Protected Species Bycatch Estimating Approaches: Estimating Harbor Porpoise Bycatch in U.S. Northwestern Atlantic Gillnet Fisheries

Orphanides, Christopher

doi:10.2960/j.v42.m647

Cited by 27 publications

(24 citation statements)

References 12 publications

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“…Examples are numerous and across taxa, including seabirds (Majluf et al, 2002;Winter et al, 2011;Gilman et al, 2016a), marine mammals (Majluf et al, 2002;Orphanides, 2009;Redfern et al, 2013;Martin et al, 2015), sharks (Walsh and Kleiber, 2001;Minami et al, 2007), and sea turtles (Murray, 2009(Murray, , 2011. GAMMs in this study resulted in the highest explanatory power for the probability of bycatch of loggerhead turtles in the Pacific, with the least explanatory ability for leatherback bycatch in the Atlantic.…”

Section: Value Of Statistical Models For Bycatch Predictionmentioning

confidence: 93%

Sea Turtle Bycatch Mitigation in U.S. Longline Fisheries

et al. 2017

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Capture of sea turtles in longline fisheries has been implicated in population declines of loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) turtles. Since 2004, United States (U.S.) longline vessels targeting swordfish and tunas in the Pacific and regions in the Atlantic Ocean have operated under extensive fisheries regulations to reduce the capture and mortality of endangered and threatened sea turtles. We analyzed 20 + years of longline observer data from both ocean basins during periods before and after the regulations to assess the effectiveness of the regulations. Using generalized additive mixed models (GAMMs), we investigated relationships between the probability of expected turtle interactions and operational components such as fishing location, hook type, bait type, sea surface temperature, and use of light sticks. GAMMs identified a two to three-fold lower probability of expected capture of loggerhead and leatherback turtle bycatch in the Atlantic and Pacific when circle hooks are used (vs. J hook). Use of fish bait (vs. squid) was also found to significantly reduce the capture probability of loggerheads in both ocean basins, and for leatherbacks in the Atlantic only. Capture probabilities are lowest when using a combination of circle hook and fish bait. Influences of light sticks, hook depth, geographic location, and sea surface temperature are discussed specific to species and regions. Results confirmed that in two U.S.-managed longline fisheries, rates of sea turtle bycatch significantly declined after the regulations. In the Atlantic (all regions), rates declined by 40 and 61% for leatherback and loggerhead turtles, respectively, after the regulations. Within the NED area alone, where additional restrictions include a large circle hook (18/0) and limited use of squid bait, rates declined by 64 and 55% for leatherback and loggerhead turtles, respectively. Gains were even more pronounced for the Pacific shallow set fishery, where mean bycatch rates declined by 84 and 95%, for leatherback and loggerhead turtles, respectively, for the post-regulation period. Similar management approaches could be used within regional fisheries management organizations to reduce capture of sea turtles and to promote sustainable fisheries on a global scale.

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Section: Value Of Statistical Models For Bycatch Predictionmentioning

confidence: 93%

Sea Turtle Bycatch Mitigation in U.S. Longline Fisheries

et al. 2017

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Section: Contribution To the Theme Section 'Techniques For Reducing Bmentioning

confidence: 99%

“…The mechanism(s) by which cetaceans become entangled in gillnets are not well understood, but one hypothesis is that animals are unable to detect gillnets at sufficient distance to avoid them. Several studies have aimed to reduce cetacean bycatch in gillnets by increasing the acoustic reflectivity of the nets (Dawson 1994, Northridge et al 2003, Trippel et al 2003, Larsen et al 2007, most recently by the addition of materials such as barium sulphate (BaSO 4 ) or iron oxide (FeO) to increase the target strength of the nylon mesh of the gillnet webbing.To date, 2 trials have shown a significant reduction in harbour porpoise Phocoena phocoena bycatch rates in 'acoustically reflective' gillnets (Larsen et al 2007), but a third trial found no such reduction (Northridge et al 2003). The results obtained by Larsen et al (2007) and Trippel et al (2009) appear promising, but the mechanism by which bycatch was reduced in these studies remains unclear.…”

mentioning

confidence: 99%

Franciscana bycatch is not reduced by acoustically reflective or physically stiffened gillnets

Bordino¹,

Mackay²,

Werner³

et al. 2013

Endang. Species. Res.

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The incidental capture of franciscana Pontoporia blainvillei in gillnet fisheries of Argentina, Uruguay and Brazil represents a major conservation threat to this species. We report on an experimental trial that compared franciscana bycatch rates in standard gillnets to gillnets with 1 of 2 modifications: increased acoustic reflectivity by infusion of barium sulphate (BaSO 4 ) or increased flexural stiffness of the nylon twine. Field trials were conducted in association with artisanal fishermen at San Clemente del Tuyu in Bahia Samborombon, Argentina, between October 2009 and March 2010. Depth sensors were used to record the underwater fishing behaviour of the 3 net types. Seventy-seven dolphins were observed incidentally captured in 807 monitored gillnet hauls, with similar fishing effort observed for each net type. There was no significant difference in franciscana bycatch rates (p > 0.05) or target fish catches (p > 0.05) among the 3 net types. The stiff net twine had a slightly but significantly higher flexural stiffness (FS) than the reflective or control net twine. The FS of the dry stiff twine was similar to that previously reported for BaSO 4 twine with a similar diameter; in contrast, the FS of the reflective nylon was, unexpectedly, much lower. However, the difference in the FS between wet, submerged stiff twine and control twine used in the field was estimated at 19.4%. The BaSO 4 net fished with a significantly lower mean float line height than either the control or stiffened net. These results show that the use of reflective or stiff nets does not lead to a reduction in franciscana bycatch rates; therefore, other management strategies need to be developed to reduce the impact of incidental captures of this species. KEY WORDS: Bycatch · Gillnet · Franciscana · Artisanal fishery Resale or republication not permitted without written consent of the publisher FREE REE ACCESS CCESS Contribution to the Theme Section 'Techniques for reducing bycatch of marine mammals in gillnets'Endang Species Res 21: [1][2][3][4][5][6][7][8][9][10][11][12] 2013 species is listed as Vulnerable by the IUCN (Reeves et al. 2008) and is considered to be the most threatened cetacean in the Southwest Atlantic (Secchi 2010). In coastal waters of Buenos Aires Province, Argentina, an estimated 650 dolphins are bycaught annually (Bordino & Albareda 2004). The most recent population estimate for this species in Argentinean waters is 14 000 individuals (Crespo et al. 2010), so it is unlikely that current bycatch levels are sustainable, and management measures are, therefore, urgently required to reduce the incidental bycatch of the species.The use of acoustic alarms has been shown to significantly reduce the bycatch rates of franciscana (Bordino et al. 2002) and other cetaceans in gillnets (Kraus et al. 1997, Carretta et al. 2008), but the financial cost of implementation and enforcement of pinger use limits their applicability in many smallscale fisheries (Read 2008). Concerns that the widespread use of acoustic alarms cou...

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“…These types of mutilations are thought to be a result of fi shermen's attempts to remove bycaught animals from gear, or to increase the possibility that the carcass would sink and not be recovered (or both) (Kuiken et al, 1994;Read and Murray, 2000). Most bycatch has been documented from New Jersey and north (Orphanides, 2009). However, data for the latest bycatch estimate were collected in February and March (Orphanides 5 ), whereas more harbor porpoise strandings in NC were recovered in April than in February and many of those strandings were positive for FI.…”

Section: Figure 6 (Continued)mentioning

confidence: 99%

“…Although harbor porpoises are known to be caught in gill nets (Orphanides, 2009), the number of HI-FI…”

Section: A B C D Ementioning

confidence: 99%

Strandings as indicators of marine mammal biodiversity and human interactions off the coast of North Carolina

Byrd

Hohn²,

Lovewell³

et al. 2014

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Abstract-The adjacency of 2 marine biogeographic regions off Cape Hatteras, North Carolina (NC), and the proximity of the Gulf Stream result in a high biodiversity of species from northern and southern provinces and from coastal and pelagic habitats. We examined spatiotemporal patterns of marine mammal strandings and evidence of human interaction for these strandings along NC shorelines and evaluated whether the spatiotemporal patterns and species diversity of the stranded animals reflected published records of populations in NC waters.

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Protected Species Bycatch Estimating Approaches: Estimating Harbor Porpoise Bycatch in U.S. Northwestern Atlantic Gillnet Fisheries

Cited by 27 publications

References 12 publications

Sea Turtle Bycatch Mitigation in U.S. Longline Fisheries

Sea Turtle Bycatch Mitigation in U.S. Longline Fisheries

Franciscana bycatch is not reduced by acoustically reflective or physically stiffened gillnets

Strandings as indicators of marine mammal biodiversity and human interactions off the coast of North Carolina

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