Challenges for Diadromous Fishes in a Dynamic Global Environment

2009 ◽  
Keyword(s):  
Average Rate ◽  
Underlying Mechanism ◽  
Local Circulation ◽  
Vertical Movements ◽  
Swimming Depth ◽  
Open Sea ◽  
Silver Eels ◽  
Vertical Distributions ◽  
The Baltic ◽  
American Eels

<em>Abstract</em>.-The horizontal and vertical movements of 20 silver American eels <em>Anguilla rostrata </em>migrating through a macrotidal estuary and bay were tracked with hydroacoustic telemetry. Eels initiated their seaward migrations around or shortly after sunset, mostly migrated at night, exhibited no bias for migration on ebb versus flood tides, and swam both with and against tidal currents with little preference for depth. Profiles of eel vertical distributions during transit through the estuary, the bay, and the tidal passages that connected the bay to the open sea differed and differed from analogous profiles for silver European eels <em>A. anguilla </em>transiting the Baltic Sea where tidal forcing is negligible. The underlying mechanism(s) associated with their direction of net displacement appears to be innate, although local circulation features may influence transit speeds and exit routes to the open sea. Our results in combination with published information for both the silver American and the European eel suggest that the horizontal migration speed for both species is relatively invariant, around 0.5 body lengths per second. The rate of ascent/descent of eels exhibiting a change in swimming depth of greater than 5 m could not be estimated with precision from the available records of eel swimming depths. The observed average rate of 0.11 m/s was, however, within the relatively narrow range of the average vertical swimming speeds (0.11-0.18 m/s) reported in the literature for silver eels executing vertical dives.

The migration of stocked, trapped and transported, and wild female American silver eels through the Gulf of St. Lawrence

2018 ◽  
Vol 75 (11) ◽  
pp. 2024-2037 ◽  
Author(s):  
Mélanie Béguer-Pon ◽  
Guy Verreault ◽  
David Stanley ◽  
Martin Castonguay ◽  
Julian J. Dodson
Keyword(s):  
Detection Efficiency ◽  
Anguilla Rostrata ◽  
Migration Speed ◽  
Hydroelectric Dams ◽  
Wild Female ◽  
Swimming Depth ◽  
Silver Eels ◽  
Diel Vertical Migrations ◽  
American Eels ◽  
St Lawrence River

The stocking of juvenile eels and trap and transport programs of large yellow (American) eels (Anguilla rostrata) were initiated in Ontario to mitigate mortalities observed at hydroelectric dams and to increase escapement from the upper St. Lawrence River and Lake Ontario (Canada). A total of 380 migrating female silver eels (stocked, trapped and transported, and wild) were tagged with acoustic transmitters between 2011 and 2014. Their migration and escapement at the exit of the Gulf of St. Lawrence, the Cabot Strait, were recorded using acoustic receivers. Escapement rates varied between 8.9% and 20.0% annually (mean = 11.4%). A high proportion of stocked eels were detected (N = 27 of 43 detected at Cabot Strait), demonstrating their ability to escape the Gulf. No differences in migration speed or crossing locations at Cabot Strait were found among the three categories. Eels crossing Cabot Strait did not display diel and tidal patterns, but their estimated swimming depth indicated diel vertical migrations. The low escapement rates observed may be related to predation events and (or) the low and variable detection efficiency of the acoustic receivers’ line.

scholarly journals Silver eel migration behaviour in the Baltic

2007 ◽  
Vol 64 (7) ◽  
pp. 1457-1462 ◽  
Author(s):  
Håkan Westerberg ◽  
Ingvar Lagenfelt ◽  
Henrik Svedäng
Keyword(s):  
Baltic Sea ◽  
Data Storage ◽  
Anguilla Anguilla ◽  
Light Level ◽  
Thermocline Depth ◽  
Silver Eel ◽  
Migration Behaviour ◽  
Swimming Depth ◽  
Silver Eels ◽  
The Baltic

Abstract Westerberg, H., Lagenfelt, I., and Svedäng, H. 2007. Silver eel migration behaviour in the Baltic. – ICES Journal of Marine Science, 64: 1457–1462 Female silver eels (Anguilla anguilla L.) were tagged with data storage tags and released in the Baltic Sea at the same time at a single site on the east coast of Sweden. Data on temperature, light, and depth were obtained from six eels, continuous records for 71 d at sea. The swimming behaviour was similar for all fish, almost stereotyped: swimming activity was between dusk and dawn, starting at a light level corresponding to civic twilight and ending in the morning at generally the same light level. During daylight, the eels rested on the seabed at depths of 2–36 m. Swimming depth was typically close to the surface: up to 95% of swimming time was spent within 0.5 m of the surface. Short dives at irregular intervals (some 1–2 h−1) were made down to the thermocline depth, or occasionally, to the seabed. The duration of such dives were typically 5–10 min. Although only a few days at liberty, the eels had migrated a considerable distance between recapture and release sites, indicating a mean rate of travel of ∼16 km d−1. The recapture positions suggested unidirectional movements towards the southwestern Baltic Sea, i.e. close to the straits leading to the ocean, supporting a belief that the recorded movements were related to eel spawning migratory behaviour.

Organohalogens of Natural and Industrial Origin in Large Recipients of Bleach-Plant Effluents

1991 ◽  
Vol 24 (3-4) ◽  
pp. 373-383 ◽  
Author(s):  
A. Grimvall ◽  
H. Borén ◽  
S. Jonsson ◽  
S. Karlsson ◽  
R. Sävenhed
Keyword(s):  
Baltic Sea ◽  
Point Sources ◽  
The Baltic Sea ◽  
Long Distance ◽  
Long Distance Transport ◽  
Open Sea ◽  
Receiving Waters ◽  
The Baltic ◽  
Organic Halogens

The long-term fate of chlorophenols and adsorbable organic halogens (AOX) was studied in two large recipients of bleach-plant effluents: Lake Vättern in Sweden and the Baltic Sea. The study showed that there is a long-distance transport (&gt;100 km) of chloroguaiacols from bleach-plants to remote parts of receiving waters. However, there was no evidence of several-year-long accumulation of chloro-organics in the water-phase. A simple water-exchange model for Lake Vättern showed that the cumulated bleach-plant discharges from the past 35 years would have increased the AOX concentration in the lake by more than 100 µg Cl/l, if no AOX had been removed from the water by evaporation, sedimentation or degradation. However, the observed AOX concentration in Lake Vättern averaged only about 15 µg Cl/l, which was less than the average AOX concentration (32 µg Cl/l) in the “unpolluted” tributaries of the lake. Similar investigations in the Baltic Sea showed that non-point sources, including natural halogenation processes, accounted for a substantial fraction of the AOX in the open sea. The presence of 2,4,6-trichlorophenol in precipitation and “unpolluted” surface waters showed that non-point sources may also make a considerable contribution to the background levels of compounds normally regarded as indicators of bleach-plant effluents.

scholarly journals Swimming depth of migrating silver eels Anguilla japonica released at seamounts of the West Mariana Ridge, their estimated spawning sites

1999 ◽  
Vol 186 ◽  
pp. 265-269 ◽  
Author(s):  
J Aoyama ◽  
K Hissmann ◽  
T Yoshinaga ◽  
S Sasai ◽  
T Uto ◽  
...  
Keyword(s):  
Anguilla Japonica ◽  
The West ◽  
Swimming Depth ◽  
Silver Eels ◽  
Spawning Sites

Why should the Odra River mouth area not be regarded as an estuary? A geologist's point of view

2007 ◽  
Vol 36 (2) ◽  
Author(s):  
Andrzej Osadczuk ◽  
Stanisław Musielak ◽  
Ryszard Borówka
Keyword(s):  
Coastal Lagoons ◽  
River Mouth ◽  
Mouth Area ◽  
Point Of View ◽  
River Mouth Area ◽  
Open Sea ◽  
Odra River ◽  
Flow Through ◽  
The Baltic ◽  
Shallow Water Body

Why should the Odra River mouth area not be regarded as an estuary? A geologist's point of viewThe authors find no arguments that would justify application of the term "estuary" to the area of the Odra River discharge into the Baltic Sea. The physiography, geology, and hydrology of the Odra river mouth show that the area possesses many more characteristics typical of flow-through coastal lagoons than those of estuaries. Of key importance in this respect is the Szczecin Lagoon, an extensive, shallow water body separated from the open sea by a barrier intersected by three narrow and long straits. The lagoonal nature of the area is demonstrated also by its geological history.

An evaluation of light-mediated vertical migration of fish based on hydroacoustic analysis of the diel vertical movements of rainbow smelt (Osmerus mordax)

1995 ◽  
Vol 52 (3) ◽  
pp. 504-511 ◽  
Author(s):  
A. R. Appenzeller ◽  
W. C. Leggett
Keyword(s):  
Vertical Migration ◽  
Strong Relationship ◽  
Fish Population ◽  
Osmerus Mordax ◽  
Ambient Light ◽  
Rainbow Smelt ◽  
Vertical Movements ◽  
Light Levels ◽  
Vertical Distributions ◽  
Lower Light

We used hydroacoustics to examine diel changes in the vertical distributions of rainbow smelt, Osmerus mordax, in Lake Memphremagog, Quebec/Vermont. Our objective was to evaluate hypotheses linking diel vertical movements of fish with light levels. Smelt distributions were also monitored from June through October (1988 and 1990) to evaluate seasonal changes in their behavior. A strong relationship (r2 = 0.83) between ambient light intensities and the upper fish layer in the water column was observed. Fish depth was also related to the depth of the thermocline during the night and when surface water temperatures were > 18 °C. The most characteristic feature was the strong avoidance of light levels > 0.1 μW/cm2. However, we found considerable variation in lower light levels experienced by the whole fish population. The results suggest that existing models of anti-predation behavior relating light and fish depth are consistent, with some limitations, with patterns of diel vertical migration in rainbow smelt.

Petroleum hydrocarbons - a necessity of monitoring in a dredged material in the Polish coastal zone

2018 ◽  
Vol 33 (1) ◽  
pp. 50-60
Author(s):  
Marta Staniszewska ◽  
Helena Boniecka
Keyword(s):  
Baltic Sea ◽  
Coastal Zone ◽  
Petroleum Hydrocarbons ◽  
The Other ◽  
Dredged Material ◽  
The Baltic Sea ◽  
Legal Standards ◽  
Open Sea ◽  
Long Time ◽  
The Baltic

Petroleum hydrocarbons (PHCs) are toxic for the water organisms and in sediments they may last for a very long time. The Baltic Sea is an area exposed to the PHCs due to highly developed shipping. In Poland, there is a lack of legal standards specifying guidelines regarding handling dredged material containing PHCs, excavated in waterways, roadsteads, and in port basins, and there are no standards specifying their acceptable concentration in sediments. Therephore petroleum hydrocarbons in the excavated dredged material are rarely examined at the Polish coasts. In years 2009-2018 only 4% of sediments were examined in terms of their content. Indicated that only the sediments from the open sea did not contain PHCs, the other ones were very or moderately contaminated with PHCs. Collected results clearly indicate that sediment should be monitored in terms of the PHC content, in most cases should not be thrown back to the sea. In most cases they may be stored onshore, but only on wastelands, mainly industrial and transport areas. Some of them may also be used in the areas of cleaner lands, i.e. forests, wood- and bush-covered lands, recreation and leisure areas.

scholarly journals Recruitment dynamics of the Gulf of Riga herring stock: density-dependent and environmental effects

2010 ◽  
Vol 67 (9) ◽  
pp. 1914-1920 ◽  
Author(s):  
Tiit Raid ◽  
Georgs Kornilovs ◽  
Ain Lankov ◽  
Anne-Marin Nisumaa ◽  
Heli Shpilev ◽  
...  
Keyword(s):  
Environmental Effects ◽  
Egg Production ◽  
Age Groups ◽  
Zooplankton Community ◽  
Density Dependent ◽  
Current Period ◽  
Open Sea ◽  
Gulf Of Riga ◽  
The Baltic ◽  
Peak Abundance

Abstract Raid, T., Kornilovs, G., Lankov, A., Nisumaa, A-M., Shpilev, H., and Järvik, A. 2010. Recruitment dynamics of the Gulf of Riga herring stock: density-dependent and environmental effects. – ICES Journal of Marine Science, 67: 1914–1920. The Gulf of Riga and open-sea stocks of the Baltic herring have displayed remarkably consistent inverse recruitment and stock development patterns since the 1970s: the open-sea stocks steadily declined, whereas the Gulf stock increased rapidly in the early 1990s, reaching a peak abundance in the early 2000s and exceeding the level of the 1970s by a factor of 2–3. The increase was accompanied by a decline in the mean weight-at-age and the condition factor. The estimated decline (by 30–40%) in the average annual consumption rate per individual and changes observed in the zooplankton community suggest that density-dependent effects may have increased since the 1970s. The current period of high stock sizes is also characterized by greater recruitment variability. Historical fecundity investigations have established that the average egg production per individual has decreased in all age groups by 20–50%, along with a decrease in mean weight and condition. Yet, the effect on recruitment has been low so far, because lower fecundity has been compensated by the greater abundance and population fecundity has been maintained at the original level. Recruitment appears to be more influenced by environmental conditions than by spawning-stock biomass.

scholarly journals Management of Nutrient-Rich Wastes and Wastewaters on Board of Ships

2021 ◽  
Author(s):  
Céline Vaneeckhaute
Keyword(s):  
Food Waste ◽  
Sewage Water ◽  
Nutrient Recovery ◽  
Wastewater Management ◽  
Future Perspectives ◽  
Treatment Practices ◽  
Conventional Management ◽  
Open Sea ◽  
The Baltic ◽  
Review Current

Ship-generated nutrient-rich waste sources, including food waste and sewage water, contribute to eutrophication and deoxygenation of marine ecosystems. This chapter aims to discuss the characteristics of these waste and wastewater sources, review current ship-generated organic waste and wastewater regulations, inventory conventional management and treatment practices, and identify future perspectives for more sustainable nutrient-rich waste and wastewater management on board of ships. According to regulations, untreated food waste and sewage can generally be discharged into the open sea at more than 12 nautical miles from the nearest land, hence this is currently a common practice. However, special restrictions apply in special designated areas such as the Baltic Sea, where food waste must be comminuted/grounded and nutrients need to be removed from the sewage prior to discharge at 12 nautical miles from the nearest land. Current research looks at the valorisation of these waste and wastewater sources through anaerobic digestion, composting and/or nutrient recovery.

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