What I usually do is go through the lake and harpoon kill any that are 1.4x or less. Then I set traps and punch one of them, it'll grab the aggro from the others. Now you have 5 angry fish coming at you and your line of baskets.

The moment one of them is within range, just grab them in the basket line.

Wearing flak or riot gear is suggested but not necessary since 80% of the lake fish are dead and the remaining 20% won't deal too much damage