LB 23-246 - Characterizing the spatial and temporal dynamics in the pelagic fish community of the northern Humboldt Current System

Background/Question/Methods:

It is of general interest to ecologists to quantify and describe the changes in court or long-term scales of the spatial structures of a community and how they respond to disturbances. For instance, the northern Humboldt Current System (nHCS) is an area where climate change and environmental variability are most notable, modifying key physiological, demographic, and community-scale processes, thus driving species redistribution at a global and local scale. Understanding the role and ecological implications of these interannual or decadal events is vital in describing the dynamics of the nHCS pelagic fish community. Through the community trajectory analysis framework, we tested and characterized, over time, the spatial patterns and compositional dynamics of the pelagic fish community under study. Changes were evaluated at local scales in addition to community ecological regions, these last developed through hierarchical spatial clustering. We used data from pelagic assessment surveys carried out by the Instituto del Mar del Peru from 1983 to 2018.

Results/Conclusions:

We found that the interannual trajectories highlight the decadal dynamics of the community. An extended segment described the regime shift of the system from 1990 to 1991. The transition from 1997-1998 to 1999 represents the years associated with an El Niño extreme event, followed by a long period where the directionality values were low, whit local communities deviating and returning to previous states. However, only the offshore ecological region described this particular variability on the whole community. The main factor controlling the spatial and temporal dynamics of the nHCS pelagic fish community seems to be the environmental stability of the system. This study helped track the magnitude and direction of those ecological changes and define the community's recovery process after an event-driven change.