Tandem 1: Evolutionary management of harvested populations

Background - Almost all harvesting practises exert unwanted selection onto the target populations. One example is selection on life-history and behavioral traits in exploited fish populations. All fishing gears are selective, most often with respect to a minimal size of the fish, determined by mesh size, but also in terms of behavioral traits in case of active fishing gear (e.g. long-lining, angling). In the past decade, multiple examples of life-history changes over a few generations of heavy fishing have been documented. A dramatic outcome is that fisheries "breed" fish populations with a mean reduction in age and size at maturity, and sometimes even reduced growth rates. Such changes in vital traits may have profound cascading effects. For example, since food spectra are very much gape width driven, different sizes of fish will also eat different prey, with concomittant effects on the food-web role of a focal fish population that is now, on average, smaller. Because aquaculture cannot replace the complex environmental conditions for most wild caught fish species, harvesting of wild populations will continue. It is thus imperative to reduce, and possibly reverse, the unwanted effects of fisheries-induced selection, along with a general demographic protection of many fish stocks.

Overall objectives

  • Explore how the ecological and economic processes that lead to  evolutionary pressure on harvested populations can be reverted.
  • Develop and model novel harvesting rules that mitigate   unwanted evolutionary effects and sustain both viable levels of harvest and critical ecosystem functions.

Doctoral Project 1.1: Fisheries-induced evolution

Specific aims

  • Analysis of the underlying factors that promote or restrain fishery-induced changes in fish populations (e.g., life-history characteristics, habitat and ecosystem types, fishing gear and intensity, type of management regime).
  • Assess the "selective" load that remains in the population of a fished stock and may persist over decades once the fishing pressure is alleviated, using quantitative genetic modeling.
  • Build the biological basis to reform (if required) the management regimes of exploited fish stocks in the North Atlantic area where time-series data of key traits are available.

People working on this project

  • Prof. Dr. Thorsten Reusch
  • MSc Kwi Young Han

PI's Homepage: https://www.geomar.de/en/mitarbeiter/fb3/ev/treusch/

Doctoral Project 1.2: Evolutionary fishery economics and management

Specific aims

  • Understand the technical and economic factors that lead to fisheries-induced evolution
  • Investigate with a combination of ecological-evolutionary and ecological-economic models how the history of fisheries-induced evolution influences future sustainable and economically efficient fisheries management.
  • Quantify an option value of conservative fishing with adjusted selectivity patterns.

People working on this project

  • Prof. Dr. Martin Quaas
  • MSc

PI 's Homepage: https://www.idiv.de/groups_and_people/core_groups/biodiversity_economics.html