International Journal of Marine Science 2016, Vol.6, No.27, 1-22
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Three months in the lean season in the semi-industrial fishery loaded negatively on PC2 and two months in the
peak season loaded positively on PC2 (Table 3). Thus, abundance and diversity observed in the lean season of the
semi-industrial fishery reduced with increasing nitrate levels and increased with decreasing total alkalinity
whereas abundances observed in the peak season increased with increasing nitrate levels and decreased with
decreasing total alkalinity.
Figure 6: PCA showing relationship between fishery and seasons sampled and the six principal variables
3.4 Relationship between environmental variables and species abundance
A Canonical Correspondence Analysis further explained the relationship between the six identified principal
variables and fish species that occurred in the seasons and fisheries. For the lean season of the artisanal fishery, the
first two axes cumulatively explained 100% of the variation found in species abundance as a result of the selected
environmental variables, with axis 1 alone accounting for 91.3% of the variation. The first ordination axis
reflected species with a gradient related to pH, nitrates and phosphates on the positive end of the axis and Revelle
factor, total alkalinity and carbonate ion concentration on the negative end. The second axis had pH and nitrates
on the positive end and phosphates, Revelle factor, total alkalinity and carbonate ion concentration on the negative
end (Figure 7).
Figure 7: CCA biplot showing relationship between dominant fish species identified in the lean season of the artisanal fishery
-4
-2
0
2
4
PC1
-2
0
2
4
PC2
Teshie-M1Lean
Teshie-M2Lean
Teshie-M3Lean
Teshie-M1Peak
Teshie-M2Peak Teshie-M3Peak
Tema-M1Lean
Tema-M2Lean
Tema-M3LeanTema-M1Peak
Tema-M2Peak
Tema-M3Peak
Tema-M4Peak
Tema-M5Peak
TOTAL ALKALINITY (umol/kg)
REVELLE FACTOR
PH
CARBONATE
Nitrates
Phosphates
-1.0
1.5
-1.5
1.0
S.dorsal
B.auritu
S.sphyra
G.decada
C.chrysu
C.hippo
T.ovatus
L.laevig
TOTAL AL
REVELLE
PH
CARBONAT
Nitrates
Phosphat
