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C C Monteiro - One of the best experts on this subject based on the ideXlab platform.
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hake merluccius merluccius l 1758 Ghost Fishing by gill nets off the algarve southern portugal
Fisheries Research, 2003Co-Authors: M N Santos, H J Saldanha, Miguel B Gaspar, C C MonteiroAbstract:Abstract An experiment to study Ghost Fishing using a total of 27 monofilament gill nets in two trials was conducted between 2000 and 2002, approximately 6.5 miles off the city of Faro (Algarve, southern Portugal). The nets were set during spring and autumn, on a sandy-muddy Fishing ground at depths between 65 and 78 m, for European hake ( Merluccius merluccius ). They were set with one end cut loose to simulate lost nets. The hake catches (size, number and biomass) and biofouling (weight) from the twine of the deliberately lost nets were monitored over time, by using grapnel equipment to “creep” for and retrieve the nets in groups of three at sequential increasing intervals. The day before each net retrieval, three control nets were set in order to evaluate the changes in the catching efficiency of the lost nets over time. Similar patterns were observed in both trials, with a sharp decrease in the nets’ catching efficiency and an increase on the biofouling. Hake catches were initially comparable to those taken in normally fished gill nets in the area, but decreased steadily over time. Biofouling was strongly associated with declines in net catching efficiency. Under the conditions experienced in the study, the maximum Fishing lifetime of a “lost” gill net is 248 days, but showing negligible catches after 3 months. Based on an exponential model, we estimated that a 100 m length of gill net will catch is a maximum 87.6 hake, weighing 29.9 kg during this time. The study showed that hake “Ghost Fishing” represent only 0.5% of the total annual hake catches in the Algarve, and is considered to be a minor problem compared to discarding.
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An experimental study of gill net and trammel net 'Ghost Fishing' off the Algarve (southern Portugal)
Marine Ecology Progress Series, 1997Co-Authors: Karim Erzini, Pedro Monteiro, J. Ribeiro, M N Santos, Miguel B Gaspar, C C Monteiro, Teresa BorgesAbstract:Four 100 m lengths of both monofilament gill nets and trammel nets were deployed at depths between 15 and 18 m off the coast of the Algarve (south of Portugal) between April 1995 and June 1996. The nets were set on a natural rocky bottom with one end cut loose to simulate lost nets. Changes in net structure (net height, effective Fishing area, movement, colonisation, wear and tear) and their catches (species, sizes, numbers, and biomass) were monitored by divers. Similar patterns were observed in all the nets, with a sharp decrease in net height and effective Fishing area, and an increase in visibility within the first few weeks. Net movement was negligible except in the case of interference from other Fishing gears. Catch rates were initially comparable to normally fished gill nets and trammel nets in this area, but decreased steadily over time. No sea birds, reptiles or mammals were caught in any of the 8 nets. Catches were dominated by fish (89 % by number, at least 27 species), in particular by sea breams (Sparidae) and wrasses (Labridae). Under the conditions experienced throughout the study the Fishing Lifetime of a 'lost' net is between 15 and 20 wk. Based on an exponential model, we estimated that 100 m lengths of gill net and trammel net will catch 314 and 221 fish respectively over a 17 wk period. However, we consider this to be an underestimate due to high rates of predation and scavenging by octopuses, cuttlefish, moray eels, conger eels, and other fish such as the wrasse Coris julis. When the nets were surveyed in the following spring, 8 to 11 mo after being deployed, they were found to be completely destroyed or heavily colonised by algae and had become incorporated into the reef
Teresa Borges - One of the best experts on this subject based on the ideXlab platform.
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An experimental study of gill net and trammel net 'Ghost Fishing' off the Algarve (southern Portugal)
Marine Ecology Progress Series, 1997Co-Authors: Karim Erzini, Pedro Monteiro, J. Ribeiro, M N Santos, Miguel B Gaspar, C C Monteiro, Teresa BorgesAbstract:Four 100 m lengths of both monofilament gill nets and trammel nets were deployed at depths between 15 and 18 m off the coast of the Algarve (south of Portugal) between April 1995 and June 1996. The nets were set on a natural rocky bottom with one end cut loose to simulate lost nets. Changes in net structure (net height, effective Fishing area, movement, colonisation, wear and tear) and their catches (species, sizes, numbers, and biomass) were monitored by divers. Similar patterns were observed in all the nets, with a sharp decrease in net height and effective Fishing area, and an increase in visibility within the first few weeks. Net movement was negligible except in the case of interference from other Fishing gears. Catch rates were initially comparable to normally fished gill nets and trammel nets in this area, but decreased steadily over time. No sea birds, reptiles or mammals were caught in any of the 8 nets. Catches were dominated by fish (89 % by number, at least 27 species), in particular by sea breams (Sparidae) and wrasses (Labridae). Under the conditions experienced throughout the study the Fishing Lifetime of a 'lost' net is between 15 and 20 wk. Based on an exponential model, we estimated that 100 m lengths of gill net and trammel net will catch 314 and 221 fish respectively over a 17 wk period. However, we consider this to be an underestimate due to high rates of predation and scavenging by octopuses, cuttlefish, moray eels, conger eels, and other fish such as the wrasse Coris julis. When the nets were surveyed in the following spring, 8 to 11 mo after being deployed, they were found to be completely destroyed or heavily colonised by algae and had become incorporated into the reef
M N Santos - One of the best experts on this subject based on the ideXlab platform.
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hake merluccius merluccius l 1758 Ghost Fishing by gill nets off the algarve southern portugal
Fisheries Research, 2003Co-Authors: M N Santos, H J Saldanha, Miguel B Gaspar, C C MonteiroAbstract:Abstract An experiment to study Ghost Fishing using a total of 27 monofilament gill nets in two trials was conducted between 2000 and 2002, approximately 6.5 miles off the city of Faro (Algarve, southern Portugal). The nets were set during spring and autumn, on a sandy-muddy Fishing ground at depths between 65 and 78 m, for European hake ( Merluccius merluccius ). They were set with one end cut loose to simulate lost nets. The hake catches (size, number and biomass) and biofouling (weight) from the twine of the deliberately lost nets were monitored over time, by using grapnel equipment to “creep” for and retrieve the nets in groups of three at sequential increasing intervals. The day before each net retrieval, three control nets were set in order to evaluate the changes in the catching efficiency of the lost nets over time. Similar patterns were observed in both trials, with a sharp decrease in the nets’ catching efficiency and an increase on the biofouling. Hake catches were initially comparable to those taken in normally fished gill nets in the area, but decreased steadily over time. Biofouling was strongly associated with declines in net catching efficiency. Under the conditions experienced in the study, the maximum Fishing lifetime of a “lost” gill net is 248 days, but showing negligible catches after 3 months. Based on an exponential model, we estimated that a 100 m length of gill net will catch is a maximum 87.6 hake, weighing 29.9 kg during this time. The study showed that hake “Ghost Fishing” represent only 0.5% of the total annual hake catches in the Algarve, and is considered to be a minor problem compared to discarding.
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An experimental study of gill net and trammel net 'Ghost Fishing' off the Algarve (southern Portugal)
Marine Ecology Progress Series, 1997Co-Authors: Karim Erzini, Pedro Monteiro, J. Ribeiro, M N Santos, Miguel B Gaspar, C C Monteiro, Teresa BorgesAbstract:Four 100 m lengths of both monofilament gill nets and trammel nets were deployed at depths between 15 and 18 m off the coast of the Algarve (south of Portugal) between April 1995 and June 1996. The nets were set on a natural rocky bottom with one end cut loose to simulate lost nets. Changes in net structure (net height, effective Fishing area, movement, colonisation, wear and tear) and their catches (species, sizes, numbers, and biomass) were monitored by divers. Similar patterns were observed in all the nets, with a sharp decrease in net height and effective Fishing area, and an increase in visibility within the first few weeks. Net movement was negligible except in the case of interference from other Fishing gears. Catch rates were initially comparable to normally fished gill nets and trammel nets in this area, but decreased steadily over time. No sea birds, reptiles or mammals were caught in any of the 8 nets. Catches were dominated by fish (89 % by number, at least 27 species), in particular by sea breams (Sparidae) and wrasses (Labridae). Under the conditions experienced throughout the study the Fishing Lifetime of a 'lost' net is between 15 and 20 wk. Based on an exponential model, we estimated that 100 m lengths of gill net and trammel net will catch 314 and 221 fish respectively over a 17 wk period. However, we consider this to be an underestimate due to high rates of predation and scavenging by octopuses, cuttlefish, moray eels, conger eels, and other fish such as the wrasse Coris julis. When the nets were surveyed in the following spring, 8 to 11 mo after being deployed, they were found to be completely destroyed or heavily colonised by algae and had become incorporated into the reef
Matt K. Broadhurst - One of the best experts on this subject based on the ideXlab platform.
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Effects of twine material on the marine debris and relative Ghost Fishing of portunid hoop (tangle) nets
Aquaculture and Fisheries, 2019Co-Authors: Matt K. Broadhurst, Russell B. MillarAbstract:Abstract Portunids are important to recreational fisheries in Australia and typically are harvested by baited gears. Most of these baited gears are considered environmentally benign, although small conical hoop (tangle) nets fished in southeastern Australia sometimes are damaged and lose twine, which becomes marine debris. Substituting conventional multifilament polyamide (PA) twine with alternative multi-monofilament and monofilament PA twines in hoop nets can dramatically reduce marine debris, but there remain unanswered questions concerning the relative Fishing power of alternative twines among derelict hoop nets. This study addresses the shortfall in data by comparing the efficiencies and damage to replicate hoop nets made from the three twines and left to fish for short (one and two days), medium (three to five days) and long (ten and fourteen days) soaks. Irrespective of twine material or soak time, all hoop nets entangled the same numbers of giant mud crabs, Scylla serrata implying catch saturation within two days. Only four other animals were caught (all yellowfin bream, Acanthopagrus australis) and all died. At least some replicates of all hoop nets were damaged and lost twine, but this was greatest among the multifilament (up to a maximum of 9.3 m hoop-net deployment−1), followed by the multi-monofilament (up to 7.4 m hoop-net deployment−1) and monofilament hoop nets (1.4 m hoop-net deployment−1). Replacing the existing multifilament twine in hoop nets with monofilament when targeting S. serrata would maintain catches and minimise marine debris during conventional soaks, without increasing Ghost Fishing over the short term.
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Relative Ghost Fishing of portunid traps with and without escape gaps
Fisheries Research, 2018Co-Authors: Matt K. Broadhurst, Russell B. MillarAbstract:Abstract Owing to concerns about derelict portunid traps perpetually Fishing (‘Ghost Fishing’) in southeastern Australia, the utility of escape gaps for minimising temporal catching efficiencies, and damage and mortality, among key species was investigated. Replicate baited traps with (i) no escape gaps (‘conventional’), (ii) three escape gaps (‘escape-gap’ traps), or (iii) three holes where escape gaps would have been if they were biodegradable (‘open-hole’ traps) were deployed and retrieved after short (one and two weeks), medium (four and six weeks) and long soaks (eight and 10 weeks). No trap had bait remaining after any soak. Total catches comprised 17 species, but 70% was blue swimmer crabs, Portunus armatus—most (78%) of which were smaller than a proposed new legal size (≥65 mm carapace length). Many (62%) P. armatus were injured (typically missing one or two appendages), but had few mortalities (total of 5%). Compared to conventional traps, the escape-gap and open-hole traps retained significantly fewer undersized P. armatus across all soaks (by 93 and 96%) and there were less total injuries (by 86 and 97%) and mortalities trap–1 (by 80 and 85%). Irrespective of the trap, catches of total and undersized P. armatus and injuries trap–1 were greater after short (all by up to 3×) than medium or long soaks. Several traps had broken mesh bars, which was negatively associated with P. armatus catches and injuries. Only three other species had mortalities (n = 7). The data support using escape gaps for minimising Ghost Fishing among derelict portunid traps.
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Relative efficiencies and durabilities of recreational hoop- and lift-nets targeting two Australian portunids
Fisheries Research, 2016Co-Authors: Matt K. Broadhurst, Paul B. Butcher, Russell B. MillarAbstract:Abstract The temporal efficiencies and durabilities of established and alternative recreational portunid crab ( Scylla serrata and Portunus pelagicus ) baited nets were assessed during two experiments (simulating conventional and ‘Ghost’ Fishing) with the objective of minimising environmental impacts. The established gear (‘hoop nets’) comprised a circular panel of large, thin-twined mesh designed to entangle portunids while approaching a centrally located bait. The alternative gear (‘lift net’) had an identical diameter and central bait, but instead of entangling catches, comprised thicker, smaller meshes that were raised in a barrier during retrieval to prevent egress. Both gears similarly caught more portunids during nocturnal than diurnal deployments. When actively fished (i.e. retrieved every 30 min), lift nets were equally effective as hoop nets for catching S. serrata (and caused less exoskeleton damage—mostly limb loss) and more than twice as effective for P. pelagicus (attributed in part to broader size selection). Lift nets were minimally damaged, but irrespective of the deployment duration, all hoop nets had broken/missing meshes (lost as marine debris), and those left for up to 12 days quickly became non-functional. The results illustrate the utility of simply substituting problematic gears—instead of attempting their modification—with those that are inherently more benign to reduce environmental impacts.
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Mitigating unaccounted Fishing mortality from gillnets and traps
Fish and Fisheries, 2013Co-Authors: Sebastian S. Uhlmann, Matt K. BroadhurstAbstract:Gillnets and traps often are considered to have fewer holistic environmental impacts than active Fishing gears. However, in addition to the targeted catches, gillnets and traps still cause unwanted mortalities due to (i) discarding, (ii) Ghost Fishing of derelict gear, (iii) depredation, (iv) escaping or dropping out of gear, (v) habitat damage, and potentially (vi) avoiding gear and predation and (vii) infection of injuries sustained from most of the above. Population-level concerns associated with such ‘unaccounted Fishing mortalities’ from gillnets and traps have been sufficient to warrant numerous attempts at mitigation. In this article, we reviewed relevant research efforts, locating 130 studies in the primary literature that concomitantly quantified mortalities and their resolution through technical modifications, with the division of effort indicating ongoing concerns. Most studies (85) have focused on discard mortality, followed by Ghost-Fishing (24), depredation (10) and escape (8) mortalities. The remaining components have been poorly studied (3). All problematic mortality components are affected by key biological (e.g. species), technical (e.g. Fishing mechanisms) and/or environmental (e.g. temperature) factors. We propose that these key factors should be considered as part of a strategy to reduce impacts of these gears by first assessing modifications within and then beyond conventional configurations, followed by changes to operational and handling practices. Justification for this three-tiered approach is based not only on the potential for cumulative reduction benefits, but also on the likely ease of adoption, legislation and compliance.
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Giant mud crab (Scylla serrata): relative efficiencies of common baited traps and impacts on discards
ICES Journal of Marine Science, 2012Co-Authors: Paul A. Butcher, Matt K. Broadhurst, Jesse C. Leland, Brian D. Paterson, David G. MayerAbstract:This study was initiated in response to a scarcity of data on the efficiency, selectivity and discard mortality of baited traps to target Scylla serrata. Five replicates of four traps, including "hoop nets", rigid "wire pots", and collapsible "round" and "rectangular" pots were deployed for 3, 6 and 24 h in two Australian estuaries. Trapped S. serrata were "discarded" into cages and monitored with controls over 3 d. All S. serrata were assessed for damage, while subsets of immediately caught and monitored individuals had haemolymph constituents quantified as stress indices. All traps retained similar-sized (8.119.1 cm carapace width) S. serrata, with catches positively correlated to deployment duration. Round pots were the most efficient for S. serrata and fishmostly Acanthopagrus australis (3 mortality). Hoop nets were the least efficient and were often damaged. No S. serrata died, but 18 were wounded (biased towards hoop nets), typically involving a missing swimmeret. Physiological responses were mild and mostly affected by biological factors. The results validate discarding unwanted S. serrata for controlling exploitation, but larger mesh sizes or escape vents in pots and restrictions on hoop nets would minimise unnecessary catches, pollution and Ghost Fishing. © 2012 International Council for the Exploration of the Sea. Published by Oxford University Press. All rights reserved.
Henrique N. Cabral - One of the best experts on this subject based on the ideXlab platform.
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Trammel nets’ Ghost Fishing off the Portuguese central coast
Fisheries Research, 2009Co-Authors: Filipa Baeta, Maria Jose Costa, Henrique N. CabralAbstract:Abstract The loss of Fishing gear has negative consequences to marine communities if the gear preserves its catching abilities for a significant period, a phenomenon called “Ghost Fishing”. The present study assessed the impact of lost trammel nets in both sandy and rocky bottoms in the central area of the Portuguese coast. Ten trammel nets, each 50 m long and corresponding to the most common type used by the local commercial fleet, were allowed to fish continually for 285 days. During this time, changes in the structure and catching ability of each net were monitored by scuba divers in regular time intervals (1, 5, 10, 15, 20, 30, 40, 60, 80, 120, 250 and 285 days). Three control nets were also set in each bottom type the day before each monitoring dive. Irrespective of bottom type, nets’ Fishing area decreased to about 40% during the first 30 days, and then gradually (rocky bottoms) or sharply (sandy bottoms). It was estimated that during the experiment 541 and 257 individuals were caught per 100 m of net in rocky and sandy bottoms, respectively. Catching efficiency decreased in a negative exponential manner in parallel with the nets deterioration. The nets’ effective Fishing lifetime, when catching efficiency became lower than 1%, was 10–11 months in the rocky bottom and 8 months in the sandy bottom.