GROWTH AND SURVIVAL OF SEAHORSE (Hyppocampus barbourie) LARVAE REARED UNDER DIFFERENT TEMPERATURE LEVELS ABSTRACT

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1 GROWTH AND SURVIVAL OF SEAHORSE (Hyppocampus barbourie) LARVAE REARED UNDER DIFFERENT TEMPERATURE LEVELS Irfan Ambas 1 1) Faculty of Marine Science and Fisheries, Hasanuddin University, Makassar Received: 13 May 2008; Accepted: 10 January 2009 ABSTRACT Temperature is one of the water quality parameters which significantly affect growth and survival of aquatic species particularly at early stages. The study is intended to evaluated growth and survival of seahorse (H. barbourie) reared under different temperature levels. Experimental containers were 12 L capacity buckets filled with 5 L sterile treated seawater, equipped with aeration system, a shelter and thermostat. Two days old healthy seahorse larvae were stock at density 1 ind/l. The larvae were fed with enriched Artemia nauplii at density of 1 2 ind/ml once per day after water exchange. Temperature levels examined in the study as treatment were 26 o C (A), 29 o C (B) and 32 o C (C) and each treatment was triplicate. To determine effect of temperature on growth and survival rate of seahorse larvae, the data were analyzed statistically. Growth of larvae reared at different temperature varied greatly both in absolute growth in weight (g) and absolute growth in length (cm). Statistical analysis results indicated absolute growth in weight (g) and length (cm) of larvae reared at 26ºC significantly higher than those larvae reared in temperature 29ºC and 32ºC. Meanwhile, survival rate (%) of seahorse larvae reared at different temperature levels vary considerably but statistically not significant different. Results of the study suggested that rearing of seahorse (H. barbourie) larvae at temperature level of 26 o C will give better results in terms of absolute growth in weight and length, as well as survival rate (%) of the larvae compared to other two temperature (29 o C and 32 o C) examined in this study. Key word: Seahorse larvae, temperature, growth and survival. INTRODUCTION Seahorse is a unique creature which found mostly in marine environment, though several species inhabit estuarine waters. Today the seahorse is facing extinction from over fishing for the pet and medicine trade, and habitat destruction from global warming and development. The wild seahorse is so rare today that it is rarely seen by anyone. The seahorse is now an endangered species protected by CITES (Convention on International Trade in Endangered Species). Seahorse aquaculture has received widespread attention due to concerns over declines in wild seahorse populations, and in recognition of their high economic value and marketability. Seahorse species investigated to date including west Australia seahorse Hippocampus subelongatus (Payne and Rippingale, 2000) the Oceanic seahorse Hippocampus kuda (Job et al., 2002; Anindiastuti dkk., 2005); Hippocampus abdominalis (Woods 2003a, 2003b and 2003c) longsnout seahorse Hippocampus reidi (Olivotto et al 2008). Seahorse aquaculture has great potential to integrate both conservation and sustainable development goals by providing an alternative livelihood option for fishers in source countries who, in the absence of alternatives to fishing, continue to exploit declining seahorse populations. Overexploitation of the seahorse is highly related to its behavior and ecology, such 1 ) Korespondensi: Jurusan Perikanan FIKP UNHAS Jl. Perintis Kemerdekaan Km.10 Tamalanrea Tel/fax: + 62 (0411) irfanambas@yahoo.com) Growth and Survival of Seahorse (Hyppocampus barbourie) Larvae Reared Under Different Temp 19

2 as habitat, lengthy pregnancy, mobility, fecundity etc. Most seahorse inhabit shallow area from 20 feet to 100 feet which is the area most frequented by man. Meanwhile, pregnancy period is also length around days which means if the male broodstock are captured during pregnancy the larvae will also loss. Seahorse mobility is also a major disadvantage of the species from being exploited. Seahorses are slow-moving animal and prefer hold onto objects. Fecundity also contributes to stock population in the wild. Unlike most of fish species which can release thousand even millions of eggs per spawning, seahorse species could only brood eggs less or around 100 eggs. Aquaculture can make a significant reduction the pressure on ocean resources and preventing collapse. However aquaculture industry can only be developed when its larval production technology is already well-practiced in hatchery. One aspect of water quality in larvae rearing particularly for commercial purpose is temperature. Temperature affect metabolism rate of organism, dissolve oxygen which in some point may cause mortality particularly at larvae stages. Al-Qadri, 1993, and Al-Qadri et al, (1997; 1999) reared seahorse (Hyppocampus sp) larvae at temperature around o C. Meanwhile, Simon and Schuster (1997) stated that seahorse live in water temperature of 25 C. Moreover, Wong (1990) in Al-Qadri (1998) found that seahorse live at water temperature between C. RESEARCH METHODS This study was carried out at Hatchery Unit, Department of Fishery, Faculty of Marine Science and Fishery Hasanuddin University, Makassar. Meanwhile, several measurements especially water quality parameters were analyzed at Water Quality Laboratory, department of Fishery. Experimental Organism Seahorse larvae using in this experiment were 2 days old larvae, collected from natural spawning of a broodstock kept in 250 L fiber tank. During maturation, the broodstock were fed 5 % per day of the total body weight with tiny shrimp locally called jembret (Mesopodopsis sp) collected daily from nearby shrimp ponds and fed alive to the broodstock.. Naturally mature and larvae carrying broodstock were selected and held for natural spawning. Last stage male maturation indicated with a very big and dark color of brooding pouch. Spawning of broodstock mostly took place during day time which last up to several hours. Few hours after spawning, the larvae and broodstock were separated before using for experiment. Stocking Density and Feed The 2 days old seahorse larvae were stocked at density of 1 ind/l (Anonim, 1998). Since each bucket filled with 5 L seawaters, therefore each bucket stocked with 5 seahorse larvae. The larvae were fed with enriched Artemia nauplii at density of 1 2 ind/ml fed only once per day in the morning. Experimental Procedure First, each clean 12 L capacity buckets filled with 5 L sterile treated seawater. Newly hatch enriched Artemia nauplii than introduced at density of 1-2 ind/ml. Once all experimental containers were ready, the 2 days old healthy seahorse larvae which previously collected in a big separated container, they were counted individually into experimental container. Each experimental bucket stocked with 5 seahorse larvae (1 ind/l). 20 Irfan Ambas

3 The container also equipped with aeration and shelter where the larvae may hold to. In order to maintain temperature level, each bucket also equipped with a thermostat which its temperature level previously set according to treatment examined here. The thermostat were set at temperature of 26, 29, and 32 o C and placed in the bottom of container according to its temperature level tested. To maintain good water quality, water exchange % was performed each day through siphoning prior to feeding. Experimental Design Experimental design performed in this study was Randomly Experimental Design (RAL) consists of three temperature treatment level and each was triplicate. Each container was placed randomly (Gasperz, 1994). Temperature levels examined in the study were: Treatment A : 26 o C Treatment B : 29 o C Treatment C : 32 o C Parameters Measurements Parameters measured were absolute growth and survival rate and several water quality parameters including salinity, Dissolve Oxygen, ph and ammonia. Growth of larvae was measured at termination of the experiment using electrical balance (0,001 g) and length using scale (0,1 cm). 1) Absolute Growth in Length (cm) Absolute growth in length of the seahorse larvae was calculated using following formula: G = Lt - Lo Where: G = Absolute growth in Length (cm) Lt = Average larvae length at termination of experiment (cm) Lo= Average initial larvae length (cm) 2) Absolute Growth in Weight (g) Absolute growth in weight of the seahorse larvae was also calculated using formula: W = Wt - Wo Where: W = Absolute growth in weight (g) Wt = Average larvae weight at termination of experiment (g) Wo = Average initial larvae weight (g) 3) Survival Rate (%) Data Analysis Survival rate of seahorse larvae in each culture medium was monitored and counted daily, from initial day to the termination of experiment. Survival rate (%) was calculate using formula as follow (Effendie,1997) : S = Nt/No x 100 % Where : S = Survival rate (%) Nt = Number of larvae at initial stocking (ind) No = Number of larvae at termination of the experiment (ind) To determine effect of temperature on growth and survival rate of seahorse larvae, the data were analyzed statistically. For survival rate data, previously transformed using Growth and Survival of Seahorse (Hyppocampus barbourie) Larvae Reared Under Different Temp 21

4 Arsin transformation before analysis. Once analysis showed a significant difference (P < 0.05), analysis was proceed using Least Significant Difference test (LSD) to detect which treatment gave significantly better result. Larvae Growth RESULTS AND DISCUSSION Absolute growth both in weight and length of seahorse (Hippocampus barbaouri) larvae is shown in the Table 1. Table 1. Average absolute growth in weight (g) and length (cm) of seahorse larvae reared at different temperature ( o C) Temperature ( ºC) 26ºC (A) 29ºC (B) 32ºC (C) Absolute growth in weight (g ± sd) Absolute growth in Length (cm ± sd) 0,017 ± 0,003 a 0,593 ± 0,058 a 0,008 ± 0,005 b 0,382 ± 0,135 b 0,001 ± c 0,053 ± 0,092 c Table 1 showed that growth of larvae reared at different temperature varied greatly both in absolute growth in weight (g) and absolute growth in length (cm). Absolute growth of seahorse larvae reared at 32ºC temperature was only 0,001 ± g at termination of experiment, while those reared at temperature 26ºC showed highest average individual weight up to 0,017 ± 0,003 g. Similar in weight, larvae growth in length was also varied. Lowest length (0,053 ± 0,092 cm) achieved in larvae reared at higher temperature (32ºC), on the other hand the length of larvae reared in lower temperature (26ºC ) attained the average length up to 0,593 ± 0,058 cm. Statistical analysis results indicated that temperature significantly affected absolute growth both in weight and length of seahorse larvae. Further, Least significantly difference (BNT) test showed that absolute growth in weight (g) and length (cm) of larvae reared at 26ºC significantly higher than those larvae reared at temperature of 29ºC and 32ºC. In addition, larvae absolute weight (g) and length (cm) reared in water temperature of 29ºC also significantly higher (P< 0.05) than larvae kept in water temperature of 32ºC. The study indicated that better growth both in weight and length of seahorse (H. barbourie) larvae was achieved using lower (26 o C) temperature, compare to other two temperature levels tested here. It seems that seahorse larvae especially for H. barbourie may grow optimally at temperature of 26 o C. Optimum temperature which tolerable to larvae will optimize the use of energy for growth, however when temperature are significantly higher or lower than the optimum levels for the larvae, the energy gained from food will partly used for environmental adaptation or other physiological process. Wong and Benzie (2003) evaluated four temperature levels of 17, 20, 23 and 26 o C on the juvenile seahorses, Hippocampus whitei growth and found that after 107 days rearing there was a significant effect of temperature on the length, wet weight, respiration rate and three condition indices. The juveniles reared at 26 o C were more heavier 48 %, 28 % longer and almost twice higher growth rates compare to those reared at temperature of 17 o C. Although growth of juveniles seahorse were increase with the increase of temperature, however the condition factors decreased as the temperature increased. The decrease of condition factors may be due to a greater metabolic rate, and less fat created at 22 Irfan Ambas

5 higher temperatures. The tolerant adaptability of aquatic species including seahorse is vary slightly according to their stage of the development. Adult individual of seahorse may survive at temperature 32 o C or even higher and to the lower temperature of 20 o C. However, previous preliminary study conducted using temperature above 32 o C showed a mass mortality occurred within one day. Other factor affected related to temperature is dissolve oxygen. Boyd (1982) stated that dissolve oxygen in the water will decrease as the temperature increase. Chemical and biological reactions will twice higher as the temperature increase up to 10 o C. This explained that aquatic organism critically will use or require more dissolve oxygen in higher temperature than in lower temperature. Wong and Benzie (2003) also found the increase of oxygen consumption of seahorse Hippocampus whitei as the increase of temperature from 17 to 26 o C. In spite of stages during development, different species may also have different optimum temperature level for their growth and survival. James and Woods (2001) examined the effect of temperature on seahorse using H.abdominal found that growth increase from 12 to 18 o C, but length did not increase, implies that 18 o C is an optimum temperature for the species. Al-Qadri et al., (1997; 1999) using seahorse species of H. kuda concluded that optimum temperature for rearing of the species larvae was o C. Meanwhile, Payne and Rippingale (2000), rearing West Australian seahorse H. subelpngatus, at temperature of 23 o C. Survival Rate Survival rate of seahorse larvae kept in medium at different temperature levels is shown in Table 2. Table 2. Average Survival Rate (%) of Seahorse (H. barbaouri) larvae Reared Under different temperature Levels. Temperature ( o C) 26º C 29º C 32º C Survival Rate (%) ± Sd 53,33 ± 30,55 a 46,67 ± 23,09 a 6,67 ± 11,55 a Survival rate (%) of seahorse larvae reared at three different temperature levels vary considerably. Lowest survival rate (%) was observed in tanks with temperature of 32º C, while larvae reared with water temperature of 26º C showed highest survival rate (53,33 ± 30,5 %). Statistical analysis indicated that there was no significantly difference (P > 0.05) in terms of survival rate among seahorse larvae reared under different temperature levels. Such result due to great variation among replicates within a treatment. Considerable variation found in this study indicated with a wide range of standard deviation value among replicates (Table 2). Mortality occurs in all treatment during 11 days rearing period (Figure 1). Highest mortality rate was observed in larvae kept at temperature of 32º C, which last after 5 days of rearing and steady to the termination of the experiment. On the other hand, mortality of seahorse larvae reared both at temperature of 26º C and 32º C slightly constant from day 2 to the end of observation period. Al-Qadri et al., (1993) also observe high mortality rate during rearing period of Growth and Survival of Seahorse (Hyppocampus barbourie) Larvae Reared Under Different Temp 23

6 seahorse larvae where mortality on the first two days was 25 %, day 3 to 5 mortality reached 50 % and day 6-10 mortality of seahorse larvae already amount to 75 %. Moreover, when rearing period extended from day 31 to 60, the mortality already reached 95 %. The study suggested it is not surprising that seahorse larvae mortality will occur during rearing period. Adaptability of seahorse species to temperature may vary greatly among species. For example, H. whitei, which subjected to level temperature greater (23 and 26 o C) than its normal temperature in the wild (21 o C), its survival rate were almost 100 % Wong and Benzie (2003). However, higher mortality of seahorse occur in this study particularly those reared at temperature of 32 o C. One possible reason for the relatively higher mortality was feed quality which may not nutritionally meet the seahorse requirements. Payne and Rippingale (2000), stated that artemia nauplii are not an appropriate monodiet for juveniles of some seahorse species. They concluded that the presence of intact artemia in faeces indicated poor digestion, but on the contrary copepods are well digested. In addition, constant feeding with artemia nauplii quantitatively will not meet seahorse requirement. Temperature affects greater on survival than on growth. When temperature level is still within adaptable level for the species, the seahorse may survive but considerable effect on growth will arise. However, when the organisms are subjected to such a high temperature for a long period, it will lead to mortality. 120 Survival (%) of Seahorse Larvae Reared under Different Temperature Level Survival Rate (%) Rearing Period (day) Figure 1. Survival Rate (%) of seahorse larvae during 11 days rearing period under different temperature level 26 o C ( ) 29 o C( ), and 32 o C (X) Water Quality Water quality is one of the key important factor for succeed of aquatic species culture activities. Boyd (1982) stated that water quality is a variable or parameter which affecting survival rate, growth, reproduction and fish production. Average value of several water quality parameters measured in this study is presented in Table Irfan Ambas

7 Table 3. Average Value of Several Water Quality Parameters during experiment Parameters Temperature Examined A (26ºC) B (29ºC) C (32ºC) Optimum References Salinity (ppt) Al Qadri (1997) ph Al Qadri et al(1999) DO (mg/l) Al Qadri (1999) Ammonia (ppm) < 0,5 Al Qadri (1998) It seems that water quality in culture medium during rearing period of seahorse larvae at different temperature level was still within the range of optimum level for better growth and survival of the larvae, except dissolve oxygen level which sometime dropped to level of 4.16 ppm. It is already mention previously that water temperature also affect dissolve oxygen in the rearing tanks. CONCLUSION Temperature affects growth both in weight (g) and length (cm) of seahorse (H. barbourie) larvae. Highest absolute growth was found in larvae reared at 26 o C and the lowest was observed in larvae cultured at water temperature of 32 o C. Survival rate of seahorse larvae range between 6,67 ± 11,5 % to 53,33 ± 30,55 % at the termination of 11 days culture period. In general, water quality parameters during experiment were still within the optimum range for good growth and survival of seahorse larvae, except for the temperature examined in this study. REFERENCES Al Qodri, A.H., Sudaryanto dan P. Hartono Pemeliharaan Juwana Kuda Laut (Hippocampus spp) pada Bak Terkontrol. Direktorat Jenderal Perikanan. Balai Budidaya Laut. Lampung. Al Qodri, A.H Breeding Standard of Sea Horse in Indonesia. Paper Presented to International Workshop on The Management an Culture of Marine Species Used in Tradisional Medicine, 5-9 Juli Cebu Philippines. Sea farming Development Center. Teluk Betung. Indonesia. Al Qodri, A.H., Sudaryanto dan Hartono P., Rekayasa Teknologi Pembenihan Kuda Laut (Hippocampus spp). Direktorat Jenderal Perikanan. Balai Budidaya Laut. Lampung. Al Qodri, A.H., Ari W.K dan P. Hartono Rekayasa Pemijahan Kuda Laut (Hippocampus kuda Blecker). Makalah disampaikan pada Pertemuan Perekayasaan Teknologi Pembenihan Agribisnis Air Tawar, Payau dan Laut Lintas UPT Ditjen Perikanan, tanggal Juli 1999, Hotel Param Cisarua, Bogor. Anindiastuti, Thariq M and Al Qodri A.H., Hatchery technology of Seahorse Hippocampus kuda in Indonesia. Book of abstract. World aquaculture Bali Indonesia International Peace and Development Through Aquaculture. May , Bali International Convention Center, Nusa Dua, Bali Indonesia. Page 38. Boyd, C.F Water Quality Management for Pond Fish Culture. Auburn University. Alabama. USA. Effendie, M.I Biologi Perikanan. Yayasan Pustaka Nusatama. Yogyakarta Gaspersz, V Metode Perancangan Percobaan. Armico. Bandung. Growth and Survival of Seahorse (Hyppocampus barbourie) Larvae Reared Under Different Temp 25

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