An examination of the organic contaminant concentrations revealed that the majority of the samples were reported below the analytical detection limits. Information presented in Tables 3.4a and Table 3.4b indicates that only one of the Polycyclic Aromatic Hydrocarbon (PAH) compounds analysed, Naphthalene, was recorded at detectable levels for at least 15% of the biota samples analysed in samples collected during both the dry season (ie December 1998 and January 1999) and wet season (ie August 1999 and September 1999). More individual PAHs were detected in biota during the wet season sampling (August and September 1999) though only Naphthalene was detected frequently above the detection limit in tissue samples (27% and 33% in August and September 1999, respectively). Of the non-PAH organics, only Total DDT (Tables 3.4a and 3.4b, Figure 3.4a and 3.4b) and Total PCBs (Figure 3.4c and 3.4d) were detected sufficiently frequently above the detection limit to warrant further discussion. TBT was only rarely detected in tissue samples above the detection limit during both the dry (12% and 3% during December 1998 and January 1999, respectively) and wet season (3% and 0% during August and September 1999, respectively). Total PCBs occurred in less than 50% of biota samples during the dry season sampling (ie December 1998 and January 1999) but conversely in greater than 50% of samples during the wet season. Results are also presented graphically for Naphthalene which was the most frequently recorded PAH in the tissues (Figure 3.4 e and 3.4f).

The percentage of stations above the dl was chosen for statistical reasons and follows procedures outlined in other international marine environmental monitoring programmes. A discussion of these statistical methods is provided in international guidelines presented in Clarke & Brandon (1994)(19) . The detection limits used in this Study were very low and below applicable safety criteria. For example, the detection limit for DDT was 0.15 ug kg-1 wet weight and the USFDA action level guideline is 5 mg kg-1 wet weight. The detection limits, therefore, represent very low levels and values reported at or below can be placed in context.

a - 0% to 15% no presentation, 15% to 50% graphical presentation (with discussion for naphthalene only), > 50% discussion with graphical presentation and statistical analysis if detected in greater than 60% of stations.

a - 0% to 15% no presentation, 15% graphical presentation (with discussion for naphthalene only), > 50% discussion with graphical presentation and statistical analysis if detected in greater than 60% of stations