Long-term datasets can reveal otherwise undetectable ecological trends, illuminating the historical context of contemporary ecosystem states. We used two decades (1997–2019) of scientific trawling data from a subtidal, benthic site in Puget Sound, Washington, USA to test for gradual trends and sudden shifts in total sea star abundance across 11 species. We specifically assessed whether this community responded to the sea star wasting disease (SSWD) epizootic, which began in 2013. We sampled at depths of 10, 25, 50 and 70 m near Port Madison, WA, and obtained long-term water temperature data. To account for species-level differences in SSWD susceptibility, we divided our sea star abundance data into two categories, depending on the extent to which the species is susceptible to SSWD, then conducted parallel analyses for high-susceptibility and moderate-susceptibility species. The abundance of high-susceptibility sea stars declined in 2014 across depths. In contrast, the abundance of moderate-susceptibility species trended downward throughout the years at the deepest depths – 50 and 70 m – and suddenly declined in 2006 across depths. Water temperature was positively correlated with the abundance of moderate-susceptibility species, and uncorrelated with high-susceptibility sea star abundance. The reported emergence of SSWD in Washington State in the summer of 2014 provides a plausible explanation for the subsequent decline in abundance of high-susceptibility species. However, no long-term stressors or mortality events affecting sea stars were reported in Washington State prior to these years, leaving the declines we observed in moderate-susceptibility species preceding the 2013–2015 SSWD epizootic unexplained. These results suggest that the subtidal sea star community in Port Madison is dynamic, and emphasizes the value of long-term datasets for evaluating patterns of change.

In each year from 1997 to 2019 (except for 1998), we chartered a vessel equipped with a Southern California Coastal Waters Research Program (SCCWRP) otter trawl net for an annual research cruise near Port Madison, a bay on the west side of Puget Sound, WA. The vessel, which ran each year for two days in mid-May, towed the SCCWRP net along the bottom in set trawling locations corresponding to four depths: 10, 25, 50 and 70 m. Each year, five trawls took place at each depth, corresponding to discrete time periods: early morning (~6:00–8:00), morning (~10:00–12:00), afternoon (~15:00–17:00), evening (~20:00–22:00), and night (~1:00–3:00). Each trawl sampled benthic habitat for ~5 min over 370 m. Following each trawl, all sea stars caught were identified to species, counted, recorded, and released. This data was ultimately used to test for gradual trends and sudden shifts in total sea star abundance during the study period (1997–2019). We also obtained data on water temperature collected from 1999–2017 by the Washington State Department of Ecology at a site ~9 km southeast of our trawling sites (47.66001°, –122.4417°) to assess the effect of temperature on sea star catch over time. See below for a description of each data file pertaining to the analyses conducted by Casendino et al. (2023). 

List of data files included: 

1. invertebrates_dataset.csv
2. invertebrates_dataset_1997.csv
3. trawling_dataset.csv
4. trawling_dataset_1999.csv
5. WADeptEcology_CTD.csv

invertebrates_dataset.csv – documents invertebrates caught in sampling bottom trawls in Puget Sound, WA, from 1999 to 2019. Includes trawl information such as year, date, time, and depth. Categorizes invertebrates by informal group (e.g., crab, sea star, or shrimp), common name (e.g., vermillion star, sand star, or spiny red star), genus species (e.g., Pycnopodia helianthoides) and the number caught during a particular trawl.

invertebrates_dataset_1997.csv – documents invertebrates caught in sampling bottom trawls in Puget Sound, WA, in 1997. The row labelled “TRAWL” includes labels to indicate trawl time, where numbers 1, 2, 3, 4, and 5 correspond to afternoon, evening, night, early morning, and morning trawls. Depth is also listed. Sea stars collected during trawls are listed under the “echinoderms” heading by scientific name, and corresponding columns show how many individuals were caught during particular trawls.

trawling_dataset.csv – includes trawling information from 2000 to 2019. The column labelled “Station Name” includes basic information such as the type of trawl employed and depth sampled, and “Date” includes the day, month and year of each trawl. The exact time and depth of the start and end of each trawl tow are also listed, as well as the Mean Lower Low Water depth. Coordinates of the start and end of trawl tows are listed in degrees decimal minutes form, as well as the distance, speed and direction of each trawl.

trawling_dataset_1999.csv – reports trawling data from 1989 to 2000, including the same information presented in Dataset_trawlmaster.csv. From 1995 onwards, spatial coordinates are listed in degrees decimal minutes form.

WADeptEcology_CTD.csv – reports environmental data (including temperature data) collected by the Washington State Department of Ecology from 1999 to 2017 at a site in Puget Sound ~9 km southeast of our trawling sites.