Fisheries long term monitoring program : Scallop (Amusium japonicum balloti) survey results: 1997-2006

Abstract

In Queensland, saucer scallops (Amusium japonicum balloti) are a target or principal species in the east coast otter trawl fishery. The fishery operates from about 20o S to the New South Wales border. The fishery is currently managed by a series of input and output controls, including spatial and temporal closures, effort and gear regulation and minimum size limits. In 2006, the annual Queensland saucer scallop harvest was estimated at 504 tonnes (CFISH database June 2007).
Decreasing total catch and catch rates combined with consistently high effort from 1993 until 1996, raised concern amongst fishers and fisheries managers regarding the sustainability of the stock. A precautionary management approach led to the creation in 1997 of scallop replenishment areas, three areas closed to fishing in the Yeppoon, Bustard Head and Hervey Bay regions. In 2001, these scallop replenishment areas were expanded and opened to fishing according to a rotational harvest strategy. The objective was to allow fishers access to the high densities of post spawning scallops that develop within the replenishment areas. The current rotational strategy allows for a 9 month fishing period, followed by a 15 month closure.
Since 1997, the Department of Primary Industries and Fisheries has carried out an annual scallop survey. In its initial phase this survey was a pre-recruitment survey. The objectives were to provide a long-term data series that when combined with existing fishery monitoring programs and historical data would assist in the assessment of the resource status and contribute to assessment of the performance of management strategies. The objectives of the survey were revised in 2001 corresponding with the introduction of a rotational harvest strategy for the scallop replenishment areas. Current objectives focus on assessing the performance of the rotational harvest strategy.
Standardisation of scallop survey catch rates allows data from 1997 to 2006 to be directly compared. This report presents mean scallop catch rates rather than scallop abundance. Numbers and length frequencies of Moreton Bay bugs and blue swimmer crabs are also reported.
Lows in scallop catch rates were seen in 2002 and 2003 and 2005. In 2004 both age classes monitored were relatively strong. The 2006 increase in numbers was largely due to increased catch of scallops older than one year old (1+). Blue swimmer crabs were also caught in low numbers in 2005.
The only species of conservation interest encountered during the surveys have been syngnathids and sea snakes. Both of these taxonomic groups have been encountered in relatively low numbers.