Publication Date:
2016-01-23
Description:
The analysis of biomass time-series from standardized surveys, particularly comparing patterns of variation and their supposed relationship with drivers, can provide insight into how fish species and communities as a whole respond to environmental, trophic, and fishing-related drivers of change in ecosystems. Here we describe and compare the common patterns of temporal variations in demersal fish communities among three distinct ecoregions of the Gulf of St Lawrence (GSL; Atlantic Canada) for 1990–2013, a period during which many commercial groundfish stocks collapsed due to fishing and subsequently failed to recover. Dynamic factor analysis was used to estimate common trends in biomass densities, to assess synchrony among species, and to investigate the influence of key drivers on those trends. The analyses revealed similar temporal patterns of variations for all regions: the trends fluctuated between periods of negative and positive slopes with transitions around the late 1990s or early 2000s and again in the late 2000s. Over the last two decades, the effect of predation by seals was more important than an effect of fishing, especially in the southern GSL. Warming trends in the upper layer of the water column and in the deep water masses may have affected the dynamics of species in those communities, especially in the northern GSL. Fluctuations in the biomasses of two important commercial species (Greenland halibut Reinhardtius hippoglossoides and Atlantic halibut Hippoglossus hippoglossus ) influenced trends in all regions. The effect of weakly exploited and non-commercial species appeared more important late in the series, and the species associated with trends varied according to the region. However, the rarity of many small-demersal species from the bottom-trawl surveys in the northern GSL may limit detection of changes in this community.
Print ISSN:
1054-3139
Electronic ISSN:
1095-9289
Topics:
Biology
,
Geosciences
,
Physics
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