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A. Williams, M. Green, K. Graham, J. Upston, F. Althaus, B. Barker Industry partners: Whan and Boxsall Pty Ltd, Fortuna Seafoods Pty Ltd SESSF RAG Environment.

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Presentation on theme: "A. Williams, M. Green, K. Graham, J. Upston, F. Althaus, B. Barker Industry partners: Whan and Boxsall Pty Ltd, Fortuna Seafoods Pty Ltd SESSF RAG Environment."— Presentation transcript:

1 A. Williams, M. Green, K. Graham, J. Upston, F. Althaus, B. Barker Industry partners: Whan and Boxsall Pty Ltd, Fortuna Seafoods Pty Ltd SESSF RAG Environment Meeting - August 2012 MARINE AND ATMOSPHERIC RESEARCH Determining the distribution of gulper sharks on Australia’s eastern seamount chain and the selectivity of Minor Line fishing in regard to seamounts populations of Blue-eye Trevalla and Harrisson’s Dogfish – preliminary results

2 Background for project 2 | Harrisson’s Dogfish (and other deepsea dogfish) nominated for listing under EPBC Act in 2005 Extensive east coast sampling using Auto Longline vessel Diana in 2009 identifies Taupo Seamount off NSW as one potential refuge for Harrisson’s Dogfish Taupo and Barcoo seamounts closed to all fishing in June 2010 during Stage 1 implementation of AFMA’s Upper Slope Dogfish Management Plan Fishing selectivity / Minor Line / Seamounts / Gulper sharks

3 Rationale for project Proposition 1: The ‘Minor Line’ method of fishing would be able to catch Blue-eye Trevalla on Taupo and Barcoo, and avoid Harrisson’s Dogfish during normal fishing operations Proposition 2: Other seamounts in the Tasmantid Seamounts Chain may also be refuges for Harrisson’s Dogfish 3 | Fishing selectivity / Minor Line / Seamounts / Gulper sharks Photos courtesy Jo Rowley,

4 Objectives 1.Establish whether Harrisson’s Dogfish can be avoided during normal Minor Line fishing operations to harvest Blue-eye Trevalla on offshore seamounts. 2.Identify environmental factors such as depth and time of day, together with gear/ method characteristics, that determine why the species of interest are captured or avoided by Minor Line fishing. 3.Determine the distribution of Harrisson's Dogfish on the east Australian seamount chain. 4.Provide an estimate of relative abundance of Harrisson's Dogfish on inhabited seamounts. Fishing selectivity / Minor Line / Seamounts / Gulper sharks 4 |

5 Study area 5 | Will be done last 7/10 trips 1 trip Contours: 200m, 1000m, 2000m depth. Fishing selectivity / Minor Line / Seamounts / Gulper sharks

6 Seamount morphology summary 6 | Fishing selectivity / Minor Line / Seamounts / Gulper sharks SeamountDepth range (m) Area (km 2 ) % Fraser Peak depth ~400 m Total area 162 km 2 < – – – Recorder Peak depth ~500 m Total area 469km 2 < – – – SeamountDepth range (m) Area (km 2 ) % Queensland Peak depth ~300 m Total area 806 km 2 < – – – Britannia Peak depth ~200 m Total area 1981 km 2 <2000.7<1 200– – – SeamountDepth range (m) Area (km 2 ) % Derwent Hunter Peak depth ~400 m Total area 1291 km 2 < – – – Barcoo Peak depth ~300 m Total area 395 km 2 < – – – Taupo Peak depth ~200 m Total area 1360 km 2 < – – – Smallest TA Smallest ‘fishing’ depths Large ‘fishing’ depths

7 Hi-resolution swath map of Barcoo 7 | Fishing selectivity / Minor Line / Seamounts / Gulper sharks

8 Hi-resolution swath map of Taupo (partial) 8 | Fishing selectivity / Minor Line / Seamounts / Gulper sharks

9 Minor Line fishing equipment 9 | Vessel nameClaudarahNelson Bay Home PortTuncurry (NSW)Mooloolaba (QLD) OwnersWhan and Boxsell Pty LtdFortuna Fishing Pty Ltd Length / breadth (metres)18.3 / / 4.0 Tonnage4020 Main engine (KW)4422 x 246 Four hydraulic reels on each boat in same relative position – three used for each drop 1500 m of Dyneema® line on reel 18 hooks per line (54 per drop) weighted 5–10 kg Lines tended by hand, hauled when experienced crew feel several fish have been hooked Hooks typically 5–10 minutes on bottom while boat drifts Normal fishing only during day Fishing selectivity / Minor Line / Seamounts / Gulper sharks Photos courtesy Jo Rowley,

10 Selectivity of Minor Line – test development 10 | Hypothesis - “a bycatch of gulper shark can be avoided during ‘standard’ targeted commercial Blue-eye fishing on the Taupo and Barcoo Seamounts using Minor Lines”. Test 1: Gulpers are avoided because standard (daytime, mid-depth) fishing avoids ‘gulper habitat’ [gulpers occupy deep depths during the day and mid- depths only at night] Test 2: Gulpers are avoided because the standard blue eye fishing method [gear/practice/blue-eye schools targeted] selects strongly for blue eye Test 3: Gulpers are avoided because they are not present in sufficient abundance on the seamounts to be caught with Minor Line fishing [e.g. soak time too short, hooks too few, gulpers too few] Fishing selectivity / Minor Line / Seamounts / Gulper sharks

11 Selectivity of Minor Line – experimental design 11 | Fishing selectivity / Minor Line / Seamounts / Gulper sharks Dropline design 54 hooks per line 1–4 hour soak time Mid depth at night Deep depth at day

12 Results of selectivity testing - preliminary 12 | BarcooTaupo Drop line Minor line Drop line Minor line Non-target hooks retrieved Gulpers caught1511 ratio1/741/2861/142 1/693 Target hooks retrieved Gulpers caught 0 2 ratio 1/1909 “Target” means fishing signs and structure seen on sounder to try and catch Blue-eye Fishing selectivity / Minor Line / Seamounts / Gulper sharks

13 Distribution and major catch composition 13 | Fraser (n=41; m) Recorder (n=7; m) Queensland (n=17, m)Britannia (n=31; m) Taupo (n=25; m) Barcoo (n=46; m) Blue-eye Trevalla Harrisson’s Dogfish Whitetail Spurdog (sthn) Whitetail Spurdog (nthn) Eigthbar Grouper Flame Snapper Spikey Spurdog (sthn) Longfin Gemfish Alfonsino Blacktail Spurdog Taupo and Barcoo data 3/10 trips Fishing selectivity / Minor Line / Seamounts / Gulper sharks

14 Relative abundance of Harrisson’s Dogfish 14 | SeamountsTotal hooks used Harrisson’s Dogfish Catch rate Per 1000 hooks Fraser Recorder Queensland Britannia Barcoo Taupo Fishing selectivity / Minor Line / Seamounts / Gulper sharks Photos courtesy Jo Rowley,

15 Conclusions – objectives 1 and 2 15 | 1.Establish whether Harrisson’s Dogfish can be avoided during normal Minor Line fishing operations to harvest Blue-eye Trevalla on offshore seamounts. 2.Identify environmental factors such as depth and time of day, together with gear/ method characteristics, that determine why the species of interest are captured or avoided by Minor Line fishing. The result of the tests on Taupo and Barcoo strongly support the ability of Minor Line fishing to avoid Harrisson’s Dogfish captures, provided the gear is set during the day and in less than 550 metres. Minor Line fishing has very short bottom times and the catch are removed by hand, both will result in better survival outcomes for shark species bycatch. Fishing selectivity / Minor Line / Seamounts / Gulper sharks

16 Conclusions – objectives 3 and 4 16 | 3.Determine the distribution of Harrisson's Dogfish on the east Australian seamount chain. 4.Provide an estimate of relative abundance of Harrisson's Dogfish on inhabited seamounts. Harrisson’s Dogfish are distributed on all the Seamounts sampled, however they appear to be very low in abundance at Fraser Seamount, the smallest in area and the most northern (possible species latitudinal limit). Queensland, Britannia and Recorder seamount have a relative abundance two orders of magnitude greater than on Fraser, Taupo and Barcoo. Derwent Hunter remains to be sampled. Fishing selectivity / Minor Line / Seamounts / Gulper sharks

17 MARINE AND ATMOSPHERIC RESEARCH / WEALTH FROM OCEANS Thank you Photos courtesy Jo Rowley,


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