Current Biology
Volume 27, Issue 18, 25 September 2017, Pages 2843-2848.e2
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Old-Growth Fishes Become Scarce under Fishing

https://doi.org/10.1016/j.cub.2017.07.069Get rights and content
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Highlights

  • Fishing reduced the proportion of old fish in 79% to 97% of populations

  • The magnitude of decline was greater than 90% in 32% to 41% of populations

  • US Southeast and West Coast had the most pronounced and consistent age truncation

  • Shifting baselines and recruitment variation can bias estimates of age truncation

Summary

Researchers have long recognized the importance of ecological differences at the species level in structuring natural communities yet until recently have often overlooked the influence of intraspecific trait variation, which can profoundly alter community dynamics [1]. Human extraction of living resources can reduce intraspecific trait variation by, for example, causing truncation of age and size structure of populations, where numbers of older individuals decline far more with exploitation than younger individuals. Age truncation can negatively affect population and community stability, increasing variability in population and community biomass [2, 3, 4, 5, 6], reducing productivity [7, 8, 9, 10] and life-history diversity in traits such as the spatial and temporal pattern of reproduction and migration [4, 11, 12, 13, 14, 15, 16]. Here, we quantified the extent of age truncation in 63 fished populations across five ocean regions, as measured by how much the proportions of fish in the oldest age groups declined over time. The proportion of individuals in the oldest age classes decreased significantly in 79% to 97% of populations (compared to historical or unfished values, respectively), and the magnitude of decline was greater than 90% in 32% to 41% of populations. The pervasiveness and intensity of age truncation indicates that fishing is likely reducing the stability of many marine communities. Our findings suggest that more emphasis should be given to management measures that reduce the impact of fishing on age truncation, including no-take areas, slot limits that prohibit fishing on all except a narrow range of fish sizes, and rotational harvesting.

Keywords

age truncation
age structure
fisheries management
maternal effects
population dynamics
life-history diversity

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