Fisheries Science: Foundation and Application PDF

Fishing gears & destructive fishing Dirk Zeller Sea Around Us – Indian Ocean  How categorize, group fishing gears? 1. By activity level Passive versus active 2. By catch method Nets vs hooks vs traps etc....

Fishing gears & destructive fishing Dirk Zeller Sea Around Us – Indian Ocean  How categorize, group fishing gears? 1. By activity level Passive versus active 2. By catch method Nets vs hooks vs traps etc. King M (1995) Fisheries biology, assessment and management. Fishing News Books, Blackwell Science Ltd., London  Passive fishing gears Fishing action occurs by the gear independent of vessel movement via engine power, although setting of gear may require vessel movement and engine power Traps/pots/weirs: enticing or guiding animals into being caught baited or unbaited (shelter seeking) King M (1995) Fisheries biology, assessment and management. Fishing News Books, Blackwell Science Ltd., London Traps, pots and weirs  Traps, pots and weirs 5/51  Traps, pots and weirs Weirs: At least for last 3000 years Most wide-spread fishing method prior to industrialization Varies widely Filous et al. (2021) Fisheries science and marine education catalyze the renaissance of traditional management (rahui) to improve an artisanal fishery in French Polynesia. Marine Policy 123: 104291  Traps, pots and weirs Hadrah weirs in Persian Gulf Al-Abdulrazzak D and Pauly D (2014) Managing fisheries from space: Google Earth improves estimates of distant fish catches. ICES Journal of Marine Science 71(3): 450-455 Garibaldi L, Gee J, Tsuji S, Mannini P and Currie D (2014) Comment on: “Managing fisheries from space: Google Earth improves estimates of distant fish catches” by Al-Abdulrazzak and Pauly. ICES Journal of Marine Science 71(7): 1921-1926 Al-Abdulrazzak D and Pauly D (2014) Ground-truthing the ground-truth: reply to Garibaldi et al.’s comment on “Managing fisheries from space: Google Earth improves estimates of distant fish catches”. ICES Journal of Marine Science 71(7): 1927-1931  Traps, pots and weirs Hadrah in Persian Gulf Unreported catch (family/clan business…) Google Earth (+ Google Earth archive) Incl. correction for low visibility (cloud, light angle etc.) >1600 images assessed Major reply & rebuttal in literature… Al-Abdulrazzak D and Pauly D (2014) Managing fisheries from space: Google Earth improves estimates of distant fish catches. ICES Journal of Marine Science 71(3): 450-455 Garibaldi L, Gee J, Tsuji S, Mannini P and Currie D (2014) Comment on: “Managing fisheries from space: Google Earth improves estimates of distant fish catches” by Al-Abdulrazzak and Pauly. ICES Journal of Marine Science 71(7): 1921-1926 Al-Abdulrazzak D and Pauly D (2014) Ground-truthing the ground-truth: reply to Garibaldi et al.’s comment on “Managing fisheries from space: Google Earth improves estimates of distant fish catches”. ICES Journal of Marine Science 71(7): 1927-1931  Reading assignment Al-Abdulrazzak D and Pauly D (2014) Managing fisheries from space: Google Earth improves estimates of distant fish catches. ICES Journal of Marine Science 71(3): 450-455 Garibaldi L, Gee J, Tsuji S, Mannini P and Currie D (2014) Comment on: “Managing fisheries from space: Google Earth improves estimates of distant fish catches” by Al-Abdulrazzak and Pauly. ICES Journal of Marine Science 71(7): 1921-1926 Al-Abdulrazzak D and Pauly D (2014) Ground-truthing the ground-truth: reply to Garibaldi et al.’s comment on “Managing fisheries from space: Google Earth improves estimates of distant fish catches”. ICES Journal of Marine Science 71(7): 1927-1931  Reading assignment Al-Abdulrazzak D and Pauly D (2014) Managing fisheries from space: Google Earth improves estimates of distant fish catches. ICES Journal of Marine Science 71(3): 450-455 Garibaldi L, Gee J, Tsuji S, Mannini P and Currie D (2014) Comment on: “Managing fisheries from space: Google Earth improves estimates of distant fish catches” by Al-Abdulrazzak and Pauly. ICES Journal of Marine Science 71(7): 1921-1926 FAO Al-Abdulrazzak D and Pauly D (2014) Ground-truthing the ground-truth: reply to Garibaldi et al.’s comment on “Managing fisheries from space: Google Earth improves estimates of distant fish catches”. ICES Journal of Marine Science 71(7): 1927-1931  Passive fishing gears Hand ‘tools’: collecting reef/shore gleaning (women/children: “invisible”) spear Hook and line: baited or unbaited handlines pole and line longlines 10/51 King M (1995) Fisheries biology, assessment and management. Fishing News Books, Blackwell Science Ltd., London Hook and line Hook and line Hand line  Pole and line (rod and reel) Pole and line Very common for tuna in 1950s Baited: live bait thrown overboard Wild bait schools Squid jigs Still practised, e.g., Maldives Considered ‘cleanest’ tuna fishing method Least bycatch 15/51 Longlines  Passive fishing gears Net gears: gillnets King M (1995) Fisheries biology, assessment and management. Fishing News Books, Blackwell Science Ltd., London  Gillnets Gillnets Bottom: generally ‘set’ gillnets Pelagic: ‘drift’ or ‘set’ gillnets Can be many km long Considerable bycatch Contributor to ‘ghost fishing’  Active fishing gears Fishing action occurs by actively moving gear across seafloor or through water column using engine power Net gears: bottom trawl (otter & beam) pelagic trawl dredges purse seine King M (1995) Fisheries biology, assessment and management. Fishing News Books, Blackwell Science Ltd., London  Trawls 2 basic types of bottom trawl Otter: using heavy Otter boards – Faster moving/more active finfish 20/51  Trawls 2 basic types of bottom trawl Otter: using heavy Otter boards Beam: metal beam keeps net open – Flatfish and slow moving species  Trawls Pelagic or mid-water trawl May have Otter boards, weights or use net shape Single vessel Pair trawls Small- & medium-sized pelagic species  Dredges Dredges Very heavy seafloor gear Leading edge: heavy chain, toothed or inclined bar Targets sessile invertebrates (scallops, oysters) High seafloor disturbance  Purse seines Purse seine nets Encircling or surrounding fish school Mainly pelagic, but also beach purse seines – Major tuna fishing gear (canned tuna) – Small- & medium-sized pelagic species  Purse seines Purse seine nets Encircling or surrounding fish school Pelagic purse seines can be extremely large 25/51  Fish Aggregation Devices Fish aggregation devices (FADs) Surface, near-surface floating rafts Attract fish Moored or drifting Mainly pelagic, but also anchored for near-shore use Concentrate fish, not assist in new production  Fish Aggregation Devices Fish aggregation devices (FADs) Surface, near-surface floating rafts Attract fish Moored or drifting Mainly pelagic, but also anchored for near-shore use Concentrate fish, not assist in new production Fish Aggregation Devices  Fish Aggregation Devices Fish aggregation devices (FADs) Deemed ‘efficient’ Over-efficient? Yellow fin versus juvenile bigeye bycatch  Fish Aggregation Devices Capacity/fishing power concerns associated with FADs Same nominal/effective effort but more catching power Higher catchability with FADs 30/51  Fish Aggregation Devices Reading assignment: https://www.seaaroundus-io.org/sea-around-us-indian-ocean-news/un-ban-fad Will also be a topic in lecture: “Global fisheries for large pelagic species”  Summary: fishing gears 1. By activity level 2. By catch method Very large variation in gear details in space over time by target species via traditions by name etc. King M (1995) Fisheries biology, assessment and management. Fishing News Books, Blackwell Science Ltd., London  Destructive fishing Most commonly: Dynamite Cyanide  Dynamite fishing Dynamite fishing Widespread in tropical countries Illegal Easy to make  Dynamite fishing Dynamite fishing Easy fishing when other methods harder 35/51  Dynamite fishing Dynamite fishing Easy fishing when other methods harder Extremely dangerous  Dynamite fishing Dynamite fishing Easy fishing Extremely wasteful Highly destructive  Cyanide fishing Cyanide fishing Easy way to catch fish alive Dominates aquarium trade Asian live food fish trade Widespread in tropical countries  Cyanide fishing Cyanide fishing Toxicity of cyanide High delayed mortality Impact on coral etc.  Destructive fishing However, the globally most destructive fishing gear Active bottom contact gears Bottom trawling/dredging Watling and Norse (1998) Conservation Biology 12(6): 1180-1197 40/51 Kaiser et al. (2002) Fish and Fisheries 3: 114-136 Habitat and ecosystem-damaging nature of bottom trawling Watling and Norse (1998) Conservation Biology 12(6): 1180-1197 Kaiser et al. (2002) Fish and Fisheries 3: 114-136 Habitat and ecosystem-damaging nature of bottom trawling Watling and Norse (1998) Conservation Biology 12(6): 1180-1197 Kaiser et al. (2002) Fish and Fisheries 3: 114-136 Habitat and ecosystem-damaging nature of bottom trawling Problem known since at least 1376… based on a formal complaint lodged by fishers to England’s King Edward III to ban it: “… there used to be plenteous fishing, but certain fishermen for several years have contrived an instrument called “wondyrechaun" with a net so close meshed that no fish can escape. And that the great and long iron of this instrument run so heavily and hard over the seafloor that it destroys the flowers of the underwater land as well as the spat of oysters etc., upon which the fish feed…” Pp.131-132, Roberts (2007) The Unnatural History of the Sea  Bottom trawling as destructive fishing gear Often disputed by some… their “research shows no measurable negative impacts” on seafloor habitat... How far back in time does their study go? – See: Hilborn R, Amoroso R, Collie J, Hiddink JG, Kaiser MJ, Mazor T, McConnaughey RA, Parma AM, Pitcher CR, Sciberras M and Suuronen P (2023) Evaluating the sustainability and environmental impacts of trawling compared to other food production systems. ICES Journal of Marine Science. https://doi.org/10.1093/icesjms/fsad115 North Sea Pauly: Indonesian Sea 1970s Shifting baselines, see Pauly (1995) and lecture Watling and Norse (1998) Conservation Biology 12(6): 1180-1197 Kaiser et al. (2002) Fish and Fisheries 3: 114-136 Pauly (1995) TREE 10: 430 Fishing gear… massive range and diversity across space and time 45/51 Cashion et al. (2018) Fisheries Research 206:57-64  Fishing gear… massive range and diversity across space and time FAO has datasets on fishing gears, and produces reports… But not harmonized with or integrated across FAO databases Cannot query FAO data for catch by gear type…. 46/51 Cashion et al. (2018) Fisheries Research 206:57-64  Sea Around Us categorization of fishing gear First attempt : Derived broad taxon-gear % associations across regions/globally Worked at broad scale, but had distinct errors at country levels (not country specific): – UAE trawling, despite enforced trawl ban Associations not readily modifiable at database code level… abandoned approach in early 2010s Watson et al. (2006a) Fisheries Research 79: 97-102 47/51 Watson et al. (2006b) Fisheries Research 79: 103-111  Sea Around Us categorization of fishing gear Second attempt: Derived gear categories by fishing country, taxon, year and the area of fishing Is far more country-specific and modifiable 48/51 Cashion et al. (2018) Fisheries Research 206:57-64  Sea Around Us categorization of fishing gear 49/51 Cashion et al. (2018) Fisheries Research 206:57-64 Sea Around Us: Catch by gears Global total catch Global landed catch Global discarded catch 50/51 Cashion et al. (2018) Fisheries Research 206:57-64  Catch by gear types FAO data not harmonized or linked to gears Sea Around Us reconstructed catch by gear allows better examination of effects of fishing at any geographic scale Some issues with small-scale gears exist – Consistency of definition and assignment – Diversity of gears and names – Multi-gear nature of many small-scale fisheries – Being revised Alignment across other data parameters ongoing… e.g. fishing sectors 51/51  Homework: read….. Jarvis C and Brennan ML (2024) History of Trawling and Ecological Impact. pp. 9-25 In Jarvis C (ed.), Threats to Our Ocean Heritage: Bottom Trawling. Springer Nature Switzerland, Cham. https://doi.org/10.1007/978-3-031-57953- 0_2 Sea Around Us – Indian Ocean