Why the Atlantic cod (<i>Gadus morhua</i>) stock off eastern Nova Scotia has not recovered

Fu, Caihong; Mohn, Robert; Fanning, L. Paul

doi:10.1139/f01-095

Cited by 76 publications

(75 citation statements)

References 18 publications

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“…Inbreeding remains an unlikely explanation for high F IS in fish with large populations such as gobies that are not subject to drastic reduction in their effective population sizes like commercial fishes (Fu et al, 2001;Hoarau et al, 2002). Nevertheless, polygyny and polyandry, which are known to be common features in gobies (Lindström and Seppä, 1996), could be responsible for inbreeding because some of the parents might dominate the progeny (see Zeh and Zeh, 2001).…”

Section: Discussionmentioning

confidence: 99%

Evidence for fine-scale genetic structure and estuarine colonisation in a potential high gene flow marine goby (Pomatoschistus minutus)

et al. 2004

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Marine fish seem to experience evolutionary processes that are expected to produce genetically homogeneous populations. We have assessed genetic diversity and differentiation in 15 samples of the sand goby Pomatoschistus minutus (Pallas, 1770) (Gobiidae, Teleostei) from four major habitats within the Southern Bight of the North Sea, using seven microsatellite and 13 allozyme loci. Despite its high dispersal potential, microsatellite loci revealed a moderate level of differentiation (overall F ST ¼ 0.026; overall R ST ¼ 0.058). Both hierarchical analysis of molecular variance and multivariate analysis revealed significant differentiation (Po0.01) between estuarine, coastal and marine samples with microsatellites, but not with allozymes. Comparison among the different estimators of differentiation (F ST and R ST ) pointed to possible historical events and contemporary habitat fragmentation. Samples were assigned to two breeding units in the estuary and coastal region. Despite this classification, there were indications of a complex and dynamic spatiotemporal structure, which is, most likely, determined by historical events and local oceanic currents.

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Section: Discussionmentioning

confidence: 99%

Evidence for fine-scale genetic structure and estuarine colonisation in a potential high gene flow marine goby (Pomatoschistus minutus)

et al. 2004

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“…More recently, the rapid, post-World War II development of industrialized fisheries has greatly increased fishing pressure and has led to numerous recent declines in large-bodied predators around the globe (e.g. Fu et al 2001, Pauly et al 2002, Myers & Worm 2003, Lotze & Milewski 2004, Bundy 2005. Removal of large-bodied predators can result in community change, either through competitive or predator release, which is occasionally further modified by climatic effects (e.g.…”

Section: Introductionmentioning

confidence: 99%

Compensation in exploited marine fish communities on the Scotian Shelf, Canada

Shackell¹,

Frank²

2007

Mar. Ecol. Prog. Ser.

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We evaluated the temporal dynamics of the aggregate groundfish community, further decomposed into functional groups, individual species abundances, and health indicators, from adjacent management units on the Scotian Shelf. On the colder, eastern half of the shelf, several species collapsed in the early 1990s, while, on the western half, no such collapses were evident despite similar exploitation regimes. The decline in the eastern aggregate biomass was influenced by a decline in average body size, which was interpreted as a past integrator of temperature and size-selective fishing. Biomass of 3 out of 4 functional groups declined in the east; 3 out of 4 groups increased in the west. Some species from the east appear to be slowly compensating, but not enough to counter the decline in aggregate biomass. Species inhabiting the warmer western region show strong evidence of compensation. In effect, warmer waters allow potential compensating species to increase at a faster rate. Quantitative measures of functional group temporal stability revealed no differences between areas; therefore, neither area can be considered stable. Physiological condition declined in many species in both regions. Species that increased in the west, or had slower rates of decline, had higher levels of condition than eastern populations. With the exception of cod in the western region, species growth rates declined in both areas. Although the west appears more stable, it is following a similar, but protracted trajectory, to that found in the east. The protracted response in the west may be due to higher demographic rates in warmer waters. To foster resilience in the western area, we should address the rapid pace of new fisheries, effects of size-selective mortality, and the diminishing number of natural refugia.

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“…For example, no sand lance were caught in the surveys conducted in 1992-1994, yet this species accounted for over 60% of the estimated diet in those years. Similarly, over the period of our study Atlantic cod biomass declined (Fu et al 2001), but there is only weak evidence of declining trend in the importance of cod in the diet of grey seals. By contrast, consumption of longhorn sculpin, silver hake, and capelin all increased in 1 or Table 6.…”

Section: Discussionmentioning

confidence: 47%

Seasonal and interannual variability in grey seal diets on Sable Island, eastern Scotian Shelf

Bowen

Harrison

2007

NAMMCOSP

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We studied seasonal and interannual variability in the diet of grey seals (Halichoerus grypus) using faecal samples collected from Sable Island, Nova Scotia between 1991 and 1998. More than 28,000 prey from at least 28 taxa were identified from 1,245 faecal samples collect mainly in spring, fall and winter. Sand lance (Ammodytes dubius) dominated the diet in all season and years, but the importance of this and other species varied over time. There was also evidence of seasonal and interannual variation in the size of prey consumed both within and among species. We compared diet composition with estimates of prey numbers and biomass from annual research trawl surveys conducted in March and July. Species-specific numerical corrections were applied to otolith counts to account for the complete digestion of otoliths, and fish catchability correction factors applied to trawl survey catches to account for trawl selectivity. Based on an odds ratio index of prey selectivity, grey seals positively selected sand lance in both seasons. Other species were either relatively avoided or eaten roughly in proportion to their estimated abundance.

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Why the Atlantic cod (Gadus morhua) stock off eastern Nova Scotia has not recovered

Cited by 76 publications

References 18 publications

Evidence for fine-scale genetic structure and estuarine colonisation in a potential high gene flow marine goby (Pomatoschistus minutus)

Evidence for fine-scale genetic structure and estuarine colonisation in a potential high gene flow marine goby (Pomatoschistus minutus)

Compensation in exploited marine fish communities on the Scotian Shelf, Canada

Seasonal and interannual variability in grey seal diets on Sable Island, eastern Scotian Shelf

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