Gammarids were additionally collected with a long hand net at several known stickleback breeding grounds.
The sampling places of the copepods and infected sticklebacks were about 80 km apart.
Survival is essential for transmission to the stickleback host, which only feeds on live copepods.
The parasite uses the stickleback as an intermediate host between copepods and the final host, piscivorous birds.
Other studies examining growth in experimentally infected sticklebacks have not provided standardized rations, making comparison with the present study difficult.
The sampling places of the copepods and infected sticklebacks were about 2 km apart and the two water bodies were connected.
This facilitates predation by the subsequent host, the three-spined stickleback.
One singly infected copepod was fed to each of 30 of the selected sticklebacks and the remaining fish (sham-exposed controls) were fed parasite-free copepods.
