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Title:

Understanding the movement, behaviour and post-release survival rates of Swordfish to sustainably develop a new large pelagic game fishery off the coast of Tasmania – a pilot study

Project Number:

2015-022

Organisation:

Institute for Marine and Antarctic Studies (IMAS) Taroona

Principal Investigator:

Sean Tracey

Project Status:

Completed

FRDC Expenditure:

$112,580.00

Program(s):

Adoption, Environment, Industry

Need

Several important questions and opportunities arise with the development of this new recreational fishery. Fishers have already demonstrated a willingness to release this species post-capture. Off the back of the successful post-release survival study on Southern Bluefin Tuna (FRDC project 2013-025) the fishers are interested to understand the post-release survival rates of Swordfish. While the impacts of the recreational fishery to Swordfish populations is expected to be relatively low, due to the niche nature of the fishery, it is truly positive that the recreational fishers would like to have the information at hand to make informed decisions when choosing to release this species as well as potentially reduce the impacts of catching and handling on animals post-release. To address this question satellite tags will be deployed in fish caught using recreational fishing methods off the east coast of Tasmania to monitor their movement and behaviour post-release to determine survival. The methodologies will closely follow those developed and implemented during the successful post-release study on Southern Bluefin Tuna. Another important question relates to whether the fish that are being caught off Tasmania are resident or migratory. The main swordfish population typically inhabit waters further north along the east coast of Australia well up into the Coral Sea. It is expected that the fish available to the recreational fishery off the coast of Tasmania are larger fish that migrate south. It is possible however, that the fish off Tasmania are resident and associating with seafloor features, as they have been found to do further up the coast of Australia (ETBF commercial fisher, pers. comm.). If they are a resident population there is potential for localised depletion, but if their presence here is migratory then a recreational fishery, with appropriate management, can be developed into the long term as the main swordfish population in the Western and Central Pacific is considered to be in a healthy state. The results will also increase our understanding of Swordfish movement and migration by applying tags to fish further south than has been done previously.

Objectives

1. Preliminary quantification of post-release survival rates for Swordfish caught by recreational fishers

2. Determine migratory behaviour of Swordfish caught off the east coast of Tasmania based on data from satellite tags

3. Collect biological samples for use in future molecular stock structure and heavy metal accumulation analyses

4. Deliver a desktop review of contemporary and innovative management methodologies for the sustainable development of recreational opportunities related to large game species (reviewing both aquatic and terrestrial literature).

Understanding the movement, behaviour and post-capture survival of recreationally caught Swordfish from southeast Australia – a pilot study

Final Report
ISBN:978-1-925646-52-8 (print) 978-1-925646-51-1 (electronic)
ISSN:
Author(s):Sean Tracey
Date Published:January 2019
While recreational fishers in Australia have targeted Swordfish in the past, both at night-time with shallow set baits and during the day with deep-set baits, success had been limited with only a few Swordfish reported landed. In 2014, adjacent to the coast of Tasmania an individual fisher had repeated success targeting Swordfish on the continental shelf break using the deep-dropping method during the day-time, fishing in depths of approximately 400 – 600 m. The reporting of this success garnered significant interest by the game fishing community in Australia, and the fishery developed further in Tasmania over subsequent years, as well as southeast Victoria. A small amount of targeted effort using the same methods and subsequent catch was also reported in Western Australia, New South Wales and Queensland. The fishery however is still relatively niche.