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Long-term dynamics of the northern Humboldt Current System pelagic fish
community: a look into community shifts
Abstract
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The northern Humboldt Current System (nHCS) is an area with high
environmental variability that impacts key demographic and
community-scale processes. Understanding the role and ecological
implications of these interannual or long-term events is crucial in
describing the dynamics of the nHCS community. Using catch data from
pelagic assessment surveys from 1983 to 2019 and the community
trajectory analysis framework, we tested and characterised the patterns
and compositional dynamics of the nHCS pelagic fish community over space
and time. Spatially, changes were evaluated for ecological regions with
similar community composition identified through hierarchical clustering
with spatial constraint. We found that the community is in constant
inter-annual variability consistent with the long-term warm and cold
periods of the system. A long trajectory segment suggests a community
regime shift between 1994 and 1999, years associated with a change in
the average oceanographic conditions in the system and an extreme El
Niño event (1997-98). After 1999, we identified a period where the
community was constantly changing and dominated by coastal species.
These long-term community changes were not homogeneous over the
ecological areas, finding a lower temporal variability in the coastal
area than in the northern and offshore. The main factor controlling the
spatial and temporal dynamics of the nHCS pelagic fish community seems
to be the long and short-term environmental conditions in the system.
This study helps to understand the magnitude and direction of pelagic
fish community changes and define the community’s recovery process after
an event-driven change.