Definition of Bycatch

FIGURE 16Definition of Bycatch

CAPTURE = CATCH + BYCATCH + RELEASE

Relative bycatch:

Bycatch/Abundance

Bycatch Sp A 50,000

Bycatch Sp B 80

Abundance Sp A 5,000,000 1% Sustainable

Abundance Sp B 800 10% Non-sustainable

2009 incidental dolphin mortality estimates, population 2009 incidental dolphin mortality estimates, population abundance (Gerrodette et al., 2006), and relative abundance (Gerrodette et al., 2006), and relative

population mortality.population mortality.

StockIncident

almortality

Population

abundance

Relative mortality

(%)

Offshore spotted dolphin

Northern / eastern 264 911,177 0.03

Southern / western 254 911,830 0.03

Spinner dolphin

Eastern 288 790,613 0.04

Whitebelly 222 711,883 0.03

Common dolphin

Northern 109 449,462 0.02

Central 30 577,048 <0.01

Southern 49 1,525,207 <0.01

Other dolphin 23 2,802,300 <0.01

Total 1,239

Efficiency in resource utilization

a) The complement of the bycatch rate is the Utilization rate (UR), the ratio of the production of the fishery to the biomass extracted from the system from all species:

Catch of a species (or group of species)UR = ------------------------------------------------------ Capture of a species (or group of species)

Bycatch rate (BR) = Bycatch/Capture

Utilization rate = 100 – BR = Catch/Capture

Estimated Total EPO totals - all set types

Year SetType Capture/set Disc./set%

Discard Disc. in EPO capture discard BR% UR%2007 Dolphin 12.5 0.0 0.1 226

School 14.8 0.3 1.9 1,774

Log 32.4 1.3 4.0 8,144 395,016 10,144 2.57 97.432008 Dolphin 15.4 0.0 0.2 418

School 21.1 0.5 2.4 3,022

Log 36.8 1.3 3.6 9,032 497,918 12,472 2.50 97.502009 Dolphin 16.9 0.0 0.1 331

School 15.5 0.2 1.5 1,184

Log 35.1 1.1 3.1 7,824 499,608 9,338 1.87 98.13Average Dolphin 18.2 0.1 0.5 975

All years School 17.4 0.5 2.7 2,3541993-2009 Log 42.1 4.0 9.6 20,363 468,322 23,692 5.06 94.94

Total MT capture, bycatch and bycatch ratios 3 main tuna species (YFT, SKJ, BET)

1993-09

0

20

40

60

80

100

120

140

160

93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09

MT

Tho

usan

ds

Years

Unassociated Sets

Discards

Retained Capture

050

100150200250300350400

93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09

MT T

hou

sand

s

Years

Floating Object Sets

Discards

Retained Capture

0

50

100

150

200

250

300

350

93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09

MT T

hous

and

s

Years

Dolphin Sets

Discard

Retained Capture

ISSF Meeting – 24-27 Nov 09 - SukariettaDiscards by major types of fishery – FAO Kelleher

Fishery discard (%) Shrimp trawl 62.3Demersal finfish trawl 9.6Tuna and HMS longline 28.5Midwater (pelagic) trawl 3.4

Tuna purse seine 5.1Tuna purse seine 5.1Mobile trap/pot 23.2Dredge 28.3Small pelagics purse seine 1.2Demersal longline 7.5Tuna pole and line 0.4

Expressing bycatch as the ecological cost of production

Bycatch per ton of catch

All years (1993-2009)All years (1993-2009)     BYCATCH per 1000 MT of tunaBYCATCH per 1000 MT of tuna

SpeciesSpeciesDolphin Dolphin

setssetsSchool School

setssets FAD setsFAD setsOFFSHORE SPOTTEDOFFSHORE SPOTTED 5.195.19 0.000.00 0.000.00EASTERN SPINNEREASTERN SPINNER 1.991.99 0.000.00 0.000.00WHITEBELLY SPINNERWHITEBELLY SPINNER 1.761.76 0.000.00 0.000.00COMMON DOLPHINCOMMON DOLPHIN 1.681.68 0.040.04 0.000.00OTHER DOLPHINOTHER DOLPHIN 0.720.72 0.050.05 0.010.01SAILFISHSAILFISH 1.781.78 3.903.90 0.180.18BLACK MARLINBLACK MARLIN 0.110.11 0.250.25 0.760.76STRIPED MARLINSTRIPED MARLIN 0.060.06 0.170.17 0.180.18BLUE MARLINBLUE MARLIN 0.040.04 0.150.15 0.780.78MAHI MAHIMAHI MAHI 0.840.84 53.9453.94 1,365.661,365.66WAHOOWAHOO 0.560.56 3.773.77 622.55622.55RAINBOW RUNNERRAINBOW RUNNER 0.060.06 13.6413.64 476.21476.21YELLOWTAILYELLOWTAIL 1.251.25 106.24106.24 116.59116.59OTHER SHARKSOTHER SHARKS 0.680.68 3.013.01 1.711.71WHITETIP SHARKWHITETIP SHARK 0.500.50 2.022.02 14.1014.10HAMMERHEAD SHARKHAMMERHEAD SHARK 0.330.33 2.492.49 5.715.71UNID. SHARKUNID. SHARK 3.573.57 4.234.23 11.0611.06MANTARAYMANTARAY 4.364.36 30.3630.36 0.540.54STINGRAYSTINGRAY 1.191.19 5.485.48 0.590.59SILKY SHARKSILKY SHARK 7.557.55 33.7233.72 96.5996.59UNID. TURTLEUNID. TURTLE 0.020.02 0.070.07 0.080.08OLIVE RIDLEYOLIVE RIDLEY 0.040.04 0.130.13 0.170.17GREEN/BLACK TURTLEGREEN/BLACK TURTLE 0.000.00 0.030.03 0.020.02

Species Dolphin sets Log setsOFFSHORE SPOTTED 5.19 0.00EASTERN SPINNER 1.99 0.00

WHITEBELLY SPINNER 1.76 0.00COMMON DOLPHIN 1.68 0.00

OTHER DOLPHIN 0.72 0.01SAILFISH 1.78 0.18

BLACK MARLIN 0.11 0.76STRIPED MARLIN 0.06 0.18

BLUE MARLIN 0.04 0.78Unid/OTHER BILLFISH 0.13 0.27

OTHER BIG FISH 0.11 30.78MAHI MAHI 0.84 1,365.66

WAHOO 0.56 622.55RAINBOW RUNNER 0.06 476.21

YELLOWTAIL 1.25 116.59TRIGGER FISH 8.63 5,957.57SILKY SHARK 7.55 96.59

WHITETIP SHARK 0.50 14.10HAMMERHEAD

SHARK 0.33 5.71MANTARAY 4.36 0.54STINGRAY 1.19 0.59

OTHER SHARKS 4.25 12.77UNID. TURTLE 0.02 0.08OLIVE RIDLEY 0.04 0.17

GREEN/BLACK TURTLE 0.00 0.02

Bycatch to produce 1000 MT tuna

Average 1993-2009

Sets on Fish Aggreg. Devices

1 dolphin +

0.3 rays

1.4 billfishes +

30 sharks +

803 large bony fishes +

0.05 sea turtles +

18 MT tunas

Sets on Dolphins

How to compare species?How to compare species?

Conservation statusConservation status VulnerabilityVulnerability Ecological “role” (keystone, structural)Ecological “role” (keystone, structural) Trophic levelTrophic level A new proposal: A new proposal: Replacement cost to the ecosystemReplacement cost to the ecosystem

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Bycatch/catch ratios (B/C) such as number or tonnage of a species per 1000 MT of tuna retained (Catch) are useful to link impact with production, and therefore to assess the relative ecological costs of different gears or set types.

Areas and periods with high B/C ratios are good candidates for spatial or temporal closures, using Bycatch Reduction Curves (Hall, 1996).

150°

150°

70°

70°

80°

80°

90°

90°

100°

100°

110°

110°

120°

120°

130°

130°

140°

140°

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20° 20°

10° 10°

0° 0°

10° 10°

20° 20°

Ratio: Num. silky sharks/Tuna catch MT (FOB sets)

Carcharhinus falciformis

> 0 - 0.09

0.09 - 0.9

0.9 - 3.3

3.3 - 10.6

Years: 2006 - 2010 (>=10 sets)

150°

150°

70°

70°

80°

80°

90°

90°

100°

100°

110°

110°

120°

120°

130°

130°

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140°

30° 30°

20° 20°

10° 10°

0° 0°

10° 10°

20° 20°

Ratio: Num. blue marlins/Tuna catch MT (FOB sets)

Makaira nigricans

> 0 - 0.09

0.09 - 0.1

Years: 2006 - 2010 (>=10 sets)

Mark – recapture Satellite trackingCatch curvesFishers interviewsStrandings