The experimentalORIGINAL rearing SCIENTIFIC of Noah’s Ark, PAPER Arca noae (Linnaeus, 1758) and Bearded Horse Mussel, Modiolus barbatus (Linnaeus, 1758) in Mali Ston Bay The experimental rearing of Noah’s Ark, Arca noae (Linnaeus, 1758) and Bearded Horse Mussel, Modiolus barbatus (Linnaeus, 1758) in Mali Ston Bay Valter KOŽUL, Nikša GLAVIĆ, Jakša BOLOTIN, Nenad ANTOLOVIĆ Institute for Marine and Coastal Research, D. Jude 12, P.O. Box 83, 20000 Dubrovnik, Croatia, (e-mail: [email protected]) Abstract The growth rate of shellfish bivalve, noah’s ark, Arca noae (Linnaeus, 1758) and bearded horse mussel, Modiolus barbatus (Linnaeus, 1758) was investigated under commercial conditions at a shelfish farm in Mali Ston Bay. In February 2007. juvenile stages of A. noae (average shell length of 21.70±7.13 mm) and M. barbatus (average shell length of 20.85±6.80 mm) were collected in the Mali Ston Bay at a depth of 0.5 to 3m. After two years the length of A. noae ranged from a minimum of 6.0 mm to a maximum of 52.0mm, with an average length of 32.73±8.09 mm. For M. barbatus the length ranged from a minimum of 8.3mm to a final maximum of 50.3mm., with an average lenght of 3.19±6.14 mm. Key words: noah’s ark, Arca noae, bearded horse mussel, Modiolus barbatus, growth rate Pokusni uzgoj kunjke, Arca noae (Linnaeus, 1758) i bijele mušule, Modiolus barbatus (Linnaeus, 1758) u Malostonskom zaljevu Sažetak Istraživan je rast školjkaša, kunjke Arca noae (Linnaeus, 1758) i bijele mušule, Modiolus barbatus (Linnaeus, 1758) u uvjetima komercijalnog uzgajališta kamenice u Malostonskom zaljevu. Tijekom veljače 2007 sakupljeni su juvenilni primjerci ovih školjkaša (A. noae srednje dužine ljušture 21,70±7,13 mm i M. barbatus srednje dužine ljušture 20,85±6,80 mm), sa dubine od 0.5 do 3 m u Malostonskom zaljevu. Nakon dvogodišnjeg uzgoja dužina ljušture A. noae bila je u rasponu od 6.0 mm do 52.0 mm, sa srednjom vrijednosti od 32,73±8,09 mm, na kraju pokusnog razdoblja. Srednjak dužine ljušture M. barbatus bio je na kraju pokusa 33.19±6.14 mm s početnim minimumu od 8.3 mm i završnim maksimumom od 50.3 mm. Ključne riječi: kunjka, Arca noae, bijela mušula, Modiolus barbatus, rast Proceedings. 46th Croatian and 6th International Symposium on Agriculture. Opatija. Croatia (807-809) Section 6 . Fisheries, Game Management and Beekeeping 807 Valter KOŽUL, Nikša GLAVIĆ, Jakša BOLOTIN, Nenad ANTOLOVIĆ Introduction The bivalve noah’s ark, Arca noae (Linnaeus, 1758) and bearded horse mussel, Modiolus barbatus (Linnaeus, 1758) are commercially important edible shellfish species. A. noae is distributed in the eastern Atlantic Ocean, the Mediterranean Sea, the Black Sea, and the West Indies (Nordsieck, 1969). M. barbatus is widespread from the British Isles south to Mauritania, West Africa and are found in the Mediterranean (Poppe and Goto 2000). In the Adriatic Sea, both species are widely distributed and locally common (Hrs Brenko and Legac, 1996; Benović, 1997; Zavodnik, 1997). A. noae lives attached with solid byssus on all types of hard substrate, including rocks or shells, from low tide to depths of over 100 m and can grow up to 90 mm in lenght (Poppe and Goto, 2000). The horse mussel occurs in the lower eulittoral-sublittoral fringe and extend down to depths of 110 m, where they attach by strong byssus threads to rocky substrata. This paper describes preliminary consideration towards the controlled culture of A. noae and M. barbatus on commercial farms. Materials and methods Juvenile stages of A. noae and M. barbatus were collected in the Mali Ston Bay during February 2007. All specimens were collected at a depth of 0.5 to 3 m, over an of area 500 m2. For this investigation, 100 juveniles of A. noae and 100 juveniles of M. barbatus were collected together, along with the substrate on which they grew. Collected specimens were measured immediately after removal from the seabed. The specimens were not removed from the rocks. For the experimental cultivation specimens on rocks were placed in commercial oyster baskets at a depth of 8 m. The individuals were measured every two months throughout the experiment. These measurements included ventral and anterior-posterior shell length. Dead or damaged specimens were recorded during the measurements. Sea temperature was monitored daily and salinity was monitored monthly. Results and discusion The average length of A. noae specimens harvested from the seabed was 21.70±7.13mm (min. 6.0mm, max. 36.6mm), while the average length of M. barbatus was 20.85±6.80mm (min. 8.2, max. 33.1mm) (Fig. 1). Fig. 1. The average length measured during the experimental period The results of the two years research demonstrate a range from a minimum measured length of 6.0 mm for A. noae, to a maximum length of 52.0 mm. Average length at the end of the experimental period was 32.73±8.09 mm. Similar results were noted for M. barbatus, with an initial minimum of 8.3 mm, to a final maximum of 50.3 mm, with an average length at the end of experimental period of 33.19±6.14 mm (Fig. 1). Our study demonstrates a low 9.0% mortality rate for A. noae. The mortality rate for M. barbatus was higher at 34%. 808 46th Croatian and 6th International Symposium on Agriculture The experimental rearing of Noah’s Ark, Arca noae (Linnaeus, 1758) and Bearded Horse Mussel, Modiolus barbatus (Linnaeus, 1758) in Mali Ston Bay The average monthly growth of A. noae shell length was 1.29±1.34 mm month-1. The monthly growth for M. barbatus was higher at 1.89±1.1 mm month-1. The highest average growth was recorded between June and September of 2006 for both species, with a value of 3.48 mm month-1 for A. noae, and 4.47 mm month-1 for M. barbatus. The lowest values were recorded between November and February, when average increase in length was 0.27 mm month-1 for M. barbatus and 0.33 mm month-1 for A. noae. The average temperature over the experimental period was, 16.3˚C and the average salinity was 36.0psu. As noted in other research on this species, it was confirmed that these two shellfish species are a slow- growing, demonstrating growth of less than 20 mm over the experimental period of two years. The same results were also confirmed by Peharda et al. (2002), while studying the natural populations of A. noae in a few locations in the Adriatic sea. They noted a maximum size of 70 mm and an age of up to 16 years. Peharda et al. (2007) also noted slow growth of M. barbatus which attains a length of 40 and 50 mm within 5 and 8 years respectively. Due to the slow growth of these shellfish species and easy collecting, formation of broodstock at strategic locations will be important towards increasing the abundance of natural populations. Literature Benović, A., 1997. The history, present condition, and future of the molluscan fisheries of Croatia. In: MacKenzie CL Jr, Burrell VG Jr, Rosenfield A, Hobart WL (eds) The history, present condition, and future of the molluscan fisheries of north and Central America and Europe, vol 3, Europe. NOAA Technical Report NMFS 129. US Department of Commerce, pp 217-226. Hrs-Brenko, M., Legac, M.,1996. A review of bivalve species in the eastern Adriatic Sea: II. Pteromorphia (Arcidae and Noetidae). Natura Croatica, 5, 221-247. Nordsieck, F., 1969. Die europäischen Meeresmuscheln (Bivalvia). Stuttgart: Fischer Verlag, 256 pp. Peharda, M., Richardson, C.A., Onofri, V., Bratoš, A., Crnčević, M., 2002. Age and growth of the bivalve Arca noae L. in the Croatian Adraitic Sea. 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