Using scales and otoliths to trace life histories of barramundi (Lates calcarifer) from north Queensland

Fish scales and sagittal otoliths from barramundi were analysed to determine whether types of habitats - freshwater lagoons, rivers and weirs; estuarine; marine - could be identified from the known lifecycle history of individual fish. The experiments ran between July 2000 and February 2003. Elemental abundances (Ba, Ca, Fe, K, Mg, Mn, Na, P, S, Sr) and Sr isotopic compositions were analysed using in situ laser ablation (UV) multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) measurements. Multiple additive regression tree (MART) and linear discriminant analysis (LDA) were used to classify otolith scales as estuarine or freshwater and validated against the known history of caged fish subjected to repeated scale sampling at capture, after 82 and 240 days, and at death (between 99 and 310 days). An Sr fingerprint was created which was able to group otoliths to the fish's source locatuion.Sample fish were captured from Cape Cleveland, Magnetic Island, Gordon Creek, Upper Alligator Creek, Inkerman Station, Black's Weir; and from dry tropic (Burdekin, Barrattas, Haughton, Ross) and wet tropic (Herbert, Johnstone) rivers.Note was also made of fish size (total length; small, 625mm). To determine whether types of habitats (e.g. freshwater or estuarine) could be identified from scales and otoliths and verified against the known lifecycle history of individual fish in the sample.