Eastern Orange Roughy 2016 Survey and Biomass Report
CSIRO have released the report on the biomass of orange roughy in the eastern zone. Read the executive summary and download the full report below.
EXECUTIVE SUMMARY
Based on the 2016 acoustic surveys the biomass of spawning orange roughy on the grounds at 38 kHz and 120 kHz ranges from 24 000 (CV 0.12) to 29 600 (CV 0.22) tonnes for observation or process error analysis respectively. There has been a significant 2 fold increase in spawning biomass at St Helens Hill since 2013.
The 38 kHz timeEastern Orange Roughy Survey and Biomass Report 2016 series estimate of spawning biomass in 2016 is now higher than that recorded in 2010 and the long term trend is consistent with a recovery of fish to the spawning sites. The 38 kHz snapshot survey biomass estimate in 2016 of 29 600 tonnes (CV 0.22) extends the index of survey observations since 1990. The 120 kHz biomass estimates were approximately 10% less than the 38 kHz estimates and this relationship is consistent with previous observations (Ryan and Kloser 2016).
The difference between 38 kHz and 120 kHz biomass estimates indicates a source of bias in one or both data sets. Until the source of bias is found the average of the 38 kHz and 120 kHz estimates is recommended. The averaged over frequency combined ground estimate is 27 700 tonnes (CV 0.18) assuming process error dominant and 24 000 tonnes (CV 0.12) assuming observational error dominant.
It is important to note that we an error in the 38 kHz transducer calibration data supplied by the manufacturer and have adjusted this and the 2013 data by 18% accordingly.
