2019 Queensland Saucer scallop (Ylistrum balloti) fishery-independent survey

Abstract

In 2019 a fishery independent scallop recruitment survey was conducted along the Queensland east coast from Double Island Point to Yeppoon. The objective of the survey is to produce an index of the relative abundance of 0+ and 1+ scallop age classes that can be compared with previous surveys. 18 survey strata consisting of 310 sites were sampled over 29 nights using commercial shallow water prawn gear. Maheno Inner and Maheno Outer strata have been combined for results and analysis. Data was adjusted using generalised linear models (GLM) to derive mean scallop densities. The findings of the 2019 survey provide:
• Overall survey mean total scallop density of 51.0 scallops per ha is very low.
• 11 of the 17 strata show a decrease in adjusted mean total scallop density compared to 2018.
• 10 of the 17 strata show a decrease in adjusted mean total scallop density from 2017.
• 4 of the 6 SRAs show a decrease in adjusted mean total scallop density compared to 2018.
• 4 of the 6 SRAs show a decrease in adjusted mean total scallop density compared to 2017.
• Increase in adjusted mean total density in Maheno and Sunshine strata compared to 2018.

The analysis also shows:
• That data collected from contemporary surveys (2017 to 2019) can be compared with surveys conducted from 1997 to 2006.
• Modelling adjusted means has been improved by the addition of explanatory terms (lunar phase and time of night that survey trawls was undertaken)
• The effect of introducing TEDs and BRDs to the survey gear show no significant differences in catch rates compared with surveys where these were absent.
The data collected in 2019 will contribute to the formal stock assessment of the stock, which is due to be released in 2020.