Correlations between pathological changes and chemical contamination in American eels, Anguilla rostrata, from the St. Lawrence River

1997 ◽  
Vol 54 (8) ◽  
pp. 1916-1927 ◽  
Author(s):  
C M Couillard ◽  
P V Hodson ◽  
M Castonguay
Keyword(s):  
Anguilla Rostrata ◽  
Chemical Contamination ◽  
Pathological Changes ◽  
Preneoplastic Lesions ◽  
Biomarkers Of Exposure ◽  
Reproductive Impairment ◽  
Migratory Season ◽  
American Eels ◽  
The Relationship ◽  
St Lawrence River

American eel (Anguilla rostrata) from the St. Lawrence River are heavily contaminated with chemicals that may be associated with increased incidence of diseases and reproductive impairment. The relationship between tissue mirex concentration and body mass was used to separate eels into two groups: the proportion of eels migrating from contaminated areas (Lake Ontario and upper St. Lawrence River) increased as the migration season progressed. Vertebral malformations and basophilic foci in the liver (preneoplastic lesions) were more frequent at the end of the migratory season, when the eels were more heavily contaminated with organochlorine compounds. In contrast, mesenteric nematodes were more common in the first week of the season, when eels were less contaminated. Diameters and percentages of different stages of oocytes, and density and surface area of pigmented macrophage aggregates in the spleen, did not vary among weeks. While basophilic foci are specific biomarkers of exposure to environmental contaminants, vertebral malformations may be caused by a variety of other anthropogenic or natural factors.\b Further studies are needed to confirm the observed associations between chemical contamination and pathological changes.

Why Is Recruitment of the American Eel, Anguilla rostrata, Declining in the St. Lawrence River and Gulf?

1994 ◽  
Vol 51 (2) ◽  
pp. 479-488 ◽  
Author(s):  
M. Castonguay ◽  
P. V. Hodson ◽  
C. M. Couillard ◽  
M. J. Eckersley ◽  
J.-D. Dutil ◽  
...  
Keyword(s):  
Anguilla Rostrata ◽  
Commercial Fishing ◽  
Hydroelectric Dams ◽  
Chemical Contamination ◽  
The Past ◽  
Silver Eels ◽  
High Prevalence ◽  
American Eels ◽  
Reference Stock ◽  
St Lawrence River

We critically review four potential causes of a drastic decline in juvenile American eels, Anguilla rostrata, recruiting to Lake Ontario (81-fold decline from 1985 to 1992) and in juvenile eel densities in tributaries to the Gulf of St. Lawrence. Silver eels from the St. Lawrence River were much more contaminated and had a high prevalence of deformities and lesions than a reference stock although they were on average less contaminated in 1990 than in 1982 (1.12 versus 4.54 μgg−1 for PCB; 0.025 versus 0.07 μg∙g−1 for mirex). Lethal toxicity from chemical contamination has been known to occur in St. Lawrence River eels for the past 25–30 yr. Major habitat modifications in the St. Lawrence took place in the 1950's (St. Lawrence Seaway and hydroelectric dams), about 30 yr before recruitment started declining; this long delay argues against these perturbations being primary causes of the decline. There is little evidence that commercial fishing and oceanographic changes caused the decline. Overall, we conclude that we do not know what caused the pronounced recruitment decline. We propose research avenues and hypotheses that may advance understanding and emphasize that because of panmixia, the recruitment decline could be species wide.

Spatial and Temporal Variations in Chemical Contamination of American Eels, Anguilla rostrata, Captured in the Estuary of the St, Lawrence River

1994 ◽  
Vol 51 (2) ◽  
pp. 464-478 ◽  
Author(s):  
P. V. Hodson ◽  
M. Castonguay ◽  
C. M. Couillard ◽  
C. Desjardins ◽  
E. Pelletier ◽  
...  
Keyword(s):  
Temporal Variations ◽  
Polynuclear Aromatic Hydrocarbons ◽  
Delphinapterus Leucas ◽  
Anguilla Rostrata ◽  
Chemical Contamination ◽  
Reference Sites ◽  
Beluga Whales ◽  
Pcb Congeners ◽  
American Eels ◽  
St Lawrence River

Levels of polychlorinated biphenyls (PCBs), mirex, and pesticides were 10–100 times higher in migratory adult American eels, Anguilla rostrata, sampled at Kamouraska, Quebec, in 1990 than in eels from an uncontaminated reference tributary; concentrations in eels within the estuary varied little among sites. In contrast, mercury levels were the same at estuarine and reference sites, suggesting natural sources or atmospheric deposition of mercury. Dioxins, furans, and polynuclear aromatic hydrocarbons were virtually absent at all sites. During the 7 wk of migration, levels of PCBs, mirex, and pesticides in eels increased, while mercury did not. Since 1982, levels of PCBs and mirex have declined by 68 and 56%, respectively, and the percentage of eels exceeding human health guidelines for PCBs and mirex was about twofold lower in 1990 than in 1982. Levels of other pesticides have also declined, except that dieldrin is unchanged since 1982. While chemical concentrations are declining, levels of specific, highly toxic PCB congeners are sufficiently high that eel consumption by beluga whales (Delphinapterus leucas) is still likely to be hazardous. The hazard to the eels themselves is unknown due to a scarcity of toxicity data, but the highest concentrations of chemicals were observed in gonads.

Seasonal and diel patterns of stream invasion by American eels (Anguilla rostrata) in the northern Gulf of St. Lawrence

1989 ◽  
Vol 67 (1) ◽  
pp. 182-188 ◽  
Author(s):  
J.-D. Dutil ◽  
M. Michaud ◽  
A. Giroux
Keyword(s):  
Anguilla Rostrata ◽  
Small Stream ◽  
Glass Eel ◽  
North Shore ◽  
Diel Patterns ◽  
The North ◽  
Stream Migration ◽  
Glass Eels ◽  
American Eels ◽  
The Relationship

Seasonal and diel patterns of stream invasion by American eels (Anguilla rostrata) were monitored in a small stream located on the north shore of the Gulf of St. Lawrence from 1981 to 1985. Glass eels and elvers migrated from the sea in late June and July. Glass eels made up only a small percentage of the migrants. Pigmentation progressed quickly in the estuary, but elvers grew very slowly. Migration from the estuary and through the lower reaches of the stream was slow; no glass eels or elvers occurred at a station located only 4 km from saltwater. Juvenile eels reached that station in their second summer of stream residence. Juvenile eels migrated in July and August. They ranged from 70 to 250 mm in length and included more than one age-class. Those less than 100 mm in length were most numerous. Relative abundance of glass eels and elvers decreased in the estuary from 1981 to 1985. This coincided with a decrease in the proportion of smaller sized eels in the stream migration over the same period. Juvenile eels migrated progressively later in summer as the proportion of smaller sized eels decreased. Stream migration was nocturnal. Movements mainly occurred between 21:00 and 23:00. The relationship between glass eel and elver abundance in the estuary and juvenile eel abundance in the stream 1 and 2 years later was not clear.

A processing plant survey of external lesions of American eels (Anguilla rostrata) from Lake Ontario and the St. Lawrence River, Canada

1997 ◽  
Vol 31 (1-2) ◽  
pp. 19-32 ◽  
Author(s):  
Lucie T Dutil ◽  
Catherine M Couillard ◽  
Denise Bélanger
Keyword(s):  
Lake Ontario ◽  
Anguilla Rostrata ◽  
Processing Plant ◽  
American Eels ◽  
Plant Survey ◽  
St Lawrence River

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.

Distinction between American Eels (Anguilla rostrata) of Different Geographic Origins on the Basis of Their Organochlorine Contaminant Levels

1989 ◽  
Vol 46 (5) ◽  
pp. 836-843 ◽  
Author(s):  
Martin Castonguay ◽  
Jean-Denis Dutil ◽  
Claude Desjardins
Keyword(s):  
Lake Ontario ◽  
Anguilla Rostrata ◽  
Fish Tissues ◽  
Environmental Distribution ◽  
Stock Discrimination ◽  
Geographic Origins ◽  
Organochlorine Contaminants ◽  
Organochlorine Contaminant ◽  
American Eels ◽  
St Lawrence River

This study presents evidence that organochlorine contaminant levels of fish tissues represent a valuable tool for stock discrimination. Variability of concentrations of 15 organochlorine contaminants allowed a discrimination among American eels (Anguilla rostrata) of unknown (captured during the migration down the St. Lawrence River) or known geographic origins. The study also exemplifies that information regarding environmental distribution of contaminants can be gained by comparing organic contaminant levels among groups of fish. Indeed we can infer from this study that mirex contaminated sediments have extensively (at least 400 km) drifted downstream from Lake Ontario in less than 19 yr.

Fecundity and Gonad Observations of the American Eel, Anguilla rostrata, Migrating from Chesapeake Bay, Virginia

1974 ◽  
Vol 31 (8) ◽  
pp. 1387-1391 ◽  
Author(s):  
Charles A. Wenner ◽  
J. A. Musick
Keyword(s):  
Chesapeake Bay ◽  
Anguilla Anguilla ◽  
Total Weight ◽  
Anguilla Rostrata ◽  
American Eel ◽  
Total Length ◽  
American Eels ◽  
The Relationship ◽  
Sexually Mature ◽  
Gonadal Condition

Fecundity of the American eel, Anguilla rostrata, was estimated from 21 specimens migrating from Chesapeake Bay during November 1970. The relationship between total length and fecundity is log y = −4.29514 + 3.74418 log x where y is fecundity and x is total length (mm) and between total weight and fecundity is log y = 3.22990 + 1.1157 log x where y is fecundity and x is total weight (g). Gonadal condition was described statistically and histologically. Specimens migrating from Chesapeake Bay are more sexually mature than either American eels migrating from Canadian waters or European eels, Anguilla anguilla, migrating from Europe. The significance of these findings with regard to Tucker's hypothesis of European eels being more sexually advanced at the onset of the spawning migration is discussed.

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