Rainbow trout (Salmo gairdneri) stocking and Contracaecum spp

Area of Science:

• Ichthyology
• Parasitology
• Ecology

Background:

• Rainbow trout stocking in High Rock Lake was unsuccessful due to high levels of Contracaecum spp. larvae.
• Nematode larvae in fish tissues rendered them unmarketable, impacting the stocking program's viability.

Purpose of the Study:

• To investigate the ecological factors contributing to Contracaecum spp. larval infections in introduced rainbow trout.
• To understand the parasite's life cycle and transmission dynamics within the High Rock Lake ecosystem.

Main Methods:

• Experimental infections were conducted on rainbow trout and pelicans (Pelecanus erythrorhynchos).
• Observations were made on fish-eating bird behavior and the prevalence of Contracaecum spp. larvae in minnow species.
• Ecological data on fish densities and bird populations were analyzed in relation to parasite loads.

Main Results:

• Introduction of rainbow trout attracted significant numbers of fish-eating birds, especially pelicans.
• Rainbow trout predation on minnows concentrated parasites, increasing infection rates in both introduced and native fish.
• Parasite levels in minnows decreased when rainbow trout stocking ceased and bird populations returned to normal.

Conclusions:

• The ecosystem dynamics, including introduced fish, native prey, and bird populations, influenced parasite transmission.
• Management of fish stocking and bird presence is crucial for controlling parasite infections in aquatic ecosystems.
• Understanding host-parasite interactions is vital for successful fisheries management and disease prevention.