Although egg production (based on mature female abundance) in 2012 was within the historical range, a low proportion of berried females was observed during commercial monitoring and fishery-independent trawl surveys between September 2012 and January 2013, potentially explaining the low recruitment observed in 2013. In 2013, despite a slight increase in catch to 62 t, fishery-independent trawl surveys indicated low recruitment, similar to the low levels preceding the closure in 2006. However, catches remained low at around 50 t, with catch rates declining from 1.1 kg per trap-lift in 2010 to 0.5 kg per trap-lift in 2012. This easing included lengthening the fishing season to six months (December–June) and decreasing the minimum size to the pre-closure size limit of 130 mm CW, while retaining a 20 per cent reduction in trap numbers. At that time, the fishery was assessed to be recovering.īased on improving abundances of juveniles (aged 0+ years) and increased egg production levels in 2010, 20, commercial management restrictions were eased. The commercial fishing season for 2010 was restricted to 3.5 months and minimum size limits were increased from 130 mm carapace width (CW) to 140 mm to ensure that the catch level would enable continued recovery of the spawning stock biomass. Fishery-independent trawl surveys indicated that the strength of recruitment and the spawning stock biomass did not improve sufficiently to reopen the fishery until December 2009. Fishery-independent surveys indicated that low recruitment was a result of high fishing pressure combined with poor environmental conditions, which reduced the spawning stock to low levels and required the closure of the fishery in December 2006. Following a series of high catches (250–350 t) in the late-1990s, the catch declined significantly. A shift by commercial fishers from using gill nets to traps in the mid-1990s resulted in a marked increase in annual crab landings. Historically, variations in recruitment of Blue Swimmer Crabs in the Cockburn Sound (Crab) Managed Fishery and recreational fishery have been driven by environmental conditions, which have caused large fluctuations in stock abundance and annual commercial catch. Here, assessment of stock status is presented at the biological stock level-North-Eastern Australia (Queensland), South-Eastern Australia (New South Wales), Spencer Gulf, Gulf St Vincent and West coast (South Australia), and at the management unit level-Shark Bay, Cockburn Sound, Peel-Harvey Estuary, Western Australian North Coast and Western Australian South-West Coast (Western Australia). In South Australia, research has identified three separate biological stocks of Blue Swimmer Crab-in Spencer Gulf, Gulf St Vincent and on the coastline west of the Eyre Peninsula. Due to the geographic separation between the major fishing grounds for Blue Swimmer Crab in New South Wales and Queensland, they are managed as two separate biological stocks. Stock structure on the east coast of Australia is uncertain, involving overlapping stocks or a semi-continuous stock. The stock delineation between these regions is unknown. In Western Australia, Blue Swimmer Crab is fished in numerous fisheries across five regions. They are also found in the warmer waters of the South Australian gulfs. Blue Swimmer Crab is distributed in Australia from the south coast of Western Australia, north to the Northern Territory, across Queensland, down the east coast and to the New South Wales–Victoria border.
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