Adel Heenan

Human, oceanographic and habitat drivers of central and western Pacific coral reef fish assemblages.

Coral reefs around US- and US-affiliated Pacific islands and atolls span wide oceanographic gradients and levels of human impact. Here we examine the relative influence of these factors on coral reef fish biomass, using data from a consistent large-scale ecosystem monitoring program conducted by scientific divers over the course of >2,000 hours of underwater observation at 1,934 sites, across ~40 islands and atolls. Consistent with previous smaller-scale studies, our results show sharp declines in reef fish biomass at relatively low human population density, followed by more gradual declines as human population density increased further. Adjusting for other factors, the highest levels of oceanic productivity among our study locations were associated with more than double the biomass of reef fishes (including ~4 times the biomass of planktivores and piscivores) compared to islands with lowest oceanic productivity. Our results emphasize that coral reef areas do not all have equal ability to sustain large reef fish stocks, and that what is natural varies significantly amongst locations. Comparisons of biomass estimates derived from visual surveys with predicted biomass in the absence of humans indicated that total reef fish biomass was depleted by 61% to 69% at populated islands in the Mariana Archipelago; by 20% to 78% in the Main Hawaiian islands; and by 21% to 56% in American Samoa.

Context-dependent male mating preferences for unfamiliar females

We used laboratory and field-based experiments to examine male mate choice in the promiscuous Panamanian bishop Brachyrhaphis episcopi (Poeciliidae) (also referred to as Brachyraphis episcopi). As females of this species can store sperm, males could increase their reproductive success by selectively mating with different females. To test this, males in both the laboratory and field were allowed to choose between a familiar (same tank or pool) and an unfamiliar female (different tank or pool). We compared males from streams and seasonally occurring pools to see whether lack of access to new females in pools promotes male mate choice for unfamiliarity. In addition, we chose streams and pools both with and without predatory fish to examine the influence of predation risk. In both the laboratory and the field, males attempted more matings with unfamiliar than familiar females. Field experiments showed that courtship preferences differed between males from populations with and without predatory fish: males from populations with predators were choosy only when light levels were dim, whereas males from populations without predators were choosy when light levels were brighter. Males from both streams and pools discriminated between familiar and unfamiliar females, but there were no differences in mating preferences between males from each habitat. Although the reasons for a preference for unfamiliar females remain unclear, the plasticity of this behaviour is evident. Differences in male mate choice between populations with and without predators suggest that males may face a trade-off between the costs and benefits of being choosy.

Monitoring Herbivorous Fishes as Indicators of Coral Reef Resilience in American Samoa

Resilience-based management aims to promote or protect processes and species that underpin an ecosystems capacity to withstand and recover from disturbance. The management of ecological processes is a developing field that requires reliable indicators that can be monitored over time. Herbivory is a key ecological process on coral reefs, and pooling herbivorous fishes into functional groups based on their feeding mode is increasingly used as it may quantify herbivory in ways that indicate resilience. Here we evaluate whether the biomass estimates of these herbivore functional groups are good predictors of reef benthic assemblages, using data from 240 sites from five island groups in American Samoa. Using an information theoretic approach, we assembled a candidate set of linear and nonlinear models to identify the relations between benthic cover and total herbivore and non-herbivore biomass and the biomass of the aforementioned functional groups. For each benthic substrate type considered (encrusting algae, fleshy macroalgae, hard coral and turf algae), the biomass of herbivorous fishes were important explanatory variables in predicting benthic cover, whereas biomass of all fishes combined generally was not. Also, in all four cases, variation in cover was best explained by the biomass of specific functional groups rather than by all herbivores combined. Specifically: 1) macroalgal and turf algal cover decreased with increasing biomass of ‘grazers/detritivores’; and 2) cover of encrusting algae increased with increasing biomass of ‘grazers/detritivores’ and browsers. Furthermore, hard coral cover increased with the biomass of large excavators/bio-eroders (made up of large-bodied parrotfishes). Collectively, these findings emphasize the link between herbivorous fishes and the benthic community and demonstrate support for the use of functional groups of herbivores as indicators for resilience-based monitoring.

Natural bounds on herbivorous coral reef fishes

Humans are an increasingly dominant driver of Earths biological communities, but differentiating human impacts from natural drivers of ecosystem state is crucial. Herbivorous fish play a key role in maintaining coral dominance on coral reefs, and are widely affected by human activities, principally fishing. We assess the relative importance of human and biophysical (habitat and oceanographic) drivers on the biomass of five herbivorous functional groups among 33 islands in the central and western Pacific Ocean. Human impacts were clear for some, but not all, herbivore groups. Biomass of browsers, large excavators, and of all herbivores combined declined rapidly with increasing human population density, whereas grazers, scrapers, and detritivores displayed no relationship. Sea-surface temperature had significant but opposing effects on the biomass of detritivores (positive) and browsers (negative). Similarly, the biomass of scrapers, grazers, and detritivores correlated with habitat structural complexity; however, relationships were group specific. Finally, the biomass of browsers and large excavators was related to island geomorphology, both peaking on low-lying islands and atolls. The substantial variability in herbivore populations explained by natural biophysical drivers highlights the need for locally appropriate management targets on coral reefs.

Ecosystem monitoring for ecosystem‐based management: using a polycentric approach to balance information trade‐offs

Ecosystem monitoring for ecosystem-based management: using a polycentric approach to balance information trade-offs Adel Heenan*, Kelvin Gorospe, Ivor Williams, Arielle Levine, Paulo Maurin, Marc Nadon, Thomas Oliver, John Rooney, Molly Timmers, Supin Wongbusarakum and Russell Brainard Joint Institute for Marine and Atmospheric Research, University of Hawai’i, M anoa, Honolulu, HI 96822, USA; NOAA Pacific Islands Fisheries Science Center, National Marine Fisheries Service, Honolulu, HI 96818, USA; Department of Geography, San Diego State University, San Diego, CA 92182, USA; and NOAA Coral Reef Conservation Program (The Baldwin Group Inc.), Silver Spring, MD 20910, USA

Restoring depleted coral-reef fish populations through recruitment enhancement: a proof of concept

To determine whether enhancing the survival of new recruits is a sensible target for the restorative management of depleted coral-reef fish populations, settlement-stage ambon damsel fish Pomacentrus amboinensis were captured, tagged and then either released immediately onto small artificial reefs or held in aquaria for 1 week prior to release. Holding conditions were varied to determine whether they affected survival of fish: half the fish were held in bare tanks (non-enriched) and the other half in tanks containing coral and sand (enriched). Holding fish for this short period had a significantly positive effect on survivorship relative to the settlement-stage treatment group that were released immediately. The enrichment of holding conditions made no appreciable difference on the survival of fish once released onto the reef. It did, however, have a positive effect on the survival of fish while in captivity, thus supporting the case for the provision of simple environmental enrichment in fish husbandry. Collecting and holding settlement-stage fish for at least a week before release appear to increase the short-term survival of released fish; whether it is an effective method for longer-term enhancement of locally depleted coral-reef fish populations will require further study.

Ecological Impacts of the 2015/16 El Niño in the Central Equatorial Pacific

The authors thank Cisco Werner (NOAA/NMFS) for proposing this special issue and encouraging our submission. We thank each of the editors, Stephanie Herring, Peter Stott, and Nikos Christidis, for helpful guidance and support throughout the submittal process. We also thank each of the anonymous external reviewers for thoughtful guidance and suggestions to improve the manuscript. REB, TO, RV, AH, and BVA are grateful for support from the NOAA Coral Reef Conservation Program. AC acknowledges support from the National Science Foundation for the following awards: OCE 1537338, OCE 1605365, and OCE 1031971. This is PMEL contribution no. 4698. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. government. The views expressed in the article are not necessarily those of the U.S. government. (NOAA Coral Reef Conservation Program; OCE 1537338 - National Science Foundation; OCE 1605365 - National Science Foundation; OCE 1031971 - National Science Foundation)

Long-term monitoring of coral reef fish assemblages in the Western central pacific

Throughout the tropics, coral reef ecosystems, which are critically important to people, have been greatly altered by humans. Differentiating human impacts from natural drivers of ecosystem state is essential to effective management. Here we present a dataset from a large-scale monitoring program that surveys coral reef fish assemblages and habitats encompassing the bulk of the US-affiliated tropical Pacific, and spanning wide gradients in both natural drivers and human impact. Currently, this includes >5,500 surveys from 39 islands and atolls in Hawaii (including the main and Northwestern Hawaiian Islands) and affiliated geo-political regions of American Samoa, the Commonwealth of the Northern Mariana Islands, Guam, and the Pacific Remote Islands Areas. The dataset spans 2010–2017, during which time, each region was visited at least every three years, and ~500–1,000 surveys performed annually. This standardised dataset is a powerful resource that can be used to understand how human, environmental and oceanographic conditions influence coral reef fish community structure and function, providing a basis for research to support effective management outcomes.

Pacific Reef Assessment and Monitoring Program. Data report : ecological monitoring 2012-2013 : reef fishes and benthic habitats of the main Hawaiian Islands, American Samoa, and Pacific Remote Island Areas

Acknowledgements Thanks to all those onboard the NOAA shipsHìialakai and Oscar Elton Sette for their logistical and field support during the 2012-2013 Pacific Reef Assessment and Monitoring Program (Pacific RAMP) research cruises and to the following divers for their assistance with data collection; and Darla White. We thank Rusty Brainard for his tireless support of Pacific RAMP and the staff of NOAA PIFSC CRED for assistance in the field and data management.

Using Participatory Methods to Assess Data Poor Migrant Fisheries in Kenya

ABSTRACT Spatial information is limited for artisanal fisheries management and almost entirely absent for migrant fishers. Here, we addressed this data gap for East African migrant fishers via participatory mapping methods. We worked with 14 migrant fishing vessels operating from four fish landing sites in Kenya. We monitored individual vessels using GPS tracking to produce fishing ground intensity maps. We then generated fishing preference maps via focus group discussions. The fishing intensity maps provided high-resolution spatial information on fishing activities, whereas the fishing preference maps identified preferred fishing grounds. These two techniques generally showed high agreement. By further integrating these two fisher coproduced maps with supplemental vessel logbook data, it is clear that any spatial management measures would most affect migrant fishers using ringnets, hook and line, and cast nets gear. Our successful application of low-technology participatory mapping techniques to provide geospatial fisheries data have broad application to data poor fisheries worldwide.