Bycatch and Discards PDF

Bycatch & discards Dirk Zeller Sea Around Us – Indian Ocean  Bycatch & discards How define? Are they the same or something different? Bycatch Anything caught unintentionally whilst fishing for specific species or sizes...

Bycatch & discards Dirk Zeller Sea Around Us – Indian Ocean  Bycatch & discards How define? Are they the same or something different? Bycatch Anything caught unintentionally whilst fishing for specific species or sizes Either the wrong species, the wrong gender, or undersized or juveniles of the target species Origin: mortality of dolphins in tuna purse seine fisheries in the 1960s… “dolphin-free” tuna Various ways the word "bycatch" is used in fisheries Catch which is retained and sold but is not the primary target Catch of marketable fish which fishers discard (low value species, wrong size etc.) Catch of unwanted/unmarketable species which fishers throw back, such as some echinoderms and crustaceans, and various vulnerable species groups, including seabirds, sea turtles, marine mammals and elasmobranchs Catchpole et al. (2005) Marine Policy 29(5): 421-430 Hall et al. (2000) Marine Pollution Bulletin 41(1): 204-219 Hall (1996) Review of Fish Biology and Fisheries 6(3): 319-352 2/28 Alverson et al. (1994) FAO Fisheries Technical Papers T339, Rome. 233 p  Bycatch & discards Discards Portion of a catch on deck that is not retained but is thrown back, often dead or dying Discarding is driven by economic and political factors Unmarketable species Individuals below minimum landing sizes (undersized) Species which fishers are not allowed to land, e.g., quota restrictions (regulatory discards) Fishers optimizing their return (high grading) Discards a subset of “bycatch” But Bycatch definition confusion in USA…. Always check which definition of bycatch used… Catchpole et al. (2005) Marine Policy 29(5): 421-430 Hall et al. (2000) Marine Pollution Bulletin 41(1): 204-219 Hall (1996) Review of Fish Biology and Fisheries 6(3): 319-352 3/28 Alverson et al. (1994) FAO Fisheries Technical Papers T339, Rome. 233 p  Discards Highly variable in time and space, driven by the composition of the catch on deck. Discarding behaviour is driven by: Environmental factors - recruitment of small fish into the fishery Social/political factors - quota regulations - choice of fishing gear - fishers' behaviour Main drivers or discard “types” Gear based discarding Market driven discarding Regulatory discarding Catchpole et al. (2005) Marine Policy 29(5): 421-430 Hall et al. (2000) Marine Pollution Bulletin 41(1): 204-219 Hall (1996) Review of Fish Biology and Fisheries 6(3): 319-352 4/28 Alverson et al. (1994) FAO Fisheries Technical Papers T339, Rome. 233 p  Gear based discarding Different gears have different levels of bycatch potential The less selective a gear, the higher its bycatch potential (hence discard potential) Best: Traps, pots and weirs Hand-lines (shallow vs deep survivorship… swim bladder barotrauma… buoyancy) Do least damage to catch, allows easy, often live release But: predation within traps if no escape option; depredation in line fisheries Worst: Bottom trawls Gill nets Longlines Non-selective and highly body-damaging gears Survival rate generally low Catchpole et al. (2005) Marine Policy 29(5): 421-430 Hall et al. (2000) Marine Pollution Bulletin 41(1): 204-219 Hall (1996) Review of Fish Biology and Fisheries 6(3): 319-352 5/28 Alverson et al. (1994) FAO Fisheries Technical Papers T339, Rome. 233 p  Market driven discarding Market demands/prices can drive discarding behaviour Why retain something that fetches a low price? Certain sizes demanded by market or fetch higher prices Plate-sized whole fish Pollution concerns may lead to reduced prices or demand Swordfish Can be highly variable in space and time Day to day, Trip to trip, or seasonally Long-term (Canadian East Coast lobster… poor man’s food to luxury) 6/28  Regulatory discarding Fisheries regulations that impact what can and cannot be retained and landed Fishing licenses may be linked to specific species – Mandated/managed species or not Lists of species that are protected and cannot be caught, or have very low TAC – E.g., endangered rockfish (Canada): fisheries driven by avoidance fishing Quota limits - “Overage” - Discard or buy/lease quota from other fisher to maintain TAC & quota rules - E.g., Canada halibut overage trading - High grading - Discard fish of lower value out of hold to retain more valuable fish - Occurs in fisheries that are restricted to land their total catch due to management, market or physical constraints - E.g., UK dumping, NZ foreign fleet dumping Batsleer et al. (2015) Reviews in Fish Biology and Fisheries 25(4): 715-736 7/28 Torkington (2016) Marine Policy 63: 180-183  Discard data Data difficult to get or collect Fishers reluctant to record, not mandated to record, or record unreliably Only reliable manner is via independent observer data On-board – limited coverage due to cost – Biases fisher’s behaviour unless 100% Electronic (video) – e.g. 100% Canadian sablefish (Anoplopoma fimbria) fishery Making detailed studies challenging Many estimates limited to target/assessed species, e.g. ICES (Europe) stock assessments A few global assessments 8/28  Global estimates Alverson et al. (1994) 27 MT based on 1980s and 1990s data Kelleher (2005) 6.8 MT based on subset of “quantitatively complete” studies = 8% discard rate 7.3 MT if 8% applied to global FAO reported landings data Kelleher (2005) claimed that strong decline is due to Increased retention and use of previously discarded catches More selective gears & bycatch reduction devices (BRDs) BRD: See https://www.afma.gov.au/sustainability-environment/bycatch-discarding/bycatch-reduction-devices See http://www.fao.org/fishery/equipment/brd/en Alverson et al. (1994) FAO Fisheries Technical Papers T339, Rome. 233 p 9/28 Kelleher (2005) FAO Fisheries Technical Paper 470, Rome. 131 p  Global estimates Total catch Reported landings (FAO) Zeller and Pauly (2005) not a serious attempt to estimate discards, but rather present a modified viewpoint of Kelleher (2005) suggested decline in global discards Given that reported landings declined during C-E period, any increased retention/use of previously discarded catch should stabilize or increase the reported landings? But total catch (landings + discards) declines more strongly than only reported landings Zeller and Pauly (2005) Fish and Fisheries 6: 156-159 10/28 Zeller et al. (2018) Fish & Fisheries 19(1): 30-39  Global discard estimates 11/28 Zeller et al. (2018) Fish & Fisheries 19(1): 30-39  Discards by geographic area 12/28 Zeller et al. (2018) Fish & Fisheries 19(1): 30-39  Discards by geographic area 13/28 Zeller et al. (2018) Fish & Fisheries 19(1): 30-39  Discards by geographic area 14/28 Zeller et al. (2018) Fish & Fisheries 19(1): 30-39  Discards driven by foreign fleets within geographies NW Atlantic EC Atlantic (West Africa) Pre-EEZ Major foreign fishing countries Foreign fishing countries (Europe) Post-EEZ Local (Canada & USA) 15/28 Zeller et al. (2018) Fish & Fisheries 19(1): 30-39  Discards driven by local fleets within geographies NE Atlantic NW Pacific WC Pacific Local fishing fleet dominance 16/28 Zeller et al. (2018) Fish & Fisheries 19(1): 30-39  Discards primarily in EEZ waters 17/28 Zeller et al. (2018) Fish & Fisheries 19(1): 30-39  Discards by taxonomic groups 18/28 Zeller et al. (2018) Fish & Fisheries 19(1): 30-39  Discards by taxonomic groups Marketable target species 19/28 Zeller et al. (2018) Fish & Fisheries 19(1): 30-39  Discards by taxonomic groups Marketable target species 20/28 Zeller et al. (2018) Fish & Fisheries 19(1): 30-39  Discards by taxonomic groups nei = not elsewhere included 21/28 Zeller et al. (2018) Fish & Fisheries 19(1): 30-39  Discards by taxonomic groups High discard prevalence of: 1) Marketable target groups Poor product quality Poor/non-selective fishing practises Small sizes Deliberate high grading Management/enforcement failure 2) Marine fishes nei Poor information and data resolution/collection 22/28 Zeller et al. (2018) Fish & Fisheries 19(1): 30-39  Discards 2019: FAO third update on discarding Pérez Roda MA, Gilman E, Huntington T, Kennelly SJ, Suuronen P, Chaloupka M and Medley P (2019) A third assessment of global marine fisheries discards. FAO Fisheries and Aquaculture Technical Paper No. 633, Food and Agriculture Organization (FAO), Rome. xvi & 58 p. https://www.fao.org/responsible-fishing/resources/detail/en/c/1317018/ Use our data as one of their sources or comparison sources… Find similar levels… 9.1 million t per year (6.7-16.1 million t) Equivalent to 10.1% of annual reported landings ~46% of all discards from bottom trawls But not deep linked in public FAO database to countries or in space and time 23/28  Discards 24/28 Pérez et al. (2019) FAO Fisheries and Aquaculture Technical Paper No. 633  No-fit topic A topic that does not readily fit into any one specific lecture topic in BIOL3305….. Fisheries and animal welfare: Well established in animal husbandry on land – cattle farming… – phasing-out live sheep exports…. Also beginning to be addressed with marine mammals, marine reptiles etc. But not in fisheries and only very superficially in aquaculture (animal husbandry in water) Here raise one point only, related to a nice paper that makes a distinct point on this topic….. 25/28  Animal welfare Mood and Brooke (2024) did a very interesting thing… Converted fisheries catch from tonnes (industrialized commodity) to numbers of individual fish…. Gives a much clearer picture of our impacts This “number of individuals” approach is the norm for farmed animals… So why not for fish? Used: FAO capture production (landings) tonnages (2000–2019) Estimates of mean individual weight, based on internet-sourced capture and market weights Results: Between 1,100 and 2,200 billion (1–2 x 1012), or 1.1–2.2 trillion individual fish were caught annually Fisheries: Most catch is either suffocated, cut up alive, or throat cut and bled to death But see tuna sashimi fisheries…. Careful handling and brain pithing 26/28 Mood and Brooke (2024). Animal Welfare 33: e6  Animal welfare Mood and Brooke (2024): Around 80 billion land animals are slaughtered for food annually…. vs. 1,000-2,000 billion finfish Thus, fish predominate vertebrate numbers used for food globally, yet little if any welfare regulations exist for handling and humane killing marine fish (Swiss protection for inland fisheries). Existing laws on captive wild animal welfare might be useful as foundation for welfare protection of wild-caught fish. Som such laws exist for aquaculture… so why no applied to wild–caught? Interestingly, even the MSC is silent on fish welfare. 27/28 Mood and Brooke (2024). Animal Welfare 33: e6 Sea Around Us – Indian Ocean