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Generally the gestation period in all of batches was 24-38 days. There was significant differences in gestation period among the two treatments. In addition, the comparison of survival rate of fish's larvaes in different treatments showed, 6ppt salinity cause to increase of survival rate of fry fishes in the first month of rearing (p<0.05) (table1).

Table1- fry mortality rate

Mortality Percentage

Mortality Number

Offspring Number

Treatment

12.89

58

450

A

7.23

35

484

B

Several investigators demonstrated the wide salinity tolerance of poeciliid fishes (P. reticulata, Arai et al 1998; Limia melanonotata, Haney and Walsh, 2003). In addition, many works documented the wild occurrence of P. latipinna in fresh and salt water environs such as rivers, ponds,lakes, mangrove swamps, coastal marshes, estuaries, and back waters (Schlupp et al., 1992). During acclimatization in the present study, normal feeding andswimming behavior indicated that the mollies were not under stress. In treatment B,the first spawning occurred as early as 10days after the initial stocking, perhaps indicatingthat embryos were in an advanced developmentstage at the start of experiment.

The main finding of this study was thatsalinity has a noticeable positive impact onthe breeding performance of P. Sphenops. Although young were released irregularly duringthe spawning, the gestation periodwas consistently recorded as 35 days in twotreatments. Similarobservations were made by Milton andArthington (1983) and Dawes (1991) whenone tablespoon of common salt per gallon ofwater was added to molly tanks. Gestationperiods are poorly documented in livebearingspecies. According to Milton and Arthington(1983), embryonic development in poeciliidsvaries 26-63 days. These authors reported onthe role of temperature and photoperiod butnot on salinity. Dawes (1991) reported that theoptimal temperature for reproduction of livebearersis 22-26°C.The highest fry production was in the treatment B with 6ppt salinity.

This salinity may beisosmotic to the body fluids of poeciliid fishesso that less energy was consumed forosmoregulation and more energy was availablefor growth and reproduction.

Arai F., Shikano, T. and Fujio, Y., 1998. An environmental factor stimulating salinity toleranceand branchial chloride cells in a euryhaline teleost Poecilia reticulata. Fish. Sci, 64:329-333.

Bennett, W.A,. and Beitinger, T.L., 1997. Temperature tolerance of sheepshead minnow

(Cyprinodon variegatus), Copeia,1997(1):77-87.

Claireaux, G., and Lagardere, J.P., 1999.Influence of temperature, oxygen and salinity on the metabolism of the European sea bass. J. Sea Res, 42:157-168.

Dawes J.A., 1991. Livebearing Fishes: A Guide to their Aquarium Care, Biology and Classification. Blandford Publ., London. 240 pp.

Duncan D.B., 1955. Multiple range and multiple F-tests. Biometrics, 11:1-42.

Ghosh, S., Sinha, A., Sahu, C., 2008. Bioaugmentation in the growth and water quality of livebearing ornamental fishes. Aquacult Int, 16:393—403.

Haney, D.C. and Walsh, S.J., 2003. Influence of salinity and temperature on the physiology of Limia melanonotata (cyprinodontiformes: Poeciliidae): A search for abiotic factors limitinginsular distribution in Hispaniola. Caribb. J. Sci,

39(3):327-337.

Milton, D.A. and Arthington,A.H. 1983. Reproductive biology of Gambusia affinisholbrooki(Baird and Girard), Xiphophorus helleri (Gunther) and X. maculatus (Heckel) (Pisces;Poeciliidae) in Queensland, Australia. J. Fish Biol.,

23:23-41.

Schlupp, I., Parzefall, J., Epplen, J.T., Nanda, I., Schmid, M. and Schartl, M. 1992.

Pseudo male behavior and spontaneous masculinization in the all-female teleost Poecilia formosa(Teleostei: Poeciliidae). Behaviour, 122:88-104.

Sudha,c., 2012. Study on induced breeding in ornamental fish (poecilia sphenops). European Journal of Experimental Biology, 2 (4):1250-1255.

Vannuccini, S., 2004. Overview of fish production, utilization, consumption and trade. FAO, Fishery Information, Data and Statistics Unit. Food and Agriculture Organization of the United Nations, Rome, Italy.

Use of carotenoids in aquaculture (With emphasis on reproduction of ornamental fishes)

Bahremand, M., Pirbeygi, A., Farhangi, M., Naserizadeh, M.

Department of Fisheries, Faculty of Natural Resource, University of Tehran, Karaj, Iran Bahremand.m@ut.ac.ir

Introduction

An appropriate balance of internal essential nutrients in the egg significantly affect the early development of larval fish. Maternal diet prior to and during oogenesis is a crucial issue in this regard (Laevens et al., 1999). Astaxanthin as an important pigment significantly affect the growth and development of embryo and substantially improve the fertilization rates of broodstocks (Ansari et al., 2011). The concentrations of this carotenoid in the egg could be used as a suitable indicator to assess the quality of egg (Hartman et al.,1947). Many studies suggest that carotenoids have a major role in normal embryonic development. In addition, they affect hatching and survival rates over larval period (Ansari et al., 2011).

Carotenoids and carotenoid-protein complexes are stored in the skin and muscle of most fish including ornamental fish (Velasco-Santamaria and Corredor-Santamaria, 2011). Producing different ornamental fish species with divers color is an important issue in aquaculture industry. However, astaxanthin can only be synthesised by plants, microalgae, zooplankton and crustaceans. Fish like other animals, can not synthesize carotenoids de novo (Chatzifotis et al., 2005), That is why it is important. to add carotenoids in the diets as important additives.

A number of studies have been conducted to assess the dietary inclusion of carotenoid in ornamental fish such as goldfish and koi carp (Hancz et al., 2003; Gouveia and Rema, 2005), neon serpae tetra (Wang et al., 2006), and guppies (Grether et al., (1999). However, the number of studies regarding the effect of carotenoids on egg quality and larval growth of ornamental fish are scarce in the literature .

Carotenoid sources

More than 600 carotenoids have been identified in the nature. However, only 50 of them have shown provitamin A activity (Olson, 1989). Carotenoids are synthesized from geranyldiphosphate by all photosynthetic organisms (Mirzaee et al., 2012). Cyanobacteria (bluegreen algae such as Spirulina), dried shrimp meal, shrimp and palm oils, and extracts from marigold, red peppers, mold and Phaffia yeast are excellent natural sources of carotenoids.

Fig. 1.Chemical structure of two carotenoids.

The synthetic astaxanthin is a potent carotenoid which is used as an additive in fish diets (100-400 mg/kg), However, the high cost involved in providing synthetic pigments has limited their wide use at farm level. Nowadays, there is a great interest to find the natural sources of carotenoids around the glob. Different microalgae contain a wide varity of nutrients, They are important in production of larval fish and can be used as natural source of pigments in fish diets.

Chlorella vulgaris as one of the most effective astaxanthin sources, significantly improved the skin color intensity in ornamental fish (Velasco-Santamaria and Corredor-Santamaria, 2011). The high efficiency of C. vulgaris was attributed to good bioavailability of carotenoids and the thin cell membrane of C. vulgaris.

The pigmentation efficiency widely varies in natural and synthetic carotenoids. Supplementation of the diet by C. vulgaris led to good skin

pigmentation in goldfish. However, the pigmentation rates was signficanly improved when snnthetic astaxanthin was added in the diet (Gouveia and Rema, 2005). Sinha and Asimi (2007) investigated four natural sources of carotenoid in goldfish (Spirulina, China rose petals, Marigold petals and Lactobacil). Result showed the superiority of China rose petals in terms of skin pigmentation and gonadal development. Ezhil et al (2008) studied the dietary effect of marigold petal meal in swordtail. They showed that marigold petal meal (with lutein pigment) can be used as a suitable source of pigments in fishe diets. Nevertheless, the growth, feed efficiency and survival rate were not affected by dietary supplementation of natural or synthetic carotenoid in some fish species

(Wang et al., 2006).

Mode of action

Carotenoids (e.g. P- and a-carotene, astaxanthin and canthaxanthin) must be cleaved to yield retinol or other forms of vitamin A to serve as provitamin A compounds. The manner for transporting of Carotenoids is analogous. Although endocrine and nervous system control the coloration, another factor in determination of the color of fish are dietary sources of pigments. The effectiveness of carotenoid sources in terms of deposition and pigmentation is species specific. Moreover, all fish species do not have the same pathways for the metabolism of carotenoid. Therefore, transformation of carotenoids in fish tissues is not universal (Chatzifotis et al., 2005). Absorption and accumulation of astaxanthin in ornamental fishes is higher than other carotenoids (Mirzaee et al.,2012). HDL fraction appears can be important for transporting carotenoids from the muscle to the skin during spawning times in salmonids,. Similarly, transport of vitellogenin in VHDL corresponds to a large pool of carotenoids to eggs (Lubzens et al., 2003). In addition, the transport of VTG has been shown to correspond with deposition of retinoids in eggs

(Irie and Seki, 2002).

Gross and Budowski (1966) found evidence for the conversion of astaxanthin, canthaxanthin and zeaxanthin via P-carotene to vitamins A1

and A2 in guppies and platties. In freshwater fish in which more vitamin A2 is normally present, more zeaxanthin and lutein exist in eggs (Hata and Hata, 1971). Lubzens et al. (2003) reviewed studies which quantified concentrations of carotenoids in fish eggs and showed that eggs from freshwater teleosts contain less than 1 mg carotenoids per gram of dry egg weight. While, eggs from marine teleosts contained 10-25 mg/g. Commonly, marine and freshwater teleosts contain 2-14 mg retinal per dry gram of eggs, 0.5 to 7 mg/g of retinol and retinol esters. It appears that marine teleosts have slightly higher proportions of retinal and dehydroretinal than freshwater teleosts. The role of vitamin A and carotenoids for determining egg and early life stage quality has been a controversial subject for over 50 years (Izquierdo et al., 2001). The few available carefully designed studies suggest that better egg condition and increased measures of survival are associated with enhanced concentrations of some carotenoids. Salmonids generally take up carotenoids, predominantly, canthaxanthin and astaxanthin, from the diet and deposit them in muscle. These stores can then be mobilised to eggs via VHDL or high density lipoproteins (Torrissen and Christiansen, 1995). This active transfer has shown that carotenoids are critical to egg and larval developments (Torrissen and Christiansen, 1995). Generally, carotenoids are more concentrated in eggs of salmonids in which post-fertilisation development takes place in low oxygen environments than in eggs that develop in a pelagic environment. In these cases it has been suggested that carotenoids help eggs to develop more adequately in low oxygen environments.

Torrissen (1984) found that fry fed unsupplemented feed grew slower than fry fed with astaxanthin- and canthaxanthin-supplemented feed (30 mg/kg). Hoff (1996) attributed hatching success and viability in clownfish larvae to the egg pigmentation. The carotenoids are also one of main factors which are important to influence immune system in fishes (Thompson et al. 1994). The improved larval survival may also be due to the vitamin A activity of the carotenoids, as they form precursor to vitamin A, which in turn can increase the visual capabilities of the larvae and thereby resulting in increased prey strike success.

Among carotenoids, astaxanthin is one of the most important carotenoids which is known to influence the egg quality in many fishes (Watanabe and Miki 1993). The importance of carotenoids in the egg and larval quality in sebae anemonefish can be shown through the active mobilization of dietary carotenoids to develop eggs within a short span (< 48 hrs) (Binu Varghese 2004). Numerous functions such as UV protection, provitamin A activity, improved respiratory function (Ansari et al., 2011) and antioxidant protection against free radical damage (Edge et al., 1997) have been proposed for carotenoids in fish eggs. Carotenoids are important in ensuring normal embryonic development and could also affect hatching rates and larval survival (Ansari et al., 2011). Carotenoids may be involved in photoreception processes (Pan et al., 2001).

Carotenoid content of eggs and its color is full depended on amount of carotenoid stored in egg during yolk formation. Species with large eggs require higher amounts of pigment than those with small eggs and there is a correlation between the time of emberyonic development and the concentration of carotenoids in eggs (Kitahara, 1983).

Future studies

A number of research should be conducted to find new carotenoid sources in microalgae, plants and animals. In addition the mode of action of various carotenoids (both natural and synthetic) in different fish species should be further explored in the future.

References

Ansari, R., Alizadeh, M., Shamsai, M., and Khodadadi, M. 2011. The effects of algal and synthetic astaxanthin (Heamatococcus pluvialis) on egg guality of Rainbow trout broodstock (Oncorhynchus mykiss). World journal of fish and marine sciences., 3(6): 539-547.

Binu Varghese, 2004. Nutritional studies on sebae anemonefish, Amphiprion sebae Bleeker 1853, with special reference to protein and lipid requirements. Ph. D. Thesis, Central Institute of Fisheries Education, Mumbai, 192 pp.

Chatzifotis, S., Pavlidis, M., Jimeno, C.D., Vardanis, G., Sterioti, A., and Divanach, P. 2005. The effect of different carotenoid sources on skin coloration of cultured red porgy (Pagrus pagrus). Aquaculture research, 36: 1517-1525.

Edge, R., McGarvey, D.G., Truscott, T.G. 1997. The carotenoids as anti-oxidant -a review, J, Photochemistry and photobiol. Biol, 41: 189-200.

Ezhil, J., Jeyanthi, C., Narayanan, M. 2008. Effect of formulated pigmented feed on colour changes and growth of red swordtail, Xiphophorus helleri. Turk J Fish Aquat Sci, 8(1):

99-101.

Gouveia L. and P. Rema, 2005. Effect of microalgal biomass concentration and temperature on ornamental goldfish (Carassius auratus) skin pigmentation. Aquac. Nutr., 11:19-23.

Grether F.G., Hudon J. and F.D. Millie, 1999. Carotenoid limitation of sexual coloration along an environmental gradient in guppies. Biol. Sci., 266:1317-1322.

Gross, J. and P. Budowksi. 1966. Conversion of carotenoids into vitamin A1 and A2 in two species of freshwater fish. Biochem. J., 101: 747-754.

Hancz C., Magyary I., Molnar T., Sato S., Horn P. and N. Taniguchi, 2003. Evaluation of color intensity enhanced by paprika as feed additive in goldfish and koi carp using computer-assisted image analysis. Fish. Sci., 69:1158-1161.

Hartman, M., Medem, F.G., Kuhn, R., Bielig, H.J. 1947. Untersuchngen uber die berfruchtungs stoffe der regenbogeforellle. Z. Naturforsch, 2: 330-343.

Hata, M. and M. Hata. 1971. Carotenoid pigments in goldfish (Carassius auratus). I. composition and distribution of carotenoids. Int. J. Biochem., 2: 11-19.

Hoff, F.A. 1996. Conditioning, spawning and rearing of fish with emphasis on marine clownfish. Aquaculture Consultants Inc. USA. 212 pp.

Irie T., and T, Seki. 2002. Retinoid composition and retinal localisation in the eggs of teleost

fishes. Comp. Biochem. Physiol., 131B: 209-219.

Izquierdo, M.S., H. Fernandez-Palacios and A.G.J. Tacon. 2001. Effect of broodstock nutrition on reproductive performance of fish. Aquaculture., 197: 25-42.

Kitihara, T. 1983. Behaviour of carotenoids in the chum salmon (Oncorhynchus keta) during anadromous migration. Comp. Biochem. Physiol., 76B: 97-101.

Laevens, P., E. Lebegue, H. Jaunet, A. Brunel, P. Dhert and P. Sorgeloos. 1999. Effect of dietary essential fatty acids and vitamins on egg quality in turbot broodstocks. Aquacult. Internat.,

7: 225-240.

Lubzens, E., L. Lissauer, B. Levavi-Sivan, J.-C. Avarre and M. Sammar. 2003.Carotenoid and retinoid transport to fish oocytes and eggs: what is the role of retinol binding protein. Mol.

Aspects Med., 24: 441-457.

Olson, J.A. 1989. Provitamin A function of carotenoids: the conversion of b-carotene into vitamin

A. J. Nutr., 119: 105-108.

Pan, C.H., Chien, Y.H., Cheng, J.H. 2001. Effects of light regime algae in the water and dietary astaxanthin on pigmentation, growth and survival of black prawn Penaeus monodon post

larvae. Zool. Stud, 40: 371-382.

Sinha, A., and Asimi O.A. 2007. China rose (Hibiscus rosasinensis) petals: a potent natural carotenoid source for goldfish (Carassius auratus L.). Aquacult Res, 38(11): 1123-1128.

Thompson, I., T. C. Fletcher, D. F. Houlihan and C. J. Secombes. 1994. Effect of dietary vitamin A intake on the immunocompetence of Atlantic salmon (Salmo salar). Fish Physiology

and Biochemistry 12: 513-523.

Torrissen, O.J. 1984. Pigmentation of salmonids- effect of carotenoids in eggs and start-feeding diet on survival and growth rate. Aquaculture, 43: 185-193.

Torrissen, O.J., and R, Christiansen. 1995. Requirements for carotenoids in fish diets. J. Appl.

Ichthyol., 11: 225-230.

Velasco-Santamaria, Y., and Corredor-Santamaria, W. 2011. Nutritional requirements of freshwater ornamental fish: a review. Rev. MVZ Cordoba., 16(2): 2458-2469.

Wang, Y.J., Chien, Y.H., and Pan, C.H. 2006. Effects of dietary supplementions of carotenoids on survival, growth, pigmentation, and antioxidant capacity of characins, Hyphessobrycon callistus, Aquaculture, 261(2): 641-648.

Watanabe, T and W. Miki. 1993. Astaxanthin; An effective dietary component for red sea bream broodstock. In: Fish Nutrition in Practice (ed. Kaushik, S.J. and Luquet), PINRA, Paris,

pp 27-36.

Biofloc, a prospective technology for increasing the efficiency of fish and shrimp larviculture in Iran

Farideh Bakhshi1, Vafa Farahmandi1 and Reza Malekzadeh-Viayeh2*

1 Department of Fisheries and Aquaculture, Faculty of  Natural Resources, Urmia University, Urmia, Iran

2 Artemia and Aquatic Animals Research Institute, Urmia University, Urmia, Iran. * r.malekzadeh@urmia.ac.ir

Introduction

Larviculture is a critical stage in the production of aquatic organisms. Development of fish and crustacean larviculture worldwide is restricted mainly due to the lack of sufficient and/or high-quality water and feed items (Cahu & Zambonino Infante, 2001). Feed comprises more than 50 percent of operating costs of aquaculture systems (Asaduzzaman et al., 2010). On the other hand, water shortages in semiarid regions such as Iran have limited the expansion of aquaculture industry. Thus, the pivotal challenges in the future would be to supply adequate amounts of water and feed and to increase the feeding efficiency in marine larviculture. One way to tackle this problem is to establish a self-sustained system in which water is purified and a continuous feed supply is guaranteed. Although such system has not yet been setup in large scale, it is predictable that it will play more significant roles in the future. In this article, a novel biotechnological approach for minimizing water and feed requirements in larviculture of aquatic animals is introduced.

Biofloc technology

The 'Biofloc technology' (BFT) gets its name from the capacity of microorganisms for flocculating organic matters (Mahanand & Srinivasa Rao, 2012). The technology is based on inorganic nitrogen assimilation into heterotrophic bacterial biomass (Azim et al., 2008); Nitrogenous wastes produced in a culture system (i.e. as faces, feed remains and decayed dead organisms) are decomposed by certain groups of bacteria,

resulting in the production of less toxic products. On the other hand, folliculated organic products can be as a food source for the cultured animals, e.g. fish and shrimp (De Schryver et al., 2008). Invention of biofloc technology seems to be inspired from fish pond systems which depend mainly on the exploitation of autotrophic (mainly microalgae), heterotrophic (mainly detritus-associated bacteria) and microbial (bacteria, protozoa, fungi) food webs (Azim et al., 2008). The heterotrophic food web consistently appears as a major contributor to the total production of target animals (Azim et al., 2008).

Fig. 1. Transformation of organic matters and production of nitrogen and carbon in a fish culture system (De Schryver et al., 2008).

The bacteria need adequate amounts of carbon for their functions. This carbon is usually supplied from an external source. Thus, a suitable carbon to nitrogen ratio (C:N) should be provided for efficient operation

of the system (Azim et al., 2008). The C:N controls in biofloc systems can be accomplished by reducing feed protein contents (Azim et al., 2008), or adding inputs with the appropriate C:N ratio to stimulate heterotrophic bacterial growth (Taw, 2010). Figure 1 shows that how fish farming practice can result in the production of nitrogen and carbon. In fact, it indicates the process by which organic matters are transformed into nitrogen and carbon in a natural pond system. Avnimelech (2007) found that the levels of inorganic nitrogenous wastes are reduced through microbial assimilation, by the addition of extra carbonaceous materials.

How does the system work?

A biofloc system is comprised of hundreds of bacterial nuclei having the size range from 100 to 200 um (Azim et al., 2008). It may also contain different types of algae, protozoa, rotifers, etc. in the sizes between 10 and 100 um (Mahanand & Srinivasa Rao, 2012). The bacteria comprise an important part of the food chain in a bioflo system (Avnimelech, 2009), while the other components of the ststem, e.g. zooplanktons, can grow by grazing on bacteria and consequently, supply additional feed for the cultured animals. Figure 2 indicates the simple mechanism of transformation of feed and wastes into the folliculated particles which can then be used as food sources for the farmed fish. As is shown in the figure, bioflocs are integrated within the culture unit by using feed with a relatively low N content and/or the addition of a carbon source. The bioflocs consume inorganic N waste together with the carbon source, thereby producing microbial biomass that can be used as a feed by the animals (Fig. 2A). By using a separate bioflocs reactor, the waste water from the culture tank is brought into the biofloc reactor, where a carbon source is added in order to stimulate biofloc growth. The water of the biofloc reactor can be recirculated into the culture tank and/or bioflocs can be harvested and used as a supplementary feed (Fig. 2B). Inorganic nitrogen control is based on an enhancement of heterotrophic bacterial growth to assimilate nitrogen into new cellular proteins (Azim & Little, 2008). Fish tank effluents are continuously pumped into the

biofloc reactor in which bacterial flocs are produced by vigorous agitation and aeration with a dome diffuser and carbon supplementation. As bacterial biomass increases, reaching a high density, they tend to form noticeable aggregates (bioflocs), which can be consumed by cultured animals as a natural food source (Azim & Little, 2008). Furthermore, the flocculated particles are passed through a floc separator in which flocs are settled and removed periodically and processed for formulated feed. The clean water containing controlled amounts of bioflocs is pumped to the fish tanks again (Azim & Little, 2008).

Addition of carbon and nitrogen sources, at a high C:N ratio, into the aquaculture ponds was recommended for the establishment of bioflocs and control of inorganic nitrogen concentration (De Schryver et al., 2008). The C:N ratio in an aquaculture system can be increased by adding different locally available cheap carbon sources such as glycerol, molasses and cornmeal.

A

Culture unit i- a&ratior and Mining}

{ \0 3i.mx

^ | C source J Irorgaiic H^r--^"^

C J til re unit Bioflocs reactor (aeration +- mixi ig)

Inorganic N

Fig. 2. Schematic illustration showing how bioflocs can be implemented in aquaculture systems (Craba et al., 2012).

Discussion and Conclusions

Biofloc technology is applicable to extensive as well as intensive aquaculture systems (Craba et al., 2012). It produces low cost bioflocs rich in protein, which in turn can serve as a feed for aquatic organisms (De Schryver et al., 2008). The efficiency of protein utilization is twice as high in biofloc technology compared to the conventional aquaculture systems (Craba et al., 2012). Azim et al. (2008) found that biofloc quality was independent of the quality of feed applied to a fish culture pond, and contained more than 50% crude protein on dry matter basis. The dietary composition and size of biofloc can be considered as appropriate for all omnivorous fish species. However, the underlying ecological processes can be explained through factor analysis.

The production and potential use of heterotrophic bacteria by using fish wastes concurrently improve water quality in the proposed indoor systems and would be a prospective technology to lower nutrient discharge and to increase nutrient retention, thereby ensuring its future sustainability (Azim & Little, 2008). A preliminary study indicated that microbial flocs generated in bioreactors using fish waste and offered as supplemental feed, improved shrimp growth (Kuhn et al., 2007). At present, biofloc system is a highly sought technology for Pacific white shrimp culture due to high efficiency, productivity, sustainability and lowering feed convention ratio (Taw, 2010). This system has been susccessfully applied for several fish species including common carp, Cyprinus carpio (Jana & Sahu, 1993), rohu, Labeo rohita and gonia, Labeo gonius (Azim, et al., 2001), black sea bass, Centropristis striata (Bender et al., 2004), Nile tilapia, Oreochromis niloticus (Asaduzzaman et al., 2009) and European sea bass, Dicentrarchus labrax (De Schryver et al., 2010). In addition, the heterotrophic microbial biomass is suspected to have a controlling effect on pathogenic bacteria (Asaduzzaman et al., 2010), and can improve disease protection in the cultured organisms (Viti and Giovannetti, 2005).

A major obstacle to the use of biofloc technology is to convince farmers to implement the technique, since the concept of biofloc

technology goes in against common wisdom that water in the pond has to be clear (Avnimelech, 2009). Despite this, several factors promote the implementation of the technique. Firstly, water has become scarce or expensive to an extent of limiting aquaculture development. Secondly, the release of polluted effluents into the environment is prohibited in most countries. Thirdly, severe outbreaks of infectious diseases led to more stringent biosecurity measures, such as reducing water exchange rates (Avnimelech, 2009). Biofloc technology provides a more economical alternative for traditional aquaculture activities (De Schryver et al., 2008; Avnimelech, 2009). Experience regarding biofloc technology and technical knowledge about the technique needs to be transferred to the farmers in a clear, practical and straightforward way, not forgetting to emphasize the economic benefits of this technique.

The simplified idea of recycling excreta of aquatic organisms into feed might frighten the consumers and prohibit them from buying these products. Despite this hitch, it is clear that with the growing human population, technological progress in aquaculture is needed to protect wild fish stocks and control fish prices (Jiang, 2010). Population growth pushes up fish prices as a result of a seafood shortage and increases pressure on wild fish stocks (Peron et al., 2010). In contrast, technological improvement tends to decrease fish prices and increases wild fish stocks by making the alternative fish product, farmed fish, relatively easier to produce. Therefore, biofloc technology could alleviate the depletion of wild fish stocks and poverty, while improving social welfare through lowering the fish production prices, all beneficial for both farmer and consumer. Moreover, consumers now call for guarantees that their food has been produced, dealt with and commercialized in a way that is not hazardous to their health, respects the environment and addresses diverse other ethical and social considerations (Craba et al.,

2012).

In addition to biofloc technology on its own, several researchers are looking at combinations of this technology with other innovative techniques to improve efficiency of aquaculture. Nevertheless, clear understanding of the microbiological aspects particularly bacteria growth

patterns, characterization of biofloc and possible manipulation of microbial community is necessary for the successful design and operation of such technologies (Azim & Little, 2008).

References

Asaduzzaman, M., Wahab, M.A., Verdegem, M.C.J., Huque, S., Salam, M.A., Azim, M.E. (2010) C/N ratio control and substrate addition for periphyton development jointly enhance freshwater prawn Macrobrachium rosenbergii production in ponds. Aquaculture 280, 117-123.

Asaduzzaman, M., Wahab, M.A., Verdegem , M.C.J., et al. (2009) Effects of addition of tilapia Oreochromis niloticus and substrates for periphytondevelopments on pond ecology and production in C/N-controlled freshwater prawn Macrobrachium rosenbergii farming systems. Aquaculture 287, 371-380.

Avnimelech, Y. (2009) Biofloc Technology - A Practical Guide Book. The World Aquaculture Society,Baton Rouge, Louisiana, United States. 182 pp.

Azim, M.E., Little, D.C. (2008) The biofloc technology (BFT) in indoor tanks: Water quality, biofloc composition, and growth and welfare of Nile tilapia (Oreochromis niloticus). Aquaculture 283 29-35.

Azim, M.E., Little, D.C., Bron, J.E. (2008) Microbial protein production in activated suspension tanks manipulating C:N ratio in feed and the implications for fish culture. Bioresource Technology 99 3590-3599.

Azim, M.E., Wahab, M.A., van Dam, A.A., Beveridge, M.C.M.,Verdegem, M.C.J. ( 2001) The potential of periphyton-based culture of two Indian major carps, rohu Labeo rohita (Hamilton) and gonia Labeo gonius (Linnaeus). Aquac Res 32, 209-216.

Bender, J., Lee, R., Sheppard, M., Brinkley, K., Philips, P., Yeboah, Y., Wah, R.C. (2004) A waste effluent treatment system based on microbial mats for black sea bass Centropristis striata recycled water mariculture. Aquac Eng 31, 73-82.

Cahu, C., Zambonino Infante, J. (2001) Substitution of live food by formulated diets in marine fish larvae. Aquaculture 200, 161-180.

Craba, R., Defoirdta, T., Bossierb, P., Verstraete, W. (2012) Biofloctechnology in aquaculture: Beneficial effects and future challenges. Aquaculture, 351-356.

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Gonadosomatic index and egg diameter variations in the Iranian cichlid, Iranocichla hormuzensis

Ehsan Daneshvar* and Yazdan Keivany

Department of Natural Resources, Isfahan University of Technology, Isfahan 84156-83111, Iran, E-mail: keivany@cc.iut.ac.ir

Abstract

The reproductive biology of the Iranian cichlid, Iranocichla hormuzensis was investigated for 13 consecutive months in lower Mehran River, from August 2008 through August 2009. Four hundred and eighty six individuals (252 males and 234 females) were captured using a seine net (5mm mesh size). The observed sex ratio was 1:0.93 (Males:Females) (x2, df = 1, P = 0.414). Mean±SD of total length (TL) values in females and males were 62.08 ±6.51 and 70.34±8.16mm, respectively. A gonadosomatic index (GSI) analyses of females indicated that the reproductive period was during February-June, with a peak in March. The absolute fecundity ranged between 48-167 eggs with a Mean±SD of 107 ± 35.2. Egg diameters ranged from 0.58 to 2.93 mm. Fecundity was best correlated with total body mass (M) (linear regression, r2 = 0.6194) condition factor (linear regression, r2 = 0.6149) and total length (TL) (linear regression, r2 = 0.5629).

Keywords: Biology, Fecundity, Gonadosomatic index, Mehran River, Reproduction

Introduction

Cichlids comprise about 150 genera and 1300 species, making it the second largest perciform family (Nelson, 2006). Cichlid fishes have a worldwide distribution and they are found in fresh and brackish waters of

Central and South America, Africa, Madagascar, the Levant, southern India, Sri Lanka and southern Iran. The Iranian cichlid, Iranocichla hormuzensis Coad, 1982, is the only endemic species of cichlids in Iran (Coad, 1982; Berra, 2001). This species found in Fars and Hormuzgan provinces (southern Iran) in rivers with warm and salty water (Esmaeili et al., 2008). They are recognized by the darkened rays and lack of spots in the pectoral fin and specially, by the single nostril opening on each side of the head (Coad, 1982). Esmaeili et al., (2008) investigated some aspects of biology of I. hormuzensis in the upstream of Mehran River. In this study we present information on the gonadosomatic index (GSI) and fecundity of I. hormuzensis from lower Mehran River.

Materials and Methods

The sampling area was the Dezhgan in Mehran River in Hormuzgan province. The bottom structure of this area was sandy-muddy. During August 2008 and August 2009, a total of 486 individuals were captured with seine net by searching the substrate for 120 to 150 minutes. The specimens were transported in 10% formalin to the laboratory for further examination.

Gonads were removed and weighed with a digital scale at an accuracy of 0.001g. For determine the reproductive cycle and the breeding season of the fish, we measured gonadosomatic index (GSI = 100 Gonad Mass/ Body Mass) and modified gonadosomatic index (MGSI =100xGonad Mass /Fish Mass- Gonad Mass) (Nikolsky 1963), Dobriyal index (DI = VGW ) (Dobriyal et al. 1999) and RC= GW/TL (Way et al. 1998) where GW is gonad mass in g and TL is total length of fish in mm.

The absolute fecundity, as the number of mature ova likely to be spawned, was calculated using ripe ovaries with higher gonadosomatic index by the method of Batts (1972). Fecundity was estimated from 15 fish in the ripe macroscopic stage. The ovaries were placed in Gilson's solution. The egg diameter of preserved in 4% formalin solution was measured using an ocular micrometer.

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