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Updated: May 8, 2026
12:24
Laboratory Estimation of Net Trophic Transfer Efficiencies of PCB Congeners to Lake Trout (Salvelinus namaycush) from Its Prey
Published on: August 29, 2014
Quantifying the balance between bycatch and predator or competitor release for nontarget species
Emilius A Aalto1, Marissa L Baskett
1Department of Environmental Science and Policy, 1 Shields Avenue, University of California, Davis, California 95616, USA. aalto@ucdavis.edu
Summary
Fisheries bycatch can benefit nontarget species through reduced competition or predation. Strong species interactions, like those with shared predators, can make these indirect benefits outweigh direct mortality from bycatch.
Area of Science:
- Ecology
- Fisheries Science
- Population Dynamics
Background:
- Nontarget species caught as bycatch in fisheries face direct mortality.
- These species can also experience indirect effects, both positive (release from competition/predation) and negative, due to species interactions.
- The net impact of bycatch depends on the balance between direct mortality and indirect ecological effects.
Purpose of the Study:
- To analyze the relative importance of species interactions in determining the overall effect of bycatch on nontarget species.
- To develop a metric to quantify the trade-off between direct mortality and indirect positive effects.
- To assess how different levels of bycatch impact populations based on community structure.
Main Methods:
- Utilized two- and three-species community modules to model ecological interactions.
- Developed a 'bycatch transition point' metric to evaluate the shift from positive to negative harvest impacts.
- Simulated scenarios with varying strengths of competition and predation.
Main Results:
- In strongly competitive scenarios, release from competition due to harvest can lead to population increases even with moderate bycatch.
- In a three-species model with a shared predator, release from apparent competition outweighed bycatch mortality across a wide parameter range.
- Indirect ecological effects can have a larger impact on populations than direct mortality from bycatch in tightly linked communities.
Conclusions:
- Species interactions significantly influence the population-level consequences of fisheries bycatch.
- The 'bycatch transition point' metric effectively evaluates the balance between positive indirect effects and negative anthropogenic impacts.
- Conservation and management strategies should consider indirect ecological effects in fisheries, especially for species in tightly linked communities.
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