scholarly journals Reduced herding of flounders by floating bridles: application in Gulf of Maine Northern shrimp trawls to reduce bycatch

2014 ◽  
Vol 72 (5) ◽  
pp. 1514-1524 ◽  
Author(s):  
Pingguo He ◽  
Christopher Rillahan ◽  
Vincent Balzano
Keyword(s):  
North Atlantic ◽  
Gulf Of Maine ◽  
Shrimp Fishery ◽  
The North ◽  
Northern Shrimp ◽  
Shrimp Fisheries ◽  
The Difference ◽  
Catch Rates ◽  
Silver Hake ◽  
Merluccius Bilinearis

Abstract We hypothesized that a floating trawl bridle that does not contact the seabed would reduce the herding of fish, especially bottom dwelling flounders, and thus reduce bycatch of these fish in shrimp trawls. We further hypothesized that, due to the non-herding nature of northern shrimp (Pandalus borealis), the use of an off-bottom floating bridle would not reduce shrimp catch. These hypotheses were tested in the field by comparing a trawl with regular bottom-tendering wire bridles and the same trawl with floating synthetic bridles in the Gulf of Maine northern shrimp fishery. As expected, no statistically significant differences in catch rates and size were found for the targeted northern shrimp (146.3 ± 10.58 kg h−1 control vs. 140.8 ± 9.35 kg h−1, p = 0.13). Total finfish bycatch was reduced by 14.9%, and the difference was statistically different (p = 0.01). The most important reduction was the catch of juvenile American plaice (Hippoglossoides platessoides) with a significant reduction of 20.0% (p = 0.01). For witch flounder (Glyptocephalus cynoglossus), a reduction of 19.3% was found, but it was not statistically significant (p = 0.14). The reduction of Acadian redfish (Sebastes fasciatus) (by 28.0%, p = 0.02) was also statistically different. Catch of targeted silver hake (Merluccius bilinearis) was reduced by 10.8%, but the difference was only marginally significant (p = 0.07). An analysis of length frequencies for the targeted shrimp and major bycatch species revealed no size-related selection between the gears with regular bridles and floating bridles. The reductions in flounder bycatch indicate reduced herding of benthic species when the bridles are kept off bottom. This easy modification may be readily adopted in the northern shrimp fisheries in the North Atlantic, and can also possibly be applied in other shrimp and prawn fisheries with further experimentation.

scholarly journals The paradox of constant oceanic plastic debris: evidence for evolved microbial biodegradation?

2017 ◽  
Author(s):  
Ricard Solé ◽  
Ernest Fontich ◽  
Blai Vidiella ◽  
Salva Duran-Nebreda ◽  
Raúl Montañez ◽  
...  
Keyword(s):  
North Atlantic ◽  
Nonlinear Coupling ◽  
Global Studies ◽  
Two Dimensional ◽  
Plastic Debris ◽  
The North ◽  
Microbial Biodegradation ◽  
The North Atlantic ◽  
The Difference ◽  
Microbial Model

Although the presence of vast amounts of plastic in the open ocean has generated great concern due to its potential ecological consequences, recent studies reveal that its measured abundance is much smaller than expected. Regional and global studies indicate that the difference between expected and actual estimates is enormous, suggesting that a large part of the plastic has been degraded by either physical and biotic processes. A paradoxical observation is the lack of a trend in plastic accumulation found in the North Atlantic Subtropical Gyre, despite the rapid increase in plastic production and disposal. In this paper we show, using mathematical and computer models, that this observation could be explained by the nonlinear coupling between plastic (as a resource) and an evolved set of organisms (the consumers) capable of degrading it. The result is derived using two different resource-consumer mathematical approaches as well as a spatially-dependent plastic-microbial model incorporating a minimal hydrodynamical coupling with a two-dimensional fluid. The potential consequences of the evolution of marine plastic garbage and its removal are outlined.

Behavioral inferences from regulatory observer data: catch rate variation in the Scotian Shelf silver hake (Merluccius bilinearis) fishery

1999 ◽  
Vol 56 (2) ◽  
pp. 288-296 ◽  
Author(s):  
D M Gillis
Keyword(s):  
Interference Competition ◽  
Temporal Trends ◽  
Catch Rate ◽  
Rate Variation ◽  
Scotian Shelf ◽  
Apparent Contradiction ◽  
Fishing Vessels ◽  
Catch Rates ◽  
Silver Hake ◽  
Merluccius Bilinearis

The detailed spatial and temporal data collected for the regulation of the silver hake (Merluccius bilinearis) fishery on the Scotian Shelf provide a unique opportunity to test hypotheses about variability in catch rates on the scale of individual trawls. I used these data to examine vessel interactions and long-term temporal trends in catchability. An index of course linearity, derived from observed positions, times, and speeds of fishing vessels, indicated that interference competition was present in the fishery. However, catch rate did not decline with local vessel density. This apparent contradiction is consistent with fleet dynamic theory and suggests that the direct examination of catch rates is a poor test for interference in the retrospective analysis of fisheries data. The study of extended periods of high, localized fishing activity revealed a cycle in catch rates with periods of about 6 days. Such periods may represent an interaction between tidal, diel, and (or) technological factors. Although more study is required to identify the cause of these cycles, their existence should be considered in the design of surveys and other population studies using catch and effort data.

Le controle du socle dans l'évolution de la sedimentation en Manche occidentale apres le Paléozoïque

1975 ◽  
Vol 279 (1288) ◽  
pp. 137-143 ◽  
Keyword(s):  
North Atlantic ◽  
Transverse Direction ◽  
Longitudinal Direction ◽  
The West ◽  
The North ◽  
The North Atlantic ◽  
The Difference ◽  
Cenozoic Sediments ◽  
Two Sides

The estimates of the thickness of the Mesozoic and Cenozoic sediments found in the western Channel show that the deposition of these sediments was controlled by two independent processes. (1) In the longitudinal direction, the displacement of maximum sedimentation, from east to west is entirely dependent on the opening of the North Atlantic. (2) In a transverse direction, it is probable that the difference of subsidence between the two sides of the Aurigny—Ouessant fault originated from the fracturing of the original Atlantic rift in the Western Approaches. Transverse compressions and extensions have disturbed the continual depression of the Channel towards the west.

A Unified Nonlinear Multiscale Interaction Model of Pacific–North American Teleconnection Patterns

2020 ◽  
Vol 77 (4) ◽  
pp. 1387-1414
Author(s):  
Dehai Luo ◽  
Yao Ge ◽  
Wenqi Zhang ◽  
Aiguo Dai
Keyword(s):  
North Atlantic ◽  
North American ◽  
Wave Train ◽  
Interaction Model ◽  
Energy Dispersion ◽  
Pacific North American ◽  
The North ◽  
The North Atlantic ◽  
The Difference ◽  
Multiscale Interaction

Abstract In this paper, reanalysis data are first analyzed to reveal that the individual negative (positive)-phase Pacific–North American pattern (PNA) or PNA− (PNA+) has a lifetime of 10–20 days, is characterized by strong (weak) westerly jet stream meanders, and exhibits clear wave train structures, whereas the PNA− with rapid retrogression tends to have longer lifetime and larger amplitude than the PNA+ with slow retrogression. In contrast, the wave train structure of the North Atlantic Oscillation (NAO) is less distinct, and the positive (negative)-phase NAO shows eastward (westward) movement around a higher latitude than the PNA. Moreover, it is found that the PNA wave train occurs under a larger background meridional potential vorticity gradient (PVy) over the North Pacific than that over the North Atlantic for the NAO. A unified nonlinear multiscale interaction (UNMI) model is then developed to explain why the PNA as a nonlinear wave packet has such characteristics and its large difference from the NAO. The model results reveal that the larger background PVy for the PNA (due to its location at lower latitudes) leads to its larger energy dispersion and weaker nonlinearity than the NAO, thus explaining why the PNA (NAO) is largely a linear (nonlinear) process with a strong (weak) wave train structure, though it is regarded as a nonlinear initial-value problem. The smaller PVy for the PNA− than for the PNA+ leads to lower energy dispersion and stronger nonlinearity for PNA−, which allows it to maintain larger amplitude and have a longer lifetime than the PNA+. Thus, the difference in the background PVy is responsible for the asymmetry between the two phases of PNA and the difference between the PNA and NAO.

scholarly journals Variations in the difference between mean sea level measured either side of Cape Hatteras and their relation to the North Atlantic Oscillation

2016 ◽  
Vol 49 (7-8) ◽  
pp. 2451-2469 ◽  
Author(s):  
P. L. Woodworth ◽  
M. Á. Morales Maqueda ◽  
W. R. Gehrels ◽  
V. M. Roussenov ◽  
R. G. Williams ◽  
...  
Keyword(s):  
North Atlantic Oscillation ◽  
Sea Level ◽  
North Atlantic ◽  
Mean Sea Level ◽  
The North ◽  
Cape Hatteras ◽  
The North Atlantic ◽  
The Difference ◽  
The North Atlantic Oscillation

An investigation of storm waves in the North Atlantic Ocean

1955 ◽  
Vol 230 (1183) ◽  
pp. 560-569 ◽  
Keyword(s):  
Wind Speed ◽  
Shallow Water ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Deep Ocean ◽  
The North ◽  
Storm Waves ◽  
The Difference ◽  
Tidal Streams ◽  
Wave Recorder

Since February 1953 the Ocean Weather Ship Weather Explorer , using a shipborne wave recorder, has taken records of waves at the positions ‘India’ (61° 00' N, 15° 20' W) and ‘Juliet’ (52° 20' N, 20° 00'W). An investigation of the records shows that conditions of wave generation in the deep ocean are different from those on the continental shelf. In both deep and shallow water, the steepness of the highest waves decreases as the fetch increases until an equilibrium value is reached after about 100 miles. In deep water this equilibrium value increases with the wind speed, whereas in shallow water it tends to decrease with wind speed. Different empirical rules are required for wave prediction in the deep ocean and the shallow sea. The difference can probably be attributed to a greater effect of turbulence near the coast, where the depth is of the same order as the wavelength and there are active tidal streams.

scholarly journals Reducing the catch of small shrimps in the Gulf of Maine pink shrimp fishery with a size-sorting grid device

2007 ◽  
Vol 64 (8) ◽  
pp. 1551-1557 ◽  
Author(s):  
Pingguo He ◽  
Vincent Balzano
Keyword(s):  
Gulf Of Maine ◽  
Marine Science ◽  
Grid System ◽  
Pink Shrimp ◽  
Pandalus Borealis ◽  
Shrimp Fishery ◽  
Trawl Fishery ◽  
Size Sorting ◽  
Catch Rates

Abstract He, P., and Balzano, V. 2007. Reducing the catch of small shrimps in the Gulf of Maine pink shrimp fishery with a size-sorting grid device. – ICES Journal of Marine Science, 64: 1551–1557. Since implementation of the Nordmøre grid in the Gulf of Maine pink shrimp (Pandalus borealis) trawl fishery in the early 1990s, fish bycatch has been reduced drastically. However, the Nordmøre grid does not reduce the amount of small shrimps landed when the shrimps are on the fishing grounds. This paper reports on two designs of a new size-sorting grid system, one with a funnel and one without. The designs' main feature is the size-sorting grid's position, installed in front of the main Nordmøre grid. They were tested in the flume tank and at sea. Parallel tows involving two vessels and alternating tows using one vessel were made to compare the size-sorting grid system. Both size-sorting designs reduced the number of small shrimps in the catch significantly, by 38 and 45 kg−1 of catch, respectively. There was some reduction in shrimp catch rates, presumably from the release of small shrimps. There were no significant differences in the number or quantity of major bycatch species for the commercial grid and the two experimental grid designs. The designs were practical to operate and easy to install. Their application could reduce the catch of small shrimps in the pink shrimp fishery in the Gulf of Maine and in other areas.

scholarly journals Interannual Variability of High-Wind Occurrence over the North Atlantic*

2011 ◽  
Vol 24 (24) ◽  
pp. 6515-6527 ◽  
Author(s):  
Xuhua Cheng ◽  
Shang-Ping Xie ◽  
Hiroki Tokinaga ◽  
Yan Du
Keyword(s):  
Interannual Variability ◽  
North Atlantic ◽  
Gulf Stream ◽  
Storm Track ◽  
Surface Air Temperature ◽  
High Wind ◽  
The North ◽  
The North Atlantic ◽  
The Difference ◽  
The North Atlantic Oscillation

Abstract Interannual variability of high-wind occurrence over the North Atlantic is investigated based on observations from the satellite-borne Special Sensor Microwave Imager (SSM/I). Despite no wind direction being included, SSM/I data capture major features of high-wind frequency (HWF) quite well. Climatology maps show that HWF is highest in winter and is close to zero in summer. Remarkable interannual variability of HWF is found in the vicinity of the Gulf Stream, over open sea south of Iceland, and off Cape Farewell, Greenland. On interannual scales, HWF south of Iceland has a significant positive correlation with the North Atlantic Oscillation (NAO). An increase in the mean westerlies and storm-track intensity during a positive NAO event cause HWF to increase in this region. In the vicinity of the Gulf Stream, HWF is significantly correlated with the difference between sea surface temperature and surface air temperature (SST − SAT), indicative of the importance of atmospheric instability. Cross-frontal wind and an SST gradient are important for the instability of the marine atmospheric boundary layer on the warm flank of the SST front. Off Cape Farewell, high wind occurs in both westerly and easterly tip jets. Quick Scatterometer (QuikSCAT) data show that variability in westerly (easterly) HWF off Cape Farewell is positively (negatively) correlated with the NAO.

Local and migratory movements of humpback whales (Megaptera novaeangliae) satellite-tracked in the North Atlantic Ocean

2014 ◽  
Vol 92 (1) ◽  
pp. 9-18 ◽  
Author(s):  
A.S. Kennedy ◽  
A.N. Zerbini ◽  
O.V. Vásquez ◽  
N. Gandilhon ◽  
P.J. Clapham ◽  
...  
Keyword(s):  
Dominican Republic ◽  
North Atlantic ◽  
Gulf Of Maine ◽  
North Atlantic Ocean ◽  
Megaptera Novaeangliae ◽  
Humpback Whales ◽  
The North ◽  
Breeding Grounds ◽  
Multiple Feeding ◽  
Feeding Grounds

North Atlantic humpback whales (Megaptera novaeangliae (Borowski, 1781)) migrate from high-latitude summer feeding grounds to low-latitude winter breeding grounds along the Antillean Island chain. In the winters and springs of 2008 through 2012, satellite tags were deployed on humpback whales on Silver Bank (Dominican Republic) and in Guadeloupe (French West Indies) breeding areas. Whales were monitored, on average, for 26 days (range = 4–90 days). Some animals remained near their tagging location for multiple days before beginning their northerly migration, yet some visited habitats along the northwestern coast of the Dominican Republic, northern Haiti, the Turks and Caicos islands, and off Anguilla. Individuals monitored during migration headed towards feeding grounds in the Gulf of Maine (USA), Canada, and the eastern North Atlantic (Iceland or Norway). One individual traveled near Bermuda during the migration. This study provides the first detailed description of routes used by North Atlantic humpback whales towards multiple feeding destinations. Additionally, it corroborates previous research showing that individuals from multiple feeding grounds migrate to the Antilles for the breeding season. This study indicates that North Atlantic humpbacks use an area broader than the existing boundaries of marine mammal sanctuaries, which should provide justification for their expansion.

Sign in / Sign up

Export Citation Format

Share Document