Автор неизвестен - Krmulture in iran - страница 32

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20: 0



20: 1n-9



20: 2n-6



20: 3n-3



20: 4n-6



(20: 5n-3) (EPA)



(22: 6n-3) (DHA)















Data are mean±SD (n=3)

Dissimilar letters in rows indicate a significant difference (P<0.05)

Therefore, in order to achieve resistance against stress-induced changes in environmental conditions of ornamental fishes, use of artemia enriched with long-chain polyunsaturated fatty acids in breeding centers of ornamental fishesis recommended.


The author wishes to thank Shahid Etebari Research Institute of Isfahan University of Technology for their financial support.


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Ako, h; Tamani, C.S; Bass, P. and Lee, C.S., 1994. Enhancing the resistance to physical stress in larvae of Mugical cephalus by the feeding of enriched Artemia nauplii. Aquaculture, 122(1), 81-90.

Smith, D. M., Hunter, B.J., Allan,h, G.L., Roberts, D.C.K., Boot M.A. and Glencross, B.D.,

2004. Essential fatty acids in diet of silver perch, Bidyanus bidyanus :effect of linolenic and linoleic acid on growth and survivalAquaculture, 236(1^4),377-390.

Van Stappen, G., Lavens, P. and Sorgeloos, P., 1996. Artemia:In:Manual on the production and use of live food for aquaculture, Eds., FAO. Publication,. 101-318 pp.

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Effect of brood-stock's diet containing enriched Artemia on survival rate in Angel Pterophyllum scalare


Hamed Mousavi-Sabet

Deptartment of Fisheries, Faculty of Natural Resources, University of Guilan, Someh Sara, Guilan, Iran. Mousavi-sabet@guilan.ac.ir


Artemia was added to diets of angel fish Pterophyllum scalare broodstocks and larvae survival rate was determined. Broodstock angel fish (18 pairs) were kept separately in a 50 L aquarium. Artemia + fatty acid emulsion + 0.5 g vitamin C resulted in the highest larvae survival (93.3%) which was also significantly higher than the control group (P < 0.05). Adding Artemia decreased larval mortality rate and would be a useful ingredient to include in diets for broodstock in continuous spawning operations and is likely to be economical for broodstock operations because of increased efficiency even though the feed cost would be higher.


Ornamental fishes are popular pets around the world and their cultivation can be quite lucrative. Fresh water ornamental fishes are found in different areas in the world and the aquarium industry has developed methods for cultivation and propagation of many common species. Angel fish Pterophyllum scalare is native of Central America and can live and adapt to a variety of climate or environmental conditions. This fish is commonly sexually mature at less than one year of age. Its life spawn depends upon how well proper culture conditions are maintained, but it seems that this fish would survive for 2-3 years under ideal conditions. It can spawn 10-15 times on average, each time producing hundreds of eggs Brood stock fed live food often perform

better because the live food may have greater nutritional value, be more palatable and easier to digest and can positively influence gonadal development and propagation. Successful fish production depends upon access to suitable food for feeding that is healthy and supports growth for brood stock and for the newborn stages for the larvae (Lim 2002a). Among numerous sources and variety in live food, Artemia is particularly important. Artemia can be used as carrier of some nutritive materials such as long chain unsaturated fatty acids and vitamins especially vitamin C (Coutteau et al. 1997). Researchers indicate that fatty acids play a critical role in the reproductive physiology of teleost fishes (Kim et al. 1996) such as maintaining immune function, osmoregulatory systems and endocrine system function. Vitamin C plays an important role in maintaining immune response and is required for numerous biological functions in fish and other vertebrates, for example, maintaining skeletal integrity, growth and survival and physiologic coefficient such as resistance against stresses, poisoning and immune activities improve in different species of aquatic larvae with usage of vitamin C complements (Dhert and Sorgeloos 1995). In this research the affect of feeding angel fish broodstock artemia (Artemia) which had been specifically fed an emulsion of unsaturated fatty acids and vitamin C was tested to determine if feeding these enriched artemia would improve the survival rate of angel fish larvae.

Materials and methods

Broodstocks were the eighteen pairs of fish with 9-10 months of age and 8-11 cm in length. They were divided into 6 treatment groups and each treatment replicated 3 times. Selected pairs were ready to spawn. The ideal spawning conditions involved separating brood stock from the colony (100 fish in two aquariums with 500 liter of water) and placing each breeding pair into a separate aquarium with 50 liter of aerated, dechlorinated municipal water (28.0±0.1oC, pH=7.5±0.5, and hardness >170 ppm). To stimulate spawning, a ceramic plate was placed at an angle of 45° against an inside wall of the aquarium to stimulating

spawning and provide a locus for egg deposition. Selected brood stock fishes were acclimated on the treatment feed for at least during 7 days before the first experimental spawning. Fish diets for the various treatments included a control diet which was a common concentrated food for ornamental fishes (crude protein 40%, crude fiber 5%, crude fat 6%, moisture 12%, ash 10%) (Energy Company, Thailand). Live Artemia was transferred to the ornamental fish farm and enriched in 1.5 L dishes with 33 g/L salt, 28 °C and under mild aeration. The density of the Artemia was 200 animals per liter when fed to the fish. To produce the artemia high in unsaturated fatty acid the following feeding regime was followed: Artemia was suspended in a small tank containing an emulsion

INVE Co (ICES 30/4/C, INVE Co., Belgium) which consist of 30%

unsaturated fatty acid methyl esters at 30% dry weight of the emulsion). This emulsion was 4 to 1 of dicosahexenoic (DHA) and eicosapentaenoic (EPA). Preparation of standard emulsion is done on the basis of Leger's formulation 1989 (Lim 2003). Five ml of the fatty acid emulsion was blended with 50ml dechlorinated fresh water and blended in an electric blender for 3 minutes at room temperature. For Artemia enriching with fatty acids and vitamin C, ascorbyl palmitate was added at a ratio of either 10% or 20% of the fatty acid emulsion as proposed by (Merchie et al. 1995, 1997) and Agh and Sorgeloos (2005). The ascorbyl palmitate at 0.05 g or 1 g per 5 ml of emulsion was blended with 50 ml of water for a total of 55 ml. Five ml of this blend was then added to the 1.5 L tank for enrichment. These prepared emulsions blends were stored in tightly sealed containers which excluded light under a nitrogen head space to limit oxidation and the suspension kept in the refrigerator for up to 10 days until it was used for enriching the Artemia. For each spawning cycle a new batch of enriched artermia was prepared. For artemia enrichment, 2ml of one of the emulsions described above was added to per 1liter of water (Leger et al. 1987; Coutteau and Sorgeloos 1997). After 12 hr, enrichment solution effective saturation of the artemia was achieved. A treatment of 4 ml per liter water was added with the Artemia and incubated for 24 hr. After 24 hr, the enriched Artemia were recovered. At this point, we wrapped the artemia in a clean and wet cloth and held them

in a refrigerator (10°C) until use. The enriched artemia were fed within 24 hours to the broodstock angel fish. Brood stocks were feed 4 meals a day at 7:00, 12:00, 17:00, 23:00 hours. The control group was fed with a commercial concentrated food using the same feeding schedule. 4 to 5 days after hatching, the number of actively swimming larvae was counted. This provided data for computing larvae survival rate. To determine uptake of long chain fatty acids in the enriched Artemia, fatty acid profiles were measured (n=3) by the gas chromatography system (GC). Data were analyzed by analysis of one-way ANOVA, and Duncan's test in P < 0.05 for comparison of averages using SPSS 16 software.


The concentration of EPA and DHA in the artemia increased after enrichment with the emulsion from 3.48-3.82g and 6.89-6.77 g percent of the total fatty acids and vitamin C for EPA and DHA respectively. The level of EPA was 1/25(%) and DHA was 1/59(%) in concentrate food.

The survival rate were 74.9, 87.4, 92.3, 93.2, 93.3 and 93 in different

treatments including concentrated food (control treatment), concentrate food +Artemia, Artemia, Artemia + unsaturated fatty acid, Artemia + unsaturated fatty acid + 0.5g Vitamin C, Artemia + unsaturated fatty acid + 1g Vitamin C, respectively.


The effect of enriching live artemia with long chain unsaturated fatty acid and Vitamin C is has been evaluated in different species of fishes and shrimp in salt and fresh water, but only in a few ornamental fishes. Similar research with Acipenser sp., Indian white shrimp post larvae (Tenaeus indicus), rainbow trout larvae (Oncorhynchus mykiss), giant freshwater prawn (Macrobranchium rosenbergii) and milk fish larvae (Chanos chanos) reported and that enriched artemia with unsaturated fatty acid and Vitamin C increased larvae survival rate (Dhert et al. 2004; Gapasin 1998; Girri et al. 2002; Lim 2001; Lim 2002a). Here we saw an

increase in survival between the control and the treatments using fatty acid enrichment, but adding vitamin C in addition to the unsaturated fatty acids did not appear to increase survival. Moradkhani (2008) studied Cichlasoma severum and noticed effects of using live food include enriched foods on increased fecundity. Also, Tamaru et al. (2003) noted that the use of live food for angel fish brood stock and Carassius auratus increases fertilization percent. Lim et al. (2003), Tamaru et al. (2003), Dhert (2004) and Moradkhani (2008) researched feeding for Poecilia reticulata, Xiphophorus helleri, Xiphophorus maculates, Poecilia sphenops, Hyphessobrycon herbertaxelrodi, Cichlasoma severum, Carassius auratus and Symphysodon aequifasciata and found that enrichment of Artemia with unsaturated fatty acid and ascorbic acid and its use in feeding of brood stocks improved larvae survival rate. Adding Artemia with unsaturated fatty acids and Vitamin C to broodstocks diets improved larval survival rate (Moradkhani 2008; Lim 2001a; Lim 2001b; Merchie 1997; Sorgeloos 1980; Tamaru et al. 2003). About larvae survival rate, acquired results showed that all treatments have significant difference with testimonial group (P < 0.05). Since Vitamin C decreases stress, as result; decreasing effect of environmental stresses on larvae cause to increase its survival in treatment which had been enriched with ascorbic acid. Increasing unsaturated fatty acid and vitamin C content in the parents' food could transmit beneficial effects to the gametes through the fertilized eggs enhancing survivability and increasing the strength of the resulting larvae. Improving efficiency of hatchery operations would make them more economically viable and also increase the number of offspring from breeding pairs of angel fish.

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Res 33(8): 575-589.

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Breeding season of Cobitis keyvani in south of the Caspian Sea basin

Hamed Mousavi-Sabet

Deptartment of Fisheries, Faculty of Natural Resources, University of Guilan, Someh

Sara, Guilan, Iran.

Email: Mousavi-sabet@guilan.ac.ir


Breeding season of Cobitis keyvani, an endemic Loach fish species from the Talar River in south of the Caspian Sea basin, in north of Iran was studied by regular monthly collections throughout one year. Gonado-somatic and modified gonado-somatic indices were estimated. The mature females and males were longer than 49 and 45 mm in total length, and +2 and +1 in age, respectively. The spawning of Cobitis keyvani from the Talar River took place from May to late July, when the water temperature is between 18.7 to 24.0°C. The GSI values average at the beginning of the reproduction period was 10.09%, with ranged from 6 to 25% in ripe mature females. Based on the gonado-somatic index, it was concluded that the fish has a prolong active reproductive period. Their long reproductive activity is an adaptation by short-lived small fishes to environmental conditions.


The Cobitis genius fishes are represented in Iran by three valid species. These are Cobitis linea (Heckel, 1849), Cobitis faridpaki (Mousavi-Sabet, Vasil'eva, Vatandoust and Vasil'ev, 2011) and Cobitis keyvani (Mousavi-Sabet, Yerli, Vatandoust, Ozeren and Moradkhani, 2012). Cobitis faridpaki and Cobitis keyvani are found in south of the Caspian Sea basin. However, some researchers reported that the spined loach Cobitis tenia Linnaeus, 1758 is found also in the basin (Abdoli and

Naderi, 2009). While some others believe that the fish can't be C. taenia and C. taenia is rather northern European species and its occurrence in the southern Caspian Sea basin is unlikely (Kottelat and Freyhof, 2007). Cobitis linea Heckel, 1849 is found in the Kor River basin and the upper Kul River drainage of the Hormozgan basin (Banarescu and Nalbant, 1967; Bianco and Nalbant, 1980). Cobitis keyvani is one of the species of family Cobitidae and is an endemic fish from south of the Caspian Sea basin in north of Iran. This species is found in the lower streams of the Talar Rivers (Mousavi-Sabet et al., 2012). Species of this family are small benthic freshwater fishes with a wide distribution area covering large parts of Eurasia and Africa (Perdices and Doadrio, 1997). Spined loach during the day remains buried in sand, mud or dense weed growths, being active at night, and is mostly solitary (Coad, 2012). The loaches achieve sexual maturity in the first (males) or second (females) year of their life (Boron and Pimpicka, 2000; Marconato and Rasotto, 1989). Our main aim was to provide data on breeding season of the fish. This information is necessary for conservation programs of this endemic fish. We believed that the information of this small and colorful Loach is important because it may enter aquarium trade.

Materials and methods

The study was conducted in the Talar River in south of the Caspian Sea basin. Fish were collected from the river monthly from May 2009 to April 2010 by electrofishing (200-300 V). The specimens were immediately preserved in 4% formaldehyde until they could be examined. The fish were measured (Tl: total length, Sl: standard length to the nearest 0.1mm) and weighed (W: body weight, to the nearest 0.01 g). To examine the monthly changes in gonads as a mean for estimating the spawning season of this Loach, two indices were used: gonado-somatic index (GSI) and modified gonado-somatic index (MGSI). In order to determine the GSI (GSI=Wg/Wx100) (Nikolski, 1963) and MGSI (MGSI=Wg/W-Wgx 100) (Nikolski, 1963) ovaries were weighed (Wg) with 0.001 g accuracy. The sex was determined by using the external

dimorphic characteristics which Cobitis keyvani exhibits, include: females were longer and ponderous than males, a lamina circularis (Canestrini scale) was well developed at the base of the male pectoral fin, compared to females, males had much longer pectoral fins, length of pectoral fin in males fits 16.31 percent of SL, while in females length of pectoral fin fits 13.48 percent of SL. The Chi square test was used to assess deviation from a 50:50 sex ratio (Robards et al., 1999). The fish's age was assessed based on the annual growth of scales taken from the left side of the body, between end of the pectoral fin and the beginning of the dorsal fin. In order to compare significant differences in the GSI index between samples taken on various months and various size samples, the analysis of variance and Tukey's test were applied (p<0.05). The data were analyzed with the SPSS version 10.0 software package and Microsoft Excel 2010 software.


This fish, Cobitis keyvani, is commonly found in tributary streams of the Talar River. The bottom of these water bodies is generally sandy, silt and rubble (With diameter 5 to 45 cm), and the water is clear and slow running. The analysis of water in two different stations in May showed that the temperature was 17.8 to 19.6 °C with pH 6.9 -7.1, O2 5-9 mg/l and hardness 209 mg/l. During this study, 237 specimens of the Loach were caught ranging total length from 45.0 to 90.1 mm, standard length 37.3 to 81.5 mm and total weight from 0.5 to 6.1 g. The female specimens were longer and heavier than males and achieve maturity later than males, at the age of 2+, Tl more than 49 mm and body weight about 2 g. We observed significant differences in female and male GSI and MGSI in different months. There were no significant differences between GSI and MGSI. The female GSI increased during November to May, peaking at the mid of spring and decreased until August, then showed a slow increasing to October and finally decreased in November (Fig. 1). GSI pattern showed that reproductive period had a duration of 4 months, so this fish had prolong reproductive activity.

Figure 1: Variation of mean gonado-somatic index (GSI) and Modified gonado-somatic index (MGSI) of female (F) and male (M) Cobitis keyvani in different months from the Talar River


Females achieve maturity later than the males; at the age of 2+, Sl is about 56 mm and body weight about 2 g (Boron and Pimpicka, 2000; Robotham, 1981). The loach is a short-lived species, most of the caught fish were 2+ and 3+ years old, some were 1+ and 4+ and only a few of them were 5+ years old (Robotham, 1981). The oldest females (3.17%) among specimens in present study were 5+ years old but most of them (47.01%) were in the fourth year of their lives. This is the first study concerning reproduction process of Cobitis keyvani. Spawning of C. taenia takes place from May to July, usually in shallow littoral, among the submerged vegetation where the water temperature is at least 16-18°C (Boron and Pimpicka, 2000; Bialokoz, 1986). A similar time of spawning was observed for C. bilineata Canestrini from northern Italy (Marconato and Rasotto, 1989). A later spawning period (June-July) was observed for C. taenia from the United Kingdom (Robotham, 1981). Ekmekci and Erk'akan (2003) showed that the C. simplicispina from

Turkey begins to spawn in April, when the water temperature is 15° and finishes in May. The spawning period in the Talar River lasted until the late of July. A similar time is reported for Cobitis sp. from the Babolrud River in the same basin (Mousavi-Sabet et al., 2011a). As late as in late-July, in some females ovaries filled with oocytes were observed ready to be laid. However, in August, the ovaries of most of the loaches under study indicated end of the reproductive period. In Lake Zegrze, female loach's ovaries were filled with mature eggs in August (Boron and Pimpicka, 2000). The development stages of gonads did not correspond with the age and/or size of the examined females. The process of accumulating reserve substances in the ovaries of the females can be obtained partly by tracing the changes in the gonado-somatic index. In species which spawn in late spring and in summer such as loach, the index remains low in winter and then rises sharply just before the spawn (Marconato and Rasotto, 1989; Rinchard and Kestemont, 1996; Wootton, 1979). A rapid increase in the weight of ovaries takes place when the temperature rises and increasing amounts of food are consumed (Wootton, 1979). Changes in the gonado-somatic index, calculated for the population in which females spawn in batches, must not be used as the only credible indicator of the number of batches laid. The highest GSI values from 18% for the fish from Lake Lucien (Kostrzewa et al., 2003) to 26% in the loach from Italy (Marconato and Rasotto, 1989) were observed during the reproduction period. At the time, the values of GSI vary widely; from 4 to 26% for Cobitis sp. from Iran (Mousavi-Sabet et al., 2011a), from 2 to 20% for C. elongatoides from the Czech Republic (Halacka et al., 2000), from 12 to 26% for C. taenia from Italy (Marconato and Rasotto, 1989), but also lower from 7 to 17% for C. simplicispina from Turkey (Ekmekci and Erk'akan, 2003) or from 5 to 18% for Cobitis sp. from Lake Lucien (Kostrzewa et al., 2003) and from 5.2% to 12.2% for C. elongatoides from Hungary (Eros, 2000). In Cobitis keyvani from the Talar River, the highest average value of GSI (calculated in late April, before spawning) was about 10.09%, ranged from 6 to 25%.

Abdoli, A. and Naderi, M., 2009. The Biodiversity of Fishes of the Southern Basin of the Caspian Sea. Abzian Scientific Publication. Tehran. 238 pp. [In Persian]

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1980(4), 903-906.

Boron, A. and Pimpicka, E., 2000. Fecundity of spined loach, Cobitis taenia from the Zegrzyfiski Reservoir, Poland (Osteichthyes, Cobitidae). Folia Zoologica, 49 (Suppl. 1), 135-140.

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Ekmekci, F. and Erk'akan, G., 2003. Preliminary data on growth and reproduction of Cobitis cimplicispina from Turkey. Folia Biologica, 51 (Suppl.), 183-186.

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Halacka, K., Luskova, V. and Lusk, S., 2000. Fecundity of Cobitis elongatoides in the Nova Rise Reservoir. Folia Zoologica, 49 (Suppl.1), 141-150.

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Biologica, 51 (Suppl.), 179-182.

Kottelat, M. and Freyhof, J., 2007. Handbook of European Freshwater Fishes. Kottelat, Cornol, Switzerland and Freyhof, Berlin, Germany. xiii + 646 pp.

Marconato, A. and Rasotto, M. B., 1989. The biology of a population of spined loach

Cobitis taenia L. Bolletino del Museo di Zoologia, 56, 73-80.

Mousavi-Sabet, H., Kamali, A., Soltani, M., Bani, A., Esmaeili, H.R., Rostami, H., Vatandoust, S. and Moradkhani, Z. 2011a. Age, reproduction, and fecundity of a population of Cobitis sp. (Actinopterygii: Cypriniformes: Cobitidae) from the Babolrud River in the southern Caspian Sea basin. Acta Ichthyologica Et Piscatoria, 41 (2), 117-122.

Mousavi-Sabet, H., Vasil'eva, E.D., Vatandoust, S. and Vasil'ev, V.P. 2011b. Cobitis faridpaki sp. Nova-a New Spined Loach Species (Cobitidae) from the Southern Caspian Sea Basin (Iran). Journal of Ichthyology, 51(10), 925-931.

Mousavi-Sabet, H., Yerli, S.V., Vatandoust, S., Ozeren, S.C. and Moradkhani, Z. 2012. Cobitis keyvani sp. nova—a New Species of Spined-loach from South of the Caspian Sea Basin (Teleostei: Cobitidae). Turkish Journal of Fisheries and Aquatic Sciences, 12, 7-13.

Perdices, A. and Doadrio, I., 1997. Phylogenetic relationships and classification of the genera Cobitis and Sabanejewia (Cobitidae) based on allozyme data. Ninth International Congress of European Ichthyologists (CEI9) "Fish Biodiversity". Italy 1997 (Napoli-Trieste). Book of Abstracts, p. 71.

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Wootton, R. J., 1979. Energy costs of egg production and environmental determinants of fecundity in teleost fishes. Journal of the Zoological Society of London, 44,


The Effect of 17-alpha methyl testosterone on survival rate in Zebra Cichlid (Cichlasoma nigrofasciatum)


Hamed Mousavi-Sabet

Deptartment of Fisheries, Faculty of Natural Resources, University of Guilan, Someh Sara, Guilan, Iran. Mousavi-sabet@guilan.ac.ir


In the present study, effect of different dose rates of synthetic androgen 17-alpha methyl testosterone (MT) i.e. 30, 60, 100, 150, 200 and 300 mg of MT per kg of feed, on survival rate of Zebra Cichlid was evaluated. MT was administrated orally by using pellet dry starter and Ethanol Alcohol, diet to Cichlid fry for 40 days in glass aquaria. The larvae were also kept for 6 weeks after feeding. The results showed that high doses MT receiving treatments showed a significantly less survival rate than other experiments. No significant different was observed between control group, ethanol group, dose 30 and dose 60, but mortality in dose 100, 150, 200 and 300 mg MT /kg feed was significantly different between these groups and significantly higher than the other groups. Control and ethanol groups exhibited 0.83% and 0.0% mortality, respectively. Application of dose rates of 30 and 60 mg MT /kg feed showed 1.66% and 2.50% mortality, respectively. Also, in dose rates, 100 and which were more than 100 mg hormone/kg feed, mortality rate were significantly higher than other treatments. These results were interpreted as an indication that increasing concentrations of MT caused an increase in the mortality rate of zebra cichlid larvae.

Many species of ornamental fishes exhibit a marked sexual dimorphism and in most cases the male fish, due to their more heavily pigmented bodies and usually more developed fins, are preferred over the female fish by the hobbyists (Piferrer & Lim 1997). So, researchers decided to produce mono-sex and preferably all male population of cichlids, because the males grow faster than females (Barras & Melard 1997; Myers et al 1995; Tariq Ezaz et al 2004). There are different ways such as hormonal sex reversal, manual sexing, hybridization, and super male production to attain, mono sex population. Sex reversal by oral administration of feed incorporated with methyl testosterone (MT) is the most effective and practical method for the production of all male populations but the hormone makes an increasing in mortality in treated fish. Cichlids are an important group of relatively large and often colorful aquarium fishes. The family Cichlidae comprises about 105 genera and 1300 species, and it is the second largest family in the Perciformes order (Nelson 2006). Zebra Cichlid Cichlasoma nigrofasciatum is a medium-sized cichlid from Central America (Axelrod et al. 1971). In this study it was used as a model fish because of its wide range of tolerance to water hardness, pH and temperature. It is also easily obtainable and can be propagated inexpensively (Piferrer & Lim 1997). Under optimum conditions the fish produce large numbers of viable eggs (100-800 per batch). The development period from fertilization to hatching is very brief, approximating 3 days at 27C. This species also shows notable reproductive features, such as a complex social and breeding behavior, which includes parental care and, most importantly, a high spawning rate (about every 20 days during a9-month period). The aim of this study was, to find out the effect of different dose rates of MT treatment on survival rate of the Cichlid larvae.

Materials and methods

The hormonal treatment of zebra cichlid larvae was achieved by oral administration of 17-alpha methyl testosterone through feed. A stock of

C. nigrofasciatum, comprising males (mean weight: 3.53 ± 0.11 g; mean length: 67.04 ± 3.15 mm) and females (mean weight: 2.79 ± 0.14 g; mean length: 56.74 ± 4.73 mm) was procured from a local ornamental fish dealer. Variability in sex ratios among individual spawns in cichlids has been observed by Shelton et al. (1983). Therefore, three pairs from this stock were placed in three separate aquariums containing recirculating water (28±1oC) and exposed to a 16 (light): 8 (dark) photoperiod. All of the larvae used in these treatment studies were obtained from these pairs. These females had spawned -in an earthen jug- the eggs hatched approximately 3 days past fertilizing (dpf), and within 3 days the larvae had free swimming. The larvae were immediately removed from the aquariums, counted and placed in 24 small glass aquariums, each containing 40 liter of water that was continuously aerated with a 5-cm air stone and filtered by a normal sponge filter. Each experimental trial consisted of a control group and a group fed with ethanol treated diet (fish were fed with a diet treated with ethanol). Six different dosage groups, 30, 60, 100, 150, 200 and 300 mg of MT per kg of food (each in 3 replicates), were set out, MT was added to diet with Alcohol (Ethanol) dry method, and each trial was stocked with 40 fish. The larvae were fed daily with a commercial diet (dry starter pellet food with 40% crude protein) 6 times per day, for 40 days. Differences in mortality between groups was tested with the one-way analysis of variance by ranks (SPSS ver. 10.0 for Windows) followed by the Duncan non-parametric multiple comparison procedure.


Mortality of MT-treated fish; Table 1 is shown the survival rate of both control and MT-treated C. nigrofasciatum larvae. When considering mortality, no significant different was observed between control group, ethanol group, dose 30 and dose 60, but mortality in dose 100, 150, 200 and 300 mg MT /kg feed was significantly different between these groups and significantly higher than the other groups. Control and ethanol groups exhibited 0.83% and 0.0% mortality, respectively.

Application of dose rates of 30 and 60 mg MT /kg feed showed 1.66% and 2.50% mortality, respectively. Also, in dose rates, 100 and which were more than 100 mg hormone/kg feed, mortality rate were significantly higher than other treatments. These results were interpreted as an indication that increasing concentrations of MT caused an increase in the mortality rate.

Table 1. Effects of treatment with MT on the survival rate (mean ± SE) in C. nigrofasciatum

Dosage MT (mg/kg feed)

Survival rate (%)

Mortality rate (%)

0 (Control)



0 (Ethanol group)





















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