Abstract
Distribution and abundance of common parasitic nematodes in marine fishes is not well documented in many geographic regions. Understanding the influence of large-scale environmental changes on infection rates of fish by nematodes requires quantitative assessments of parasite abundance for multiple host species. We collected samples of two species of cod and eight species of rockfish (total of 232 specimens) from waters near Kodiak Island, Alaska, USA during Spring and Summer of 2015, and dissected and recorded all internal nematode parasites. We quantified the prevalence and intensity of nematode parasites in the ten host species, and tested for differences in prevalence among host species. We found three species of nematode: Anisakis simplex, sensu lato (Van Thiel), Pseudoterranova decipiens, sensu lato (Krabbe), and Hysterothylacium sp. (Ward and Magath). Eighty-two percent of the examined fish were infected with at least one parasitic nematode. The overall prevalence of P. decipiens, A. simplex, and Hysterothylacium sp. was 56%, 62%, and 2%, respectively. Anisakis simplex and P. decipiens were abundant and present in all ten species of host fish examined, whereas Hysterothylacium sp. was rare and found in only five of the host fish species. Prevalence and mean intensity of P. decipiens and A. simplex varied across the ten host species, and the number of parasites varied substantially among individual hosts within host species. The mean intensity of P. terranova and A. simplex in our study was substantially higher than the mean intensity for these same species from multiple other locations in a recent meta-analysis. This study provides a baseline of nematode parasite abundance in long-lived fish in waters near Kodiak Island, AK, and fills an important gap in our quantitative understanding of patterns of occurrence and abundance of these common and widespread parasites of marine fish.
Highlights
Documenting environmental change, and consequent change in the distribution of organisms, has become increasingly important for understanding the ecological and evolutionary responses of organisms over time [1]
We found three species of parasitic nematodes (Figure 2) in 232 potential host fish, found three parasitic nematodes
Patterns of prevalence and intensity among the ten host species we studied are remarkably similar for the two common species of parasitic nematodes
Summary
Documenting environmental change, and consequent change in the distribution of organisms, has become increasingly important for understanding the ecological and evolutionary responses of organisms over time [1]. Several examples of change in distribution, abundance, and diversity of species have been observed because of good baseline data available from previous research [1,2,3]. Detecting such changes without baseline data is difficult, and quantifying the effects of change is impossible without previously collected quantitative data [4]. To understand the influence of large-scale environmental changes on infection rates of fish by nematodes, it is important to perform quantitative assessments of parasite abundance for multiple host species in many locations [1]
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