Methods

Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>

Methods

Adult rusty crayfish were trapped in August of 2001 and from June-August of 2002-2011 using Gee-style minnow traps modified by widening the openings and baited with beef liver or frozen fish following (Capelli and Magnuson 1983). Between 30-313 (mean=149) traps were set at 43 sites around the perimeter of the lake at the 1 m depth contour, with higher concentrations of traps in locations of higher crayfish abundance (Hein et al. 2007). Traps were emptied daily from 2001-2003 and every 1-4 days from 2004-2011 as catch rates declined. From 2001-2008 all trapped rusty crayfish were removed, and all native virile crayfish (Orconectes virilis) were released. From 2009-2011 trapping continued but all crayfish were released. Catch per unit effort (CPUE) of each crayfish species is used as an index of adult crayfish abundance, and was calculated daily (total crayfish caught/total trap days).
Capelli G.M. and Magnuson J.J. (1983) Morphoedaphic and Biogeographic Analysis of Crayfish Distribution in Northern Wisconsin. J. Crustacean Biol., 3, 548-564
Hein C.L., Vander Zanden M.J. and Magnuson J.J. (2007) Intensive trapping and increased fish predation cause massive population decline of an invasive crayfish. Freshwater Biol., 52, 1134-1146

Methods

To control for sampling methodology and allow comparisons among native and invasive species, we only included data where both invasive and native species from a taxonomic group were sampled using the same methods across multiple sites. Exceptions were made to include rusty crayfish (Orconectes rusticus) in its native range and zebra mussel (Dreissena polymorpha) data. Native rusty crayfish data were obtained from (Jezerinac 1982). Zebra mussel data were mainly obtained from a meta-analysis (Naddafi et al. 2011) which compiled data from 55 European and 13 North American sites from 1959-2004. Additional densities from North America were compiled from multiple primary literature sources (Table S3). All zebra mussel records were presented as number per m2 and are from their invaded range; we did not include native mussel data.Crayfish data were obtained from multiple sources. Crayfish were collected in Wisconsin, USA during summers of 2002-2010 from lakes in the Northern Highlands Lake District following their protocol for crayfish collection. Crayfish were sampled in Wisconsin streams tributary to Lake Michigan from 2007-2010 using 10 gee-style minnow traps per site baited with chicken livers and set overnight. Swedish crayfish were sampled using 30 minnow traps baited with frozen fish in lakes and streams of southern Sweden from 2001-2003 as described in (Nystrom et al. 2006). Washington crayfish were collected from 100 lakes in the Puget Sound Lowlands region of Washington State, USA between 2007 and 2009 from mid-June to early October of each year. At each lake, the investigators set 20 minnow traps baited with fish-based dog food. Traps were deployed in four clusters of five traps each and recovered the following day. All crayfish densities are presented as number per trap per day, with the exception of native range rusty crayfish data, which were reported as number per site (Jezerinac 1982) and excluded from all comparisons that depend on sampling units.Wisconsin fish data were collected from streams throughout the state from 2005-2010 using either a backpack or towboat electrofisher with pulsed DC current in wadeable (less than1m depth) streams for a minimum of 15 minutes. For Wisconsin trout species, locations sampled within 10 years following a stocking event of that species were excluded. Lamprey data were collected from 2008-2010 from Great Lakes tributaries using backpack electrofishers following standardized methods as a part of the sea lamprey assessment program of the United States Fish and Wildlife Service and Department of Fisheries and Oceans, Canada. North American fish densities are presented as number per minute of sampling. Swedish fish data were collected using backpack electrofishing between 1980 and 2010 from streams in Vasterbotten county, northern Sweden, and were obtained from the Swedish Electrofishing REgister (SERS), www.fiskeriverket.se, and are reported as number per 100 m of stream.Snail data were collected in 2006 from lakes in the Northern Highlands Lake District in Wisconsin as described by (Solomon et al. 2010), and densities are presented as number per two m2. Aquatic plant data were collected using a systematic grid-based point-intercept sampling methodology to record macrophyte frequency of occurrence in 242 Wisconsin lakes from 2005-2008. Aquatic plant presence absence was recorded from a boat using a double-sided rake sampler at each point on a sampling grid as described in (Mikulyuk et al. 2010). Density data are presented as proportion of sites within lake littoral zone where a species was present.For all data, if multiple records existed from the same location, we used the most recent record. If replicate samples existed within the same site on the same sampling date, the mean value was used.

Methods

CRAYFISH AND MINNOW TRAPS There have been introductions of exotic crayfish species in recent years into many north temperate lakes. Monitoring yearly abundances of crayfish species is important in determining the status and extent of the invasions.Crayfish traps are set on all lakes except the bog lakes (Crystal Bog and Trout Bog). Minnow traps are set only on the bog lakes. Prior to 1998, five traps were set at each fyke net site. Starting in 1998, three traps are set per site. Thus, prior to 1998, thirty traps were set on each lake (covering 6 sites.) As of 1998, 18 traps are set on each lake.Minnow traps and crayfish traps are set in shallow water (approx 1 m), 2 traps on one side, and 1 trap on the other side of the fyke net lead. Minnow traps are baited with 1 slice of bread per trap to attract minnows inhabiting the bogs. Crayfish traps are baited with 120 g of liver. Traps are fished for approximately 24 hours . Crayfish are identified to species and returned to the lake, except 2001 - 2008 when in Sparkling Lake Rusty Crayfish (Orconectes rusticus) was removed. Minnows caught in either the crayfish or minnow traps are identified to species, measured for total length.Minnow traps used are galvanized steel two piece traps, 44.5 cm long by 30.5 cm maximum diameter with 2.5 cm diameter openings at the ends. The mesh size is 6.4 mm on a side. Crayfish traps are identical, but the opening hole of both sides of the trap has been forced to 5 to 7 cm.

Methods

Two approaches for trapping were used in the initial phase of this study: removal trapping and &quot;standardized surveys&quot;. Traps set for removal of rusty crayfish were concentrated in areas of the lake to maximize catch rates. In 2001, removals began on 14 August 2001 and traps were emptied daily during the last 2 weeks of August. From 2002 on, crayfish are trapped and removed from mid to late June through late August. Traps are wire mesh minnow traps with openings widened to 3.5-cm diameter. (In 2001, other traps and trapping methods were also evaluated.) Traps are baited with 4- 5 dead smelt.Removal traps were set in arrays of 10 at 10-m intervals along the 1-m depth contour, and were emptied daily during during 2001 - 2003 and every 1 to 4 days starting in 2004. Removal traps were concentrated on the southern and western shorelines of the lake where catch rates are highest from 2001-2004. From 2005-2008, traps were set around the entire perimeter of the lake. From 2001 to 2004 the sex of each crayfish in a trap was recorded, and a randomly selected subsample of the daily crayfish catch was used to estimate mean size. From 2005-2008, the number of crayfish in each trap was recorded, and a randomly selected subsample of 50 individuals was measured and their sex was determined.To assess the environmental predictors of rusty crayfish catch rates, &quot;standardized surveys&quot; were conducted prior to harvest in 2001 through 2006. Standardized surveys were comprised of perimeter trapping and depth trapping. Although perimeter trapping occurred every year, depth trapping only took place in 2001 and 2003. For perimeter trapping, 43 traps were baited with 120 g of beef liver and set for 24 hours at 1-m depths at 100-m intervals along the shoreline. Perimeter traps were set on 6 dates in June through August. Three days after the June and July perimeter trapping events, 14 depth transects were set around the perimeter of the lake. Depth transects were spaced 300-m apart and along the transect, traps were set at 0.5, 3, 5, 8 and 12-m depths. Perimeter trapping at the 43 sites, but not the associated depth transect trapping, was done on four dates in 2002 and continued to be done for three to five dates annually through 2006.Trap_id: During removal trapping, from 2001-2004 10 traps were set at each of the standard trapping sites. For years 2001- 2004, the trap_id of removal traps includes additional information about the spatial location of the trap. The first number of the trap_id indicates the trap site (1 to 43) and the number after the dash identifies which trap of 10 was pulled from the site as you move clockwise around the lake. For example, trap 12-1 is at the flagpost of site 12, trap 12-5 is approximately halfway between sites 12 and 13, and trap 12-10 is just before you arrive at site 13.Starting in 2005, the removal traps are distributed equally around the lake starting at trap site 1 and proceeding in a clockwise direction. These traps are given trap_ids of sequential numbers as they are lifted. These trap_ids do not relate directly to the trap site. However, you can calculate the approximate trap site for each trap by knowing the total number of traps set over the 43 standard trap sites. In 2005, a total of 277 traps were initially set. In 2006, 220 traps were set over the 43 sites. During the initial retrieval in 2006, data were grouped for each of the 22 sets of 10 traps. To make these data comparable to the rest of the removal trap data, the crayfish represented in the grouped data were assigned randomly to individual traps within the 10 trap set. In 2007, the maximim trap_id was 269. In 2008, the maximum trap_id was 289.Removal: Traps set annually at 43 sites around the lake and fished through the trapping season. In 2002, additional single traps were set near logs and other likely places which were not in close proximity to other traps. These traps have -MIN appended to the trap number in TRAP field.Perimeter: Traps set annually (through 2006) on standard arrays at 43 sites around the lake at 1 m deep for a limited number of days. The last year perimeter traps were used was 2006.Depth Transect: Traps set on standard arrays that ranged from 0.5 to 12 m deep. Depth transects were set in 2001 and 2003 only.Lead: Traps were set at the ends of a &ldquo;lead&rdquo; made of aluminum flashing and staked to the bottom of the lake in 2001 only. Experiment was to see if the flashing would be a barrier to the crayfish, and would lead crayfish into small minnow traps. Traps were set at different depths. Leads were set at survey sites: 7, 15, and 26. (Site is indicated in the TRAP field for these traps). Traps were set at each end of the lead and along the middle, as indicated by the depth they were set.Minnow: Minnow traps set in 2001.Commercial: Experimental large box traps used only in 2001.Wik: Traps designed by Don Wik and used in 2002 only. These were square traps with trapezoid-shaped ends, and an entrance on the top of the trap.References:Hein, Catherine L., Brian M. Roth, Anthony R. Ives, and M. Jake Vander Zanden. 2006. Fish predation and trapping for rusty crayfish (Orconectes rusticus) control: a whole lake experiment. Canadian Journal of Fisheries and Aquatic Sciences: 63 383-393Hein, Catherine L., M. J. Vander Zanden, John J. Magnuson. 2007. Invasive trapping and increased fish predation cause massive population decline of an invasive crayfish. Freshwater Biology:
Update 2021
Table biocom_crayfish_daily_station was extened by summarising 2001-2006 data from biocom_crayfish_individual. New data are added for 2011-2019

Methods

Littoral Zone Surveys: Littoral habitat, fish and macrophyte surveys were performed at eight sites within each of the 55 lakes. The sites were chosen by randomly selecting two points per compass quadrant of each lake. Each year littoral habitat surveys were conducted in June, fish surveys in July and macrophyte surveys in August.Littoral fish were sampled in July of each year, along the shallow areas (water depth greater than 0 and less than2 m) adjacent to the riparian plots. Night electroshocking and crayfish and minnow traps were used to catch fish and crayfish. All species were identified and counted.