Bycatch Rate Calculator

This calculator converts raw catch weights from a fishing trip or observed set into the standard rate metrics fisheries managers and observer programs actually track. Total catch is simply target catch plus bycatch, and from there the bycatch ratio (bycatch ÷ total catch) and discard rate (discarded weight ÷ total catch) are both expressed as percentages of that combined total — note the discard rate is calculated against total catch, not against bycatch alone, so it reflects overall waste relative to everything brought up, not just the non-target fraction. Bycatch per unit effort (BPUE) divides total bycatch weight by fishing effort in hours, giving a rate that can be compared across trips of different lengths; the same bycatch weight is also divided by the number of sets or hauls to get a per-set figure, and target catch per hour (CPUE) is calculated the same way for comparison.

The fleet-wide estimate extrapolates by multiplying your BPUE by the fleet's total reported effort hours, which assumes your sampled trip's bycatch rate is representative of the whole fleet — a reasonable rough projection but one that can be badly skewed by gear type, season, or location differences if your sample isn't typical. Gear selectivity is reported as target catch's share of total catch: a higher percentage means the gear is doing a better job of catching only what's intended. Retained bycatch (bycatch minus discards) shows how much of the non-target catch is actually being utilized rather than thrown back.