Resource Assessment Report No.3 Scallop Resource April 2019 Mervi Kangas, Sharon Wilkin, Errol Sporer, Arani Chandrapavan, Nick Breheny, Dean Meredith i Executive Summary Saucer scallops, Ylistrum balloti (formerly Amusium balloti), are fished using otter trawls in four separate fisheries in Western Australia. The Shark Bay Scallop Managed Fishery (SBSMF) is usually Western Australia’s most valuable scallop fishery with boats licensed to take only scallops (11 Class A licenses) and boats that also fish for prawns (18 Class B licenses). The second largest scallop fishery is the Abrolhos Islands and Mid-West Trawl Managed Fishery (AIMWTMF). The South West Trawl Managed Fishery (SWTMF) and the South Coast Trawl fishery (SCTF) are multi-species fisheries that primarily target scallops. Management is generally based on limited entry, gear controls and seasonal closures however Shark Bay undertook a catch quota trial between 2014 and 2017 with an allocation between the Class A and B sectors and this has been formalised since 2017. The AIMWTMF is managed according to a “constant escapement policy” designed to ensure that a minimum level of scallop spawning stock is left at the end of each fishing season. This thereby helps to ensure that fishing does not deplete the residual stock to a level that then impacts on recruitment. The harvest strategy for the two key fisheries recognise that scallop recruitment is naturally highly variable and unpredictable. Thus, control rules are in place to provide the spawning stock with a very high level of protection in years when scallops are naturally low in abundance. The other two smaller scallop fisheries consist of a small number of licenses and low fishing activity in which fishing effort is related to the abundance of scallop in any given year, which can be highly variable (due to sporadic recruitment). Broader management objectives for all scallop fisheries are to; ensure that bycatch, in particular large animals including turtles, is minimised and that the effects of fishing do not result in irreversible changes to ecological processes. Catches in these fisheries vary widely depending on the strength of recruitment, which is thought to be influenced by the strength of the Leeuwin Current and water temperature. Extreme environmental events, as was observed with a marine heatwave in the summer of 2010/11 had a significant impact on scallop stocks, particularly in Shark Bay and the Abrolhos Islands with closures of 3-5 years and variable recovery in these stocks since. In the SBSMF and AIMWTMF annual fishery-independent scallop surveys have been undertaken and provide size and abundance information from standardised sites. These data are used to determine an index of abundance that provides the basis for predicting the catch the following year and for setting the TACC in Shark Bay. The stock status of all the scallop fisheries in 2017/18 was sustainable but a significant stock decline was evident in November 2018 in northern Shark Bay to below the reference level requiring consideration for a recovery strategy. ii Table of Contents Executive Summary ................................................................................................................... ii Table of Contents ..................................................................................................................... iii List of Abbreviations ................................................................................................................ vi Scope ..................................................................................................................................... 1 How the Department Operates .............................................................................................. 1 Aquatic Environment ............................................................................................................ 2 Shark Bay............................................................................................................. 2 West Coast and South Coast ................................................................................ 3 Resource Description ............................................................................................................ 4 4.1 Scallop Resource ........................................................................................................... 4 4.2 Selection of Indicator Species for Resource.................................................................. 5 Species Description ............................................................................................................... 6 5.1 Saucer scallop (Ylistrum balloti) ................................................................................... 6 Taxonomy and Distribution ................................................................................. 6 .............................................................................................................................. 6 Stock Structure..................................................................................................... 6 Life History .......................................................................................................... 7 Inherent Vulnerability ........................................................................................ 22 Fishery Information ............................................................................................................. 23 6.1 Fisheries / Sectors Capturing Resource ....................................................................... 23 6.2 SBSMF ........................................................................................................................ 24 History of Development .................................................................................... 24 Current Fishing Activities.................................................................................. 25 6.3 Illegal, Unreported or Unregulated Fishing ................................................................ 29 6.4 AIMWTMF ................................................................................................................. 29 History of Development .................................................................................... 29 Current Fishing Activities.................................................................................. 30 Fishing Methods and Gear ................................................................................. 32 6.5 Illegal, Unreported or Unregulated Fishing ................................................................ 33 6.6 SWTMF ....................................................................................................................... 33 iii History of Development .................................................................................... 33 Current Fishing Activities.................................................................................. 34 Fishing Methods and Gear ................................................................................. 36 6.7 Illegal, Unreported or Unregulated Fishing ................................................................ 36 6.8 SCTF ........................................................................................................................... 37 History of Development .................................................................................... 37 Current Fishing Activities.................................................................................. 38 Fishing Methods and Gear ................................................................................. 39 6.9 Illegal, Unreported or Unregulated Fishing ................................................................ 39 Fishery Management ........................................................................................................... 40 7.1 Management System ................................................................................................... 40 7.2 Harvest Strategy .......................................................................................................... 40 7.3 External Influences ...................................................................................................... 42 Environmental Factors ....................................................................................... 42 Climate Change ................................................................................................. 42 Introduced Pest Species ..................................................................................... 42 Market Influences .............................................................................................. 43 Non-WA Managed Fisheries ............................................................................. 43 Other Activities .................................................................................................. 43 Information and Monitoring ................................................................................................ 43 8.1 Range of Information .................................................................................................. 43 8.2 Monitoring ................................................................................................................... 44 Commercial Catch and Effort ............................................................................ 44 Processor Returns 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