Seasonal and diurnal activity of sixgill sharks (Hexanchus griseus) on a shallow water reef in the Strait of Georgia, British Columbia

2003 ◽  
Vol 81 (6) ◽  
pp. 1107-1111 ◽  
Author(s):  
Robert Dunbrack ◽  
Robert Zielinski
Keyword(s):  
British Columbia ◽  
Shallow Water ◽  
Population Biology ◽  
Time Lapse ◽  
Diurnal Activity ◽  
Top Predator ◽  
Strait Of Georgia ◽  
Continental Shelves ◽  
Unique Site ◽  
Hexanchus Griseus

The bluntnose sixgill shark (Hexanchus griseus) is a large, deepwater, cosmopolitan species whose range includes the Strait of Georgia, British Columbia. Although this species is probably the top predator on most of the world's continental shelves, there is little information on its population biology or behaviour. At a unique site off Flora Islets, in the Strait of Georgia, a number of H. griseus individuals show unexpected diurnal activity on a shallow reef. Regular movements of these sharks along the base of the reef wall allowed us to use an automated, time-lapse video system to make the first extensive observations of their behaviour between June 2001 and July 2002. Sixgill shark frequency (no. of sharks observed/h) increased in June and reached a peak between mid-June and mid-July. Sixgill sharks were not observed between October and May. Sixgill shark frequency was highest in the afternoon and the sharks tended to move as individuals rather than in groups. The observations suggest that this shallow-water activity is not related to either reproduction or feeding and its purpose remains unclear.

scholarly journals Abundance Trends for Hexanchus griseus, Bluntnose Sixgill Shark, and Hydrolagus colliei, Spotted Ratfish, Counted at an Automated Underwater Observation Station in the Strait of Georgia, British Columbia

2008 ◽  
Vol 122 (2) ◽  
pp. 124 ◽  
Author(s):  
Robert Dunbrack
Keyword(s):  
British Columbia ◽  
Relative Abundance ◽  
Time Lapse ◽  
Video Monitoring ◽  
Rocky Reef ◽  
Observation Station ◽  
Strait Of Georgia ◽  
The Past ◽  
Time Period ◽  
Hexanchus Griseus

Recordings from a time lapse video monitoring station on a shallow rocky reef in the Strait of Georgia, British Columbia, revealed a steep and continuous decline in the occurrence of Hexanchus griseus (Bluntnose Sixgill Shark) between 2001 and 2007, with relative abundance in 2006 and 2007 less than 1% of that in 2001. The relative abundance of another chondrichthyan, Hydrolagus colliei (Spotted Ratfish), decreased to 15% of 2004 levels in 2005 and 2006 and remained below 25% in 2007. There is no compelling explanation for these decreases. Over the past 25 years water temperatures have increased in the Strait of Georgia and there have been a number of El Niño warm water events, but diver observations of H. griseus at this site over the same time period give no indication of prior changes in abundance. Neither species is targeted by a fishery, but injuries, possibly related to hooking and entanglement, observed in 28% of individually identified H. griseus suggests this species may be taken locally as bycatch.

scholarly journals Body Size Distribution and Frequency of Anthropogenic Injuries of Bluntnose Sixgill Sharks, Hexanchus griseus, at Flora Islets, British Columbia

2005 ◽  
Vol 119 (4) ◽  
pp. 537 ◽  
Author(s):  
Robert Dunbrack ◽  
Robert Zielinski
Keyword(s):  
British Columbia ◽  
Size Distribution ◽  
Population Biology ◽  
Commercial Fishing ◽  
Free Swimming ◽  
Strait Of Georgia ◽  
Pregnant Females ◽  
Demersal Species ◽  
Hexanchus Griseus

The Bluntnose Sixgill Shark (Hexanchus griseus) is a widely distributed demersal species whose population biology is poorly understood. Although H. griseus is normally found in deep continental slope waters, individuals from a population in the Strait of Georgia, British Columbia, make unexpected diurnal movements onto a shallow reef (Flora Islets) between June and August. This shallow water activity allowed in situ length measurements to be made on 35 free-swimming Bluntnose Sixgill Sharks using stereo videography. The measured sharks were all large juveniles and sub-adults, although smaller juveniles and pregnant females are known to occur in deeper adjacent waters. The restricted size distribution at Flora Islets may arise because small juveniles avoid contact with larger conspecifics and mating takes place offshore. All measured sharks were individually identified by unique scar patterns. In 13 of 35 sharks these scars were consistent with injuries expected from hooking and entanglement by commercial fishing gear.

scholarly journals Upper-crustal structure beneath the Strait of Georgia, Southwest British Columbia

2007 ◽  
Vol 170 (2) ◽  
pp. 800-812 ◽  
Author(s):  
R. K. Dash ◽  
G. D. Spence ◽  
M. Riedel ◽  
R. D. Hyndman ◽  
T. M. Brocher
Keyword(s):  
British Columbia ◽  
Crustal Structure ◽  
Strait Of Georgia

Characterizing spatial structures of larval fish assemblages at multiple scales in relation to environmental heterogeneity in the Strait of Georgia (British Columbia, Canada)

2018 ◽  
Vol 75 (11) ◽  
pp. 1902-1914 ◽  
Author(s):  
Lu Guan ◽  
John F. Dower ◽  
Pierre Pepin
Keyword(s):  
British Columbia ◽  
Environmental Heterogeneity ◽  
Multiple Scales ◽  
Larval Fish ◽  
Critical Role ◽  
Multiscale Approach ◽  
Spatial Structures ◽  
Strait Of Georgia ◽  
Medium Scale

Spatial structures of larval fish in the Strait of Georgia (British Columbia, Canada) were quantified in the springs of 2009 and 2010 to investigate linkages to environmental heterogeneity at multiple scales. By applying a multiscale approach, principal coordinate neighborhood matrices, spatial variability was decomposed into three predefined scale categories: broad scale (>40 km), medium scale (20∼40 km), and fine scale (<20 km). Spatial variations in larval density of the three dominant fish taxa with different early life histories (Pacific herring (Clupea pallasii), Pacific hake (Merluccius productus), and northern smoothtongue (Leuroglossus schmidti)) were mainly structured at broad and medium scales, with scale-dependent associations with environmental descriptors varying interannually and among species. Larval distributions in the central-southern Strait were mainly associated with salinity, temperature, and vertical stability of the top 50 m of the water column on the medium scale. Our results emphasize the critical role of local estuarine circulation, especially at medium spatial scale, in structuring hierarchical spatial distributions of fish larvae in the Strait of Georgia and suggest the role of fundamental differences in life-history traits in influencing the formation and maintenance of larval spatial structures.

Ediacaran fossils and dubiofossils, Miette Group of Mount Fitzwilliam area, British Columbia

1991 ◽  
Vol 28 (10) ◽  
pp. 1541-1552 ◽  
Author(s):  
H. J. Hofmann ◽  
E. W. Mountjoy ◽  
M. W. Teitz
Keyword(s):  
British Columbia ◽  
Shallow Water ◽  
Rocky Mountains ◽  
Carbonate Mounds ◽  
Windermere Supergroup

Shallow-water clastic beds flanking stromatolitic carbonate mounds in the upper part of the Vendian Miette Group (Windermere Supergroup) of the Rocky Mountains contain a poorly preserved, soft-bodied fauna that comprises morphologically very variable discoid remains; these include the taxa Beltanella sp., cf. B. grandis, Charniodiscus? sp., Irridinitus? sp., Nimbia occlusa, Protodipleurosoma sp., cf. P. rugulosum, and Zolotytsia? sp. and seven types of dubiofossils.

Factors influencing the distribution of Egregia menziesii (Phaeophyta, Laminariales) in British Columbia, Canada

1978 ◽  
Vol 56 (9) ◽  
pp. 1198-1205 ◽  
Author(s):  
D. K. Gordon ◽  
R. E. DE Wreede
Keyword(s):  
British Columbia ◽  
High Temperature ◽  
Laboratory Experiments ◽  
Algal Flora ◽  
The West ◽  
Common Component ◽  
Strait Of Georgia ◽  
Low Salinity ◽  
Factors Influencing ◽  
Juan De Fuca

Egregia menziesii (Turner) Areschoug is a common component of the algal flora along the west coast of Vancouver Island, Queen Charlotte Strait, and the Strait of Juan de Fuca but is absent from the Strait of Georgia in British Columbia, Canada. This distribution pattern was found to be correlated with temperature and salinity in that E. menziesii is not present in areas where there are seasonal periods of low salinity and high temperature. To test this correlation, field transplants of sporophytes and laboratory experiments with sporophytes and culture work were carried out. The results suggest that the distribution of E. menziesii is limited by specific combinations of salinity and temperature; it requires high salinities and temperatures less than 15 °C for its survival.

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