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Carvalho, P. G., Jupiter, S. D., Januchowski-Hartley, F. A., Goetze, J., Claudet, J., Weeks, R., et al. (2019). Optimized fishing through periodically harvested closures. J. Appl. Ecol., 56(8), 1927–1936.
Résumé: Periodically harvested closures are a widespread, centuries-old form of fisheries management that protects fish between pulse harvests and can generate high harvest efficiency by reducing fish wariness of fishing gear. However, the ability for periodic closures to also support high fisheries yields and healthy marine ecosystems is uncertain, despite increased promotion of periodic closures for managing fisheries and conserving ecosystems in the Indo-Pacific. We developed a bioeconomic fisheries model that considers changes in fish wariness, based on empirical field research, and quantified the extent to which periodic closures can simultaneously maximize harvest efficiency, fisheries yield and conservation of fish stocks. We found that periodic closures with a harvest schedule represented by closure for one to a few years between a single pulse harvest event can generate equivalent fisheries yield and stock abundance levels and greater harvest efficiency than achievable under conventional fisheries management with or without a permanent closure. Optimality of periodic closures at maximizing the triple objective of high harvest efficiency, high fisheries yield, and high stock abundance was robust to fish life history traits and to all but extreme levels of overfishing. With moderate overfishing, there emerged a trade-off between periodic closures that maximized harvest efficiency and no-take permanent closures that maximized yield; however, the gain in harvest efficiency outweighed the loss in yield for periodic closures when compared with permanent closures. Only with extreme overfishing, where fishing under nonspatial management would reduce the stock to <= 18% of its unfished level, was the harvest efficiency benefit too small for periodic closures to best meet the triple objective compared with permanent closures. Synthesis and applications. We show that periodically harvested closures can, in most cases, simultaneously maximize harvest efficiency, fisheries yield, and fish stock conservation beyond that achievable by no-take permanent closures or nonspatial management. Our results also provide design guidance, indicating that short closure periods between pulse harvest events are most appropriate for well-managed fisheries or areas with large periodic closures, whereas longer closure periods are more appropriate for small periodic closure areas and overfished systems.
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Crochelet, E., Barrier, N., Andrello, M., Marsac, F., Spadone, A., & Lett, C. (2020). Connectivity between seamounts and coastal ecosystems in the Southwestern Indian Ocean. Deep-Sea Res. Part II-Top. Stud. Oceanogr., 176, 104774.
Résumé: Understanding larval connectivity patterns is critical for marine spatial planning, particularly for designing marine protected areas and managing fisheries. Patterns of larval dispersal and connectivity can be inferred from numerical transport models at large spatial and temporal scales. We assess model-based connectivity patterns between seamounts of the Southwestern Indian Ocean (SWIO) and the coastal ecosystems of Mauritius, La Reunion, Madagascar, Mozambique and South Africa, with emphasis on three shallow seamounts (La Pemuse [LP], MAD-Ridge [MR] and Walters Shoal [WS]). Using drifter trajectory and a Lagrangian model of ichthyo-plankton dispersal, we show that larvae can undertake very long dispersion, with larval distances increasing with pelagic larval duration (PLD). There are three groups of greater connectivity: the region between the eastern coast of Madagascar, Mauritius and La Reunion islands; the seamounts of the South West Indian Ridge; and the pair formed by WS and a nearby un-named seamount. Connectivity between these three groups is evident only for the longest PLD examined (360 d). Connectivity from seamounts to coastal ecosystems is weak, with a maximum of 2% of larvae originating from seamounts reaching coastal ecosystems. Local retention at the three focal seamounts (LP, MR and WS) peaks at about 11% for the shortest PLD considered (15 d) at the most retentive seamount (WS) and decreases sharply with increasing PLD. Information on PLD and age of larvae collected at MR and LP are used to assess their putative origin. These larvae are likely self-recruits but it is also plausible that they immigrate from nearby coastal sites, i.e. the southern coast of Madagascar for MR and the islands of La Reunion and Mauritius for LP.
Mots-Clés: behavior; Biophysical model; Connectivity; conservation; coral-reef fishes; Ichthyop; Lagrangian modelling; larvae dispersal; Larval drift; Larval duration; local retention; madagascar; marine populations; model; population connectivity; recruitment; Seamounts; Southwestern indian ocean; Surface drifters
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D'agata, S., Mouillot, D., Wantiez, L., Friedlander, A. M., Kulbicki, M., & Vigliola, L. (2016). Marine reserves lag behind wilderness in the conservation of key functional roles. Nat. Commun., 7, 12000.
Résumé: Although marine reserves represent one of the most effective management responses to human impacts, their capacity to sustain the same diversity of species, functional roles and biomass of reef fishes as wilderness areas remains questionable, in particular in regions with deep and long-lasting human footprints. Here we show that fish functional diversity and biomass of top predators are significantly higher on coral reefs located at more than 20 h travel time from the main market compared with even the oldest (38 years old), largest (17,500 ha) and most restrictive (no entry) marine reserve in New Caledonia (South-Western Pacific). We further demonstrate that wilderness areas support unique ecological values with no equivalency as one gets closer to humans, even in large and well-managed marine reserves. Wilderness areas may therefore serve as benchmarks for management effectiveness and act as the last refuges for the most vulnerable functional roles.
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Goetze, J. S., Claudet, J., Januchowski-Hartley, F., Langlois, T. J., Wilson, S. K., White, C., et al. (2018). Demonstrating multiple benefits from periodically harvested fisheries closures. J. Appl. Ecol., 55(3), 1102–1113.
Résumé: 1. Periodically harvested closures (PHCs) are one of the most common forms of fisheries management in Melanesia, demonstrating multiple objectives, including sustaining fish stocks and increasing catch efficiency to support small-scale fisheries. No studies have comprehensively assessed their ability to provide short-term fisheries benefits across the entire harvest regime. 2. We present a novel analytical framework to guide a meta-analysis and assist future research in conceptualizing and assessing the potential of PHCs to deliver benefits for multiple fisheries-related objectives. 3. Ten PHCs met our selection criteria and on average, they provided a 48% greater abundance and 92% greater biomass of targeted fishes compared with areas open to fishing prior to being harvested. 4. This translated into tangible harvest benefits, with fishers removing 21% of the abundance and 49% of the biomass within PHCs, resulting in few post-harvest protection benefits. 5. When PHCs are larger, closed for longer periods or well enforced, short-term fisheries benefits are improved. However, an increased availability of fish within PHCs leads to greater removal during harvests. 6. Synthesis and applications. Periodically harvested closures (PHCs) can provide short-term fisheries benefits. Use of the analytical framework presented here will assist in determining long-term fisheries and conservation benefits. We recommend PHCs be closed to fishing for as long as possible, be as large as possible, that compliance be encouraged via community engagement and enforcement, and strict deadlines/goals for harvesting set to prevent overfishing.
Mots-Clés: analytical framework; conservation; coral-reef fishes; customary management; fisheries management; food security; locally managed marine areas; long-term; management; marine protected areas; marine reserve; matter; meta-analysis; metaanalysis; partially protected areas; periodically harvested closures; populations; reserves; small-scale fisheries; video
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Jacquet, C., Mouillot, D., Kulbicki, M., & Gravel, D. (2017). Extensions of Island Biogeography Theory predict the scaling of functional trait composition with habitat area and isolation. Ecol. Lett., 20(2), 135–146.
Résumé: The Theory of Island Biogeography (TIB) predicts how area and isolation influence species richness equilibrium on insular habitats. However, the TIB remains silent about functional trait composition and provides no information on the scaling of functional diversity with area, an observation that is now documented in many systems. To fill this gap, we develop a probabilistic approach to predict the distribution of a trait as a function of habitat area and isolation, extending the TIB beyond the traditional species-area relationship. We compare model predictions to the body-size distribution of piscivorous and herbivorous fishes found on tropical reefs worldwide. We find that small and isolated reefs have a higher proportion of large-sized species than large and connected reefs. We also find that knowledge of species body-size and trophic position improves the predictions of fish occupancy on tropical reefs, supporting both the allometric and trophic theory of island biogeography. The integration of functional ecology to island biogeography is broadly applicable to any functional traits and provides a general probabilistic approach to study the scaling of trait distribution with habitat area and isolation.
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