WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2017 11 Every year, the WAS Board of Directors sponsors a monetary award ($100) to the authors of the best article published in World Aquaculture magazine as a way to encourage high-quality submissions. The WAS Honors and Awards Committee has selected the article by Lorenzo M. Juarez, Pablo A. Konietzko and Michael H. Schwarz on “Totoaba Aquaculture and Conservation: Hope for an Endangered Fish from Mexico’s Sea of Cortez.” As a consequence of this article, additional attention is being directed to conservation of the endangered totoaba. Congratulations to Lorenzo and his co-authors! Best Article in World Aquaculture in 2016 This issue’s selected research publication from the Journal of the World Aquaculture Society is “Phosphorus Budget in Integrated Multitrophic Aquaculture Systems with Nile Tilapia, Oreochromis niloticus, and Amazon River Prawn, Macrobrachium amazonicum.” Authors are Fernanda S. David, Danilo C. Proença and Wagner C. Valenti and the paper is found in volume 48(3):402414. Over the last decade there has been a burgeoning interest in integrated multitrophic aquaculture systems (IMTA). Most aquaculture systems can be classified as monospecific. Ecological principals are demonstrated by the characteristics of efficiency and stability found in community food webs composed of an array of species representing different trophic levels. IMTA systems are a step toward the application of the food web concept in aquaculture production. In such systems, directly fed species are cultured in association with extractive species that benefit from the availability of nutrients from uneaten feed and feces produced. Nutrients from these sources are thus incorporated into extractive species. Therefore, a principal outcome of IMTA systems is enhancement of nutrient utilization efficiency, resulting in less phosphorus released in discharged effluent. IMTAs can therefore contribute to environmental sustainability of aquaculture production. Furthermore, additional income can be realized by farming two species. In this investigation, the authors evaluated the source and fate of phosphorus with earthen ponds where IMTA management was practiced. The fed species was Nile tilapia Oreochromis niloticus and the extractive species was Amazon River prawn Macrobrachium amazonicum. There were three treatments, each with four replicates. Two treatments consisted of ponds having one of two different substrates and one treatment consisted of ponds without any substrate. Substrates were positioned in ponds and became colonized by periphyton that was presumably consumed by prawns as an additional source of nutrition. Periphyton also served as a nutrient sink for phosphorus. At the inception of the experiment, amounts of phosphorus in several compartments were measured. Between 73 and 95 percent of phosphorus was introduced to ponds from three principal sources: tilapia feed, inlet water and fertilizer. Feed for the fed species was the principal source of phosphorus in all treatments, Recent Research Highlight from the Journal of the World Aquaculture Society ranging between 50-60 percent. Inlet water was the second highest input source of phosphorus (17-27 percent). The phosphorus content of rainwater introduced to ponds during the study was calculated and included. Input quantities were not statistically different among treatments. The fate of phosphorus that entered ponds was principally accumulation in pond sediment, increased fish and prawn biomass and outlet water. The percentage of phosphorus found in the tilapia and prawns of the IMTA system (20-28 percent) exceeded the percentages previously determined in the biomass of either species in monoculture (10-20 percent). Higher stocking densities of the prawns would likely increase the comparatively small amount of phosphorus that was retained in prawn biomass (1-2 percent), relative to fish biomass. The expectation of significantly greater recovery of phosphorus in fish and prawn biomass from the presumed consumption of periphyton growing on substrate was not realized. However, the two treatments with substrates retained twice as much phosphorus added to ponds over the grow-out period, thereby significantly reducing the quantity of phosphorus lost to outlet water. Between 60 and 68 percent of the total phosphorus accumulated in the sediment of ponds in all treatments. Additionally, no significant difference for each of the phosphorus outputs was observed among treatments, except for phosphorus in effluent from ponds without substrate, which was significantly higher. The lack of significantly different, treatment-dependent values for other output compartments may be the result of high variation among values. No significant differences in productivity were observed among the three treatments. The combined productivity realized after 140 days of culture in the IMTA system was 5,350 kg/ha, consisting of approximately 91 percent fed tilapia and 9 percent extractive prawns. Despite wide variation in phosphorus values for different compartments, this investigation substantiates the obvious value of IMTA systems. These systems effectively increase nutrient recovery in the harvested biomass of two species, primarily introduced through feed. IMTA systems are an example of a management practice that will positively contribute to the realization of environmentally sustainable aquaculture, particularly in earthen ponds, which currently represent the predominant system used for (CONTINUED ON PAGE 12)
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