As the intensity and speed of environmental change increase at both local and global scales it is imperative that we gain a better understanding of the ecological implications of community shifts. While there has been substantial progress toward understanding the drivers and subsequent responses of community change (e.g. lake trophic state), the ecological impacts of food web changes are far less understood. We analyzed Wabash River fish assemblage data collected from 1974-2008, to evaluate temporal variation in body-size structure and functional group composition. Two parameters derived from annual community size-spectra were our major response variables: (1) the regression slope is an index of ecological efficiency and predator-prey biomass ratios, and (2) spectral elevation (regression midpoint height) is a proxy for food web capacity. We detected a large assemblage shift, over at least a seven year period, defined by dramatic changes in abundance (measured as catch-per-unit-effort) of the dominant functional feeding groups among two time periods; from an assemblage dominated by planktivore-omnivores to benthic invertivores. There was a concurrent increase in ecological efficiency (slopes increased over time) following the shift associated with an increase in large-bodied low trophic level fish. Food web capacity remained relatively stable with no clear temporal trends. Thus, increased ecological efficiency occurred simultaneous to a compensatory response that shifted biomass among functional feeding groups.

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Tournament fishing has risen in popularity over the last half a century. As such, social and financial incentives combined with technological advancements are expected to drive changes in angler's capacity to exploit tournament‐eligible fish stocks, as has been observed in commercial fisheries. The aim of this study was to quantify temporal trends in angler efficiency and their ability to exploit a given fish stock relative to effort in largemouth bass fishing tournaments. A collective analysis across seven Illinois reservoirs comparing change through time in angler catch rates and relative population abundances indicated that angler efficiency has generally improved through time. For the decade from 2005 to 2015, a greater than threefold increase in the efficiency of anglers to exploit a static population of largemouth bass was estimated. Anglers have become more efficient at exploiting populations, which is likely to influence management decisions in the future, particularly in harvest‐orientated fisheries and those reliant upon fishery‐dependent surveys.

Artificial habitat structures are used to mitigate habitat loss within aquatic ecosystems and to increase angler catch rates; however, the potential trophic outcomes of concentrating fish at structure additions are rarely evaluated. We compared fish and fish prey assemblages between reservoir coves with and without newly added offshore habitat structures (PVC cubes enclosing 2.25 m3). Further, we tested whether offshore habitat additions changed fish assemblage and abundance in littoral habitats of treated coves. Coves with offshore structures had higher concentrations of fish and an assemblage structure dominated by Pomoxis and Lepomis species at offshore sites compared to coves without offshore structures. There was no evidence for an effect of offshore structures on fish relative abundance and assemblage structure in nearby littoral habitats. Zooplankton and benthic macroinvertebrate abundances did not change because of the addition of habitat structures. Lack of a response of lower trophic organisms may be due to low predation mortality or else losses to predation are replaced by increased prey production or immigration at the offshore structures. Our results indicated that artificial structures effectively concentrated fish, but increases in fish density may be partitioned among newly available structure in offshore habitats and existing structure within littoral habitats. Future studies are needed to test for a relationship between foraging space and food resources provided by artificial habitats, which may be useful for optimizing the number, size, and material composition of structures used in habitat enhancement programs.