By Carmelo “Mel” Russo
Little is known about the existence of whitefish (subfamily Corigoninae) in Seneca and Cayuga Lakes. The 1970 edition of Hubbs and Lagler, key to northeastern freshwater fishes, lists a particular kind of whitefish as the “the Seneca Lake Cisco.” This would be a subspecies of the Great Lakes cisco. The 2004 edition cites several more possible subspecies of ciscoes as being present in Canandaigua, Skaneateles, and some of the other Finger Lakes. Although not documented, the species was reported as “present” in 1909 by Cornell vertebrate biologists Reed and Wright, but the duo had collected no specimens of the fish in the Cayuga Lake basin. They did state that “Any specimens of whitefish in Cayuga Lake were certain to be ciscoes.”
The cisco (Coregonus artedi) is a whitefish whose lower mandible protrudes beyond the snout.
Also, the bodies of ciscoes are more laterally compressed and there are differences in the number of gill rakers within the species. (Gill rakers are coarse hairlike structures that are filled with many capillaries. These can be observed under the operculum [gill cover.] They are equivalent to the alveoli of lungs that facilitate gas exchange for internal respiration.) It is the rakers that caused taxonomists (classifiers) to believe that the cisco is one of the most differentiated species of fish in existence. In 1970, there were over 55 subspecies of ciscoes (C.artedi) listed by Hubbs and Lagler: one for almost every small, deep lake throughout the Great Lakes region.
It is theorized that during the last global warming approximately 10,000 years ago, the vast extensions of the Great Lakes resulting from the melting ice caps reached far into the northern states including Wisconsin, Michigan, Ohio, and New York. During this period, as organisms do, the original Great Lakes cisco population extended itself to fill the newly available living space throughout the expanse of high water. When the ice caps began reconstituting about 8000 years ago, the ciscoes became trapped in the deep holes into which they had settled during the receding high water. Among the “deep holes” were the Finger Lakes. Eventually they could not interbreed with the main originally contiguous population of the Great Lakes ciscoes because of the land and the intolerable shallow water barriers that separated them. Scores of separate habitats were created by the retreating post glacial waters of Lake Iroquois (over-sized Lake Ontario), Lake Wayne, Lake Lundy (over-sized Lake Erie) and others.
Each of these “deep holes” has existed separately from the Great Lakes for about 8000 years. Since ciscoes are cold water fish, the numerous individual populations were isolated for all of this time from the original. Thus, random differences in gene make up were perpetuated within each group. There became the subspecies known as the Seneca Lake Cisco, the Cayuga Lake Cisco, the Skaneateles Lake Cisco, and the list continues. The untrained human eye can not tell the differences among these Coregonids. However subtle variations occur in the number of gill rakers, scales in the lateral line and the extremity of the snouts, among other things.
An analogy of this would be genetic equivalent of a southern Italian and a Norwegian as compared to a Seneca Lake Cisco and a Great Lakes Cisco. The two types have differences but the species could interbreed if the populations were contiguous and the resulting offspring would be fertile exhibiting characteristics of each group. Isolation caused the perpetuation of differences in each of both forms.
The cisco category of whitefish is a classic example of what biologists call evolution. This is NOT a religion. These ever-so-slight changes in populations of a single species are sometimes random. Often changes occur and are perpetuated in an isolated population for no reason. At other times the gene may be advantageous and be perpetuated in the population because of environmental differences. In the case of cisco, the continuation of the variations of the number of gill rakers gene may be a survival trait in individuals related to differences in available oxygen. The greater the number of gill rakers, the more surface for the absorption of oxygen. Thus, a once meaningless gene may have had significance when oxygen concentrations of the water became lower or higher in the various lakes.
Other genetic differences like the number of scales in the lateral line may have no advantage or disadvantage and may just continue because of inbreeding within an isolated population. There is no opportunity for hybridization or gene co-mingling because of geographic barriers. Other genetic barriers may be time, temperature, water quality, and reproductive cycles.
Unlike their close, tasty relative, the great lakes whitefish (C. clupieformes), ciscoes are savored only when smoked (not inhaled though). Few are caught in our lakes because of their weak, smaller jaws and lack of teeth. Natural reproduction of whitefish and all lake salmonids in the Finger Lakes may be nonexistent today because of increasing siltation of the rocky shoals upon which these species require to spawn. Any specimens of “whitefish” brought to my attention have proven to be sheepshead (freshwater drum, Aplodinotus grunniens) which are not related at all, to whitefish.
The entire whitefish group is now considered a subfamily of salmonidae (trouts and salmons) as all have a fleshy or adipose fin between the tail and dorsal fin, all are soft scaled, and all have similar internal structures. Scales of trouts and salmon are smaller, however. Recently, genetic scientists have lumped many of what were considered separate species and subspecies into one species because of DNA studies and newly found environmental effects on gene expression. It is a wonder to know that right here in the Finger Lakes area we have our own little bit of evolution that has recently gone on and may still be continuing. This is yet another interesting anomaly of the unique Finger Lakes area in which we live.
Sources: Hubbs and Lagler (1970, 2004)
Reed and Wright (1909)
Images (L to R):
https://commons.wikimedia.org/wiki/File:Coregonushoyi.jpg Deepwater Cisco (Coregonus hoyi)
http://www.gov.mb.ca/waterstewardship/fish/provincial_fish/fish_species.html Freshwater Drum (Aplodinotus grunniens)
© 2015 Mel Russo All Rights Reserved.