HAL Id: hal-01927071
https://hal.archives-ouvertes.fr/hal-01927071
Submitted on 22 Nov 2018
HAL is a multi-disciplinary open access
archive for the deposit and dissemination of
sci-entific research documents, whether they are
pub-lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d’enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.
possibility into reality
François Poisson, Francisco Abascal Crespo, Jim R. Ellis, Pierre Chavance,
Bach Pascal, Miguel. N. Santos, Bernard Séret, Maria Korta, Rui Coelho,
Javier Ariz, et al.
To cite this version:
François Poisson, Francisco Abascal Crespo, Jim R. Ellis, Pierre Chavance, Bach Pascal, et al..
Techni-cal mitigation measures for sharks and rays in fisheries for tuna and tuna-like species: turning
possibil-ity into realpossibil-ity. Aquatic Living Resources, EDP Sciences, 2016, 29 (4), pp.402. �10.1051/alr/2016030�.
�hal-01927071�
Technical mitigation measures for sharks and rays in fisheries
for tuna and tuna-like species: turning possibility into reality
François Poisson
1,a, Francisco Abascal Crespo
2,8, Jim R. Ellis
3, Pierre Chavance
4, Bach Pascal
4,
Miguel. N. Santos
5, Bernard Séret
6, Maria Korta
7, Rui Coelho
8, Javier Ariz
2and Hilario Murua
71 Institut Français de Recherche pour l’Exploitation de la Mer (Ifremer), UMR Marbec, CS 30171, Avenue Jean Monnet, 34203 Sète Cedex,
France
2 Instituto Español de Oceanografía, PO Box 1373, 38180 Santa Cruz de Tenerife, Spain
3 Centre for Environment, Fisheries and Aquaculture Science (CEFAS), Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk, NR33 0HT,
UK
4 Institut de Recherche pour le Développement (IRD), UMR Marbec, CS 30171, Avenue Jean Monnet, 34203 Sète Cedex, France
5 ICCAT Secretariat, Calle Corazón de Maria 8, 6 planta, 28002 Madrid, Spain
6 Institut de Recherche pour le Développement (IRD), UMR 212, Muséum national d’Histoire Naturelle Département Systématique
et Evolution, CP 51, 55, rue Buffon, 75231 Paris Cedex 05, France
7 AZTI, Herrera Kaia, Portualde z/g, 20110 Pasaia (Gipuzkoa), Spain
8 Instituto Português do Mar e da Atmosfera (IPMA), Avenida 5 de Outubro s/n, 8700-305 Olhão, Portugal
Received 25 February 2016; Accepted 5 October 2016
Abstract – Tuna fisheries have been identified as one of the major threats to populations of other marine vertebrates, including sea turtles, sharks, seabirds and marine mammals. The development of technical mitigation measures (MM) in fisheries is part of the code of conduct for responsible fisheries. An in-depth analysis of the available literature regard-ing bycatch mitigation in tuna fisheries with special reference to elasmobranchs was undertaken. Studies highlightregard-ing promising MMs were reviewed for four tuna fisheries (longline, purse seine, driftnets and gillnet, and rod and line – in-cluding recreational fisheries). The advantages and disadvantages of different MMs are discussed and assessed based on current scientific knowledge. Current management measures for sharks and rays in tuna Regional Fishery Management Organizations (t-RFMOs) are presented. A review of relevant studies examining at-vessel and postrelease mortality of elasmobranch bycatch is provided. This review aims to help fisheries managers identify pragmatic solutions to reduce mortality on pelagic elasmobranchs (and other higher vertebrates) whilst minimizing impacts on catches of target tuna species. Recent research efforts have identified several effective MMs that, if endorsed by t-RFMOs, could reduce elas-mobranchs mortality rate in international tropical purse seine tuna fisheries. In the case of longline fisheries, the number of operational effective MMs is very limited. Fisheries deploying driftnets in pelagic ecosystems are suspected to have a high elasmobranchs bycatch and their discard survival is uncertain, but no effective MMs have been field validated for these fisheries. The precautionary bans of such gear by the EU and by some t-RFMOs seem therefore appropriate. Recreational tuna fisheries should be accompanied by science-based support to reduce potential negative impacts on shark populations. Priorities for research and management are identified and discussed.
Keywords: Mitigation/ elasmobranch / bycatch / pelagic / mortality / tuna regional fishery management organizations
1 Introduction
Global fishing effort was roughly constant from 1950 to 1970, but increased steadily in subsequent decades (Anticamara et al. 2011). In 2005, global discards were es-timated at 6.8 million tonnes (mt) for 78.4 mt total reported landings: a global discard rate of 8% (Kelleher2005). Tuna and tuna-like species are of great importance as a global food resource and are of major economic value. Their reported
a Corresponding author:francois.poisson@ifremer.fr
global landings have increased continuously from <0.6 mt in 1950 to 7 mt in 2010 (FAO2014). Bycatch in tuna fisheries is the primary source of fishing mortality of some marine species (Bellido et al.2011), and tuna fisheries have been identified as one of the major threats to populations of various marine ver-tebrates, including marine turtles (Lewison et al.2004; Baez et al.2013; Roe et al.2014), sharks (Gilman et al.2007; Huang
2011), seabirds (Croxall et al.2012; Lewison et al.2012) and marine mammals (Forney et al.2011; Macías et al.2012).
the world are managed under the auspices of various tuna Regional Fishery Management Organizations (hereafter re-ferred to as t-RFMOs). Historically, t-RFMOs did not ad-dress bycatch issues, and only limited management actions were introduced. In recent years, however, t-RFMOs have in-cluded bycatch issues in their mandate and established work-ing groups on bycatch and ecosystems to better address by-catch (Gilman et al.2014). Options for technical mitigation measures (MMs) and bycatch reduction research have been central to these discussions, with several novel initiatives developed and many on-going studies (e.g., Kelleher 2005; Soykan et al. 2008; Gilman 2011). Some of these initia-tives have been developed against a background of increased global efforts by environmental non-governmental organiza-tions (ENGOs) to encourage innovative MMs (e.g., Bazilchuk
2005).
The development of MMs in fisheries as a part of respon-sible fisheries was first introduced in the 1982 Law of the Sea Convention (United Nations 1982), and addressed further in the subsequent Code of Conduct for Responsible Fisheries (FAO1995). Various national and international projects have investigated potential MMs to reduce negative impacts of tuna fisheries on bycatch taxa, which have helped t-RFMOs adopt-ing bycatch reduction management measures to either protect particular taxa of conservation concern or to regulate a partic-ular fishery.
Information on MMs has been collated in a variety of initiatives. The Western and Central Pacific Fisheries Commission (WCPFC) maintains the “Bycatch Mitigation Information System” (BMIS), a database that provides the latest information on the mitigation and management of in-cidental bycatch taken by fisheries targeting highly migra-tory species (http://www.wcpfc.int/bmis; accessed October 2015). This information is also of relevance to similar oceanic fisheries elsewhere in the world. The development of the BMIS was part of joint t-RFMO efforts that were facilitated under the Kobe III process (Fitzsimmons and Bunce 2013). Similarly, the New England Aquarium main-tains a database of references and summaries from by-catch reduction studies, as well as descriptions of byby-catch MMs (Consortium for Wildlife Bycatch Reduction’s web-site:http://www.bycatch.org; accessed October 2015) and the International Sea Food Foundation (ISSF) maintains a website with an index to t-RFMO measures (http://iss-foundation.org/
rfmo-resolution-database; accessed October 2015). These
ini-tiatives list and describe recent developments addressing by-catch issues, which can be shared with fisheries managers, sci-entists, fishers and the public.
Whilst initial research on MMs focused on “charismatic megafauna” (marine mammals, sea turtles and seabirds), elas-mobranchs (sharks and rays) have become of increased scien-tific, public and political concern since the 1990s. However, there are differences in the efficiency between MMs suggested to reduce impacts on elasmobranchs, which in some cases have been adopted by some countries and/or fishing entities.
Several reviews of mitigations measures in tuna longline and purse seine fisheries have been published (Gilman2011; Clarke et al.2014; Hall and Roman2013). A meta-analysis of
MMs in longline fisheries (Favaro and Côté2015). However, none of them includes a qualitative ranking system to assess the performance of the MMs. Here, a comprehensive review of existing MMs for several fisheries and a qualitative assess-ment of their success in terms of reducing bycatch (or dead discards) of elasmobranchs is provided, with their advantages and disadvantages assessed using defined criteria. This study takes a global view and the potential impacts of MMs on target species, other bycatch groups and the environment are consid-ered as well as current management measures for sharks and rays in t-RFMOs. For effective management measures to be implemented, it is crucial to have appropriate estimates of both at-vessel and postrelease survival rates for relevant species, as this determines the efficacy of MMs (Carruthers et al. 2009). Therefore, an in-depth analysis of the current bycatch miti-gation and management literature, as well as discard survival studies was undertaken, with recent innovations highlighted and important data gaps identified.
2 Material and methods
2.1 Fisheries
Four main fisheries for tuna and tuna-like species were considered; (1) longline fisheries (surface and deep-sets), (2) purse seine fisheries, (3) driftnets/gillnets, and (4) rod and line fisheries (typically recreational).
2.2 Web sites and literature reviews
The websites of the five main t-RFMOs (Inter-American Tropical Tuna Commission (IATTC), International Commission for the Conservation of Atlantic Tunas (ICCAT), Indian Ocean Tuna Commission (IOTC), Western and Central Pacific Fisheries Commission (WCPFC), and the Commission for the Conservation of Southern Bluefin Tuna (CCSBT) were consulted to summarize all relevant recommendations and resolutions that have been adopted for elasmobranch conservation and management.
Advantages and disadvantages of generic MMs (suitable for all fishing gears) were then identified from the litera-ture. Published literature on elasmobranch bycatch and MMs for fisheries targeting tuna, tuna-like species and/or sharks was reviewed for the four gear groups. Literature sources were identified by searching Bycatch Mitigation Information System (BMIS), ISI Web of Knowledge, the data base of the Consortium for Wildlife Bycatch Reduction and working doc-uments submitted to relevant t-RFMO working groups.
Publications examining at-vessel (“at-haul back” or “hook-ing”) and postrelease survival were identified based on library and electronic database searches using relevant key words (mortality, survival, survivorship and shark, ray and elasmo-branch) and covered the period 1992 to March 2015. The re-view focused on studies relating to elasmobranchs taken in fisheries targeting tuna, tuna-like species and/or sharks. For each study, the following information was collated: (1) study location and origin of the data; (2) objectives of the study;
2.3 Performance assessment of technical mitigation measures
After identifying potential types of interactions with fish-ing gears, and a short description of each mitigation option, de-tailed comments on the advantages, disadvantages and caveats for each MM are provided. Technical MMs were categorized as “fishing gear modification”, “fishing practices and strat-egy”, and “Protocols to increase survival rates after release”. The performance of potential MMs found in the literature was assessed against 14 criteria (nine derived from Patterson and Tudman2009) and five additional criteria). Seven of the cri-teria assessed the biological and environmental impact of the MMs and addressed the following questions (Patterson and Tudman2009):
(1) Could the mitigation measure reduce interactions with elasmoranchs?
(2) Could it minimize the level of discarding?
(3) Could it facilitate the escape of by-caught individuals? (4) Could it improve the survival of elasmobranchs? (5) Could other higher vertebrate taxa likely derive benefit
from the measure?
(6) Could it have other positive impacts on the environment (e.g. in relation to pollution or habitat degradation)? (7) Could it affect fuel consumption and/or the carbon
foot-print?
The remaining group of criteria assessed the impact of the measure on the fishing activity and the perception of the measure by the fishing industry, and addressed the following:
(8) Would the measure impact overall catch, catch rates or quality of the target species?
(9) How easily could a positive response be detected? (10) Would implementing the measure induce additional
costs?
(11) How difficult would be the implementation? (12) Would it impact current data collection on bycatch? (13) Would it impact crew safety?
(14) Would the fishing industry be supportive?
A qualitative ranking system was adopted to synthesize all in-formation given equal weighting to all criteria. Attribute values were derived from comments given in the publication and also from the expertise of the authors. Each criteria was scored on a 5-point scale (+2 to –2) where –2 = very negative impact on bycatch and/or an anticipated very poor acceptance from fish-ers, –1= negative impact and/or poor acceptance, 0 = none or unknown effect or not applicable; 1 = positive impact and/or acceptance, and 2= very positive impact and/or acceptance. The overall score for each MM was the sum of the scores for each criterion. It was also identified whether the measure was experimental, tested at a large scale, or already implemented in the field.
Currently 35 management resolutions or recommenda-tions for elasmobranchs have been adopted by the five main t-RFMOs to mitigate the effects of tuna fishing on elasmo-branch populations. These cover sixteen types of technical MMs (Table1). Most measures are recent, with 5 (14%) hav-ing been adopted between 2004 and 2005 and 24 (69%) since 2009 (Table1).
The literature review identified nine generic MMs that have been recommended irrespective of the fishing gear. These mea-sures range from input controls to limitations on what (species, sizes) can be retained on board. All generic MMs have advan-tages and drawbacks (Table2).
3.2 General assessment of technical bycatch mitigation measures
The published literature on this topic has increased in re-cent years. Of a total of 118 relevant studies identified for the period 1963–2015, 103 (87%) have been published since 2005 (Tables3and4). The literature analysis provided an in-dication of how the MMs may benefit elasmobranchs, other taxonomic groups and the environment, as well as how they could impact the profitability of the fishery and logistic con-siderations for practical implementation. The review showed, for all gears combined, that gear modifications were the most widely proposed measure (19 MMs) followed by fishing strat-egy (13 MMs), with three generic MMs irrespective of gear type (Table3). The assessment scores for the three categories ranged from 0 to 12 (overall score) while overall scores for all criteria combined ranged from 1 to 20 (TableS2d). This ranking is intended to help managers identify potential man-agement options, based on best available current knowledge.
Three mitigation measures belonging to the third cate-gory of measures (“Enforcement of safe handling and release”, “Workshops and training”, and “Mandatory sea turtle/shark handling tools”), as practices to increase survival rates after release in all fisheries obtained high scores (13–20), as fishers are generally supportive of these measures, they would be easy to introduce, and incur limited expenses (TableS2d).
3.3 Mitigation measures for longline fisheries
Twenty potential MMs were identified for longline fish-eries, comprising 11 for “Fishing gear modification”, six for “Fishing practices and strategy” and three for “Practices to increase survival rates after release”. Overall scores ranged from 5-19 (Fig. 1, Table S2da). Among the MMs in the “Fishing gear modification” category, “Prohibition of wire leaders” obtained the higher scores for both tuna and sword-fish longline sword-fisheries (score= 19) and “Prohibition of light attractors” for tuna fisheries (score= 16). Use of “Artificial bait” was identified as potentially useful to improve selectivity, but further development is needed (score = 17). The MMs
specifying management measures relating to elasmobranchs implemented by t-RFMOs during the period 2003 to 2014. IATTC: resolution binding, recommendations non-binding; ICCAT: recommendation binding, resolution non-binding; WCPFC: Conservation and management measure binding, resolution non-binding; IOTC: resolution binding, recommendation non-binding; CCSBT: recommends to members and cooperating non members to comply with all current binding and recommendatory measures aimed at the protection of ecologically-related species (including elasmobranchs) adopted by IOTC, ICCAT and WCPFC.
Management measure IATTC ICCAT IOTC WCPFC
Implementation of shark NPOA Res 03-10
Prohibition of wire for tuna-directed fisheries CMM 2014-05
Report catch Res.C05-03 Res.04-10 Res.05-05 CMM2010-07
Full utilization of shark products Res.C05-03 Res.04-10 Res.05-05 CMM2010-07
5% fins/body ratio Res.C05-03 Res.04-10 Res.05-05 CMM2010-07
Mitigation research Res.C05-03 Res.04-10 Res.05-05 Res.2005-03
Reporting in logbooks Res.C05-03 Rec.07-06 Res.10-02/13-03 Res.2005-03
Observers Res.C11-08 Rec.11-10 Res.11-04 CMM 07-01
CMM2014-01 Prohibition of retention of:
– Thresher sharks Alopias spp. Rec.09-071 Res.12-092
– Oceanic whitetip shark Carcharhinus longimanus Res.C11-103 Rec.10-074 Res.13-065 CMM2011-046
– Hammerhead sharks Sphyrna spp., Rec.10-087
– Silky sharks Carcharhinus falciformis Rec.11-088 CMM2013-089
Prohibition of purse seine setting on whale sharks Res.C13-04 CMM2012-04
Prohibition of large scale driftnets in the high seas Rec.03-04 Res.12-12 CMM2008-04
Management plans for sharks fisheries CMM2014-05
Encourage the release of live sharks, especially juveniles Res.01-11/Rec.15-06
Estimates of the mortality of non-target species (all sharks) CMM2004-04
Encourage research on shortfin mako Res.C15-04 Rec.14-06
Conservation of Mobulid rays caught in association with fisheries
CCSBT: With only one exception, all CCSBT members and cooperating non-members are also parties or cooperating parties to IOTC, WCPFC
and/or ICCAT. As a consequence, any binding bycatch mitigation measure of these RFMOs is in practice binding for the CCSBT
mem-ber/cooperating non-member when fishing within that convention area.
NPOA: National Plan of Action.
influencing hook characteristics (“Corrodible hooks”, “Weak hooks” and “Increased hook size”) scored 10–15. Nevertheless, the additional time needed to prepare the gear and the drastic changes in the fishing gear itself would likely hamper the acceptance of such measures by fishers. The use of “Circle hooks” only, i.e. prohibition of J-hooks and tuna hooks, scored 11 and, although implemented in several areas already, more detailed case studies are needed. Those MMs dealing with deterrents (“Magnetic, electropositive or electrical deterrents”; “Olfactory repellents”; “Auditory deterrents/attractors”) scored poorly at the present time, as these options have never been successfully field-tested.
Among the measures within the “Fishing practices and strategy” category, the highest ranking options were: “Deep setting”, “Fleet communication” and “Management of offal and spend discharge” (scores= 14, 14 and 12, respectively)
1 Alopias superciliosus. 2 Alopias spp. 3 Carcharhinus longimanus. 4 Carcharhinus longimanus. 5 Carcharhinus longimanus. 6 Carcharhinus longimanus.
7 Sphyrnidae (except for the Sphyrna tiburo).
8 Carcharhinus falciformis
9 Carcharhinus falciformis.
and were considered easy to implement and at no extra cost. “Prohibiting the use of live bait” (score= 11) may also be an acceptable measure, as it would impact on few fisheries. While “Reduced soak time” (score= 10) would be less popular with fishers, especially for longliners where swordfish and sharks were important catches, as fishers assume that it would be as-sociated with reduced catches of target species. “Restricting fishing on topographic and oceanic features” (score = 10) was considered difficult to implement, and more comprehen-sive studies on the temporal and spatial distribution of sharks in relation to their position in the water column and in rela-tion to water temperatures (including oceanic fronts etc.) are necessary.
Among the 20 MMs considered, 17 (85%) were also con-sidered beneficial for other bycatch groups, twelve (60%) might reduce interactions with sharks, 13 (62%) might have the ability to minimize the level of discarding (as opposed to facilitating escape from the gear, which was found in only four cases), and eight (38%) could improve survival. Two of the MMs might increase fuel consumption (“Reduced soak time” and “Restricting fishing on topographic and oceanic fea-tures”) and another two might reduce the impact on the wider environment, whether by reducing plastic and battery waste (“Prohibition of light attractors”) or through reduced pressure on resources of bait fish (“Artificial bait”).
Ta b le 2 . S u mmary of adv ant ages and d is adv ant ages of generi c m anagement m easures for reduci n g bycat ch of el asmobranchs in tuna and tuna-l ik e fi sheri es. M a nagement mea-sur e Adv a ntage Dis a dv antage Remarks S our ce Legal cons traints in fishe ry fo r fin cu tti ng and re m ova l • Fi shi n g eff or t and fi shing m o rt ality on sh arks could b e reduced, as num bers re-tained depend on hold capacity , as fi ns were a h igh-v alue, lo w v olum e p roduct • E n ables b etter quantifi cation and sp ecies identifi cation o f landings • F is h er s ar gue that the obligation o f land-ing the sh ar k car cas s w ith fi n s n atur ally attached re duces on-boar d st or age, in-creas es labour cos ts and that the fl es h can deter ior ate w hen d ef ro sting is re-quired for rem o ving the fi ns • Required h igh rates of obs erv er co v -er age and /or ins p ections w h en v es se ls land • Pos si ble increas e in trans -s hipm ent o f fi n s if lo w le v els of enf o rcem ent at sea • Finning prohibitions di v ert attention fr o m as se ss ing w h ether catch le v els ar e su st ai n ab le • Is su es w ith com p liance and enf o rce-me n t C am h ie ta l. W als h et al. Clar k e et al. ( 2013 Q u otas fo r b y cat ch sp ecies • Quotas m ay h elp lim it landings • Benefit to st ock in ques tion d epends on dis card survi v al • May incenti vize finning or high grading this st udy S p ecies re te n tion p roh ib it ion • Reduced fi shing m o rt ality on the m os t vulner able bycatch sp ecies • Depending on their le v els o f o ccurrence and /or m ark et v alue, m ay not ha v e se -v ere cos t to the fi sh ing indus try • Benefi t to sp ecies in ques tion d epends on dis card survi v al • P o ss ible identifi cation p roblem s w ith so me ta x a • S o m e “pr ohibited species ” m ay ha v e high v alue p roducts (e. g . fi ns , g ill rak-er s, ja w s) • Can im p act o n retention o f d ead sp eci-m ens for scientific study this st udy Mi ni m u m landi ng si ze (M L S ; the sm all-es t length at w hich it is le gal to retain the sp ecies ) • ML S re gulations can encourage fi sh ing to occur o n g rounds where sm all fis h are les s ab undant • F is h er s m ay im pr o v e gear se lecti v ity to reduce capture probability of young fi sh • If ML S re gulations do not decreas e en-counter rate, then their su cces s is d epen-dent on sm all fi sh being releas ed li v e and h av ing a high pos treleas e survi v al • In so m e sp ecies (e .g ., blue sh ar k and shortfin m ak o) it has b een sh o w n that at-v es se l m or tality is higher in sm aller indi viduals • Studies to better d elineate pupping and nurs ery grounds should b e encouraged Car ru ther s et al. Coelho et al. , 2013 ) Maxi m u m landi ng len g th (M LL; th e lar g es t length at w h ich it is le g al to re tain the species ) • Dis courages the tar geting o f lar ger indi-viduals , w hich are o ften m ature fem ales and the m o st fecund • ML L re gulations can encourage fi sh ing eff or t to m o v e aw ay fr o m ar eas at tim es w h en lar g e (of ten fem ale) sh ar ks aggr e-gate • L ar g er sh arks can be higher v alue • E ff ecti v enes s d epends on dis car d sur -vi v al • If the species is a tar geted species , then the eff ecti v enes s als o d epends on whe the r eff or t is redir ected to sm aller fishe s • Can create p roblem s for ho w fi sh ers as -se ss th e si ze o f la rg er fi sh es , esp ec ia ll y w h en ali v e. • In so m e cas es , a de gree of tolerance m ay b e required b y enforcers if som e fi sh ar e jus t o v er M L L , es pecially if pos t-m o rtem changes allo w landed fi sh to be “s tr etched” m or e eas ily w h en m eas ur ing
Ta b le 2 . cont inued. C o mp en sa tion miti-gation / Industr y se lf-p o licin g • Reduction o f shar k catches and m or tal-ity • G reater in v o lv em ent o f fi sh er s in the m anagem ent of their fi sh eries • Could enhance collaborati v e w ork w ith sc ientis ts to re duce bycatch and bycatch m o rt ality • M ay im p act the sus tainability of the ac-ti vity for boats w h ich cannot reach the goals • Re gulations propos ed by authorities o r by the fi sh ing indus try its elf could fi -nancially penalize indi vidual v es se ls or a fi sh er ies as so ciation w hen bycatch st andards are not m et • Reducing o r w ithholding an y subs idies , or increas e cos t o f the perm it or licens e fe e • Fis h eries m ay benefit from ‘en viron-m ental’ accr editation if their m ain catch recei v es a higher v alue G ilm an ( 2011 ) Spati al /temporal clos u re Re gulations in v o lving clos u re or gear res trictions in particular fis hing zones and /or fis hing seas ons . • Reduction o f shar k catches and m or tal-ity • Reduction o f catches and m or tality fo r other taxa • Could induce an increas e in fuel con-su m p tion for reaching o ther fi shing grounds • Caus e p roblem s to fl eets w ith lim ited ra nge capacity • Could increas e fi sh ing im p act on other grounds through fl eet dis p lacem ent • Can b e d iffi cult to enf o rc e in h igh seas ar eas • Clos ed ar eas in re m o te high seas ar eas that aff ect le gal fl eets m ay then be tar -geted b y IU U v es se ls • N eces sity to kno w the patter n s o f h abi-ta t u se , b ys ex an db ys iz es , b o th h o r-izontal and v er tical of sh ar k and other taxa • Need to unders tand the lik ely res pons e in fleet beha viour to gauge benefits to st ocks of concern in relation to potential im pacts o n o ther fis hing grounds • E as y to m onitor and enf o rc e w ithin the E x clus iv e E conom ic Z ones o f the re g-ulating n ation and fleets equipped w ith VMS • Re gulation in international w aters is re-st ri cted to the fi sh er ies o f the re gulating nation o r international agreem ents A lv er son et al. ( 1994 ); L eathw ick et al. ( 2008 ); Dunn et al. ( 2011 ); Se nk o et al. ( 2014 ) Fi sh in g eff or t re duc -ti on L im its on the o v er all fi shing capac-ity of the fl eet • Reduction o f shar k catches and m or tal-ity • Reduction o f catches and m or tality fo r other taxa • Can h av e fi nancial im p lications if the v es se ls still need to tr av el long dis -tances to the fi sh ing g rounds b u t once there the y h av e to reduce the eff ort (les s hooks or se ts ). • Monitoring com p liance can be di ffi cult (and expens iv e) to achie v e/ im plem ent • V arious approaches can b e u se d to lim it o v erall fis hing eff or t, su ch as lim iting the num ber and si zes (or capacity) o f v es se ls par ticipating in a fi sher y, the num ber o f hooks , the num ber o r dura-tion o f fi sh ing oper ations • Reducing v es se l size could reduce fuel cons um ption Da vis and W o rm ( 2013 ) Bycatch man agemen t • Reduction o f shar k catches and m or tal-ity • Reduction o f catches and m or tality fo r other taxa • A n y m eas ur e that res tr icts fi shing faces reluctance by the indus try • L and-all policies can re su lt in m ix ed fi sher ies being clos ed ear ly w h en the catch lim its fo r the sp ecies w ith the sm alles t quota are reached (“chok e” sp ecies ), or if bycatch lim its of vulnera-ble taxa ar e ex ceeded S ev er al m anagem ent appr oaches ha v e been de v eloped to reduce w as tage, bycatch, and dis carding in fis heries E x am ples include (1) national bycatch polic y; (2) bycatch quotas or caps ; (3) indi vidual h abitat quotas (IHQs); (4) byc at ch ta x syst em (5) ze ro (d ead) d is car d s policies Da vis and W o rm ( 2013 )
Ta b le 3 . Ad v an ta g es an d d isa d v an ta g es o f te ch n ic al mitig atio n m ea su re s fo r re d u cin g ela smo b ra n ch ca tc h es in tu n a an d tu n a-lik e fi sh er ie s an d o v era ll sc o re o bt ai ned b y each L ongl in e fi sher ie s (S W O : S w or dfi sh, T U N : T una S H K : S h ar k) Miti ga ti on ca te g or y Miti ga tion m ea su re O v er a ll score A dva nt ag e Dis adva nt ag e R em a rks So u rce Fishin g Ge ar mo dific ati ons Prohibition of li g ht a ttr a ctors (no chemical li g ht sticks, batter y -powered li g h t-emittin g di od es , “electro lu me ”, etc.) SWO: 10 TUN: 16 SHK: 14 • Red u ced shark and sea tu rtle bycatch • Red u ced po ll u tion (plastic con tainers,
chemical components, batt
eries). • Eas y to im plem ent. •
Fishers fear red
u
ced catch rates
of tar g et speci es. • Fishers co u ld increase effort (sets, n u mber of
hooks per set)
to compensate p erceived loss of cat ches. • Alread y im plem ented in som e ar eas • Effectiven
ess of the chemical li
g ht-sticks appears to be low, b u t si g nifican t, on C P UE and catch composition • Diffic u lt to enfo rce in h ig h seas fi sheries •
Some fishers avoid
u sin g li g ht s ticks beca u se th ey beli eve it incr eas es catch rat es of sharks • LEDs have a similar intended effectiven ess th an chemical li g ht sticks b u t may have less environmental im
pact if batteries are stored and
disposed of ashore cor rectly • Eco-tox icolo g
ical tests showed toxicity of
chemical li g ht-sticks fo r marine or g an isms, especially u nder low dil u
tion conditions or direct
contact.
(Alessandro and Antonello
, 2010; Berkeley et al ., 1983; Bi g elow et a l. , 1 999; Bromhead et al. , 2012; d Oliveir a e t a l. , 2 014; Gless et a l. , 200 8; Hazin et a l. , 2005; Ivar do S et a l. , 2009; Loh m al. , 2006; P inho et 2009; P oisson et al. 2010; Santos et al. Wan g et al. , 200 7 ) Prohibition of wire le ad ers ( only n y lon allowed) SWO: 19 TUN: 19 SHK: 11 • Red u ced n u mbers of sharks bro ug ht to vessel (bite thro ug h) . •
Saved time thro
ug h red u ced h andlin g of sharks. • Catch rates of other val u ab le t u na an d billfish species are hi g h er on n y lon th an on w ire lead ers. • Eas y to im plem ent • The r ed u ced in teractions with liv e sharks red u ces the r isk for the crew. • The u se of wir e leaders is con sidered ind icatin g shark tar g etin g as it is known to si g nificantly
increase the retention
of sharks. • Alread y im plem ented in som e ar eas. • Fishers acknowled g e th at wir e leaders wer e often deplo y ed to red u ce g ear loss fro m sharks. • N y lon lead
ers catch more bi
g ey e t u na, T hunnu s obes u
s and all tar
g
et species com
bined, while wir
e lead ers catch m o re bl u e shark , Prio na ce g lau ca
and all sharks co
mbined • The f ate of es caped animals hooked on n y lon traces is no t kno wn. Need for more st u dies for b etter u nderstandin g of the impacts on o ther g ro u ps of animals. (Afonso et a l. , 2 012; clark e, 2011; K ir b y Ward, 2014; S P C-OF 2013; Stone and Dixon, 2001; Ward et al. , 2008) Circle hooks
(no J-hooks, which
tend to be f u lly in g ested m o re freq u ently and th u s likely to in cr ease post-release mortality and no circle • Red u ced at-vess el mortality of shar ks compared to J-h ooks • Red u ced catch r ates of • Conflictin g res u lts concern in g potential r ed u ctions in catch rates of tar g et sp eci es. • P otential in creases in bycatch • Alread y im plem ented in som e ar eas and fisher ies • Effect on shark s u rvivorship is no t f u lly known • Red u ction of s ea t u rtle in ter actions: the u se of circle hooks h as conserva tion
benefits for sea
(Epperly
et
al.
, 2012
Fernandez-Carvalho et al., 2015; and
Kotas,
Ta b le 3 . C ont inued. hooks, which are more fr eq u ently hooked in th e jaw) SWO: 11 TUN: 11 SHK: 11 pela g ic stin g ray • Red u ced impact on crocodile sh ark and small sharks • Hookin g locatio n of circle hooks can lead to a decrease in postrelease mortality of incidentally ca ug ht species • An y sharks to b e retained may b e of better q u ality • Eas y to im plem ent
of some species (in
cl u din g sharks). • Comparisons between hook ty p es have show n varied r es u lts between fi
sheries, and species,
so m eas u re m ay be in effectiv e • Fishers have sugg ested th at baitin g circle ho ok is more time cons u min g . • Additional
cost for fishers if
mandator y meas u res bro ug ht in witho u t warn in g tu
rtles; J-hooks and t
u na hooks have a m u ch g reater probability of bein g swal
lowed than circle
hooks.
In addition,
as the
hook size increases,
the likelihood of swallowin g decr eas es • The u
se of circle hooks has conservation ben
efits for billfi sh; th ey may catch f ewer sea b irds t h an those sets u sin g J-hooks; potential r ed u ction in the overall r ate of m arine mammal in teractions • Need to d efin e a u n iform s y stem for ho ok
characteristics and terminolo
g y • Notable differ en ce in th e experimental d esi g ns of the p u b lished st u dies • Need to u nders tand the ro le o f all oper ation al characteristics in g ear performan ce analy sis • Need for improved species-specifi c contro lled experiments to p
rovide more definitive res
u lt s • Catch-and-releas e st u dies
have revealed that one
of the stron g est correlations of mortality for fis hes is deep hookin g in bod y or g ans s u ch as th e oesopha gu s, g ills, or stomach , which is lar g ely infl u en ced b y ho ok choice. • Makin g the u
se of circle hooks mandator
y co u ld affect shark catchab ilit y . In t h e ev ent th at it increased the n u mber of sharks
hooked, this may
offset an
y
impr
oved escape rate or postrelease
su rvival. • Time series of fi sher y -d epend en t C P UE data u sed in some stock as sessments may be compromised et a l. , 2011; Galeana-Villasenor et al. , 2008; Godin et al. , 201 2; Graves and Horod y sk y , 2008; Graves et al. , 2012; Kaplan et al. , 20 07; Moazzam and N awaz, 2014; M u ru a et al. , 2013; P acheco et al. , 2 011; P iovano et al. , 2 009; P rince et al. , 200 2; P rince et a l. , 2007 a; R ead, 2007 ; Rice et al. , 2012 ; Richards et al. , 2 012; R u dersha u sen et al. , 2012; Sales et al. , 2010; Sa u ls and A y ala, 2012; Serafy e t a l. , 20 12; Serafy e t a l. , 20 09; Stokes et al. , 20 11; Ward et a l. , 2009; Watson et al. , 2005; Wilson and Diaz, 2012; Yokota et al. , 2006; Yokota et al. , 2012) Corro d ible hook 11 • Lower cost th an stainless steel hooks. • Eas y to im plem ent and adopted b y the fishin g ind u str y . • Co u ld red u ce lon g -term heal th im pact
(infections) if bitten off by
a shark.
•
The fate of escaped animals is not known
•
The economic impact
of adoptin g corrodib le ho oks req u ires a thor o ug h assess
ment, as these hoo
ks wo u ld need to b e replaced more often th an the lo w-g rade stain
less steel hooks c
u rren tly u sed in fishin g operations. (McGrath et al. , 2011; P atterson and T u dm an, 2009) We a k hook (cir
cle hooks with
smaller diam eter wire) 15 • P ossible red u ction of the incid ental catch of lar g er sharks •
The ability of wea
k
hooks to release
lar
g
e fish alive and in
g ood condition is q u esti onable • P
otential loss of lar
g e individ u als of other co mm er ci al species •
The economic impact
of adop tin g weak hoo ks req u ires a thor o ug h assess
ment, as these hoo
ks
wo
u
ld need to b
e replaced more often th
an the
lo
w-g
rade stain
less steel hooks c
u rren tly u sed in fishin g operations. (NMFS, 2009)
Ta b le 3 . C ont inued. Incre a se in hook si ze 10 • P ossible red u ction of the incid ental catch of u nwanted species • P otential red u ction in catch es of some tar g et species. • Efficiency of the m eas u re n eeds to be accessed as it m ay im pact t ar g et species catch es (P iovano et al. , 2009) Artifici a l b a it SWO: 17 TUN: 17 SHK: 17 • P
ossible increase the species-select
ivity of the g ear • P ossible red u ction of shark, sea tu rtle, b ird, marine mammal by catch • Red u ce or stab ilize the overall cost of bait thro ug h improved g ear efficiency (e. g . b y red u cin g b ait lo st d u rin g soak tim e) • Costs and s u pply less variab le than nat u ral b ait • P ossible red u ction of the press u re on species exploited for bait • P
otential impact on catch
rates of tar g et speci es. • co u ld ind u ce ad ditional time to bait the lin e. • Artificial b aits may have thei r own environmen tal impact. • Necessit y to u se eco-f riend ly m ateri al • Co u ld also be co nsideration of u sin g fish waste an d other s u b-prod u cts as bait (Eric k son a n d Berkeley, 2008; Garcia-C ortes et al. 2009.; Gilm an et al. 2007; Try gg vadottir et al. , 2002.; Bach et 2012) F ish not sq u id b a it SWO: 5 TUN: 13 SHK: 8 • P otential r ed u cti o n in b y catch of some shark species • Red u ced sea t u rtle by ca tc h • Mackerel b ait a tt racts sharks . • Conflictin g res u lts concern in g the red u ction of tar g et species
catch rates and the increases of some
b y catchspecies (especially for elasmobranch species). • P ossible red u ction in fisher y reven u e when mackerel was u sed instead of sq u id. • Decreased exploitation cost as sq u id can b e the more expensive bait u sed in these fisheries. • Improved st u dies to u
nderstand the combination
of hook ty pe/size and bait ty p e in relation to catch rates by species
(and size) needs
to be considered • May be d iffic u lt to con trol on -bo ard • The effectivenes s of this method co u ld be species-, fisher y - and g eo g raphically -specific (Coelho et al. , 2 012; Fernandez-C arv alho et al. , 2015; Foster et a 2012; Gilman et al. , 2008) M ag netic, E+ met a ls, el ect ric a l d eterrents 7 • P otential r ed u cti o n in b y cat ch of shark species • The im pact on t h e tar g et spe cies often u nknown • These dev ices ar e fra g il e, c o stly and th e method can b e diffi cu lt to im plem ent • Conflictin g res u lts concernin g the effi ciency of ma g netic d eter
rents from laborator
y st u dies, especially in rel ation to possible habit u ation • There is not eno ug h information on the eff ect th at ma g net and m etal co u ld hav e as rep ellent on (Godin et al. , 20 13; McC u tcheon an d Kaji 2013; Mey er et al. , 2005; O' Connell et al ., 2010; O' Connell et al ., 2011;
Ta b le 3 . C ont inued. • P oll u tion concer ns • Health and safety concerns pela g ic sharks commonly ca ug ht by commercial lon g liners . Ri gg et al. , 2009 ; Robbins et al. , 2 011; Stoner and Kaim mer, 2008; Swimmer et a l. , 2008; Tallack an d Mandelman, 200 9) Olf a cto ry re p ellents 9 • The u se of chemical shark repellen ts like shark necromon e seems to rep el sharks • Habit u
ation may occ
u r. • P oll u tion concer ns. • It is reco g nized that th e m etho d still req u ires a g reat d eal of ex
perimentation and eval
u ation , and ru ns the risk to attr act or r epel t u na or t u n a-like species.
Sisneros and Nelson, 2001 ; So
u thwo od et al., 2008 ; (Da g orn et al. , 2010; Jordan et al. , 2013;
Sisneros and Nelson, 2001; So
u thwood et al. , 2008; Stro u d et al. , 2014) (Hart and Collin, 2015) A ud itor y d et errents a n d a ttr a ct ors 9 • Low freq u en cy so u nds have stron g attr active effect on sharks. • • Diffic u lt to implement in ind u strial fisheries d u e to g ear size. • Res u lts hav e b een promisin g , b u t m o re investi g ation an d lar g e-scale tri
als are req
u ired . Given th e cu rren t limit ed stat e of its dev elopm ent, this method can n ot be consid ered at th e moment. (M y rber g , 2001 ; M y rb er g et a l. , 1969; Nelson, 1976; Nelson an d Gr u ber, 1963; So u thwood et al. , 2008) F leet comm u nic a tion 14 See table 4 fo r d etails ) 1 1 0 2 , na mli G( R edu ce d so a k time 10 • Red u ced catch o f sharks •
Decrease in at-vessel mortality
and potential
increase in postrelease survival of
discarded by ca tc h • Improved q u ality of the tar g et species • P otential red u ction in the depredation of tar g et species • P
otential for red
u ced catch es of tar g et species. • Ne g ativ e impacts on fisher safety if it red u ces th e restin g tim e for the cr ew. • Diffic u lt to monitor as the ha u lback time (
and so the soak
time) incr eases with q u antity of fish ca ug h t. • Optim al soak ti m e likel y v aries b y fisher y . • The or g anisatio n of work acco rdin g to a certain pattern m u st tak e acco u nt of th e g eneral principle of adap tin g work to the crew • Increased v itality of some species ca ug ht co u ld increase pro cessin g
time and affect crew
saf
ety.
•
Swordfish catch
did not increas
e with lon g er soak times. • The lon g line g ear is g en erally co u nter-r etrieved;
the first hook
set is the last retrieved.
The mi n im u m soak tim e is the el apse tim e be tween th e end of settin g an d the be g inn in g of the ha u lin g and the m axim u
m soak time, from start of sett
in g to end of ha u lin g of the lon g
line. While the settin
g d u ration and th e drif tin g time of the lin e can be easily monitor ed the ha u lb ack tim e incr ease si g nificantly w ith the n u mber of fish ca ug h t. (Carr u thers et al. , 2011; Erickson and B erkeley , 2008; Lokk ebor g and P ina, 1997 ; P ois son et a l. , 2010; Ward and M y ers, 2007) Devices d eplo y ed prior to the fis hing oper ation including time an d fuel gas consumption.
Ta b le 3 . C ont inued. • P
ossible increase in fishin
g effort (i.e., in creas e in the n u
mber of sets) and conseq
u ently in b ait req u irements an d fu el cons u mption Prohibition of li v e b a it 11 • Improved C P UE of ye llowfin and bi g eye tu nas • May incr ease th e b y catch rat es (i.e. sharks , sea birds, billfish) • This techniq u e is u sed only in few areas and applies to a limited n u mber of fis heries • Farmed milkfish C han os c han os is a com m on commercial bait of lon g lin e fisheries in so m e Asian co u ntr ies. • The u se of live bait is alr ead y banned in sev er al co u ntries. • Co u ld impact the c u rren t activity of th e fish farmin g . • The effects on b y catch
rates have not been
assessed. (FitzGerald, 200 4; NMFS, 2008) Dee p settin g SWO: 7 TUN: 14 SHK: 7 • Red u ction in the b y catch of those sharks livin g in the u pp er water col u mn. • Red u ced sea t u rtle by catch. • Risk of incr eas in g catch es of deeper-dwellin g shark species in som e ar eas • Techn icall y dif fi cu lt to reach the d esired depth. • May res u lt in hi g her mortality rates for fish ca ug ht (barotra u ma) • May ca u se increased discard in g of other species. • Shiftin g fishin g
effort into deep
er water can be a risk y r esponse to th e decline in shallow coas tal water r eso u rces (Beverly and Ro binson, 2004; Cambiè et al. , 2013; P atterson and T u dman, 2009; Walsh et al. , 2009; Watson and Bi g elow, 2014) M a n ag ement of off a l d isch a rg e 12 • P otential red u ction in catches of scaven g in g species s u ch as s h arks. • Red u ced interactions with seab irds. • Eas y to implem ent with no extr a cost. • P ositive s u
pport from the
fishin g ind u stry . • Meas u re may req u ire g reater observer cov era g e to enco u ra g e u ptake and to develop best pract ice. • Little is known of the impact u
pon shark catch
rates of th ese pr acti ces. (Gilm an et al. , 2008)
Ta b le 3 . C ont inued. Fishing practice /strateg y R estrictin g fis h in g on to p o g rap hic a n d oce a nic fe a tu res 10 • Areas of hi g h elasmobranch ab u ndance can b e avoided . • Some areas may be associated with ph y sical feat u re s and s u ch sites can b e d esi g nated easily. • S u ch areas may also be u sed by tar g et species. • Diffic u lt to enfo rce in h ig h seas. • Some prod u ctiv e ar eas may be associated with oceano g raphic feat u
res and so have var
y in g de g rees of spatio-temporal fidelity • If le g al fisheries avoid s u ch
sites, then they
may be exploited more b y IUU fisheries • May inc rease steam in g tim es
for some vessels
• More comprehensive st u dies o n the distr ib u tion and behavio u r of sharks and tar g et species in relation to ocean o g raphic and to po g raphic feat u res req u ired . (Bi g elow et al. , 1999; Gilman et al. , 20 07; Watson et al. , 20 05) Practices to i ncr ease su rvival rates Enforcement o f the p roto cols o f sa fe h a n d lin g a n d rele a se 14 • Improved safety for crews. • Effective meas u re for species with low at-vessel m o rtal it y. • May improve post-release s u rvival, incl u din g for species which c u rrently have a hi g h discard mor tality . • Eas y to implem ent with relativel y l itt le expense • P ositive s u
pport from the
fishin g ind u str y as it co u ld be im plem ented
with little expe
nse. • Mandator y m eas u res can req u ire hi g h lev els of observer covera g e. • Ability to have opt imal handlin g of sh arks may be compromised o n some vessels b y the desi g n of the d eck . • Booklet d edicated to skipp ers and cr ew s, presentin g the g ood practices sh o u ld be dev elop ed initi all y • Monitorin g the u ptake and im plementation of these pract ices is nece ssar y • F u rther research on shark
stress and postrelease
mortality co u ld help in improvin g handlin g pract ices • To improve th e crews' awar eness of the b y catch iss u e, one deckh and co u ld be desi g nated “B y catch mana g er ” to coo rdinate g ood b y catch practices on -board . (Carr u thers et al. , 2011; P atterson and T u dman, 2009) M a n da tor y s a fe h a n d lin g eq u ip ment for s h a rks a n d t u rtles (de -hooke r, m o u th opene r, bolt cu tter, line c u
tter with lon
g handle, dipnet). 13 • Improved safety for crews. • Red u ced postrelease mortality of sharks and other sensitive s p ecies • P ositive s u
pport from the
fishin g ind u str y . •
Allows crew to safely discard p
ela g ic stin g ra y and recover hoo ks. • Uptake of su ch tools can req u ire approp riate tr ainin g and ed u cation pr o g rammes and su fficien t lev els of observer covera g e • Alread y im plem ented in som e fisheries • Monitorin g the implementa tion of these practices onboard is n ecessar y (Carr u thers et al. , 2011) Worksho p /Tr a inin g s 13 s li at e d r of 4 el ba t ee S
Ta b le 3 . C ont inued. Miti ga ti on ca te g or y Miti ga tion Me a su re A dva nt ag es Dis adva nt ag es R em a rks So u rce Fishin g Ge ar mo dific ati ons Prohibition of Ent a n g lin g F ADs 17 • Red u ction of th e probability
for sharks and sea t
u rtles to g et entan g led in the DFADs (g host fishin g ). • Red u ction of sy n thetic m aterial d ebris. • Eas y to im plem ent. • P ositive s u ppor t from the fishin g ind u str y if the efficiency of th is device is gu aranteed . • The cost of s u ch DFADs is hi g her than a “re gu la r” one. • Shorter lifespan . • G u idelin es for non-entan g lin g DFADs has be en develop ed b y ISSF (Anon y mo u s, 20 13; Da g orn et al. , 2010; Filmalter et al. , 2013 ; Franco e t a l. , 20 09) M a n da tor y u se of ho pp er 15 • Increased r eten tion of lar g e
sharks and other b
y catch on the u pper deck, so facilitatin g saf e handlin g
and live release.
• No impact on the t ar g et species • P otential cost of modify in g vessel desi g n if str u ct u ra l chan g es req u ired • Redesi g nin g th e hopper is req u ir ed to im prove the reten tion of small sharks. (P oisson et al. , 2 014b) R ele a se pa nels f o r sh a rk 10 • Red u ced catch o f sharks. • No impact on the t ar g et species. • P ositive s u ppor t from the fishin g ind u str y if the efficiency of th is device is gu aranteed . • • Needs modifications to th e p u rse
seine net, which co
u ld disco u ra g e fishers • Diffic u lt to implement/ enforce as it can incr ease th e tim e of the fishin g operation. • P romisin g
approach which needs
fu
rther refin
ements of this concept
with addition al testin g and experimentation . (Itano et al. , 201 2 ) Tropical
tuna purse seine fi
sheries Im p ro v ed con v ey or belt a n d w a ste ch u te d esi g n 13 • P
otential way to red
u ce dama g e on sharks (and other b y catch ) and post-release mortality. • A u thorize a q u ick release directly from the lower d eck • P ositive s u ppor t from the fishin g ind u str y as it co u ld be possible to redesi g n the s y stem • Fishers co u ld th en vol u ntarily adopt this pract ice. • These devices ar e not standardized and th eir
shape and location
var y . • Improved desi g n of s u ch s y stems wo u
ld likely improve dis
card su rvival of b y catch. • The conv ey or belts c u rr ently on vessels can b e an obstacl e to cro ss for the crew w h en they w ant to release sharks.
Most of the time,
crews are rel
u
ctant to leav
e their
workstation to release sharks from the
u pp er d eck . • The postrelease su rvival of the shark released thro ug h this dev ice is u nknown. (P oisson et al. , 2 014b) Reduced interactions with sharks and redu ced risk s of accid ent for the crew.
Ta b le 3 . C ont inued. Fishin g p ra cti ces/str ate gy Settin g on bi gg er agg re ga tions 11 • Red u ced total b y catch • Eas y to imp lement as
skippers are able to determine th
e size of the agg re g ation pr io r to settin g net. • P ositive s u ppor t from the fishin g ind u stry as this method co u ld be u sed in conj u
nction with other
incentive based sy stems. • Eas y to co ntrol with lo g book and observer d ata • Only moderate effects on th e total b y catch. • Diffic u lt to im plement/enfor ce in the absence of appropriate obs erver covera g e. • Fishers co u
ld adopt this meas
u re vol u ntarily when approachin g a pre-determined seasonal bycatch q u ota, b u t w ish to con tin u e catchin g t u na. (Da g orn et al. , 2012) D F AD monitorin g or m a n ag ement p la n 5 • Red u ction of total b y catch • Stron g
opposition of the fishin
g ind u str y . • Increased f u el cons u mption while increasin g searchin g time. • Deplo y in g a g reater n u mber of
DFADs in the water does not necessaril
y help fishers to catch more t u na, b u t does increase the level of fishin g effort and b y catch. (Da g orn et al. , 2 013; Sempo et al. , 2013; S P C, 2009) B a n of s upp ly v essels 9 • Red u ction of th e n u mber of FADs deplo y ed • In the P acifi c O cean , i t h as alr ea d y been proposed to prohibit th e u se of tend er vessels operatin g in su
pport of vessels fishin
g on DFAD s. • Only few fis heries ar e u sin g su pply vessels. (Arrizabala g a et al. , 2001; Da g orn et al. , 20 13) To w in g D F AD o u t of net a fter encirclem ent 12 • P otential red u ction of shark by ca tc h •
Release of the comm
u nity associated with the FAD aliv e • No eviden ce of the shark behav io u r. •
Risk for fishers
if t
u
nas are seen or
tho ug ht to escap e from th e n et. • P romisin g
approach which needs
fu rther r efinements of the concept with addition al testin g and experimentation . (Hall and Roman, 2013) M u lti p le F ADs 11 • P otential red u ction of shark b y catch. • Not eno ug h information at the moment. • More investi g
ation on the meas
u re at lar g e-scal e tri als req u ired . (Schaefer and F u ller , 2011)
Ta b le 3 . C ont inued. Use b a it st a tion 6 • P otential red u ction of shark b y catch. • Not eno ug h information at the moment. • The k ey q u
estions for this st
u
dy
are: 1) wheth
er
the bait station
is
more attractive to the sharks than a FAD; 2)
whether the sharks can be
attr acted witho u t th e t u n as bein g attr
acted as well; and 3) wheth
er the u se of bait s tations is practical and efficien t wit
hin the constrain
ts of a p u rse-seine fishin g . (anon y m o u s, 20 07; Kondel and R u sin, 2007; Scott, 2007) R estriction of settin g on w h a le sh a rks a n d m a ri n e m a mm a ls 13 • Red u
ced safety risks for
crew • Red u ced postrelease mortality of s harks and other sensitive s p ecies • Red u ced net dama g e • Red u ced time spent handlin g me g afa u na • Eas y to im plem ent • P ositive s u ppor t from the fishin g ind u str y • Eas y to co ntrol with lo g book and observers d ata • Moderate improvement of pr esent sit u ation
since whale sharks (an
d
m
arine m
am
m
als) are rel
eased aliv e in the majority o f cases witho u t bein g bro ug ht on-boar d. • Diffic u lt to implement/enfor ce i n the absence of appropriate obs erver covera g e. •
Some t-RFMOs adopted meas
u res to prohib it setti n g intention all y on whale shark and to release u
nharmed accidental bycatch (WC
P FC CMM 12-04, IOTC Res. 13-05, IATTC C 13-04). (anon y mo u s, 20 07, 2010; Capietto et al. , 2 014; clarke, 2011; Speed e t al. , 2008) Enforcement of the p rotocols of s a fe h a n d lin g a n d rele a se •
Improvement of the saf
ety for the cr ew. • Uptake of s u
ch tools can req
u ire appropriate tr ainin g and ed u cation • A first version of g ood practices has been developed for the EU (P oisson et al. , 2 014a; P oisson et a l. , 2014b; P o isson et a l. , 16 • Effective meas u re especially for s p ecies with low at-h au lin g mortality. • Red u ction of
the shark
post-release mortality. • Eas y to implement with relativel y l itt le expense • P ositive s u ppor t from the fishin g ind u str y pro g rammes and s u fficient levels of observer covera g e p u
rse seiner fleet
and can be adopted for o ther fisheries. • A st u dy
shows that if sharks are
released as rapidly as possible and handled in a g ood manner, b y -cat ch m o rtalit y of silk y sharks can be red u ced b y 1 5% in the fisher y • More investi g ations on at-vessel mortality req u ir ed 2012) Worksho p /Tr a inin g 13 s li at e d r of 4 el ba t ee S Practices to increase s urvival rates
Ta b le 3 . C ont inued. Miti ga ti on ca te g or y Miti ga tion Me a su re A dva nt ag e Dis adva nt ag e R em a rks So u rce Fishin g Ge ar mo dific ati ons Mo d if y mesh sl a ck 5 • Improvement of th e s u rvivorship at ha u lin g b u t not the n u mber of inter actions • Red u ction of g illnet dama g e ca u sed b y wrapped sharks. • Red u ction of sharks b y catch witho u t havin g a deleterio u s eff ect on tar g et cat c h rates in th e cas e of anchored g illnet tar g etin g Spanish mackerel (S co m bero m or u s ma c u la tu s ) and spot (Leiosto mu s x an thu r u s ) • A maxim u m si ze limit may be u sef u l as it will protect t h e breedin g stock and lar g er shar ks likel y h a ve a bett er chan c e of s u rvivin g af ter b e in g capt u re d. •
It does not chan
g e the n u mber of inter actions • Marine m a mmals (i.e. seals) can be affected by g ear chan g es • Modification o n a case b y case basis co u ld h inder their ability to retain sharks (Hov g å rd and Lassen, 2000; McA u ley et al. , 2007; P atterson and T u dm an,
2009; Thorpe and Frierson, 2009
) M ag netic, E+ met a ls, electric a l d eterrent 1 • The u se of f e rrite ma g net
blocks appears to repel sharks.
• No reaction b e havior of the barr am u ndi L a tes c a lc a rif er to m a g netic fields. •
The size and
wei g ht of the ma g nets u sed here may p ose diffic u
lties with attachin
g
them to
nets while maintainin
g th e fishin g inte g rity and b u o y an cy of th e n e t in th e water • More research is need e d (Ri gg et al. , 2009) Use t u rtle/sh a rk li g hts • Ill u minated nets may not only be u sef u l in red u cin g sea t u
rtle interactions with
g illnets, b u t may also b e a method of red u cin g scallop e d hammerhead b y -cat ch in g illne ts. •More research is needed
to see the impact
on sharks and ray s (So u thwood et a l. , 2008; Wan g et a l. , 2007)
Dri and gill
net fisheries Fishin g p ra cti ces/str ate gy R e du ce d so a k time 8
Shorter soak times wo
u ld likel y incr ease th e s u rvivorship b u t co u ld increase the n u mber of inter
actions if the effort is
not limited . Optimal soakin g d u ration lik ely varies b y fisher y • As fishers wo u ld be movin g their g ear aro u nd more, this wo u ld potentially increase the n u mber of interactions. A red u ced soak time wo u ld be diffic u lt to monitor and ens u re compliance (Carr u thers et al. , 2011; Frick et al. , 2012; P atterson and T u dman, 2009) F leet comm u nic a tion 14 See table 4 fo r d e tails R estricte d settin g time 7 • Shark species g enerally
spend more tim
e near th e s u rface at ni g ht which co u ld res u lt in an increas e of sharks ca ug ht when ni g ht settin g . see above • Optimal settin g ti me d u ration lik ely varies by fisher y . • More r e sear ch i s needed (P atterson and T u dman, 2009) Enforcement o f the p roto cols o f s a fe h a n d lin g a n d rele a se 16 • sr e ht ur r a C( et al. , 2011; Frick et al., 2012) Ne g
ative impacts on fisher safety
if it red
u
ces the restin
g time for the crew. • Pra ctices to increa se su rv iva l ra tes
Ta b le 3 . C ont inued. Miti g ati on cate g ory Miti g ation Meas u re Advanta g e Disadvanta g e Rema rks So u rce Fishing Gear modifications
Circle hooks See abov
e 11 • Increased postrelease su rvival e k o o C ; 5 0 0 2 , i ks u S d na e k o o C( et a l. , 2012; Seraf y et al. , 2012;
Wilson and Diaz, 2012)
. Fishing practices/strate gy P rohibition of live bait See abov e 11 • Red u ced int er actions
with sharks and other bycatch, incl
u di n g sea birds ( P rince et al. , 20 07b) Fleet comm u nication 12 See table 5 fo r d etails Practices to increase su rviv al rates Enforcement of
the protocols of safe
handlin g and release See abov e 14
Increased postrelease survival
•
Given the emphasis on ta
g -an d-release strate g y, it is important to g ain some u nderstandin g of postrelease behavior and mortality . •
the mode of capt
u
re shark
can affect mortality
(e. g . common thresher) • an g ler ed u cation pro g
rammes that have tried to promote
vol u ntar y ch an g es in an g ler behavior hav e shown
promise in some inland fish
eries (Cooke and S u ski, 2005 ; Cook e et a l. , 2012; Kneebone et al. , 2013; P epper ell and Davis, 1999; Sep u lv eda et al. , 2015) Workshop/trainin g 13 See table 4 fo r d etails • As recreational an g lin g con tin u es to g row in po p u lar ity , expandin g to man y dev elopi n g co u ntries, and tar g etin g alternative species, it is
important that reasonab
le dat a appropriate fo r specific fish an d fisheries ar e available. The s u stain able u se and cons ervation of r ecreational fisher y r eso u
rces depends on the dev
elopment an d dissemination of effectiv e and pr actical cat ch-and -release an g lin g proto cols developed with stakeholders. Species-specific gu
idelines for
catch-and-release are needed , considerin g the diversity of s p ecies and v ariation in fishin g techniq u es. (Fowler and P artrid g e, 2012; Ly nc h et al. , 2010; NOAA., 2009) Recreaonal fisheries
Ta b le 4 . Su mma ry o f ad v an ta g es an d d isa d v an ta g es o f g en era l te ch n ic al mitig atio n m ea su re s fo r ela smo b ra n ch b y ca tc h in tu n a an d tu n a-lik e fi sh er ie s. M itigation m eas u re Adv a ntage Dis a dv antage Remarks S our ce D ev elop real-ti me fl eet commu n icat ion pr ogramme • Can report real-tim e obs erv ations of by-catch hots pots to b e av o ided by other v esse ls • Helps av o id hots pots o f sharks and other taxa • E as y to im plem ent • Di ffi cult to m onitor . • A v oiding bycatch hots pots m ay be com p ro m is ed b y catch ra tes o f tar get sp ecies . • May b e succes sf ul if there is n o com pe-tition for tar g et fi sh, st rong econom ic in-centi v es to reduce d epredation, bycatch and inter actions w ith unw anted species • Support from the fis hing indus try b e-caus e econom ic cos ts potentially lo w and allo w s them to dem ons tr ate en v i-ronm ental aw arenes s (Gilm an et al. 2008; Gilm an et al. 2006) W or kshops and tr ai ni ng pr ogr am m es on good handling a nd fishi ng pr ac ti ce s, a nd sp ecies id en ti fi cat ion • Im pr o v ed saf ety for cr ew s • Reduced m o rt ality of dis car ded elas m o-br anchs and other sens iti v e sp ecies • P o tential tim e sa v ings • Rais e the fis hers ’ aw arenes s of cons er -v ation is su es and encourage their partic-ipation in the su st ainable m anagem ent of m arine res ources • P o tential for fi sher s to incur cos ts when attending w o rks hops com p rom is -ing p ar ticipation. • Som e good handling p ractices m ay in-cr eas e the tim e tak en to br ing fi sh on-boar d or catch-p ro ces si ng tim e. • Re gional w orks hops for fi sh ers and ob-se rv er s could b e o rg anized to re vie w v arious m itigation m ethods and fi sh ing pr actices to re duce m or tality of bycatch sp ecies • Could b e run alongs ide obs erv er p ro-g ra mme s • Protocols for good handling and releas e sh ar ed, in o rd er to ens u re the saf ety o f the cre w and optim ize the su rvi v al of re-leas ed anim als . • Species identification w orks hops can help ens u re cor rect sp ecies catch recor d ing • Pos si ble support from o f thes e m eas ures if the y recei v e som e subs idies in retur n (Ca rrut h er s et al . 2011; Pois so n et al. 2014; Pois so n et al. 2012)
