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A sustainable integrated system for culture of fish, seaweed and abalone

A sustainable integrated system for culture of fish, seaweed and abalone
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  Ž . Aquaculture 186 2000 279– r locate r aqua-online A sustainable integrated system for culture of fish,seaweed and abalone Amir Neori ) , Muki Shpigel, David Ben-Ezra  Israel Oceanographic and Limnological Research, National Center for Mariculture, P.O. Box 1212, Elat,88112, Israel Accepted 2 December 1999 Abstract A 3.3 m 2 experimental system for the intensive land-based culture of abalone, seaweed andfish was established using an integrated design. The goals were to achieve nutrient recycling,reduced water use, reduced nutrient discharge and high yields. Effluents from Japanese abalone Ž . Ž .  Haliotis discus hannai  culture tanks drained into a pellet-fed fish  Sparus aurata  culture tank. Ž . The fish effluent drained into macroalgal  Ul Õ a lactuca  or  Gracilaria conferta  culture, andbiofilter tanks. Algal production fed the abalone. The system was monitored to assess productivityand nitrogen partitioning over a year. The fish grew at 0.67% day y 1 , yielding 28-kg m y 2 year y 1 . Ž  y 2  y 1 . The nutrients excreted by the fish supported high yields of   U. lactuca  78-kg m year and Ž . efficient 80% ammonia filtration.  Gracilaria  functioned poorly.  Ul Õ a  supported an abalonegrowth rate of 0.9% day y 1 and a length increase of 40–66  m m day y 1 in juveniles, and 0.34%day y 1 and 59  m m day y 1 in young adults. Total abalone yield was 9.4 kg year y 1 . A surplus of seaweed was created in the system. Ammonia-N, as a fraction of total feed-N was reduced from45% in the fish effluents to 10% in the post-seaweed discharge. Based on the results, a doublingof the abalone:fish yield ratio from 0.3 to 0.6 is feasible. q 2000 Elsevier Science B.V. All rightsreserved. Keywords:  Integrated; Land-based; Sustainable; Mariculture; Abalone; Fish; Seaweed; Nutrient-budget Ž .  E-mail address: A. Neori . ) Corresponding author. Tel.:  q 9-727-636-1400,  q 9-727-636-1441,  q 9-727-636-1445; fax:  q 9-727-6375761.0044-8486 r 00 r $ - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0044-8486 99 00378-6  ( ) A. Neori et al. r  Aquaculture 186 2000 279–291 280 1. Introduction The discharge of low-quality water from intensive land-based mariculture facilitiescauses environmental and economic concerns, since fish excrete to the water 70–80% of  Ž . their ingested protein N, 80% of it in dissolved forms Porter et al., 1987 . Thedevelopment of practical and non-polluting land-based maricultural practices is thereforeof great importance, both for mariculture and for the coastal environment.A useful approach of integrated mariculture has been designed at the National Center Ž . for Mariculture NCM , Eilat, for solving the effluent problem by nutrient recycling.Water from fishponds recirculates through biofilters of seaweed, which remove most of  Ž . the ammonia from the water Cohen and Neori, 1991; Neori et al., 1993, 1996 . Thefinancial return from the low-value seaweed biomass by-product can be raised greatly byfeeding it to valuable macroalgivores, such as sea urchins and abalone. Ž . Abalone is a commercially valuable marine gastropod Oakes and Ponte, 1996 . Its Ž culture worldwide is severely limited by supplies of suitable seaweed Uki and Watan- . abe, 1992 . This situation makes it only natural to add abalone to the integrated culture Ž . system for fish and seaweed Shpigel and Neori, 1996 . The integrated culture of two Ž organisms, abalone and seaweed, has been tested on a laboratory scale Neori et al., . 1998 .In this study, we describe the performance of a more complex system, for integratedculture of three organisms — abalone, fish and seaweed. The system is intended to befully integrated, that is, the fluxes of water and nutrients between the three modules areadjusted to optimize water use, nutrient recycling and marketable production. Thesystem is also intended to be sustainable, one that allows increased supply of marketablemarine organisms with minimal increases in pollution and in burden on naturalpopulations. 2. Materials and methods Ž The experimental system was a modification of our model design design B in . Shpigel and Neori, 1996 , with a water saving modification, by which the abaloneculture water were recycled for the fish culture. It consisted of one unit each for abalone, Ž  y 1 . finfish, and seaweed. Unfiltered seawater 2400 l day was pumped to two abalonetanks, drained through a fish tank, and finally through a seaweed filtration r production Ž . Ž unit back to the sea Fig. 1, gray rectangles . The fish were fed with fish feed Matmor, . Israel . Ammonia and other nutrients excreted by the fish were removed by the seaweedand supported their growth. The seaweed was harvested and fed to the abalone. Theintegrated culture was operated for a year, beginning in October 1995. 2.1. Abalone unit   ( ) A. Neori et al. r  Aquaculture 186 2000 279–291  281 Ž . Fig. 1. A schematic diagram of the integrated mariculture system gray rectangles . The processes defining the Ž  y 1 . nitrogen budget are illustrated. Rounded values grams N year quantify each process; solid vertical arrowsare seawater flows; heavy dashed arrows are N inputs and outputs; the fine dashed line is seaweed recycling tothe abalone. The abalone unit consisted of two 120-l rectangular bottom drained tanks. The tanks Ž were elevated, allowing effluents to drain into the fish tank. A removable screen 1-cm . mesh covered the whole area 10 cm above the flat bottom, and retained the abalonewhile allowing feces and detritus to drain. The tanks were completely flushed andcleaned once a week. Two parallel air diffusers suspended the algae, which were addedas feed. Two 160-mm diameter half pipes were stacked on the netting to provide surfacearea and shelter for abalone attachment.Two size groups of Japanese abalone,  Haliotis discus hannai,  were stocked in Ž . Ž . separate tanks, 1200 juveniles of 11 " 2.3 mm mean " sd length 0.23 " 0.04 g in Ž . Ž . one tank Group I and 251 adults of 44.2 " 2 mm length 15.7 " 4.6 g in a second tank  Ž . Group II . The juveniles were kept in the system 374 days. Six hundred juveniles wereculled out after 184 days. The adults were kept in the system at stocking densities of 20–30 kg m y 3 . After 184 days they were harvested, measured for the parametersdescribed below, and then replaced by 600 smaller individuals of 16.6 " 3.1 mm length Ž . Ž . 0.7 " 0.1 g for an additional 224 days Group III .One hundred animals in each adult group were individually tagged. Once a month thetagged animals were washed free of debris, drained to remove surplus water and driedon absorbent paper. Wet weight measurements were used to calculate specific growth Ž . Ž rates SGR% for each time interval, i.e., the percent body weight gain per day Shpigel . et al., 1996, based on Day and Fleming, 1992 w x SGR% s  ln W  y ln W   r t   = 100 1 Ž . Ž . t   0  ( ) A. Neori et al. r  Aquaculture 186 2000 279–291 282 where  W   is the wet weight of an animal at the beginning of each monitoring interval 0 and  W   is the weight after  t   days of growth, at the end of the interval. Shell length t  measurements were used to calculate shell growthShellgrowth  m m r day y 1 s  L  y  L  r t   2 Ž . Ž . Ž .  2 1 where  t   is time interval in days,  L  is the length of an animal at the beginning of each 1 monitoring interval and  L  is the length at the end of the interval. Food conversion ratio 2 Ž . FCR was calculated from feed intake and growthFCR s feedintake gfw  r weightgain gfw 3 Ž . Ž . Ž . Additionally, the cumulative yields of the three abalone groups and the suppliedseaweed were used to calculate overall production FCR. 2.2. Fish unit  Ž . Three hundred gilthead sea bream  Sparus aurata  with an average weight of 40 g Ž . Ž  2 . 12 kg total weight were stocked in a 600-l 1 m surface area rectangular aeratedtank. The fish were fed a 45% protein pellet diet. The bottom of the tank was draineddaily to remove feces and uneaten food. Stocking density was maintained below 15 kgm y 3 . Excess fish were culled regularly. Once a month a sample of 50 fish was weighed.Specific growth rates and FCR were calculated as mentioned above. 2.3. Seaweed unit  Two species of seaweed,  Ul Õ a lactuca  and  Gracilaria conferta,  were grown in two Ž  2 . Ž . 600-l 1 m surface area tanks as described in Vandermeulen 1989 . The algae weresuspended in the water column by air diffusers situated at the bottom. Total seaweedbiomass was kept approximately at 1.5 kg of   U. lactuca  and 5–13 kg of   G. conferta. Twice a week, excess seaweed biomass was harvested. The seaweed was drained of surplus water and weighed. The biomass was fed to the abalone as needed and the restdiscarded. Several crashes of the  G. conferta  stock occurred, necessitating biomassimports. 2.4. Abiotic parameters and nitrogen budgets Ž . Abiotic parameters oxygen, temperature, pH and ammonia levels were monitored Ž . twice a day at 0800 and 1400 h in all components of the system. Ammonia levels were Ž . monitored by an electrode Ingold NH Electrode Type 15-230-3000 . In addition, 24-h 3 intensive measurements were carried out several times a year. During the intensive Ž . measurement periods, ammonia-N was measured by an autoanalizer Technicon AA-II Ž . as in Neori et al. 1996 . Nitrogen content of the abalone and the seaweed tissue were Ž . measured by a CHN analyzer Perkin Elmer .Nitrogen levels of the abalone mucus, and fish and abalone feces were measured inpreliminary experiments and were estimated for this experiment according to the actualsizes of the abalone.  ( ) A. Neori et al. r  Aquaculture 186 2000 279–291  283 3. Results 3.1. Abalone unit  Average water temperature in the abalone tanks ranged from 20 8 C in winter to 28 8 Cin summer. Levels of pH, oxygen and salinity were stable throughout the year andranged between 7.4–7.6, 7.8–8.8 mg l -1 and 40–41 ppt, respectively.Growth rate by weight slowed as the animals grew larger, but growth rate by length Ž was lower in juveniles of the larger size than in small juveniles and in adults Table 1; . Ž . Fig. 2 . From October 1995 to December 1996 the juvenile abalone Group I more then Ž . tripled their length and multiplied their weight by nearly 30 fold Table 1 . Theyincreased their weight on averaged by nearly 1% day y 1 and their length by 66.5  m m y 1 Ž . day . Their FCR was above 5 and the survival 75%. The adult abalone Group II Ž . increased 25% in length and doubled their weight in half a year Table 1 . Daily growthaveraged only 0.34% by weight, but nearly equalled the juveniles’ length increase at 59 m m day y 1 . FCR of the adults was nearly triple that of the juveniles, 14.2, but survival Ž . was better, at 95%. The juveniles in the second period Group III gained in weightnearly 8 fold and doubled their length in 224 days. Their daily growth averaged aboutthe same as that of the juveniles from Group I, at nearly 1%, while their length increased y 1 Ž . on average by only 40  m m day Table 1 . Their FCR was intermediate between those Ž .  y 1 of the other two groups Table 1 . The total abalone yield was 9.4 kg year , with 40% Ž . meat and meat dw protein content of 75 " 1% mean " sd,  n s 4 . 3.2. Fish unit  Average water temperature in the fish tank ranged from 19.1 8 C in winter to 27.9 8 C insummer. Salinity levels were constant throughout the year at 41 ppt. The pH levelsranged between 7.1–8.0. Oxygen levels were relatively low and ranged between 2.5–6.3 y 1 Ž  y 3 . mg l . Annual fish production was 28 kg 35 kg m . The fish grew in a year from 40 Ž . g to commercial weight of 470 g, but growth was slow in the summer months Fig. 3 . y 1 Ž Average growth was 0.67% day , FCR averaged 2 and the survival was 95% Table . 1 . 3.3. Seaweed unit  Water temperature in the seaweed tanks ranged from 18.1 8 C in winter to averagetemperature of 31.2 8 C in summer. Salinity was stable and at 41 ppt throughout the year. Ž . Ž  y 1 . The daily levels of pH 8.5–8.9 and dissolved oxygen 8.9–9.07 mg l were high, astypical for intensive photosynthetic culture.  U. lactuca  grew at a stable rate throughout Ž . the year, yielding on average 233 g fresh weight a day and 78 kg annually Fig. 4 . dw Ž . protein in this seaweed averaged 28 " 4%  n s 4 . Only 46% of the yield wastransferred to the abalone, the rest was harvested.Annual production of   G. conferta  was poor, only 14 kg, of which half was in useless Ž . fragments Fig. 4 , because of frequent culture crashes. dw protein content of this Ž . seaweed averaged 33 " 3%  n s 4 . The useful yield was given to the abalone, with theadditional import of over 5 kg from another system.
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