International Journal of Marine Science 2016, Vol.6, No.27, 1-22
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for 79.8% of the total variation. Scores on PC1 were positively correlated with Revelle factor and nitrates but
negatively correlated with pH and Carbonate ion concentration (Table 2). High scores on PC1 were thus
associated with increasing Revelle factor and nitrates and decreasing pH and carbonate ion concentration. Both
seasons sampled in the artisanal fishery loaded negatively on PC1 (Table 8), and thus inversely correlated with the
scores on PC1. Abundance and diversity in the artisanal fishery increases with decreasing pH and carbonate ion
concentration and decreases with increasing Revelle factor and nitrates. Both seasons in the semi-industrial
fishery except the third month of the lean season which was not significant (P < 0.4) loaded positively on PC1
(Table 8). Thus with the exception of month 3 sampled in the lean season in the semi-industrial fishery,
abundances of species observed in all other seasons of the two fisheries probably increased with increasing nitrate
levels and an increasing Revelle factor, while they decreased with decreasing pH and carbonate ion concentration.
Scores on PC2 were positively correlated with nitrates and negatively correlated with total alkalinity. Thus scores
on PC2 increased with increasing nitrates and decreasing total alkalinity.
Table 7: Summarised PCA values on Physico-chemical parameters that relate with species abundance in the two fisheries for both
seasons
Variables
PC1
PC2
Total alkalinity (µmol/kg)
0.235
-0.684*
pH
-0.504*
0.204
Carbonate ion concentration (µmol/kg)
-0.458*
-0.168
Nitrates (mg/l)
0.396*
0.505*
Phosphates (mg/l)
0.293
0.378
Revelle factor
0.489*
-0.255
Eigenvalue
3.420
1.370
% variance explained
56.90
22.80
Cummulative % variance
56.90
79.80
Values with * are significant at 5% significance level.
Table 8: Principal component scores for fishery/season which loaded on selected principal components
Principal Component scores
Fishery/Season
PC1
PC2
Teshie-M1Lean
-1.10*
0.36
Teshie-M2Lean
-0.64*
-1.66*
Teshie-M3Lean
-1.95*
0.71*
Teshie-M1Peak
-1.48*
0.21
Teshie-M2Peak
-2.12*
0.14
Teshie-M3Peak
-1.30*
0.04
Tema-M1Lean
-1.29*
0.13
Tema-M2Lean
1.97*
-1.28*
Tema-M3Lean
0.16
-1.46*
Tema-M1Peak
1.43*
-1.38*
Tema-M2Peak
2.15*
0.31
Tema-M3Peak
2.14*
-0.18
Tema-M4Peak
3.43*
2.41*
Tema-M5Peak
-1.40*
1.64*
Values with * are significant at 5% significance level.
