Pilot Production of Hatchery-Reared Summer Flounder Paralichthys Dentatus in a Marine Recirculating Aquaculture System: the Effe
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JOURNAL OF THE Volume 36, No. 1 WORLD AQUACULTURE SOCIETY March 2005 Pilot Production of Hatchery-RearedSummer Flounder Purulichthys dentutus in a Marine Recirculating Aquaculture System: The Effects of Ration Level on Growth, Feed Conversion, and Survival PATRICKM. CARROLLAND WADE0. WATANABE University of North Carolina at Wilmington, Centerfor Marine Science, 7205 WrightsvilleAvenue, Wilmington, North Carolina 28403 USA THOMASM. LOSORDO Department of Zoology, North Carolina State University, Raleigh, North Carolina 27695 USA Abstract-Pilot-scale trials were conducted to suggests increased competition for a restricted ration evaluate growout performance of hatchery-reared led to a slower growth with more growth variation. The summer flounder fingerlings in a state-of-the-art decrease in growth in phases 2 and 3 was probably related recirculating aquaculture system (RAS). The outdoor to a high percentage of slower growing male fish in the RAS consisted of four 4.57-m dia x 0.69-111 deep (vol. population and the onset of sexual maturity. = 11.3 m’) covered, insulated tanks and associated water This study demonstrated that under commercial treatment components. Fingerlings (85.1 g mean initial scale conditions, summer flounder can be successfully weight) supplied by a commercial hatchery were stocked grown to a marketable size in a recirculating aquaculture into two tanks at a density of 1,014 fishhank (7.63 kg/mg). system. Based on these results, it is recommended that a Fish were fed an extruded dry floating diet consisting farmer feed at a satiation rate to minimize growout time. of 50% protein and 12% lipid. The temperature was More research is needed to maintain high growth rates maintained between 20 C and 23 C and the salinity was through marketable sizes through all-female production 34 ppt. Under these conditions, growth, growth variation and/or inhibition of sexual maturity. (CVw,),feed utilization, and survival of fish fed to 100% and 82% of a satiation rate were compared. Due to clear changes in growth patterns during the The summer flounder Paralichthys dentatus is study, data was analyzed in three phases. During phase a left-eyed flatfish in the family Paralichthyidae. 1 (d 14196), fish showed rapid growth, reaching a It inhabits the coastal waters from Nova Scotia to mean weight of 288 g f 105 and 316 g f 102, with southern Florida, but is most abundant from Cape a CVw, of 0.36 and 0.32 and FCR’s of 1.38 and 1.36 Cod to Cape Hatteras (Grimes et al. 1989). High in the subsatiation and satiation groups, respectively. market value and growing demand have stimu- During phase 2 (d 1964 454), fish displayed slower lated interest in summer flounder as a potential growth reaching mean weights of 392 g f 144 and 436 aquaculture species. Successful culture of the g * 121, with a CVw,of 0.37 and 0.28, and increasing Japanese flounder Paralichthys olivaceus in Asia FCR’s of 3.45 and 3.12 in the subsatiation and satiation and the turbot Scophthalmus maximus in Europe groups, respectively. During phase 3 (d 4544614), fish has provided a positive model for the development showed little growth reaching mean weights of 399 g i 153 and 440 g f 129, with a CVw,of 0.38 and 0.29 in of research and the commercialization of the sum- the subsatiation and satiation groups, respectively. Over mer flounder in the U.S. Since 1990,developments the entire growout period (d 14614), feed conversion have been made in the spawning and rearing of ratios were 2.39 and 2.37 and survival was 75% and 81 % juvenile summer flounder, but to date there is little in the subsatiation and satiation treatments, respectively. information on growout to a marketable size. The maximum biomass density reached during the study It has been shown in some flatfish species that was 32.3 kg/m3. feeding to satiation does not necessarily produce The satiation feed rate was superior to the 82% the best conversion efficiency, since feed may satiation rate, since it maximized growth rates, with no be only partially digested feed, ending as waste effect on FCR. The higher CVw,in the subsatiation group 6 Copyright by the World Aquaculture Society 2005 120 PILOT PRODUCTION OF HATCHERY-REARED SUMMER FLOUNDER 121 (Puvanendran et al. 2003). As feed cost is among the highest operational costs in commercial aqua- culture operations, it is essential to minimize feed conversion ratios, while maintaining an acceptable growth rate. The objectives of this study were to evaluate growth rates of hatchery-reared summer flounder fingerlings to full marketable sizes in a commercial scale recirculating aquaculture system and compare growth, feed conversion ratio, and survival of fish fed at a satiation and a subsatia- tion feed rate. Materials and Methods Experimental Animals This study was conducted at the University of North Carolina at Wilmington Center for Marine Science (UNCW-CMS) Aquaculture Facility in Wrightsville Beach, North Carolina, USA, from September 2000 to May 2002. Hatchery-reared, juvenile summer flounder (mean weight = 30 g) FIGUREI. Scale blueprint of the summerjloundergrowout were obtained from a commercial hatchery (Great system. Bay Aquaculture, Portsmouth, New Hampshire, USA). Fish were live-hauled by truck to UNCW- CMS in July 2000 and were maintained in an ted with an 11-L swirl separator. The double drain 11.3-m3 tank supplied with recirculating seawater featured a flatfish ring to keep fish out of the drain. until the beginning of the study. Filtered seawater The double drain divided the effluent flow into two (from a natural source) supplied the recirculating streams. One stream discharged water containing system with makeup water. During this period, settleable solids (approximately 5% of the flow fish were fed ad libitum an extruded dry floating rate) to the swirl separator. The larger stream (ap- flounder diet consisting of 50% protein and 12% proximately 95% of the flow rate) from the double lipid (Melick Aquafeed, Catawissa, Pennsylvania, drain reunited with the clarified water from the USA). swirl separator in a standpipe well. The effluent Experimental System stream was then treated with a rotating drum screen filter with a 60-pm screen (PRA Manufacturing, Growout studies of summer flounder fingerlings British Columbia, Canada) to remove fine solids. were conducted in an outdoor state-of-the-art recir- The filtered water was then distributed over a bio- culating aquaculture system (RAS) (Fig. 1) based logical filter by a drip plate. The biological filter on the North Carolina State University Fish Barn media consisted of 0.53 m3 of 3-mm polystyrene design (Losordoet al. 2000). The commercial scale microbeads with a specific surface area of 1,145 RAS consisted of two groups of two 1 1.3-m3 cir- mz/m3.Water was then pumped out of the biologi- cular fiberglass tanks (4.57 m dia x 0.69 m deep). cal filter by a 3.36-kW centrifugal pump (Jacuzzi Each group was supported by an independent Piranha, Little Rock, Arkansas, USA) and passed recirculating system. Tanks were insulated and through a 3-kW heat pump (Aqualogic, San Di- covered by a translucent conical fiberglass cover ego, California, USA). A small portion of the flow with a retracting door, and the interiors were black was diverted to a foam fractionator (Top Fathom, in color to maintain a low illumination level. Eugene, Oregon, USA) that discharged back into Each tank contained a center double drain the biological filter. Water from the heat pump was (Aqua-Optima, Trondheim, Norway) that was fit- treated by a 260-W ultraviolet (W)sterilizer (Em- 122 CARROLL ET AL. peror Aquatics, Pottstown, Pennsylvania, USA). lowered repeatedly until 100 fish were sampled. From the UV sterilizer, the water passed through From d 406 onward, the 30 tagged fish along with an oxygen cone before entering the culture tanks. 30 random fish were sampled every 2 mo until the Flow to each tank was maintained at 150 L/min. end of the study on d 614. Fish were weighed and Carbon dioxide stripping was accomplished by measured with the aid of an anesthetic, 75-mg/L air diffusers placed at the bottom of the biological methane trisulfonate (MS-222). Total length was filter and a degassing column between the water recorded to the nearest millimeter and weight distribution drip plate and the biological filter to the nearest gram using an electronic balance media. (Acculab, Bradford, Massachusetts, USA). Fish were allowed to recover in seawater before being Experimental Design returned to the tank. To compare the effects of ration level on growth and feed utilization, fingerlings (mean wt. = 85.1 Water Quality g, range = 23-139 g) were stocked in two 11.3-m3 Dissolved oxygen was monitored continuously tanks at a density of 7.63 kg/m3(1,014 fishhank, 62 in each tank by a PT 4 oxygen monitor (Point fish/m2). Mean coefficient of variation of weight Four, British Columbia, Canada). Salinity, pH, was 0.29. Fish in one tank were fed at a rate of and temperature were monitored daily by a YSI 100% satiation, i.e., until fish stopped feeding, 5200 Recirculating Monitoring System (Yellow while fish in the other tank were fed at 80% of the Springs Instruments Co., Inc., Yellow Springs, satiation level. Total daily feed ration in the 100% OH). Ammonia-nitrogen, nitrite-nitrogen, and satiation group was expressed as a percentage of nitrate-nitrogen levels were checked weekly using total tank biomass determined at the last sampling. a spectrophotometer (Hach Company, Loveland, Total daily feed ration in the subsatiation treatment CO). was determined by multiplying the satiation feed Analytical Methods rate by 0.80 and the total biomass determined at the last sampling.