scholarly journals Direct observations of American eels migrating across the continental shelf to the Sargasso Sea

2015 ◽  
Vol 6 (1) ◽  
Author(s):  
Mélanie Béguer-Pon ◽  
Martin Castonguay ◽  
Shiliang Shan ◽  
José Benchetrit ◽  
Julian J. Dodson
Keyword(s):  
Continental Shelf ◽  
Sargasso Sea ◽  
Direct Observations ◽  
American Eels

Artificial maturation, fertilization, and early development of the American eel (Anguilla rostrata)

2010 ◽  
Vol 88 (11) ◽  
pp. 1121-1128 ◽  
Author(s):  
K. Oliveira ◽  
W. E. Hable
Keyword(s):  
Early Development ◽  
Anguilla Rostrata ◽  
Sargasso Sea ◽  
American Eel ◽  
Important Species ◽  
Vitro Fertilization ◽  
Commercially Important ◽  
Elusive Species ◽  
American Eels

Spawning for the American eel ( Anguilla rostrata (Le Sueur, 1817)) takes place in secretive locations within the Sargasso Sea, which has thus far prevented investigations of gametogenesis and early development in this ecologically and commercially important species. Attempts to induce maturation and reproduction in this species have been few and have produced limited results, with a single report of the production of gastrula-stage embryos. Here we report the successful maturation of female American eels. Maturation occurred within 13 weeks and ovulation was induced with a single injection of 17α,20β-dihydroxy-4-pregnen-3-one (DHP). Following in vitro fertilization, embryogenesis through hatching was observed and larvae were maintained for up to 6 days. We show that a crucial factor for successful fertilization is the stage of the oocyte at the time of induced ovulation. Oocytes that had not reached the migratory nucleus stage, or had passed this stage, were not successfully fertilized. These findings demonstrate that American eel can reproduce in the laboratory and previously untestable hypotheses pertaining to the developmental biology of this elusive species can now be explored.

Spatial distribution of Antarctic shrimps (Crustacea: Decapoda) by underwater photography

1991 ◽  
Vol 3 (4) ◽  
pp. 363-369 ◽  
Author(s):  
Julian Gutt ◽  
M. Gorny ◽  
W. Arntz
Keyword(s):  
Spatial Distribution ◽  
Continental Shelf ◽  
Weddell Sea ◽  
Small Scale ◽  
Frequency Distributions ◽  
South Eastern ◽  
Direct Observations ◽  
Underwater Photography ◽  
Dispersion Patterns ◽  
Eastern Weddell Sea

Three species of shrimps (Notocrangon antarcticus, Chorismus antarcticus, Nematocarcinus lanceopes) were investigated in the south-eastern Weddell Sea using of underwater photography. Maximum densities of c. 100 specimens per 100 m2 were found for N. antarcticus on the continental shelf (200–600 m) and for N. lanceopes on the slope (800–1200 m). Small-scale dispersion patterns and size-frequency distributions were analyzed within dense concentrations. These direct observations indicate that the behaviour of the three species is adapted to different habitats with Chorismus distribution correlated with that of sponges and Notocrangon with base sediment.

Larval fishes of a Middle Atlantic Bight estuary: assemblage structure and temporal stability

1999 ◽  
Vol 56 (2) ◽  
pp. 222-230 ◽  
Author(s):  
David A Witting ◽  
Kenneth W Able ◽  
Michael P Fahay
Keyword(s):  
Continental Shelf ◽  
Dominant Species ◽  
Fish Assemblages ◽  
Larval Fish ◽  
Temporal Stability ◽  
Temperature Cycle ◽  
Sargasso Sea ◽  
Larval Fishes ◽  
Middle Atlantic ◽  
Lower Temperature

We collected weekly, quantitative ichthyoplankton samples over 6 years (1989-1994, 1309 samples) to identify temporal scales of variability in the abundance and occurrence of larval fish assemblages near Little Egg Inlet in southern New Jersey, U.S.A. We collected species that spawn in the estuary (30%), both the estuary and continental shelf (35%), continental shelf (25%), and the Sargasso Sea (10%). The following analyses suggest an annually repeated seasonal progression of species assemblages: (i) the rank abundance of the 20 dominant species did not change significantly from year to year, (ii) variation in the density of the dominant species was primarily explained by intraannual rather than interannual variation, and (iii) multivariate analysis of the assemblage matrix identified five seasonal assemblages that occurred during all six years. We found that the timing and duration of each of these seasonal groups were correlated with two characteristics of the annual temperature cycle, magnitude (higher or lower temperature) and trajectory (increasing vs decreasing temperature). We suggest that the repeated occurrence of larval fish assemblages in temperate estuaries along the U.S. coast may, in part, be driven by local environmental processes.

Do Leptocephali of the European Eel Swim to Reach Continental Waters? Status of the Question

1998 ◽  
Vol 78 (1) ◽  
pp. 285-306 ◽  
Author(s):  
J.D. McCleave ◽  
P.J. Brickley ◽  
K.M. O'Brien ◽  
D.A. Kistner ◽  
M.W. Wong ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Anguilla Anguilla ◽  
Late Winter ◽  
European Eel ◽  
Sargasso Sea ◽  
North East ◽  
Nutritional Mode ◽  
Mid Atlantic Ridge ◽  
One Year ◽  
European Coast

We examined recent arguments that leptocephali of the European eel,Anguilla anguilla, swim in an oriented manner, rather than drift, to reach the continental shelf of Europe and the Mediterranean Sea. There is a cline of increasing body length of leptocephali from south to north and from west to east from the Mid-Atlantic Ridge (30°W) to the continental shelf, which could represent migration from south-west to north-east, transport eastward at all latitudes, or increased growth rate with latitude. Evidence that this cline is a trend in age of arriving glass eels along the European coast, and that the duration of migration is less than one year, is weak. Ages reported in the literature for specimens from Morocco to The Netherlands were based on the unvalidated assumption that rings in otoliths were deposited daily. The assumption is unwarranted because of low metabolic rate and uncertainty of nutritional mode of leptocephali. If the assumption were accepted, calculated hatching dates of eels arriving at the European coast imply year-round spawning. Lengths of leptocephali in the Sargasso Sea at various times imply that eels spawn only in late winter and spring. Leptocephali contain tiny amounts of muscle, especially aerobic muscle for sustained swimming. They probably have insufficient capability to swim across the Atlantic in the less than 1–2 y reported by others.

Subtropical pupping ground for a cold-water shark

2010 ◽  
Vol 67 (5) ◽  
pp. 769-773 ◽  
Author(s):  
Steven E. Campana ◽  
Warren Joyce ◽  
Mark Fowler
Keyword(s):  
Life History ◽  
Continental Shelf ◽  
Gulf Stream ◽  
Cold Water ◽  
Mature Female ◽  
Life History Stage ◽  
Sargasso Sea ◽  
Eastern Canada ◽  
Northern And Southern Hemispheres ◽  
Conservation And Management

Porbeagle sharks ( Lamna nasus ) are large pelagic sharks apparently restricted to the cold temperate waters of the northern and southern hemispheres. Despite considerable knowledge of their biology, their pupping (birthing) grounds have never been identified. Pop-up archival transmission tags applied to 21 sharks off eastern Canada indicated that males and immature sharks of both sexes remained primarily on the continental shelf for periods of up to 348 days after tagging. However, mature female porbeagles migrated up to 2356 km through the winter, at depths down to 1360 m beneath the Gulf Stream, to a subtropical pupping ground in the Sargasso Sea. In addition to this pupping ground being well south of their documented range, the placement of such a key life history stage in international, largely unregulated waters poses problems for the conservation and management of a species that is largely fished in Canadian waters.

Occurrence of American Eels, Anguilla rostrata, in Waters Overlying the Eastern North American Continental Shelf

1973 ◽  
Vol 30 (11) ◽  
pp. 1752-1755 ◽  
Author(s):  
Charles A. Wenner
Keyword(s):  
Continental Shelf ◽  
Chesapeake Bay ◽  
North American ◽  
Cape Cod ◽  
Anguilla Rostrata ◽  
American Eel ◽  
Morphometrical Analysis ◽  
Assateague Island ◽  
American Eels

Eleven reproductively maturing specimens of the American eel, Anguilla rostrata, were collected during three independent off-shore trawling operations. Three females were taken on December 5, 1967 southeast of the mouth of Chesapeake Bay in 10–13 fathoms, one male and one female on November 5, 1969 southeast of Cape Cod in 35–45 fathoms, and six females east of Assateague Island on December 22, 1971 in 5 fathoms. Morphometrical analysis showed that the specimens were within the range of "silver" phase of Anguilla rostrata. Gonadal observations were made on all specimens.

STUDIES OF MARINE PLANKTONIC DIATOMS: I. CYCLOTELLA NANA HUSTEDT, AND DETONULA CONFERVACEA (CLEVE) GRAN.

1962 ◽  
Vol 8 (2) ◽  
pp. 229-239 ◽  
Author(s):  
Robert R. L. Guillard ◽  
John H. Ryther
Keyword(s):  
Continental Shelf ◽  
Narragansett Bay ◽  
Vitamin B ◽  
Centric Diatom ◽  
Sargasso Sea ◽  
Planktonic Diatoms ◽  
Physiological Differences ◽  
Electron Microscopes ◽  
Morphological Differences

Bacteria-free clones of the small centric diatom Cyclotella nana Hustedt were isolated, three from estuarine localities, one from Continental Shelf waters, and one from the Sargasso Sea. Detonula confervacea was isolated from Narragansett Bay. Morphology of all clones was studied with the light and electron microscopes. Morphological differences between clones of C. nana do not at present warrant separating any as distinct species.Clones of C. nana require only vitamin B12; D. confervacea has no vitamin requirement.Growth of the estuarine clones of C. nana was unaffected by salinity down to 0.5‰ and increased with temperature to 25 °C. The Shelf clone grew more rapidly at salinities above 8‰ and at temperatures between 10° and 20 °C. The Sargasso Sea clone did not survive below 15 °C or 17.5‰, while D. confervacea did not survive at temperatures above 15° or at salinities below 8‰. The physiological differences between clones correspond roughly to the conditions obtaining in nature where each was collected.

Laboratory Experiments on the Orientation of the Adult American Eel, Anguilla rostrata

1968 ◽  
Vol 25 (10) ◽  
pp. 2143-2155 ◽  
Author(s):  
S. G. Miles
Keyword(s):  
Laboratory Experiments ◽  
Time Lapse ◽  
Physical Basis ◽  
Spawning Migration ◽  
Anguilla Rostrata ◽  
Sargasso Sea ◽  
Breeding Area ◽  
American Eel ◽  
American Eels

Adult American eels, Anguilla rostrata, caught on their spawning migration downriver, were filmed while in a circular tank, and the orientation of the eels was analysed by determining the direction of alignment of each eel in each frame of the time-lapse film. When allowed a view only of the sky, the eels oriented southward, in the direction of their supposed breeding area in the region of the Sargasso Sea. This southward orientation continued even if the eels were denied a view of the sky, provided they were subject to the diel rhythm of light–dark. Thus the eel seems capable of noncelestial orientation; the physical basis of this is not known.

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