JOURNAL OF THE Vol. 29, No. 2 WORLD AQUACULTURE SOCIETY June, 1998

Artificial Propagation of Mutton Snapper analis, A New Candidate Marine Fish Species for Aquaculture

WADE 0.WATANABE', EILEENF? ELLIS,SIMON c. ELLIS,JUAN CHAVES AND CHRISTINEMANFREDI Caribbean Marine Research Center, 805 East 46th Place, Vero Beach, Florida 32963 USA

RANDOLPHW. HAGOOD,MARIA SPARSIS AND STEVENARNESON Atlantic Aquaculture Technologies, Inc., 4600 Taylor Dairy Road, Fort Pierce, Florida 34951 USA

Abstract Wild-caught mutton snapper Lutjanus analis, a high-value marine food fish species, ma- tured in flow-through seawater (36 &) tanks after 3 yr in captivity. On 31 May 1995, a female with a mean oocyte diameter of 382 pm was injected with human chorionic gonado- tropin (HCG) (500 IUlkg body wt.) followed 24 h later by a second injection (1,OOO IUkg body wt.). At the time of the second injection, three males were injected with HCG (500 IU/ kg body wt.). Voluntary spawning occurred 33 h after the first injection, with a total of 534, 781 eggs released. Fertilization rate was 75.7%, while average diameter of fertilized eggs was 783 pm. Embryos were stocked in a 30-m3 outdoor tank at a density of 10.5L. On day 2 post-hatching (d2ph), larval density was 8.61 larva&, and average notochord length was 2.6 mm. Larvae were fed ss- rotifers from dl-d28ph, Artemia nauplii from d7-d38ph, and artificial diets (52-48% protein) from d24-d38ph. On d38ph, fish averaged 0.308 g and 22.2 mm standard length. Survival (from d2ph) was 14.3%, with a total of 36,900 post-metamor- phic juveniles produced. On d97ph, 1,390 hatchery-reared juveniles (avg. wt. = 10.5 g) were stocked into two 14.5-m3 recirculating seawater tanks (695 fish/tank; 48 fish/m3) and fed a 56% protein pellet. After 168 d, fish averaged 140.8 g, with a survival rate of 97.8% and a feed conversion ratio (dry wt./wet wt.) of 1.2. These preliminary results reveal the mutton snapper to be a prime, new candidate species for commercial cultivation.

The mutton snapper Lutjanus analis (Fig. Adults have an attractive body conforma- 1) is an important food fish species in the tion and color: olive above the , tropical western Atlantic (Bortone and Wil- white with a reddish hue below, with red liams 1986), with distribution ranging from fins and blue spots around the eye (Bohlke New England to southeastern Brazil, in- and Chaplin 1993). cluding the Bahamas and the Gulf of Mex- A carnivorous species, the mutton snapper ico (Bohlke and Chaplin 1993). Juveniles feeds on fishes and (Randall and small adults are found in shallow areas 1967) and is considered one of the most de- near mangroves and grass beds (Mueller et licious saltwater fishes to eat. The mutton al. 1994), while larger adults may be found snapper resembles and is often marketed as in deeper waters on the continental shelf. L. the red snapper L campechanus (Robins and analis is a large snapper that grows to near- Ray 1986); taste and appearance are indistin- ly 30 inches (76 cm) in length and 25 guishable between these species once filleted. pounds (1 1.4 kg) in weight (Mason and In the early 1900s, mutton snapper was Manooch 1985; Bohlke and Chaplin 1993). commonly sold at fish markets in Puerto Rico, Cuba and Florida (Mueller et al. 1994). However, overfishing of shelf-edge I Corresponding author's present address: Center for Marine Science Research, The University of North spawning aggregations have led to a major Carolina at Wilmington, 7205 Wrightsville Ave., Wil- decline in landings in recent years, with a mington, North Carolina 28403 USA. collapse of the commercial fishery in some

0 Copyright by the Wnrld Aquaculture Society 19YX

176 ARTIFICIAL PROPAGATION OF MUTTON SNAPPER 177

FIGUREI. Adult mutton snapper Lutjanus analis. (C. Munfredi photo). locations off Florida and Cuba (Gulf of Materials and Methods Mexico Fishery Management Council Induced Spawning 1992). Relatively little is known about the reproductive biology and early life history This study was conducted at the Carib- of this species. bean Marine Research Center on Lee Snappers belonging to the family Lutjan- Stocking Island (Exuma Cays), Bahamas idae (i.e., lutjanids), including the man- (23"45'N, 76"lO'W) and at Atlantic Aqua- grove snapper L. argentimaculatus and culture Technologies, Inc. in Vero Beach, John's snapper L. johni, command high Florida from May 1995 to February 1996. market prices in Southeast Asia and are cul- Fifteen sub-adult mutton snapper L. analis tured in floating net cages and brackish- (0.30-0.78 kg; 28-39 cm TL) were trapped water ponds in Singapore, Indonesia and in waters off Lee Stocking Island from the Philippines (Emata et al. 1994). Supply May-August 1992. Fish were maintained of seed for farms depends entirely on wild under ambient photoperiod and temperature fry, which is limited and unreliable (Lim et in an outdoor, 15-m3 flow-through seawater al. 1985; Singhagraiwan and Doi 1993; (36-38 g/L) tank supplied with aeration and Emata et al. 1994) and therefore a major covered with two layers of 70% light-oc- constraint to the sustainability of snapper cluding cloth. A commercially prepared aquaculture in these regions. (Zeigler Bros., Pennsylvania, USA) striped Given a premium value, high demand, and bass grower diet containing 38% protein or the over-exploitation of natural populations, frozen squid and fish were provided daily the mutton snapper was selected for evalua- to satiation. tion as a potential aquaculture species in the In May 1995, ovarian maturity of brood- U.S. In this report, results of preliminary tri- stock was assessed by biopsy (Shehadeh et als on artificial propagation, including hor- al. 1973), A polyethylene cannula (1.52- mone-induced spawning of captive brood- mm o.d., 0.86-mm i.d.) was inserted into stock, culture of larvae through metamorpho- the oviduct of an anaesthetized (100 mg/L sis, and growout of juveniles in a recirculat- tricaine methane sulfonate) female, and a ing culture system, are described. sample of gonadal tissue was removed by 178 WATANABE ET AL. oral suction as the cannula was withdrawn. pressed as percentages of total eggs and of The samples were fixed in a solution of buoyant eggs. 10% formalin in seawater. Using a com- pound microscope fitted with an ocular mi- Larval Culture crometer, the diameters of at least 100 oo- Between 1 June and 10 July 1995, sur- cytes were measured to the nearest 50 Fm, vival and growth of larval mutton snapper, from which a mean and standard deviation from egg to metamorphic stages, were stud- were calculated. Developmental stage of ied under pilot-scale hatchery conditions. oocytes was assessed from microscopic ap- The rearing unit consisted of an outdoor, pearance (Kuo et al. 1974). In males, ma- above-ground, rectangular tank (7.5 X 4.5 turity was assessed by the presence or ab- X 0.90 m = 1 X w X d; volume = 30 m3), sence of milt when gentle pressure was ap- constructed of framing lumber, lined with plied to the abdomen. Fish were weighed black, high-density polyethylene. The tank and measured (total length = TL; fork was enclosed by a translucent polyethylene length = FL) after sampling. At the time of greenhouse with a 70% light-occluding this study in May 1995, sex ratio was 8 cloth cover. Light intensity at the water sur- female: 5 male: 2 undetermined. Females face measured between 0800 h and 1500 h ranged from 1.15-2.08 kg and 46-50 cm was approximately 7,000 to 12,000 lux. TL (38.4-44.5 cm FL), while males ranged Aeration was provided from a blower from 1.22-1.93 kg and 43.2-47.5 cm TL through six nylon tee connectors (used in (40.3-45 cm FL). lieu of airstones) spaced equidistantly On 31 May, hormone-induced spawning throughout the tank. A minimum level of was attempted in a female (1.79 kg; 49.5 aeration for dispersion of eggs and larvae cm TL, 46 cm FL) with mature, vitellogenic was used (Ellis et al. 1997). stage oocytes and a low percentage (2.7%) Fig. 2 summarizes the feeding regimen used during the pilot-scale trial. One week of atretic eggs. To induce spawning, human prior to the spawning, the rearing tank was chorionic gonadotropin (HCG) (Sigma filled with unfiltered seawater and fertilized Chemical Co., St. Louis, Missouri, USA) with ammonium phosphate (50 g), mono- was used in a series of two intramuscular potassium phosphate (15 g). urea (2.5 g), injections. A first (priming) dose of 500 IU/ Fe-EDTA (7.5 g). and trace metal mix (0.5 kg body wt. was administered at 0600 h g) (Oceanic Institute, Honolulu, Hawaii, followed 24 h later by a second (resolving) USA), then inoculated with the microalga dose of 1,OOO IUkg body wt. At the time Nunnochloropsis oculutu (150 X lo3 cells/ of second injection, three males were also mL) and, after 5 d, ss-type rotifers Bru- injected with HCG (500 IUkg body wt.) to chionus plicutilis (1 individudml). On the stimulate spermiation. Spawners were re- day of spawning, fertilized eggs (approxi- turned to the original broodtank for - mately 1-2 h post-fertilization) were ing trials. stocked into the rearing tank at a density of After spawning, eggs were collected 10.5 eggs/L. from the water surface using a fine mesh Larvae were fed ss-type rotifers until day dip net and transferred to three 500-L in- 28 post-hatching (d28ph) (Fig. 2). Rotifers cubators containing seawater and supplied were grown at 22 g/L salinity in a batch with aeration. Total number of eggs culture system and fed N. oculutu and Ba- spawned was determined volumetrically. ker’s yeast Succhuromyces cerevisue at an Aeration was suspended approximately 30 approximate 1:l ratio. Rotifer and algae min post-fertilization, and buoyant eggs concentrations in the rearing tank were were skimmed and transferred to a separate monitored daily and replenished as avail- incubator. Fertilization success was ex- able. Rotifers were added at concentrations ARTIFICIAL PROPAGATION OF MUTTON SNAPPER 179

-Nannochloroosis oculata - - Brachionus Dlicatilis c

. Artemia salina - -Artificial food -

-7 1 7 10 20 25 35 37

t t Days post-hatching Added Stocked fertilizer eggs

FIGURE2. Feeding regimen used during pilot-scule culture of mutton snapper from egg to metamorphic stages in a 30-in3 tank (see text,for detuils).

(individuals/mL) averaging 18 (range = subsurface siphons. Four surface skimmers 12-27) from dO-dSph, declining to an av- (Lim 1993) were used to reduce oily sur- erage of 8 (range = 1-15) until d28ph. Al- face film and were cleaned twice daily. gae was maintained at ,approximately 25 X Survival was monitored volumetrically lo3 cells per rotifer per mL. on d2, d5, d7, d10, d15, d20 and d25ph Newly hatched San Francisco Bay (SFB) with the use of a PVC column (10 cm X strain Artemia nauplii were fed at 1/L from 1.2 m = diam. X 1) equipped with a ball d7-d9ph. One-day-old enriched Artemia valve. Vertical samples were collected at (SFB strain) were added three times daily night when larvae were more uniformly (0900, 1200, and 1600 h) from dlOph to distributed. On d38ph, total number of fish d20ph, in total numbers increasing from remaining was determined gravimetrically. 0.21 X loh to 23.5 X 10Vd during this pe- Growth was monitored d2, d5, d6, d8, riod. Nauplii were enriched with a com- dl 1, d16 and d2lph by measuring the no- mercial fatty acid booster (high-DHA Super tochord lengths (NL) of 20 fish with a mi- Selco; Arternia Systems, NV-SA, Gent, croscope equipped with an ocular microm- Belgium) for 15-22 h prior to being fed to eter. Standard lengths (SL) were measured larvae. From d21 to d35ph. larvae were fed on d26, d31, and d38ph. On d38ph, 100 fish enriched Great Salt Lake (GSL) strain Ar- were weighed individually. temia in numbers increasing from 24.3 X Water temperature and dissolved oxygen loh to 66.9 X 106/d. were recorded twice daily, and salinity and On d24ph, Artemia were added to the total ammonia nitrogen were measured rearing tank later in the day and an artifi- once daily. Mean water quality values +- SE cial, pelleted diet (Nippai ML-400; 52% (range) were as follows: temperature 28.7 protein, 12% fat; particle size = 400-850 -+ 0.1 C (26.8-30.4 C); dissolved oxygen pm) (Nippon Formula Feed Manufacturing 6.08 -+ 0.10 mg/L (4.1-7.9 mg/L); salinity Co. Ltd., Yokahama, Japan) was fed hourly 37.5 ? 0.2 g/L (36-39 g/L), and total am- from 0700 h to 1200 h and at 1500 h. Tran- monia nitrogen 0.12 1 -+ 0.0 12 mg/L (0.0 1- sition to a larger feed (Nippai ML-800; 0.27 mg/L). 48% protein, 8% fat; particle size = 800- 1,500 pm) was begun on d29ph, and was Juvenile Growout fed every 2 h from 0700 h to 1900 h. Hatchery-reared postlarvae from the 1 Seawater (36-38 g/L) exchange began on June spawn were held in 4.5-5 m3 flow- dlph at a rate of lO%/d and was gradually through seawater tanks from d38-d96ph increased to 150%/d by d37ph. Water was and fed ad-libitum a commercially-prepared drained from the tank through screened, mahimahi grower (Zeigler Bros., Pennsyl- 180 WATANABE Er AL vania, USA) containing 50% protein. On 475 pm), and a unimodal egg diameter-fre- d97ph (7 September 1997), 1,390 juveniles quency distribution was observed (Fig. 3a). (avg. wt. = 10.5 g, range = 4.8-18.4 g) Within 24 h of the first injection, mean oo- were air-shipped in oxygenated plastic bags cyte diameter increased to 475 pm (range to Atlantic Aquaculture Technologies, Inc., = 275-575 pm) (Fig. 3b), while the fre- a commercial marine fish farm in Vero quency distribution of oocyte diameters re- Beach, Florida, where they were stocked mained unimodal. into two outdoor 14.4-m3 fiberglass tanks Under a water temperature that averaged (dim. = 3.5 m; depth = 1.4 m) at a density 28.5 C during the hormone induction peri- of 48.3 fish/m3 (695 fish/tank, 0.51 kg/m3). od, voluntary spawning occurred 33 h after Both tanks were supported by a common the first injection, with a total of 534, 781 water recirculation system, consisting of a eggs released. Overall fertilization rate was high-rate sandfilter for solids removal and 75.7%, while fertilization rate of buoyant a “fluidized bed” biofilter. Water flow to eggs was 84%. Buoyant eggs were trans- each tank was approximately 100 L/min, lucent, spherical, and contained a single oil providing 10 exchanges per d. Freshwater droplet. Mean diameter of fertilized eggs was added periodically to maintain water (measured at 1 h post-fertilization) was 783 level and a salinity of 30 g/L. NaHCO, was pm (range = 725-875 pm) (Fig. 3c). added as required to maintain pH above 7.4. Beginning approximately 3 h prior to Tanks were covered by 70% light-occluding spawning, males followed and circled the shade cloth. injected female and the coloration of both Fish were hand fed to satiation three male and female spawners darkened. Ovi- times daily from dO to d90 then once daily position was completed in less than one a commercially-prepared (Moore-Clark min, with eggs released at the water surface Co., Vancouver, British Columbia, Canada) by the female, whose dorsal surface was mahi mahi grower containing 56% protein frequently exposed, while males circled and 14% fat. rapidly below. Fish were grown under ambient photo- Larval Culture period and temperature conditions through Under an incubation temperature of 27.7 late November, when solar heaters were C, hatching commenced 17 h post-fertiliza- used periodically to maintain water temper- tion. On d2ph, larval density was 8.61 lar- atures above 18 C. Water temperature was vae/L. Larval survival (from d2ph) declined monitored daily, salinity, dissolved oxygen, gradually to 29.3% (2.52 fish/L) by d20ph, pH, total ammonia nitrogen, and alkalinity then declined more slowly to 14.3% (1.23 were monitored every 5 d. fish/L) by d38ph (Table l), when a total of Growth was monitored by measuring to- 36,900 post-metamorphic juveniles were tal length and weight of at least 50 fish us- produced. Timing of metamorphosis varied ing an anesthetic (0.3 g/L 2-phenoyxethan- among individuals from approximately d30 01). on do, d89, and on d168 when the ex- to d38ph. periment was terminated. Growth rate was Larval notochord length (Table 1) on expressed as daily weight gain [final wt. (g) d2ph was 2.66 mm, increasing slowly to - initial wt. (g)/time (d)] and as specific 4.94 mm by d2lph. Growth was rapid after growth rate [(ln final wt. (g) - In initial wt. d2lph, with larvae reaching 22.2 rmn SL (g))/time (d)] 100. (range = 18.5-25.8 mm) by d38ph, when Results fish averaged 0.309 2 0.015 g. Induced Spawning Juvenile Growout Prior to the first hormone injection, mean At the end of the 168-d growout study, fish oocyte diameter was 382 pm (range = 225- averaged 140.8 g (207 rmn TL) (Table 2) for ARTIFICIAL PROPAGATION OF MUTTON SNAPPER 181

90 r Pre-injectlon 00 .

70 - 60 - a 50 - P = 382 rrn

225 275 325 375 425 475 525 575 625 675’ 725 775 025 075

b P = 475 prn

225 275 325 375 425 475 525 575 625 075 725 775 025 075

1 h post-fertilization 90 r

C

225 275 325 375 425 475 525 575 625 675 725 775 625 075 Oocyte diameter (pm)

FIGURE3. Oocyte diameter-frequency distribution in a mutton snapper female at various stages of HCG- induced spawning: (a) 24 h pre-injection, (b) second injection and (c)fertilized eggs at I h post-spawning. Distributions are based on samples of 100 eggs. an average daily weight gain of 0.78 g/d and 100-180 g. Feed consumption for the dura- a specific growth rate of 1.55%/d. Final in- tion of the study averaged 1.58% body wt./d dividual weights ranged from 30-300 g (Fig. while overall feed conversion ratio (dry wt. 4), with 69.4% of these fish ranging from fed/wet wt. gain) was 1.2. 182 WATANABE ET AL.

TABLE1. Survival and growth of larval L. analis were maintained within acceptable limits from hatching through metamorphic stages during throughout the study. pilot-scale culture in a 30-m' tank. Fertilized eggs were stocked at a density of 10.5 eggs/L. Fish remained robust throughout the study, and final survival was 97.8%, while Age Survival final biomass density was 6.65 kg/m3 (Table (d post- Notochord lengthh 2). Abnormalities were observed in a small hatching) (larvaen) (%)" (mm) percentage of individuals, including scoli- 2 8.61 100 2.66 t 0.32 osis (5.0%) and gill plate deformities 5 6.85 79.6 2.96 2 0.25 6 3.03 f 0.27 (2*4%)- 7 6.56 76.2 8 3.39 2 0.22 Discussion 10 5.38 62.5 Induced Spawning 11 4.12 ? 0.53 15 4.72 54.8 Wild-caught mutton snapper apparently 16 4.67 2 0.56 reached first maturity during their third year 20 2.52 29.3 in captivity. This conclusion is based on 21 4.94 2 0.35 their relatively small initial sizes (25-35 cm 25 2.16 25.1 26 9.68 f 1.54 FL, 28-39 cm TL), which indicated that 31 16.2 f 1.40 these individuals were sub-adults at cap- 38 1.23 14.3 22.2 f 3.61 ture. Sizes of these fish at spawning (43-50 Percentage of larval density on d2ph. cm TL) is also consistent with previous data Mean f SD (N = 20, except for d38ph when N = on first-maturing adults (40.2 cm FL, 43.9 100). cm TL) (Rojas 1960 in Grimes 1987). De- finitive information on age/size at first ma- turity in mutton snapper is needed for Water temperature during the study av- broodstock management purposes. Avail- eraged 25.7 2 0.2 C, but ranged from 18 able data suggests a relatively long period to 31 C due to seasonal changes. Salinity of growth to first maturity, a factor that will averaged 24.1 2 0.6 g/L, but fluctuated be- place a premium on broodstock. tween 18 and 30 g/L with evaporation and In this study, gonadal maturation and rain. Relatively large declines in alkalinity spawning of captive mutton snapper brood- (88.7 2 5.9; range = 40-140 mg/L as stock was associated with increasing day- CaCO3) and pH (7.4; range = 6.8-7.7) ne- length and water temperatures in late cessitated periodic additions of NaHCO,. spring/early summer. This is similar to what Dissolved oxygen (5.88 2 0.08; range = was reported for the vermilion snapper 5.00-6.20 mg/L) and total ammonia nitro- Rhomboplites aurorubens (Grimes and gen (0.34 5 0.04; range = 0.10-1.0 mgL) Huntsman 1980) in southeastern U.S. wa-

TABLE2. Growth, survival. and biomass density during pilot-scale growout ofjuvenile L. analis in recirculating seawater tanks. Two 14.4-mJ tanks were each stocked with 695 juveniles (age = 97 d post-hatching) and grown for 168 d.

Age (d post- Body wt.' Total length" Survival" Biomasp hatching) Expt. day (n) (mm) (a) (kg/m2) Nb

~ ~ 97 0 10.5 2 2.5 88.7 ? 8.9 100 0.507 51 186 89 68.7 ? 18.8 157 ? 13.6 99.9 3.31 144 265 I68 140.8 ? 46.2 207 t 7.8 97.8 6.65 1,037

a Values represent mean ? SD for fish sampled from both tanks. N = number of fish sampled. ARTIFICIAL PROPAGATION OF MUTTON SNAPPER 183

FIGURE4. Frequency distribution of body weights for subadult mutton snapper (N = 1.037) grown for 168 d in 14.4-in’ recircululing sruwuter tanks. ters, the ehu Etelis carbunculus (Everson oocyte diameters was observed prior to suc- 1984) in Hawaii, and the red snapper L. cessful induced spawning. This is in con- campechanus (Arnold et al. 1978) held un- trast to many lutjanids which show a po- der an artificial photothermal regime simu- lymodal distribution, a pattern generally as- lating conditions in the northwestern Gulf sumed to indicate multiple spawnings by of Mexico. Results of the present study sug- individual females during the reproductive gest a summer spawning season for mutton season (Grimes 1987). However, the pro- snapper in the central Bahamas. Reproduc- cess of recruitment of maturing oocytes tive seasonality in a given lutjanid species, from the undifferentiated oocyte pool is not however, may vary among populations, understood in lutjanids, and the relationship from extended summer spawning, to year- between numbers of modes and numbers of round spawning with pulses in spring and spawnings is therefore unclear (Grimes fall, possibly depending upon habitat (e.g., 1987). As was observed in the Nassau oceanic island vs. continental) (Grimes grouper Epinephelus striatus, a unimodal 1987). Spawning seasonality of a captive distribution does not preclude multiple in- mutton snapper broodstock, therefore, can- duced spawnings within a single season not be reliably predicted from seasonal con- (Watanabe et al. 1995). siderations, and experimental studies are The mammalian gonadotropin, HCG, needed to determine the effects of artificial used widely to induce ovulation and spawn- temperature and photoperiod regimes on ing in finfish (Lam 1982; Donaldson and gonadal maturation of captive broodstock Hunter 1983; Shelton 1989), was an effec- as a basis for controlled breeding programs. tive agent for inducing final maturation and In this study, a unimodal distribution of ovulation leading to spawning in female 184 WATANABE ET AL. mutton snapper. Similar results were re- tion of both males and females was also ported in red snapper L. campechanus practiced during voluntary spawning of (Minton et al. 1983), John’s snapper L. John’s (Lim et al. 1985) and mangrove johni (Lim et al. 1985). yellowtail snapper (Singhagraiwan and Doi 1993; Emata et al. Ocyurus chrysurus (Soletchnik et al. 1989) 1994) snappers. Male courtship behavior and mangrove snapper L. argenrimaculatus may be an important prelude to voluntary, (Emata et al. 1994). Mean pre-injection di- synchronized release of gametes by spawn- ameter of the female spawned in this study ers (Zohar 1989). (382 pm) was similar to those reported for In the present study, 404, 829 fertilized induced spawning of red snapper (354-365 eggs were produced following induced pm) (Minton et al. 1983), mangrove snap- spawning of a single female. Natural per (400 pm) (Emata et al. 1994) and spawnings, without hormone induction, John’s snapper (400 pm) (Lim et al. 1985). have been reported in captive red snapper Work is needed to establish the critical min- (Arnold et al. 1978) and yellowtail snapper imum oocyte diameter for induced spawn- (Soletchnik et al. 1989), but were unpre- ing of mutton snapper. dictable and produced relatively small In this study, a two-injection sequence quantities of eggs (3,000-27,000) (Soletch- was used, with spawning obtained 33 h af- nik et al. 1989). Hormone induction is an ter the first injection, similar to results re- important method to supply fertilized eggs ported for L. johni (Lim et al. 1985). On on demand. the other hand, a single injection of HCG induced spawning of John’s snapper (Lim Larval Culture et al. 1985), yellowtail snapper (Soletchnik The survival rate (14.2%) of mutton et al. 1989) and mangrove snapper (Emata snapper larvae to the metamorphic stages in et al. 1994), which occurred from 27-37 h this study surpasses those attained in pre- after injection. Proper hormone dose rate vious rearing attempts with larval lutjanids. and latency varies with a number of factors, For mangrove snapper (Singhagraiwan and including age, stage of ovarian develop- Doi 1993; Emata et al. 1994), yellowtail ment (i.e., oocyte diameter), water temper- snapper (Soletchnik et al. 1987) and red ature (Shelton 1989; Watanabe et al. 1995) snapper (Rabalais et al. 1980; Minton et al. and broodtank size (Lim et al. 1985), and 1983; The Aquaculture News October must be standardized for the mutton snap- 1996), larvae typically died early in devel- per through further study. Because of their opment or survived through metamorphosis higher potency and lower cost (Harmin and at very low rates. Relatively good survival Crim 1992; Bromage 1995; Carillo et al. was obtained with John’s snapper in Sin- 1995; Zohar et al. 1995), the efficacy of su- gapore using a diverse feeding regime, in- peractive analogues of mammalian gonad- cluding mussel larvae, rotifers, Arfemia otropin releasing hormones, such as lutein- nauplii, wild zooplankton, moina and izing hormone-releasing hormone analogue minced meat. Survival rate through meta- (LHRH-a), on spawning of mutton snapper morphosis (d30-35ph) of larvae stocked in merits evaluation. 5-m3 tanks at densities of 20-25,000/m3 av- Circumstantial evidence suggests that eraged 1%, with a maximum of 5% (Lim HCG was effective for stimulating spermia- et al. 1985). Survival to metamorphosis of tion in mutton snapper males, which dis- mutton snapper larvae in the present study played vigorous courtship behavior and is comparable to those attained in commer- achieved good fertilization success, even cial hatcheries in Europe for sea bream Spa- though little sperm could be expressed from rus aurata (i.e., 10-20% at weaning onto these individuals at the time of injection, formulated feeds) (Sorgeloos and Sweet- only 9 h before spawning. Hormone injec- man 1993). ARTIFICIAL PROPAGATION OF MUTON SNAPPER 185

Larval culture trials with John’s snapper lieved to be significant causes of mortality (Lim et al. 1985) and mangrove snapper in hatchery-reared larval fish (Hecht and Pi- (Emata et al. 1994) were characterized by enaar 1993; Watanabe et al. 1996). Al- two periods (approximately d3-d7ph and though chasing and tail-biting were noted d18-d28ph) of high mortality. In contrast, among larvae and juveniles in this study, survival of mutton snapper larvae in this consumption of cohorts was not observed, study declined gradually to d20ph (Table 1) despite considerable size variation among and slightly thereafter. High early survival pre-metamorphic staged fish. of mutton snapper compared to John’s or mangrove snappers does not appear to be Juvenile Growout attributable to size differences among the Mutton snapper juveniles proved ex- early developmental stages of these species, tremely hardy under culture in recirculating which have very similar fertilized egg di- seawater tanks, showing no evidence of dis- ameters (0.78, 0.74, and 0.8 mm, respec- ease and few mortalities despite handling tively) and larval sizes on d3ph near the for growth measurements and marked fluc- time of first-feeding (2.76 mm NL, 2.75 tuations in water temperature, salinity, and mm TL, and 2.87 mm TL, respectively). pH. Growth rates and feed conversion ob- Relatively high survival of larval mutton tained in this study were good, but can like- snapper in this study may be related in part ly be improved through control of environ- to improved nutrition. In contrast to earlier mental conditions within optimal ranges. rearing trials with other lutjanids, larval No published data is available on temper- mutton snapper in this study were fed Ar- ature and salinity optima for growth of mut- temia enriched with n-3 highly unsaturated ton snapper, but preliminary laboratory fatty acids, particularly docosahexaenoic studies indicate juvenile growth is higher at acid (DHA), essential for normal growth 30 C than at 25 C (S. C. Ellis et al., un- and stress resistance in larval marine fish published data). Hence, rearing tempera- (Watanabe 1993). In addition, whereas only tures in this study (average = 25.7 C) were live feeds were used in earlier studies, the probably suboptimum during the late fall supplementation of live feed (Artemia)with and winter when temperatures fell as low an artificial diet (Sorgeloos 1994) beginning as 18 C. Furthermore, while juvenile mut- on d24ph in this study was associated with ton snapper in this study were tolerant of a dramatic increase in larval growth (Table reduced salinities, which declined as low as 1) and a stabilization in survival after 18 g/L, culture at an optimal salinity may d20ph. Since larvae readily accepted the ar- improve growth. Experimental studies on tificial diet on d24ph, it is likely that mutton the combined effects of temperature and sa- snapper larvae could be weaned at an even linity on growth of juvenile mutton snapper earlier age. are needed to delineate optimal conditions High survival of larval mutton snapper for growout. through metamorphic stages in this study Growth and feed conversion during was also probably related to species-specif- growout can also likely be improved ic behavioral characteristics. Unlike many through nutritional means. In this study, a tropical marine fish species that do not ac- mahi mahi grower diet, characterized by a cept rotifers (Young 1994), these prey ap- high protein and lipid content, was used. To parently elicited a strong feeding response optimize diet composition, studies are need- in first-feeding mutton snapper, resulting in ed to determine the dietary protein, lipid efficient prey capture and consumption. In and energy to protein ratio requirements of addition, high survival of larval mutton juvenile mutton snapper (Ellis et al. 1996; snapper may be related to a lower incidence Johnson 1996). of interfish aggression and cannibalism, be- Successful development of commercial 186 WATANABE ET AL. marine finfish culture in the U.S. can be sig- E. Mananos and N. Bromage. 1995. Sea Bass nificantly advanced by identifying high-val- (Dicentrardzus lubrux). Pages 138-168 in N. R. Bromage and R. J. Roberts, editors. Broodstock be ued, high-demand species that can easily management and egg and larval quality. Black- reared through larval stages and that can be well Science Ltd., Oxford/London/Edinburgh/ grown to marketable sizes in intensive re- Cambridge. circulating systems which minimize land Donaldson E. M. and G. A. Hunter. 1983. Induced requirements, permit operations away from final maturation, ovulation and spermiation in cul- the high-priced coastal zone and mitigate tured fish. Pages 351-403 in W. S. Hoar and D. J. Randall, editors. Fish physiology, volume 9B. multi-user conflicts and problems of efflu- Academic Press, New York, USA. ent discharge requirements (NRC 1992; Ellis, S., G. Viala and W. 0. Watanabe. 1996. Watanabe 1995). While preliminary, results Growth and feed utilization of hatchery-reared ju- of this study indicate that the mutton snap- venile Nassau grouper fed four practical diets. The per is a prime, new candidate species for Progressive Fish-Culturist 58: 167-172. Ellis, E. P., W. 0. Watanabe, S. C. Ellis, J. Ginoza commercial aquaculture development. and A. Moriwake. 1997. Effects of turbulence, salinity and light intensity on hatching and early Acknowledgments larval survival in Nassau grouper. Epinephrlus This study was supported by a grant from striatus. Journal of Applied Aquaculture 7:33-43. the George Baker Trust. We thank the Emata, A. C., B. Eullaran and T. U. Bagarinao. E 1994. Induced spawning and early life description Marine Biology and Biotechnology Labo- of the mangrove red snapper, Lufjunus urgenti- ratory, Universite de Caen (France) for pro- muculutus. Aquaculture 121:381-387. viding a traineeship to C. Manfredi, Mi- Everson, A. R. 1984. Spawning and gonadal matura- chael Feeley for technical assistance, and tion of the ehu, Efelis carhunculus, in the North- Robert Wicklund for helpful advice. We western Hawaiian Islands. Pages 128-148 in R. W. Grigg and K. Y. Tanoue, editors. Proceedings also thank the John H. Perry Foundation, of the Second Symposium on Resource Investi- the Marine Sciences and Technology Center gations in the Northwestern Hawaiian Islands, (University of Connecticut), and the Center volume 2, May 25-27, 1983. UNIHI SEA- for Marine Science Research (University of GRANT-MR-84-0 I. University of Hawaii, Hono- North Carolina at Wilmington) for support lulu, Hawaii, USA. Grimes, C. B. 1987. Reproductive biology of the Lut- in various phases of this project. janidae: A review. Pages 239-294 in J. J. Polov- ina and S. Ralston, editors. Tropical snappers and Literature Cited groupers; Biology and fisheries management. Arnold, C. R., J. M. Wakeman, T. D. Williams and Westview Press, Boulder, Colorado, USA. G. D. Treece. 1978. Spawning of red snapper Grimes, C. B. and G. R. Huntsman. 1980. Repro- (Lufjunus cumpechunus) in captivity. Aquaculture ductive biology of the vermilion snapper, Rhom- 15:301-302. boplites auroruhens, from North Carolina and Bohlke, J. E. and C. C. G. 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