Muki Shpigel

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

A 3.3 m 2 experimental system for the intensive land-based culture of abalone, seaweed and fish 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 . . Haliotis discus hannai culture tanks drained into a pellet-fed fish Sparus aurata culture tank. . The fish effluent drained into macroalgal Ul˝a lactuca or Gracilaria conferta culture, and biofilter tanks. Algal production fed the abalone. The system was monitored to assess productivity and nitrogen partitioning over a year. The fish grew at 0.67% day y1 , yielding 28-kg m y2 year y1 . y2 y1 . The nutrients excreted by the fish supported high yields of U. lactuca 78-kg m year and . efficient 80% ammonia filtration. Gracilaria functioned poorly. Ul˝a supported an abalone growth rate of 0.9% day y1 and a length increase of 40-66 mm day y1 in juveniles, and 0.34% day y1 and 59 mm day y1 in young adults. Total abalone yield was 9.4 kg year y1 . A surplus of seaweed was created in the system. Ammonia-N, as a fraction of total feed-N was reduced from 45% in the fish effluents to 10% in the post-seaweed discharge. Based on the results, a doubling of the abalone:fish yield ratio from 0.3 to 0.6 is feasible. q 2000 Elsevier Science B.V. All rights reserved.

The integrated culture of seaweed, abalone, fish and clams in modular intensive land-based systems : II. Performance and nitrogen partitioning within an abalone (Haliotis tuberculata) and macroalgae culture system

A pilot-scale system for the intensive land-based culture of abalone was established using an integrated design aimed at eliminating the dependence on external food sources, whilst reducing water requirements and nutrient discharge levels. The system was the first and simplest trial in a series of progressive complexity of the concept of integrated culture of seaweed, abalone, fish and clams in modular and intensive land-based facilities. Relative sizes of the modules, their stocking densities and the rate of nutrient supply were determined based on earlier results to be optimal. Effluents from two abalone (Haliotis tuberculata) culture tanks drained into macroalgae (Ulva lactuca or Gracilaria conferta) culture and biofilter tanks, where nitrogenous waste products contributed to the nutrition of the algae; net algal production from each algal tank was harvested and used to provide a mixed diet for the abalone. Excess algal yield was used elsewhere. The system was monitored to assess productivity and nitrogen partitioning over a year, while improvements were made based on the accumulating results. Total annual N-budgets were combined with mean production figures to determine a suitable ratio of abalone biomass to algal culture vessel productivity, towards commercial application of the concept. The abalone grew on average 0.26% and 0.25% body weight/d in the two culture tanks; reduced growth and increased food conversion ratios (food eaten/biomass gain; w/w) were associated with high summer water temperatures (max. 26.9°C). U. lactuca showed reliable growth and filtration performance (mean production of 230 g fresh weight/m2/d, removing on average 58% of nitrogen supplied). Conversely, G. conferta growth was highly erratic and was deemed unsuitable for the current application. It is estimated that 1 kg of abalone biomass would require food supplied by 0.3 m2 of U. lactuca culture, reducing N inputs required by 20% and N in effluent by 34% when compared to the two organisms grown in monoculture.

A proposed model for “environmentally clean” land-based culture of fish, bivalves and seaweeds

Abstract A model system is proposed, in which particulate and dissolved metabolites from the effluents of fish culture are removed by biofilters of bivalves (Crassostrea gigas and/or Tapes semidecussatus) and seaweeds (Ulva lactuca). The design utilizes ecological principles and the results of long-term pilot-scale trials with each of the four components of the system. Fresh sea water enters the fishponds, drains through an earthen sedimentation pond, a bivalve filtration unit and a seaweed filtration/production unit, and is finally discharged back into the sea. An additional loop recirculates water from the sedimentation pond through a bivalve production unit. The performance of each of the different components of the system is assessed in terms of total nitrogen budgets, which yield the following results: fish yield, 26% of the N introduced in the feed; bivalve yield, 14.5%; seaweed yield, 22.4%; settled feces, 32.8%; suspended and dissolved discharge back into the sea, only 4.25%. The harvested yields contain 63% of the N budget. The production of 1 kg of fish, requiring 3 kg of feed, is accompanied by the production of 3 kg of bivalves and 7.8 kg of seaweed. Each 100 m2 of fishponds requires 50 m2 of sedimentation ponds, 33 m3 of bivalve troughs and 42 m2 of seaweed ponds.

A semi-recirculating, integrated system for the culture of fish and seaweed

Abstract Biofiltration allows for environmentally sustainable mariculture. An intensive, biofiltered recirculating integrated system producing fish and seaweed on a semi-commercial scale was evaluated with respect to production and to nutrient and heat budgets. The system consisted of abalone (Haliotis discus hannai) and sea urchin (Paracentrotus lividus) tanks, an intensive fishpond (Sparus aurata), and a three-stage Ulva lactuca biofilter, which cleaned and recirculated 50% of the effluent back to the fishpond. To preserve water heat, the shellfish and fishpond units were both covered with greenhouses; the biofilter unit was covered with a greenhouse only during winter. Seaweed yield was variable and averaged 94 and 117 g m−2 day−1 (fresh weight) in periods with and without greenhouse cover, respectively. Protein content of U. lactuca averaged above 34% of dry weight. The biofiltration of only 50% of the water through the seaweed biofilter reduced the export of dissolved nutrients to the environment by nearly 30%. Peak ammonia excretion by the morning-fed fish coincided with maximum seaweed light-dependent ammonia uptake and concentrations of ammonia in the fishpond remained within nontoxic limits. Also, daytime photosynthesis of U. lactuca (uptake of CO2) met fish respiration (production of CO2), thus balancing fishpond pH levels within safe limits regarding ammonia toxicity. Daytime oxygen demand by the fish was partially met by the photosynthetically generated oxygen. Before covering the biofilter with a greenhouse, it lost much heat, reducing the temperature in the fishpond. Following the greenhouse covering of the biofilter, heat loss ceased and consequently the fishpond temperature was raised. Recirculation through the biofilter improved system sustainability; it reduced water use, lowered negative environmental impact, and maintained stable and safe water quality conditions in the fishpond.

A novel three-stage seaweed (Ulva lactuca) biofilter design for integrated mariculture

Seaweed biofilters have proven their usefulness in the treatment of fishpond effluents. However, their performance poses a dilemma: TAN (Total Ammonia N) uptake rate – and with it seaweed yield and protein content – is inversely proportional to TAN uptake efficiency. The ideal for a seaweed biofilter performance would be a high uptake rate together with high uptake efficiency. The novel three-stage seaweed biofilter design described here has solved this dilemma. The design used the finding that the performance of seaweed ponds depended on the flux of TAN through them, and that therefore effluents with reduced TAN concentration could provide the seaweed with a high TAN flux if the water flow increased proportionally. Effluents from a seabream fishpond were passed through a series of three successively smaller (25, 12.5 and 6.25 m2, respectively) air-agitated Ulva lactuca ponds. The diminished inflow TAN concentrations to the second and third ponds of the biofilter system were compensated for by the increased water exchange rates, inversely proportional to their sizes. The biofilter performance was evaluated under several TAN loads. TAN was efficiently removed (85–90%), at a high areal rate (up to 2.9 g N m-2 d-1) while producing high protein U. lactuca (up to 44% dw) in all three stages, although with mediocre yields (up to 189 g fresh m-2 d-1). Performance of each seaweed biofilter pond correlated not with TAN concentration, but with areal TAN loads. The novel three-stage design provides significant functional and economic improvements in seaweed biofiltration of intensive fishpond water.

The effect of photoperiod and temperature on the reproduction of European sea urchin Paracentrotus lividus

Abstract The effects of water temperature and light regimes on gonadal development in the sea urchin Paracentrotus lividus were evaluated in two 12-week periods, one in spring–summer and one in winter–spring. Four different combinations of photoperiod and temperature regimes (18–26 °C) were tested in each. Sea urchins were fed a prepared diet. Food intake, growth, gonadosomatic index, biochemical composition and gametogenetic stages were measured. Results show that water temperatures between 18 and 22 °C enhance growth and gonadal development. Long days (illumination) reduce the rates of gametogenesis while short days increase reproductive development.

The integrated culture of seaweed, abalone, fish and clams in modular intensive land-based systems: I. Proportions of size and projected revenues

Three environmentally friendly modular designs for integrated mariculture are described. The basic design consists of modules for the culture of seaweed (Ulva lactuca or Gracilaria spp.) and abalone (Haliotis tuberculata). Modules for the culture of fish (Sparus aurata) and then clams (Tapes philippinarum) are subsequently connected in two progressively complex systems. The modular design allows flexibility in the allocation of resource shares to each product according to operational and economic constraints. Reduction in nutrient release to the environment results from increasing the fraction of supplied ammonia or protein-N that ends up as commercial products relative to current monoculture practices. As much as half or more of the nitrogen supplied to the proposed systems is expected to be utilized by harvestable yields of seaweed, molluscs and fish. System dimensions and projections of yields and revenues allow readers to roughly estimate profitability for the three designs under their own conditions.

The Pacific oyster, Crassostrea gigas, as a biological filter for a marine fish aquaculture pond

Abstract An oyster aquaculture system, designed to take advantage of excess phytoplankton production, was integrated with an intensive fish aquaculture system on a pilot scale. In addition to providing a commerical product from otherwise unutilized biomass, the oyster culture system functioned as a biological filter to remove excessive and dangerous levels of phytoplankton from the fish pond water. Oyster growth was rapid at ambient temperatures greater than or equal to 27°C, producing a commercial product within 14 to 18 months; phytoplankton levels were sufficiently reduced to allow a 50% reduction in fresh sea water input to the fish ponds. The reduction of nutrient levels in the runoff water is ecologically advantageous in a system proximal to delicate coral reefs.

A biomechanical filter for treating fish-pond effluents

Abstract Cultured bivalves, Crassostrea gigas and Tapes philippinarum efficiently removed particulate matter from fish-pond effluents under two hydrological regimes. Two reactor types, a Plug Flow Reactor and a Continuous Stirred Flow Reactor were tested. Under the experimental conditions, the Plug Flow Reactor was found to be more efficient in deputing aquaculture effluents. A mixture of juvenile bivalves of both species further increased treatment efficiency. Flow rate and reactor length influence vertical settling of the non-planktonic particles. A mathematical model is proposed to predict particle removal by the bivalves under the conditions of the two rector types.

Propagation of the Manila clam (Tapes semidecussatus) in the effluent of fish aquaculture ponds in Eilat, Israel

Abstract The Manila clam, Tapes semidecussatus Reeve (Bivalvia, Veneridae), was reared in the effluent of marine fish aquaculture ponds in Israel. Despite relatively high water temperatures during the summer (27–31°C) and extremely high salinity throughout the year (41±1 ppt), the clams grew from 1.90±0.38 g to 18.35±4.45 g in 13 months, with mortality rates of only 10–12%. In addition, gametogenesis occurred during much of the year. Although reared in conditions much different than those where it is found naturally, T. semidecussatus acclimated to local conditions and appears to have excellent potential for intensive mariculture in Israel.