Abstract
A complete understanding of population connectivity via larval dispersal is of great value to the effective design and management of marine protected areas (MPA). However empirical estimates of larval dispersal distance, self-recruitment, and within season variability of population connectivity patterns and their influence on metapopulation structure remain rare. We used high-resolution otolith microchemistry data from the temperate reef fish Hypsypops rubicundus to explore biweekly, seasonal, and annual connectivity patterns in an open-coast MPA network. The three MPAs, spanning 46 km along the southern California coastline were connected by larval dispersal, but the magnitude and direction of connections reversed between 2008 and 2009. Self-recruitment, i.e. spawning, dispersal, and settlement to the same location, was observed at two locations, one of which is a MPA. Self-recruitment to this MPA ranged from 50–84%; within the entire 60 km study region, self-recruitment accounted for 45% of all individuals settling to study reefs. On biweekly time scales we observed directional variability in alongshore current data and larval dispersal trajectories; if viewed in isolation these data suggest the system behaves as a source-sink metapopulation. However aggregate biweekly data over two years reveal a reef network in which H. rubicundus behaves more like a well-mixed metapopulation. As one of the few empirical studies of population connectivity within a temperate open coast reef network, this work can inform the MPA design process, implementation of ecosystem based management plans, and facilitate conservation decisions.
Highlights
Accurate and robust estimates of larval dispersal and local retention are essential prerequisites to resolving marine colonization patterns, controlling the spread of invasive species, and the design of effective marine protected areas (MPAs) [1,2,3,4]
The natal origins of 89 post-dispersal YOY were determined by comparing their otolith core microchemistry with the chemical reference maps generated from the microchemistry of larval fish otoliths collected from the 6 study sites
As was mentioned in the text, the inherent variability within the larval fish otolith microchemistry dataset resulted in mean DFA classification success of 71.2% in 2008 and 68.4% in 2009
Summary
Accurate and robust estimates of larval dispersal and local retention are essential prerequisites to resolving marine colonization patterns, controlling the spread of invasive species, and the design of effective marine protected areas (MPAs) [1,2,3,4]. Outside of MPAs, benefits accrue when individuals move beyond MPA boundaries (i.e. spillover) increasing the biomass of catchable fish in waters adjacent to MPAs. In addition MPAs may sustain populations on a regional scale by larval dispersal and adult/juvenile movement among reefs [9]. Documentation of MPA self-recruitment and connectivity via larval dispersal will aid in the assessment of MPA success [4]. It will advance our understanding of the benefits MPAs provide marine natural resources yielding useful information for managers tasked with conserving marine biodiversity and moving fisheries toward sustainability [10]. Evidence for this larval reseeding remains elusive
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