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Hella Marine - NZ - 728 - July

SARDI fisheries scientists deploy satellite tags on shortfin makos

by Dept of Enviroment and Primary Industries on 25 Apr 2013
Shortfin mako Jarrod Day
The Southern Shark Ecology Group from SARDI Aquatic Sciences in South Australia is currently utilising two types of satellite tags to answer the following research questions:

1. How long do shortfin makos remain in Victorian waters?
2. Are they linked to other shortfin mako populations via their movements?
3. Are shortfin makos in Victoria vulnerable to fisheries in other regions?

This project is funded by Victorian recreational fishing licence fees and is supported by VRFish and several Victorian gamefishing clubs.

Fisheries scientist from SARDI recently deployed four satellite tags on shortfin makos off Portland. Three additional satellite tags will be deployed in 2013.

Prior to this project, other satellite tags were deployed in the Central Great Australian Bight and off SE South Australia to investigate the migration patterns and critical habitats of shortfin makos.

Satellite and conventional gamefish tagging data has shown there is mixing of the shortfin mako population between the Southern, Indian and Pacific Oceans.

What do the satellite tags deployed on shortfin makos look like?

In Victoria, two types of tags are being deployed. The first type is a slim black SIRTRACK™ tag. These small tags (~40 mm long and 37 g) are fixed to the trailing edge of the first dorsal fin. They are being used to tag shortfin makos of 1-2 m.

The second larger tag type is circular and cast in clear resin. These larger tags are attached to the middle of the first dorsal fin. They are being used on shortfin makos >2 m. They have a blue Wildlife Computers™ label embedded inside them with the contact details for the manufacturer.

These large
r tags store dive and temperature information so it is important to the study that they are returned if the shark is captured and killed.

Four other tag types have been used in previous projects on shortfin makos off southern Australia. It is possible that fishers may also capture a shortfin mako that has retained one of these tags.

What should we do if we catch a shortfin mako that has any type of satellite tag attached to it?

Ultimately, it is the choice of the fisher as to whether they wish to follow the following options during two different capture scenarios:

Scenario 1: A shortfin mako is hooked and the fisher identifies that the shark has a satellite tag attached to its dorsal fin. The shark is jaw hooked, is in lively, healthy condition and has no visible physical injuries other than the hook wound in the corner of its mouth. The fisher makes the decision to release the shark.

Preferred option: The leader is cut as close as possible to the mouth of the shark, or the hook is removed with the shark in the water (if the decision is made that it can be done without compromising the safety of anyone on-board i.e. adequate equipment is on-board such as wiring gloves, wire cutters and bolt-cutters). A clear photo of the shark and tag is taken. The fisher can then contact Dr Paul Rogers at SARDImage courtest of Paul RogersI to report the location and details of the capture on 0400 536150, 08 82075487; email: paul.rogers@sa.gov.au. If Paul is not available please contact Mr Paul Irvine on 0404 837211.

Scenario 2: A shortfin mako is hooked and the fisher identifies that the shark has a satellite tag attached to the dorsal fin. The shark is hooked in the gut or throat, is bleeding from the mouth and/or gills and the angler makes the decision to land it.

Preferred option: The fisher contacts Dr Paul Rogers as soon as possible to discuss the capture and recovery of the satellite tag. If the fisher is within phone range and enough people are on-board to manage the situation safely, this can be done while the shortfin mako is on the leader.

Is it illegal to capture and kill a shortfin mako that has a satellite tag?

No, it is currently legal for recreational fishers to target, capture and take shortfin makos regardless of whether they have been satellite tagged. However, by reporting the capture of a tagged mako, the fisher is providing valuable information for our scientific study. If the tag is recovered it can be used to tag another shark.

Can I follow the tagged shortfin makos online?

Yes, the satellite tagged makos can be followed online on the Wildlifetracking website.

Where can I get an update about shortfin mako research in Australia?

An article about recent shortfin mako research is to be published in the April 2013 edition of Bluewater Boats and Sportfishing magazine. This information will also be summarised soon on the Southern Shark Ecology Group website.



http://www.dpi.vic.gov.au/

 

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