Temporal variation in lake properties
The results of PCA ordination showed a clear separation between the
years based on the lake water quality properties and fisheries yields
for a 13-year time frame (Figure 2). Of the five axes extracted in the
PCA, only axes 1 and 2 are presented as they explain the majority of the
extracted variance, 93.84% in total, 81.25 %, and 12.59 %,
respectively.
The years 2013 and 2014 ordinated in the upper left of the biplot and
are characterized as having high TN concentrations and total fish yields
while, the years from 2008 to 2012 are ordinated to the lower right and
characterized by having higher turbidity concentrations ranging between
73.69-185 NTU, higher WQI values fluctuating between 860.19 and 1443.47,
higher TP levels varying from 146.66 to 240.35 µg. L-1indicating periods of poor water quality and high yearly water level
fluctuations measured as yearly amplitude (1.56-9.36 m). Besides, the
years 2015 to 2020 that were ordinated in the upper and lower left of
the biplot are characterized by having higher DLTM, indicating an
increase in the annual lake water levels relative to the long-term
average. The other water quality parameters such as DO and temperature,
known to affect assemblages and lake function, were not strong
descriptors in the grouping of years using the first two components
(Figure 2).