Standard Talk (15 mins) Australian Society for Fish Biology Conference 2022

How valuable are metrics of population connectivity for area-based marine management? (#58)

Nils C Krueck 1
  1. University of Tasmania, Hobart, TAS, Australia

The dispersal of fish larvae by ocean currents is likely to be an increasingly important driver of marine population connectivity across fragmented habitats. A boost in availability of larval dispersal data from biophysical simulations has therefore led to routine calculations of population connectivity metrics that are used to support area-based marine management decisions, including the placement of Marine Protected Areas (MPAs). However, simulation-derived data on larval dispersal remains highly variable and uncertain because field measurements for empirical validation are notoriously difficult to implement. Here I present a case study on coral reef fishes which confirms that consideration of larval dispersal could be critical for area-based management to help recover both fish populations and fisheries from depletion, thereby mitigating potentially severe impacts on coastal communities. Importantly, I further show that site selection for management or protection can be effective in achieving multiple objectives even if based on simple and empirically measurable metrics of population connectivity. Maximizing larval export contributions from MPAs to surrounding areas, for example, is likely to be a broadly beneficial site prioritization approach. Across investigated fish families with diverse life histories, this strategy was found to increase catches by a factor of 1.3 ± 0.3 (mean ± SD) and total fish biomass by a factor of 3.2 ± 0.3 compared to conditions without effectively managed or protected areas. These findings are relevant for both the implementation and impact evaluation of global conservation policies, specifically in tropical biodiversity hotspots, where coral reefs are often overfished and increasingly threatened but local communities highly dependent on sustainable fisheries. However, as long as simulation-derived larval dispersal data remains highly uncertain it might best be considered as an additional (albeit potentially critical) rather than primary criterion for site prioritization in the context of area-based marine management.