SIZE AT FIRST MATURITY AND FECUNDITY OF Auxis spp. FROM WEST COAST OF SUMATERA AND SOUTH COAST OF JAVA, EASTERN INDIAN OCEAN

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1 SIZE AT FIRST MATURITY AND FECUNDITY OF Auxis spp. FROM WEST COAST OF SUMATERA AND SOUTH COAST OF JAVA, EASTERN INDIAN OCEAN Prawira A.R.P. Tampubolon, Dian Novianto, Irwan Jatmiko Research Institute for Tuna Fisheries ABSTRACT From The 6 th Working Party on Neritic Tuna (WPNT), last year, Indonesia was requested to present the result of the latest research about the reproduction aspect of Auxis spp. held by Research Institute for Tuna Fisheries (RITF). This research used wider size range to estimate the size at first maturity than the presented research in the last WPNT. The aims of this research were to disclose size-of-first-maturity and fecundity of Auxis spp. caught by purse seine from west coast of Sumatra and south coast of Java, eastern Indian Ocean. From this study, the reference point of the worth catching fish size can be revealed. The study was held from January until December 2016 in four locations, two locations from IFMA 572 (Lampulo and Sibolga) and IFMA 573 (Sendangbiru dan Cilacap). The size at bullet tuna (Auxis rochei) and frigate tuna (Auxis thazard) were cmfl, and cmfl respectively. Some of the fish, for further analyzed, were dissected to find out the sex and gonadal maturity. The size at first maturity was determined using logistic curve approach when 50% of the fish populations were already mature. The size at first maturity of bullet tuna was cmfl and the frigate tuna was cmfl. The eggs of the fishes were also counted. The fecundity of bullet tuna was eggs. While, the fecundity of frigate was eggs. Key words: Neritic tuna, size at first maturity, fecundity, Auxis thazard, Auxis rochei, Eastern Indian Ocean. INTRODUCTION In the 6 th Working Party on Neritic Tunas, the delegation of Indonesia, from Research Institute for Tuna Fisheries (RITF), presented a paper entitled Size Distribution and Reproductive Aspects of Auxis spp. from West Coast Sumatera, Eastern Indian Ocean. 1

2 This paper provided an analysis of size and maturation of Auxis spp. WPNT appreciated the result and encouraged to extend the size range of the samples. WPNT also requested Indonesia to present the result of purse seine fishing vessel research related to this field which was held in 2016 (IOTC 2016). Purse seine fisheries in Indonesia are consisted of two types, which are small pelagic and large pelagic purse seine. The difference of them is on the mesh size and fishing area. In both types of the purse seine, also found the catch of neritic tunas, which are kawakawa, bullet tuna, frigate tuna. Although the catch of the neritic tunas was lesser than skipjack tuna and scads, but the information about the biological condition of these resources was still important to be understood. Auxis was distributed throughout the tropical and subtropical waters. Auxis is the most abundant species in the Mediterranean Sea and the most widely exploited fish on a small scale tuna fisheries (Sabates & Recasens 2001). To ensure the sustainability of this commodity, the reproduction aspects have to be revealed. Research on the reproductive biology of fish can provide critical data and information regarding the frequency of spawning, spawning success, spawning duration and the size at maturity (Mardlijah & Patria, 2012). The aims of this study were to reveal the size-of-first-maturity and fecundity of Auxis rochei and Auxis thazard. METHODS The fish were collected from four spots along the west coast of Sumatera (IFMA 572), which were Lampulo (Aceh) and Sibolga (North Sumatera) and south coast of Java (IFMA 573), which were Pacitan (East Java) and Sendangbiru (East Java). It was held from January 2016 to December The fish were caught using purse seine armadas which were operated in eastern Indian Ocean. The data collecting included fork length, weight of the whole body, and gonadal aspects. Gonad samples were preserved and analyzed in Histology Laboratory of Research Institute of Tuna Fisheries. Female gonadal maturity stage was observed histologically based on the oocyte development criteria, which is classified the maturity of 2

3 female gonad into five stages. (Appendix 1); while the gonadal maturity of the male fish was analyzed morphologically. Size at First Maturity Size at first maturity is defined as length or weight at maturity. Maturity is defined as minimal size attained at maturity or the size at which 50% of the fish at that size are mature (Froese & Pauly 2017). The size at first maturity was determined by the size when 50% of the fish population reached sexual maturity (L m 50) using General Linear Model with family = binomial (logistic model). In this study, statistical analysis using R software version (R Core Team, 2016). Fecundity Total fecundity is counted by using the sub-sample method of gonad weight or called gravimetric method. The whole gonads were taken out from the mature female fish and weighed. Then, the gonads preserved using 10% formalin solution. The sub-samples were taken from the whole gonad and weighed. The eggs then separated, placed on a petri dish, and filtered using a 1,000-micron sieve. The retained eggs on the sieve were placed on a bogorov plate and washed with 70% alcohol solution to be observed under a microscope and counted the number of eggs. The estimation of fecundity based on the formula of Bagenal (1978) as follows: Where : F = Fecundity (eggs); Wg = Total gonad weight (gram); Ws = Sample gonad weight (gram); n = The eggs in the sample gonad (eggs) F = W W n 3

4 RESULT Size at first maturity During the study, the amont of bullet tuna and frigate tuna which were dissected fir analyzing the reproduction were 404 and 443 fish. The bullet tunas were consisted of 117 males, 132 females and 155 unidentified; whereas the frigate tunas were 245 males, 194 females dan 4 unidentified one. The unidentified fish were ones who can t be determine the sex because the gonad is thread-like shape and too small to be identified visually Individually, the smallest bullet tuna which had reached maturity was 22 cmfl (Figure 1), while for frigate tuna was 21.5 cmfl (Figure 2). But, according to the logistic curve, the size at first maturity for bullet tuna and frigate tuna population were cmfl (Figure 3) and cmfl (Figure 4). This study used wider range of size, broader distribution and more sample than Tampubolon et al. (2016). A. rochei and A. thazard from Tampubolon et al. (2016) were cmfl and cmfl, respectively. Whereas, the range size at A. rochei and A. thazard in this study were cmfl and cmfl. The size at first maturity for A. rochei and A. thazard from Tampubolon et al. (2016) were bigger than this research: 27.16cmFL and 34,89 cmfl. 100% Percentage (%) 80% 60% 40% 20% 0% TKG V TKG IV TKG III TKG II TKG I Mean Length (cmfl) Figure 1. Bullet tuna gonado somatic index (GSI) based on the length 4

5 Persentage (%) 100% 80% 60% 40% 20% 0% GMS TKG V GMS TKG IV GMS TKG III GMS TKG II GMS TKG I Mean length (cmfl) Figure 2. Frigate tuna gonado somatic index (GSI) based on the length Fork length Figure 3. Logistic curve model to determine the Lm 50 of bullet tuna Mature fish proportion Mature fish proportion Fork length Figure 4. Logistic curve model to determine the Lm 50 of frigate tuna 5

6 Fecundity The fecundity was counted from the mature female fish. The fecundity of bullet tuna was eggs and the diameter of the mature eggs were µm. While, the fecundity for frigate tuna was eggs and the diameter of the eggs were µm. The size of the egg grows larger as the egg matures. Size range The size range of bullet tuna caught by purse seine for this study were cmfl at IFMA 572 and cmfl at IFMA 573 (Figure 5). Whereas, the size range of frigate tuna were cmfl (IFMA 572) and (IFMA 573) (Figure 6). Frequency (Ind) Figure 5. Size distribution of bullet tuna caught by purse seine in IFMA 572 and IFMA 573 Frequency (ind) IFMA IFMA Length (cmfl) Length (cmfl) Frequency (Ind) Frequency (ind) Figure 6. Size distribution of frigate tuna caught by purse seine in IFMA 572 and IFMA IFMA IFMA Length (cmfl) Length (cmfl)

7 Based on the size at first maturity, the bullet tuna that were caught by purse seine in IFMA 572 and 573 were dominated by juvenile fish. Whereas, the frigate tuna caught by purse seine in IFMA 572 were dominated by juvenile fish; while in IFMA 573 is dominated by the adult one. CONCLUSION The size at first maturity of bullet tuna was cmfl and for frigate tuna was cmfl. The fecundity of bullet tuna and frigate tuna was eggs and respectively. REFERENCES Bagenal, T.B Methods for assessment of fish production in fresh water. IBP. Handbook (3). Blackwell Scientific Publication, Oxford. 253pp. Froese R.& Pauly D.. Editors FishBase. World Wide Web electronic publication. version (02/2017). [IOTC] Indian Ocean Tuna Commission Report of the 6 th Session of the IOTC Working Party on Neritic Tunas. Seychelles, June pp. Mardlijah, S. & M.P. Patria Biologi reproduksi ikan madidihang (Thunnus albacares Bonnatere 1788) di Teluk Tomini. BAWAL Widya Riset Perikanan Tangkap. 4(1): Sabates A, Recasens L Seasonal distribution and spawning of small tunas (Auxis rochei and Sarda sarda) in the northwestern Mediterranean. Scientia Marina 65(2): Tampubolon PARP, Novianto D, Hartaty H, Kurniawan R, Setyadji B, Nugraha B Size distribution and reproductive aspects of Auxis spp. From west coast Sumatera, eastern Indian Ocean. IOTC-2016-WPNT06-19.pdf. 7

8 Appendix 1. The criteria of gonadal maturity stage Maturity Condition Remarks Stage I Immature Small perinuclear oocytes with purple stained cytoplasm and a spherical nucleus. Peripheral nucleoli (small black dots) may be seen in the nucleus, along with differential staining of the cytoplasm, which might be precursors of yolk vesicles II Early mature An accumulation of pale purple stained yolk vesicles begins in the cytoplasm. These yolk vesicles initially concentrate at the periphery of the oocyte and spread inwards towards the nucleus. Peripheral nuclei are present III Late maturing Pink stained yolk granules (spheres) are present throughout the oocyte. The zona radiata is wide, turns pink and shows radial striations. The nucleus is centrally located. IV Ripe The nucleus migrates to the periphery of the oocyte and is usually replaced by a few large oil droplets. Sometimes you can see the yolk granules fusing to form yolk plates V Spent The yolk coalesces completely (uniform pink stain). The oocyte significantly increases in size and appears irregular in shape (probably due to a loss of fluid during histological preparation). 8