Some aspects in early life stage and female spawner of swamp eel, Monopterus albus Journal: Songklanakarin Journal of Science and Technology Manuscript ID SJST-0-0.R Manuscript Type: Original Article Date Submitted by the Author: -Jul-0 Complete List of Authors: Amornsakun, Thumronk; price of Songkla University, Keyword: Fecundity, Yolk absorption, Mouth development, Start of feeding, Swamp eel, Monopterus albus
Page of 0 0 0 0 0 0 Female biology and early life aspect of swamp eel, Monopterus albus Thumronk Amornsakun *, Ponpanom Promkaew and Anuar bin Hassan Fisheries Technology Program, Department of Technology and Industries Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, Pattani, Thailand 000. * Corresponding author. E mail address: thumronk.a@psu.ac.th thumronk.a@gmail.com Pattani Inland Fisheries Development Center Yarang, Pattani Faculty of Fisheries and Aqua-Industry Universiti Malaysia Terengganu Mengabang Telipot, Kuala Terengganu, Malaysia 00 Abstract The sexual maturity of female swamp eel, Monopterus albus was studied by determining its fecundity and gonadosomatic index (GSI). It was found that the size of a sexually matured female swamp eel was 00-0 g in body weight. The egg s type were non adhesive demersal and rounded. The maximum fecundity was found in June at 0 ova/fish with gonadosomatic index (GSI) of.0 %. The minimum fecundity was recorded ova/fish as in October with gonadosomatic index (GSI) of 0. %. The average diameter of egg was, µm. Overall, the sizes of the fish eggs can be classified into seven groups (based on its diameter), which were 0-0 µm (. %) as group, -,0 µm (. %) as group,,-,0 µm (. %) as group,,-,0 µm (.0 %) as group,,-,0 µm (. %) as group,,-,0 µm ( %) as group, and,-,0 µm ( %) as group. Newly hatched larvae of swamp eel were produced by semi-control natural method. The newly hatched larvae were sized in. ± 0.0 cm in total length (TL), with yolk sacs volume of,.±0.0 µm. The yolk sacs were completely absorbed within hours after hatching (hah) time at water temperature of -0. C. All the larvae were able to open mouths at 0 hah (.0 ± 0. mm TL), with the height measurement of.00 ± 0. µm. The digestive tract was straight, and it is placed on the yolk sac. The digestive tracts were formed at hah with length of.00 ± 0. µm. The average number of Moina in the digestive tract at the start of feeding was 0. individual/larva. Larvae died within,0 hah at water temperature ranged between.0 to 0. C. It was found that the feeding scheme of larval swamp eel were as follows: larvae of age - days (total length.-.0 cm) consumed Moina., but at of age - days (average total length.-.0 cm) the larvae consumed both Moina and a commercial pellet known as power feed. Larvae that at more than -day old (average total length.0 mm) consumed only power feed. KEYWORDS: Fecundity; Gonadosomatic index (GSI); Yolk absorption; Mouth development; Start of feeding; Starvation, Larviculture; Swamp eel, Monopterus albus
Page of 0 0 0 0 0 0. Introduction Swamp eel, Monopterus albus is a commercially important fish in Southeast Asia aquaculture industry. To propagate M. albus in commercial-scale hatcheries, it is essential to provide fundamental biology information about the early-life yolk absorption, mouth opening, digestive tract development, and the start of feeding time. Complete yolk absorption is recognized as critical period in larval rearing and survival (Kosutaruk & Watanabe, ; Holm, ; Eda, Fujiwara, & Takita, ; Amornsakun & Hassan, ; Amornsakun, Chiayvareesajja, Hassan, Ambak, & Jee, ; Amornsakun, a; Amornsakun, Sriwatana, & Chamnanwech, 00; Amornsakun, Sriwatana, & Promkaew, 00a; Amornsakun, Sriwatana, & Promkaew, 00b). Survival of fish larvae is determined by the interaction of various environmental factors, such as temperature, food supply with a suite of species-specific characteristics, egg and larval size, yolk and oil globule volume, and its resorption rates, time of onset of feeding and feeding behaviour. Larvae use yolk energy for various activities (Blaxter, ; May, ). Mouth size at first feeding stage of various larval fish encounter their appropriate prey size has been well documented for a number of cultured fish (Shirota, 0; Nash, Kuo, & McConnel, ; Fukuhara, ; Doi&Singhagraiwan, ; Eda, Fujiwara, & Takita, ). M. albus is eel-like shape, with yellow ventral and black dorsal body without pectoral fins (Collin, Trexler, Nico, & Rawlings, 00; Jewham, 00; Jesoa & Kuanmuang, ). M. albus is carnivorous fish that eat shrimp, fish, insect, worm and detritus (Hill & Watson, 00), for example fish (%), shrimp (%) and insect (%) (Shafland, Gestring, & Sanford, 00). Maturity age of the fish is over year old, but can be different between male and female fish (Liem, ). Sexual dimorphism of this fish can only be classified by gonad observation. Sexually-matured female M. albus are known to be about -0 cm long
Page of 0 0 0 0 0 0 and 00-0 g body weight while the male being 0-. cm long, and 00-00 g body weight (Kuanmuang, ). Spawners were daily fed with fresh fish, about % of the body weight. Fish spawner will make the fish nest before spawning. Cultured M. albus larvae were fed by commercial pellet known as power feed (containing 0% protein) (Pechcharoon & Uraipradit, 00). However, fundamental information about biological development of early life and female maturation still remain to be discovered therefore this study was designed to investigate baseline information for optimization of large scale culture, and ultimately for the culture management of this fish, including fecundity, gonadosomatic index (GSI) of mature female fish, period of yolk absorption, larvae mouth development, and onset of larvae first feeding period.. Materials and methods The sexual maturity of M. albus was studied by determining its fecundity, egg diameter, and GSI. Fecundity was estimated by a gravimetric method (Tarnchalanukit, Chuapoehuk, Suraniranat, & Na Nakorn, ). Egg diameter was measured using an ocular microscope (Amornsakun, Sriwatana, & Promkaew, 0). GSI was calculated, using the following equation (Tarnchalanukit, Chuapoehuk, Suraniranat, & Na Nakorn, ): GSI= Weight of ovary Weight of body 00 Semi-control natural method was used to produce newly-hatched larvae which were done sexually mature fishes, male and female brooders at a : ratio, were cultured in concrete ponds in which soil was filled as spawning ground and the water depth were kept at 0 cm. The spawners were fed every two days with fresh fish (% of their BW). Fertilized eggs were routinely checked in concrete ponds for daily spawning examination, and transfer fertilized egg to fiberglass tank for hatching.
Page of 0 0 0 0 0 0. Yolk absorption The time of yolk absorption and the size of yolk-sacs were assessed using a profile projector. Ten newly-hatched larvae were randomly sampled every hours from aquarium until the yolk sacs were fully absorbed. The specimens were fixed in 0% buffered formalin. Yolk volumes were calculated using the following formula (Fukuhara, ): = ( ) where R = minor axis and R = major axis.. Mouth height Samples of twenty newly hatched larvae were taken every hours from the aquarium to measure the size of mouth opening and upper jaw length using a profile projector, after fixing in 0% buffered formalin. The mouth height was calculated as follows (Shirota, 0): mouth height=upper jaw length. Start of feeding Larvae (n=00, aged. days) were fed with Moina (0 µm width) at a density of 0 individual/ml in a -liter aquaria (0 L of water). Twenty larvae were randomly sampled every hours, fixed in 0% buffered formalin and dissected to observe the presence of Moina in the digestive tract which signaled the time of feeding start (Pechmanee, Pongmaneerat, & Iizawa, ). This observation conducted in replication.. Starvation Newly-hatched larvae (00) were starved in a -liter aquaria (0 L of water) to monitor mortalities at every hours till completion in replication (Fukuhara, ).
Page of 0 0 0 0 0 0. Feed and feeding Larvae (00, aged days) were cultured in a -liter aquaria (0 L of water) and were fed in a scheme, as follows: those aged - days with Moina at a density of 0 individual/ml and those aged - days with Moina and commercial pellet (0% crude protein) (in density :) twice a day (Tarnchalanukit, Chuapoehuk, Suraniranat, & Na Nakorn, ; Kungvankij, Pudadera, Tiro, & Potestas, ; Eda, Darwisito, Fujiwara, & Takita, ). Twenty larvae were randomly and daily collected hour after feeding, fixed in 0% buffered formalin and observed their stomach contents.. Results Female of M. albus (Figure ) were found matured at sized 00-0 g BW, maximum fecundity of 0 ova/fish with GSI.0% (Figure ) in June and minimum fecundity of ova/fish) with GSI of 0.% in October were obtained. The eggs were non-adhesive demersal and rounded with sizes at, µm. The egg were able to classified into groups such as 0-0 µm (.%), -,0 µm (.%),,-,0 µm (.%),,-,0 µm (.0%),,-,0 µm (.%),,-,0 µm (%), and,-,0 µm (%) (Figure ). Newly-hatched larvae (mean±sd, n=0) were.±0.0 cm in length with yolk sacs volume of,.±0.0 µm (Figure ). The yolk sacs were completely absorbed within hah (.±0. cm) at -0. C (Figure ). Mouths were opened about 0 hah (.0±0. cm) with mouth sized at.00±0. µm in width (Figure ), with a straight digestive tract at was.00±0. µm in total length and anus opening at hah (.±0.0 cm) at.0-. C. The average number of Moina in the digestive tract at the start of feeding was 0. individual/larval. The larvae started to feed with Moina at hours
Page of 0 0 0 0 0 0 after mouth opening, and at hours before yolk absorption. The starved larvae started to die at 0 till,0 hours (. days) (Figure ),.0-0. C. Based on the feeding scheme number of Moina being consumed by -, -, -, -, -, 0-, -, -, -, - and -days-old larvae (.-.0 cm in length) were.,.,., 0.,.,.,.,.,.,. and. individuals/larva, respectively, at -0. C. The larvae at age - days (average total length.-.0 cm) consumed both Moina and commercial pellet. Larvae age more than after -day old (average total length.0 mm) consumed exclusively on power feed.. Discussion The fecundity of M. albus, 0 ova/fish, was comparatively less than those of Channa striatus, Anabas testudineus and Trichogaster pectoralis. But the sexually-matured female M. albus was 00-0 g. Sexually-matured female C. striatus was reported. cm in total length,. g BW, and 0, ova/fish fecundity (Amornsakun, Sriwatana, & Promkaew, 0); whereas A. testudineus being. cm in length and g BW and,0 ova/fish fecundity (Amornsakun, Sriwatana, & Promkaew, 00a) and T. pectoralis being.0 cm in length,.0 g BW,, ova/fish fecundity (Amornsakun, Sriwatana, & Promkaew, 00b). The fertilized eggs of M. albus (, µm in diameter) were classified as large, similar to Mystus wyckioides (,.0 µm), but - times larger than those of C. striatus, A. testudineus and T. pectoralis, respectively (Amornsakun, b; Amornsakun, Sriwatana, & Promkaew, 00a; Amornsakun, Sriwatana, & Promkaew, 00b; Amornsakun, Sriwatana, & Promkaew, 0). The lower GSI of the mature female M. albus of.0% than the normal range -0% of Clarias batrachus (Tarnchalanukit, Chuapoehuk, Suraniranat, & Na Nakorn, ) but similar to C. striatus.0% (Amornsakun, Sriwatana, & Promkaew, 0), and. and. times less than those of A. testudineus and T. pectoralis, respectively (Amornsakun, Sriwatana, & Promkaew, 00a; Amornsakun, Sriwatana, & Promkaew, 00b).
Page 0 of 0 0 0 0 0 0 The yolk absorption period for newly-hatched larval M. albus was. days after hatching, which were longer than M. nemurus ( days) (Amornsakun, Chiayvareesajja, Hassan, Ambak, & Jee, ), M. wyckioides (. days) (Amornsakun, b) Oxyeleotris marmoratus (. days) (Amornsakun, Sriwatana, & Chamnanwech, 00) A. testudineus (. days) (Amornsakun, Sriwatana, & Promkaew, 00a), T. pectoralis (. days) (Amornsakun, Sriwatana, & Promkaew, 00b), C. striatus (. days) (Amornsakun, Sriwatana, & Promkaew, 0), Mugil curema (. days) (Houde, Berkeley, Klinovsky, & Schekter, ), Chanos chanos (. days) (Chaudhuri, Juario, Primavera, Samson, & Mateo, ) and Clarias sp. (- days) (Tarnchalanukit, Chuapoehuk, Suraniranat, & Na Nakorn, ). The yolk sac volume at the time of the first feeding of M. albus was. %, which were higher C. striatus (.%) (Amornsakun, Sriwatana, & Promkaew, 0), O. marmoratus (.%) (Amornsakun, Sriwatana, & Chamnanwech, 00), similar with M. wyckioides (.0%) (Amornsakun, c), but less than M. nemurus (.0%) (Amornsakun, Chiayvareesajja, Hassan, Ambak, & Jee, ), T. pectoralis (.%) (Amornsakun, Sriwatana, & Promkaew, 00b) and A. testudineus (.0%) (Amornsakun, Sriwatana, & Promkaew, 00a; Kjorsvik, Meerent, Kryvi, Arnfinnson, & Kvenseth, ). The size of Moina was.% of mouth opening of the larval M. albus (.00 µm), in the range 0-0% of mouth size in various fishes (Hunter, 0; Amornsakun, Chiayvareesajja, Hassan, Ambak, & Jee, ; Amornsakun, c; Amornsakun, Sriwatana, & Chamnanwech, 00; Amornsakun, Sriwatana, & Promkaew, 00a; Amornsakun, Sriwatana, & Promkaew, 00b) but different from C. striatus (.%) (Amornsakun, Chiayvareesajja, Hassan, Ambak, & Jee, ; Amornsakun, c; Amornsakun, Sriwatana, & Promkaew, 0) M. wyckioides (.%), M. nemurus (0.%), O. marmoratus (.0%), T. pectoralis (.%) A. testudineus (0.%)
Page of 0 0 0 0 0 0 (Amornsakun, Sriwatana, & Chamnanwech, 00; Amornsakun, Sriwatana, & Promkaew, 00a; Amornsakun, Sriwatana, & Promkaew, 00b). Moina could be a good live food for larval M. albus because of its suitable size and ease of culture. The number of Moina in the digestive tract at the start of feeding was 0. individual /larva, similar to those reported in T. pectoralis, O. marmoratus and C. striatus, but less than reported in A. testudineus, M. nemurus, M. wyckioides and C. chanos. Gut contents showed 0. rotifer/larva of T. pectoralis (Amornsakun, Sriwatana, & Promkaew, 00b), 0. rotifer/larva of O. marmoratus (Amornsakun, Sriwatana, & Chamnanwech, 00), 0. Moina/ larva of C. striatus (Amornsakun, Sriwatana, & Promkaew, 0),. rotifer/larva of climbing perch (Amornsakun, Sriwatana, & Promkaew, 00a),. individual/larva of green catfish (Amornsakun, Chiayvareesajja, Hassan, Ambak, & Jee, ). Moina/larva of M. wyckioides (Amornsakun, c) and - rotifer /larva of C. chanos (Eda et al., 0). The starved larva of M. albus become debilitated and eventually died at 0 hah, less tolerance lower than A. testudineus ( hours) at.0-0.ºc (Amornsakun, Sriwatana, & Promkaew, 00a), and C. striatus ( hours) at.0-0.ºc (Amornsakun, Sriwatana, & Promkaew, 0). Larvae can tolerate feeding delay up to a certain point depending on the amount of yolk, temperature and other species-specific characteristics (May, ; Hunter, 0; Holm,), for example, days for Engraulis mordax (Lasker, Feder, Theilacker, & May, 0), days for Mugil cephalus (Kuo, Shehadeh, & Milisen, ), days for C. chanos (Chaudhuri, Juario, Primavera, Samson, & Mateo, ), days for Repomucenus sp. (Eda, Darwisito, Fujiwara, & Takita, ), days for Lates calcarifer (Hassan & Amornsakun, ), days for T. pectoralis (Amornsakun et al., 00b). Ishibashi () observed that the yolk sac of unfed Tilapia sparmanii larvae was absorbed faster than that of fed larvae.
Page of 0 0 0 0 0 0 Food supply during the larval stage is an important factor in achieving high survival and growth rates. Mass mortality of larval and juvenile fish will often occur if the food supply is inadequate (Houde, ). Different species require different sequential food during the early life stages. Most freshwater fish are given rotifer or Moina as a first feeding (Tarnchalanukit, Chuapoehuk, Suraniranat, & Na Nakorn, ; Tawaratmanikul, Viputanimat, Mewan, & Pokasap, ; Vatcharakornyothin, Viputhanumas, Tawaratmanikul, & Pokasap, ), and artificial feeds for juveniles are generally in the form of fine crumbles of appropriate particle size. The larval M. albus is no exception. The type of feed for larval M. albus cultured such as Moina and commercial pellet is similar with other fishes, but time for feeding may be different. It was found that larval M. albus of age - days (average total length.-.0 cm) consumed Moina. The larvae of age - days (average total length.-.0 cm) consumed both Moina and power feed. Larvae aged more than days able to consume completely with power feed. Watanabe, Kitajima, and Fujita () described the food regimes used most extensively in the larvae of various fish production in Japan. In newly hatched fish greater than. mm of body length, rotifers were exclusively given as an initial feed, when fish reached mm or more, marine copepods such as Tigriopus, Acartia, Oithona and Paracalanus were given. Brine shrimp, Artemia salina, were commonly used for the larvae of many species during shortages of marine copepods. Larvae larger than 0 to mm were fed minced fish, shellfish and shrimp or an artificial diet. Tsukashima and Kitajima () reported the rearing of larval and juvenile filefish, Stephanolepis cirrhifer, up to the stage of young fish. They were fed rotifer, Tigriopus japonicus, Artemia and subsequently fish meat. Tarnchalanukit, Chuapoehuk, Suraniranat, and Na Nakorn () reported that C. batrachus of age - days were fed on Moina, and fed with a commercial catfish pellet when they reached 0 days-old. Chawpaknam, Vorasayan, and Poungin (0) reported that fry nursing of two-spot glass
Page of 0 0 0 0 0 0 catfish, Ompok bimaculatus, of age - days fed with Moina showed a better growth and higher survival rates than those fed with egg custard. The M. albus larvae of age - days (average total length.-.0 cm) consumed zooplankton such as Moina. At days old of larvae consumed only power feed, and this stage is sheer regarded as juvenile stage. The time for juvenile-stage development was similar with the M. nemurus and A. testudineus, but it was earlier than O. marmoratus and T. pectoralis. As reported previously, larval stage for M. nemurus, and A. testudineus were reported at age between -0 and - day-old fed on rotifer and Moina as main diet. At age of day-old onward, both species were developed as juvenile stage and able to fed on commercial artificial (Amornsakun, Chiayvareesajja, Hassan, Ambak, & Jee, ; Amornsakun, Hassan, Ambak, & Chiayvareesajja, ; Amornsakun, Sriwatana, & Promkaew, 00a). While, O. marmoratus have longer larval period at about - days which was only fed on rotifer and Artemia, before reach juvenile stage at 0- day-old fed with either Moina or grinded fish (Amornsakun, Sriwatana, & Chamnanwech, 00a; Amornsakun, Sriwatana, & Chamnanwech, 00b). Despites, T. pectoralis larval stage was reported at the age of - day-old. The first diet T. pectoralis was rotifer at early stage fllowed by Moina. Nevertheless, at age of -0 day-old was able to feed with articicial diet (Amornsakun, Sriwatana, & Promkaew, 00b). We concluded that the size at sexual maturity of female M. albus was 00-0 g in body weight. The eggs were non adhesive demersal and rounded type. Fecundity was maximum (0 ova/fish) in June with GSI of.0 %. The average diameter of egg was, µm. The newly hatched larvae were.±0.0 cm in total length, and had yolk sacs of,.±0.0 µm in volume. The yolk sacs were completely absorbed within hours after hatching at a water temperature of -0. C. All the larvae had open mouths about 0 hours after hatching (.0±0. mm), with mouth size at.00±0. µm opened at
Page of 0 0 0 0 0 0 hah. The average number of Moina in the digestive tract at the start of feeding was 0. individual/larva. The feed deficit larvae started to die at 0 hours. The feeding scheme of larval M. albus were as follows: larvae of age - days (average total length.-.0 cm) consumed Moina., but at of age - days (average total length.-.0 cm) larvae were able to fed with Moina and commercial pellet know as power feed. Acknowlegements I am grateful to the Prince of Songkla University (ก00) for financial support of the field work. I also thank Mr.Humdee Doloa and MissVeeranut Kuntiyapiruk for assistance in research. And I would also like to thank Assoc. Prof. Dr. Buhri bin Arifin and Assoc. Prof. Dr. Aroonsri Priprem for editorial assistance in preparing this manuscript. References Amornsakun, T. (a). Feeding biology in early life stages of green catfish, Mystus nemurus (Cuv.&Val.). Ph.D. Thesis, Faculty of Applied Science and Technology, University Putra Malaysia Terengganu. p. Amornsakun, T. (b). Preliminary propagation and larval rearing of red-tail catfish, Mystus wyckioides. Research report, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus. p. (in Thai with English abstract) Amornsakun, T. (c). Some aspects in early life stages of larval red-tail catfish, Mystus wyckioides. Songklanakarin Journal of Science and Technology, (), 0-0. Amornsakun, T., & Hassan, A. (). Aspect in early life stage of larval red snapper, Lutjanus argentimaculatus (Forskal). Songklanakarin Journal of Science and Technology, (), -.
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Page of 0 0 0 0 0 0 Figure. Matured female of swamp eel
Page of 0 0 0 0 0 0 Figure. The ovary of swamp eel
Page of 0 0 0 0 0 0 Figure. The Eggs of swamp eel
Page of 0 0 0 0 0 0 Figure. Newly hatched larvae of swamp eel
Page of 0 0 0 0 0 0 Yolk Volume (cubic micrometer) 00 00 00 000 00 00 00 00 0 0 0 00 0 00 Time Elasped from Hatching (hr) Figure. Total length (TL) and yolk absorption of larval swamp eel at elapsed time after hatching YV: Yolk volume
Page of 0 0 0 0 0 0 Mouth Height (micron) 000 00 00 00 00 00 00 00 00 00 0 0 0 00 0 00 Time Elasped from Hatching (hr) Figure. Total length (TL) and development of mouth opening of larval swamp eel at elapsed time after hatching MO: Mouth Opening 0
Page of 0 0 0 0 0 0 Survival Rate (%) 0.00 00.00 0.00 0.00 0.00 0.00 0.00 0 00 00 00 00 00 00 00 00 00 000 00 00 Time Elasped from Hatching (hr) Figure. Survival of swamp eel after hatching without feeding at.0 to 0. C