Present Status of the Salmonids Atlantic Salmon and Sea-Trout in the Dutch Part of the River Rhine

1994 ◽  
Vol 29 (3) ◽  
pp. 37-41 ◽  
Author(s):  
W. G. Cazemier
Keyword(s):  
Atlantic Salmon ◽  
Salmo Trutta ◽  
Natural Populations ◽  
River Rhine ◽  
Sea Trout ◽  
The Past ◽  
The North ◽  
Trout Population ◽  
The North Sea ◽  
Heavy Pollution

In the past, the anadromous salmonids, Atlantic salmon (Salmo salar) and sea-trout (Salmo trutta), have formed natural populations in the river Rhine. From the beginning of the nineteenth century onwards, the greater part of the drainage area of the river has been gradually altered from a more or less rural and agricultural area, into a highly industrialised one with subsequent industrialisation, river-engineering and heavy pollution. These developments are considered to be the major cause for the disappearance of the populations of anadromous salmonid fish in the 1950s. The water quality has recovered significantly during the past 25 years. From about 1975 onwards, this process gave rise to a recovery of the anadromous trout population. Results of recent studies of the sea-trout migration pattern are presented. They reveal that nowadays these salmonids can complete their up- and downstream migrations from the North Sea to places, situated at hundreds of kilometres upward the river and vica versa. The numbers of recorded Atlantic salmon and catch locations in inland waters are presented. They show a significant increase since 1989. These phenomena can be understood as promising signs of the recovery of the Rhine aquatic ecosystem.

The Rotterdam Initiative in Reducing Waste Discharges at Source

1991 ◽  
Vol 24 (10) ◽  
pp. 171-177
Author(s):  
T. Vellinga ◽  
J. P. J. Nijssen
Keyword(s):  
Public Relations ◽  
Action Plan ◽  
Detailed Balance ◽  
River Rhine ◽  
The North ◽  
Complementary Role ◽  
Action Programme ◽  
The North Sea ◽  
Set Up

Much of the material dredged from the port of Rotterdam is contaminated to such a degree that it must be placed in specially constructed sites. The aim of Rotterdam is to ensure that the dredged material will once again be clean. This will entail the thorough cleansing of the sources of the contamination of the sediment in the harbours and in the River Rhine. The Rotterdam Rhine Research Project (RRP) is one of the means to achieve this based on: technical research, legal research, public relations and dialogues with dischargers. The programme for five selected heavy metals is almost complete. For many heavy metal discharge points between Rotterdam and Rheinfelden, a specially devised independent load assessment has been carried out four times. Balance studies were used to determine the relative contributions of the point discharges to the total. Currently the results are being used in an attempt to negotiate agreements with a selected number of the major dischargers. At present, more detailed balance studies are being set up and exploratory measurements carried out for organic micropollutants. It may be concluded that the research is progressing successfully and methods and techniques developed seem satisfactory and broadly applicable. The Rhine Action Programme encompasses an international effort to improve the quality of the Rhine water. Although the RRP plays a modest complementary role to the Rhine Action Plan, there is no doubt of the value of this Rotterdam initiative. The mode of work followed in the RRP contains elements that can be of use in combatting the contamination of the North Sea by rivers other than the Rhine.

scholarly journals Documentation of multiple species of marine fish trapped in Atlantic salmon sea-cages in Norway

2018 ◽  
Vol 31 ◽  
pp. 31
Author(s):  
Per Gunnar Fjelldal ◽  
Monica F. Solberg ◽  
Kevin A. Glover ◽  
Ole Folkedal ◽  
Jonatan Nilsson ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Salmo Trutta ◽  
Gadus Morhua ◽  
Mesh Size ◽  
Anguilla Anguilla ◽  
Wild Fish ◽  
Melanogrammus Aeglefinus ◽  
European Eel ◽  
Farmed Salmon ◽  
Sea Trout

The production of salmonids in sea-cages has been developed for monoculture of the target species. However, we show here for the first time, that wild fish may enter sea-cages used for farming of Atlantic salmon (Salmo salar L.) in Norway, out-grow the mesh size, and thereafter become permanently trapped. Within seven different sea-cages located in western Norway, eight different species of wild fish were identified; European eel (Anguilla anguilla), sea trout (Salmo trutta L.), cod (Gadus morhua), haddock (Melanogrammus aeglefinus), saithe (Pollachius virens), pollack (Pollachius pollachius), hake (Merluccius merluccius) and whiting (Merlangius merlangus). In the two most extreme cases, a 5 × 5 × 7 m cage with 311 farmed salmon (903 g) also contained 542 whiting (79 g), 77 haddock (43 g), and 5 cod (26 g), and a 12 × 12 × 15 m cage with 1695 farmed salmon (559 g) also contained 1196 haddock (35 g), 1115 whiting (31 g), 46 cod (23 g), 23 saithe (48 g), 15 pollock (22 g), 5 sea trout (54 g), and 2 hake (29 g). The present study thus demonstrates that aquaculture cages designed for monoculture may attract and effectively ‘trap’ wild fish. We did not investigate the frequency of this occurrence, and the ecological significance of these observations remains unclear. However, with the ever-increasing number of sea-cages used for global aquaculture, this is clearly a topic for further research.

scholarly journals Salmon lice evasion, susceptibility, retention, and development differ amongst host salmonid species

2017 ◽  
Vol 75 (3) ◽  
pp. 1071-1079 ◽  
Author(s):  
Samantha Bui ◽  
Elina Halttunen ◽  
Agnes M Mohn ◽  
Tone Vågseth ◽  
Frode Oppedal
Keyword(s):  
Atlantic Salmon ◽  
Chinook Salmon ◽  
Salmo Trutta ◽  
Parasite Development ◽  
Lepeophtheirus Salmonis ◽  
Sea Trout ◽  
Salmon Lice ◽  
Salmonid Species ◽  
Host Parasite ◽  
Temporal Overlap

Abstract With different ecological characteristics amongst salmonid species, their response to parasitic infestation is likely to vary according to their spatial and temporal overlap with the parasite. This study investigated the host–parasite interactions amongst three species of salmonids and the ectoparasitic salmon louse, Lepeophtheirus salmonis. To determine any variation in infestation parameters amongst salmonids, single population groups of Atlantic salmon (Salmo salar), chinook salmon (Onchorhynchus tshawytscha), and previously-infested and naïve sea trout (Salmo trutta) were exposed to a controlled infestation challenge. We found that chinook salmon and both sea trout groups were more susceptible to acquiring lice than Atlantic salmon. Behavioural responses during infestation were more pronounced in Atlantic and chinook salmon. Parasite development was similar in lice attached to Atlantic salmon and sea trout, but hindered on chinook salmon. At 16 days post-infestation, chinook salmon had reduced lice loads to the same level as Atlantic salmon, whilst sea trout retained their lice. These results demonstrate differences in interactions with L. salmonis amongst these species, and highlight the vulnerability of sea trout to infestation.

scholarly journals DESIGN, ANALYSIS AND FIELD TEST OF A DYNAMIC FLOATING BREAKWATER

1976 ◽  
Vol 1 (15) ◽  
pp. 159 ◽  
Author(s):  
D.J. Agerton ◽  
G.H. Savage ◽  
K.C. Stotz
Keyword(s):  
Solid Wall ◽  
Offshore Structures ◽  
The Past ◽  
The North ◽  
Production Platform ◽  
Floating Breakwater ◽  
The North Sea ◽  
Floating Breakwaters ◽  
Offshore Oil ◽  
Permanent Wave

Interest in floating breakwaters has been generated in recent years because the concept offers the potential of providing a less expensive alternative to traditional, solid wall type barriers for providing permanent wave protection to the thousands of new recreational boat harbors and marinas that have been built in the past 20 years. Also, they may be able to provide temporary, mobile wave protection during construction and installation of offshore facilities for oil transfer and production operations, defense facilities and other offshore structures in deeper water (depths exceeding 50 to 100 feet). The engineering director of one of the largest and most active offshore oil producing companies recently stated that they would be willing to pay up to $6 million for a mobile, floating breakwater that had the proven capability to significantly reduce risks due to wave action during offshore erection in the North Sea or elsewhere. Considering the investment in just one deep water oil production platform already exceeds $100,000,000, the worth of such a reusable, wave protection system during the critical erection period of a platform should be large.

Effects of hydrological change and the cessation of stocking on a stream population of Salmo trutta L

1988 ◽  
Vol 39 (3) ◽  
pp. 337 ◽  
Author(s):  
PE Davies ◽  
RD Sloane ◽  
J Andrew
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
River Flow ◽  
River System ◽  
Riparian Habitat ◽  
Mean Flow ◽  
Age Composition ◽  
The North ◽  
Trout Population ◽  
Class Strength

The North Esk-St Patricks river system, northern Tasmania, was electrofished at 27 sites in 1985, 30 years after the same sites had been electrofished in a previous study on the survival of released brown trout. All sites were dominated by brown trout, Salmo trutta L. Before 1955, stocking of brown trout fry and yearlings had been heavy. Stocking ceased after 1956 and few releases were made to 1985. At all but 4 sites, the number and total biomass of brown trout were higher in 1985 than in 1955. The estimated total population of brown trout had increased by 63%, accompanied by a 55% increase in the number of fish of legal size (>22 cm). Previously described 'nursery streams' still maintained high densities of 0+ fish, despite considerable changes in the age composition at other sites. Little or no change had occurred in riparian habitat at 23 of 27 sites. Change in year-class strength was highly correlated with change in total annual river flow in the natal year. This is explained in terms of mortality in 'nursery streams' during periods of low river flow. At 19 sites out of 21, changes in age composition were related to relative changes in year-class strength due to interannual variability in river flow. Four sites where major changes in riparian habitat occurred exhibited decreased brown trout biomass but still showed changes in age structure due to variation in annual flow. Mean annual river flow had increased by three times since the 1950s and this was attributed to a doubling in the proportion of cleared land in the catchments. Effects of changes in river hydrology on the trout population are discussed. Growth of S. trutta was essentially independent of density. The number of anglers, total effort and the total harvest in 1985/86-1986/87 were significantly higher than in 1945/46-1953/54. A shift toward higher catch per season per angler was observed in 1985/86-1986/87 compared to the 1945/46- 1953/54 seasons, but catch per day had not changed. Total annual mortality remained at 70%. The effects of increased mean flow and interannual flow variability on the brown trout population of the North Esk river system are discussed.

scholarly journals Coastal archaeologies: settlement on the changing North Sea littoral

Antiquity ◽  
2017 ◽  
Vol 91 (358) ◽  
pp. 1095-1097
Author(s):  
Hans Peeters
Keyword(s):  
Sea Level ◽  
North Sea ◽  
British Isles ◽  
Prehistoric Archaeology ◽  
Sea Floor ◽  
The Past ◽  
The North ◽  
The North Sea ◽  
The Many ◽  
Rising Sea Level

Over the past decade or so, the submerged prehistoric archaeology and landscapes in the area that is known to us today as the North Sea have received increasing attention from both archaeologists and earth scientists. For too long, this body of water was perceived as a socio-cultural obstacle between the prehistoric Continent and the British Isles, the rising sea level a threat to coastal settlers, and the North Sea floor itself an inaccessible submerged landscape. Notwithstanding the many pertinent and pervasive problems that the archaeology of the North Sea still needs to overcome, recent research has made clear that these rather uninspiring beliefs are misplaced.

scholarly journals Reconstruction of Atlantic herring ( Clupea harengus ) recruitment in the North Sea for the past 455 years based on the δ 13 C from annual shell increments of the ocean quahog ( Arctica islandica )

2019 ◽  
Vol 20 (3) ◽  
pp. 537-551 ◽  
Author(s):  
Juan Estrella‐Martínez ◽  
Bernd R. Schöne ◽  
Ruth H. Thurstan ◽  
Elisa Capuzzo ◽  
James D. Scourse ◽  
...  
Keyword(s):  
North Sea ◽  
Clupea Harengus ◽  
Atlantic Herring ◽  
Arctica Islandica ◽  
The Past ◽  
The North ◽  
The North Sea
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