Biomarkers of exposure in fish inhabiting the Swan-Canning Estuary, Western Australia - a preliminary study

Brief description

Black bream (Acanthopagrus butcheri) were collected from seven sites in the Swan-Canning estuary during August and September 2000 to assess containination to the estuary using the biomarkers - the mixed function oxygenase (MFO) enzyme ethoxyresorufin-O-deethylase (EROD) activity and PAH bile metabolites.

Lineage

Maintenance and Update Frequency: notPlanned

Statement: - Fish collection and dissection -

Black bream were collected by a commercial fisherman, during the months of August and September 2000, from six sites in the Swan River (N = 86) and one site in the Canning River (N = 20) (see thumbnail) using a 120 m, 100 mm monofilament haul net. Sampling dates were determined by barometric pressure, moon phases and prevailing winds. Collection took place between the hours of 10 PM and midnight when the fish entered shallow water for feeding. A sample of water for the measurement of temperature, pH and salinity was collected approximately 45 cm below the draft of the fishing vessel. Upon capture the fish were maintained alive on board in a fibreglass tank with carbon filtered river water. On return to land the fish were transferred to a 1000 L aerated vat filled with river water for transport back to the laboratory. Fish were sacrificed within 2 hours of capture. The fish were weighed and standard, fork and total lengths were recorded. An external examination was conducted for abnormalities and any sign of parasite infestation. A sample of blood was taken from the caudal vein using a vaccutainer. The blood samples were allowed to clot on ice for 15minutes and immediately centrifuged for 10 minutes at 3000 rpm. Each fish was killed by the method of Iki Jimi (spike through the brain), dissected and the bile collected from the gall bladder using a 1 mL syringe and needle. Livers were removed, quickly examined for any anomaly, weighed, rinsed in ice-cold KCl, and a 1-g sample taken for analysis. All samples were immediately placed in liquid nitrogen then later transferred to a freezer and held at -80 degrees Celsius until analysis. Gonads were removed and examined for anomalies then weighed and assigned to one of the following maturity stages; 1 - undeveloped, 2 - early development, 3 - maturing, 4 - pre spawning, 5 - spawning, 6 - spent, using Nikolskii's (1969) scale of gonad development. The gonads and remaining abdominal organs were discarded and the fish weighed to record the carcass weight.

The Condition Factor (CF), Liver Somatic Index (LSI) and Gonadosomatic Index (GSI) were calculated according to the equations:

(1) CF = [(BW - GW)/TL power of 3] × 100
(2) LSI = (LW/CW) × 100
(3) GSI = (GW/CW) × 100

- where BW = total body weight, GW = gonad weight, TL = total length, LW = liver weight and CW = carcass weight. The condition factor is based on gonad-free weight to avoid any bias due to variations in sexual maturation, and the LSI and GSI are based on carcass weight to avoid bias due to variable levels of fat in the gonads and intestines, and variable gonad weight (Hodson et al., 1991).

For methods on determining biomarkers - the mixed function oxygenase (MFO) enzyme ethoxyresorufin-O-deethylase (EROD) activity and PAH bile metabolites, see Methods section of the journal article.

Notes

Purpose
To evaluate the usefulness of biochemical marker techniques for the implementation of a routine monitoring programme in the Swan-Canning estuary using a fish native to the estuary.