A study of fisheries ecology at Benwenerup, or Stokes Inlet, west of Esperance is helping to deliver an important scientific assessment of this culturally significant waterway, the Western Australia Department of Primary Industries and Regional Development (DPIRD) said in a statement on Tuesday, July 9. Local Tjaltjraak Rangers and the DPIRD are working together to gather and share data and knowledge about the waterway through sampling fish, monitoring water quality, and collecting and analysing shoreline debris.
The Rangers are running their Healthy Land and Sea Country Program and working with DPIRD Aquatic Science and Assessment scientist Tim Leary to conduct a fishery independent black bream stock assessment based on a longitudinal sampling program. As part of the research, the Rangers helped set and retrieve nets, took water quality measurements within the estuary, and worked in a laboratory setting to dissect fish and remove otoliths (ear bones) to help assess species’ ages.
This study also involves testing for the presence of nano-plastics in fish tissue, another initiative of the Tjaltjraak Healthy Land and Sea program that implements projects determined by the Traditional Owners, the Kepa Kurl Wudjari people, through the Esperance Tjaltjraak Native Title Aboriginal Corporation. Tjaltjraak Rangers carry out six sampling periods across a year to coincide with the Wudjari cultural seasons to understand the annual changes within the inlet.
Mr Leary said the sampling enabled assessment of the condition of the inlet through fish ecology, water quality testing, and observation of plastics in the environment or when detected in processed samples of black bream, yellow-eye mullet, and sea mullet.
DPIRD and the Tjaltjraak Rangers have also visited Lake Warden north of Esperance – part of the Kepwari Cultural Corridor and RAMSAR-listed wetlands – to take water samples, assess the water quality, and analyse it for phytoplankton. Mr Leary said Lake Warden was the site of a recent fish kill incident in May, so it was important to conduct a follow-up check with the Rangers and update the Department of Water and Environment Regulation monitoring.