Phrixocephalus cincinnatus
For hundreds of millions of years, parasites have existed on earth. These ancient but everadapting life forms have inhabited our world since life began. Despite the information we have obtained, and amount of effort and time put in to study parasites, there are many knowledge gaps that remain. In aquaculture for instance, more specifically salmon farming, we are attempting to close some of these gaps and discover more about the parasite, wild fish, and farmed fish relationships. Two things are certain however – parasites are found in both farmed and wild fish populations and they are a natural occurrence.
So what, exactly, is a parasite anyway? The definition is not complicated. A parasite is simply any organism that takes it’s nutrients directly from another organism in order to survive and has the potential to harm its host.
We tend to think of parasites as only animals, but plants can be parasites too. Mistletoe, which you might be familiar with, is an example of a plant parasite because it grows within or attached to a different tree or shrub.
Parasites have an important role to play in the ongoing development of life. “There’s a constant adaptation of the host and the parasite as they try to outdo each other,” explained Derek Nickel, Environmental Technician. It’s like two countries at war, he added. This struggle between the two is one of the many mechanisms that help move evolution forward.
Earlier this year it was reported that an increase in the numbers of a copepod from the family Pennellidae might be caused by fish farms. However, ground-breaking studies were done in BC waters in the late 1960s and early 1970s on this parasite (well in advance of large-scale salmon aquaculture) by respected scientists such as Dr. Bob Kabata and Dr. Earl Forrester.
They examined its population levels and distribution and concluded that population fluctuations and the shift of parasites from one location to another is expected due not only to the movement of the host but also to naturally occurring environmental conditions. Their research also included collecting much life cycle data, although a great deal remains unknown.
Fish infected with this specific species of Pennellidae can suffer blindness caused by the parasite infecting its eyes. This lack of sight leads to starvation when the fish are unable to find food.
There has been little to no compelling evidence to support the suggestion that any increase in these Pennellidae parasite populations are related to presence of salmon farms, commented Derek. This assertion in the summer 2010 is simply not supported in the scientific literature and no conclusions can currently be made about potential links to salmon farming operations.
