Avoidance of fisheries-induced evolution: management implications for catch selectivity and limit reference points

Area of Science:

• Ecology
• Evolutionary Biology
• Fisheries Science

Background:

• Life-history traits like maturation timing are subject to evolutionary pressures.
• Fishing mortality (F) and gear-specific capture probabilities can influence selection on these traits.
• Northern Atlantic cod (Gadus morhua) exhibit variation in maturation timing (4 vs. 7 years).

Purpose of the Study:

• To investigate how fishing mortality and gear selectivity affect the fitness of early- and late-maturing Atlantic cod genotypes.
• To determine the fishing mortality threshold (F evol) that favors early maturity.
• To assess if traditional fisheries management objectives can minimize fisheries-induced evolution.

Main Methods:

• Estimated fitness (r) for early- and late-maturing cod using life-history data.
• Incorporated catch selectivity data for four fishing gear types (trap, gillnet, handline, otter trawl).
• Calculated fitness functions to identify the fishing mortality threshold for selection favoring early maturity.

Main Results:

• Over-exploitation led to fishing mortalities exceeding those required for evolutionary change.
• Dome-shaped selectivity of fixed gears (e.g., handlines) reduced selection for early maturity.
• Knife-edged selectivity of bottom trawls enhanced selection for early maturity.
• An evolutionarily-sensitive threshold (F evol) was identified, comparable to overfishing reference points.

Conclusions:

• Fisheries-induced evolution can be minimized by adhering to traditional management objectives and harvest control rules.
• Using evolutionarily-sensitive limit reference points, aligned with F msy and F 0.1, can effectively reduce fisheries-induced evolution.
• Sustainable fishing practices are crucial for minimizing genetic changes in commercially exploited fish populations.