DOI: 10.2478/alife-2018-0022
EXPERIMENTAL REARING OF THE GOLDEN GRAY MULLET LIZA AURATA (RISSO, 1810) IN A RECIRCULATING SYSTEM AT THE BLACK SEA Victor Nicolae NITA1, Magda-Ioana NENCIU1, Carmen Georgeta NICOLAE2 1
National Institute for Marine Research and Development “Grigore Antipa”, 300 Mamaia Blvd., 900581, Constanta, Romania 2 University of Agronomic Sciences and Veterinary Medicine of Bucharest, 59 Marasti Blvd, District 1, 011464, Bucharest, Romania
Corresponding author email:
[email protected],
[email protected] Abstract Recirculating Aquaculture Systems (RAS) used in aquatic research and production are a viable alternative to traditional open-sea mariculture. The rearing of marine living resources in controlled environments is one of NIMRD’s constant concerns. Golden gray mullet Liza aurata (Risso, 1810) is spread in the Mediterranean, Black and Caspian Seas, as well as along the Atlantic coast, and culture in extensive and semi-intensive enclosures has been practiced worldwide for centuries, especially in the Far East and the Mediterranean, reaching a global production of 134,329 tons in 2010. The species’ potential for aquaculture is enhanced by its eurihalyne and eurithermal adaptability, allowing it to grow in a variety of ecosystems. The biological material used for the experiment was represented by golden gray mullet fingerlings fished using the beach seine from the Black Sea. They were monitored for health state, growth rythm (mean length and weight determinations), behavior under RAS conditions, survival rate and overall adaptability. The growth of juveniles after 90 days was 89.2% for total length and 246% for mean biomass. Concerning overall adaptability, after approximately one month, the golden gray mullet individuals fully adapted to rearing in the RAS tanks and handling during measurements. Moreover, the food administered (Skretting Classic K) was easily accepted, active feeding behavior being observed even in the presence of NIMRD’s staff. The fish’s health state was good, with no mortalities caused by infections or parasites. The survival rate upon completion of the two monitoring months was 76.66% (23 of the 30 individuals included in the experiment). The preliminary results obtained showed a good adaptability and a normal growth rate, which makes Liza aurata a potential candidate for aquaculture targeting the national and regional market. Keywords: golden gray mullet, mariculture, recirculating aquaculture systems (RAS).
and Development “Grigore Antipa”) constant concerns. The design of the seawater supply system is an extremely important condition in planning the incubation and rearing station of aquatic organisms, considering both economic and technological aspects (Niță et al., 2011). The knowledge of biological information of fish growth indicates the well-being and adaptation to the aquatic environment (StavrescuBedivan et al., 2016). A Recirculating Aquaculture System (RAS) is basically composed of three major units: the seawater absorption unit, the primary filtering (if necessary) and storage unit, and the secondary filtering and sterilizing unit (Muir and Roberts, 1999).
INTRODUCTION Recirculating Aquaculture Systems (RAS) used in aquatic research and production are a viable alternative to traditional open-sea mariculture. They are highly attractive in geographical areas where mariculture development is hampered by environmental conditions (Meske, 1985). As a follow-up of treating and reusing seawater, the recirculating system uses a much smaller amount of water and the resulting effluents do not pose a danger of contamination for the marine environment, while eliminating the major risk of storms (Landow, 1991). The rearing of marine living resources in controlled environments is one of NIMRD’s (National Institute for Marine Research 149
Seawater absorption There are three classical seawater absorption methods: direct pumping, “mining” and drilling. The most appropriate technique should be carefully selected, taking into account the conditions in the field, the topography and any other particular conditions in the area. The first two methods seem more appropriate for high capacity hatcheries, while the latter is suitable for small and medium-sized breeding stations. For the present research, the direct seawater pumping system connected to the laboratories of the National Institute for Marine Research and Development was used.
A prerequisite for these tanks is the smoothness of inner surfaces. A rugged surface of the tank is not recommended for sanitary issues, being a favorable factor for the formation of bacterial films, which can cause water degradation.
Primary filtration and storage tank Seawater absorbed from different depths crosses a pre-filter (containing a layer of anthracite 100 cm thick and 1.5 mm in diameter), and then is stored in tanks. Subsequently, water is pumped into the storage tanks of the rearing and breeding station.
Figure 1. Mechanical sand and quartz filters in NIMRD’s RAS (Photo: Nita V.)
Secondary filtration and sterilization Seawater is then filtered through the mechanical sand filter (Figure 1), containing anthracite 0.8 mm in diameter and sand with different grain sizes. Further on, the water passes through a 5 μm accuracy filtering cartridge (Figure 2). In order to minimize the pathogenic load, the filtered seawater is then UV sterilized and distributed to the various compartments of the system. Heating system A heating system is essential in order to obtain the best results in mariculture. As such, two sets of heaters were set-up, with capacities of 200 and 400 x 10³ kcal/min., respectively (a primary heater and a spare heater).
Figure 2. Automatic filtering cartridge in NIMRD’s RAS (Photo: Nita V.)
The diversity of production in fish culture by introducing valuable species, for which there is demand for consumption, is one of the main development directions of aquaculture (Costache et al., 2017).
Tanks In rearing marine living resources, various sizes and shapes of tanks can be used, both for the organisms used as feed, and for larvae and juveniles. Most of the times, round tanks are preferred, due to the fact that the circular driving of water pumped and the central location of the drainage allow an easy discharge of excessive organic matter, while not generating an overly strong water current (as is the case of rectangular tanks), which would cause unnecessary fatigue to the fish.
MATERIALS AND METHODS The golden gray mullet Liza aurata (Risso, 1810) (Figure 3) is widely distributed in the Mediterranean, Black, and southern Caspian Seas, as well as along the Atlantic coast from Scotland and the southern coast of Norway and Sweden south towards Morocco (Thomson, 1990). 150
Together with other members of the Mugilidae family, they inhabit coastal lagoons and estuaries, where they constitute target species for artisanal fisheries (Katselis et al., 2007). They also play a crucial ecological role as biotic vectors of organic matter between littoral habitats and the open sea (Lefeuvre et al., 1999).
fingerlings fished using the beach seine from the Black Sea (harvesting site - Mamaia Bay, September 2016). They were transported to NIMRD’s laboratory in sufficiently large tanks filled with seawater and provided with permanent air flow (Figure 4), and, after gradual temperature harmonization, carefully transferred in the experimental tank of the RAS (Figure 5).
Figure 3. Golden gray mullet Liza aurata (Risso, 1810) (Photo: Nenciu M.)
Figure 4. Fish transportation under strong air flow (Photo: Nita V.)
Mullet farming in extensive and semi-intensive ponds and reservoirs has been practiced worldwide for centuries, especially in the Far East and in the Mediterranean region (Crosetti and Cataudella, 1995), reaching a total global production of 134,329 metric tons in 2010 (FAO, 2012). Flathead grey mullet, Mugil cephalus, is the most important cultured mullet species. Liza ramada, Liza aurata, Liza saliens, Valamugil seheli and Chelon labrosus are cultured in the Mediterranean region and Liza parsia, Liza tade and Liza macrolepis are cultured in the Indo Pacific region (Pillay, 1990). Their potential for aquaculture stems from their euryhaline and eurytherm adaptability that allows them to grow well in a variety of ecosystems, from coastal lagoons with saline and brackish waters to freshwater ponds (Crosetti and Cataudella, 1995). Moreover, fry production is high in certain seasons, and their capture almost entirely supports seed supply for mullet aquaculture (Crosetti and Cataudella, 1995). Mullets are also commercially important; L. aurata fetches 4-6 €/kg on the Greek market (Hotos and Katselis, 2011). The biological material used for the experiment was represented by golden gray mullet
Figure 5. Golden gray mullet fingerlings during acclimation in the experimental rearing tank (Photo: Nita V.)
RESULTS AND DISCUSSIONS L. aurata fingerlings were monitored for health state, growth rhythm (mean length and weight determinations), and behavior under RAS conditions, survival rate and overall adaptability. Initially, the fish did not ingest food, which was provided in small portions, so as not to load the water with excessive organic matter during the acclimation period. The switch to inert feed (pellets) under captive conditions was gradual. The feed was represented by Skretting Classic K 1P pellets, grain size 2 mm in diameter and the following proximate composition (Table 1). 151
point when water temperature control started being implemented, keeping the temperature at a steady value of 19°C. Ten days after transportation, when all parameters were stabilized and fish fed actively, it was considered that the critical acclimation from natural conditions to NIMRD’s RAS had been successfully completed. It was then that the first measurements of the batch were performed, for fish total length and biomass determination. The mean values recorded were the following: Lmean= 9.3 mm Wmean = 8.3 grams The growth of juveniles after 90 days (upon completion of the experiment) was 89.2% for total length (from a mean of 9.3 mm at the beginnig of the trial, to 16.6 mm in the end) and 246% for mean biomass (from 8.3 g initially to 41 g mean biomass after three months) (Figures 8 and 9).
After 72 h, the seawater parameters in the tank were as follows: Ttank = 15.6°C; Stank = 14.4‰. At this point, a first intake of 12 g of fodder was given, according to the formula for this body size (Zaharia, 2002): daily intake = fish biomass x 2.5%. The complete consumption of the feed intake was observed after 24 h, and subsequently another quantity of 12 g of fodder was administered. It was noted that fish started eating regardless of human presence (Figures 6 and 7).
Figure 6. Mullet fingerlings after acclimation, actively feeding in the experimental tank (Photo: Nita V.)
Figure 8. Initial measurements of mullet individuals (Photo: Nita V.)
Figure 7. Daily feed intake dosage (Photo: Nita V.) Table 1. Proximate composition of the Skretting Classic K 1P pellets Composition Raw protein Raw lipids Raw fiber Raw ash Phosphorus Digestible energy (MJ/kg)
1st Period 43.0 11.5 4.0 9.0 0.8 14.0
2nd Period 40.0 11.5 4.0 8.5 0.8 13.6
3rd Period 31.0 9.0 4.0 8.5 0.8 11.8
Figure 9. Final measurements of mullet individuals (Photo: Nita V.)
Most certainly, the high growth rates recorded must take into account the fact that the fish used for the experiment were juveniles (fingerlings), thus having a very fast growth rate (Figure 10).
Virtually, it was after this point that we proceeded to daily feeding of the fish with the calculated intake of the fodder, avoiding any disturbance of the feeding rhythm. It was at this 152
which makes Liza aurata a potential candidate for aquaculture targeting the national and regional market. ACKNOWLEDGEMENTS This study has been carried out with financial support from the PROMARE Nucleu Programme, funded by the Romanian National Authority for Scientific Research and Innovation (ANCSI), project no. PN16230301.
Figure 10. Growth rate of golden gray mullets included in the experiment
REFERENCES
We estimate that the values will subsequently decrease, which will be monitored during later rearing of mullets in NIMRD’s tanks. Concerning overall adaptability, after approximately one month, the golden gray mullet individuals fully adapted to rearing in the RAS tanks and handling during measurements. Moreover, the food administered (Skretting Classic K) was easily accepted, active feeding behavior being observed even in the presence of NIMRD’s staff. Throughout the experiment, fish were very active (which is characteristic for the species). The fish’s health state was good, with no mortalities caused by infections or parasites. The survival rate upon completion of the three monitoring months was 76.66% (23 of the 30 individuals included in the experiment). However, mullets are known to be sensitive to handling, which causes loss of scales and makes them prone to bacterial and fungal infections resulting in mortality even several days after stocking (Yashouv, 1972; Dankwa et al., 2004). Certainly, the mortality rate observed in this study could be partially attributed to handling, in spite of the special care which was given to this activity. Moreover, transition from natural to artificial diets could also be considered a major factor affecting mortality.
Costache M., Bucur C., Costache M., Radu D., Nicolae C.G., 2017. Research on the use of different hormonal substances to stimulate maturation and ovulation in perch (Perca fluviatilis L.). Scientific Papers. Series D. Animal Science, Vol. LX, ISSN 2285-5750, 333-336. Crosetti D., Cataudella S., 1995. The mullets, In: C.E. Nash, A.J. Novotny (eds.). World Anim. Sci.Production of Aquatic Animals (fishes-C8). Elsevier Science, Amsterdam, Netherlands, 253-268. Dankwa H.R., Blay J., Yankson K., 2004. Potential for culture of grey mullets (Pisces: Mugilidae) in Ghana. Ghana J. Sci., 44: 19-27. Food and Agriculture Organization of the United Nation (FAO), 2012. FishStatJ - software for fishery statistical time series. Aquaculture Production 19502010 (Release date: March 2012). FAO, Rome, Italy. Hotos G.N., Katselis G.N., 2011. Age and growth of the golden grey mullet Liza aurata (Actinopterygii: Mugiliformes: Mugilidae), in the MessolonghiEtoliko lagoon and the adjacent gulf of Patraikos, Western Greece. Acta Ichthyologica Et Piscatoria, 41(3): 147-157. Katselis G., Koukou K., Dimitriou E., Koutsikopoulos C., 2007. Short-term seaward fish migration in the Messolonghi-Etoliko lagoons (Western Greek coast) in relation to climatic variables and the lunar cycle. Estuarine, Coastal and Shelf Science, 73:571-582. Landow M., 1991. Introduction to Aquaculture. Wiley Publishing, 440. Lefeuvre J.C., Laffaille P., Feunteun E., 1999. Do fish communities function as biotic vectors of organic matter between saltmarshes and marine coastal waters? Aquatic Ecol., 33:293-299. Meske C.P.B., 1985. Fish aquaculture: Technology and experiments. Pergamon Press, Oxford, 209. Muir J., Roberts, R., 1993. Recent Advances in Aquaculture IV. Blackwell Scientific, 340 pp. Niță Victor, Zaharia Tania, Maximov Valodea, Nicolae Carmen, 2011. Obtaining the necessary living food for rearing the turbot (Psetta maxima maeotica) in its early life stages. Scientic papers, Animal science, Bucharest, Seria D, Vol. LIV, 225-230. Pillay T.V.R., 1990. Aquaculture Principles and Practices. Blackwell Science. FishingNews books, Oxford, UK, 575.
CONCLUSIONS This first experimental stage aimed at testing mullet rearing in a recirculating system, under circumstances similar to Black Sea waters (target species - golden gray mullet Liza aurata). The preliminary results obtained showed a good adaptability and a normal growth rate, 153
Stavrescu-Bedivan Mala-Maria, Vasile Scaeteanu Gina, Madjar Roxana Maria, Manole Mali Sanda, Staicu Andrea Cristina, Aioanei Florin Teodor, Plop Eugen Florin, Toba George Leonard, Nicolae Carmen Georgeta, 2016. Interactions between fish well-being and water quality: a case study from MoriiLake area, Romania. Agriculture and Agricultural Science Procedia, Vol. 10, ISSN 2210-7843, 328-339. Thomson J.M., 1990. Mugilidae. In: J.C. Quero, J.C. Hureau, C. Karrer, A.Post, L. Saldanha (eds.). Checklist of the fishes of the eastern tropical Atlantic
(CLOFETA), Vol. II. UNESCO Paris, SEI Paris, JNICT Lisbon, 855-859. Yashouv A., 1972. Efficiency of mullet growth in fish ponds. IJA - Bamidgeh, 24: 12-25. Zaharia T., 2002. Research for elaborating the breeding and rearing technology for flounder and turbot, aiming at natural populations’ restoration. Food Chemistry and Fisheries Techniques Institute, “Lower Danube” University of Galati, Romania, 156 (PhD thesis - in Romanian).
154
