Reproductive Biology of the King Angelfish <I>Holacanthus Passer</I

BULLETIN OF MARINE SCIENCE, 65(3): 677–685, 1999

REPRODUCTIVE BIOLOGY OF THE KING ANGELFISH HOLACANTHUS PASSER VALENCIENNES 1846 IN THE GULF OF CALIFORNIA, MEXICO

Marcial Arellano-Martínez, Bertha P. Ceballos-Vázquez, Federico García-Domínguez and Felipe Galván-Magaña

ABSTRACT Aspects of the reproductive biology of Holacanthus passer, a valuable ornamental fish, were studied. Male and female specimens were collected monthly from June 1992 to May 1993 in the Gulf of California. The sex ratio differed significantly from 1:1 over the size range of the sample; females prevailed at small lengths and males at larger lengths. The ovarian and testes development was analyzed by histological techniques and the reproductive cycle was determined. H. passer is a partial spawner with asynchronous development of the gonads. The period of reproductive activity was from April to No- vember coinciding with the highest values of gonadosomatic index and temperature. The gonadosomatic index adequately describes the reproductive activity of the species.

The king angelfish Holacanthus passer V., ranges from the central Gulf of California to Ecuador and the Galápagos Islands (Gotshall, 1982). Their juveniles are caught in the Gulf of California for sale to aquaria because of their great color pattern, yielding prices as high as US $100 each in the international market (Pérez-España and Abitia-Cárdenas, 1996). Despite their importance in the aquarium industry, there are no studies on their population biology or the impacts of exploitation and studies on their biology are scarce (Pérez-España and Abitia-Cárdenas, 1996). The fishery for H. passer juveniles is presently prohibited because their excessive exploitation caused the depletion of the populations. An alternative for preserving economic benefits is the culture of king angelfish. Past attempts to culture this species have yielded poor results. Knowledge of the reproductive biology may help in the development of angelfish culture. Observations on the ecology and social organization of H. passer in the Gulf of Cali- fornia were reported (Reynolds and Reynolds, 1971). Studies on the food habits and feeding behavior (Reynolds and Reynolds, 1971; Pérez-España and Abitia-Cárdenas, 1996), and a macroscopic description of the digestive tract (Pérez-España and Abitia- Cárdenas, 1996) have been conducted. The reproductive biology of H. passer is undescribed. The objective of this study was to examine the gonadal development and the timing of reproduction of this species in relation to the gonadosomatic index and water temperature.

METHODS

The study was carried out at Cueva de León (24°02'N, 110°24'W) in the Gulf of California, Mexico. From June 1992 to May 1993, adult specimens of H. passer were collected monthly with a Hawaiian harpoon at 2 to 10 m depth between 09:00 and 14:00. Standard length and total weight were recorded for each fish. The water temperature was recorded at the time of sampling.

677 678 BULLETIN OF MARINE SCIENCE, VOL. 65, NO. 3, 1999

Gonads were dissected, weighed, and fixed in 10% formalin solution. Gonad sections were dehy- drated in alcohol and embedded in paraffin. Sections (7 µm) were placed on slides and stained with haematoxylin and counterstained with eosin (Humason, 1979). A modification of the developmen- tal stages established by Ceballos-Vázquez and Elorduy-Garay (1998) for the golden-eyed tilefish Caulolatilus affinis Gill was used to categorize the gonads. Sex ratios were analyzed by month, and by length class, with a χ2 test (α = 0.05) for the signifi- cance of the deviation from the expected ratio (1:1).

The gonadosomatic index (IG) was calculated with the equation: × IG = Gonad weight (g)/Total weight (g) 100

In order to make a quantitative comparison of IG results with histological results, a monthly gonad index (Ig) was computed for each sex (Heffernan et al., 1989) utilizing a numerical grading system with 1 = resting and spent, 2 = developing, and 3 = ripe and spawning. A correlation analysis between IG and Ig was done to determine if the IG is an accurate predictor of specific reproductive condition. A linear correlation analysis was used to investigate the relationship between gonadosomatic index and temperature. Correlation analyses were carried out with all the specimens caught throughout the annual cycle (Encina and Granado-Lorencio, 1997).

RESULTS

A total of 200 specimens was collected, 114 females (55.9%), 86 males (42.1%); and four immature (2%). The sex ratio for the total sample was 1.32F:1M and differed significantly (P ≤ 0.05) from the expected ratio of 1:1. The analysis by month shows that only in October there was a significant difference (P ≤ 0.05) in sex ratio (Table 1). Fishes ranged in standard length from 81 mm to 253 mm (mean = 177.8, 37.6 SD). The analysis of sex ratios by length class, carried out on all the data, shows significant deviations from the expected ratio of 1:1 in seven length classes (P ≤ 0.05) (Table 2). It was found that nearly all fish >200 mm are males. Gametogenesis, either spermatogenesis or oogenesis, of H. passer was divided into five stages (resting, developing, ripe, spawning, and spent) (Table 3). The reproductive

(erauqsihC,seicneuqerfelamdnaelameF.1elbaT χ2 fosoitarxesdnaseulav) ressapsuhtnacaloH b P(oitar1:1amorfecnereffidtnacifingisyllacitsitatsaetacidni*.htnomy ≤ .)50.0

M htno Feelame Malχ2SexratioF:M J767une 07.071:1.1 J5uly 151501.121: A60ugust 111:0. 6 September170 03.55 61:1.4 O5ctober24154.733 *1:6.2 November180 05.22 21:1.2 D5501ecember 1: J6312anuary 1: February30301: March 1551 22.21:2. A72pril 1618.311:0.5 May 911202.1:0.8 T4OTAL1618*31.921.32: ARELLANO-MARTÍNEZ ET AL.: REPRODUCTIVE BIOLOGY OF KING ANGELFISH 679

(erauqsihCdnaseicneuqerfelamdnaelameF.2elbaT χ2 foseulav) ressapsuhtnacaloH htgnelyb P(oitar1:1amorfecnereffidtnacifingisyllacitsitatsaetacidni*.ssalc ≤ .)50.0

S)htgneldradnat (emmFeemalMlalTotaχ2 80−90 12330.33 90−100 21330.33 100−110 21330.33 110−120 1120 120−130 52761.28 130−140 61713.57 140−150 831132.27 150−160 1286 1*10.889 160−170 3451 3*20.828 170−180 2406 3*16.133 180−190 1451 173.26 190−200 35850. 200−210 333 210−220 14151*11.267 220−230 12232*19.174 230−240 100101.* 240−250 666.* 250−260 111

Table3.DescriptionofthedevelopingstagesofthegonadsofHolacanthuspasser.

SetagesFeemal Mal ReestingOocyteswereembeddedinfinger-likLittleornospermatocyte fyolds,thepredominantoocyteswereearldevelopmentpresent.Spermatogenic alndprevitellogenicoocytes.Gonadatubules,ingeneral,wereinactive. lumenwasgenerallylarge. DsevelopingLargeearlyandprevitellogenicoocyteIntensespermatogenicactivityin wereinlesserquantities.Thevitellogenictshetubuleswithcellsinallstage aendmatureoocytesweredominant.Thofdevelopment.Spermatozoa lumenwassmallerthanatthepreviouscollectinginspermatogenictubules. stage. ReipeThematureoocyteswerethemorThespermatozoawaspredominant representativeones.Prehydratedandwithlittleornonespermatogenic hydratedoocyteswerepresentinsomeactivityoccurring.Thecollecting ovaries.Therewasnolumenvisible.tubulesweretotallyfilledwith spermatozoa. SrpawningThegeneralappearancewasverysimilaChannellingofspermatozoainto toripeovariesbutthedistinctivecollectingtubules.The characteristicofthisstagewasthespermatogenicandcollecting presenceofpostovulatoryfollicles.tubuleswerepartiallyempty. S.pentTheabundanceofearlyoocytesincreasedTubulesalmostempty,withsome Thevitellogenicandmatureoocyteswereresidualspermatozoa.Some inreabsorption.Theatreticstructureswerespermatogenesismayoccur. dominant,sothatthegonadcouldbe consideredinreabsorption. 680 BULLETIN OF MARINE SCIENCE, VOL. 65, NO. 3, 1999

Figure 1. Reproductive cycle of (a) females and (b) males of Holacanthus passer. Relative frequency of gonadal stages between June 1992 and May 1993. cycle of H. passer from Cueva de León, B.C.S., is summarized in Figure 1. From Novem- ber to May most fishes were inactive, as determined by the dominance of the resting and spent stages. The developing stage (both sexes) and the ripe stage (males) were present in this period from March to May, indicating that the reproductive activity started in March. Ripe and spawning females were present from June to October, whereas ripe and spawning males were found from April to November. Monthly quantitative assessments of histologic reproductive condition are illustrated in Figure 2. From these data, it is apparent that the gonad index of both, female and male, have a similar tendency along the year, with high values coinciding with reproductive activity. The values of Ig were lowest during the end of autumn and winter then, by spring Ig started to increase reaching the highest values in summer and early autumn. For males, a decrease in Ig values was in summer but Ig values increased again by autumn. The Ig ARELLANO-MARTÍNEZ ET AL.: REPRODUCTIVE BIOLOGY OF KING ANGELFISH 681

Figure 2. Monthly gonad index values throughout the year for females and males of Holacanthus passer.

values indicated that spawning started in summer and continued into the early autumn, with fish quiescent by the late autumn and winter. The mean values of gonadosomatic index were low from October to May, except in April for males when there was a considerable increase coinciding with ripe individuals. In June, females index reached the highest value, and tended to decrease in the following months (Fig. 3). For females a significant correlation (P < 0.05) was found between gonad index and gonadosomatic index, whereas for males a significant correlation (P < 0.05) wasn’t found (Table 4). From December to April, the water temperature was minimum reaching the lowest values (20.5°C) in January and April. In May, the water temperature started to increase, reaching its highest values (30°C) in July and September, coinciding with reproductive activity (Fig. 4). For both sexes, gonadosomatic index and temperature were positively correlated. But only for females was a significant correlation (P < 0.05) found between gonadosomatic index and temperature (Table 4).

dna)gI(xednidanog,)GI(xednicitamosodanogrofxirtamtneiciffeocnoitalerroC.4elbaT elamdnaelamefrofdetaluclac)T(erutarepmet .ressapsuhtnacaloH n = etacidni*.eziselpmas P(noitalerroctnacifingisyllacitsitatsa ≤ .)50.0

Feelame Mal (n=1n14)(=86)

IG IG I*g 06.850.4 T*07.730.5 682 BULLETIN OF MARINE SCIENCE, VOL. 65, NO. 3, 1999

Figure 3. Mean values of gonadosomatic index throughout the year for (a) females, and (b) males of Holacanthus passer.

DISCUSSION

The sex ratio for H. passer differed significantly from 1:1 for the whole sample, with a dominance of females, but the ratio varied by month. The significant difference for the total sample may reflect the great proportion of females encountered in October. Sex ratios by length class showed significant deviations in seven classes, the three small ones favoring females and the other four favoring males. Differences in sex ratios where females prevail at small lengths and males prevail at larger lengths have been reported for other pomacanthids, like Centropyge interruptus (Moyer and Nakazono, 1978). These differences in the sex ratio have been attributed, among other factors, to either a differential distribution of a fraction of the population or to a greater survival of males (Moyer and Nakazono, 1978; Moyer et al., 1983; Aranis and Torres, 1987; Elorduy-Garay and Ramírez-Luna, 1994). There has also been argument for evidence of protogynous sex change (Aranis and Torres, 1987). ARELLANO-MARTÍNEZ ET AL.: REPRODUCTIVE BIOLOGY OF KING ANGELFISH 683

Figure 4. Values of water temperature at Cueva de León, B. C. S., México from June 1992 to May 1993.

Sex change is common among reef fishes (Hourigan and Kelley, 1985) and ten families are protogynous species (Warner, 1978; Policansky, 1982). Protoginy has been described for two genera of pomacanthids: Centropyge (Moyer and Nakazono, 1978; Bruce, 1980; Aldenhoven, 1984) and Genicanthus (Shen and Liu, 1976; Susuki et al., 1978; Carlson, 1982). In the present study, no histological evidence of protogyny was encountered. The characteristics of gametogenesis in H. passer were similar to those described for Caulolatilus affinis (Ceballos-Vázquez and Elorduy-Garay, 1998). The ovaries of H. passer have oocytes at different stages of development simultaneously, common for fishes with partial or multiple spawning. Additionally, late postovulatory follicles and atresia charac- teristic of a spent stage were present in ovaries with oocytes in a clear developing stage, which suggests that H. passer is a partial spawner. According to Thomson et al. (1979), the reproduction of H. passer occurs in late summer, but in our samples the reproductive activity occurred from late summer to early winter. The use of the gonadosomatic index as an indicator of reproductive activity has been discussed by De Vlaming et al. (1982). Its utility to detect hydrated ovaries due to the enormous increase in weight has been established by Hunter and Macewicz, (1985), thus gonadosomatic indexes provide useful estimates of duration of spawning (Ceballos-

Vázquez and Elorduy-Garay, 1998). The usefulness of the IG as a means for determining

reproductive condition is limited since similar IG values may be determined for two different stages of gonad development (e.g., resting and spent) because of the gonad have

similar weights in both stages. The IG does not give exactly information about the gonad development stage but it gives good information about the annual trend in the reproductive activity of the population. In H. passer, the annual trend in the mean monthly values of female gonadosomatic index generally agrees with the reproductive activity and with histological results. This was evident because of the significantly positive correlation obtained between female

values of IG and Ig. Therefore, the monthly trends in gonadosomatic index are predictive in comparison to reproductive condition, and the gonadosomatic index adequately repre- 684 BULLETIN OF MARINE SCIENCE, VOL. 65, NO. 3, 1999

sents the main period of reproductive activity of female H. passer (June to November). In

the case of males, the correlation between IG and Ig was not significant; therefore gonadosomatic index does not represent the reproductive activity in males. This may be explained by the low weight that the male gonads reach during the maturation. Temperature is one of the most important environmental factors in the regulation of fish reproduction (Moyle and Cech, 1988). Temperature has a pronounced effect on spawning and on the rate of gonadal development in fish (Bye, 1990). The reproductive cycle of female H. passer shows a clear seasonality related to the water temperature since there is a significant positive correlation between IG and temperature. A similar relationship between temperature and gonadal activity has been observed for tilapia (Zohar, 1989). For other fishes like Mugil cephalus, Dicentrarchus labrax, and Sparus aurata, gametogenesis and temperature are inversely related (Zohar, 1989). In H. passer the inactive period occurs from December to March, with lowest values of water temperature (20.5° to 24°C). Gametogenesis commenced when temperature started to increase and continued during the warmer months (27° to 30°C). In some fishes sud- den increases in water temperature appear to be the final cue for stimulating maturation and ovulation (Bye, 1990) whereas cooler temperature inhibits gametogenesis. In females, spawning occurs with water temperatures over 28°C, whereas for males it occurs over the 24°C. For most species, spawning occurs only within a relatively narrow temperature range (Bye, 1990).

ACKNOWLEDGMENTS

We are grateful to Dirección de Estudios de Postgrado e Investigación del Instituto Politécnico Nacional for funding this work. To H. Pérez-España for helping us with the sampling. We acknowl- edge the fellowships of Programa Institucional de Formación de Investigadores and CONACyT to M. Arellano-Martínez and the Comisión de Operación y Fomento de Actividades Académicas pro- vided to F. García-Domínguez and F. Galván-Magaña. Thanks to E. Glazier for editing the English- language text.

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DATE SUBMITTED: July 17, 1998. DATE ACCEPTED: February 22, 1999.

ADDRESSES: Centro Interdisciplinario de Ciencias Marinas, Apdo. Postal 592, 23000, La Paz, B. C. S., Mexico. CORRESPONDING AUTHOR: (M.A.-M.) Tel.: (112) 2 53 44; fax: (112) 2 53 22; email: .