Its whirling disease that causes that corkscrew effect to the fish. Below is a long description about the disease from a NH Biologist John Viar on FISHLAKEWINNI:
Hello Salty and Tim-
Thank you for your questions regarding the "cripple" laker/whirling disease concerns. I have since seen some of the thread/posts on fishlakewinni.
It should be made clear, although documented in the 1980's from the Merrimack River/southern NH (as one poster correctly noted), the probability of its widespread existence/detrimental effects in NH water bodies is very low at best. It has been detected in New York, it has also been detected in Vermont, notably in the Battenkill. However, as of 2005 per my source, it has not been detected in Maine which overall, is most similar to NH in terms of water quality/type of water bodies e.g. glacial lakes.
Many factors must "come together" for this affliction to take hold, including the existence and abundance, and habitat for, the intermediate host (Tubifex worms). Also, lake trout are not highly susceptible to the disease, whereas rainbow trout are highly susceptible. In our recent (at least my time, ~last decade) electroshocking studies conducted in streams/rivers (including lake tributaries) statewide, in which countless juvenile salmonids are examined during biological surveys, including rainbow, brook, and brown trout, and salmon, to the best of my knowledge there has been no indication of the presence of whirling disease. (Yes, in particular NH waters juvenile wild rainbows, browns, and salmon are not only present but actually fairly common, contrary to popular belief/common knowledge. Wild brook trout, native to NH, are obviously present.) In terms of fall netting, we have literally examined thousands and thousands of adult salmonids, and again, have not observed symptoms that suggest whirling disease is present in NH's large lakes (although external symptoms are not always seen in adult fish/they simply aren't there to see as adults; see below).
Given the posts I'm sure many have done extensive Google/internet searches; nonetheless check this link for information on whirling disease:
http://www.whirling-disease.org/ Most fish infected with whirling disease rarely achieve such size (although it is possible) as the lake trout pictured, since they typically spin and lose control of normal swimming activities (hence the name of the affliction) as juveniles - thus easily preyed upon by other predators, or severely limited in their own foraging efforts. (And we all know a small spinning fish in the jungle we call Winnipesaukee is on borrowed time). Given the current state of knowledge regarding this disease, more likely causes for such deformities in central and northern New Hampshire waters include genetics, "popped" vertebrae/disks, wounds incurred earlier in the fish's life - such as suffered from predator attacks, nutritional/foraging deficiencies, previous fungal or bacterial infections, and exposure to chemical contaminants, among other possibilities. Again, it is not impossible it could be whirling disease, but very, very, unlikely given the current knowledge and lack of observation/verification in the myriad of other waters and salmonids surveyed throughout NH on an annual basis.
One thing that should be noted; do NOT keep under-length fish. The laker we saw turned into the Winni Derby this spring is a perfect example that seemingly "cripple" fish may fare much better than we realize (deformed or not, I'll take an 11 lbs. laker any day!). However, if the fish is of legal length, you are certainly allowed to harvest the fish if desired.
Thank you again for your questions and what a great season. Can't wait until next year. Stay tuned for fall netting results; I'll be sure to send the "fall netting summary" and updated "fin clip/age list" to the website sometime this winter.
Also, feel free to post this response on the website, since it appears there was quite a thread on this topic.
John V.
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John A. Viar
Fisheries Biologist I
New Hampshire Fish and Game Department
Region 2 Office
PO Box 417
New Hampton NH 03256
(603)744-5470
