(C) PLOS One This story was originally published by PLOS One and is unaltered. . . . . . . . . . . Climate change disturbances contextualize the outcomes of coral-reef fisheries management across Micronesia [1] ['Peter Houk', 'University Of Guam Marine Laboratory', 'Uog Station', 'Mangilao', 'Andrew Mcinnis', 'David Benavente', 'Cnmi Coastal Resources Management', 'Saipan', 'Northern Mariana Islands', 'Mike Gaag'] Date: 2022-08 Climate change is increasing disturbance events on coral reefs with poorly understood consequences for fish population dynamics and fisheries management. Given growing concerns over food security for the tropical Pacific, we assessed fisheries management policies across a suite of Micronesian islands since 2014 as climate disturbance events have intensified. Disturbances associated with the 2015–2017 ENSO led to significant mortality of corals and calcifying substrates and replacement with algae and detritus, followed by a doubling of biomass across all fish guilds that was proportional to their starting points for all islands. Increased fish biomass was equally attributed to growth of individuals evidenced by increased size structures, and recruitment/survival evidenced by larger population densities. However, the pulsed increase of fish biomass lasted 1–2 years for islands with limited and isolated MPA but remained high for islands with effective MPA networks for 4 years until the study ended. Meanwhile, policies to protect grouper spawning seasons resulted in increased occurrences that were magnified by disturbances and MPA. Grouper increases were largest where both spawning season bans and MPA networks existed, helping to tease apart the management-from-disturbance responses. Smaller rates of increases over longer time were observed for species with commercial fishing bans (bumphead parrotfish, Napoleon wrasse, and sharks). Yet, occurrences remain low in comparison to remote-island baselines, and MPA only provided benefits for juveniles in inner lagoons. Recent trends for these species were less influenced by climate disturbances compared to groupers. The results cautioned how short-term responses of fish assemblages following climate disturbances can provide false signs of success for some management policies without contextual reference baselines that may not exist. Positively, improvements were noted for both MPA and species policies in our region that are expected to benefit reef resilience. Funding: The authors received funding through the Micronesia Conservation Trust that stemmed from several primary sources: 1) National Oceanic and Atmospheric Administration Coral Reef Conservation Cooperative Agreement Grants (PH, AM, MG, SM, JN, BS, TS, CT), 2) Margaret A. Cargill Foundation (PH, SM, JN, TS, JH), 3) the Global Environmental Facility Small Grants Program (PH, AM, MG, SM, JN, BS, TS, CT), 4) The Nature Conservancy Micronesia Program (PH, DB, MM, SM), and 5) The Waitt Foundation Blue Prosperity Micronesia Program (PH, MG, SM, JN, BS, TS, CT, JH). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Copyright: © 2022 Houk et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The present study examined temporal trends in fish assemblages across Micronesia, tropical North Pacific, during the past decade when MPA and species management policies evolved and climate change intensified. One significant driver of increased fisheries management has been the Micronesia Challenge (MC, 2006 to 2030) that represents a novel conservation movement defined by the leaders of five island nations across Micronesia to improve the ecosystem services offered to their societies [ 30 ]. Many islands established and improved MPA networks with dedicated enforcement. In addition, several species policies were developed to address declines in large targeted species. Many islands now have commercial sales ban for bumphead parrotfish, Napoleon wrasse, and sharks, as well as seasonal closures during spawning aggregations of large groupers [ 31 – 34 ]. We used 8 years of benthic and fish monitoring data to evaluate the effectiveness of fisheries policies exposed to climate-induced disturbances associated with the 2015–2017 ENSO. Collectively, our study provided a contextual understanding of how fisheries management policies interacted with each other and interacted with climate disturbances that are becoming more common on coral reefs. Studies have predicted gradual declines in the physiological performance of fish as sea surface temperatures rise and ocean productivity decreases in the tropics across decades [ 14 – 16 ]. However, fewer studies have documented how climate disturbances have begun to reshape fisheries ecology within decades by altering the flux of energy through food webs following disturbances, leading to increased variability in fish abundances [ 17 – 19 ]. Small coral-associated fish decline in abundance and diversity following significant disturbances, but the pulsed algal/detrital influx following coral loss can benefit generalist herbivores and detritivores and lead to homogenization across habitats that lowers diversity [ 12 , 20 – 25 ]. Yet, less consistent findings have been reported for larger fish that are targeted for food and essential for ecosystem resilience, such as parrotfishes, groupers, and snappers [ 16 – 18 , 26 , 27 ]. A metanalysis that controlled for disturbance magnitude and time revealed: 1) temporary increases in herbivore biomass and density as corals died and algae and detritus increased, often perpetuating to higher level consumers and predators, 2) a shift from pelagic to benthic energy production within many primary consumers, and 3) potential long-term declines in fish biomass to levels below pre-disturbance periods that were associated with persistent changes in habitat structure [ 28 ]. Importantly, the positive response of target fish populations in the year(s) following coral mortality and algal/detrital accumulation has been described as a beneficial feedback loop between fish assemblages and reef substrates that supports ecosystem recovery [ 19 ]. However, it is unclear how fishing pressure and management policies may modulate this response [ 12 , 26 , 29 ]. More specifically, how do fisheries disturbance dynamics change when exposed to a growing portfolio of area-and-species based policies? Pacific island societies have coexisted with their marine resources for many generations using traditional forms of reef tenure that are diverse and often tailored to species, life stages and spawning events, taboo areas, and fishing methods [ 1 – 5 ]. Yet, human population growth, lack of employment options, technological advances, urbanization, and cash economies have placed a greater reliance on commercial fisheries with increasing top-down enforcement to try and control exploitation [ 6 , 7 ]. Growing exploitation and reduced traditional knowledge can force management policies to become more streamlined to avoid confusion among stakeholders and address the logistical constraints of enforcement [ 8 ]. For instance, permanent no-take marine protected areas (MPA) have often replaced rotational/seasonal/ceremonial counterparts to cope with high fishing pressure and facilitate resilience [ 9 ], while harvesting bans for many large targeted species, such as bumphead parrotfish, may replace (temporary) customary harvesting policies [ 10 ]. Despite conservation gains in many localities, global studies continue to document declines in marine resources along human gradients that are now being influenced by climate change in poorly understood ways [ 11 – 13 ]. A deeper understanding of management efficacy and potential interactions with disturbance cycles is now critical as climate change intensifies. Methods Micronesia is comprised of many tropical nations that together account for over 6,000 km2 of coral reefs [35]. Past studies documented that unsustainable fishing and land-based pollution represented primary chronic stressors that have impacted Micronesia’s marine resources in recent decades [19, 32–34, 36–38]. Houk et al. [37] further reported that fishing pressure had a disproportionate impact to both fishery resources and overall coral-reef ecosystem condition, while proxies to land-based pollution were noted as secondary drivers in lagoon environments adjacent to urbanized watersheds. Micronesia reefs are also facing increasing frequencies of acute disturbances tied to climate change [39]. Most recently, heat-stress disturbances during the 2015–2017 ENSO have reduced living coral cover by up to 90%, with similar magnitudes of degree heating weeks and impacts on Chuuk, Pohnpei, and Kosrae. Yap experienced unique low level heat stress in late 2014 that was not related to the 2015–2017 ENSO, and then experienced high densities of Crown-of-Thorn starfish in 2015 that coincided with the onset of ENSO (densities ranged between 0 to 6 individuals per 100 m2 during the annual monitoring event, with a mean of 1±0.80 SD per site). The noted disturbance regimes caused similar 15 to 20% losses of corals and/or other calcifying substrates including crustose coralline algae and soft corals, with replacements of turf, macroalgae, and cyanobacteria (S1 Fig). Previous work also documented differential coral loss across Micronesia associated with the recent ENSO based upon taxonomy [39]. Here, we examined fish assemblage responses to ongoing fisheries management policies and the bottom-up pulses of algae and detritus provided to the coral-reef food webs following disturbances. We first evaluated MPA efficacy and the status of several species-specific fisheries policies across the main islands of the Federated States of Micronesia (Yap, Chuuk, Pohnpei, and Kosrae) (Fig 1, S1 and S2 Tables). Marine protected area (MPA) networks were established and enhanced around Yap and Pohnpei during three distinct time frames: i) most were initiated between 2010 and 2013, Yap-3, Pohnpei-5, ii) one was initiate in 2015 in Pohnpei, and iii) two were established between 2018 and 2020, one each on Yap and Pohnpei (Fig 2 and S1 Table). Individual smaller MPA were also established in Chuuk and Kosrae but given their isolation to inner reefs these were omitted from our island-scale MPA analyses within. Second, several local and regional fisheries policies were investigated: 1) a ban on commercial harvesting of Bolbometopon muricatum (established in 2008, 2010, 2012, 2015 for Kosrae, Chuuk, Pohnpei, and Yap, respectively) and Cheilinus undulatus (2010, 2015, and 2019 for Chuuk, Yap, and Pohnpei, respectively), 2) a ban on harvesting groupers during their spawning season in Pohnpei since 2012 and Chuuk since 2015, and 3) a regional ban on shark fishing for all study islands similarly since 2015. Collectively, these species are referred to as large targeted species with active management policies. PPT PowerPoint slide PNG larger image TIFF original image Download: Fig 1. Map of Micronesia and the main populated islands of the Federated States of Micronesia: Yap, Chuuk, Pohnpei, and Kosrae. Red dots represent no-take marine protected areas (MPA) with numbers for Yap and Pohnpei corresponding to Fig 3, gray dots represent non-MPA. The coral reefs base layer is available through the Allen Coral Atlas project (https://www.allencoralatlas.org/, Allen Coral Atlas maps, bathymetry and map statistics are © 2018–2022 Allen Coral Atlas Partnership and Arizona State University and licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). The land base layer was made by the authors based upon the Allen Coral Atlas products. https://doi.org/10.1371/journal.pclm.0000040.g001 PPT PowerPoint slide PNG larger image TIFF original image Download: Fig 2. Trends in fish biomass from spatially-restricted fish surveys (a). Colors indicate fish guilds: darkest green–bumphead parrotfish, green–large herbivore and detritivores, light green–small herbivore and detritivores, dark red–large secondary consumers, light red–small secondary consumers, blue–tertiary consumers. See methods for fish guild details. Black arrows indicate the timing of disturbances. Small black dots represent individual reefs while large black dots indicate annual means. Posterior distributions from Bayesian modeling of the magnitude of the fish response, or the change in fish biomass 1-year after mass coral mortality compared to before, and the duration of fish response measured by the change in fish biomass 3-years following mass bleaching compared to before (b). For Chuuk, data were only available 2-years following the disturbance but statistical analyses for the response duration were all scaled to change in fish biomass per year. https://doi.org/10.1371/journal.pclm.0000040.g002 Data collection Data were collected by all authors in a collaborative partnership with the Micronesia coral-reef and fisheries monitoring network (https://micronesiareefmonitoring.com/). Data were deposited into the Micronesia Reef Monitoring online database that hosts data, provides data access, and offers collaboration with interested individuals and organizations (https://micronesiareefmonitoring.com/). Data are also publicly available through the National Oceanic and Atmospheric Administration Nationa Center for Environmental Information website (https://www.coris.noaa.gov/search/catalog/main/home.page) under accession number 0162463. No permits were required because our work was non-invasive and did not require and collections of marine specimens. Long-term monitoring site selections were stratified across (i) management regimes, (ii) wave exposure, (iii) islands, and (iv) major reef habitats, to be representative of each island [37], with the total number of sites proportional to the area of reef habitat (Fig 1). Therefore, statistical analyses of temporal trends at the island and reef type scales were based upon the same suite of sites, which were indicative of the environments and management regimes of our study islands. This approach controlled for inherent differences in site-based characteristics (i.e., rugosity) to the extent possible, allowing for an evaluation of island-scale policies. Cumulatively, the present study included fisheries data from 95 sites across Micronesia collected between 2014 and 2020. The sizes and abundances of target food-fishes were collected using standard visual census techniques by experienced and calibrated observers. Food-fish were defined as acanthurids, scarids, serranids, carangids, labrids, lethrinids, lutjanids, balistids, kyphosids, mullids, holocentrids, and sharks. Fish surveys were conducted using 12 stationary-point counts (SPCs) separated by equal intervals along 5 x 50 m transect lines established at each site and used for benthic data collection noted below. During each SPC, the observer recorded the species and estimated the size of all fish within a 5 to 6 m circular radius for a period of 3-minutes. Fish sizes were binned into 5 cm categories and converted to biomass using coefficients from regional fishery-dependent data where available [19, 32, 36], or else from FishBase (www.fishbase.org). Total biomass and biomass across size-based trophic guilds were derived from these surveys, with guilds previously defined by trophic level and maximum body sizes [19]. The spatially-restricted data described above were available from 2014 to 2020. Because large targeted fish often avoid observers and may not be well captured in the spatially-restrictive surveys, a second spatially-unrestricted method was adopted in 2020. The second observer maintained a distance of 5 m behind the primary observer and conducted 3-minute SPC fish counts of all fish larger than 40 cm with no spatial restrictions. The species examined by this study included: 1) Bolbometopon muricatum or bumphead parrotfish, 2) Cheilinus undulatus or Napoleon wrasse, 3) large groupers consisting of Plectropomus spp. and Epinepheleus spp. with asymptotic sizes greater than 40 cm, and 4) sharks (Carcharhinus amblyrhynchos, Triaenodon obesus, and Carcharhinus melanopterus—grey-reef, white-tip, and black-tip sharks). In addition, we transcribed data from rapid ecological assessments that were conducted in the mid-2000’s for the islands of Yap and Pohnpei to gain a unique historical perspective for potential shifts in bumphead parrotfish and Napoleon wrasse that were observed [40, 41]. Historical species checklists represented presence/absence data for each site based upon similar dive profiles as our study. Thus, historical data were similar to spatially-unrestricted observations conducted in 2020 once aggregated to the site level and converted to presence/absence data. Last, previously published benthic data were summarized to investigate the connection between the disturbance events, the subsequent increase in non-calcifying algal/detrital substrates that emerged as corals and other calcifying organisms died, and the increases in both fish density and biomass shortly after disturbances [39]. Benthic data were collected from standardized photographs taken at 1 m intervals on the transect lines, with benthic substrates recorded under 5 randomly placed dots from each photo (S1 Fig, see [42] for further details). [END] --- [1] Url: https://journals.plos.org/climate/article?id=10.1371/journal.pclm.0000040 Published and (C) by PLOS One Content appears here under this condition or license: Creative Commons - Attribution BY 4.0. via Magical.Fish Gopher News Feeds: gopher://magical.fish/1/feeds/news/plosone/