A man comes home and finds an eel that his wife has bought for dinner. Faced with it, he cries. The last line, "that was all I," is oddly broken off, and it leaves a few readings open. The simplest is that the eel was all he could manage to do or say, or all there was to the moment: a creature, a meal, and his tears. It could also mean that the cry was all he did, a helpless reaction rather than any action.
The title helps. A "starving artist" who "casts a wide net" suggests someone scraping together a living from whatever turns up, and the eel fits that picture of making do. The speaker may be crying out of pity for the animal, or out of worry about money, or some tangle of both. The poem doesn't say, and that's part of its pull.
The mood is small, strange, and quietly funny, with real sadness underneath. Its brevity makes the moment feel raw and unfinished, like a thought that stops mid-sentence.