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  • 1
    Online Resource
    Online Resource
    Canadian Science Publishing ; 1999
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 56, No. 12 ( 1999-12-01), p. 2350-2361
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 56, No. 12 ( 1999-12-01), p. 2350-2361
    Abstract: In southwestern Nova Scotia, haddock (Melanogrammus aeglefinus) spawning is centered on Browns Bank where the variability of a partial gyre influences the distribution of eggs and larvae. An unknown proportion of each year-class is advected northward to the Bay of Fundy. We examined the variability in length at age 2 as an index of retention during early life. We assumed that early life stages that are retained in the Scotian Shelf area grow more slowly, while those that are advected into the Bay of Fundy grow more quickly. An optimization program was used to estimate the proportions of Scotian Shelf and Bay of Fundy sized components in length at age 2 bimodal frequency distributions for year-classes 1968-1993. The median proportion of Scotian Shelf sized fish was 0.89. A physical circulation model showed that the majority of particles released on Browns Bank drifted towards the Bay of Fundy. Results of the physical model and the size-based index differ partly because the former predicts the fate of passive particles, while the latter is an integrated measure of the proportion of fish retained and surviving. Survival is associated with high wind stress (r = -0.5, p = 0.011, n = 25) implying a higher probability of survival of those retained in the Scotian Shelf region.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 1999
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
    SSG: 21,3
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Wiley ; 2006
    In:  Ecology Letters Vol. 9, No. 10 ( 2006-10), p. 1096-1105
    In: Ecology Letters, Wiley, Vol. 9, No. 10 ( 2006-10), p. 1096-1105
    Abstract: The dependence of long‐term fishery yields on primary productivity, largely based on cross‐system comparisons and without reference to the potential dynamic character of this relationship, has long been considered strong evidence for bottom‐up control in marine systems. We examined time series of intensive empirical observations from nine heavily exploited regions in the western North Atlantic and find evidence of spatial variance of trophic control. Top‐down control dominated in northern areas, the dynamics evolved from bottom‐up to top‐down in an intermediate region, and bottom‐up control governed the southern areas. A simplified, trophic control diagram was developed accounting for top‐down and bottom‐up forcing within a larger region whose base state dynamics are bottom‐up and can accommodate time‐varying dynamics. Species diversity and ocean temperature co‐varied, being relatively high in southern areas and lower in the north, mirroring the shifting pattern of trophic control. A combination of compensatory population dynamics and accelerated demographic rates in southern areas seems to account for the greater stability of the predator species complex in this region.
    Type of Medium: Online Resource
    ISSN: 1461-023X , 1461-0248
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2006
    detail.hit.zdb_id: 2020195-3
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    Elsevier BV ; 2007
    In:  Trends in Ecology & Evolution Vol. 22, No. 5 ( 2007-5), p. 236-242
    In: Trends in Ecology & Evolution, Elsevier BV, Vol. 22, No. 5 ( 2007-5), p. 236-242
    Type of Medium: Online Resource
    ISSN: 0169-5347
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2007
    detail.hit.zdb_id: 1498910-4
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    The Royal Society ; 2010
    In:  Proceedings of the Royal Society B: Biological Sciences Vol. 277, No. 1686 ( 2010-05-07), p. 1353-1360
    In: Proceedings of the Royal Society B: Biological Sciences, The Royal Society, Vol. 277, No. 1686 ( 2010-05-07), p. 1353-1360
    Abstract: Globally, overfishing large-bodied groundfish populations has resulted in substantial increases in their prey populations. Where it has been examined, the effects of overfishing have cascaded down the food chain. In an intensively fished area on the western Scotian Shelf, Northwest Atlantic, the biomass of prey species increased exponentially (doubling time of 11 years) even though the aggregate biomass of their predators remained stable over 38 years. Concomitant reductions in herbivorous zooplankton and increases in phytoplankton were also evident. This anomalous trophic pattern led us to examine how declines in predator body size (approx. 60% in body mass since the early 1970s) and climatic regime influenced lower trophic levels. The increase in prey biomass was associated primarily with declines in predator body size and secondarily to an increase in stratification. Sea surface temperature and predator biomass had no influence. A regression model explained 65 per cent of prey biomass variability. Trait-mediated effects, namely a reduction in predator size, resulted in a weakening of top predation pressure. Increased stratification may have enhanced growing conditions for prey fish. Size-selective harvesting under changing climatic conditions initiated a trophic restructuring of the food chain, the effects of which may have influenced three trophic levels.
    Type of Medium: Online Resource
    ISSN: 0962-8452 , 1471-2954
    Language: English
    Publisher: The Royal Society
    Publication Date: 2010
    detail.hit.zdb_id: 1460975-7
    SSG: 12
    SSG: 25
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  • 5
    Online Resource
    Online Resource
    Wiley ; 2008
    In:  Ecology Letters Vol. 11, No. 9 ( 2008-09), p. 883-897
    In: Ecology Letters, Wiley, Vol. 11, No. 9 ( 2008-09), p. 883-897
    Abstract: Poleward declines in species diversity [latitudinal diversity gradients (LDG)] remain among the oldest and most widespread of macroecological patterns. However, their contemporary dynamics remain largely unexplored even though changing ecological conditions, including global change, may modify LDG and their respective ecosystems. Here, we examine temporal variation within a temperate Northwest Atlantic LDG using 31 years of annual fisheries‐independent surveys and explore its dynamics in relation to a dominant climate signal [the wintertime North Atlantic Oscillation (NAO)] that varies interannually and alters the latitudinal gradient of Northwest Atlantic continental shelf bottom water temperatures. We found that the slopes of the annual LDG vary dramatically due to changes in geographic distributions of 100+ species, variations that are concealed within the cumulative, static LDG. These changes are strongly associated with changes in NAO sign and strength. This is the first illustration of temporal dynamics in a contemporary LDG and the first demonstration of the speed at which local environmental variations can alter an LDG. Our findings underscore the need to investigate factors that modify LDG separately from those that contribute to their origins.
    Type of Medium: Online Resource
    ISSN: 1461-023X , 1461-0248
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2008
    detail.hit.zdb_id: 2020195-3
    SSG: 12
    Location Call Number Limitation Availability
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