Marine mammal recovery is associated with the resurgence of a nematode parasite

Data files

Sep 12, 2025 version files 154.70 KB

Abstract

As the oceans change, the abundance of parasites and risk of infection to marine mammals may also be changing. Nematodes in the family Anisakidae can harm marine mammals and recent studies have revealed a global increase in these parasites, but the cause is unknown. We sought to determine how anisakid risk in Puget Sound had changed over 98 years by conducting parasitological analysis of museum specimens of the prey species of marine mammals. We dissected Pacific Herring, Walleye Pollock, Surf Smelt, Pacific Hake, and Copper Rockfish collected between 1920 and 2018. We found that the larval anisakid Contracaecum spp. was the most abundant marine mammal parasite in these prey fish. We used a state-space model to assess the relationship between Contracaecum spp. abundance and time, with harbor seal abundance and sea surface temperature as potential correlates. We detected an overall decline in Contracaecum spp. abundance with a recent uptick starting in 1989, which was correlated with increasing harbor seal abundance. While these data reveal a regional trend, increases in marine mammal parasites in response to marine mammal protection have occurred elsewhere, and suggest that the phenomenon might be more widespread than is currently appreciated. Marine mammals in Puget Sound are probably less burdened by anisakids than they were historically, but the recent recovery of anisakids could impact the health of these hosts, which today face very different stressors than they did in the past.

Dataset includes anisakid (Contracaecum and Anisakis spp.) data collected from natural history specimens of five species of fish hosts collected from 1880-2018 in Puget Sound, Washington. These files include Pacific hake (hake_2022.02.21.csv), Pacific herring (herring_2022.02.23.csv), walleye pollock (pollock_2022.02.21.csv), copper rockfish (rockfish_2022.02.21.csv), and surf smelt (smelt_2022.02.21.csv). There is also harbor seal abundance data from Chasco et al. 2017, pollutant data from Brandenberger et al. 2008, and temperature data from Race Rocks lighthouse (48.2980°N, 123.5315°W) British Columbia Lightstation Sea-Surface Temperature and Salinity Data.

Description of the Data and file structure

Each fish species' anisakid count and metadata are all housed in independent .csv files (smelt_2022.02.21.csv, rockfish_2022.02.21.csv, pollock_2022.02.21.csv, herring_2022.02.23.csv, hake_2022.02.21.csv). For analysis, the fish data (hake, herring, pollock, rockfish, and smelt) have been compiled into one dataset in the compiled_data.RDS file. The other data (temperature, pollutants, and harbor seal abundance estimates) are derived from the publications listed below.

hake_2022.02.21.csv , herring_2022.02.23.csv , pollock_2022.02.21.csv , rockfish_2022.02.21.csv , smelt_2022.02.21.csv

Year.Collected: the year the fish was collected from the wild and preserved in the Burke Museum's Ichthyology collection

Columns named in the format XX_XX_XX: the count of each genus of parasites found in each fish, the suffix indicating the initials of the scientific name of that species in some cases, or "all" in others, where it was found in more than one species. For example, Anisakis_sp_all indicates Anisakis sp. nematodes found throughout the body of the particular host.

latjitt site: the collection site latitude, but the coordinate has been "jittered" by +/- a small amount to reduce overlap in mapping and analysis.

Fish.ID: the catalog number of each fish dissected

Standard.Length..mm.: standard length of the fish in mm

Total.Length..mm.: total length of the fish in mm

long: longitude the fish was collected

lat: latitude the fish was collected

fish_density: an estimate of the density of the fish in Puget Sound from that year

X: year since 1920

temp_na_rm: average temperature, calculated with NAs removed. Data compiled from Race Rocks Temperature data, temperature with NAs removed

sTemp: temperature standardized to a value between 0-1.

Pb: average lead reading for that year in μg/g

As: average arsenic reading for that year in μg/g

Zn: average zinc reading for that year in μg/g

Ni: average nickel reading for that year in μg/g

V: average vanadium reading for that year in μg/g

Cr: average chromium reading for that year in μg/g

Cu: average copper reading for that year in μg/g

Ba: average barium reading for that year in μg/g

Be: average beryllium reading for that year in μg/g

Sig8_lignin: average lignin reading for that year in mg/g

Lamb8: average soil biomarker concentration reading for that year

Bd.V_soil_biomarker: average soil biomarker concentration reading for that year

compiled_data.RDS

In this compiled dataset, each row is a parasite species in an individual fish. The columns represent different variables:

site: the latitude and longitude the fish was collected

year: the year the fish was collected

fish.id: the institution and catalog number of the fish

length: the standardized length of the fish

long: longitude collected

lat: latitude collected

fish species: general common name of the fish

para.spc: the species of parasite collected from the fish

count: the number of parasites collected of that species from the fish

sfish_density: when available, the standardized population density of that fish species in that year

temp_na_rm: the water temperature from that year, with NAs removed, from Race Rocks

bd.v_soil_biomarker: average soil biomarker concentration reading for that year

par.type: general type of parasite

lifecycle: type of parasite life cycle, direct (single host) or complex (multihost)

nhosts: number of hosts needed to complete the parasite's life cycle

terminal: whether the species was a terminal host or not, 0 = no, 1 = yes, 2 = "unknown"

ord2raw: PC2 from the PCA compiling pollutant information

ord1raw: PC1 from the PCA compiling pollutant information

ord2: LOESS prediction of PC2

ord1: LOESS prediction of PC1

temp_smooth: the simple moving average (sma) of the temperature for that year

Sharing/access Information

Links to other publicly accessible locations of the data: https://github.com/wood-lab/Mastick_et_al_Ecology

Data derived from the sources below:
Wood CL, Welicky RL, Preisser WC, et al. 2023 A reconstruction of parasite burden reveals one century of climate-associated parasite decline. Proc Nat Acad Sci 120: e2211903120.

Brandenberger JM, Crecelius EA, Louchouarn P. 2008 Historical inputs and natural recovery rates for heavy metals and organic biomarkers in Puget Sound during the 20th century. Environ Sci Technol 42: 6786–90.

Chasco B, Kaplan IC, Thomas A et al. 2017 Estimates of Chinook salmon consumption in Washington State inland waters by four marine mammal predators from 1970 to 2015. Can J Fish Aquat Sci 74: 1173–94.

British Columbia Lightstation Sea-Surface Temperature and Salinity Data (Pacific), 1914-present. https://open.canada.ca/data/en/dataset/719955f2-bf8e-44f7-bc26-6bd623e82884.

Strom A, Francis RC, Mantua NJ, Miles EL, Peterson DL. 2004 North Pacific climate recorded in growth rings of geoduck clams: a new tool for paleoenvironmental reconstruction. Geophysical Research Letters, 31(6).