Indian Journal of Geo Marine Sciences Vol. 47 (04), April 2018, pp. 839-845

Reproductive biology of blue tang fish ( Paracanthurus hepatus Linnaeus, 1776) in Khanh Hoa seawater, Viet Nam

Huynh Minh Sang * & Ho Son Lam

Aquaculture Department - Institute of Oceanography, Vietnam Academy of Science and Technology, 01 Cau Da, Nha Trang, Viet Nam *[Email: [email protected]] Received 23 August 2016 ; revised 28 November 2016

Blue tang fish ( Paracanthurus hepatus Linnaeus, 1776) is one of the most popular fish caught in Khanh Hoa seawaters for aquarium. A study on reproductive biology was conducted to evaluated the reproductive parameters including gonadal development stages, sex ratio, spawning season, fecundity and size at first sexual maturity. Results showed that, number of male and female in the nature was not significantly different. Gonadal of the fish passed through five stages of maturation. The histological screening of gonad, percentage of maturation stage and gonadal somatic index value of the fish showed all year round spawning with a peak of spawning female from April to September. Length at first sexual maturity of the fish was 149.2 mm. Fecundity ranged from 1.527 – to 20.618 ovaries/ and strongly related to weight and length.

[Key word : blue tang, Paracanthurus hepatus, reproductive biology, Khanh Hoa]

Introduction of 8 to 14 individuals. These fish reach sexual The reproductive cycles of fishes are closely tied to maturity at 9–12 months of age 3. the environmental changes particularly temperature, Increasing demand for ornamental purposes of the photoperiod and food supply 1. Reproductive blue tang fish have been affecting in the natural parameters, such as gonadal development stages, sex resource of this fish in Khanh Hoa seawater. A survey ratio, sex at first maturity, spawning season, data conducted to evaluation the natural caught of this fecundity, are of great value in fishery resource fish in Khanh Hoa has shown that total number caught management and also essential and important in per year did not exceed 1000 individual 4. Thus, there aquaculture practices. The availability of quality seeds is a great need for a suitable management strategy of and the ability to control fish reproduction are widely the natural resource of the fish as well as the strategy recognized as limiting factors in the farming of any for also breeding of this fish supporting for commercial 2. ornamental aquarium, reducing the impact on natural Blue tang fish ( Paracanthurus hepatus Linnaeus, resource. However, information available on the 1776) is a species of Indo-Pacific surgeonfish. This reproductive biology of this fish in Khanh Hoa fish is found from East Africa to Micronesia, Line seawaters is still unknown. Hence, a detail Islands and Samoa Islands, northwards to Kochi investigation on reproductive biology including Prefecture, southwards to New South Wales, gonadal development stages, sex ratio, spawning Australia. As a popular fish in marine aquarium, and season, fecundity and size at first sexual maturity was it is the only member of the Paracanthurus. The conducted and the results are presented and discussed species' range is broad, but it is common nowhere. in this paper. The fish can be found throughout the Indo-Pacific. It is seen in the reefs of the Philippines, , Material and Methods Japan, the Great Barrier Reef of Australia, New Blue tang fish was collected from the fishing boat Caledonia, Samoa, Florida, East Africa, and Sri fishing in Nha Trang bay and Spattly Island, Khanh Lanka, Vietnam. The blue tang is one of the most Hoa seawater from January 2015 to December, 2015. common and most popular marine aquarium fish all The fish boat used trammel net, diving catch to collect over the world. They live in pairs, or in small groups the fish. The size of fishes ranged from 30 to 180 mm 840 INDIAN J. MAR. SCI., VOL. 47, NO. 04, APRIL 2018

in total length. Around 30 fishes was collected each months and the monthly gonado-somatic indices (GSI). month. The number of fish collect each month is The GSI was calculated 7&8 using the formula: presented at Table 1. GSI = 100 * (GW/BW) where GW is weight of gonad The fishes was transported to laboratory at the and BW is weight of fish. Institute of Oceanography, Vietnam for analysis. At the To estimate the length at first maturity (Lm), females, laboratory the fishes were killed using ice-slurry were grouped separately into 6 mm class intervals and immersion method then weighed and measure the fish in stage III and above were considered mature. length. Reproductive gonad of the fish (testes or ovaries) Length at first sexual maturity (L m) were defined as the were then dissected and weighed for further analysis. length at which 50 per cent of all female fish having While the maturity stages of females were ovaries at advanced stage of development according to recognized based on the macroscopic appearance of King 9. The proportion of the female fish have ovaries at the ovary in the body cavity and microscopic structure advanced stage of development (P) of each size group of ova, in males only the macroscopic appearance of was adjusted by correction factor as the the biggest size testes was considered. Gonadal development stages of group was 100%. The linear relationship between size 5 fishes were determined by methods of Nikolsky and group and Ln(1-P/P) was determined and the L m was Xakun & Buskaia 6 using Olympus BX50 microscope calculated at P = 0.5. at 10 X and 40 X magnification. Sex ratio was determined by the ratio of number of Histological analysis of testes and ovary was male and female. Chi-square test was used to test the performed following the method described by Gen different between the number of male and females in et al. (2007). Ovary or testes of each gonadal the natural population of the fish. development stage of fish were dissected and fixed in To estimate fecundity, 30 ovaries in stage – IV 4% buffer formalin for 24 h. After dehydrating by were utilised. From formalin preserved ovary of passing the tissue through a series of alcohol solutions known weight, a small portion was removed and of 70, 85 and 98%, the samples were vacuum weighed to the nearest 0.001 g in an electronic embedded in paraffin. The histological sections balance and then kept in modified Gilson’s fluid 10 for (4 -5µm) were stained for general morphological two days. All the oocytes in the sample ovary were purposes with hematoxylin and eosin (H&E). The counted under binocular microscope using a counting samples were photographically analyzed and chamber. The absolute fecundity was estimated using documented using the Olympus BX 50 microscope at the formula: Absolute Fecundity (F) = (weight of 40 X magnification. ovary/weight of sample) x number of oocytes in the Spawning season of the species was determined sample. The relationship between fecundity and total based on the availability of mature and spent length and weight statically determined using the individuals in the commercial landings during different following formula: LogF = aLogX + b where F is Table 1 — Number of fish collected each month during 2015 demoted fecundity, X is total length or weight, a and Month No Month No b are constant. Relative fecundity was calculated using the following formula: S=F/W where S is Jan 30 Jul 31 Feb 30 Aug 30 relative fecundity W is fish weight (g). Mar 30 Sep 37 Apr 31 Oct 30 Results May 32 Nov 30 The maturity stages of ovary and testes of blue tang Ju 32 Dec 30 fish in Khanh Hoa was represented as in Tables 2 and 3. Table 2 — Maturity stages of female blue tang fish in Khanh Hoa Maturity stages Particular of the gonads Stage I, Immature Ovary was thin, short and glassy in appearance. It could not be distinguished ovary and testes by snake-eyes. The stages was observed in the fish size under the first maturation size. Stage II, Maturing Ovary developing, ovary and testes can be distinguished by snake-eyes. Ovaries are opaque and creamy yellow. Stage III, Mature Ovaries increase the size comparing to stage II. Ovaries are reddish yellow, extending about 2/3 body cavity length. Stage IV, Ripe/Oozing Ovaries are yellow to amber colored filling the entire body cavity, extending in the entire body cavity length Stage V, Spent Ovaries are rather flaccid, reddish yellow. SANG & LAM et al .: BIOLOGY OF BLUE TANG FISH ( PARACANTHURUS HEPATUS LINNAEUS, 1776) 841

The histology of ovaries and testes of the blue tang V was higher during the priod from March to August fish in Khanh Hoa are presented as Figs. 1 and 2. than that during the period from September to Ratio of male and female of blue tang fish in February (Fig. 3). Percentages of advance stage of Khanh Hoa seawaters was 1:1,07. Number of male ovaries (IV and V) in July was the highest (81 %) and and female was not significantly different ( χ2 = 0, the lowest was in January 47 (%). 45 < 3, 845 ( df = 1, P < 0,05 )). GSI of the female blue tang fish in Khanh Hoa The fishes at mature (III) and ripe stages (IV) of seawater was highest in March (0,65 ± 0,24), and ovaries presented all year round. However, lowest was in October (0,22 ± 0,08). For the male percentages of fish at maturation stages of III, IV and blue tang fish, the highest GSI was in February

Fig. 1 — Histological sections of ovaries of the blue tang fish in Khanh Hoa Note: A, B, C & D is the histological section of the ovaries at II, III, IV & V maturity stage, respectively; Evtg: early vitellogenic oocyte; AVtg: advanced vitellogenic oocyte; PG: primary growth oocyte; y: yolk vesicles; n: nucleus. 842 INDIAN J. MAR. SCI., VOL. 47, NO. 04, APRIL 2018

Fig. 2 — Histological images of the testes of of the blue tang fish in Khanh Hoa Spc: spermatocytes; Spm: spermatids; Spz: spermatozoa; Sc: Sertoli cells; L: seminiferous lobule; It: interstitialtissue. Table 3 — Maturity stages of male blue tang fish in Khanh Hoa Maturity stages Particular of the gonads Stage I, Immature Testes was thin, short and glassy in appearance. It could not be distinguished ovary and testes by snake-eyes. The stages was observed in the fish size under the first maturation size. Stage II, Maturing Testes start developing, ovary and testes can be distinguished by snake-eyes. Testes are moderately thick, flattened and white. Stage III, Mature Testes increase the size comparing to stage II. Testes are flat, well-developed and creamy white, extending about 2/3 body cavity length Stage IV, Testes are very thick, flat, turgid and creamy, extending in the entire body cavity length Ripe/Oozing Stage V, Spent Testes are sunken (0,22 ± 0,13) to April (0,22 ± 0,1), and the lowest GSI The length of the first sexually maturity of the blue tang fish in was observed in October (0,14 ± 0.04) (Fig. 4). Khanh Khoa seawater was counted at 149.2 mm (Fig. 5). SANG & LAM et al .: BIOLOGY OF BLUE TANG FISH ( PARACANTHURUS HEPATUS LINNAEUS, 1776) 843

100 The absolute fecundity of the blue tang tang fish in 90 Khanh Hoa varied from 1.527 – to 20.618 80 ovaries/individual with an average of 9.983 ± 6.026 ovaries/individual. Relative fecundity of the fish 70 varied from 28 to 92 with an average of 60 67 ± 19 ova/gram of females fish. The relationship 50 Stage V Stage IV between fecundity and the length and weight of fish 40 Stage III was presented as in Fig. 6 and 7. 30 Stage II Stage I 20

Percentage (%) Percentage Discussion 10 Understanding of the reproductive biology of fish 0

… is necessary for fishery resource management and

July aquaculture practices. This is the first attempt to May June April March August Septem January October February December Month November 5

Fig. 3 — Monthly percentages of maturation stages of blue tang fish 4.5 100% 90% Male 4 80% 70% Log F Log 60% 3.5 50% y = 4.581x - 6.581 GSI % GSI 40% R² = 0.935 3 30% 20% 10% 2.5 0% 2.1 2.2 2.3 2.4 2.5 … … … Log (TL) July May June Dece April Nove Septe March

August Fig. 6 — Fecundity - total length relationship of the blue tang fish January October February Month in Khanh Hoa

Fig. 4 — Monthly change of the GSI of blue tang fish in Khanh Hoa 4.5 y = 1.535x + 0.683 2 4.3 R² = 0.913 1.5 4.1 y = -0.053x + 7.908 3.9 1 R² = 0.922 3.7 0.5 3.5 Log F Log Length (mm) 3.3 0 3.1

Ln(1-P)/P 110 130 150 170 190 -0.5 2.9

-1 2.7 2.5 -1.5 1.5 2 2.5 -2 Log BW

Fig. 7 — Fecundity - total weight relationship of the blue tang fish Fig. 5 — Groups of size relationship and Ln ((1-P) / P) of the blue in Khanh Hoa tang fish in Khanh Hoa

844 INDIAN J. MAR. SCI., VOL. 47, NO. 04, APRIL 2018

investigate some reproductive parameters of the blue (9.234-10.988) Thalassoma hardwicki (4.600-8.743) tang fish. In this study, the gonad of the blue tang fish và Chaetodon octofasciatus (1.060-2.879) 15 ; and was divided into 5 stages of maturity. This is lowest than Chaetodon collare (2.763-31.065) and normally observed in the tropical fish having the year Parupeneus bifasciatus (2.968-146.373) 15 . Similar to round reproduction cycles. At mature or ripe stages, other fish, fecundity of the blue tang fish in the beside the main component oocytes (oocyte at early current study is positive correlated to total length. vitellogenic and advanced vitellogenic stage), the This finding suggests that total ovaries in a spawning primary growth oocytes also exist at the considerate season depend on the fish size 16 . number. This is the evidence that blue tang fish Sex ratio of the blue tang fish in the current study was spawn continuously during the spawning season. In approximate 1:1. The result is in consistent with other addition, the data on the changes in percentage of fish such as Acanthlinis leucosternon 15 . However, the maturity stages and GSI in the current study suggests ratio is diffent to others species such as A. triostegus that, blue tang fish in Khanh Hoa spawn all year Chaetodon collare; Plectorhinchus orientalis; round with a peak season from April to September. Thalassoma hardwicki 15 . This results is consistent with others studies on The length at sexual maturity of the blue tang fish tropical marine fishes. Fishes in estuary and coastal in Khanh Hoa seawater in the current study is larger seawater all most spawning year round and have one than that of two other fish belonging to family peak spawning season 11&12 . The peak spawning : Acanthlinis leucosternon (101 -120 cm) season of the blue tang fish in Khanh Hoa is similar and A. triostegus (71-100 cm) 15 . This may due to the to the anemone fish ( Amphiprion sp )13 and in species characteristics and the maximum size as well contrast with sliver sillago ( Sillaga sihama ) (from as the life cycle of the fishes. December to April) 14 . According to Vijay Anand and Pillai 15 the peak spawning season of some species Conclusion belonging to family Acanthuridae is different with The present study reveals that blue tang fish in the blue tang fish in the current study. Acanthlinis Khanh Hoa seawater spawns year round which peak leucosternon , A. triostegus, Chaetodon collare, season from April to September, length at first sexual Plectorhinchus orientalis, Parupeneus bifasciatus maturity of the fish is 149.2 mm. Fecundity ranged have peak spawning season from September to from 1.527 – to 20.618 ovaries/ and strongly related April, November to May, February to April, to weight and length. The currently findings provide December to May and September to April, the scientific foundation for the purpose of fishery respectively. The different in peak spawning season resource management and artificial breeding of the and of the different fish species may due to the blue tang fish. species biology and environmental condition. Fecundity of fishes is usually determined from the Acknowledgments number of ova of the mature group in the ovary. In The authors are grateful to Ms. Nguyen Tuong Vy, the present study, fecundity of Paracanthurus Ms. Phan Thi Ngoc for contributing to sample collection hepatus , was determined from the examination of and analysis. This work is finacially supported by 30 specimens. In the present study, fecundity showed Vietnam Academy of Science and Technology (VAST) high correlation coefficient with the total length of the under the project number VAST06.04/15-16. fish. The regression of fecundity and total length can be expressed as Log F = 4.581*Log (TL) – 6.581 with References R2 value was 0.935. The regression of fecundity and 1 Baganal T B, Aspects of fish fecundity. In: Ecology of freshwater fish production (Welly, Newyork) 1978, pp. 75-101. body weight can be expressed as Log F = 1.535*Log 2 2 Shamsan, E. F. and Z. A. Ansari (2010). Studies on the (BW) + 0.683 with R value was 0.913. The absolute reproductive biology of Indian Sand Whiting Sillago sihama fecundity of blue tang fish in Khanh Hoa seawater is (Forsskal). Indian J. of Mar. Sci. , 39 (2010), 280-284. equivalent to the fecundity of other aquarium fish 3 McIlwain, J., Choat, J. H., Abesamis, R., Clements, K.D., such as Chaetodon trifasciatus (1.984-21.975) and Myers, R., Nanola, C., Rocha, L. A., Russell, B., and 15 Stockwell, B., The IUCN Red List of Threatened Species 2012. C. melannotris (1.492-24.532) . By contrast, this 4 Sang H M,. Evaluation on the exploitation status of blue tang value is higher than other fish such as Thalassoma fish in Khanh Hoa seawaters. Final report. Project number lunare (3.342-10.360); Parupeneus barberinus VAST06.04/15-16 2016 SANG & LAM et al .: BIOLOGY OF BLUE TANG FISH ( PARACANTHURUS HEPATUS LINNAEUS, 1776) 845

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