COS 42-5
Non-equilbrium dynamics of near shore fish communities in Lake Huron
We studied temporal changes of fish communities at five different sampling locations in Lake Huron to determine if these communties exhibited complex non-equilbrial behavior. Surveys using nets of varying mesh size were conducted yearly at each location generating time series from fifteen to thirty three years. Total catch for each of thirteen species were standardized. Dynamic factor analysis was used on standardized abundances to estimate latent trends across all species in the communties at each sampling location. Models assuming one, two, and three latent trends were compared using corrected AIC values. Calculations were done using the R package MARRS.
Results/Conclusions
Two latent trends were identified that were relatively consistent across sites. The first trend corresponded to species that declined in the early 1980's and leveled out thereafter. The second trend corresponded to species which initially increased, then began declining after about 1995. There were no consistent life history attributes for the species that were associated with each of these trends that might correspond to "guilds" or groups of species that might respond to environmental change in ways obvious from their autecologies. The overall impact of these changes suggested that there had been a community wide decline in abundance over the past few decades that was accompanied by a fundamental reorganization of community structure. Our results are inconsistent with dynamical behavior that would be expected from random or cyclic fluctuations of abundances of species around well-defined equilibria.