Rapid Effects of Marine Reserves via Larval Dispersal

School of Natural Resources, University of Arizona, Tucson, Arizona, United States of America.
PLoS ONE (Impact Factor: 3.23). 02/2009; 4(1):e4140. DOI: 10.1371/journal.pone.0004140
Source: PubMed


Marine reserves have been advocated worldwide as conservation and fishery management tools. It is argued that they can protect ecosystems and also benefit fisheries via density-dependent spillover of adults and enhanced larval dispersal into fishing areas. However, while evidence has shown that marine reserves can meet conservation targets, their effects on fisheries are less understood. In particular, the basic question of if and over what temporal and spatial scales reserves can benefit fished populations via larval dispersal remains unanswered. We tested predictions of a larval transport model for a marine reserve network in the Gulf of California, Mexico, via field oceanography and repeated density counts of recently settled juvenile commercial mollusks before and after reserve establishment. We show that local retention of larvae within a reserve network can take place with enhanced, but spatially-explicit, recruitment to local fisheries. Enhancement occurred rapidly (2 yrs), with up to a three-fold increase in density of juveniles found in fished areas at the downstream edge of the reserve network, but other fishing areas within the network were unaffected. These findings were consistent with our model predictions. Our findings underscore the potential benefits of protecting larval sources and show that enhancement in recruitment can be manifested rapidly. However, benefits can be markedly variable within a local seascape. Hence, effects of marine reserve networks, positive or negative, may be overlooked when only focusing on overall responses and not considering finer spatially-explicit responses within a reserve network and its adjacent fishing grounds. Our results therefore call for future research on marine reserves that addresses this variability in order to help frame appropriate scenarios for the spatial management scales of interest.

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Available from: Richard Cudney-Bueno
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    • "As a fisheries tool, no-take marine reserves can protect and restore marine fisheries through an increase in biomass, age, and density of protected species inside the reserve, leading to an increase in the reproductive potential of these species due to lower mortality from the prohibition on harvesting. This increase in density and reproduction can lead to density-dependent dispersal of juvenile and adults ( " spillover " ) and export of larvae and eggs across reserve borders to the surrounding fished areas (Gell & Roberts 2003, Cudney-Bueno et al. 2009, Goñi et al. 2010), though the effectiveness can be variable based on, for example, prevailing currents, reproductive timing, or larval duration of target species (Cudney-Bueno et al. 2009, Carson et al. 2010, Cole et al. 2010). By supplying the nonprotected areas with recruits through " spillover " of juveniles and adults and export of eggs and larvae, the fishery can be replenished and maintained. "
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    ABSTRACT: The Sapodilla Cayes Marine Reserve (SCMR) was established in 1996 to protect the queen conch (Strombus gigas) fishery in southern Belize. However, no systematic survey of queen conch populations in the SCMR had been conducted. To determine the state of the queen conch population and to provide a baseline to measure management effectiveness, we conducted shallow-water surveys of historical conch fishing areas from 2006 2008 during July and August. We collected data on habitat, depth, maturity, length, and density. We sampled 1,778 conch at eight sites throughout the reserve. Conch were found primarily in seagrass meadows (88.6%) in an average depth of 1.7 +/- 0.01 m (range: 0.3-4.9 m). 93% of conch were juveniles and the percentage of juveniles in aggregations averaged 85.0 +/- 3.8 (range 28.6 - 100.00%). Average shell length was 14.6 +/- 0.1 cm (range: 6.5-25.0 cm) and varied among aggregations and among years within aggregations. 85% of conch were below the legal harvestable size for Belize. Average density (all age classes) ranged from 0.00 +/- 0.00 to 4014.29 +/- 741.12 conch/ha and varied among sites and year. Average adult density ranged from to 0.00 +/- 0.00 to 75.00 +/- 41.19 conch/ha, subadult density ranged from 0.00 +/- 0.00 to 214.29 +/- 67.01 conch/ha, and juvenile density ranged from 0.00 +/- 0.00 conch/ha to 3785.00 +/- 737.57. Only twice was an aggregation above the density threshold required for reproduction (50 conch/ha). The SCMR appears to be an important nursery area for queen conch.
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    • "Readily-available biological and oceanographic data (e.g. satellite-derived data on spatial variability of high-productivity areas) (Hidalgo-González and Alvarez-Borrego, 2011), combined with existing oceanographic-ecological models (Marinone et al., 2008; Cudney-Bueno et al., 2009), can help to improve planning for processes in the Gulf of California and elsewhere. "
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    ABSTRACT: 1.Overfishing, pollution, coastal development and climate change threaten marine biodiversity globally and compromise the services that marine ecosystems provide. Systematic conservation planning (SCP) provides a framework to identify areas where actions can be effective in addressing these threats, while minimizing the costs of interventions. This study investigated the application of SCP in the Gulf of California, a marine hotspot where seven prioritization exercises have been undertaken. 2.The review of planning exercises showed that the use of SCP methods has progressed slowly (gaps include planning for land–sea connections and ecosystem services) and highlighted benefits and difficulties of applying SCP principles and tools. 3.Despite some convergence, important spatial differences were found in priorities between plans. Convergence was evident in well-studied shallow and benthic marine ecosystems. There were also important differences related to the planning approach, methods and extent. Divergence between methodological and spatial similarities between plans suggests that additional factors (e.g. manually delineating priority areas, incorporating updated datasets, random error), in addition to data and objectives, play an important role in defining the distribution of conservation priorities. 4.According to expert opinion, the implementation of new marine protected areas (MPAs) in the region has been influenced by some of the planning exercises. However, uptake of planning outputs has progressed slowly for many reasons (e.g. conflicting mandates and interests between organizations, limited technical capacities and resources, insufficient political commitment). Other benefits of planning included: developing institutional skills and knowledge; improving collaboration and coordination between organizations (including agencies, and local, regional and national NGOs); converging on the need to assess priorities for marine conservation in regional context; and building trust among organizations. 5.The existence of multiple marine conservation plans in the Gulf of California also highlighted some of the complexities and benefits of having multiple sets of priorities.
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    • "In theory, with these sources of information, the effectiveness of networks of reserves may be optimised in terms of reproductive output of individual or mixed stocks (Sala et al. 2002, Roberts et al. 2003). Nevertheless, application of marine reserve networks and analysis of their effectiveness as a network, remains relatively rare worldwide (but see Russ et al. 2008, Cudney-Bueno et al. 2009, Hamilton et al. 2010). To date relatively few studies have analysed how networks of reserves influence multiple subpopulations at the landscape scale. "
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    ABSTRACT: Theory suggests that marine reserve networks can maintain wide geographical distributions of exploited fish and invertebrates. Since 2005, ten regions in southwest New Zealand have been designated no-take marine reserves nested within eleven commercial fishing exclusion zones. We observed increases in abundance of rock lobster (Jasus edwardsii) and blue cod (Parapercis colias) from 2002-2010 within some marine reserves, but not in the other management zones. Mature size distributions of rock lobsters were only observed within protected areas. Model based inference ranked environmental descriptors versus area under protection in explaining abundance and changes in abundance observed within marine reserves and indicated that J. edwardsii became most abundant in larger marine reserves, but only under specific environmental conditions. P. colias became most abundant in large marine reserves, particularly those with larger buffers against commercial fishing. Analysis of population changes for both species across Fiordland since implementation of the reserve network (2006-2010) indicated that marine reserves resulted in either increases in, or maintenance of abundance in the face of regional declines. We highlight the potential effectiveness of networks of marine reserves in maintaining subpopulations with high abundance and mature size structure across large geographical areas, particularly if key criteria are incorporated.
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