Larval dispersal reveals regional sources and sinks in the Great Barrier Reef

Abstract

We analysed simulated connectivity patterns for reef fish larvae in the Cairns section of the Great Barrier Reef, and identified 2 key subregions that exhibit regional scale source-sink dynamics. The source and sink were separated latitudinally by a boundary at 16.1°S, with the source subregion lying to the north. Larval transport between the 2 subregions was predominantly unidirectional, from north to south. Only a few local populations, described here as 'gateway reefs', were able to transport larvae from the sink subregion to the source subregion and thus maintain the connectedness of the metapopulation. The northern subregion was able to persist without external larval supply, but when conditions were recruitment limited, the southern subregion depended on larval supply from the north to persist. The relative autonomy of the northern subregion, and its importance in sustaining the southern subregion, will influence the effectiveness of conservation efforts. KEY WORDS: Larval dispersal · Source-sink · Coral reef fish · Metapopulation dynamicsResale or republication not permitted without written consent of the publisher

Identifying critical regions in small-world marine metapopulations

“…3 and Methods). Theoretically, at some extremely high level of density dependence, spatial heterogeneity in larval connectivity, which creates differences in the importance of subpopulations, will diminish (40). We tested the effect of different levels of larval density dependence by altering demographic parameters (Methods) and found that the robustness of metapopulations to subpopulation removal was indeed affected by these changes; removal curves were steeper at lower compensation ratios (CRs) and less intense larval density dependence (Fig.…”

Returns from matching management resolution to ecological variation in a coral reef fishery

“…Often dispersal is thought of as having a smoothing effect-reducing spatial heterogeneity and thereby lowering the potential gains from high-resolution policy prescriptions. However, when dispersal is asymmetric, spatial ecological heterogeneity can be exacerbated rather than reduced [5,23,24]. Moreover, dispersal between different locations can create additional management complexities.…”

A coupled ecological–hydrodynamic model for the spatial distribution of sessile aquatic species in thermally forced basins

“…Here we consider one of the simplest and most used, the Beverton-Holt model (Beverton and Holt, 1957), slightly modified as proposed in Hassell (1975) to account for demographic fluctuations. This model was originally formalized to describe the dynamics of fish stocks and has already been used to link larval dispersal to recruitment dynamics in sessile aquatic population with a benthonic life stage (e.g., James et al, 2002;Armsworth, 2002;Bode et al, 2006). In the modified Beverton-Holt model, larval survival is supposed to decrease with the abundance of settling larvae itself due to competition for limited resources (either nutrients or space, or both).…”

“…Larval transport by the water flow is modeled by a Lagrangian approach, which represents a common choice in the literature (e.g., Siegel et al, 2003; see also Werner et al, 2007;Cowen and Sponaugle, 2009 and more references therein), since it provides a natural and accurate framework to describe larval movement. In our simple approach, we consider that dispersing larvae are passively transported by currents, i.e., that they are unable to swim, orient themselves or perform vertical migrations, apart from the capability to settle at the bottom of the water body in the location where they reach maturity (e.g., Bode et al, 2006). Although the assumption of passive transport is quite common in the description of larval dispersal (e.g., James et al, 2002;Aiken et al, 2007), it should be noted that active movements can also play a remarkable role in determining the mean distance traveled by larvae (Steneck, 2006;Cowen et al, 2006;Paris et al, 2007;Werner et al, 2007;Cowen and Sponaugle, 2009).…”

“…Remarkably, very few works have reported the results of long-term analyses in the context of larval dispersal. In point of fact, a recent literature survey (Miller, 2007) has reported that just 5 on the 69 reviewed papers on fish recruitment in marine ecosystems were multigenerational (e.g., Rose et al, 2003; see also Bode et al, 2006). Moreover, most works devoted to the analysis of larval dispersal refer to marine ecosystems, while we specifically address the study of closed water bodies.…”