We compiled data from experimental studies on fisheries species that compared mortality of parasitized and unparasitized hosts at a static temperature. We defined fisheries species to include both invertebrate and vertebrate species that are harvested commercially or recreationally. In Fall 2019, we searched Web of Science following PRISMA protocols (O'Dea et al. 2021) using key terms that would return papers focused on harvested aquatic species, parasites, and diseases, but would exclude papers that were focused on human, environmental or domestic animal health (see Appendix S1 in Supporting Information). This search yielded 1,201 papers. We then screened the abstracts of these papers, and retained only papers that satisfied four criteria: 1) an experiment was performed that included at least one parasite exposure treatment paired with an unexposed control group, 2) temperatures were intended to be constant and not intentionally varied, 3) hosts were from species that constitute a fishery, including those in aquaculture, and 4) estimates of survival or mortality were reported for both infected and uninfected hosts at each temperature treatment. This selection process reduced the number of studies to 386 (Appendix S1 and Figure S1). We obtained full versions of 364 papers (22 papers from the original 386 were unobtainable). We then screened the full text of these papers to ensure a match to our four criteria, which reduced the 364 papers to 70. To increase statistical power to estimate the effect of host Order on parasite-induced mortality, we excluded experiments from hosts in Orders with fewer than three effect sizes. This reduced the number of papers included in our study from 70 to 60 and yielded a total of 301 effect sizes from 140 experiments (several papers included more than one experiment; Appendix S1 and S2, Figure S1). At least two people extracted data from each paper to reduce extraction error. If extracted values differed, the data were re-extracted until there was agreement between the two extractors. For data that were displayed in a graphical format only, we used WebPlotDigitizer (Rohatgi 2022) to extract data. Data (which may have been presented as mortality rates, or proportion surviving) were converted to numbers of host individuals that were dead and alive at the end of the experiment. We also extracted information about the paper itself, including the source of the hosts used in the paper and the motivation for conducting the experiment (see Appendix S1). Finally, we collected additional information about host and parasite traits from outside sources (e.g., other peer reviewed papers, government reports) when necessary to obtain moderator variables (Table 1, Appendix S1 and S2). The moderators (Table 1) were used to test a priori hypotheses regarding how host, parasite, and study design traits influenced how temperature affected parasite-induced mortality. Because our focus was on parasite-induced mortality, we used log odds ratios and the variance surrouding log odds ratio as our effect size to compare host survival in the parasitized vs unparasitized treatments.

Rapid warming could drastically alter host-parasite relationships, which is especially important for fisheries crucial to human nutrition and economic livelihoods; yet we lack a synthetic understanding of how warming influences parasite-induced mortality in these systems. We conducted a meta-analysis using 301 effect sizes from 60 empirical papers on harvested aquatic species and determined the relationship between parasite-induced host mortality and temperature and how this relationship was altered by host, parasite and study design traits. Overall, temperature increased parasite-induced host mortality; however, the magnitude and sometimes direction of this relationship varied. Hosts from the order Salmoniformes experienced a greater increase in parasite-induced mortality with temperature than average. Opportunistic parasites were correlated with a greater increase in host mortality with temperature than average, while bacterial parasite-induced mortality was lower than average as temperature increased. Thus, parasites will generally increase host mortality as the environment warms; however, this effect will vary among systems.

Funding provided by: National Science FoundationCrossref Funder Registry ID: https://ror.org/021nxhr62Award Number: DGE-1545433 Funding provided by: Georgia Sea GrantCrossref Funder Registry ID: https://ror.org/0014w1417Award Number: NA180AR417008 Funding provided by: University of GeorgiaCrossref Funder Registry ID: https://ror.org/00te3t702Award Number: Funding provided by: National Science FoundationCrossref Funder Registry ID: https://ror.org/021nxhr62Award Number: DEB-1655426