Monitoring of the Gonad of Rabbitfish Siganus guttatus in an Oil Spill -Affected and Unaffected Area

Gonad development of rabbitfish Siganus guttatus from an oil spill affected (Taklong Island) and unaffected (Ave Maria Sanctuary) area in Guimaras province were monitored from November 2007 to December 2008. There were instances wherein samples could not be collected in both sites at the same period since tidal change was not abrupt so that the fish did not migrate to the seagrass bed where they fed and eventually get caught in the barrier net. Male rabbitfishes sampled from both area had 23-400 g body weight (BW) and 6.15-29.00 cm total length (TL) while females had 25-753 g BW and 6.50-31 cm TL. The fish were dissected and gonads were preserved in Bouin’s solution. The left lobe of the gonad was used for histological procedures. Due to limitations in measuring the gonad weight in the site, the gonads were weighed after being preserved for several months. The range of the gonadosomatic index (GSI) of the males in Taklong Is. was 0.02-8.39 and 0.04-3.25 in the Ave Maria Sanctuary. Male GSI in Taklong was lower in May and June, higher from July to November but the same in December. For the females, GSI range was 0.1-7.78 in Taklong Is. and 0.03-1.68 in Ave Maria Sanctuary. Female GSI in Taklong was lower in June and December, the same in July but was higher in August and November. Results in the GSI did not seem to show a clear difference between the oil spill affected and unaffected area. A comparison of the maturity stages of the testes and ovaries of sampled fish from both areas also showed no distinct difference between the oil spill affected and unaffected area. These results indicate that more than a year after the oil spill incident, gonad development of S. guttatus were already not affected