Dataset: Seabird by-catch in longline fisheries


Metadata record for data from ASAC Project 2295
See the link below for public details on this project.

---- Public Summary from Project ----
Longline fisheries represent a serious threat to the survival of Southern Ocean albatrosses and petrels. During line setting operations seabirds become entangled with baited hooks and are drawn underwater and drown. In the past 10-20 years populations of some species have decreased at an alarming rate and some species are considered to be threatened with extinction. The Antarctic Divisions seabird by-catch program is attempting to minimise mortality in longline fisheries by a multi-faceted approach involving mitigation research on fishing vessels, research on seabirds and initiatives of a semi-political nature.

We chartered F/V Assassin for three days to trial a series of line weighting regimes under fishing conditions experienced in the east coast tuna fishery. Sink rates of lines with 52 combinations of swivel weight, bait type and bottom length were recorded.

In Mooloolaba they don't use leaded swivels. Therefore it is an unweighted snood.

Assassin TDR metadata.xls
indicate the factors tested in the experiment, and the order in which they were undertaken. The Tuncurry_order_of_sets.xls file is the order in which the snoods (numbered by regime code) were put out during each line set. Should be read in conjunction with the metadata file. The D1, D2, D3 numbers denote the end of a working day when we downloaded the data from the day's line sets (4 on day 1, 6 on day 2, 5 on day 3).

assassin summary means.xls
assassin summary seconds to depth for analysis.xls
Assassin_time_to_depth_graphs.xls are files summarising the sink rates.

The folder
contains all the raw time depth recorder files.

The fields in these datasets are:

Bait type YT - yellowtail, SM - slimy mackerel, SQ - squid, SA - Saury,
LYT - Live Yellow Tail, LSM - Live Slimy Mackerel, DYT - Dead Yellowtail,
DSM - Dead Slimy Mackerel, DSQ - Dead Squid, DSQ + light/Sau - Dead Squid plus lightstik/Saury, DSQ + light - Dead Squid plus lightstik

Bait life status (D - dead, L - live)

Swivel weight (grams)

Bottom length (metres)

Number (n)

Standard Deviation

Time to depth (seconds)

Light stik

Side (SB - Starboard, P - Port)



Regime (codes are the number of the snood (just a way to keep a track of the treatments))

Depth (metres)


Time Depth Recorder (number in each shot represent the individual time depth recorder number that was attached to the snood just near the hook)

Taken from the 2008-2009 Progress Report:
Progress against objectives:
We have consolidated two research streams for pelagic longline fisheries. One is to conduct "conventional" mitigation research, principally focusing on methods to expedite gear sink rates, and the other is to develop an underwater bait delivery system for tuna and swordfish gear. Both streams are dealt with below.

The conventional research focuses on operational aspects of gear, and at this stage does not involve seabird avoidance research (this will come later).

In the last 12 months I have a) completed a designed experiment on a chartered tuna vessel off Mooloolaba, Queensland, examining the effect of mainline tension (created by use of a line shooter) on the sink rate of baited hooks in the shallow depth ranges; b) a designed experiment in Coquimbo, Chile (as part of Birdlife Internationals Albatross Task Force) examining the effect on initial sink rates of the five branch line deployment methods used by tuna vessels in the southern hemisphere, and c) completed five weeks in Mooloolaba with a chartered fishing vessel and in collaboration with DeBrett's Seafoods and Amerro Engineering, on the R and D of the underwater setting machine.

Taken from the 2009/2010 Progress Report:

In the past 12 months research work has focused on:

a) the development of the underwater bait setting capsule,
b) the effects of propeller turbulence on the sink rates of baited tuna hooks,
c) the effect of improved line weighting on the catch rates of fish taxa.

We have made considerable progress with the underwater setting machine and are intending to complete a "proof-of-concept" experiment with the device in Uruguay this winter/spring. Project "b" was completed on two vessels (one in Chile and one in Australia, as opportunities arose) and a paper was submitted to the Seabird Bycatch Working Group meeting of ACAP in April 2010. Part "c" above was completed in January 2010 and has morphed into a second trial that may show more promise that the first. When that trial has been completed the work will be written up for publication.

Taken from the 2010/2011 Progress Report:

Public summary of the season progress:
Line weighting trials: A trial was completed on the effects of seabird friendly (fast sinking) tuna branch lines on the catch rates of target and non-target fish. No effects on catch rates were detected, clearing the way for test on effectiveness in deterring seabirds. Out of this trial grew a second study, involving weights placed at the hook. This trial probably has more promise than the first, and is currently underway in the Australian tuna fishery.

Underwater setter: A prototype version was tested experimentally off Uruguay in the spring of 2010. The experiment revealed the potential of underwater setting to near-eliminate seabird interactions. We are currently finessing the technology with a view to returning to Uruguay (with the finished product) in autumn 2012 to complete the experiment.

General Information