The Origin And Future Of The Salmoninae
The Origin And Future Of The Salmoninae
Introduction
It is unlikely that any family of fish has received as much attention as the Salmonidae. Many have a particularly heart-felt interest in the Salmoninae (trout, salmon, and char) because they love to fish. But man often destroys that which he loves, and the Salmoninae are no exception to this phenomenon. Exploitation of these fish has led to the extinction of certain species in some areas, but the attempt to preserve our valued fisheries has resulted in extensive research on the Salmoninae. This knowledge allows us to speculate on their origin and their prospects for the future.
Taxonomy
It is believed that the Salmoninae are descendants of the Isospondyli order of fishes. This group, the most primitive of bony fishes are also called the teleosts and looked somewhat like today's tarpons and lerrings. The earliest fossils of isospondylous fishes have been found in Cretaceous rocks which means these forms were in existence well over 65 million years ago. The sub-order Salmonoidei is separated from other isospondylous fishes due to many similarities in structure. We find the existence of a second adipose fin which is not found in other fish, and scaled bodies but scaleless heads. Also, the vertebrae of the tail are turned upwards. There are many other similarities such as similar jaws and oviducts. Of the six families of the sub-order Salmonoidei, the Salmonidae family distinguishes itself by having only one or two upturned tail vertebrae rather than three. Within the family Salmonidae, I am interested in the Salmoninae (trout, salmon, and char) rather than the Thymalinae (grayling) and Coregoninae (whitefishes).
Before continuing, I would like to mention that there is a lot of confused nomenclature in this sub-family. By common definition, salmon are anadramous. This means that they live and feed in the ocean and migrate up rivers to reproduce. Trout, on the other hand are said to be completely fresh water fish. Still, we find that some common names of fish go against this general rule. So we hear of anadramous trout, such as steelhead, and landlocked salmon.
In the sub-family Salmoninae, there are seven genera. Brachymystax is an Asian freshwater genus. Hucho is found in Eurasia. Salvelinus is circumpolar and is commonly called "char". Char have smaller scales than other Salmoninae and have...