Fish deaths in Chile about half last year, 3.5kt is not much compared with their annual output of 122kt (in 2020), but it might become noticeable as their weight was about 1.6kg (at the blumar site at least), so they would have grown to 3x that, about 10kt.
But maybe they didnt expect them all to grow to maturity, and have more small ones than they need to get to their quota, i have no idea.