Aquaculture International (2005) 13: 233–239 DOI 10.1007/s10499-004-1585-8
Ó Springer 2005
Growout of hatchery-reared juvenile spotted babylon (Babylonia areolate link 1807) to marketable size at four stocking densities in ﬂow-through and recirculating seawater systems N. CHAITANAWISUTI1,*, S. KRITSANAPUNTU2 and S. Y. NATSUKARI3 1
Aquatic Resources Research Institute, Chulalongkorn University, Phya Thai Road, Pathumwan, Bangkok 10330, Thailand; 2Department of Bioproduction, Faculty of Technology and Management, Prince of Songkla University, Suratani Province 84100, Thailand; 3Faculty of Fisheries, Nagasaki University, 1–14 Bunkyo-Machi, Nagasaki 852, Japan; *Author for correspondence (e-mail: firstname.lastname@example.org) Received 22 December 2003; accepted in revised form 21 July 2004
Key words: Spotted babylon, Babylonia Areolata, Growout, Stocking density, Flow-through water system, Recirculating water system Abstract. Hatchery reared juvenile spotted babylon, Babylonia areolata, were raised in canvas rearing tanks at four stocking densities (100, 200, 300 and 400 ind. mÀ2) in ﬂow-through and recirculating seawater systems until they reached the marketable sizes of 100–140 snails/kg. At all stocking densities, ﬁnal increments in mean length and weight of snails held in ﬂow-through systems were higher than those in recirculating systems, there was a signiﬁcant eﬀect (p < 0.05) of culture system on ﬁnal length and weight. Mean (±SE) survival of snails held at 100 ind. mÀ2 in the ﬂow-through system was 100.0 ± 0.1% but was not signiﬁcantly higher than survival in any other treatment (p > 0.05). Mean survival of snails held in the recirculating system was not signiﬁcantly lower than at any stocking density in the ﬂow-through system (p > 0.05).
Introduction The spotted babylon, Babylonia areolata, supports the second largest commercial gastropod ﬁshery in Thailand. In recent years there has been a rapid increase in market demand for this species in Thailand and other Asian countries. Because of this economic importance and the success with babylon culture, interest has developed in developing appropriate culture systems to increase per unit production (no.mÀ2), as well as decrease maintenance time and production costs during the growout phase of culture. Although large scale rearing of B. areolata is technically feasible, many problems must be solved to enable economically viable spotted babylon culture to develop. One problem that must be solved during growout in both intensive and extensive culture is stocking density, particularly with respect to growth. Eﬀects of stocking density on growth and survival are well documented for some marine bivalves and gastropods, e.g. oysters (Holiday et al. 1993), clams (Hadley and Manzi 1984), queen conch (Appeldoorn and Sanders 1984; Siddall 1984) and abalone
234 (Mgaya and Mercer 1995). The type of system used to culture spotted babylon inﬂuences growth, survival and cost of production (Chaitanawisuti and Kritsanapuntu 2000), but there was no information available on optimal stocking density for large scale production of juveniles of this species. In the present study the relationship between stocking density, growth and survival was determined for growout of hatchery reared juveniles of the spotted babylon in ﬂow-through and recirculating seawater systems. Materials and methods Design of experimental culture systems Four treatments of each culture system, each with two replicates were used as follows. Flow-through system Juveniles were reared in indoor rectangular canvas tanks that measured 1.5 · 0.5 · 0.7 m (L:W:H). Each tank was supplied with ﬂow-through ambient natural seawater at a rate of 50 l hÀ1 . Water depth was maintained at 0.5 m. The bottom of each tank was covered with a 5 cm layer of coarse sand (0.5– 1.0 mm mean grain size) that served as a substrate. When snails were removed from the rearing tanks for measurement, the substrate was cleaned by ﬂushing it with a jet of water and sun dried for 6 h every 30 days. Salinity and temperature ranged from 29 to 30 ppt and 29–32 °C respectively. Recirculating system Each canvas tanks measured 1.5 · 0.5 · 0.7 m (L:W:H) and had an independent recirculating system with supplemental aeration, airlift pump and biological ﬁlter. Biological ﬁlters were tanks of 0.5 · 5 · 0.7 m (L:W:H) that contained oyster shells held in nylon net bags. Water ﬂowed from the culture tank through the ﬁlters via airlift pumps at a ﬂow rate of 100 l hÀ1, before it was returned to the rearing tank. As in the ﬂow-through system, the tank bottom was covered with a 5 cm layer of coarse sand (0.5–1.0 mean grain size) to serve as a substrate. When snails were removed from the tank for measurement, the substrate was cleaned by ﬂushing it with a jet of water and sun dried for 6 h every 30 days. The tank was then reﬁlled with ambient seawater. Filter bags were rinsed in seawater to remove particulate matter, sun dried for 6 h and returned to the ﬁlter tank. Salinity was maintained at 29–30 ppt by addition of fresh water to correct for any increased salinity due to evaporation. Juvenile rearing Juvenile spotted babylons used in growth and survival experiments were produced in a hatchery (Chaitanawisuti and Kritsanapuntu 1997a). Individuals