UCSD Scripps Institution of Oceanography SIOB 296 Bycatch

UCSD Scripps Institution of Oceanography – SIOB 296 Bycatch: Problems and Solutions Week 4, 27 Jan. 2020 Eric Gilman, Pelagic Ecosystems Research Group EGilman@utas. edu. au

Transitioning to Integrated Bycatch Management • Problems from bycatch & piecemeal mgmt. • Piecemeal bycatch guidance & mgmt. • Examples of bycatch mitigation cross-taxa conflicts o o o Gillnet pingers Temporal & spatial fishery closures Pelagic longline time-of-day & depth of fishing Pelagic longline hook shape Purse seine set type • Bycatch mitigation a driver of fisheries-induced evolution • Priority actions to transition to integrated bycatch mgmt. o Adapt ERAs of the effects of bycatch o Fill priority data gaps o Modernize FAO, RFMO & national bycatch frameworks

Problems Resulting from Bycatch • Reduced abundance of K-selected species • FIE, altering evolutionary characteristics and reducing the fitness of affected populations • Altered ecosystem structure and functions via trophic links • Socioeconomic problems • Regions where overexploited bycatch was important for income & food security • One fisheries bycatch is another’s target • Bycatch of juvenile commercially important species impairs recruitment

Current approach to bycatch management

Gillnet Acoustic Pingers • Reduce bycatch of some species of small cetaceans, seabirds • Alerts bottlenose dolphins and some pinnipeds ‘dinner bell’ effect increases local abundance, depredation and possibly bycatch

Temporal and Spatial Fishery Closures designed to reduce the bycatch of one species can displace fishing effort temporally and spatially, increasing the bycatch of other species, and increasing benthic community degradation

Time-of-day and depth of fishing Depth preferences for selected pelagic teleost and sharks from satellite tag data. Boxes are 25% and 75% quartiles, solid horizontal line is the median (50% quartile), dashed horizontal line is the mean, and bars represent 10 -90 th deciles. M=male, F=female (Musyl et al. , 2011).

Longline Hook Shape Effect of C vs. J-shaped hooks of same minimum width • Sharks and rays: higher catch rate, lower at-vessel mortality rate • Hard-shelled turtles: no effect on catch rate, lower proportion deeply hooked • Leatherback turtles: lower catch rate

Species/Group Bigeye tuna Area Catch Rate Associated Sets School Sets Atlantic Ocean Eastern Pacific Ocean Indian Ocean Western and central Pacific Ocean 14% of catch 28% of catch 4% of catch 5% of catch 1% of catch 6% of catch 1% of catch Yellowfin tuna Atlantic Ocean Eastern Pacific Ocean Indian Ocean Western and central Pacific Ocean 17% of catch 15% of catch 25% of catch 14% of catch 76% of catch 43% of catch 72% of catch 22% of catch Billfishes (mainly marlins, sailfish) Atlantic Ocean 46. 8 t / 1000 sets 1. 0 t / 1000 t landed tunas 1. 4 t / 1000 t landed tunas 22. 8 t / 1000 sets 0. 6 t / 1000 t landed tunas 0. 4 t / 1000 t landed tunas 41. 9 t / 1000 sets 0. 4 t / 1000 t landed tunas 0. 7 t / 1000 t landed tunas 11. 0 t / 1000 sets 0. 1 t / 1000 t landed tunas 0. 6 t / 1000 t landed tunas 29. 6 t / 1000 sets 4. 6 t / 1000 t landed tunas 2. 3 t / 1000 t landed tunas 121. 5 t / 1000 sets 5. 1 t / 1000 t landed tunas 1. 4 t / 1000 t landed tunas 5. 7 t / 1000 sets 0. 3 t / 1000 t landed tunas 35 no. / 1000 sets 0. 0 t / 1000 t landed tunas 5. 0 t / 1000 sets 0. 1 t / 1000 t landed tunas 2. 7 t / 1000 sets 8. 5 t /1000 t landed tunas 1. 2 t / 1000 t landed tunas 6. 5 t / 1000 sets 1. 1 t / 1000 t landed tunas 0. 6 t / 1000 t landed tunas 30. 3 t / 1000 sets 2. 2 t / 1000 t landed tunas 231 no. / 1000 sets 0. 2 t / 1000 t landed tunas 6. 4 t / 1000 sets 0. 7 t / 1000 t landed tunas 0. 2 t / 1000 t landed tunas Eastern Pacific Ocean Indian Ocean Western and central Pacific Ocean Sharks (mainly silky & oceanic whitetip) Rays (mainly manta and devil) Atlantic Ocean Eastern Pacific Ocean Indian Ocean Western and central Pacific Ocean Atlantic Ocean Sea turtles (mainly olive ridley, other hard- Eastern Pacific Ocean Indian Ocean shelled species) 74. 1 no. / 1000 sets 59. 8 no. / 1000 sets 1. 8 no. / 1000 sets 0. 7 no. / 1000 sets 15. 9 no. / 1000 sets 0. 8 no. / 1000 sets 2. 8 no. / 1000 in sets (drifting FADs) 6. 1 no. / 1000 associated sets and groups tuna purse seine fishery Western and of central Pacific species Ocean PURSE SEINE SET TYPE: Catch rates selected and school sets (Williams et al. , 2009; Amandè et al. , 2008, 2010; Dagorn et al. , 2013; Hall and Roman, 2013; ISSF, 2017 c). Associated sets are drifting FADs and logs unless specified otherwise.

Bycatch Mitigation Methods Drive Fisheries-Induced Evolution A bycatch mitigation method may inadvertently cause or strengthen a fishery’s intraspecific heritable trait-selective mortality, causing FIE. • Replacing longline wire with monofilament leaders (to reduce shark catch rate) might select for individuals w/ traits for poorer vision • Wider hook (to reduce hard shelled turtle catch rate) might select for larger individuals • MPA displaces effort temporally/spatially where narrower proportion of variations of a trait w/in a population occur

Transition to integrated bycatch assessment and management Narrow-scale (fisheryby-fishery), piecemeal (species-by-species) bycatch management Monitor, assess and manage effects of a single local fishery on single stocks and populations of market and bycatch species. Employ single stock assessment models and single taxa management measures. Narrow-scale, holistic (integrated) bycatch management Monitor, assess and manage effects of a single local fishery that accounts for the relative risks to affected populations from changes in absolute abundance and intrapopulation genetic diversity. Employ a holistic, integrated bycatch management measure. Nested-scale (across regional fisheries), holistic bycatch management Monitor, assess and manage effects across regional fisheries that accounts for the relative risks to affected populations from changes in absolute abundance and intrapopulation genetic diversity. Employ a holistic, integrated bycatch management measure. Nested-scale, full EBFM Monitor, assess and manage effects across regional fisheries across components of biodiversity within a defined ecosystem, including effects on species subject to bycatch, habitat effects and effects on trophic processes and functionally-linked systems. Employ multispecies and ecosystem-based models and harvest strategies. Marine EBM Cross-sectoral planning and management that holistically governs across marine pressures.

Priority actions to transition to integrated bycatch assessment and management • Adapt methods for ERAs of the effects of bycatch – Effects on genetic diversity – Relative risks across taxonomic groups – Ecosystem-level effects • Fill priority data gaps • Modernize guidance on bycatch mgmt. Allain et al. , 2015

Assess the relative risks from alternative bycatch mitigation measures across manifestations of biodiversity. Select bycatch mgmt. measures with intentional and acceptable tradeoffs to best meet objectives, when cross-taxa conflicts are unavoidable. Eric Gilman, Pelagic Ecosystems Research Group EGilman@utas. edu. au