Post-Hooking Survivability of Released Blue Shark from

Longline Gear in Hawaii as Identified with PSATs

Mike Musyl – Univ. Hawaii/Jimar/PFRP

Rich Brill – VIMS/NMFS

Keith Bigelow, NMFS Honolulu Laboratory

Mahalos:

Mike LaursYonat SwimmerDave ItanoChristina LarsenNuno FragosoTom KazamaDan CurranPaul HoweyRoger Hill & Melinda BraunJohn SibertKirsten Fritches & Eric WarrantLianne MaillouxCrew & Officers of RV Townsend Cromwell

PSATs

fishery independent- you don’t need to get them physically back

Records pressure (depth) and temperature every hour

Archived data is transmitted to ARGOS satellites and then sent to user

Data throughput of about 250 consecutive days with depth/temp readings(or every other day for 500 days)

PSAT will release and transmit in the following ways--

1) experiences no significant pressure change for 4 consecutive days

2) reaches a depth of about 1200 m (tag rated to about 2000m)

3) reaches the pre-programmed pop-off date

Geolocations estimated onboard the PSAT by changes in ambient light level -

i.e. estimates of dawn/dusk provide latitude (from day length) & longitude (from local noon vs. GMT noon)

Pop-off location by ARGOS Doppler Shift

ongoing double tagging studies to provide error estimates of light-based geolocations from PSATs (i.e. PSAT affixed to GPS drifter buoys)

The range of archival & PSAT, and conventional tags

Uses of Pop-up satellite archival tags (PSATs)

1). Chronicle vertical and horizontal movement patterns and local distribution

2). Evaluate survivability of released fish

3). Provide data that will allow further refinement of catch models based on vertical behavior and environmental conditions (e.g. Bigelow et al. 2002)

4). Identify spawning seasons and locations

Blue shark Prionace glauca

Top predator in marine ecosystem

Concerns about fisheries interactions*By-catch & finning

Life history characteristics of most shark species make them ideal for overexploitation

Post-hooking Survivability of sharks

two “Prong” Approach:

1). With PSATs, investigate post-hooking mortality by examination of vertical swimming patterns

2). Investigating biochemical correlates of delayed mortality – Moyes, Musyl, & Brill studies (see July/Sept. ’02 PFRP newsletter for details)

Also…

Using PSATs to determine correlation between vertical behavior and catch

rates

--important in the context of bycatchreduction and fisheries interactions

1 5 61 5 81 6 01 6 21 6 41 6 61 6 8

Latit

ude

Nor

th

1 2

1 4

1 6

1 8

2 0

2 2

2 4

2 6

2 8

3 0

3 2 Tagged 8 blue shark8 swordfish1 yellowfin

1 blue shark

4 blue shark1 oceanic white-tip1 yellowfin

1 blue shark

Tagging Operations in March/April2001 aboard RV Townsend Cromwell

15.000

20.000

25.000

30.000

35.000

40.000

145.000150.000155.000160.000165.000170.000175.000180.000Longitude (W)

La

titu

de

(N

)

17 Blue sharks

3 makos

PSAT Tagging Operations 2002

2 oceanic white-tips6 bigeye threshersharks

Taking blood sample for biochemical study

results are based on data from:8 females and 2 males representing 731 days

In 2002 operations, 10 males & 7 females were tagged to help even sex ratios

Results (blue sharks)

10 of 14 PSATs reported for a 71% “batting average”

Date Dep. Sex Popdate FL (cm) Days-at-liberty Mortality?30-Mar-01 female 3 mos. 170 1 NO5-Apr-01 female 6 mos. 35 NO2-Apr-01 female 6 mos. 170 non-reporting5-Apr-01 male 13 mos. 204 26 NO

10-Apr-01 male 13 mos. 165 non-reporting10-Apr-01 female 13 mos. 160 non-reporting11-Apr-01 male 13 mos. 173 5 YES11-Apr-01 female 13 mos. 165 102 NO5-Apr-01 female 13 mos. non-reporting3-Apr-01 female 13 mos. 165 51 NO3-Apr-01 female 13 mos. 173 69 NO2-Apr-01 female 13 mos. 180 143 NO5-Apr-01 female 13 mos. 150 238 NO

14-Apr-01 female 13 mos. 160 61 NO

Total 731 days of data

Blue Shark Female#2

0

100

200

300

400

500

35 Day trace

Dep

th(m

)

Blue Shark Female #2, 2 days

050

100150200250300350400

12:00:00 AM 12:00:00 PM 12:00:00 AM 12:00:00 PM 12:00:00 AM

GMT Time

Dept

h (m

)

DawnDuskDusk Dawn

Blue Shark Male #1

050

100150200250300350400

26 day trace

Dep

th (

m)

Blue Shark Male #1, 2 days

050

100150200250300350400

12:00:00 AM 12:00:00 PM 12:00:00 AM 12:00:00 PM 12:00:00 AM

GMT

Dep

th (m

)

0

5

10

15

20

25

Tem

p (C

)

Daytime Depth Distribution

05

1015202530

0

60

12

0

18

0

24

0

30

0

36

0

42

0

48

0

54

0

60

0

66

0

72

0

Depth (m)

% T

ime Males

Females

80% time spent at < 180m

Nighttime Depth Distribution

0

10

20

30

40

500

40

80

120

160

200

240

280

320

360

400

440

480

Depth (m)

% T

ime

Females

Males

80% time at < 140 m

Daytime Temp. Distribution

010203040506070

8 10 12 14 16 18 20 22 24 26

Temp (C)

% T

ime Males

Females

80% time between 16-25 C

Nighttime Temp. Distribution

0

10

2030

40

50

8 10 12 14 16 18 20 22 24 26

Temp (C)

% T

ime

Females

Males

90% time between 16-25 C

Following analyses based on >5500 blue sharks captured from 319 longline setswith TDRs (temperature depth recorders) attached to longlines from Feb 96-Feb 97

Examining vertical dive behaviour and catch rates

Day depth (m) r=0.70,P<<0.001

0

5

10

15

20

25

300 80 160

240

320

400

Depth (m)

% T

ime

at D

epth

0

10

20

30

40

50

CP

UE

- T

DR

Night depth (m)r=0.54, P<<0.001

0

5

10

15

20

250 80 160

240

320

400

Depth (m)

% T

ime

at D

epth

020406080100120140

CP

UE

- T

DR

Similar PSAT/catch-at-depth analyses will be performed on:Swordfish

Blue marlin

Bigeye tuna

Yellowfin tuna

Oceanic white-tip sharks

Bigeye thresher sharks

Mako sharks

Pelagic Sea Turtles – loggerhead,

Olive Ridley

(Musyl & Swimmer, in prep.)

All tags shed before their pre-programmed pop-off date

1). Mortality- one confirmed2). Nuptial bites- yes3). RD1500 failure- no4). Tether problem -no 5). PSAT failure?

Blue Shark Male#2

0

200

400

600

800

1000

1200

5 day trace

Depth

(m

)

0

5

10

15

20

25

30

Tem

p (

C)

Tag initiates Release at about 1200m

Starts transmittingAt surface to ARGOS

Shark Mortality

Nuptial bites

Tag shedding can be probably ruled out in the short term

This tag/tether was out for 41 days—No obvious abrasions or cuts caused by dermal denticles

Harness consists of:270# fluorocarbon lineStainless steel thimblesBraided stainless steel wire encased in heavy gauge tubing

Breaking strength of eyelet on tag is 120#

Blue Shark Movements

Day/Night Depth Distribution

05

1015202530

0

60

120

180

240

300

360

420

480

540

600

660

720

Depth (m)

% T

ime Day

Night

Day/Night Temp. Distribution

05

1015202530

8 10 12 14 16 18 20 22 24 26

Temp (C)

% T

ime

Day

nitetemps