22 DECEMBER 2014 • WORLD AQUACULTURE • WWW.WAS.ORG Assuming that the average monthly feeding rate is the same in each month of a year, then the mass loading of TAN released each month is 10,275 g. At the lowest flow rate of the river (11.5 m3/s, or 29,808,000 m3/mo), the total concentration of TAN is (10,275 g × 1000 g/kg) / (29,808,000 m3 × 1000 L/m3) = 3.4 × 10-4 mg/L. This value is much lower than the 0.05 mg/L ammonia-N considered toxic to rainbow trout (Table 1). Hence, additional production of trout along the Assi River is possible without substantial environmental impact with respect to ammonia concentration. The analysis is based on the fact that there is no other source of chemical pollution because there are no other industrial facilities along the river. Water Quality in the Assi River Waters samples were collected at eight locations along the river and key water quality variables were measured in the field. Sampling locations included the source of the river, the final dam on the river before the border with Syria, ponds in farm 45 before feeding the fish, ponds in farm 45 after feeding the fish, farm 21 upstream from a group of several juxtaposed farms, farm 28 downstream from the same group of farms before feeding and farm 28 downstream from the same group of farms two hours after feeding. Conductivity, temperature and oxygen were measured with a YSI Model 85 meter (YSI Inc., Yellowstone, OH). A hand-held pH tester (Oakton Model 10) was used to measure pH. Alkalinity and hardness were determined using a LaMotte freshwater aquaculture test kit. Ammonia-N, nitrite-N, nitrate-N and phosphorus were determined using a field spectrophotometer (Hach DR/2400). Water quality parameters did not vary significantly between river and raceways or before and after feeding. The pH varied from 8.0 to 8.2. Alkalinity and hardness averaged 200 mg/L as CaCO3, with minimal variation. Dissolved oxygen concentration averaged 7.93 mg/L at the source, 7.72 mg/L at the outfall from raceways and 9.45 mg/L at the last point on the river. Water at the source contained some ammonia and varied among samples between 0.02 and 0.21 mg/L as N. Ammonia-N concentration increased downriver, reaching 0.35 mg/L. Nitrite was below detectable limits in all samples. Nitrate concentrations increased from the source of the river to downstream, reaching 0.84 mg/L in one sample. Phosphorus concentration was greater at the source (0.15 mg/L) than downstream at the last point on the Lebanese portion of the river (0.06 mg/L). Many farmers attribute low survival of rainbow trout to the degraded quality of Assi River water. However, based on analysis of samples of river water, all water quality variables measured were within the range of no harmful effect to rainbow trout (Table 2). Calculation of ammonia loading showed that, even in the most intensive aquaculture scenario, ammonia was not being released at a concentration beyond the no-harmful effect concentration. Agriculture fertilizers used around the Assi River were not likely to be the cause of ammonia levels in the river for two main reasons: 1) samples did not reveal high nitrate levels, which normally would result from agricultural fertilizers ending up in the stream, along with ammonia and 2) the small quantity and low intensity of precipitation in the Assi River watershed was not likely to cause significant runoff of agricultural fertilizers. Municipal runoff and sewers are likely the main sources of ammonia. A municipal wastewater treatment facility was not operational and wastewater just flowed through to the river. Additionally, most houses and businesses around the river were not connected to the sewer system and dumped directly or had septic tanks that leaked into the river. Recommendations for Regulation of Trout Farming An appropriate legislative framework for aquaculture development and environmental regulations has not been established by the government (Lebbos and Saoud 2006). No license is required from the Ministry of Agriculture. Establishment of a fish farm is subject to regulation by municipal authorities and is considered industry rather than agriculture. Furthermore, although the Ministry of Environment requires an environmental impact assessment (EIA) for any business bordering a river, there are no environmental standards for aquaculture effluents to support EIAs. Based on the principle that the Assi River is a public resource and that access to clean water is a basic right for all citizens, the Ministry of Agriculture must, as a first step, install a licensing system that would 1) acknowledge the existence of the current trout farms near Hermel, 2) give farm owners a grace period to ensure the transition of their facilities to meet established environmental and public health standards and, 3) regulate the establishment of new facilities on the banks of the Assi River. The Ministry of Environment should develop effluent quality criteria for the Hermel trout farmers with the aim of minimizing the discharge of specific pollutants and banning feeding regimes based on animal wastes, even if their current overall concentration is not harmful to the fish or the environment. Those criteria must not only take into consideration the effluents of individual farms but the additive effects of all the farms on the Assi River. Results of the present study suggest that additional loading of ammonia is possible without adverse effects but continuous monitoring is imperative. Also, pollutant sources other than aquaculture should be identified and discontinued. In conclusion, trout farming along the Lebanese portion of the Assi River does not pollute the river with ammonia beyond its assimilative capacity. Education of all stakeholders is necessary to improve farm management protocols to ensure growth of the industry, while maintaining environmental quality. Acknowledgments The authors thank the Department of Fisheries and Natural Resources at the Lebanese Ministry of Agriculture for facilitating this project. Gratitude also goes to the Lebanese National Council for Scientific Research for partially funding the project. Notes Nadim Farajalla and Yara Daou, Department of Landscape Design and Ecosystem Management, Faculty of Agricultural and Food Science, American University of Beirut, Lebanon. I.P. Saoud, Department of Biology, Faculty of Arts & Science, American University of Beirut, Bliss St., Beirut, Lebanon. Phone: + 961 1 374444 ext. 3819. Corresponding author e-mail: is08@aub.edu.lb
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