Abstract
Results from a 30-year study of fish and crustacean abundance at Hinkley Point,
Somerset, England are reported. Standard community ecology metrics, including
annual total species number recorded, alpha diversity and dominance indices, the
rank-abundance curve and the assemblage of permanently present species, have
all shown notable stability and no trend over the study period. In contrast,
community structure has shown clear change which can be related to the fact
that the abundances of many species have shown long-term trends. Of the 30
most abundant species, which together comprise more than 99% of the total
species number and biomass collected, 17 have shown a long-term trend in log
abundance indicative of exponential change. 9 species have shown approximately
exponential increases, and 8 exponential decreases in abundance. This
remarkable variation in individual species' abundance has been shown for some
species to be related to changes in sea water temperature, the North Atlantic
Oscillation Index, and salinity. While annual species richness has not increased,
the number of species present each month has, on average, increased. This has
been caused by changes in seasonal presence, with summer-autumn species
extending their presence further into the winter. For fish, the dominant species
show no trend, and it is argued they are likely to be under density-dependent
control. It may be that while the most abundant species are constrained by
resources, the majority of less abundant forms are dynamically unstable and more
likely to be responsive to environmental change.
Keywords:
Bristol Channel,
Community ecology,
Environmental change,
Fish,
Impingement,
Macro-crustaceans,
Population dynamics,
Power station,
Severn estuary
http://dx.doi.org/10.1016/j.jembe.2011.02.028
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