The Great Swordfish and Striped Marlin Race

Learning more about billfish that visit NSW waters

Tagged Swordfish released by anglers

This research aims to learn more about movement and behaviour of swordfish and striped marlin caught off the NSW coast and their post-release survival.. Tagging is being carried out by using experienced anglers to deploy pop-up satellite tags into fish caught  in NSW waters.

How does a pop-up satellite tag work?

Pop-up satellite archival tags (PSATs) are used to track the movement of marine animals, particularly highly migratory species such as sharks, tuna and billfish. The tags are like mini computers that are externally attached to the fish and travel along with the fish whilst logging information on water depth, light levels and temperature, and gathering information on its location (geolocation).  This allows us to gain a greater understanding of the behaviour of the fish, their migratory patterns and catch and release survival.  The great benefit of satellite tags is that they do not have to be retrieved to collect the recorded information. After a predetermined time the tag decouples from the fish and ‘pops-off’, floating to the surface. The tag then transmits the data that it has stored whilst it has been underwater to orbiting satellites that pass overhead. This data is then relayed back to DPI. Complex statistical models process the data to estimate the most likely movement track.

The project will provide us with data on the on the timing and availability of swordfish and striped marlin in NSW and their post release survival. DPI is undertaking the project with the Australian National Sportfishing Association (NSW) and NSW Game Fishing Association.

The Great Swordfish and Striped Marlin Race

Striped Marlin underwater Image Al McGlashanThis project also includes the “Great Swordfish and Striped Marlin Race” which plans to provide an interactive experience to improve our understanding of these exciting billfish species.

Once the first fish has been tagged, the race will be underway for the individual billfish  that travels the furthest distance whilst tagged.

We will keep you updated on the Race and the broader project on this page and on the DPI Fisheries Facebook page, including when fish have been successfully tagged. Information on movement of the fish will be provided when the tags pop-off the fish and their movement data is streamed back to us via satellite.
Striped marlin: Al McGlashan

Why we are undertaking the project

It is important that we learn more about recreational billfish fisheries, to enable them to grow and maximise their potential whilst ensuring the sustainability of the fisheries are maintained.

The project will:

  • research the availability of key billfish along the NSW coast to provide seasonality information and connectivity with the broader east coast population.
  • run the “Great Swordfish and Striped Marlin Race” to engage anglers and the community on this interactive learning experience.
  • Improve knowledge on catch and release mortality.

Tagged Swordfish # 1

Tag Ref.Skipper Date deployedLocation Date pop-upLocation
NSWSword#1 Chris Cleaver 24/04/2019 South Sydney 30/07/2019 Dampier Ridge - west of Lord Howe Island

Satellite Track of Tagged Swordfish


Depth and Temperature Profile

Depth and Temperature Recorded by Satellite Tag

The depth data shows that the swordfish carried out the well established diurnal pattern of diving deep during the day (around 400 - 600m+) and rising near to the surface at night. There appears to be some change to the behaviour around the end of May, where the daytime dives don’t go as deep (150 – 300m+) before the normal dive pattern to 500m+ resumes. You can see the surface water temperatures were relatively high at around 24 degrees when the fish was first tagged off Sydney and they steadily drop off to around 19 degrees when the tag popped off west of Lord Howe Island. The fish headed south towards the south east corner of Australia before it meanders eastwards and then heads on a more northerly bearing.

Tagged Swordfish # 2

Angler tagging a swordfish

Tag Ref.SkipperDate deployedLocationDate pop-upLocation
NSWSword#2Al McGlashan8/07/2021Mallacoota30/09/2021East of Batemans Bay

Satellite Track of Tagged Swordfish # 2

Movement track of Mallacoota swordfish

Depth and Temperature Profile

Dive profile of tagged swordfish from Mallcoota

The depth data shows that the fish carried out the typical pattern of diving deep during the day (to around 500 - 650m+) and rising near to the surface at night. There looks to have been a minor change to the behaviour around early to mid-September where the daytime dives don’t go as deep as normal (300 – 450m+) before the normal pattern of dives to 500m+ resumed.

The surface water temperature increased (from around 16 degrees C) as the fish moved north from Victorian waters up to NSW waters, with the surface temperature reaching over 20 degrees for a period of over week in early August. The swordfish appears to travel east from its tagging location and then north to a point directly east of southern Sydney before moving west towards the bottom of the continental slope and then tracking back south towards the border with Victoria before moving north east up to the point of pop-off, east and well offshore of the Batemans Bay area.

Tagged Swordfish # 3

Tagged broad bill swordfish

Tag Ref.SkipperDate deployedLocationDate pop-upLocation
NSWSword#3Al McGlashan24/07/2022Bermagui27/09/2022 (caught by longline vessel)Bass Canyon

Satellite Track of Tagged Swordfish


Depth and Temperature Profile

Time series of tagged swordfish

As with previous satellite tagged swordfish, the depth data shows that the fish carried out the typical pattern of diving deep during the day and rising near to the surface after sunset. It is believed that this is linked to the swords foraging for food in the Deep Scattering Layer (DSL). You can see that during the period coming up to the full moon on 12 August, the fish tends to remain slightly deeper at night - this is likely to be linked to the DSL sitting slightly lower during the period with the higher illumination from the full moon. The normal daytime diving depth appeared to vary from around 400 - 700m+ with some shallower and deeper dives over time.

On tagging, it appears that the fish moved steadily headed east for around 90 NM before moving in a general south westerly direction, over the Victorian border and tracking towards the entrance of Bass Canyon where it was caught by a longline vessel at the end of September. During that time the surface water surface ranged from around 18.5°C to around 14.5 °C with the deepest dives dropping the recorded temperature regularly down to 8 °C and below, with the lowest temperature being around 6.5 °C.