Multiple-batch spawning: a risk-spreading strategy disarmed by highly intensive size-selective fishing rate

Area of Science:

• Ecology
• Evolutionary Biology
• Fisheries Science

Background:

• Organisms employ diverse life-history strategies to adapt to environmental variability.
• Multiple-batch spawning is a risk-management strategy in long-lived fishes, distributing offspring survival risks.
• This strategy's fitness benefits increase with female body size, a trait targeted by size-selective fishing.

Purpose of the Study:

• To investigate how fishing intensity impacts the life-history traits and fitness of multiple-batch spawning fish.
• To determine if the risk-spreading advantage of multiple-batch spawning is compromised under human-induced (fisheries) selection.
• To assess the relationship between ecological population recovery and evolutionary recovery of population structure.

Main Methods:

• Utilized an eco-evolutionary mechanistic model, empirically and theoretically grounded.
• Parameterized the model specifically for Atlantic cod (Gadus morhua).
• Simulated the effects of varying fishing intensities on life-history traits and fitness.

Main Results:

• The risk-spreading strategy of multiple-batch spawning is ineffective against fisheries selection.
• Fisheries selection favors smaller fish, diminishing the risk-spreading effect.
• Ecological recovery in population size does not guarantee evolutionary recovery in population size structure.

Conclusions:

• The risk-spreading mechanism of batch spawning is vulnerable to fisheries-induced evolution.
• Recovery of the size structure in overfished stocks is crucial for full population recovery.
• Conservation strategies must consider evolutionary impacts alongside ecological recovery.