Daytime surface swarming by Meganyctiphanes norvegica (M. Sars) (Crustacea, Euphausiacea) off Brier Island, Bay of Fundy

1979 ◽  
Vol 57 (12) ◽  
pp. 2285-2291 ◽  
Author(s):  
R. G.B. Brown ◽  
S. P. Barker ◽  
D. E. Gaskin
Keyword(s):  
Spring Tide ◽  
Solar Irradiation ◽  
Food Sources ◽  
Subsurface Water ◽  
Gonad Maturation ◽  
Marine Predators ◽  
Vertical Turbulence ◽  
Meganyctiphanes Norvegica ◽  
Tidal Streams ◽  
Tide Period

In July–September the euphausiid Meganyctiphanes norvegica (M. Sars) swarms at the surface in daytime off Brier Island, Nova Scotia (ca. 44°15′ N 66°23′ W). Systematic observations of swarming were made, mainly in late August 1974, 1975, 1976, and 1978, supplemented in 1974 and 1975 by the frequency of occurrence of the euphatisiids in the proventriculi of collected greater shearwaters, Puffinus gravis (O'Reilly). Swarms, consisting mostly of immature animals, occurred near an area of turbulence where strong tidal streams ran up against steep underwater ledges, bringing cool subsurface water and also copepods to the surface. Swarming was apparently not an attempt to avoid underwater predators or unfavourable oceanographic conditions, nor was it a means of advancing gonad maturation through exposure to solar irradiation. Swarming was most common in spring tide periods when tidal streams were strongest, and did not occur at all during a neap tide period in late August 1975. It is suggested that M. norvegica swarms were transported passively to the surface by strong vertical turbulence. However, the possibility that they swam actively to the surface in search of copepods and other food passively transported in that way could not be ruled out. It is suggested that the surface swarming of Euphausia pacifica Hansen, the other well-documented survey of the phenomenon, by Y. Komaki in 1967, be reexamined in the light of these conclusions. The significance of surface swarms as food sources for a variety of marine predators is discussed.

scholarly journals Metabolic and enzymatic adaptations in northern krill,Meganyctiphanes norvegica, and Antarctic krill,Euphausia superba

2000 ◽  
Vol 57 (S3) ◽  
pp. 115-129 ◽  
Author(s):  
Friedrich Buchholz ◽  
Reinhard Saborowski
Keyword(s):  
Antarctic Krill ◽  
Citrate Synthase ◽  
Enzyme Regulation ◽  
Euphausia Superba ◽  
Food Sources ◽  
The Arctic ◽  
Ligurian Sea ◽  
Meganyctiphanes Norvegica ◽  
The Antarctic ◽  
Antarctic Krill Euphausia Superba

The Antarctic krill, Euphausia superba, is restricted to the Antarctic Ocean. The northern krill, Meganyctiphanes norvegica, is extremely widely distributed from the arctic North Atlantic to the warm Mediterranean. Respiration measurements showed no seasonal differences in rates determined in krill from the thermally stable Clyde Sea (Scotland) and the cooler but variable Danish Kattegat. In the warm Ligurian Sea, where temperatures are stable, krill showed higher rates in April than in September, indicating reactions to the short but intensive productive season. Krill can passively benefit from enhancements of overall metabolism when ascending into upper, warmer water strata during their pronounced diel vertical migration. Michaelis-Menten constants (Km) of citrate synthase (CS) were compared. In terms of respiration and enzyme regulation, krill from the Ligurian Sea stand apart: temperature and nutrition appear to be of different influence, relatable to genetic differentiation in the species. In contrast, Kmof CS in E. superba is temperature independent, highlighting the species' stenothermal physiology. A basal level of activity of digestive enzymes ensures immediate utilization of patchy food sources. Specific induction, including that of chitinases, indicating omnivory in both species, underlines krill's exceptional capacity to adapt to highly variable trophic environments. Processes of moult, growth, and reproduction are locally and seasonally adjusted.

scholarly journals Feeding dynamics and ecomorphology of Oligosarcus jenynsii (Gunther, 1864) and Oligosarcus robustus (Menezes, 1969) in the Lagoa Fortaleza, southern Brazil

2006 ◽  
Vol 66 (1a) ◽  
pp. 121-132 ◽  
Author(s):  
D. M. Nunes ◽  
S. M. Hartz
Keyword(s):  
Condition Factor ◽  
Liver Weight ◽  
Reproductive Period ◽  
Diet Analysis ◽  
Food Sources ◽  
Hepatosomatic Index ◽  
Gonad Maturation ◽  
Limiting Factor ◽  
Feeding Intensity ◽  
Mean Values

Oligosarcus jenynsii and Oligosarcus robustus are fishes of Characidae family that occur in Rio Grande do Sul, Uruguay and northern Argentina. This work purported to study the feeding dynamics (repletion and hepatosomatic indexes and condition factor) over time, and to investigate the coexistence of these two species by evaluating the partition of resources using qualitative and quantitative analyses of diet, temporal and spatial segregation throughout the water column and some ecomorphological aspects of the species in the Lagoa Fortaleza. Specimens were sampled monthly, from May 2000 to April 2001 during 24 h/month, using stationary gill nets of different mesh sizes. The records of each individual included total and standard length; total, stomach and liver weight; sex and stomach repletion. The variation of the mean values of repletion index and relative frequencies of stomach repletion stages indicate that O. jenynsii and O. robustus do not present seasonal differences in feeding intensity. The hepatosomatic index shows an allocation of energy to the liver during every period except reproduction, when part of the energy is used for gonad maturation. The estimated condition factor for both species reveals an increase in the reproductive period, evidencing the influence of gonads upon the condition of the fish. The diet analysis revealed that O. robustus is piscivorous, whereas O. jenynsii is a generalist carnivore, tending to piscivory as well. The active period of O. robustus is more concentrated at sunrise and sunset, whereas O. jenynsii is continually active, a characteristic related to hunting for prey. The ecomorphological analysis revealed differences between the two species in the dimensions of the mouth. Evidence suggests that the species coexist, sharing food sources, differing in oral morphology but ingesting similar prey, possibly because food is not a limiting factor in the environment.

scholarly journals Characteristics of Tidal Discharge and Phase Difference at a Tidal Channel Junction Investigated Using the Fluvial Acoustic Tomography System

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 857 ◽  
Author(s):  
Mochammad Meddy Danial ◽  
Kiyosi Kawanisi ◽  
Mohamad Basel Al Sawaf
Keyword(s):  
Phase Difference ◽  
Neap Tide ◽  
Spring Tide ◽  
Asymmetry Index ◽  
Acoustic Tomography ◽  
Tomography System ◽  
Tide Period ◽  
Flow Division ◽  
Cross Wavelet ◽  
Northern Branch

This study investigates the tidal discharge division and phase difference at branches connected to a channel junction. The tidal discharge at three branches (eastern, western, and northern branches) was continuously collected using the fluvial acoustic tomography system (FATS). The discharge asymmetry index was used to quantify the flow division between two seaward branches (eastern and western branches). The cross-wavelet method was applied to calculate the phase difference between the tidal discharge and water level. The discharge asymmetry index shows that the inequality of flow division is obviously prominent during the spring tide duration, where the eastern branch has the capability to deliver greater amounts of subtidal discharge, approximately 55–63%, compared with the western branch. However, the equality of flow division between the eastern and western channels can be observed clearly during the neap tide period. The wavelet analysis shows that the phase difference at the western branch is higher than at the eastern branch, because the geometry of the western branch is more convergent than that of the eastern branch. Accordingly, the amplitude of the tidal wave at the western branch is more magnified compared with that at the eastern branch. Moreover, the phase difference at the northern branch is greater than at the two seaward branches, implying that the phase difference is slightly increased after passing through the junction into the northern branch.

scholarly journals The mangrove forests as nursery habitats for the ichthyofauna of Mida Creek (Kenya, East Africa)

2014 ◽  
Vol 94 (5) ◽  
pp. 865-877 ◽  
Author(s):  
Laura Gajdzik ◽  
Ann Vanreusel ◽  
Nico Koedam ◽  
Jan Reubens ◽  
Agnes Wangui N. Muthumbi
Keyword(s):  
Isotope Analysis ◽  
Spring Tide ◽  
Fish Fauna ◽  
Size Composition ◽  
Stomach Content Analysis ◽  
Trophic Levels ◽  
Food Sources ◽  
Mangrove Forests ◽  
East African ◽  
Nursery Habitats

This study investigated the presumed nursery function of mangroves for the ichthyofauna in East African swamp forests, Mida Creek. The species and size composition of the fish fauna and their trophic interactions were studied for five stations. Samples were collected during 5–6 consecutive days close to spring tide in mid-July 2011. Fish were caught using different types of passive fishing gear, such as large and small fyke nets, gill nets and, additionally, beach seines. All individuals were identified to species level, measured and preserved for further analyses. Stomach content analysis was applied to provide information about their diet. Stable isotope analysis was used to detect whether the source of primary production for the higher trophic levels is mangrove-related or not. A total of 27 fish species was recorded in a catch of 938 teleost specimens. Our analyses showed that a majority of fish belonged to the zoobenthivorous/omnivorous trophic mode, since they were partially feeding on invertebrates and on various other food sources. Two species (Sphyraena barracuda and Synodus variegatus) exhibited a mixed diet, with a piscivorous preference. Results concerning the population structure suggested that the fish community of Mida mainly consists of transient species. Juveniles were numerically more abundant in the whole Creek than adults. These findings support the hypothesis of a nursery function of the mangrove forests, Mida Creek.

scholarly journals STUDY OF TRANSMISSION LOSS VARIATION AFFECTED BY INTERNAL TIDES IN THE SEA AREA NORTHEAST OF TAIWAN

2012 ◽  
Vol 20 (01) ◽  
pp. 1250002
Author(s):  
YUAN-YING CHANG ◽  
CHENG-KEN HUANG ◽  
CHI-FANG CHEN ◽  
SEN JAN
Keyword(s):  
Negative Correlation ◽  
Sound Propagation ◽  
Transmission Loss ◽  
Spring Tide ◽  
Mixing Layer ◽  
Internal Tide ◽  
Internal Tides ◽  
Underwater Sound ◽  
Sea Area ◽  
Tide Period

Internal tides can cause density and sound speed fluctuations in the ocean, and the thickness of the mixing layer can fluctuate in short periods of time. This phenomenon affects underwater sound propagation and induces transmission loss variations. In the sea area northeast of Taiwan, regular internal tide activity is observed. The topography and sediment there are also complex, which makes the effect on transmission loss by internal tides even more complicated. This paper studies how transmission loss variation is affected by internal tides in the sea area northeast of Taiwan. The hydrographic fields with influence from the internal tides are provided by an experiment survey on the 4th of September, 2008 and a 3-D tide model. The transmission loss comparison between different thicknesses of the mixing layer in the internal tide fields is shown. Furthermore, the correlation coefficient is calculated and shows that layer depth and transmission loss have a medium to high negative correlation in the upper water column during the summer spring-tide period, and a low to medium negative correlation during the summer neap-tide period.

scholarly journals Offshore Detachment Process of the Low-Salinity Water around Changjiang Bank in the East China Sea

2010 ◽  
Vol 40 (5) ◽  
pp. 1035-1053 ◽  
Author(s):  
Jae-Hong Moon ◽  
Naoki Hirose ◽  
Jong-Hwan Yoon ◽  
Ig-Chan Pang
Keyword(s):  
East China Sea ◽  
Tidal Current ◽  
Spring Tide ◽  
Vertical Mixing ◽  
East China ◽  
The East China Sea ◽  
Low Salinity ◽  
Low Salinity Water ◽  
Salinity Water ◽  
Tide Period

Abstract A patchlike structure of low-salinity water detached from the Chanjiang “Diluted Water” (CDW) is frequently observed in the East China Sea (ECS). In this study, the offshore detachment process of CDW into the ECS is examined using a three-dimensional numerical model. The model results show that low-salinity water is detached from the CDW plume by the intense tide-induced vertical mixing during the spring tide period when the tidal current becomes stronger. During the spring tide, thickness of the bottom mixed layer in the sloping bottom around Changjiang Bank reaches the mean water depth, implying that the stratification is completely destroyed in the entire water column. As a result, the offshore detachment of CDW occurs in the sloping side of the bank where the tidal energy dissipation is strong enough to overcome the buoyancy effect during this period. On the other hand, the surface stratification is retrieved during the neap tide period, because the tidal current becomes substantially weaker than that in the spring tide. Wind forcing over the ECS as well as tidal mixing is a critical factor for the detachment process because the surface wind primarily induces a northeastward CDW transport across the shelf region where tide-induced vertical mixing is strong. Moreover, the wind-enhanced cross-isobath transport of CDW causes a larger offshore low-salinity patch, indicating that the freshwater volume of the low-salinity patch closely depends on the wind magnitude.

The reproductive biology of Corophium volutator and C. arenarium (Crustacea: Amphipoda)

1979 ◽  
Vol 59 (2) ◽  
pp. 355-368 ◽  
Author(s):  
J. D. Fish ◽  
A. Mills
Keyword(s):  
Spring Tide ◽  
Life Cycles ◽  
Rhythmic Pattern ◽  
Adult Males ◽  
Corophium Volutator ◽  
Adult Females ◽  
Initial Rupture ◽  
Two Generations ◽  
Embryonic Life ◽  
Tide Period

The life-cycles of Corophium volutator (Pallas) and C. arenarium Crawford in the Dovey Estuary are based on two generations per year. Reproduction is well established by April and although the overwintering generation dies during the summer, reproduction continues until October as a result of the breeding of summer-generation animals. The mean brood size of C. volutator is greater than that of C. arenarium and both species show high levels of egg loss from the brood pouch. Hatching and moulting of the embryonic cuticle take place simultaneously and the initial rupture of the egg membranes is made by spines on the cuticle of the telson of the future free-living animal. These spines persist throughout post-embryonic life.Adult females of both species show a semi-lunar breeding rhythmicity and, associated with this, adult males show a rhythmic pattern of crawling behaviour. As the tide ebbs during the rising spring tide period, adult males emerge from the sediment and crawl across the mud surface in search of burrows occupied by adult females. It is concluded that copulation takes place in the burrow and not in the water column.

scholarly journals Tidally driven stick–slip motion in the mouth of Whillans Ice Stream, Antarctica

2003 ◽  
Vol 36 ◽  
pp. 263-272 ◽  
Author(s):  
Robert A. Bindschadler ◽  
Patricia L. Vornberger ◽  
Matt A. King ◽  
Laurie Padman
Keyword(s):  
High Tide ◽  
Spring Tide ◽  
Shear Stresses ◽  
Motion Events ◽  
Stick Slip ◽  
Ice Stream ◽  
Whillans Ice Stream ◽  
Stick Slip Motion ◽  
Tide Period ◽  
Slip Motion

AbstractWe show that the ice plain in the mouth of Whillans Ice Stream (formerly Ice Stream B), Antarctica, moves by stick–slip motion. During a spring-tide period, rapid motions regularly occur near high tide and during falling tide. This correlation is weaker during a neap-tide period when the tidal magnitudes are less. Precise timing of these motion events suggests that they propagate through the region with a mean velocity of 88 m s−1.We hypothesize that this speed is associated with the propagation of shear waves through a wet subglacial till. Motion events are also seen on more smoothly flowing floating ice. Event delays are very short between grounded and floating stations, suggesting the events propagate through the ice shelf as an elastic wave. We further hypothesize the events are caused by the interaction of a sticky bed, the accumulation of stored elastic strain through the compression of ice by upstream inflow, and tidal forcing. Motion events seem to be triggered either by reduction of vertical normal stresses at high tide or by the increase of shear stresses from sub-shelf ocean currents during falling tide. Event magnitudes are not related to the length of the preceding quiescent period, suggesting significant viscous dissipation within the till.

Reducing Human-Bear Conflicts: Bear-Resistant Trash Cans

EDIS ◽  
2017 ◽  
Vol 2017 (3) ◽  
Author(s):  
Ethan T. Noel ◽  
Elizabeth F. Pienaar ◽  
Mike Orlando
Keyword(s):  
Great Risk ◽  
Ursus Americanus ◽  
Black Bear ◽  
Food Sources ◽  
Vehicle Collisions ◽  
Wildlife Ecology ◽  
Human Food ◽  
Fact Sheet

The Florida black bear (Ursus americanus floridanus) is the only species of bear in Florida, with an estimated population of approximately 4,030 bears. Bears that eat garbage put themselves in danger. This 3-page fact sheet written by Ethan T. Noel, Elizabeth F. Pienaar, and and Mike Orlando and published by the Wildlife Ecology and Conservation Department explains how to secure human garbage from bears so that they don’t become reliant on human food sources, a condition that puts them at great risk of being killed from vehicle collisions, illegal shooting, or euthanasia.­http://edis.ifas.ufl.edu/uw429

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