Annual status report 2009 Mud Crab Fishery Queensland Primary Industries and Fisheries, part of the Department of Employment, Economic Development and Innovation (DEEDI), seeks to maximise the economic potential of Queensland’s primary industries on a sustainable basis. While every care has been taken in preparing this publication, the State of Queensland accepts no responsibility for decisions or actions taken as a result of any data, information, statement or advice, expressed or implied, contained in this report. © The State of Queensland, Department of Employment, Economic Development and Innovation 2009. Copyright protects this material. Except as permitted by the Copyright Act 1968 (Cth), reproduction by any means (photocopying, electronic, mechanical, recording or otherwise), making available online, electronic transmission or other publication of this material is prohibited without the prior written permission of the Queensland Primary Industries and Fisheries. Inquiries should be addressed to: Intellectual Property and Commercialisation Unit Queensland Primary Industries and Fisheries GPO Box 46 Brisbane Qld 4001 or [email protected] Tel: +61 7 3404 6999 Annual Status Report 2009—Mud Crab Fishery 1 Fishery profile 2008 Species targeted Fishery season Mud crab All year round Total harvest from all sectors Commercial licences active in 2008 Approximately 1676 t1 531 as of December 20082 Commercial harvest Commercial licences accessing the fishery in 2008 1025 t 431 Recreational harvest (2005) Fishery symbol 638 t C1 Indigenous harvest (2001) Monitoring undertaken 3 12 t Commercial logbooks (CFISH), fishery independent monitoring Charter harvest Accreditation under the EPBC Act 1.2 t Expires 21 August 2012 Commercial Gross Value of Production (GVP) Logbook validation Approximately $16.4 million Yes–completed May 2007 Sector contribution to total catch Quota managed Predominately commercial No Key fish resources Stock status Mud crab (Scylla spp.) Not assessed Comment: Mud crab will be assessed as a part of the QPIF stock status reporting program roll out in 2009–10. 1 For the purpose of this report, the total harvest estimate for 2008 includes the recreational harvest estimate from 2005, based on the assumption that the subsequent years of catch would be similar. 2 Approximately one third of C1 licences have been removed through the ongoing latent effort process. 3 The indigenous estimate is derived from the 2000-01 National Recreational and Indigenous Fishing Survey (NRIFS). There are no indications to suggest that harvest levels will have changed significantly between 2001 and 2008. Annual Status Report 2009—Mud Crab Fishery 2 Introduction Key species Mud crabs (Scylla spp.) are found throughout the Indo- The target species of the Queensland Mud Crab Fishery is Pacific region. In Australia, mud crabs are found in Scylla serrata, a portunid crab known as a mud crab. tropical and subtropical areas in association with mangrove-lined estuaries from southern New South Information contained in this section of the report was Wales, north to the Exmouth Gulf in Western Australia. sourced from Gribble, Brown and Williams 2002. Mud crabs are highly desired in both the commercial and Mud crabs are widely distributed throughout coastal recreational sectors. Queensland is unique among Queensland waters. Juveniles and adults generally Australian states in protecting all female mud crabs and occupy the same habitat within sheltered estuaries, tidal only allowing males to be harvested. reaches of mangrove-lined rivers and streams, mangrove This report covers the 2008 calendar year. forests and mud flats. Mud crabs are omnivorous scavengers consuming a diet Fishery Description of barnacles, molluscs and carrion. Mud crabs are also Fishing area and methods known cannibals, readily eating other crabs. Claws aid in the eating process, the larger claw is often used for Commercial operators are permitted to use traps and crushing shellfish such as mussels, while the smaller crab pots (with rigid or collapsible frames). In addition to claw is used for biting, cutting and manipulating the pots and traps, recreational fishers are also permitted to food. Mud crabs are nocturnal feeders and usually use dillies.4 Crab pots are defined as a fishing apparatus remain in the protection of their burrow during the day, comprising a cage; dimensions of the pots vary but most emerging in the early evening and just before dawn to are cylindrical and have two entrance funnels. Mud crabs feed. are enticed into the pot or trap by bait attached to the inside of the apparatus. Mature crabs mate when the female is in the soft-shell condition. Sperm is stored until the eggs are extruded. The fishing area covers the majority of Queensland tidal The female remains in the shelter of the burrow, under waters, except closed waters (Figure 1). the protection of the male, for several days until her new shell has hardened. Multiple spawning events in the one season may follow a single mating, with each egg mass containing from two to eight million eggs—dependant on the size of the female. Egg-bearing females migrate to deep waters offshore to spawn. Embryonic development takes approximately two to four weeks—dependant on water temperature—after which time the eggs hatch and enter a four stage pelagic existence. The larvae drift inshore via currents and transform into a semi-pelagic state before settling onto suitable substrate in shallow water. At approximately five to twelve days they metamorphose into juvenile crabs. As with other crustaceans, growth occurs through moulting. This involves the shedding of the hard shell, and then swelling of soft body tissues to expand the new soft shell before it hardens. Growth is seasonal, with Figure 1: Boundary and regional delineations of moulting occurring mainly between the months of the Mud Crab Fishery. 4 Inverted dillies or ‘witches hats’ are currently being phased out, and will be prohibited by April 2010. Annual Status Report 2009—Mud Crab Fishery 3 September and January. Growth rate appears to be Barrier Reef Marine Park Act 1975 and the Queensland accelerated in warmer northern and Gulf waters. Brown Marine Parks Act 2004). (1993), summarised a number of studies on mud crab growth and sexual maturity from a variety of latitudes, Catch statistics and found a considerable degree of variation in both age The majority of mud crabs are taken commercially (61%), and size at which mud crabs reach maturity. with just over a third of the total harvest retained by the Scylla olivacea, the brown mud crab, is also found within recreational sector (38%). Compared with the harvest by Queensland waters in the northern part of the Gulf of the commercial and recreational sectors, the annual Carpentaria. Scylla olivacea requires low salinity harvest of mud crabs by the Indigenous and charter estuarine habitats and therefore its distribution and sectors is considered very low (less than 1%). abundance is limited. Physically this species is Commercial extremely similar to—and as a result is often mistaken Whole fishery for—Scylla serrata; however, Scylla olivacea rarely grows to minimum legal size (15cm carapace width). Due to the The annual reported commercial mud crab catch in geographical limitations of Scylla olivacea, commercial Queensland increased from 963 t 5 in 2007 to 1025 t in fishers typically only harvest small quantities of this 2008 (Table 1, Figure 2). In 2008, the Queensland Mud species. Crab Fishery recorded 431 active fishers; this is the highest number of active participants since 2004. Fast growth rates, early maturity, wide distribution and high fecundity are all biological characteristics that Table 1: Catch and effort data for the commercial harvest of Mud Crabs, 1998–2008 (Source: QPIF CFISH database, contribute to the resilience of mud crabs to harvest. 31 July 2009). CPUE Main management methods used Year Licences Days Weight (t) (kg/day) Queensland Primary Industries and Fisheries (QPIF), 1998 436 31909 676 21.19 manages the Queensland Mud Crab Fishery in 1999 448 37057 838 22.62 accordance with ecologically sustainable development 2000 464 39574 1035 26.14 2001 488 39452 1029 26.09 (ESD) principles. The fishery is managed under the 2002 481 40753 1014 24.89 Queensland Fisheries Act 1994 and in accordance with 2003 499 48934 1149 23.49 the Queensland Fisheries Regulation 2008. 2004 496 46701 1178 25.22 A range of input and output controls are in place to 2005 424 40412 969 23.97 manage the harvest of mud crabs by commercial and 2006 425 39557 983 24.86 recreational fishers, including: 2007 423 38413 963 25.06 2008 431 38002 1025 26.97 • a minimum legal size limit that applies to both commercial and recreational fishers (150 mm carapace A pattern exists in monthly mud crab harvest fo r the width) fishery; logbook data shows record high catches of mud crab during the summer and autumn months (between • a prohibition on taking female crabs December and May). Catches during these months • apparatus restrictions (50 pots per licence for the contribute between 66-72% of the total reported commercial fishery and four pots per person for the commercial catch for the year (range calculated using recreational fishery) 2004–08 data). • limited entry to the commercial fishery (C1 In 2008, a decrease in fishing effort (days) and increase endorsement required) in retained weight has resulted in an increase in catch per unit effort (CPUE). CPUE increased from 25.06 kg/day • prescriptions on the size of the float that may be used in 2007 to 26.97 kg/day in 2008 (Table 1, Figure 2). This • closures (Eurimbula Creek and all adjoining waterways are closed to the harvesting of mud crabs, along with closures enforced through marine park zoning 5 Reported catch for 2007 has increased since QPIF’s established under the Australian Government Great previously stated catch due to late logbook returns from a small number of fishers.