scholarly journals Climate driven spatiotemporal variations in seabird bycatch hotspots and implications for seabird bycatch mitigation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rujia Bi ◽  
Yan Jiao ◽  
Joan A. Browder
Keyword(s):  
Gulf Stream ◽  
Spatiotemporal Patterns ◽  
Seabird Species ◽  
Advanced Planning ◽  
Physical Barriers ◽  
Pelagic Longline Fishery ◽  
Bayesian Approximation ◽  
Fishing Fleets ◽  
North Wall ◽  
National Marine Fisheries Service

AbstractBycatch in fisheries is a major threat to many seabird species. Understanding and predicting spatiotemporal changes in seabird bycatch from fisheries might be the key to mitigation. Inter-annual spatiotemporal patterns are evident in seabird bycatch of the U.S. Atlantic pelagic longline fishery monitored by the National Marine Fisheries Service Pelagic Observer Program (POP) since 1992. A newly developed fast computing Bayesian approximation method provided the opportunity to use POP data to understand spatiotemporal patterns, including temporal changes in location of seabird bycatch hotspots. A Bayesian model was developed to capture the inherent spatiotemporal structure in seabird bycatch and reduce the bias caused by physical barriers such as coastlines. The model was applied to the logbook data to estimate seabird bycatch for each longline set, and the mid-Atlantic bight and northeast coast were the fishing areas with the highest fleet bycatch estimate. Inter-annual changes in predicted bycatch hotspots were correlated with Gulf Stream meanders, suggesting that predictable patterns in Gulf Stream meanders could enable advanced planning of fishing fleet schedules and areas of operation. The greater the Gulf Stream North Wall index, the more northerly the seabird bycatch hotspot two years later. A simulation study suggested that switching fishing fleets from the hindcasted actual bycatch hotspot to neighboring areas and/or different periods could be an efficient strategy to decrease seabird bycatch while largely maintaining fishers’ benefit.

Long-term climate ocean oscillations inform seabird bycatch from pelagic longline fishery

2020 ◽  
Vol 77 (2) ◽  
pp. 668-679
Author(s):  
Rujia Bi ◽  
Yan Jiao ◽  
Haakon Bakka ◽  
Joan A Browder
Keyword(s):  
Gulf Stream ◽  
Marine Conservation ◽  
Longline Fishery ◽  
Spatial Correlation Function ◽  
Annual Variations ◽  
The Us ◽  
Physical Barriers ◽  
Pelagic Longline Fishery ◽  
Barrier Model ◽  
Pelagic Longline

Abstract Seabirds are facing increasing threats in both marine and terrestrial habitats, and many populations have experienced dramatic declines over past decades. Fisheries bycatch is the most pervasive at-sea threat and is of increasing concern in fisheries management and marine conservation. We predicted spatial and temporal heterogeneities of seabird bycatch probability in the US Atlantic pelagic longline fishery (PLL) through an interactive Barrier model based on observer data from the National Marine Fisheries Service Pelagic Observer Program. The Barrier model prevents bias caused by physical barriers such as coastlines by defining the spatial correlation function as a collection of paths between points and eliminating any paths across physical barriers. The integrated nested Laplace approximations methodology and stochastic partial differential equations approach were applied to fit the model, greatly reducing execution time. Seabird bycatch had a hotspot of high bycatch probability in the mid-Atlantic bight in most years, and the hotspot varied in presence and location yearly. The inter-annual variations in bycatch hotspot are correlated with Gulf Stream meanders. Special area and time fishing restrictions predicted by relationships with Gulf Stream positions might enable the US Atlantic PLL to avoid peak areas and periods of seabird bycatch and thereby support seabird conservation.

scholarly journals An extraordinary breach of the Gulf Stream north wall by a cold water intrusion

2002 ◽  
Vol 29 (15) ◽  
pp. 8-1-8-4 ◽  
Author(s):  
Xiaofeng Li ◽  
Timothy F. Donato ◽  
Quanan Zheng ◽  
William G. Pichel ◽  
Pablo Clemente-Colón
Keyword(s):  
Gulf Stream ◽  
Cold Water ◽  
Water Intrusion ◽  
North Wall

scholarly journals The Icelandic Low as a Predictor of the Gulf Stream North Wall Position

2016 ◽  
Vol 46 (3) ◽  
pp. 817-826 ◽  
Author(s):  
Alejandra Sanchez-Franks ◽  
Sultan Hameed ◽  
Robert E. Wilson
Keyword(s):  
Gulf Stream ◽  
Southern Oscillation ◽  
Time Lags ◽  
Grand Banks ◽  
The North ◽  
Cape Hatteras ◽  
Pressure Anomaly ◽  
Icelandic Low ◽  
North Wall ◽  
Wall Position

AbstractThe Gulf Stream’s north wall east of Cape Hatteras marks the abrupt change in velocity and water properties between the slope sea to the north and the Gulf Stream itself. An index of the north wall position constructed by Taylor and Stephens, called Gulf Stream north wall (GSNW), is analyzed in terms of interannual changes in the Icelandic low (IL) pressure anomaly and longitudinal displacement. Sea surface temperature (SST) composites suggest that when IL pressure is anomalously low, there are lower temperatures in the Labrador Sea and south of the Grand Banks. Two years later, warm SST anomalies are seen over the Northern Recirculation Gyre and a northward shift in the GSNW occurs. Similar changes in SSTs occur during winters in which the IL is anomalously west, resulting in a northward displacement of the GSNW 3 years later. Although time lags of 2 and 3 years between the IL and the GSNW are used in the calculations, it is shown that lags with respect to each atmospheric variable are statistically significant at the 5% level over a range of years. Utilizing the appropriate time lags between the GSNW index and the IL pressure and longitude, as well as the Southern Oscillation index, a regression prediction scheme is developed for forecasting the GSNW with a lead time of 1 year. This scheme, which uses only prior information, was used to forecast the GSNW from 1994 to 2015. The correlation between the observed and forecasted values for 1994–2014 was 0.60, significant at the 1% level. The predicted value for 2015 indicates a small northward shift of the GSNW from its 2014 position.

scholarly journals Impact of the Atlantic Meridional Mode on Gulf Stream North Wall Position

2018 ◽  
Vol 31 (21) ◽  
pp. 8875-8894 ◽  
Author(s):  
Sultan Hameed ◽  
Christopher L. P. Wolfe ◽  
Lequan Chi
Keyword(s):  
Gulf Stream ◽  
Cold Water ◽  
Meridional Overturning Circulation ◽  
Major Influence ◽  
Tropical Atlantic ◽  
The North ◽  
Meridional Mode ◽  
North Wall ◽  
Atlantic Meridional Mode ◽  
Wall Position

The path of the Gulf Stream as it leaves the continental shelf near Cape Hatteras is marked by a sharp gradient in ocean temperature known as the North Wall. Previous work in the literature has considered processes related to the North Atlantic Oscillation (NAO) in triggering latitudinal displacements of the North Wall position. This paper presents evidence that the Atlantic meridional mode (AMM) also impacts interannual variations of the North Wall position. The AMM signal from the tropics propagates to the Gulf Stream near the 200-m depth, and there are two time scales for this interaction. Anomalous Ekman suction induced by AMM cools the tropical Atlantic. The cold water in the Caribbean Sea is entrained into the currents feeding the Gulf Stream, and this cooling signal reaches the North Wall within a year. A second mechanism involves cold anomalies in the western tropical Atlantic, which initially propagate westward as baroclinic planetary waves, reaching the Gulf Stream and resulting in a southward shift in the North Wall position after a delay of about one year. In an analysis for the period 1961–2015, AMM’s signal dominates North Wall fluctuations in the upper 300 m, while NAO is the major influence below ~500 m; the influence of both the teleconnections is seen between 300 and 500 m. The relationship between the Atlantic meridional overturning circulation (AMOC) and the North Wall is investigated for the 2005–15 period and found to be statistically significant only at the sea surface in one of the three North Wall indices used.

Observations of cross-frontal exchange associated with submesoscale features along the North Wall of the Gulf Stream

2020 ◽  
Vol 163 ◽  
pp. 103342
Author(s):  
Alejandra Sanchez-Rios ◽  
R. Kipp Shearman ◽  
Jody Klymak ◽  
Eric D'Asaro ◽  
Craig Lee
Keyword(s):  
Gulf Stream ◽  
The North ◽  
North Wall

scholarly journals Interaction of Superinertial Waves with Submesoscale Cyclonic Filaments in the North Wall of the Gulf Stream

2018 ◽  
Vol 48 (1) ◽  
pp. 81-99 ◽  
Author(s):  
Daniel B. Whitt ◽  
Leif N. Thomas ◽  
Jody M. Klymak ◽  
Craig M. Lee ◽  
Eric A. D’Asaro
Keyword(s):  
Wave Propagation ◽  
Gulf Stream ◽  
Vertical Shear ◽  
Vertical Vorticity ◽  
Shear Structures ◽  
The North ◽  
Lagrangian Observations ◽  
Critical Layers ◽  
Balanced Flow ◽  
North Wall

AbstractHigh-resolution, nearly Lagrangian observations of velocity and density made in the North Wall of the Gulf Stream reveal banded shear structures characteristic of near-inertial waves (NIWs). Here, the current follows submesoscale dynamics, with Rossby and Richardson numbers near one, and the vertical vorticity is positive. This allows for a unique analysis of the interaction of NIWs with a submesoscale current dominated by cyclonic as opposed to anticyclonic vorticity. Rotary spectra reveal that the vertical shear vector rotates primarily clockwise with depth and with time at frequencies near and above the local Coriolis frequency f. At some depths, more than half of the measured shear variance is explained by clockwise rotary motions with frequencies between f and 1.7f. The dominant superinertial frequencies are consistent with those inferred from a dispersion relation for NIWs in submesoscale currents that depends on the observed aspect ratio of the wave shear as well as the vertical vorticity, baroclinicity, and stratification of the balanced flow. These observations motivate a ray tracing calculation of superinertial wave propagation in the North Wall, where multiple filaments of strong cyclonic vorticity strongly modify wave propagation. The calculation shows that the minimum permissible frequency for inertia–gravity waves is mostly greater than the Coriolis frequency, and superinertial waves can be trapped and amplified at slantwise critical layers between cyclonic vortex filaments, providing a new plausible explanation for why the observed shear variance is dominated by superinertial waves.

scholarly journals Aerial Observations of Symmetric Instability at the North Wall of the Gulf Stream

2018 ◽  
Vol 45 (1) ◽  
pp. 236-244 ◽  
Author(s):  
I. Savelyev ◽  
L. N. Thomas ◽  
G. B. Smith ◽  
Q. Wang ◽  
R. K. Shearman ◽  
...  
Keyword(s):  
Gulf Stream ◽  
The North ◽  
North Wall ◽  
Symmetric Instability

Fish Habitat: Essential Fish Habitat and Rehabilitation

1999 ◽  
Keyword(s):  
Fishery Management ◽  
Fish Habitat ◽  
The United States ◽  
Essential Fish Habitat ◽  
Management Planning ◽  
Fishing Fleets ◽  
Definition Of ◽  
National Marine Fisheries Service ◽  
Conservation And Management ◽  
Poor Management

<em>Abstract</em> .—Food production in the United States from ocean fisheries is leveling off after impressive growth in the 1970s and 1980s. Fishery officials project further gains through more effective regulation of harvests and reduced discarding of catch. In the longer term, however, the most important opportunity to boost production involves rehabilitating fishery habitats that have been damaged or lost because of poor management. Many thousand tons of additional seafood production can be “unlocked” for fishermen and consumers if habitats are restored. Changes in 1996 to the Magnuson- Stevens Fishery Conservation and Management Act (the Magnuson-Stevens Act) call for the mapping of these habitats and the inclusion of habitat concerns in fishery management planning. These new requirements, if properly implemented, will help focus the attention of fishermen and seafood consumers on what is being lost and what needs to be done to restore productivity. Although these requirements are a good first step, the rules and guidance for the new essential fish habitat (EFH) provisions are fundamentally flawed. For example, the rules to implement EFH provisions muddle the Magnuson-Stevens Act’s definition of EFH with numerous references to prey species and vague ecological ideas. Especially troubling is the introduction by the National Marine Fisheries Service through the rules of the concept of “contribution to a healthy ecosystem” as an apparent standard for delineating necessary amounts of EFH. In addition, it is important to remember that competition among fishing fleets is fierce, and the promise of these new habitat requirements could be lost if habitat concerns become enmeshed in the ongoing political battles for harvest allocations.

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