Frusher, SD and Ewing, G and Rizzari, J and Colquhoun, RE, Developing cost-effective industry based techniques for monitoring puerulus settlement in all conditions: Phase2, Fisheries Research and Development Corporation, Deakin ACT, FRDC Project No 2014/025, July (2018) [Government or Industry Research]
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In phase 1 of this project a design for a deep water collector was developed through consultation with industry and prototypes of this design were constructed and tested in aquaria with captured pueruli, on the seafloor adjacent to an existing inshore shallow collector site on the east coast of Tasmania, and in deep water on the south and southwest coasts of Tasmania. The prototype collectors were successfully deployed, retrieved and serviced by vessels in the commercial lobster fleet and vessel masters reported that the design facilitated safe and efficient handling on deck. The prototypes collected significantly more puerulus than adjacent routine collectors in deployments at the shallow site and collected puerulus for the first time on the deeper and more exposed southwest coast of Tasmania.
This phase 2 of the project saw deployment of a refined collector design onto reefs around Tasmania over 2 puerulus settlement seasons and provided evidence that; (1) puerulus settle in larger numbers in shallow inshore waters; (2) puerulus settlement in deeper water varies in space, time and depth around the Tasmanian coast (eg. Puerulus settlement was higher on the south coast than on the east coast in the 2016/2017 settlement season and puerulus settlement in waters deeper than 100m appears to be very low).
When deployed alongside traditional diver based collectors, the fisher-serviced puerulus collector captures and retains more puerulus than traditional diver-based methods and is more cost-effective per collector. However, refinements to the design would be required for its use in inshore puerulus monitoring due to siltation issues from mobile sediments in exposed inshore locations.
Despite experiencing lower catch rates than inshore settlement monitoring, the number and consistence of settlement on offshore deeper water collectors enabled similar temporal patterns of settlement to be determined. The deep water collectors also retained puerulus for similar periods to the traditional collectors. Consequently, deep water puerulus collection is a feasible alternative to costly inshore diver-serviced monitoring programs and would be expected to indicate similar trends in recruitment. Industry involvement in servicing offshore collectors during routine fishing operations greatly increases the cost- effectiveness of this approach; particularly if this support was provided without the requirement for financial compensation.
|Item Type:||Government or Industry Research|
|Keywords:||puerulus, larval settlement, deep water, lobster fisheries, industry monitoring|
|Research Division:||Agricultural and Veterinary Sciences|
|Research Group:||Fisheries Sciences|
|Research Field:||Fisheries Management|
|Objective Division:||Animal Production and Animal Primary Products|
|Objective Group:||Fisheries - Wild Caught|
|Objective Field:||Fisheries - Wild Caught not elsewhere classified|
|UTAS Author:||Frusher, SD (Professor Stewart Frusher)|
|UTAS Author:||Ewing, G (Mr Graeme Ewing)|
|UTAS Author:||Rizzari, J (Dr Justin Rizzari)|
|UTAS Author:||Colquhoun, RE (Mr Ruari Colquhoun)|
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