Hokkaido University
Graduate school of environmental science
I'm a phD student at Hokkaido University, mainly working for host-parasite associations of parasitic copepod Salmincola spp. and their hosts freshwater salmonid systems. Here is my WEB site: https://ryotahase344922.wixsite.com/website

Presenter of 1 Presentation

04. Parasites of fish

POSITIVE FEEDBACK OF PARASITE INFECTION AND REDUCED HOST CONDITION: A TEST BY MARK-RECAPTURE OF STREAM SALMONID AND PARASITIC COPEPOD (ID 113)

Session Type
04. Parasites of fish
Date
08/24/2022
Session Time
15:00 - 16:30
Room
Hall B4.M7+8
Lecture Time
15:20 - 15:30
Onsite or Pre-Recorded
Onsite

Abstract

Introduction

Understanding the impacts of parasite infection on host species in the wild is important for the proper managements of host’s conservation. A negative correlation between parasite infection and host body condition is generally assumed to be the causal effects of parasites. However, this could also be the consequence of host condition; poor conditioned individuals may be more susceptible to parasite infection. Moreover, infected hosts with poor body condition may suffer further infection. This positive feedback is likely to occur but has rarely been demonstrated in natural populations.

Methods

Here we conducted a mark-recapture survey on a stream salmonid-ectoparasite system: white-spotted charr Salvelinus leucomaenis vs. Salmincola sp., a parasitic copepod infecting the mouth cavity of the host in Hokkaido, Japan. Field surveys were carried out at three seasons (June, July, October) and body condition (residuals from body weight-length relationships), growth rate (mm/day) and parasite number were recorded. We conducted generalized linear mixed models (GLMMs) and structural equation modeling (SEM) to infer the causality among these variables.

Results

We found fish with poor condition were susceptible to further infections and copepod infections significantly reduced host body condition. These results suggest that parasite infection can be both cause and consequence of reduced host condition, and positive feedback is also possible.

Conclusions

This is the first study that demonstrated both causes and consequences of parasite infections and host condition through direct observations in the wild. Positive feedback creates heavily infected host, which could be the main infection sources and thus it can be the key for understanding the infection dynamics.

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