Fish's flavor doesn't survive as well as lean red meat. I've eaten 10 year old moose and venison and it tasted good.
I would thaw it out and smell it. It's not an oily fish (like salmon) so it may have survived OK.
There is an interesting quote in Alexander Solzhenitsyn's book Gulag Archipelago where apparently fish or salamander frozen in the last ice age was eaten. I found this link
. Interesting read:
These mammoths lived in Siberia together with many other species, which tend to get less publicity because their presence in “Ice Age” Siberia is even more controversial, as the mammoth is (wrongly) considered an “Arctic”, cold-climate animal. It is well known that mammoth-meat has been eaten on many occasions, and has been commended for its excellent flavour! What is less well known is that frozen salamanders and fish from northern Siberia have also been eaten. These salamanders must have lived during the last Ice Age, when the North Pole was in Canada. The eating of these antediluvian meats was mentioned by Aleksandr Solzhenitsyn in Gulag Archipelago, his monumental book on the Soviet gulags of Northern Siberia. He recalls an article he read in the scientific journal Nature, detailing an expedition led by Baron Von Toll. This expedition was manned by half-starved prisoners from the gulags, who were forced to join Von Toll’s gruelling Siberian expedition. There they discovered the remains of salamander and fish in subterranean frozen streams:
Whether fish or salamander, these were preserved in so fresh a state, the scientific correspondent reported, that those present immediately broke open the ice encasing the specimens and devoured them with relish on the spot.
The magazine no doubt astonished its small audience with the news of how successfully the flesh of fish could be kept fresh in a frozen state…
…We could picture the entire scene right down to the smallest details: how, flouting the higher claims of ichthyology and elbowing each other to be first, they tore off chunks of the prehistoric flesh and hauled them over to the bonfire to thaw them out and then bolt them down.
We understood because we ourselves were the same kind of people as those present at that event. We, too, were from that powerful tribe of zeks, unique on the face of the earth, the only people who could devour prehistoric salamander with relish.”