Metadata

Description
Detailed methods are described in the associated manuscript, (Contrasting invasion histories and effects of three non-native fishes observed with long-term monitoring data), its supplementary file, and publications cited within. In summary, long-term monitoring sites were established across the Everglades as part of the Modified Water Deliveries to Everglades National Park project. From July 1996 through April 2022 fish and invertebrates were collected using 1-square meter, 2-mm mesh, throw traps following standardized protocols at three sites in Taylor Slough, six sites in Shark River Slough, and eight sites in Water Conservation Area 3A. Each site consisted of three plots, except for two sites in Taylor Slough that consisted of five plots. In Taylor Sough and Shark River Slough, seven throw-trap samples were collected at each plot during each sampling period except when sites were only accessible by helicopter and five throw-trap samples were collected. In Water Conservation Area 3A, five throw-trap samples were collected at each plot during each sampling period. Our analyses here are on plot-level mean densities of small fishes and decapods. Samples were collected during five months of each year, starting after the onset of the wet season (begins in June), with wet-season samples collected in July and October, transition period samples collected in December, and dry-season samples collected in February and April. Animals were removed from throw traps following a standard protocol using bar seines and dip nets; vertebrates were euthanized using MS-222 and all animals were fixed in formalin before being transferred to ethanol and identified. From 1997–2021, the nine central/deeper plots in Taylor Slough, plots at five of the sites in Shark River Slough, and plots at six of the sites in Water Conservation Area 3A were sampled with an airboat-mounted electrofisher for three transects of five minutes (pedal time) to assess large fishes (>8 cm standard length) providing catch-per-unit-effort (CPUE) relative abundance values. Native fishes were released and non-native fishes were euthanized following each electrofishing transect. Electrofishing CPUE data were used to assess predator effects in supporting analyses. Dry-season electrofishing sampling is limited most years because airboats cannot access sites (throw-trap sampling continues when accessed by helicopter). To partially overcome limitations of missing dry-season sampling, we created indices of annual predator CPUE caught via electrofishing by averaging the total number of fish caught across all electrofishing transects during both wet-season sampling periods (July, October).