Paua catch-per-unit-effort from GPS dive-loggers

Presentation given at the International Abalone Symposium, Hobart, May 2012. The presentation describes work on using GPS dive loggers to estimate abundance of the New Zealand abalone, paua.

Transcript

1. P¯ aua catch-per-unit-effort from GPS dive-loggers Edward Abraham, Jeremy Cooper edward@dragonfly.co.nz International Abalone Symposium, Hobart, 9 May 2012
5. Outline 1 Old-fashioned management 2 Dive-loggers 3 P¯ aua abundance and CPUE 4 Fishdown experiment 5 Summary
6. Large areas P¯ aua statistical areas, within the P¯ aua 7 Management Area
7. Paper based reporting Jason Baker does his homework
8. Stock assessments P¯ aua 7 biomass, McKenzie & Smith (2009)
9. Towards responsive, informed management
10. Dive-loggers Boat and turtle units, made by Zebratech (NZ)
11. Dive profile Twenty minutes of free-diving for p¯ aua 40:00 45:00 50:00 55:00 00:00 −6 −4 −2 0 Time (minutes) Depth (m) qqqqqqqqqqqqqqqqqq qqqq q qqqqq q qqqqq qqqqq q qqqqqqqqqq qqqqq qqqq qqq qqq qq qqqqq q qq qqqqq qqqqqqqqqqqqqqqqqq qqq qqqqq qqqqq qqqq qqq qq q qqq qqq qqq q qq qqq q qq
12. Dive depth Free-diving has its limits q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q 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q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q qq q q q q q q qq q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q 0 50 100 150 200 250 −10 −8 −6 −4 −2 0 Time underwater (s) Depth (m)
14. P¯ aua abundance and CPUE
15. Holling disk equation Relating abundance to harvest rate 0 2 4 6 8 10 0 20 40 60 80 100 Abundance Harvest rate Buzz Holling, photo CC-BY Simon Fraser University Student mathematical biology lab, Utah University
16. Abundance and logger CPUE Schematic Raw index:
17. Abundance and logger CPUE Schematic Corrected for differences between sites and divers:
18. Measures of Fishing effort • Time underwater • Total time fishing (swimming on surface, and underwater) • Area fished
19. Fishdown experiment Determine relationships between logger CPUE and absolute abundance 1 A diver or team fishes a reef for a day, recording logger data and catch 2 Wait some time (weeks) 3 Repeat fishing on the same reef, with the same divers 4 Continue until there are no legal size p¯ aua left
20. Fighting Bay
21. Fighting Bay Closed to fishing since 1996
23. Pre-fishdown survey P¯ aua length and habitat recorded on underwater calipers (Zebratech, NZ)
24. Survey results P¯ aua patchy, in shallow water Shallow Deep
25. Site choice Small section (around 400 m long) chosen for the fishdown
26. Experiment catch 8 tonnes Fighting Bay, 500 kg Boat Harbour 2011−12−14 2011−12−15 2012−01−12 2012−02−01 2012−02−23 Boat harbour Fighting Bay Catch (kg) 0 500 1000 1500 2000
27. CPUE Similar CPUE by the end of the experiment 2011−12−14 2011−12−15 2012−01−12 2012−02−01 2012−02−23 Boat harbour Fighting Bay Catch per hour underwater (kg/h) 0 200 400 600 800 1000
30. Abundance and CPUE CPUE defined as amount harvested over time underwater q q q q q q q q q q q 0 2000 4000 6000 8000 0 500 1000 1500 Weight (kg) CPUE (kg/h) q q q q Fighting Bay Boat Harbour
31. Diver catch Diver J consistently higher than the other divers 2011−12−14 2011−12−15 2012−01−12 2012−02−01 2012−02−23 J B C G Catch (kg) 0 200 400 600 800
32. Abundance and CPUE by diver Fighting Bay CPUE calculated separately for each diver 0 2000 4000 6000 8000 0 500 1000 1500 Weight (kg) CPUE (kg/h) q q q q q q q q q q q q q q q J B C G q q q q q q q q q q q q q q J B C G q q q q q q q q q q q q J B C G q q q q q q q q J B C G
33. Next steps Ongoing work • Apply CPUE metric to the non-experimental data • Develop grooming procedures for the diver GPS data • Area-based CPUE analysis • Statistical analysis (CPUE standardisation) • Make the analysis available to industry participants
34. Thanks! Special thanks to Dave and Sandra Baker and the First Light team; to Julie Hills and the MPI people who pushed for the fishdown to go ahead; to Nigel Keeley and Ellie Watts from Cawthron for the site survey; and to Transpower and the SeaPatroller for letting us in to Fighting Bay.