Synergy among oceanographic variability, fishery expansion, and longline catch composition in the central North Pacific Ocean

Woodworth‐Jefcoats, Phoebe A.; Polovina, Jeffrey J.; Drazen, Jeffrey C.

doi:10.7755/fb.116.3.2

Cited by 18 publications

(25 citation statements)

References 10 publications

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“…In the southern hemisphere, these more extensive hotspots were in consensus with the catch distribution, indicating that these productive areas are distributed southward and extend to more eastern areas. The predicted ecological map also identified high-quality habitats north of the Hawaiian Islands, providing a weighty evidence of an important local longline fishery as ascertained by Woodworth-Jefcoats, Polovina, and Drazen (2018), and two zonal barrens associated with the OMZ. In the tropical eastern Pacific, low dissolved oxygen values were found at depths between 100 and 900 m (Karstensen, Stramma, & Visbeck, 2008), which mostly coincide with the vertical movement range of bigeye tuna.…”

Section: Variation Of Spatial Distributionmentioning

confidence: 72%

Spatial variability of bigeye tuna habitat in the Pacific Ocean: Hindcast from a refined ecological niche model

Zhou

Cao

et al. 2020

Fisheries Oceanography

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Section: Variation Of Spatial Distributionmentioning

confidence: 72%

Spatial variability of bigeye tuna habitat in the Pacific Ocean: Hindcast from a refined ecological niche model

Zhou

Cao

et al. 2020

Fisheries Oceanography

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“…To establish these sizes, we used time-averaged (2006-2016, pooled) catch records from the Pacific Islands Region Observer Program, which since 2006 has recorded the size of every third fish caught by Hawaii's longline bigeye tuna fleet. Roughly 20% of this fishery's effort is observed, and observer records have been found to correlate well with vessel logbooks (Woodworth-Jefcoats et al, 2018). We binned observed sizes of fish caught into equally spaced logarithmic size classes as in therMizer (Scott et al, 2014;Edwards et al, 2017).…”

Section: Proportion Ofmentioning

confidence: 99%

“…Model input plankton densities are summed and temperatures averaged over the footprint of the Hawaii-based deep-set longline fishery targeting bigeye tuna: (Figure 1; Woodworth-Jefcoats et al, 2018). Across the CMIP5 models used, phytoplankton densities declined by an average of 6% by mid-century and 12% by 2100.…”

Section: Climate Forcing Variablesmentioning

confidence: 99%

“…These scenarios were chosen based in part on trends in effort of Hawaii's deep-set longline fishery. Over the logbook record, effort has risen more than five-fold from 8.4 million hooks set in 1995 to over 47 million hooks set in 2015 (Woodworth-Jefcoats et al, 2018). Fishing effort does not translate equally to fishing mortality, and therefore we consider 5F to be a fairly aggressive future fishing scenario.…”

Section: Scenarios Modeledmentioning

confidence: 99%

“…This fishery operates largely outside the United States EEZ, extending from equatorial waters to the northern limits of the North Pacific subtropical gyre (35-40 • N) and from the dateline to the outer limits of the California Current region (roughly 125 • W), excluding the eastern tropical Pacific's oxygen minimum zone (Figure 1). Yet, a sizeable portion of the fishery operates in waters with little to no international competition (Woodworth-Jefcoats et al, 2018). This means that local management measures have the potential to effect broad ecosystem change.…”

Section: Introductionmentioning

confidence: 99%

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Relative Impacts of Simultaneous Stressors on a Pelagic Marine Ecosystem

2019

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Climate change and fishing are two of the greatest anthropogenic stressors on marine ecosystems. We investigate the effects of these stressors on Hawaii's deep-set longline fishery for bigeye tuna (Thunnus obesus) and the ecosystem which supports it using a size-based food web model that incorporates individual species and captures the metabolic effects of rising ocean temperatures. We find that when fishing and climate change are examined individually, fishing is the greater stressor. This suggests that proactive fisheries management could be a particularly effective tool for mitigating anthropogenic stressors either by balancing or outweighing climate effects. However, modeling these stressors jointly shows that even large management changes cannot completely offset climate effects. Our results suggest that a decline in Hawaii's longline fishery yield may be inevitable. The effect of climate change on the ecosystem depends primarily upon the intensity of fishing mortality. Management measures which take this into account can both minimize fishery decline and support at least some level of ecosystem resilience.

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Patterns of depredation in the Hawai‘i deep‐set longline fishery informed by fishery and false killer whale behavior

et al. 2021

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False killer whales (Pseudorca crassidens) depredate bait and catch in the Hawai'i-based deepset longline fishery, and as a result, this species is hooked or entangled more than any other cetacean in this fishery. We analyzed data collected by fisheries observers and from satellite-linked transmitters deployed on false killer whales to identify patterns of odontocete depredation that could help fishermen avoid overlap with whales. Odontocete depredation was observed on˜6% of deep-set hauls across the fleet from 2004 to 2018. Model outcomes from binomial GAMMs suggested coarse patterns, for example, higher rates of depredation in winter, at lower latitudes, and with higher fishing effort. However, explanatory power was low, and no covariates were identified that could be used in a predictive context. The best indicator of depredation was the occurrence of depredation on a previous set of the same vessel. We identified spatiotemporal scales of this repeat depredation to provide guidance to fishermen on how far to move or how long to wait to reduce the probability of repeated interactions. The risk of depredation decreased with both space and time from a previous occurrence, with the greatest benefits achieved by moving˜400 km or wait-ing˜9 d, which reduced the occurrence of depredation from 18% to 9% (a 50% reduction). Fishermen moved a median 46 km and waited 4.7 h following an observed depredation interaction, which our analysis suggests is unlikely to lead to large reductions in risk. Satellite-tagged pelagic false killer whales moved up to 75 km in 4 h and 335 km in 24 h, suggesting that they can likely keep pace with longline vessels for at least four hours and likely longer. We recommend fishermen avoid areas of known depredation or bycatch by moving as far and as quickly as practical, especially within a day or two of the depredation or bycatch event. We also encourage captains to communicate depredation and bycatch occurrence to enable other vessels to similarly avoid high-risk areas.

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Synergy among oceanographic variability, fishery expansion, and longline catch composition in the central North Pacific Ocean

Cited by 18 publications

References 10 publications

Spatial variability of bigeye tuna habitat in the Pacific Ocean: Hindcast from a refined ecological niche model

Spatial variability of bigeye tuna habitat in the Pacific Ocean: Hindcast from a refined ecological niche model

Relative Impacts of Simultaneous Stressors on a Pelagic Marine Ecosystem

Patterns of depredation in the Hawai‘i deep‐set longline fishery informed by fishery and false killer whale behavior

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