scholarly journals Productivity of riverine habitats may be changing for American eel

2018 ◽  
Vol 75 (11) ◽  
pp. 1773-1777 ◽  
Author(s):  
Heather Dawn Bowlby
Keyword(s):  
Nova Scotia ◽  
Atlantic Coast ◽  
American Eel ◽  
Regional Productivity ◽  
Glass Eel ◽  
Watershed Characteristics ◽  
High Productivity ◽  
Enhanced Production ◽  
Juvenile Abundance ◽  
Riverine Habitats

The panmictic population of American eel (Anguilla rostrata) is at risk, making any region that supports enhanced production important from a recovery perspective. Strong glass eel runs to a small number of rivers along the Atlantic coast of Nova Scotia are thought to indicate high productivity, partially buffering declines occurring in other regions. However, contrary to glass eel indices of recruitment, an index representing older juveniles has strongly declined in riverine habitats throughout Nova Scotia from 1995 to 2005, with evidence of substantial differences in relative abundance among watersheds. This suggests that glass eel indices may not reflect trends of older juveniles and consequently that the contribution of Atlantic coast rivers to population persistence may be overstated. More recent monitoring from two rivers shows divergent trends in juvenile eel abundance, underscoring the importance of widespread surveys to assess changes in regional productivity. Further evaluation of the watershed characteristics associated with higher juvenile abundance would aid in understanding differences in productivity among watersheds and possibly in facilitating increased spawning escapement for American eel.

Geographic and seasonal variation in biological characteristics of American eel elvers in the Bay of Fundy area and on the Atlantic coast of Nova Scotia

1998 ◽  
Vol 76 (12) ◽  
pp. 2172-2185 ◽  
Author(s):  
B M Jessop
Keyword(s):  
Nova Scotia ◽  
Atlantic Coast ◽  
Bay Of Fundy ◽  
Biological Traits ◽  
American Eel ◽  
East River ◽  
Commercially Important ◽  
The Mean ◽  
Seasonal Decline ◽  
Collection Date

Seasonal (April-July) patterns in the decline of length, mass, and condition and an increase in pigmentation stage of American eel (Anguilla rostrata) elvers collected during the estuarine commercial fishery and during entrance into fresh water varied among rivers in the Bay of Fundy and on the Atlantic coast of Nova Scotia. Elver mean length, adjusted to a mean collection date, varied among commercially fished rivers by up to 9%; mean mass varied by up to 27%. Within commercially fished rivers, mean length declined seasonally by 2-5%, mass by 0-60%, and condition by 0-44%. Elver condition declined 7-9% by the time 50% of the run (number of elvers) had entered the East River, Chester, and East River, Sheet Harbour, and by 21% at 95% of the run, while the mean pigmentation stage increased to 4.1-4.8 and 5.7-6.5, respectively, on a scale of 1-7. Such geographic variability in biological traits may result from the effect of varying annual and seasonal environmental conditions on the coastal distribution of elvers and on their run timing and physiological development in estuarine and stream habitats. The biological importance of the seasonal decline in elver length, mass, and condition is uncertain, but a seasonal decline in mass of 35% may be commercially important when elvers are sold by weight rather than count.

Marked contrast in wind-driven upwelling on the southeastern Nova Scotia coast in July of two years differing in ENSO conditions

2020 ◽  
Vol 49 (1) ◽  
pp. 81-87 ◽  
Author(s):  
Ricardo A. Scrosati ◽  
Julius A. Ellrich
Keyword(s):  
Nova Scotia ◽  
El Niño ◽  
Coastal Upwelling ◽  
El Nino ◽  
Atlantic Coast ◽  
Future Research ◽  
Recent Book ◽  
Limited Information ◽  
Marked Contrast ◽  
The World

AbstractUpwelling occurs on several coasts of the world, but it has mostly been studied on eastern ocean boundaries. We investigated upwelling on a western ocean boundary for which limited information exists. Using daily in-situ data on sea surface temperature (SST), we found a marked contrast in coastal cooling between July 2014 (pronounced) and July 2015 (weak) at two locations 110 km apart on the Atlantic coast of Nova Scotia, Canada. These findings are consistent with a marked interannual difference in wind-driven upwelling. On the one hand, southwesterlies (which cause upwelling on this coast) were more frequent in July 2014 than in July 2015. On the other hand, Bakun’s upwelling index (which is based on wind data and geographic information) indicated that coastal upwelling was more common and intense in July 2014 than in July 2015, while the reverse was true for downwelling. Interestingly, a strong El Niño event occurred in July 2015, while no El Niño (or La Niña) conditions happened in July 2014. In a recent book evaluating upwelling systems around the world, the system that is the focus of the present study was not included. Therefore, our findings should stimulate future research on upwelling on the Atlantic Canadian coast, in that way helping to further develop the knowledge base for western ocean boundaries.

SEISMIC STUDIES ON THE EASTERN SEABOARD OF CANADA: THE ATLANTIC COAST OF NOVA SCOTIA

1964 ◽  
Vol 1 (1) ◽  
pp. 10-22 ◽  
Author(s):  
D. L. Barrett ◽  
M. Berry ◽  
J. E. Blanchard ◽  
M. J. Keen ◽  
R. E. McAllister
Keyword(s):  
Nova Scotia ◽  
Upper Mantle ◽  
Atlantic Coast ◽  
Seismic Refraction ◽  
Compressional Wave ◽  
Crust And Upper Mantle ◽  
Compressional Waves ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Eastern Seaboard

The results of seismic refraction profiles on the Atlantic coast of Nova Scotia and on the continental shelf off Nova Scotia are presented. Compressional and shear waves have been observed in the crust and mantle and suggest that the thickness of the crust is about 34 km. The compressional wave velocities recorded in the main crust and upper mantle are 6.10 and 8.11 km s−1 respectively. No compressional waves with values of velocity between these values can be identified, and this suggests that any "intermediate" layer is thin or absent. The corresponding shear wave velocities are 3.68 and 4.53 km s−1. Values of Poisson's ratio in the crust and mantle are 0.22 and 0.28. Alternative models of the crust which, on the evidence of travel times, might fit the observed results are discussed.

The Lobster (Homarus americanus) Fishery off Lower Argyle Southwestern Nova Scotia

1990 ◽  
Vol 47 (6) ◽  
pp. 1177-1184 ◽  
Author(s):  
Alan Campbell
Keyword(s):  
Nova Scotia ◽  
Fold Increase ◽  
Homarus Americanus ◽  
Weekly Basis ◽  
Index Numbers ◽  
Management Implications ◽  
Frequency Distributions ◽  
Fishing Season ◽  
Juvenile Abundance ◽  
Overall Mortality

Catch and effort data for the lobster (Homarus americanus) fishery of Lower Argyle, Nova Scotia, were obtained from sales slips on a weekly basis during 1978–87. Lobster size–frequency distributions were collected during at-sea sampling at the beginning and end of each fishing season. This fishery experienced a three-fold increase in landings (from 87.6 to 270 t) due to an increase in recruitment during the 10-yr study. The fishermen responded to the improved recruitment by increasing the total number of days fished per season by 41%. Overall mortality of recruited lobster (estimated from size–frequencies) rose from 55% in 1978 to 72–81% during 1985–87. During the 1987–88 fishing season, about 1 t lobster were removed per km2 of fishing grounds. Regression relationships between a prerecruit juvenile abundance index (numbers of lobster/trap haul) and the recruited yield one to two fishing seasons later were significantly correlated for 8–9 yr of data; equations predicted that lobster yields would remain high during the 1988–89 fishing season but decline in this area during 1989–90 fishing season. Management implications of forecasting recruitment yields 1–2 yr in advance and possible strategies to reduce major recruitment fluctuations in this fishery are discussed.

Rheotaxis of Elvers of the American Eel (Anguilla rostrata) in the Laboratory to Water from Different Streams in Nova Scotia

1968 ◽  
Vol 25 (8) ◽  
pp. 1591-1602 ◽  
Author(s):  
S. G. Miles
Keyword(s):  
Organic Matter ◽  
Nova Scotia ◽  
Fresh Water ◽  
Stream Water ◽  
Salt Water ◽  
The Other ◽  
Anguilla Rostrata ◽  
American Eel ◽  
Heat Stable ◽  
Experimental Apparatus

In an experimental apparatus, elvers of the American eel (Anguilla rostrata) showed a stronger positive rheotaxis to fresh water than to salt water. The attractiveness of the fresh water was due to dissolved and particulate organic matter; these components were bio-degradable, heat stable, and nonvolatile. Four streams near Halifax, Nova Scotia, were tested, and were found to differ greatly in their attraction of elvers. Elvers were collected from each of three of these streams, and were not found to be attracted to their own stream water; elvers from one stream gave a greater rheotactic response than elvers from the other streams. The presence of adult eels in the water rendered it more attractive, whereas the presence of elvers made it less so.

Biogeography of Iberian Atlantic Neogene marginelliform gastropods (Marginellidae, Cystiscidae): global change and transatlantic colonization

2011 ◽  
Vol 85 (6) ◽  
pp. 1052-1066 ◽  
Author(s):  
Carlos Marques Da Silva ◽  
Bernard Landau ◽  
Rafael La Perna
Keyword(s):  
West Africa ◽  
Sea Water ◽  
Atlantic Coast ◽  
Central American ◽  
Marine Gastropods ◽  
High Productivity ◽  
Complex Process ◽  
Central American Seaway ◽  
Central Portugal ◽  
The Caribbean

The Marginellidae Fleming and the Cystiscidae Stimpson, herein collectively referred to as marginelliform gastropods, are convergent families of thermophilic marine gastropods. Shallow-water marginelliform gastropods are found in the Ibero-Moroccan Gulf and Mediterranean, diversity rapidly increasing towards tropical West Africa. Surprisingly, in the tropical and subtropical European Miocene fossil record, marginelliform genera of tropical affinity such asPersiculaSchumacher andPrunumHerrmannsen, occurring today in West Africa, are altogether missing. Others, such asMarginellaLamarck, are present only in the southwestern Iberian and Mediterranean Neogene record. This work describes the marginelliform gastropods from the Atlantic Iberian Neogene. Ten species are recorded, of which three are new,Persicula mikhailovaen. sp.,Gibberula costaen. sp., andGibberula brebionin. sp. This study shows thatGibberulaSwainson andVolvarinaHinds have been present in Europe since the Eocene.Marginellamay have originated in southern Africa and migrated north to Europe in the Miocene, never extending further north than west central Portugal.PersiculaandPrunumprobably originated in the Caribbean and migrated east during the Pliocene, following closure of the Central American Seaway. The colonization of the Pliocene European Atlantic coast by gastropods of these genera was selective, only where high sea-water temperature and high productivity were combined. These findings suggest that post-Messinian recolonization of the Mediterranean during the Pliocene was a complex process, involving colonization by groups originating in various regions of the Atlantic, including Europe, Africa and the Americas.

COD MOVEMENTS ON THE CANADIAN ATLANTIC COAST

1933 ◽  
Vol 8 (1) ◽  
pp. 433-458 ◽  
Author(s):  
R. A. McKENZIE
Keyword(s):  
Nova Scotia ◽  
Prince Edward Island ◽  
Cold Water ◽  
Atlantic Coast ◽  
Summer Season ◽  
Warm Water ◽  
Early Winter ◽  
Cape Breton ◽  
Inshore Waters ◽  
Glace Bay

From 1925 to 1933 inclusive, during the summer season, 8,774 cod were tagged at eight points along the coasts of Nova Scotia and Prince Edward Island and eight per cent were recaptured during the following years, none after the sixth.Cod performing a restricted migration (less than 40 kilometres) were found to be in the majority off Halifax from July to September and off Shelburne in June and August in certain areas.Near Seal island in June, off Shelburne in July and September, and off Glace Bay in July and August, the majority of the cod were found to show orderly extended migrations. In the first two instances this movement was shoreward in the summer and seaward to about 130 metres in the early winter. The Glace Bay cod moved from the offshore banks just west of the Laurentian channel to the Cape Breton vicinity in the summer, returning early in the winter.A small percentage of the various stocks of cod performed roving migrations.The complete forsaking of the Cape Breton district for the offshore banks in the winter is attributed to the unfavourable ice cold water, while south-westward of Canso the movement off shore is thought to be caused by the very warm water inshore in the autumn and continued through the influence of the cold inshore waters several months later.As they grow older, the Shelburne cod remain progressively a little farther off shore when they move to shoal water each summer.

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