My 'problems' with your entry are few and far in-between, and I would argue against myself that these problems are hardly notable, but I would like to bring them to your attention anyways. There are two instances in which the fish's thoughts are rather awkward:
[I am born.]
[On this day, I wake up.]
In both of these cases, the fish is taking part in actions that it cannot control nor can it feel. When I wake up, I do not think 'I wake up'. Instead, I think about my surroundings, which the fish does do. That said, I think you could either put the thoughts into the narrative, or you could omit the thoughts altogether. By omitting, you would further entice the reader to try and understand the fish's circumstances.
For instance:
[I am born.]
[Yet where are my parents?]
Could simply be:
[Where are my parents?]
By cutting out the 'I am born', you can immediately open the situation to a wider variety of circumstances. While that effect does not last long, your work is very short and grabbing the attention and keeping the reader guessing becomes that much more important. Like I said though, this is a minor issue. I believe your work is next to spotless in terms of grammar; you can refer to Xenon's document for what little you did miss.
Nitpicking aside, I loved your entry. There's just no way around it. First off, I have to commend you on staggering your narrative and the fish's thoughts. The flow is sublime. It's just so easy to read, I can't help but go from sentence to sentence. There is a fine line between creating quick and dirty sentences and having the reader simply read fast because the sentences are simple, and creating meaningful sentences that both grab the attention of the reader while seamlessly flowing into each other. This work treads that line very, very well. Even if you are unaware, or even if I am a bit off base, but I believe that the work put into carefully weaving small sentences like these together are underrated. I'm here to tell you I appreciate it!
Moving on, I thought the whole premise was both well thought out, and well executed. It takes a bit to realize that our protagonist is actually a fish, but I think that makes it all the more interesting. And even once I figured it out, the 'flavor' of the story doesn't really die out. I mean, this fish is just so existential! It's great ahaha.
While the salmon's tale ends with his death, the story for the reader does not end there. I take the salmon to be symbolic of humans. The moral of the story does not present one directly, but instead it challenges the reader to develop and take a stance on traditions. It challenges the reader to weigh the risks of both continuing tradition and branching off. This fish is possibly the most thought-provoking fish I have ever encountered.
Needless to say, I enjoyed your entry. The debate between you and El Chacal's work was extremely heated. Make no mistake, your work deserves every bit of that 2nd place and some. I hope you continue to enter contests. Also, feel free to submit any other stories that you have written or any that you plan to write.