Dataset DOI: 10.5061/dryad.qnk98sfwg

Description of the data and file structure

Data include counts of crabs and clams from Willapa Bay, Washington, USA in 2024. The crab species were mostly non-native European green crabs (Carcinus maenas) and native Dungeness crab (Metacarcinus magister). The clam species were mostly non-native Manila clams (Ruditapes philippinarum) and non-native soft-shell clams (Mya arenaria). Sites and dates of sampling are included in the data tables. Some data were observational, specifically clam recruitment and crab catch in traps. Other data were experimental, specifically clam densities inside and outside netting that excluded predators.

Files and variables

File: 2024_ClamRecruitment.csv

Description: Clam recruitment in 2024 in Willapa Bay, Washington, USA, was recorded monthly in replicate standardized substrates, which were mesh bags (1 mm mesh, 15 x 10 cm dimension) filled with pea gravel. At each of eight sites, five seasonal bags were placed initially and left in place beyond the summer recruitment season. Additionally, five bags were replaced monthly. Bags were spaced at 10-m intervals, lying on the sediment and kept in place by a loop around a short pole. All bags, seasonal and monthly, were set out 21-22 May 2024. Monthly bags were replaced each month, 18 June, 18 July, and 15-16 August, with the final pick-up on 18-19 September 2024. The seasonal bags were retrieved 11 January 2025.

Collected bags were processed for newly-recruited clams by using a sieve series of 4000, 2000, 500, and 250-micron sizes. The larger mesh size excluded the pea gravel, and the samples were sprayed vigorously with freshwater to move material through the sieve series. For bags collected monthly, material on the 500- and 250-micron sieves was examined for clam recruits under a dissecting microscope (10x). Manila and soft-shell clams were identified and counted, and counts were also made of other clam species. The smallest sieve mesh for monthly samples likely missed the newest settlers, which can be <200 microns, but smaller sieves also catch most of the sediment (sand), making samples infeasible to sort in the time available for this project. For seasonal bags, only 500- and 2000-micron sieves were examined since the clams would have grown to several mm since settlement. The clam species were Manila clams (Ruditapes philippinarum (A. Adams & Reeve, 1850)) and soft-shell clams (Mya arenaria L. 1758); counts of other clam species constituted 6.3% of all recruited clams in the study. Counts of the focal clam species are distinguished by the size of the mesh on which they were caught; NA= not available because that size fraction was not sorted.

Variables

• Date.Start: Date when bags of gravel were placed on the tidal flat
• Date.Collected: Date when bags of gravel were collected from the tidal flat
• Sample.ID: Code denoting the placement of the bag within a site
• Site: Code denoting which of the eight sites
• Latitude: WGS84 geoposition of the bag of gravel in north latitude
• Longitude: WGS84 geoposition of the bag of gravel, where a negative sign denotes west longitude
• Manila.Count.2000micron: Counts of Manila clams caught on 2000 micron sieve
• Manila.Count.500micron: Counts of Manila clams caught on 500 micron sieve
• Manila.Count.250micron: Counts of Manila clams caught on 250 micron sieve
• Softshell.Count.2000micron: Counts of soft-shell clams caught on 2000 micron sieve
• Softshell.Count.500micron: Counts of soft-shell clams caught on 500 micron sieve
• Softshell.Count.250micron: Counts of soft-shell clams caught on 250 micron sieve

File: 2024_smallexclosure.csv

Description: Predator access to clams was manipulated in a field experiment conducted at eight sites in Willapa Bay, Washington, USA. All experimental units consisted of window-screen mesh boxes (20 x 20 x 10 cm), dug into the sediment, and then local sediment was placed inside the unit. Each unit was covered by sewing Vexar mesh (1 cm mesh) to two sides at the top. Once sediment was added to exclosures in the field, the top was fully closed by connecting to the two remaining sides with zip-ties. The Vexar mesh of control (open) units had two large cuts, 3 cm x 10 cm, allowing predators to enter and exit the unit. Before the units were sealed in the field, five large local Manila clams, ~40 mm, and 20 small hatchery-raised Manila clams (6.27 mm, SD 2.41, N=25) were placed into each unit. Large clams were pushed into the sediment, while small clams were covered by additional substrate. The experiment was deployed 11-12 July and collected 23- 24 August 2024 for a total of 6 weeks. At collection, units were sieved (to 2 mm), and the remaining substrate was sorted by hand, identifying and measuring all live clams, including Manila, soft-shell, and other clams. Each row of data represents one live clam in the experimental unit that was measured for shell length at the end of the 6-week experiment.

Variables

• Date.Collected: Date when the experimental unit was retrieved
• Site: Code denoting which of the eight sites
• Latitude.WGS84: WGS84 geoposition of the experimental site in north latitude
• Longitude.WGS84: WGS84 geoposition of the experimental site, where a negative sign denotes west longitude
• Unit : Code denoting the experimental unit within a site
• Treatment: "open" for procedural control in which the mesh top has holes that allow predator access; "exclosure" for complete mesh top on experimental unit
• Species: Identification of clam species, specifically "Manila" for Ruditapes philippinarum, "softshell" for Mya arenaria, "Macoma" for Macoma spp.
• Size.class: Maximum shell length of the clam individual as a categorical variable, specifically "Large" if >30 mm and "Small" if <20 mm
• Length.mm: Maximum shell length of clam individual (mm)

File: 2024_CrabTeam_WB.csv

Description: Captures of European green crabs observed within the WSG Crab Team monitoring dataset in Willapa Bay during the 2024 sampling season. Each row in this table summarizes trap catch for an "effort" consisting of multiple traps deployed at a single site for one night. Traps at designated monitoring locations were baited and set according to standardized Crab Team protocols (https://wsg.uw.edu/crabteam). For each effort, three traps of two types (a galvanized steel G-40 minnow and a folding square fukui fish trap) were baited with 150-175 g Pacific mackerel for a single night, including a high tide. 

Variables

• Month: Month of capture
• Year: Year of capture
• WaterBody: Water body in which captures took place (Willapa Bay)
• Site: Name of monitoring site
• Branch: Management branch, according to WDFW conventions, in which the site was located
• SiteDetail: Three-digit number code assigned to monitoring site within the WSG Crab Team monitoring network
• EffortType: Type of trapping effort. Sentinel = Crab Team standardized monthly protocols
• TrapSets: Total number of traps set multiplied by number of nights soaking. All traps soaked for one night, so in all cases, 6 individual traps were deployed.
• EGC: Total number of European green crabs (Carcinus maenas) captured during effort. This includes the number of crabs found inside traps and any crabs collected outside of traps by hand during the effort 
• CPUE: Catch per unit effort calculated as 100 times the total number of EGC found within all traps, divided by TrapSets. This is standardized as crabs per 100 trap sets.
• Date.s: Date of trap retrieval and crab captures. Traps were deployed on the preceding date.
• LatitudeDD: WGS84 geoposition in decimal degrees of the experimental site in north latitude
• LongitudeDD: WGS84 geoposition in decimal degrees of the experimental site in longitude, where negative sign denotes west longitude
• Northing: UTM geoposition of the experimental site as northing expressed in meters
• Notes: Notes documenting any deviations or explanations of data from expected protocols 
• RecordStatus: FINAL indicates verified status of record
• Data.Source: What program and data collection device was the source of the information.

File: 2024_WDFW_WB.csv

Description: Trapping data from European green crab monitoring conducted by the Washington Department of Fish and Wildlife in Willapa Bay in 2024. Each row in this table summarizes trap catch for an "effort" consisting of multiple traps deployed at a single site for one or multiple nights. Three trap types were used (Folding square fukui fish traps, galvanized steel Gee-40 minnow traps with opening enlarged to 50mm diameter, and Promar shrimp traps with 25mm mesh size), and each was baited with ca. 100g of mackerel. Traps at designated monitoring locations were baited and set at least 10 meters apart, alternating trap type. Traps may have been set for multiple overnight tides and checked daily, but for consistency, only the first day of trap checking was used in this exploration.

Variables

• Effort_Dates: The date range across which the traps were in the water
• Day1: The date of crab capture, the first date of trap checking.
• Effort_Type: Type of trapping effort; all are monitoring indicating standardized deployment protocols
• Management_Area: Management area, according to WDFW conventions, in which the site was located
• Coordination.Area: Coordination area, according to WDFW conventions, in which the site was located
• Site_Name: Name of site where trapping occurred
• Site_ID: Unique ID number assigned to site
• Waterbody: Water body in which captures took place (Willapa Bay)
• Latitude: WGS84 geoposition in decimal degrees of the experimental site in north latitude
• Longitude: WGS84 geoposition in decimal degrees of the experimental site in longitude, where negative sign denotes west longitude
• North.Cat: Categorical classification of site position relative to the estuarine gradient within Willapa Bay. This denotes whether the site is North or South of the "fattening line" described in the text. 
• Northing: Northing geoposition of reference sample in UTM 10T in meters
• EGC_Total: Total number of European green crabs (Carcinus maenas) captured during effort. This includes number of crabs found inside all traps and any crabs collected outside of traps by hand during the effort.
• Trap_Set_Days: Total number of traps set multiplied by the number of nights soaking.
• Trap_Check_Days: Total number of traps set multiplied by number of times each traps were checked.
• CPUE_TrapSetDays: Catch per unit effort calculated as 100 times the total number of EGC found within all traps, divided by Trap_Set_Days. This is standardized as crabs per 100 trap sets.
• CPUE_TrapChecks: Catch per unit effort calculated as 100 times the total number of EGC found within all traps, divided by Trap_Check_Days. This is standardized as crabs per 100 trap sets.
• EGC_Minnow: Number of green crabs captured in only the minnow traps set during the effort
• Minnow_TrapSetDays: Number of minnow traps set multiplied by number of nights soaking.
• Minnow_TrapChecks: Number of minnow traps set multiplied by number of days the traps were checked (catch removed and trap reset).
• EGC_Fukui: Number of green crabs captured in only the fukui traps set during the effort
• Fukuis_TrapSetDays: Number of Fukui traps set multiplied by number of nights soaking.
• Fukui_TrapChecks: Number of fukui traps set multiplied by number of days the traps were checked (catch removed and trap reset).
• EGC_Shrimp_1: Number of green crabs captured in only the shrimp traps traps (25mm mesh size) set during the effort
• Shrimp1_TrapSetDays: Number of shrimp traps (25mm mesh size) set multiplied by number of nights soaking.
• Shrimp1_TrapChecks: Number of shrimp traps (25mm mesh size) set multiplied by number of days the traps were checked (catch removed and trap reset).
• EGC_Shrimp_ALL: Number of green crabs captured in all the shrimp traps traps (regardless of type of Shrimp trap) set during the effort. In these efforts, only the standard shrimp traps with 25mm mesh size were used, so this is synonymous with EGC_Shrimp_1
• ShrimpALL_TrapSetDays: Number of shrimp traps (of any type) set multiplied by number of nights soaking.
• ShrimpALL_TrapChecks: Number of shrimp traps (of any type) set multiplied by number of days the traps were checked (catch removed and trap reset).
• EGC_Hand: Number of green crabs captured by hand during this trapping effort.
• End_Date: Final date of trapping effort.
• month: Month of year of trapping effort, as numeric

File: TrappingEffort.csv

Description: Dataset collected from synoptic trapping effort conducted at the eight sites where clam recruitment and predator exclusion (small seeded plots) took place. Each row in this table documents all observed catch in a single trap. During this survey, predators were trapped with an overnight soak of baited traps from 2-3 August 2024. At each site, 10 traps were set during low tide, specifically five square Fukui traps (13 mm mesh) and five minnow traps (Gee-40, 50 mm diameter opening, and 6.35 mm mesh) alternating at 10-m intervals along a depth contour. All traps were baited using ~100-150 g Pacific mackerel and left on the mudflat overnight for a 24-hour deployment period that included a night-time high tide. The traps were retrieved at low tide.

Variables

• Index: Numeric value indicating data entry order
• Effort_Type: Purpose of trapping effort
• Date_Deployed: Date trap was placed in field
• Date_Retrieved: Date trap was retrieved from field
• Weather: Weather on trap retrieval day
• Personnel: Initials of individuals on trap retrieval team
• Management_Area: Management area, according to WDFW conventions, in which site was located
• Waterbody: Water body in which captures took place (Willapa Bay)
• Site_ID: Letter code for subsites. BR: Breakwater, BRM: Breakwater Marsh, DUK: Duckpole, OYV: Oysterville, PO: Port of Peninsula, POM: Port of Peninsula Marsh, STC: Stackpole, STS: Stackpole South; WLO: Woody's Lower elevation, WOU: Woody's Upper elevation
• Site_Name: Name of trapping site
• Site_Info: Classification of site based on elevation: Marsh: deep edge of pedestal marsh, approximately +7-8' relative to MLLW, Upper: higher elevation side of local clam bed referenced for trapping, Lower: lower elevation side of local clam bed referenced for trapping 
• County: Washington state county in which site was located
• Trap_Effort: Total number of traps set for effort
• Trap_Type: Type of individual trap set
• Trap_Number: Unique identifier of individual trap
• Trap.Elev.mllw: Elevation in meters relative to mean lower low water of trap
• Site.Elev.mllw: Average elevation of site, in meters relative to mean lower low water. Average of elevation for all traps deployed at the site.
• Trap_Info: Additional information on site parameters. Clam: on or adjacent to actively managed commercial clam bed, Marsh: deep edge of pedestal marsh
• Bait: type of baitfish used
• Latitude: WGS84 geoposition in decimal degrees of the experimental site in north latitude
• Longitude: WGS84 geoposition in decimal degrees of the experimental site in longitude, where negative sign denotes west longitude
• North.Cat: Categorical classification of site position relative to the estuarine gradient within Willapa Bay. This denotes whether the site is North or South of the "fattening line" described in the text. 
• Northing: Northing geoposition of reference sample in UTM 10T in meters
• Date_Checked: Date of trap check and data recording. If traps are removed from the field on the same date, this will be identical to Date-Retrieved
• CAMA_Total: Total number of European green crab (Carcinus maenas) found inside trap
• CAMA_Male: Total number of male European green crab (Carcinus maenas) found inside trap
• CAMA_Female: Total number of female European green crab (Carcinus maenas) found inside trap
• HEOR: Total number of hairy shore crab (Hemigrapsus oregonensis) found inside trap
• MEMA: Total number of Dungeness crab (Metacarcinus magister) found inside trap
• LEAR: Total number of staghorn sculpin (Leptocottus armatus) found inside trap
• PAGR: Total number of grainy-handed hermit crab (Pagurus granosimanus) found inside trap
• ILOB: Total number of Eastern dogwhelks (Ilyanassa obsoleta) found inside trap
• BAAT: Total number of Asian mud snail (Batillaria attramentaria) found inside trap
• URCI: Total number of Atlantic oyster drill (Urosalpinx cinerea) found inside trap
• NASS: Total number of Nassa snails (Nassarius spp., including N. mendicus and N fraterculus) found inside trap
• Mortalities: Total number of species of any organismal mortalities observed in trap.
• Notes: Relevant field notes

File: CrabSize.csv

Description: Dataset collected from a synoptic trapping effort conducted at the eight sites where clam recruitment and predator exclusion (small seeded plots) took place. Each row in this table records the biometric parameters and capture information for a single crab. During this survey, predators were trapped with an overnight soak of baited traps from 2-3 August 2024. At each site, 10 traps were set during low tide, specifically five square Fukui traps (13 mm mesh) and five minnow traps (Gee-40, 50 mm diameter opening, and 6.35 mm mesh) alternating at 10-m intervals along a depth contour. All traps were baited using ~100-150 g Pacific mackerel and left on the mudflat overnight, for a 24-hour deployment period that included a night-time high tide. The traps were retrieved at low tide. For crabs other than EGC, size was measured as total carapace width at the widest point and sex determined on-site. Trap contents other than EGC were then released. Captured European green crabs were measured, sexed, and counted off-site, and they were subsequently euthanized.

Variables

• Date_Observed: Capture date of crab
• Waterbody: Water body in which captures took place (Willapa Bay)
• Site_ID: Letter code for subsites. BR: Breakwater, BRM: Breakwater Marsh, DUK: Duckpole, OYV: Oysterville, PO: Port of Peninsula, POM: Port of Peninsula Marsh, STC: Stackpole, STS: Stackpole South; WLO: Woody's Lower elevation, WOU: Woody's Upper elevation
• Site_Name: Name of trapping site
• Site_Info: Classification of site based on elevation: Marsh: deep edge of pedestal marsh, approximately +7-8' relative to MLLW, Upper: higher elevation side of local clam bed referenced for trapping, Lower: lower elevation side of local clam bed referenced for trapping 
• Trap_Info: Additional information on site parameters. Clam: on or adjacent to actively managed commercial clam bed, Marsh: deep edge of pedestal marsh
• Latitude: WGS84 geoposition in decimal degrees of the experimental site in north latitude
• Longitude: WGS84 geoposition in decimal degrees of the experimental site in longitude, where negative sign denotes west longitude
• Trap_Number: Unique identifier of individual trap
• Trap.Elev.mllw: Elevation in meters relative to mean lower low water of trap
• Site.Elev.mllw: Average elevation of site, in meters relative to mean lower low water. Average of elevation for all traps deployed at the site.
• North.Cat: Categorical classification of site position relative to the estuarine gradient within Willapa Bay. This denotes whether the site is North or South of the "fattening line" described in the text. 
• Northing: Northing geoposition of reference sample in UTM 10T in meters
• Trap_Type: Type of individual trap set
• Species: Species code used for crab captured. CAMA: Carcinus maenas, MEMA: Metacarcinus magister, HEOR: Hemigrapsus oregonensis.
• Sex: Sex of crab Male or Female
• CW_mm: Size of crab measured as width of carapace at widest point (including spines) to nearest millimeter
• Notes: Relevant 

File: ManilaNet.csv

Description: This dataset lists the Manila clams (Ruditapes philippinarum) collected from four intertidal sites in Willapa Bay, Washington, USA, in 1 ft² (0.0929 m²) sediment samples collected to a depth of 10 cm and sieved to 5 mm. All Manila clams in each sample were measured for shell length (nearest mm). Samples were collected at three time points: November 2023, April 2024, and November-December 2024. At the second and third time points, sampling was done both underneath and outside of large clam nets deployed in a manner used by commercial clam growers. Large nets were installed by anchoring with rebar and digging the edges into the sediment. One net (14 x 5 m) per site with 6.35 mm mesh was installed in November 2023, and another with 12.7 mm mesh in April 2024; this larger-mesh net varied in size depending on grower preference: 12 x 6 m at Stackpole and MillChannel sites, 6 x 6 m at Oysterville, and two 6 x 6 m nets at Woodys. Reference samples were collected in a grid across the entire clam bed at each site (Stackpole: 9,608 m², Oysterville: 9,931 m², MillChannel: 20,112 m², Woodys: 30,000 m²). Each grid was divided into four quadrants, which we considered replicates of the treatment without nets, within which were 8-11 subsamples (on average, 9)

Variables

• DateCode: Year and season of sample collection
• Site: Code denoting each of four sites
• NetType: Mesh size of net, specifically "NetLg" and "NetLgA" for 12.7-mm mesh size and "NetSm" for 6.35-mm mesh size
• Trt: Experimental treatment, specifically "open" for reference samples outside of net, and "exclosure" underneath net
• Sample: Code denoting sample
• Rep: Code denoting quadrant of reference samples, or, for samples from underneath nets, which net the sample came from
• Size.cm: Maximum shell length (cm)
• Date: Date of collection within two weeks
• NGPS: WGS84 geoposition of the experimental site in north latitude
• WGPS: WGS84 geoposition of the experimental site, where negative sign denotes west longitude
• Northing: Northing geoposition of reference sample in UTM 10T, no data for samples underneath nets
• Easting: Easting geoposition of reference sample in UTM 10T, no data for samples underneath nets

Access information

Other publicly accessible locations of the data:

• Monitoring data from WSG Crab Team is publicly viewable via a set of Tableau dashboards: https://public.tableau.com/app/profile/matt.chadsey/viz/CrabTeamV2_5/Summary_Program?publish=yes