In "The Incomplete Angler," by Herbert Tompkins, we can clearly identify a thesis statement within the opening paragraph. A thesis statement is the author's expression and summary of the key point they intend to make in their work, and in Tompkins's work here, although the thesis is not stated outright, it is certainly implied from the outset.
Tompkins describes how, as a child and at the advice of a Master Izaak Walton, he decided to take up angling. There is a strong association drawn between angling and quietness: the keen angler must be quiet if he seeks to achieve his goal. "Perseverance" is also very important. Tompkins is keen to express that, at first, although he was quiet and he did display this virtue of perseverance, he was not successful. However, after a short time, he caught his first fish, a "three ounce dace," and was so delighted by it that he has never been so pleased with any other fish he has caught since.
There are a couple of morals, then, to this story:
1. Perseverance will eventually pay dividends;
2. The first time we are rewarded for perseverance, it will feel incredible enough to warrant helping us continue in our quest (even if that first reward is rather small).
So, we could argue that the thesis statement is something like the following: perseverance is difficult at first, but it will eventually be rewarded, and even the smallest reward for true diligence and perseverance will feel like a great reward indeed.