Larval dispersal and movement patterns of coral reef fishes, and implications for marine reserve network design

Abstract

Well-designed and effectively managed networks of marine reserves can be effective tools for both fisheries management and biodiversity conservation. Connectivity, the demographic linking of local populations through the dispersal of individuals as larvae, juveniles or adults, is a key ecological factor to consider in marine reserve design, since it has important implications for the persistence of metapopulations and their recovery from disturbance. For marine reserves to protect biodiversity and enhance populations of species in fished areas, they must be able to sustain focal species (particularly fishery species) within their boundaries, and be spaced such that they can function as mutually replenishing networks whilst providing recruitment subsidies to fished areas. Thus the configuration (size, spacing and location) of individual reserves within a network should be informed by larval dispersal and movement patterns of the species for which protection is required. In the past, empirical data regarding larval dispersal and movement patterns of adults and juveniles of many tropical marine species have been unavailable or inaccessible to practitioners responsible for marine reserve design. Recent empirical studies using new technologies have also provided fresh insights into movement patterns of many species and redefined our understanding of connectivity among populations through larval dispersal. Our review of movement patterns of 34 families (210 species) of coral reef fishes demonstrates that movement patterns (home ranges, ontogenetic shifts and spawning migrations) vary among and within species, and are influenced by a range of factors (e.g. size, sex, behaviour, density, habitat characteristics, season, tide and time of day). Some species move <0.1-0.5 km (e.g. damselfishes, butterflyfishes and angelfishes), <0.5-3 km (e.g. most parrotfishes, goatfishes and surgeonfishes) or 3-10 km (e.g. large parrotfishes and wrasses), while others move tens to hundreds (e.g. some groupers, emperors, snappers and jacks) or thousands of kilometres (e.g. some sharks and tuna). Larval dispersal distances tend to be <5-15 km, and self-recruitment is common. Synthesising this information allows us, for the first time, to provide species, specific advice on the size, spacing and location of marine reserves in tropical marine ecosystems to maximise benefits for conservation and fisheries management for a range of taxa. We recommend that: (i) marine reserves should be more than twice the size of the home range of focal species (in all directions), thus marine reserves of various sizes will be required depending on which species require protection, how far they move, and if other effective protection is in place outside reserves; (ii) reserve spacing should be <15 km, with smaller reserves spaced more closely; and (iii) marine A. L. Green and others reserves should include habitats that are critical to the life history of focal species (e.g. home ranges, nursery grounds, migration corridors and spawning aggregations),...

Efficacy of an established marine protected area at sustaining a queen conch Lobatus gigas population during three decades of monitoring

“…Populations connected by surface-advected coral propagules also have genetic structure shaped by oceanography (Baums et al 2006, Wood et al 2016. A review of dispersal focused on reef fish (with a similar length pelagic dispersal phase as conch) suggested that scales of protection should be equivalent to double the dispersal potential (Green et al 2015). However, the continuing decline we observed in the ECLSP suggests that in some areas source and sink dynamics outweigh generalizations and can cause inefficacy (D'Agostini et al 2015).…”

“…While even isolated populations with low larval supply may be replenished, given enough time (Gilmour et al 2013), it can be argued that connectivity likely dominates habitat quality as the primary mechanism of efficacy for self-sustaining MPAs in some systems (Pinsky et al 2012, White et al 2014, D'Agostini et al 2015. Overall, a review of movement patterns suggests that the most effective MPAs encompass both adult and larval dispersal while also containing the appropriate mix of key habitats for any given species (Green et al 2015). If a species has limited movement as an adult, the ecological efficacy of a MPA in protecting a population should depend on both the habitats protected and the supply of larvae.…”

Levels and drivers of fishers&#8217; compliance with marine protected areas

“…Planning considerations such as MPA size, spacing, and location can also influence the achievement of ecological objectives (Green et al 2014). However, there are critical trade-offs in planning between achieving compliance and achieving ecological objectives.…”

“…1). Ecological considerations for planning MPAs commonly suggest that large, no-take MPAs are preferable to smaller ones because they can, for instance, encompass more habitats and highly mobile species, and offer higher levels of protection (Edgar et al 2014, Green et al 2014. However, larger MPAs can be harder to manage, and excluding fishing from coastal MPAs in developing countries is likely to create friction with fishing communities (Ban et al 2011); hence, compliance and resultant ecological health are likely to weaken.…”

Integrating impact evaluation in the design and implementation of monitoring marine protected areas

“…This was accounted for in selections of control sites and will also be incorporated in post-hoc analyses. We identified an appropriate buffer of 5 km to account for the home range of most of the species of interest [47]. While most of the control sites are located at distances more than 10 km from MPA boundaries, four non-MPA sites are located less than 5 km from the boundaries of MPAs.…”