Mercury Content of Spiny Dogfish (Squalus acanthias) in the Strait of Georgia, British Columbia

1972 ◽  
Vol 29 (10) ◽  
pp. 1487-1490 ◽  
Author(s):  
C. R. Forrester ◽  
K. S. Ketchen ◽  
C. C. Wong
Keyword(s):  
Total Mercury ◽  
River Estuary ◽  
Mercury Content ◽  
Squalus Acanthias ◽  
Spiny Dogfish ◽  
Fraser River ◽  
Female Fish ◽  
Male And Female ◽  
Strait Of Georgia ◽  
Total Length

Total mercury content of Squalus acanthias sampled in the Strait of Georgia reached levels of 0.5 ppm at fish lengths of 72 and 77 cm for male and female fish, respectively. For any given length above 65 cm the mercury content was higher among males than females and higher in samples taken off the Fraser River Estuary than in other areas of the Strait. Levels of mercury reached 1.7 ppm in males (to 95 cm in total length) and almost 2.0 ppm in females (to 120 cm in total length).

Biology and Management of Dogfish Sharks

2009 ◽  
Keyword(s):  
Life History ◽  
Pacific Coast ◽  
Puget Sound ◽  
Squalus Acanthias ◽  
Spiny Dogfish ◽  
Dietary Analysis ◽  
Strait Of Georgia ◽  
Food Items ◽  
Abundance Estimates ◽  
Commercial Species

Abstract.—Spiny dogfish <em>Squalus acanthias </em>have been an important commercial species on Canada’s Pacific coast for more than 130 years. In this study we show that the spiny dogfish life history results in juveniles remaining in pelagic waters for 10–15 years after birth, with lengths up to about 60 cm. Abundance estimates show that the numbers of these young dogfish, as well as some older dogfish in the pelagic waters, appear to represent a relatively large percentage of the population in these two regions. Dietary analysis shows that while euphausiids and teleosts constitute the major food items, regardless of size/age, dogfish feed on a number of species within the ecosystem. After about 15 years, there is a movement into demersal habitats where individuals eventually mature. Because dogfish are long lived, and because they are found throughout the pelagic zone and demersal habitats, it is probable that they play a key role in the Strait of Georgia and Puget Sound ecosystems.

Pollution in the Strait of Georgia: a Review

1983 ◽  
Vol 40 (7) ◽  
pp. 1142-1167 ◽  
Author(s):  
Michael Waldichuk
Keyword(s):  
Urban Communities ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
River Estuary ◽  
Oxygen Depletion ◽  
Fraser River ◽  
Pulp Mills ◽  
Strait Of Georgia ◽  
Spring Freshet

The Strait of Georgia, when considered as a whole, is still comparatively free of major pollution problems. Local environmental degradation has taken place, however, in waters on the periphery of the Strait, adjacent to urban communities and industries, such as pulp mills. The Fraser River, which is the major source of freshwater to the Strait, introduces natural and man-made materials that can adversely affect its estuary and the marine environment. The Strait of Georgia is flushed regularly, with deep waters being replaced about annually and waters in the upper layer having a considerably shorter residence time. Buildup of pollutants or their effects, e.g. oxygen depletion, are prevented in this way. However, there is refluxing of surface waters into the deep zone from the mixing region at the southern entrance to the Strait, and this means that surface pollutants such as oil could pollute the deep water and be retained there for up to a year. Problems affecting fisheries have been identified at the Fraser River Estuary arising from discharge of sewage treatment plant effluent. The major problem of pollution affecting fisheries in the Strait of Georgia has been bacteriological contamination from sewage, which has necessitated the closure of shellfish beds. The quality of oysters, as represented by condition factor and flavor, has deteriorated in the vicinity of some pulp mills. Evidence so far indicates that the "critical pollutants," e.g. petroleum hydrocarbons, organochlorines, and metals, which are persistent, toxic, and can be bioaccumulated by marine organisms, are present in low concentrations in the water, sediments, and biota away from the Fraser River Estuary. Wood wastes in the Strait of Georgia create a menace to navigation, especially during the spring freshet of the Fraser River.

scholarly journals Observations on spiny dogfish (Squalus acanthias) captured in late spring in a North Carolina estuary

F1000Research ◽  
2014 ◽  
Vol 3 ◽  
pp. 189
Author(s):  
Charles Bangley ◽  
Roger Rulifson
Keyword(s):  
North Carolina ◽  
Dissolved Oxygen ◽  
Squalus Acanthias ◽  
Late Spring ◽  
Spiny Dogfish ◽  
Northwest Atlantic ◽  
Atlantic Population ◽  
Total Length ◽  
North Carolina Estuary

Five spiny dogfish were captured in early-mid May during gillnet and longline sampling targeting juvenile coastal sharks in inshore North Carolina waters.  Dogfish captures were made within Back Sound and Core Sound, North Carolina. All dogfish were females measuring 849-905 mm total length, well over the size at 50% maturity. Dogfish were caught at stations 1.8-2.7 m in depth, with temperatures 22.9-24.2 °C, 32.8-33.4 ppt salinity, and 6.9-8.0 mg/L dissolved oxygen. These observations are among the latest in the spring for spiny dogfish in the southeastern U.S. and occurred at higher temperatures than previously recorded for this species.  It is unclear whether late-occurring spiny dogfish in this area represent a cryptic late-migrating or resident segment of the Northwest Atlantic population.

Maturity, reproductive cycle and fecundity of the spiny dogfish Squalus acanthias (Chondrichthyes: Squalidae) off the Languedocian coast (southern France, northern Mediterranean)

2011 ◽  
Vol 91 (8) ◽  
pp. 1627-1635 ◽  
Author(s):  
C. Capapé ◽  
C. Reynaud
Keyword(s):  
Reproductive Cycle ◽  
Squalus Acanthias ◽  
Hepatosomatic Index ◽  
Spiny Dogfish ◽  
Male And Female ◽  
Southern France ◽  
Short Period ◽  
Wide Range ◽  
Males And Females ◽  
Near Term

The spiny dogfish Squalus acanthias is widely distributed in Atlanto-Mediterranean regions, being captured off the Languedocian coast (southern France, northern Mediterranean), despite a decline of landings. The male and female sexually matured between 635–700 mm and 860–880 mm total length (TL), respectively. The largest male and female were 800 mm and 1110 mm TL, respectively and weighed 2220 g and 8900 g, respectively. There was a significant relationship for total mass versus TL, and liver mass versus TL between males and females. The diameter of the largest yolky oocytes ranged between 43 and 47 mm (mean 45.08 ± 0.98), while the mass ranged between 29.5 and 37.4 g (mean 31.79 ± 2.20). Near- term embryos ranged from 245 to 271 mm TL (mean: 258.85 ± 7.28) and weighed from 47.5 to 55.9 g (mean 53.35 ± 2.26). Ovarian fecundity ranged from 6 to 15 (mean = 10.38 ± 2.66). Uterine fecundity or litter size ranged from 4 to 12 (mean = 8.15 ± 2.07). Both fecundities showed a positive relationship with TL of females. A chemical balance of development based on mean dry masses of yolky oocytes and near-term embryos was 0.87 and suggested that S. acanthias is a pure lecithotrophic species. Hepatosomatic index (HSI) and gonadosomatic index (GSI) significantly increased with size in both males and females. HSI reached the highest values in both sub-adult and adult specimens, reflecting the role of the liver in the gonadal production as well as in buoyancy, while in the GSI the highest values were observed in pregnant females. Vitellogenesis proceeds in parallel with embryonic development. Near-term females were captured in different months of the year while a short period of resting could not be excluded between parturition and the beginning of a new pregnancy, so it appears difficult to delineate the length of gestation. However, a reproductive cycle with a wide range from 18 to 24 months remains a suitable hypothesis.

Drift Bottle Observations in the Strait of Georgia

1958 ◽  
Vol 15 (5) ◽  
pp. 1065-1102 ◽  
Author(s):  
Michael Waldichuk
Keyword(s):  
Surface Water ◽  
River Estuary ◽  
Surface Current ◽  
Fraser River ◽  
Strait Of Georgia ◽  
Average Speed ◽  
Local Areas ◽  
Strong Surface ◽  
Gulf Islands ◽  
Western Side

Drift bottle observations were carried out in the Strait of Georgia during the summers of 1926–1929. A total of 1,636 bottles was released of which 672 were recovered, giving an over-all return of 41%.No consistent pattern of drift in the strait as a whole could be clearly drawn from the recoveries. Some consistency of circulation in local areas can be inferred from the net drift of bottles.Winds dominated drift bottle movements in the open strait, where tidal currents are weak. A general northwestward drift was noted from releases along the eastern side of the strait and a southeastward drift along the western side. This suggests a large counterclockwise circulation of surface water over the whole strait. A smaller gyral circulating in the same direction is apparent in the southern strait, south of a line from Sand Heads to Active Pass.A strong surface current is directed from the Fraser River estuary across the strait to the passes among the Gulf Islands. This seaward flow of fresh water is augmented by a strong seaward tidal current during large ebb tides.Tidal currents are strong with definite periodicities in the channels bordering the strait. Current speeds of more than 26 cm./sec. (0.5 knot) were calculated from data on drift bottles whose drift was of brief duration. Average speed of drift was about 10 cm./sec. (0.2 knot).

Age Determination of an Elasmobranch (Squalus acanthias) by X-ray Spectrometry

1977 ◽  
Vol 34 (1) ◽  
pp. 44-48 ◽  
Author(s):  
Barry C. Jones ◽  
Glen H. Geen
Keyword(s):  
Age Determination ◽  
Element Composition ◽  
Squalus Acanthias ◽  
Spiny Dogfish ◽  
Strait Of Georgia ◽  
X Ray ◽  
Spectrometric Technique

Ages of spiny dogfish (Squalus acanthias) in the Strait of Georgia, B.C., have been estimated by an X-ray spectrometric technique which involves measuring variations in the element composition within vertebrae.

Anomalous Occurrence of Carp (Cyprinus carpio) in the Marine Environment

1971 ◽  
Vol 28 (9) ◽  
pp. 1345-1347 ◽  
Author(s):  
W. E. Barraclough ◽  
D. G. Robinson
Keyword(s):  
British Columbia ◽  
Marine Environment ◽  
Surface Waters ◽  
Cyprinus Carpio ◽  
River Estuary ◽  
Vancouver Island ◽  
Fraser River ◽  
Strait Of Georgia ◽  
Low Salinity ◽  
Carp Cyprinus Carpio

Juvenile carp (Cyprinus carpio) were caught with a surface trawl in low salinity surface waters of the Strait of Georgia, British Columbia, during July 1967. A natural environmental route is established for the possible movement of carp from the Fraser River estuary to watersheds on Vancouver Island.

Migratory patterns of sockeye salmon (Oncorhynchus nerka) smolts in the Strait of Georgia, British Columbia, as determined by analysis of parasite assemblages

1989 ◽  
Vol 67 (7) ◽  
pp. 1670-1678 ◽  
Author(s):  
C. Groot ◽  
R. E. Bailey ◽  
L. Margolis ◽  
K. Cooke
Keyword(s):  
Sockeye Salmon ◽  
River Estuary ◽  
River System ◽  
Fraser River ◽  
Strait Of Georgia ◽  
The Pacific ◽  
Lake Washington ◽  
Migratory Routes ◽  
Migratory Patterns ◽  
Parasite Assemblages

Sockeye salmon smolts from the Fraser River system, migrating northward through the Strait of Georgia towards the Pacific Ocean, follow either an eastern route by immediately travelling northward upon leaving the Fraser River estuary or a western route by first crossing the Strait of Georgia towards Vancouver Island and then moving northward diagonally across the Strait of Georgia to join smolts migrating along the mainland shore. We used variations in parasite assemblages among Fraser River and Lake Washington sockeye smolt stocks and a maximum-likelihood mixture model to estimate the stock composition of the smolts along the two migratory routes. The results showed that most Fraser River sockeye smolts migrate northward via both the eastern and western routes through the Strait of Georgia, indicating that there is no stock specific route selection. Lake Washington smolts were more prevalent along the western route and we suggest that these smolts are transported westward when attempting to cross the Fraser River plume.

Reproduction and Embryonic Development of Spiny Dogfish (Squalus acanthias) in the Strait of Georgia, British Columbia

1977 ◽  
Vol 34 (9) ◽  
pp. 1286-1292 ◽  
Author(s):  
Barry C. Jones ◽  
Glen H. Geen
Keyword(s):  
Embryonic Development ◽  
Length Distribution ◽  
Uterine Cavity ◽  
Mesh Size ◽  
Squalus Acanthias ◽  
Population Characteristics ◽  
Spiny Dogfish ◽  
Total Catch ◽  
Strait Of Georgia ◽  
Males And Females

Lengths at 50% maturity of spiny dogfish (Squalus acanthias) in the Strait of Georgia, B.C., are 78.5 and 93.5 cm, corresponding to ages 19 and 29 yr, for males and females, respectively. Modal lengths of mature males and females are 85 and 100 cm, respectively.Mating occurs from October to January, with a peak in December. Males are capable of mating every year, with smaller dogfish mating earlier in the year than larger ones. Females mate every 2nd yr. Ovulation of 4 cm diam eggs closely follows mating. The fertilized eggs are enclosed in gelatinous capsules for 4 mo after which the embryos are released into the uterine cavity. The external yolk supply of the embryos is totally absorbed by parturition, although the internal yolk is not fully utilized until 2 mo later. Parturition occurs from September to January, with a peak in November. Gestation is roughly 23 mo. Breeding females produce a mean of 7.14 progeny.These population characteristics indicate that regulation of a future fishery should be by total catch limit rather than net mesh size selection. Key words: spiny dogfish, reproduction, length distribution, survivorship, fecundity, fishery regulation

sexual maturity, fecundity and embryonic development of the spiny dogfish, squalus acanthias, in the eastern mediterranean sea

2005 ◽  
Vol 85 (5) ◽  
pp. 1155-1161 ◽  
Author(s):  
archontia chatzispyrou ◽  
persefoni megalofonou
Keyword(s):  
Mediterranean Sea ◽  
Eastern Mediterranean ◽  
Gonadosomatic Index ◽  
Squalus Acanthias ◽  
Minimum Size ◽  
Hepatosomatic Index ◽  
Spiny Dogfish ◽  
Female Fish ◽  
Eastern Mediterranean Sea ◽  
Gravid Females

the reproductive biology of the spiny dogfish, squalus acanthias, was investigated throughout a year, in the eastern mediterranean sea. one hundred and eighty specimens were sampled of which 119 were females and 61 males, ranging from 320 to 755 mm and from 350 to 820 mm total length (tl), respectively. the minimum size of mature females was 515 mm and 470 mm tl for mature males (smaller compared with sizes in other studies). gonadosomatic index (gsi) and hepatosomatic index (hsi) were higher during june and august in female dogfish, respectively; in males gsi had a peak in july and hsi showed its highest value in april. a total of 39 gravid females was identified with tl ranging between 570 and 755 mm. only 28 of them were bearing embryos; candled uteri were observed in the 11 other gravid animals. a positive relationship was recorded between maternal length and litter size. ovarian fecundity ranged between 1 and 6 (mean 2.1±1.1); uterine fecundity ranged from 1 to 6 (mean 3.3±1.2). the size of the pups varied from 72 to 220 mm tl and their weight ranged between 1.6–48.5 g (mean 11.7±8.6). the spiny dogfish was compared with fish from other study areas and was found to be smaller in size in the eastern mediterranean sea, reaching maturity at smaller sizes and obtaining lower fecundity than female fish in other areas.

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