World Aquaculture - December 2014

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22 DECEMBER 2014 • WORLD AQUACULTURE •
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 farmmanagement 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 EcosystemManagement, 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: