Oral Presentation Australian Society for Fish Biology Conference 2017

Connectivity of fishes from the Kimberley region, Western Australia, using otolith geochemistry (#55)

Sarah Hearne 1 , Alison Blyth 2 , Jennifer McIlwain 1 , Michael Travers 3 , Kate Trinajstic 1
  1. Department of Environment & Agriculture, Curtin University, Perth, WA
  2. Department of Applied Geology, Curtin University, Perth, WA
  3. Department of Fisheries, Perth, WA

Understanding the connectivity of fish populations is vital for the effective management of fish stocks, and otolith geochemistry has become a popular source of information for understanding population connectivity. The remote Kimberley region of Western Australia has been historically understudied, resulting in a lack of population data that has limited the ability to sustainably manage fisheries in the area. This project aimed to determine if population connectivity could be determined in two species of coral reef fishes common to the region, Lutjanus carponotatus and Pomacentrus milleri through the use of otolith geochemistry. A suite of geochemical analyses were used to analyse otoliths from both species: trace elements using LA-ICPMS (laser ablation inductively coupled plasma mass spectrometry), strontium isotopes using MC-ICPMS (multi-collector ICPMS) and oxygen isotopes using SIMS (secondary ion mass spectrometry). Preliminary results indicate that there is a statistically significant difference in trace element composition between L. carponotatus from the north and south of the collection area. P. milleri showed no statistically significant differences, however their geographical collection range was highly restricted compared to L. carponotatus. Preliminary strontium isotope results show no difference, indicative that the fish are fully marine throughout their lives. Preliminary oxygen isotope results for P. milleri are suggestive of sex-mediated movement. The trace element results indicate that there is population structure within L. carponotatus but this structure is only visible at the largest scale. However, this may be due to the relatively low resolution of the analysis. High resolution SIMS data detected subtle changes in isotopes indicative of ontogenetic movement and it may be than in the potentially homogenous waters off the West Australian coast these high resolution techniques are required for fine scale differentiation. These results suggest that SIMS may be a useful technique for studying finescale movements within marine populations.