Hermaphroditism in the white spot grouper Epinephelus coeruleopunctatus (Pisces: Serranidae) harvested from Padang City waters, Indonesia

Introduction

Groupers (family Serranidae) belong to 109 species and 11 genus^1,2. Groupers are commercial marine fishes that have been harvested intensively from the wild, resulting in decreasing the population worldwide^3,4. The white spot grouper, Epinephelus coeruleopunctatus, is one of the most popular groupers and has a high economic value among groupers in Asia-Pacific regions^5,6. However, this species is rare and difficult to catch. According to local fishermen of Padang City, Indonesia, the population of E. coeruleopunctatus has been declining sharply over the last two decades⁷. According to Teixeira et al.⁸ and Mariskha and Abdulgani⁹ the decreasing fish population is caused by overfishing, habitat perturbation¹⁰ and unfriendly fishing practices¹¹. The International Union for Conservation of Nature¹² reports this species on the Red List as a threatened species.

Culturing of white spot grouper has been initiated in Indonesia; however, the fry (juveniles) are strongly dependent from the wild supply¹³. Therefore, it is very crucial to develop breeding technology of the white spot grouper. One of the problems in the development of breeding technology is hermaphroditism sex development, which is observed in this species¹⁴. Therefore, it is difficult to determine the sex differentiation between male and female. Hermaphroditism has also been reported in several other groupers, such as E. tauvina¹⁵, E. aeneus¹⁶, E. rivulatus¹⁷, E. striatus¹⁸, and Plectropomus laevis¹⁹. Hence, this paper reports on the size (length and body weight) of sex transformation in white spot grouper. This information is crucial to plan a better management strategy of fishery resources²⁰ and to develop breeding technology for the white spot grouper.

Methods

All procedures involving animals were conducted in compliance with Bung Hatta University Research and Ethics Guidelines, Section on Animal Care and Use in Research. Fish were caught from Padang City waters, at GPS coordinates 0⁰ 54’ 55.34” S, 100⁰ 10’ 15.49” E (Figure 1), between April and October 2013. The fish were caught using hooks and hand line at the depth of 30–50 m. Fishing operations were carried out from 6.00 am to 16.00 pm. The sampled fish were anesthetized with MS222, prepared by dissolving 4g of MS222 in 5L tap water²¹ and then transported to the Laboratory of Fisheries Resources of Bung Hatta University for further analysis. In the laboratory, the fish samples were measured for total length (mm) and body weight (g). The abdomen was dissected and the gonad was removed carefully and cleaned using a tissue paper and then weighed nearest to mg using a digital balance (ACIS: AD300; errors 0.01g). Sex differentiation by gonad was examined microscopically (100x magnification) and determined based on Muchlisin et al.²². The data were analyzed descriptively.

Figure 1. A map of Padang City waters showing the sampling location (red circle)⁷.

Results

A total of 56 fish were recorded during the study, where 50 fish were recognized regarding sex differentiation by gonad, of which 22 were males and 28 females. A total of 6 samples were not recognized regarding their sex, due to being still in the early gonadal development stage. The sex ratio was 2:3 (male:female). The total length of the male fish ranged from 302–537 mm, while females ranged from 183–537 mm. The body weight ranged between 374–2107 g and 85–373 g for male and female fish, respectively. The total length of fish with undetermined sex ranged from 125–242 mm and 85–373 g body weight (Table 1 and Table 2).

The study showed that the first sex differentiation of E. coeruleopunctatus occurred at a size above 183 mm; fish of this size were recognized as female and no male fish were detected in this size group. First sex differentiation is species dependent; for example, E. bleekeri occurrs at 170 mm²³ and Plectropomus laevis at 280 mm¹⁹.

The results revealed that the female white spot grouper begun to transform to male at 302 mm in length, indicating a protogynous hermaphroditism. However, the size at which all fish transform to male fish was unknown, since there were no fish sample more than 537 mm in length. But, the existing data show that the ratio of male fish was increased as total length increased; hence, we suspect that all fish have changed sex to male at sizes above 600 mm. For comparison, Renones et al.²⁴ reported that the female dusky grouper E. marginatus transforms its sex initially from female to a male at a size of 680 mm and all males were detected at size 800 mm. In addition, Tan and Tan²⁵ reported that E. tauvina begins to transform their sex from female to male at the size of 650 mm, while at the size of 700 mm all fish are recognized as male. According to Burhanuddin and Fami²⁶ the occurrence of sex transformation in hermaphroditic fish is species dependent and strongly influenced by environmental factors.

Conclusions

The white spot grouper Epinephelus coeruleopunctatus is a protogynous hermaphroditism. Sex differentiation was detected at the total length of 183 mm and at this size the fish are female. The sex transformation began to occur at 302 mm total length.

Data availability

Dataset 1: The total length, body weight and sexes of the 56 individual fish sampled. doi, 10.5256/f1000research.11090.d155119²⁷