Aquaculture Sci. 56（3），359－368（2008）

Spawning Season, Lunar-related Spawning and Mating Systems in the Camouflage polyphekadion at Ishigaki Island, Japan

1, 2 3 4 Kazuhisa TERUYA , Shukei MASUMA , Yasushi HONDO 5, ＊ and Katsuyuki HAMASAKI

Abstract: We examined seasonal changes in the gonadosomatic index of wild fish and detailed the first spawning period of each year of cultured fish over several years to determine the spawning season and lunar-related spawning of camouflage grouper Epinephelus polyphekadion in a subtropical area of southern Japan. Additionally, we observed captive females’ and males’ spawning behavior and elucidated the mating system of this species. The main spawning season of wild fish was April－May of the solar calendar (Gregorian calendar), when gonadosomatic index (GSI) values of females and males peaked. The first spawning periods varied in the solar calendar. However, they were observed from the 19th to 23rd day in the third month of the lunar calendar (lunisolar calendar) during the full moon and the last quarter moon, excluding the years when spawning occurred one month later, because of low water temperatures before the spawning season in those years. This result indicates that camouflage grouper shows lunar-related spawning. The basic mating system of camouflage grouper is pair spawning between the largest dominant male and an ovulated female. However, some non-dominant males undertook sneaker spawning.

Key words: Camouflage grouper; Lunar-related spawning; Mating system; Spawning behavior

Camouflage grouper Epinephelus polypheka- remain underdeveloped (James et al. 1997). dion (Pisces, , ) inhabits Wild and captive camouflage grouper report- shallow waters of coral reefs in subtropical and edly show a lunar-related spawning cycle; they tropical waters from southern Japan to the Indo- for several days in each successive 2－ West Pacific region (Heemstra and Randall 3 month period during the reproductive season 1993). This species has been targeted for aqua- (James et al. 1997; Rhodes and Sadovy 2002). culture and stock enhancement in Asian and Studies of the reproductive biology of camou- Pacific countries because of its high commer- flage grouper have revealed a wide variation in cial value. The need exists to develop hatchery lunar periodicity and seasonal timing of spawn- technology for mass production of juveniles ing, i.e. both new-moon and full-moon spawn- (Tawada 1989a, b; Debas et al. 1989; Tamaru ing have been reported and spawning occurs et al. 1996; James et al. 1997, 1998). However, regionally in a specific season in the Indo- larval survival rates remain low and mass cul- Pacific region (Rhodes and Sadovy 2002). In ture techniques for larval camouflage grouper Japan, although Tawada (1989b) first reported

Received January 18, 2008: Accepted June 24, 2008. 1 Shibushi Station, National Center for Stock Enhancement, Fisheries Research Agency, Shibushi, Kagoshima 899-7101, Japan. 2 Stock Enhancement Technology Development Center, National Research Institute of Aquaculture, Fisheries Research Agency, Saiki, Oita 879-2602, Japan. 3 Miyazu Station, National Center for Stock Enhancement, Fisheries Research Agency, Miyazu, Kyoto 626-0052, Japan. 4 Goto Station, National Center for Stock Enhancement, Fisheries Research Agency, Goto, Nagasaki 853-0508, Japan. 5 Department of Marine Biosciences, Tokyo University of Marine Science and Technology, Tokyo 108-8477, Japan. ＊Corresponding author: [email protected] 360 K. Teruya, S. Masuma, Y. Hondo and K. Hamasaki hormone-induced spawning of captive camou- observation of spawning behavior is impor- flage grouper, the spawning biology of wild and tant to improve the broodstock management non-hormone treated camouflage grouper has techniques. Nevertheless, camouflage grou- not been reported. per spawning behavior has not been reported. For several fish species, larger eggs are Moreover, observing the spawning behavior known to produce larger larvae with a high would reveal the number of females and males tolerance for starvation (e.g., Sehgal and Toor involved in mating, i.e. mating system, which 1991; Imai and Tanaka 1998). Kayano et al. is expected to affect the genetic variability of (1998) reported that the diameter of eggs from the offspring strongly given a limited number captive red spotted grouper Epinephelus akaara of effective parents in captivity (Perez-Enriquez that were distributed in temperate waters were et al. 1999; Sekino et al. 2002; Hara and Sekino larger at low temperatures in the early phase 2003; Alarcón et al. 2004; Nugrohoa and of the spawning season. Larvae that hatched Taniguchi 2004). Growing concern surrounds from larger eggs survived longer than those the potential negative effects on wild popula- from smaller eggs spawned at higher tem- tions of stock enhancement programs’ release peratures later in the spawning season. This of hatchery-produced juveniles with low genetic phenomenon has also been observed for coral variation (e.g., Waples 1991; Utter 1998). trout leopardus distributed in sub- To determine the spawning season, lunar- tropical waters in Japan (Teruya et al. 1992). related spawning, timing of the first spawning The diameter of eggs spawned by captive cam- period during the spawning season, and mating ouflage grouper is reported as 830±30μm systems of the camouflage grouper in a subtrop- (mean±SD) at 25－30℃ (Tawada 1989b), 769 ical area of southern Japan, we: (1) examined －832μm at 27℃ (Tamaru et al. 1996) and the gonadosomatic index of wild fish; (2) deter- 757±37μm at 29－30℃ (James et al. 1997). mined the first spawning period of cultured fish Consequently, egg diameters of the camouflage in a tank; and (3) made preliminary observa- grouper tend to decrease with increasing water tions of captive females and males’ spawning temperatures at spawning. Therefore, for sub- behavior. tropical waters, it can be inferred that egg diam- eters are larger at the lower temperatures that Materials and Methods occur early in the spawning season. Prediction of the first spawning period during the spawn- Gonadosomatic index of wild fish ing season and the use of large eggs obtained Fish were collected by hook-and-line on six during this period would be advantageous for occasions during April－October 1986 and on 13 production of camouflage grouper juveniles. occasions during February－October 1987 off The egg fertilization rate is an index that is the coast of Ishigaki Island, Okinawa Prefecture, useful to evaluate egg quality in fish broodstock Japan (Fig. 1). Size, sex and gonad weight were management (e.g., Matsunari et al. 2006). Low determined for 29 fish in 1986 and 40 fish in fertilization rates of eggs for the red spotted 1987. Body weight (BW) and total length (TL) grouper, fluctuating between 10% and 25% for of captured individuals were measured respec- spontaneous spawning, have been a problem in tively to the nearest 10 g and 1 mm. Gonads the broodstock management (Okumura 1998). were removed and weighed to the nearest Okumura et al. (2002) investigated the reason 0.1 g after paper blotting. Sex was determined by for low fertilization rates in spawning tanks of examining a small piece of gonad under a light red spotted grouper by observing spawning microscope. To assess the spawning season, behavior and found that the low fertilization rate the gonadosomatic index (GSI) was calculated might be caused by limited space, especially for each fish using the formula, GSI＝(gonad insufficient water depth, which might have weight)/(gonad-free fish weight)×100. inhibited normal spawning behavior. Therefore, Spawning of the Camoufl age Grouper 361

Spawning of captive fish length and body weight of the fish in each year Broodstock fish were captured by hook-and- are presented in Table 1. line in the coral lagoons of Ishigaki Island in The fish were reared in an outdoor octagonal 1985 and 1986. Captured fish were maintained concrete tank containing 60 kl of seawater (2 m at the Yaeyama Station of the National Center depth) throughout the year. Sand-filtered sea- for Stock Enhancement, Fisheries Research water was supplied to the tank at the rate of 2－ Agency (Fig. 1). Spawning investigations were 3 turnovers per day. In 1992 and 1993, fish were conducted during the first spawning period in stocked in a cubic net cage (5 m wide, 5 m long, April and May of each year during 1989－1993. 5 m deep) in a coral lagoon and were reared in Females and males were seven and four in 1989 an octagonal tank during a spawning season. The and five and five in other years. The mean total water temperature and photoperiod were allowed to fluctuate naturally during the rearing period. The seawater salinity was around 35‰. Water temperature was measured daily at around 10:00 a.m. The fish were fed to satiation one or two days a week with jack mackerel Trachurus Japan japonicus coated with nutrients such as vitamins. The fish were allowed to spawn naturally. The effluent from the broodstock holding tank was introduced into a rectangular polyester net (0.3 mm mesh) set in an egg collecting tank (0.9 m wide, 2.4 m long, 1.8 m deep) through a 100 mm diameter plastic hose. Whenever Okinawa spawning occurred, the eggs were collected Island using a scoop net and transferred into a mea- suring cylinder with 2 l seawater. The number of eggs was estimated by multiplying the N volume of buoyant and sunken eggs in a mea-

24°30′N suring cylinder by the number of eggs per mil- Yaeyama st. liliter of eggs, as counted under a stereoscopic Ishigaki microscope. All buoyant eggs were fertilized, Iriomote 24°20′N Island but no fertilized eggs were found among Island sunken eggs. The fertilization rate of eggs was

E E E E determined as the percent ratio of the number ′ ′ ′ ′ 00 10 20 24°10′N 50 of buoyant eggs to the total number of buoyant ° ° ° ° 10km 124 124 124 123 and sunken eggs in each spawning day. The 30 buoyant eggs’ diameters were measured to the Fig. 1. Map showing Ishigaki Island, where this study was conducted. The location of Yaeyama Station, National nearest micrometer. Center for Stock Enhancement is shown.

Table 1. Number, body size (mean±SD), and body weight (mean±SD) of the captive camouflage Number Total length (cm) Body weight (kg) Year Female Male Female Male Female Male 1989 7 4 54.8 ± 3.5 58.5 ± 1.7 3.73 ± 1.19 4.90 ± 0.29 1990 5 5 52.2 ± 1.5 57.9 ± 1.9 3.28 ± 0.38 4.70 ± 0.56 1991 5 5 53.3 ± 2.0 58.0 ± 1.6 2.67 ± 0.36 4.03 ± 1.03 1992 5 5 56.3 ± 2.7 58.9 ± 1.7 4.04 ± 0.88 4.57 ± 0.88 1993 5 5 56.5 ± 1.1 59.9 ± 1.4 4.31 ± 0.44 5.46 ± 0.94 362 K. Teruya, S. Masuma, Y. Hondo and K. Hamasaki

Spawning behavior of captive fish Changes of GSI of wild fish Spawning behavior of fish was monitored in The GSI values of females were low (＜0.5) detail on May 13, 1993 using an underwater in February (Fig. 3), but they then increased video system inserted into the broodstock hold- rapidly and peaked at 15－16 in April and ing tank (Eye-ball; Hitachi Zosen Corp., Japan), May. Some females showed high GSI values taking care not to disturb the fish behavior. The until early July. In September and October, spawning behavior was also recorded using a GSI values were less than 0.5. Although the video camera (S-VHS movie camera; Panasonic GSI values of males were lower than those of Inc., Japan) from the water surface. For night females, the values varied in a cycle similar to recording, two 500 W lights were suspended that of females. Fish of undetermined gender over the tank. This treatment did not visibly were observed from late August to February influence the fish spawning behavior. and showed low GSI values of 0.03－0.33.

Statistical analysis Spawning of captive fish The values of total length of males and First spawning of captive fish occurred females sampled from the wild were compared during different periods in late April and mid- using Mann-Whitney’s U-test. Significance was May of the solar calendar (Gregorian calendar). inferred for P －＜0.05. However, it occurred during almost the same period, from the 19th to the 23rd day in the Results third month of the lunar calendar (lunisolar cal- endar) during the full moon and the last quarter Sex and maturity of wild fish moon at the age of the moon of ca. 18－22, in Sex was determined for 41 females and 16 each year of 1989, 1991, and 1992 (Table 2). males. Twelve individuals had no visible oocytes or milt; their gender was not determined. The 20 GSI was plotted against the fish TL (Fig. 2). Females and males were, respectively, 35.5－ 16 60.4 cm and 41.0－55.3 cm TL. High GSI values were observed for females and males over the 12 GSI range of body sizes. Females were significantly 8 smaller than males (P＝0.0114): they reached maturity at a smaller body size than males. 4 0

20 6 5 16 4 12 3 GSI GSI 8 2

4 1

0 0 30 40 50 60 Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Total length (mm) Month Fig. 2. Relationship between total length and gonadoso- Fig. 3. Seasonal changes in the gonadosomatic index matic index (GSI) of wild camouflage grouper captured (GSI) of wild camouflage grouper captured in 1986 and in 1986 and 1987. Symbols show sex of individuals: ○, 1987. The χ-axis shows the solar calendar. Symbols show female; ●, male; ×, sex determined. sex of individuals: ○, female; △, male; ×, sex determined. Spawning of the Camoufl age Grouper 363

The first spawning period was from the 19th to males were reared in a tank. The largest (62 cm the 22nd day of the fourth month and from the TL, 7.06 kg BW) was the most dominant and 20th to the 23rd day of the leap third month of aggressive; it guarded a territory on the bottom the lunar calendar in 1990 and 1993, respectively. of the tank. The lunisolar calendar usually has 12 months, Spawning occurred from 10 p.m. to 11 p.m. on but a 13th month is added to the year every two May 13 (22nd day in the third month of the lunar or three years. The leap month takes the same calendar); this behavior was observed seven number as the preceding month. In 1993 (leap times during this period. Prior to spawning, a year), the intercalary month was added after male whose caudal fin was trembling circled an the third month. Hence, the spawning periods ovulated female and occasionally nudged her in 1990 and 1993 were observed immediately operculum (Fig. 4A). The pair commenced swim- after one month later than other years. Spawning ming, contacting each other laterally on the body occurred four times; the total number of buoy- and rising in the water column while circling each ant eggs spawned in each year was 7－53 mil- other. They occasionally released their gametes lion with a mean egg diameter of 859－923μm. in the middle of the water column (Fig. 4B). Fertilization rates of eggs were 28.3－94.0%. The After reaching an area immediately under the water temperature at spawning was 23.0－25.9℃. water surface, they released their gametes while beating the water with their caudal fins; they Spawning behavior of captive fish then descended individually to the bottom (Fig. Figure 4 shows a schematic diagram of the 4D). It took a pair 10－20 s to rise in the water spawning behavior. Sex was not visually deter- and descend to the tank bottom. The other non- mined before the spawning season. During the dominant males that had been unable to form a spawning season, males turned dark gray to pair with a female released their gametes while black all over, with marbled patterns, becom- the pair ascended to the water surface (Fig. 4C). ing less distinct but displaying a distinct black Spawning behavior was observed at almost the dorsal peduncle patch. In addition, the margins same time during the spawning period of May 11 of the dorsal, caudal and anal fins and the tip －14 in 1993. In this study, the number of spawn- of the pelvic fins of males become black. Five ing females was not determined.

Table 2. Spawning data for captive camouflage groupers

Water Number of eggs Number of Date of spawning 3 Mean egg temperature spawned (×10 ) Fertilization Year spawning diameter ± Solar Lunar at spawning Buoyant Sunken rate (%) times Lunar calendar SD (μm) calendar phase (℃) eggs eggs 1989 1 25-Apr 20th third month 19.0 24.0 20875 2000 91.3 896 ± 33 2 26-Apr 21st third month 20.0 24.1 22600 10720 67.8 887 ± 26 3 27-Apr 22nd third month 21.0 24.2 2340 280 89.3 916 ± 22 4 28-Apr 23rd third month 22.0 24.5 6740 3440 66.2 905 ± 27 1990 1 13-May 19th fourth month 17.9 24.5 1150 710 61.8 923 ± 18 2 14-May 20th fourth month 18.9 24.2 5070 2430 67.6 906 ± 25 3 15-May 21st fourth month 19.9 25.3 1500 3800 28.3 895 ± 30 4 16-May 22nd fourth month 20.9 24.8 375 713 34.5 883 ± 19 1991 1 3-May 19th third month 18.3 23.0 61 92 39.9 888 ± 26 2 4-May 20th third month 19.3 23.2 5920 1620 78.5 869 ± 20 3 5-May 21st third month 20.3 23.4 1360 140 90.7 884 ± 31 4 6-May 22nd third month 21.3 23.6 50 60 45.5 917 ± 13 1992 1 21-Apr 19th third month 17.9 24.2 836 120 87.4 880 ± 23 2 22-Apr 20th third month 18.9 24.3 12900 1850 87.5 859 ± 22 3 23-Apr 21st third month 19.9 24.3 6050 1200 83.4 862 ± 32 4 24-Apr 22nd third month 20.9 24.4 1430 130 91.7 889 ± 14 1993 1 11-May 20th leap third month 19.1 25.9 180 58 75.6 864 ± 13 2 12-May 21st leap third month 20.1 25.5 2130 770 73.4 885 ± 19 3 13-May 22nd leap third month 21.1 25.8 7540 480 94.0 884 ± 28 4 14-May 23rd leap third month 22.1 25.8 132 114 53.7 886 ± 25 364 K. Teruya, S. Masuma, Y. Hondo and K. Hamasaki

Surface pers at several sites from the northern to south- ern hemispheres typically occurs over a 2－3 month period with great seasonal variation. The spawning period of wild camouflage grouper at Ishigaki Island approximates that of other sites; ♀ the main spawning season at Ishigaki Island resembles those at Kuwait and Saudi Arabia (Rhodes and Sadovy 2002). Camouflage grouper males and females aggregate in large numbers to spawn at spe- cific times and locations each year in Pohnpei, Micronesia (Rhodes and Sadovy 2002). They use lunar periodicity to adjust the specific times of spawning, i.e., to complete the synchronous spawning at specific locations, as inferred for other grouper species (Toledo et al. 1993; Lee et al. 2002). Lunar-related spawning cycles Bottom have been reported for camouflage grouper Fig. 4. Schematic diagram of spawning behavior of the at several sites, with a wide variation in lunar captive camouflage grouper. Spawning behavior pro- periodicity, i.e., both new-moon and full-moon gressed from phase A through phase B to phase D. Males in phase C were sneakers (refer to the text for details). spawning depending on the site (Rhodes and Sadovy 2002). In this study, the first spawn- ing period of cultured camouflage grouper Discussion was observed from the 19th to the 23rd day in the third or fourth month of the lunar calen- Maturity, spawning season and lunar-related dar during the full moon and the last quarter spawning moon in each year during 1989－1993 (Table All camouflage groupers captured in this 2). Spawning after the full moon is inferred for study were sexually mature. High GSI values wild camouflage grouper in Pohnpei and New were observed respectively for females and Caledonia (Rhodes and Sadovy 2002). males over a range of body sizes: 35.5－60.4 cm and 41.0－55.3 cm TL (Fig. 2). Females also Prediction of the first spawning period reached maturity at a smaller body size than In 1990 and 1993, spawning occurred just one males; this phenomenon is closely related to the month later than during other years (Table 2). camouflage grouper being a protogynous her- Water temperature is well known as an impor- maphrodite (Debas et al. 1989). tant environmental factor affecting the gonad It can be concluded that at Ishigaki Island, maturation and spawning of fish (Scott 1979; the main spawning season of the wild camou- Migaud et al. 2002; Clark et al. 2005). Figure 5 flage grouper is April－May, when GSI values shows changes in water temperature in a brood- of females and males peak (Fig. 3). Some fish stock holding tank in each year during 1989－ showed higher GSI values until early July. 1993. Temperature changes showed a similar Therefore, the spawning season seems to con- trend during the five years and fluctuated tinue for 3－4 months in the field. The spawn- between ca. 19 and 22℃ from mid-January to late ing season of serranids differs depending on February and then rapidly decreased from 22－ the geographical area and species (e.g., James 23℃ to －＜20℃ from late February to early et al. 1997; Lee et al. 2002; Rhodes and Sadovy March. The cumulative temperature was calcu- 2002). Rhodes and Sadovy (2002) summarized lated from the day the temperature decreased to that the spawning season of camouflage grou- －＜20℃ in these periods for each year (Fig. 5). In Spawning of the Camoufl age Grouper 365

each year, first spawning occurred during the full 28 2000 moon to the last quarter moon after the cumula- 26 1600 1989 tive temperature exceeded ca. 1000－1100 d°. 24 1200 Delayed spawning in 1990 and 1993 is attribut- 22 800 able to the low water temperatures before the 20 400 spawning season (Fig. 5). Consequently, in 18 0 Ishigaki Island, we can predict that the first Jan. Feb. Mar. Apr. May spawning of captive camouflage grouper occurs 28 2000 around the 19th day of the lunar calendar during 26 1990 1600 the full moon to the last quarter moon after the 24 1200 cumulative temperature, as calculated based on 22 800 the minimum temperature during late February 20 400 and early March of the solar calendar, exceeds ca. 1000－1100 d°. 18 0

Jan. Feb. Mar. Apr. May ） ° 28 2000 d Spawning behavior and mating systems （

（℃） 1600 26 1991 This study first documented the spawning 24 1200 behavior of camouflage grouper in captivity 22 800 (Fig. 4). In the spawning season, the whole body of males turned dark gray to black with 20 400 marbled patterns. The largest male, the most 0 Water temperature 18 Jan. Feb. Mar. Apr. May dominant and aggressive of the males, guarded Cumulative temperature 28 2000 a territory on the tank floor and formed a pair 26 1600 with an ovulated female. Body color changes 1992 24 1200 were observed for wild camouflage groupers at spawning aggregation sites in Pohnpei (Rhodes 22 800 and Sadovy 2002). Reportedly, the male fre- 20 400 quently changes color in what appears to be 18 0 Jan. Feb. Mar. Apr. May territory-defining behavior. 28 2000 Spawning behavior of captive camouflage 26 1600 groupers resembled that of other grouper 1993 species such as chocolate hind 24 1200 boenack (Donaldson 1989), pigmy grouper 22 800 C. spiloparaea (Donaldson 1995), coral trout 20 400 (Teruya et al. 1992), and red spotted grouper 18 0 (Okumura et al. 2002). According to Okumura Jan. Feb. Mar. Apr. May et al. (2002), red spotted grouper dashed ver- Month tically in a pair from the bottom to the water Fig. 5. Changes in daily water temperature (wavy lines) surface and released gametes at the surface in and cumulative temperature (straight lines) in the camou- a tank. The pair sometimes jumped from the flage grouper culture tank during January and May of the surface and swam horizontally on the water solar calendar in each year during 1989－1991. Symbols surface before or after spawning. That behavior show the lunar phase: ●, new moon; ○, full moon. Horizontal broken arrows indicate days the temperature suggests that the low fertilization rate (19%) of decreased to －＜20℃ during late February and early eggs from captive red spotted grouper might be March; the cumulative temperature was calculated from the result of this jumping behavior from water this day. Vertical bars indicate the period when the cumu- surface during spawning in the limited space lative temperature exceeded 1000－1100 d°. Vertical arrows indicate the cumulative temperature when the first of a tank with insufficient water depth. In this spawning period begins. study, jumping behavior during spawning was 366 K. Teruya, S. Masuma, Y. Hondo and K. Hamasaki not observed for the camouflage grouper (Fig. Under extreme polygyny, in which very few 4). The variation of fertilization rates between males accomplish almost all matings, high vari- 28.3% and 94.0% among camouflage groupers in ance in male reproductive success results in a low this study (Table 2) might be attributable to the effective population size (Fessehaye et al. 2006). quality of gametes, which depends on other fac- The effective population size is always much tors such as the nutritional value of food for the smaller than in comparable monogamous popula- broodstock. tions when marked inequalities in the reproduc- The basic mating system for the camouflage tive success occur (Nunney 1993). Consequently, grouper was pair spawning, which resembles genetic variation of the offspring would be that of several grouper species (Donaldson reduced in the mating system of camouflage 1989, 1995; Teruya et al. 1992; Zabala et al. 1997; grouper under culture conditions with a limited Okumura et al. 2002). However, in this study, we number of broodstock. However, the presence observed sneaker males (Gross 1996), which of sneaker males might contribute to increased released their own gametes while a spawning genetic variability of the offspring in camouflage pair was releasing theirs (Fig. 4). This behav- grouper reared in tanks. In future studies, the ior has not been reported for other serranids. paternity of fertilized eggs and/or hatched larvae Consequently, sperm competition, the competi- must be confirmed using genetic markers. tion between the ejaculates of different males for the fertilization of an ovum (Parker 1970), is Acknowledgments expected to occur among camouflage grouper males. A positive relation between the intensity We would like to thank all the staff of the of sperm competition (= type of mating system) Yaeyama Station, National Center for Stock and relative sperm production has been found enhancement for their advice and encourage- in fish (Stockley et al. 1997; Balshine et al. ment. Cordial thanks are extended to S. Shimoji 2001). Marino et al. (2001) explained this rela- (Uminchu Saburo) for collecting the fish samples. tionship for serranids using examples of two grouper species. The mating system of wild References dusky grouper E. marginatus is pair spawning in single-male/multi-female social units during Alarcón, J. A., A. Magoulas, T. Georgakopoulos, E. Zouros the reproductive season (Zabala et al. 1997); the and M. C. Alvarez (2004) Genetic comparison of wild and cultivated European populations of the gilthead males have extremely small ripe testes, attain- sea bream (Sparus aurata). Aquaculture, 230, 65-80. ing only 0.6% of their body weight (Marino et Balshine, S., B. J. Leach, F. Neat, N. Y. Werner and R. al. 2001). The wild Nassau grouper E. striatus Montgomerie (2001) Sperm size of African cichlids in is a group spawner (Whaylen et al. 2004). relation to sperm competition. Behav. Ecol., 12, 726- 731. Consequently, males have large ripe testes, Clark, R. W., A. Henderson-Arzapalo and C. V. Sullivan attaining 10% of body weight (Sadovy and Colin (2005) Disparate effects of constant and annually 1995). The testes of male camouflage grouper cycling daylength and water temperature on repro- account for 0.5－5.5% of body weight (mean ductive maturation of striped bass (Morone saxatilis). Aquaculture, 249, 497-513. value, 2.2%; calculated as testis weight/ body Debas, L., A. Fostier, J. Fuchs, M. Weppe, G. Nedelec, A. weight×100 using data of Fig. 3) during the Bentett, C. Cauty, B. Jajabert and Aquacop (1989) The high reproductive season in late May. Therefore, sexuality of cultured hermaphroditic fish species: the mating system and relative testes weight of analysis of morphological and endocrinological fea- tures in a protogynous hermaphrodite, Epinephelus camouflage grouper were moderate between microdon, as a basis for further research to control dusky grouper and Nassau grouper. This find- reproduction in the grouper. In:“ Advances in Tropical ing supports the relation between the intensity Aquaculture” (ed. by J. Barret), AQUACOP, IFREMER, of sperm competition (= type of mating system) Actes de Colloque 9, Tahiti, French, Polynesia, pp. 543-557. and relative sperm production in serranids, as Donaldson, T. J. (1989) Pair spawning of Cephalopholis described by Marino et al. (2001). boenack (Serranidae). Japan. J. Ichthyol., 35, 497-500. Spawning of the Camoufl age Grouper 367

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石垣島におけるマダラハタの産卵期， 月齢に同調した産卵および配偶システム

照屋和久・升間主計・本藤 靖・浜崎活幸

石垣島におけるマダラハタの産卵期および産卵開始時期を明らかにする目的で，天然魚の生殖腺指 数を調査するとともに，天然魚を数年間養成した親魚の水槽内における産卵開始時期を 5 年間にわた り調査した。さらに，親魚の産卵行動を観察し，本種の配偶システムを明らかにすることを試みた。 天然魚の主要な産卵期は，雌雄とも生殖腺指数がピークに達する 4 月～5 月（太陽暦）であると推察 された。産卵期最初の親魚の産卵は，満月から下弦の月にかけての 3 月19日～23日（太陰暦）に集中 した。ただし，産卵期前の水温が低い年の産卵は，1 カ月後の満月から下弦の月の期間にシフトした。 このように，マダラハタの産卵は月齢に同調していた。水槽内では最大の雄 1 個体がなわばりを形成 し，その個体と成熟雌によるペア産卵が行われたが，小型雄によるスニーキングも観察された。