Fish production and the marine ecosystems of the Scotian Shelf, eastern Canada

1979 ◽  
Vol 54 (2) ◽  
pp. 101-108 ◽  
Author(s):  
E. L. Mills ◽  
R. O. Fournier
Keyword(s):  
Marine Ecosystems ◽  
Fish Production ◽  
Scotian Shelf ◽  
Eastern Canada

Late Quaternary sedimentation on the southwestern Scotian Slope, eastern Canada: relationship to glaciationGeological Survey of Canada Contribution 20070176.

2008 ◽  
Vol 45 (3) ◽  
pp. 267-285 ◽  
Author(s):  
Thian Hundert ◽  
David J.W. Piper
Keyword(s):  
Late Quaternary ◽  
Sediment Cores ◽  
Sediment Supply ◽  
Scotian Shelf ◽  
Eastern Canada ◽  
Glacial Retreat ◽  
Air Gun ◽  
Continental Slopes ◽  
History Of ◽  
Seismic Reflection Profiles

The sedimentary record on continental slopes has the potential to preserve a record of glacial retreat on the adjacent continental shelf. The glacial history of the southwestern part of the Scotian Shelf is poorly known. Air-gun and high-resolution sparker profiles and numerous sediment cores up to 10 m long have been used to determine the character of sedimentation on the southwestern Scotian Slope since the last glacial maximum (LGM). Seismic-reflection profiles show that glacial till was deposited at shallow depths on the upper continental slope, and correlation to dated piston cores farther downslope show that this till dates from the LGM. Slope sedimentation at this time was dominated by local ice and deposited as plume fallout and turbidites. Progressively increasing importance of red-brown sediment derived from glacial supply to Laurentian Channel indicates retreat of ice from the shelf edge and diminishing supply of proglacial sediment from the calving embayment in the mid-Scotian Shelf. With the termination of distal proglacial sediment supply, the sedimentation rate diminished rapidly and hemipelagic sedimentation prevailed through the Holocene.

Towards a balanced presentation and objective interpretation of acoustic and trawl survey data, with specific reference to the eastern Scotian Shelf

2016 ◽  
Vol 73 (12) ◽  
pp. 1914-1921 ◽  
Author(s):  
J. Michael Jech ◽  
Ian H. McQuinn
Keyword(s):  
Atlantic Cod ◽  
Management Strategies ◽  
Pelagic Fish ◽  
Trophic Levels ◽  
Fish Abundance ◽  
Forage Fish ◽  
Specific Reference ◽  
Trawl Survey ◽  
Scotian Shelf ◽  
Eastern Canada

A debate has developed over the ecosystem consequences following the collapse of Atlantic cod throughout the coastal waters of eastern Canada. The explosive increase in pelagic fish abundance in scientific bottom-trawl catches on the eastern Scotian Shelf has been interpreted as being due to either (i) a “pelagic outburst” of forage fish abundance resulting from predator release or conversely (ii) a change in pelagic fish vertical distribution leading to a “suprabenthic habitat occupation” thereby increasing their availability to bottom trawls. These two interpretations have diametrically opposing ecological consequences and suggest different management strategies for these important forage fish species. We argue that an objective evaluation of the available evidence supports the hypothesis that the abundance of forage fish has not increased in response to the demise of cod and other top predators, and the reliance on a single sampling gear with low catchability has biased and will continue to bias the interpretation of demographic trends of pelagic fish populations. We advocate that multiple sampling technologies providing alternative perspectives are needed for the monitoring and management of the various trophic levels if we are to achieve a balanced and objective understanding of marine ecosystems.

Storm graded sand at 200 m water depth, Scotian Shelf, Eastern Canada

1982 ◽  
Vol 2 (1-2) ◽  
pp. 77-81 ◽  
Author(s):  
Nikos Kontopoulos ◽  
David J. W. Piper
Keyword(s):  
Water Depth ◽  
Scotian Shelf ◽  
Eastern Canada

scholarly journals Enhanced chlorophyll-<i>a</i> concentration in the wake of Sable Island, eastern Canada, revealed by two decades of satellite observations: a response to grey seal population dynamics?

2021 ◽  
Vol 18 (23) ◽  
pp. 6115-6132
Author(s):  
Emmanuel Devred ◽  
Andrea Hilborn ◽  
Cornelia Elizabeth den Heyer
Keyword(s):  
Time Series ◽  
Phytoplankton Biomass ◽  
Standing Stock ◽  
Satellite Observations ◽  
Trophic Levels ◽  
Leeward Side ◽  
Grey Seal ◽  
Scotian Shelf ◽  
Eastern Canada ◽  
Chl A

Abstract. Elevated surface chlorophyll-a (chl-a) concentration ([chl-a]), an index of phytoplankton biomass, has been previously observed and documented by remote sensing in the waters to the southwest of Sable Island (SI) on the Scotian Shelf in eastern Canada. Here, we present an analysis of this phenomenon using a 21-year time series of satellite-derived [chl-a], paired with information on the particle backscattering coefficient at 443 nm (bbp(443), a proxy for particle suspension) and the detritus/gelbstoff absorption coefficient at 443 nm (adg(443), a proxy to differentiate water masses and presence of dissolved organic matter) in an attempt to explain some possible mechanisms that lead to the increase in surface biomass in the surroundings of SI. We compared the seasonal cycle, 8 d climatology and seasonal trends of surface waters near SI to two control regions located both upstream and downstream of the island, away from terrigenous inputs. Application of the self-organising map (SOM) approach to the time series of satellite-derived [chl-a] over the Scotian Shelf revealed the annual spatio-temporal patterns around SI and, in particular, persistently high phytoplankton biomass during winter and spring in the leeward side of SI, a phenomenon that was not observed in the control boxes. In the vicinity of SI, a significant increase in [chl-a] and adg(443) during the winter months occurred at a rate twice that of the ones observed in the control boxes, while no significant trends were found for the other seasons. In addition to the increase in [chl-a] and adg(443) within the plume southwest of SI, the surface area of the plume itself expanded by a factor of 5 over the last 21 years. While the island mass effect (IME) explained the enhanced biomass around SI, we hypothesised that the large increase in [chl-a] over the last 21 years was partly due to an injection of nutrients by the island's grey seal colony, which has increased by 200 % during the same period. This contribution of nutrients from seals may sustain high phytoplankton biomass at a time of year when it is usually low following the fall bloom. A conceptual model was developed to estimate the standing stock of chl-a that can be sustained by the release of nitrogen (N) by seals. Comparison between satellite observations and model simulations showed a good temporal agreement between the increased abundance of seal on SI during the breeding season and the phytoplankton biomass increase during the winter. We found that about 20 % of chl-a standing stock increase over the last 21 years could be due to seal N fertilisation, the remaining being explained by climate forcing and oceanographic processes. Although without in situ measurements for ground truthing, the satellite data analysis provided evidence of the impact of marine mammals on lower trophic levels through a fertilisation mechanism that is coupled with the IME with potential implications for conservation and fisheries.

The Future of Fisheries

2019 ◽  
pp. 179-184
Author(s):  
Ray Hilborn ◽  
Ulrike Hilborn
Keyword(s):  
Food Security ◽  
Fisheries Management ◽  
Economic Efficiency ◽  
Marine Ecosystems ◽  
Fish Production ◽  
Fish Stocks ◽  
The World ◽  
The Future ◽  
Uncertain Future ◽  
Traditional Fishing

The Future of Fisheries. The much-ballyhooed imminent collapse of the world’s fish stocks is simply not borne out by the available data. In much of the world, fish stocks are increasing. We foresee continued fish production wherever there is effective fisheries management, but an uncertain future where there is none, and it is there that establishing effective fisheries management is the most pressing issue. Individual countries and their management agencies will increasingly be challenged to decide between economic efficiency and maintaining traditional fishing communities and practices. As long as the management systems stay in place and the marine ecosystems remain productive, the fish they produce can be sustainably harvested and contribute to food security.

Use of fish production per unit biomass ratios for measuring the productive capacity of fish habitats

2000 ◽  
Vol 57 (8) ◽  
pp. 1657-1667 ◽  
Author(s):  
R G Randall ◽  
C K Minns
Keyword(s):  
Life History Theory ◽  
Field Studies ◽  
Productivity Index ◽  
Specific Information ◽  
Productive Capacity ◽  
Fish Production ◽  
Size At Maturity ◽  
Eastern Canada ◽  
Habitat Productivity ◽  
Species Specific

Species-specific production rate per unit biomass (P/B, per year) ratios were calculated for 79 freshwater fish species of eastern Canada. P/B (per year) ratios were calculated using two methods, which were based on allometry with fish weight-at-maturity and life expectancy, respectively. P/B (per year) values obtained by the two methods were significantly correlated, as expected from life history theory, since the two predictors (longevity, size-at-maturity) were themselves correlated. Species-specific P/B (per year) ratios were also significantly correlated with field observations of P/B from published sources. The estimation of P/B based on allometry with fish size is recommended because of its utility; the predictive equation is P/B (per year) = 2.64Wmat-0.35, where Wmat is weight-at-maturity. Both the coefficient 2.64 and the exponent -0.35 of this equation are provisional and require further validation from field studies of fish production. More accurate estimates of P/B are possible if population-specific information on size-at-maturity or mean size is known. The product of average fish biomass and estimated P/B coefficients (habitat productivity index (HPI) = B × P/B) is a proposed measure of habitat productive capacity.

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