This would not be said in the part of the US I’m in. ‘In the streams’ conveys no useful information. Things you could hear: I go freshwater fishing. I freshwater fish. I fly-fish. I’m an angler. I fish on the Elwha. (the name of the river) I fish in the Cascade mountains. (the name of a mountain range) I fish in the streams and rivers of the Cascade mountains. (the name of a mountain range) We’re more likely to contrast fishing on rivers with fishing on lakes. ‘Streams’ would fall in the river ‘category’.

Yes, you can say 'I go fishing in the streams' in the present tense. You can also say 'I went fishing in the streams' when the action is in the past.

I went to the stream to go fishing🐠

"I went stream fishing"

I believe the correct form of the sentence is "I go fishing in the stream." The singular form "stream" is used when referring to one body of water, while the plural form "streams" is used when referring to more than one body of water. The word "in" is used to show location. For example, you might say "I am standing in the stream." This shows that you are located in the stream. I hope that helps! Do you have any other questions about grammar or sentence structure?