                                                 18-21 (b)
                                                  21 (c)
Veliger SL at metamorphosis ([micro]m)   1281 [+ or -] 63 (10)#
                                               1240 (69) (a)
                                               2200 (37) (b)
                                         1170 [+ or -] 58 (10) (c)
Metamorphic success (%)
  Hydrogen peroxide                               68 (1)#
  Laurencia                                         --
  Reinduction with [H.sub.2][O.sub.2]               --
  Number of larvae per sample size                  69#

The results are expressed as average [+ or -] standard deviation
(n = samples).

(a) Berg (1976).

(b) Brownell (1977).

(c) Davis et al. (1993).

Note: Summary of veliger and metamorphosis data
from the study is indicated with #.

Figure 4. The total number if conch egg masses collected compared
with the number of copulations that were observed from June 15 to
August 2, 2000 (7 weeks).

Number of times observed

              Egg Masses   Copulations

S. raninus       144           74
S. alatus         26           31
S. costatus        5           16

Note: Table made from bar graph.

Figure 6. Male preferences towards female breeding
partners. Observations were recorded from June 15
to August 2, 2000 (7 weeks).

Female S. raninus

Male 1

1   24%
2   20%
3   18%
4   18%
5   20%

Note: Table made from pie chart.

Male 2

1   14%
2   38%
3   31%
4    3%
5   14%

Note: Table made from pie chart.

Female S. alatus

Male 1

1   36%
2    9%
3   46%
4    9%

Note: Table made from pie chart.

Male 2

3   33%
4   67%

Note: Table made from pie chart.

Male 3

1   25%
2   25%
3   17%
4   33%

Note: Table made from pie chart.

Male 4

3   100%

Note: Table made from pie chart.

Female S. costatus

Male 1

1   37%
2   38%
3   25%

Note: Table made from pie chart.

Male 2

2   75%
3   25%

Note: Table made from pie chart.

ACKNOWLEDGMENTS

The authors would like to thank the following individuals for their contributions to this study: Richard Greenfield, Jr., from CaribSea, Inc.; Buddy and Joe Pinder from the Keys Marine Conservancy; Robert Glazer from the Florida Fish and Wildlife Conservation Commission; and Jerry Corsaut, Tom Smoyer, Brian Cousin, Jackie Arosan, Tina Powell, and Riccardo Russo from Harbor Branch Oceanographic Institution, Inc. We would also like to thank John Scarpa, Ken Riley, Ashley Spring, and an anonymous reviewer for their editorial comments. This research was partially supported by The Link Foundation. This is a Harbor Branch contribution 1546.

* Correspondence: [e-mail]

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AMBER L. SHAWL AND MEGAN DAVIS

Harbor Branch Oceanographic Institution 5600 US 1 North, Ft. Pierce, Florida 34946