Definition of Bycatch FIGURE 16 Definition 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 % Non-sustainable

2009 incidental dolphin mortality estimates, population abundance (Gerrodette et al., 2006), and relative population mortality. Stock Incidental mortality Population abundance Relative mortality (%) Offshore spotted dolphin Northern / eastern264911, Southern / western254911, Spinner dolphin Eastern288790, Whitebelly222711, Common dolphin Northern109449, Central30577,048 <0.01 Southern491,525,207 <0.01 Other dolphin232,802,300 <0.01 Total1,239

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

ISSF Meeting – Nov 09 - Sukarietta Discards by major types of fishery – FAO Kelleher Fishery discard (%) Shrimp trawl 62.3 Demersal finfish trawl 9.6 Tuna and HMS longline 28.5 Midwater (pelagic) trawl 3.4 Tuna purse seine 5.1 Mobile trap/pot 23.2 Dredge 28.3 Small pelagics purse seine 1.2 Demersal longline 7.5 Tuna pole and line 0.4

Expressing bycatch as the ecological cost of production Bycatch per ton of catch

All years ( ) BYCATCH per 1000 MT of tuna BYCATCH per 1000 MT of tunaSpecies Dolphin sets School sets FAD sets FAD sets OFFSHORE SPOTTED EASTERN SPINNER WHITEBELLY SPINNER COMMON DOLPHIN OTHER DOLPHIN SAILFISH BLACK MARLIN STRIPED MARLIN BLUE MARLIN MAHI MAHI , WAHOO RAINBOW RUNNER YELLOWTAIL OTHER SHARKS WHITETIP SHARK HAMMERHEAD SHARK UNID. SHARK MANTARAY STINGRAY SILKY SHARK UNID. TURTLE OLIVE RIDLEY GREEN/BLACK TURTLE

SpeciesDolphin sets Log sets OFFSHORE SPOTTED EASTERN SPINNER WHITEBELLY SPINNER COMMON DOLPHIN OTHER DOLPHIN SAILFISH BLACK MARLIN STRIPED MARLIN BLUE MARLIN Unid/OTHER BILLFISH OTHER BIG FISH MAHI 0.841, WAHOO RAINBOW RUNNER YELLOWTAIL TRIGGER FISH8.635, SILKY SHARK WHITETIP SHARK HAMMERHEAD SHARK MANTARAY STINGRAY OTHER SHARKS UNID. TURTLE OLIVE RIDLEY GREEN/BLACK TURTLE Bycatch to produce 1000 MT tuna Average

Sets on Fish Aggreg. Devices 1 dolphin rays 1.4 billfishes + 30 sharks large bony fishes sea turtles + 18 MT tunas Sets on Dolphins

How to compare species? How to compare species? Conservation status Conservation status Vulnerability Vulnerability Ecological “role” (keystone, structural) Ecological “role” (keystone, structural) Trophic level Trophic level A new proposal: A new proposal: Replacement cost to the ecosystem Replacement cost to the ecosystem…………………..

Pinocho Moby Dick Las imagenes forman nuestra cultura

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).

Mark – recapture Satellite tracking Catch curves Fishers interviews Strandings