Interannual variability in fish biomarkers in a contaminated temperate urban estuary

Brief description

Data from sampling black bream from four sites in late winter 2000 and late winter 2002 in addition to five sites during summer 2001 and summer 2002 from the Swan-Canning Estuary are compared to determine whether patterns of responses within the estuary were sufficiently strong to overcome natural annual variability.

Lineage

Maintenance and Update Frequency: notPlanned

Statement: - Fish and Sample Collection -

Black bream were collected by a commercial fisherman, during the late winter months of August and September 2000 and 2002, from the four sites in the Swan River (N = 69 and 76 for each year, respectively). During late summer (April-May) in 2001 and 2002, the same four Swan River sites (N = 84 and 64 for each year, respectively) were sampled together with an additional site at Riverton in the Canning River (N = 16 and 21 for each year, respectively) (see thumbnail).

Sampling occurred when barometric pressure, moon phases, and prevailing winds were favorable for black bream commercial fishing. A 120-m, 100-mm monofilament haul net was used to capture adult black bream. Collection took place between 2200 and 2400 h when the fish entered shallow water for feeding. Water samples, collected at a depth of approximately 2m, were measured for temperature, pH, and salinity. Upon capture, the fish were maintained alive on board in a fiberglass tank withca rbon-filtered river water. On return to shore, the fish were transferred to a 1000-L aerated vat filled withriver water for transport back to the nearby laboratory. Fish were sacrificed within 2 h of capture.

Fish were weighed, standard, fork, and total lengths were recorded, and an external examination for any signs of abnormalities or parasitic infestation was conducted. A sample of blood from the caudal vein was taken using a vaccutainer. The blood samples were allowed to clot on ice for 15 min and then centrifuged for 10 min at 3000 rpm, and the serum was collected. Each fish was then killed by a spike through the brain (Iki Jimi method) and dissected, and the bile was removed from the gall bladder using a 1mL syringe and needle. Livers were detached, quickly examined for any anomaly, weighed, and rinsed in ice-cold KCl, and a 1-g sample was placed in a cryovial for subsequent analysis. All samples were immediately immersed in liquid nitrogen and then transferred to a -80 degrees C freezer until analysis.

Gonads were removed, examined for anomalies, 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 weight of each liver and gonad was recorded. 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.