What happens to reef fish after coral bleaching?

by Adel Heenan

For the past month, researchers aboard the NOAA Ship Hi‘ialakai have been navigating across the Pacific Ocean to survey coral reef ecosystems at remote Wake Atoll and the Mariana Archipelago. This expedition includes additional surveys at Jarvis Island, in the Pacific Remote Islands Marine National Monument, to assess the reef condition and degree of recovery from a catastrophic coral bleaching event in 2014-2015.


Jarvis Island is located in the central Pacific Ocean, close to the equator, and is a small island in the direct path of a deep current that flows east (Figure 1). Because of it’s position right on the equator and the strong currents hitting the island, Jarvis sits in the middle of a major upwelling zone—where cold nutrient rich water is drawn up from the deep. This water fertilizes the whole area, elevating nutrient levels and productivity in the reef ecosystem (Gove et al., 2006). As a result, Jarvis supports exceptionally high biomass of planktivorous and piscivorous fishes (Williams et al., 2015).

Because it is unpopulated and extremely remote, Jarvis provides an important reference point and opportunity to understand the natural structure, function, and variation in coral reef ecosystems. The island also offers a natural laboratory in which the effects of ocean warming can be assessed in the absence of stressors that impact coral reefs where humans are present (e.g., fishing or land-based sources of pollution).

El Niño, La Niña and the global coral bleaching event of 2014-2015
The Equatorial Pacific upwelling at Jarvis alternates between warm El Niño years, when upwelling is weak and oceanic productivity low, and cold La Niña years where upwelling is strong and productivity is high (Gove et al., 2006). Unusually warm sea surface temperatures, and a strong El Niño in 2014-2015, triggered the third recorded global coral bleaching event. At Jarvis, these warmer waters led to widespread coral bleaching and mortality. High sea surface temperatures in 2015 also impacted upwelling at Jarvis, as evidenced by a decrease in the primary productivity around the island.

Teams from the Coral Reef Ecosystem Program recently completed ecological monitoring at Jarvis from April 2–5, 2017. They collected data at 28 stationary point count sites (Figure 2) this year, 30 in 2016, 62 in 2015, 42 in 2012, and 30 in 2010.

FIG2_SPC

Figure 2. The stationary point count method is used to monitor the fish assemblage and benthic communities at the Rapid Ecological Assessment (REA) sites.

Main Observations
Fish biomass tended to be highest on the western side of the island where equatorial upwelling occurs (Figure 3). In 2016, we observed somewhat reduced total fish and total planktivore biomass (Figure 4), but this reduction was within the normal range of observed variability.

There were some significant reductions observed for individual species in 2016. These reductions were noticeable across multiple trophic groups, for instance the planktivorous Whitley’s fusilier (Luzonichthys whitleyi), Olive anthias (Pseudanthias olivaceus), Dark-banded fusilier (Pterocaesio tile), the piscivorous Island trevally (Carangoides orthogrammus), and the coral-dwelling Arc-eyed hawkfish (Paracirrhites arcatus) which is strongly associated with Pocillopora coral heads. Some of these species had returned to previous ranges by 2017, but others remain depleted (Figure 5).

FIG5_FishBiomass

Figure 5. Mean species biomass (± standard error) per survey year at Jarvis.

Very high levels of coral mortality were evident in 2016 surveys and coral cover remained low in 2017. Notably, macroalgal cover increased in 2017, approximately by the amount of coral cover lost in 2016 (Figure 6).

FIG6_PercentCover

Figure 6. Mean percentage cover estimates (± standard error) of benthic habitat per survey year at Jarvis. Data shown for Hard Coral (top, red); macrolagae (middle, green) and CCA: crustose coralline algae (bottom, orange). Note: no benthic data are available for 2008 as we began collected rapid visual estimates of these benthic functional groups in 2010.

Whether this reduction in specific planktivore, piscivore, and live coral-dwelling fish species is a widespread and long-standing shift in the fish assemblages at Jarvis will be the subject of forthcoming research. It seems plausible that they reflect impacts of a prolonged period of reduced food availability and changes to preferred habitat due to the anomalous warm sea conditions in 2014–2015. Our teams will return to Jarvis in 2018 to conduct another assessment in an attempt to answer some of these questions.

FIG7_shark

An emaciated grey reef shark (Carcharhinus amblyrhynchus) observed during a 2017 fish survey. (Photo: NOAA Fisheries/Adel Heenan)

Additional detail on survey methods and sampling design are available in the full monitoring brief: Jarvis Island time trends 2008-2017.

References
Gove J. et al. (2006) Temporal variability of current-driven upwelling at Jarvis Island. J Geo Res: Oceans 111, 1-10, doi: 10.1029/2005JC003161.
Williams I. et al. (2015) Human, oceanographic and habitat drivers of central and western Pacific coral reef fish assemblages. PLoS 10: e0120516, doi: 10.1371/journal.pone.0120516.

 

Five million fish and counting!

By Kelvin Gorospe

After 15 years of surveying coral reef fishes across the Pacific, the Fish Team at the Pacific Islands Fisheries Science Center’s Coral Reef Ecosystem Division (CRED) has amassed one of the world’s largest datasets of reef fishes. This dataset has been instrumental in contributing to a better understanding of the health of coral reef ecosystems. The CRED team, currently conducting surveys in the Line Islands (a series of remote atolls and low islands in the central Pacific), recently surpassed a major benchmark: five million fish sized and counted!

A school of anthias (Pseudanthias bartlettorum) at Jarvis Island. Photo by Kelvin Gorospe

A school of anthias (Pseudanthias bartlettorum) at Jarvis Island. Photo by Kelvin Gorospe

It seems appropriate that the five millionth fish was a Pseudanthias bartelttorum, a tiny anthias, commonly numbering in the thousands within our surveys, and thus, the most numerically abundant fish we encounter. Even more appropriate is that the benchmark was reached at Jarvis Island, one of the Line Islands, and one of the most fish-abundant islands surveyed by CRED in the entire U.S. Pacific Islands region.

<em>Pseudanthias bartlettorum</em>. Photo by Kevin Lino

Pseudanthias bartlettorum. Photo by Kevin Lino

In commemoration of this benchmark, here is a conversation between the lucky anthias (PSBA) that so honorably received the distinction of being the five millionth fish and the fish team member, Kaylyn McCoy (KM), who counted it.

PSBA: When I first learned that I was the five millionth fish to be counted by the legendary CRED Fish Team, I had no idea they were anywhere close to surveying that many fishes. No offense, but who cares how many of us anthiases are living here on the reef? Is that seriously your job? Get a life.

KM: Well, Ms. Anthias… You are a “Ms.” right? I sized you as a 4cm Pseudanthias bartlettorum, so you’re probably a female, and I also saw that you’re part of a giant harem of anthiases, with just a few male anthiases. Don’t give me snarkiness just because your options are thin.

PSBA: Ok ok, sorry. But seriously, why count anthiases like me?

KM: Our job isn’t to just count anthiases. Our job is to monitor whole assemblages of reef fishes across the U.S. Pacific Islands, everything from the gray reef sharks that patrol around Jarvis Island to tiny anthiases like you. You’re all part of the reef fish community, which itself is part of the larger reef ecosystem that we monitor.

PSBA: Ok, but what is the point of surveying fish communities? What does that tell us?

KM: We are part of the Pacific Reef Assessment and Monitoring Program, so we are interested in monitoring long-term trends. By coming here to Jarvis Island every three years, we hope to get a better sense of how reef fish communities like yours are changing. It’s too soon to give you a definitive answer on fish community trends through time but we’re working on that…

PSBA: Wait! I knew I’ve seen you guys before! You were here three years ago and you’re pretty much the only people that we ever see around here. Well, I guess your job is pretty cool. It lets you dive in some of the most remote coral reefs in the world. But why do you care so much about diving where there are no other people?

KM: While we’re still working on building up our time series data, the immense spatial extent of our dataset also allows us to study how coral reefs around the Pacific vary across both human and environmental gradients. In other words, the reefs we study span the whole range of human impacts (from virtually no human impacts to reefs facing intense human pressures, like fishing and runoff caused by land-use and development) and changing environmental conditions (e.g., different temperatures, nutrients, carbonate chemistry, and wave energy). We study reefs in just about every condition imaginable, allowing us to tease apart the effects of environmental and human influences on reefs. Thanks to these data we now have a better understanding of the level of reef fish stocks we can expect around pristine reefs (recent paper by Fish Team published in PLOS ONE).

PSBA: So little anthiases like me really are important to you guys?

KM: Of course! We are a division of NOAA that specifically monitors coral reef ecosystems and you are part of the ecosystem. We not only monitor the fish populations, but the benthic communities, cryptic biodiversity, and oceanographic conditions around all of the reefs we study. All of this information is provided to fisheries management agencies in Hawai‘i, American Samoa, Guam, and the Mariana Islands, as well as our management partners at the Pacific Islands Regional Office, the Western Pacific Regional Fisheries Management Council, and the U.S. Fish and Wildlife Service (CRED monitoring publications). And the more data we collect, the better we will be able to report on how reefs are responding to local threats of human fishing as well as to global threats like ocean acidification and warming (NOAA Ocean Acidification Program), and more importantly, how management can help mitigate these impacts.

PSBA: Well, I’m glad the honor of the five millionth fish didn’t go to one of those big charismatic fish like a shark or a manta, or worse, some little clown fish, those guys are always stealing the limelight. And at least you didn’t mistake me for a Luzonichthys whitleyi or a Lepidozygus tapeinosoma. Those unoriginal posers are always mimicking us in our aggregations. Thanks Kaylyn and CRED for watching out for us and hope to see you in the water next time around!

Four Million Nine Hundred Ninety-Nine Thousand Nine Hundred and Ninety-Nine

By Kevin Lino

Five million… that number has a pleasant vastness to it. Five million of anything seems overwhelming. Try to picture five million fish. Start small and keep expanding. How would that look? Would they be one compact bait ball of iridescent shapes or a colorful patch work of reef fish schooling together? Well, it would take years to count that high and yet here we stand (or swim) just a few thousand fish away from reaching this landmark.

Image 1: A school of Big Eye Jack (Caranx sexfasciatus) trail behind a towed diver during a survey. Photo by Kevin Lino

Image 1: A school of Big Eye Jack (Caranx sexfasciatus) trail behind a towed diver during a survey. Photo by Kevin Lino

Image 2: Map of Study Region for Jarvis Island, Palmyra Atoll, and Kingman Reef.

Image 2: Map of Study Region for Jarvis Island, Palmyra Atoll, and Kingman Reef.

For the PIFSC Coral Reef Ecosystem Division (CRED) fish team, it has taken 15 years of dedicated hard work under the ocean’s surface to get to this point. This happens as our team collects visual census data on reef fish populations throughout the US-affiliated Pacific Islands. As part of the Pacific Reef Monitoring and Assessment Program (RAMP) these surveys support the National Coral Reef Monitoring Program (NCRMP). The goal of our research missions is to conduct integrated, consistent, and comparable monitoring of coral reefs across all regions while assessing and detecting change in natural resources. This is true around large inhabited islands like Tutuila in American Samoa, where we recently completed surveys, well as the tiny remote atolls in the Line Islands chain where we are currently working.

Image 3: A Scalloped Hammerhead Shark (Sphyrna lewini) cruises the bottom amongst schools of anthias at Jarvis Island. Photo by Kevin Lino

Image 3: A Scalloped Hammerhead Shark (Sphyrna lewini) cruises the bottom amongst schools of anthias at Jarvis Island. Photo by Kevin Lino

Image 4: Diver Marie Ferguson tows over a school of anthias at Jarvis Island. Photo by Kevin Lino

Image 4: Diver Marie Ferguson tows over a school of anthias at Jarvis Island. Photo by Kevin Lino

To date, the division has counted 4,890,980 fish throughout our survey areas using several methods. While it is hard to know which method will be used to count the five millionth fish, our primary surveys are conducted by stationary point count (SPC) divers who use a transect line along the seafloor counting every species in that area. Another team is towed behind a small boat counting the larger (over 50 cm) more mobile species– circumnavigating the islands and covering up to 15km each day. Odds are in the favor of the SPC diver to get the count with one of the smaller species that school in their many of thousands, quite likely a cute little 3 cm Chromis vanderbilti. Either way, it is a major landmark for our program and we look forward to seeing which lucky diver will count that fish.

Image 5: A small school of Chromis vanderbilti huddle near the seafloor. Photo by Kevin Lino

Image 5: A small school of Chromis vanderbilti huddle near the seafloor. Photo by Kevin Lino

Our first stop, Jarvis Island, is one of the most pristine reef environments I have ever seen. In the waters surrounding the mostly barren sands above, is a flourishing ecosystem partially driven by upwelling of cold and nutrient rich water from deeper in the ocean. In such productive waters, tens or even hundreds of large sharks, jacks, and manta rays are likely to appear alongside our divers the moment they enter the water. Just off the bottom, the real work begins as thousands of anthias, chromis, and other small species abound in the rugose benthos of healthy corals and algae. After six days at Jarvis, we voyage north toward the masses of fish at Palmyra Atoll and Kingman Reef for the last 12 days of surveys. Both of these remote areas are also quite unique, hosting an abundance of biodiversity to keep divers busy, while getting closer to that fortunate five millionth fish.

We are grateful for the nearly 80 scientists who have worked together to get us this far. One of whom has counted nearly 500,000 more fish than her next highest counterpart. In the last decade working with CRED, Paula Ayotte has rarely missed an opportunity to go to sea and spend hours underwater during these missions. If we had a Hall of Fame, she would be inducted unanimously for so many reasons: not only for counting nearly a million fish on her own, but also for making sure all other divers are trained, and mostly for being the most entertaining dive buddy you could hope for. It has been a pleasure working with her for that time and while it would be nice to be the diver to count the 5,000,000 fish… I’m hoping that Paula gets that count with a three meter manta ray at Jarvis.

Image 6: A Giant Manta (Manta birostris) curiously swims over a diver during a survey. Photo by Kevin Lino

Image 6: A Giant Manta (Manta birostris) curiously swims over a diver during a survey. Photo by Kevin Lino

Image 7: Diver Paula Ayotte amongst a healthy school of Whitebar Surgeonfish (Acanthurus leucopareius) and Convict Tang (A. triostegus) while conducting an SPC dive.

Image 7: Diver Paula Ayotte amongst a healthy school of Whitebar Surgeonfish (Acanthurus leucopareius) and Convict Tang (A. triostegus) while conducting an SPC dive.

Meaningful monitoring

By Adel Heenan and Ivor Williams

The fish team of the PIFSC Coral Reef Ecosystem Division (CRED) recently published a report summarizing its ecological monitoring activities in 2012–2013. This publication is the first in a new series of annual status reports from the surveys of coral reef fishes and benthic habitats conducted as part of the NOAA Pacific Reef Assessment and Monitoring Program (Pacific RAMP). Its release presents a good opportunity to outline our team’s new communication strategy and to highlight recent efforts to institutionalize more effective monitoring of coral reef fishes in the U.S. Pacific.

To download the ecological monitoring report for 2012–2013, click here.

Why monitor?

Broadly, the purpose of long-term ecological monitoring is to assess the condition of natural resources and detect changes through time. Pacific RAMP includes the following specific objectives:

      • Collecting data and generating information on and documenting the status and trends of coral reef ecosystems, including primary components of the fish and benthic communities and key environmental drivers at U.S.-affiliated jurisdictions in the Pacific;
      • Generating data suitable for assessment of changes in coral reef ecosystems in response to human, oceanographic, or environmental stressors; and
      • Generating data to better evaluate the effectiveness of resource management strategies and policies.

Therefore, the value of data collected through Pacific RAMP depends on both how well it documents spatial patterns and changes across a large geographic area of the Pacific and, most important, how it informs management decisions to sustain coral reef resources. As part of NOAA’s National Coral Reef Monitoring Plan, the Pacific RAMP monitors to detect change in environmental conditions and ecosystem responses on island and regional scales because it is important for assessment of global stressors, such as ocean warming and acidification. The islands monitored span a wide range of potential human impact—from large population centers, such as Oahu, Maui, and Guam, to some of the most remote and pristine coral reefs in the world (e.g., Rose Atoll, the Pacific Remote Islands Marine National Monument, and the Northwestern Hawaiian Islands). As such, CRED data are extremely valuable in the context of a conundrum that sits at the heart of fisheries management: what were coral reefs like in the absence of human influence? More specifically, to know how many fishes were there in the absence of fishing (a concept that is technically referred to as pristine fish abundance) is one of the essential reference points from which maximum sustainable harvest is calculated and, thus, fills a basic information need to support fisheries management decisions.

The large spatial scale at which CRED operates does make it more difficult to assess local or island-scale impacts. In general, many questions that require repeated visits throughout the course of a year or more intensive local sampling are best handled by the jurisdictions’ own monitoring programs. Nonetheless, with a few possible exceptions, the sampling area across which our standardized methods are applied (~40 U.S. Pacific islands and atolls) is globally unique and the data we collect provide an important context for status and trends observed at local levels. For the full potential of Pacific RAMP to be realized, however, CRED’s field surveys need to align with a number of equally important components that make long-term monitoring effective.

What makes ecological monitoring effective?

What constitutes effective monitoring is clearly context specific. It depends on, for example, the variables of interest (e.g., physical vs. biological, species-specific or community-level estimates) and the target quantitative objectives. Within the CRED fish team, we have implemented the following components to make our long-term monitoring efforts more relevant and reliable. To clarify our field sampling method and to establish an institutional memory, the fish team’s standard operation procedure is publicly available (click here to download). The standard operating procedure is currently being revised to include our statistical sampling design.

Before fieldwork begins, the CRED fish team conducts regular observer training focused on fish identification and on fish-size estimation. Once in the field, we continually monitor diver performance in terms of biomass and species richness estimates relative to other divers (Fig. 1). We have a standardized framework centered on transparent, reproducible reporting that has greatly increased our ability for timely and fastidious communication of our data. To make our data meaningful, however, we have to turn it into information. To do so, we have devised a tiered communication strategy.

Figure 1. This diagram illustrates the training, data collection, data processing, and reporting phases the fish and benthic surveys conducted by the fish team for the Pacific Reef Assessment and Monitoring Program.

Figure 1. This diagram illustrates the training, data collection, data processing, and reporting phases the fish and benthic surveys conducted by the fish team for the Pacific Reef Assessment and Monitoring Program.

 

Our new communication strategy for information products

The communication strategy of the CRED fish team has four levels, each of increasing complexity and detail. At the first level, immediately following each cruise leg, which typically cover a region or archipelago, we produce a monitoring brief that outlines our sampling effort and an overview summary of the new data (click herefor access to monitoring briefs). Second, we are committed to producing an annual status report within three months of the new calendar year. This status report presents the new site-level data collected (Fig. 2), sets the regions surveyed in the context of the wider Pacific areas that CRED surveys (Fig. 3), and reports on our diver performance results. The third and fourth tiers provide more in-depth analyses for specific projects. To illustrate, a technical report came from the additional surveys performed around Guam in 2011, surveys that allowed for assessment of the efficacy of marine protected areas (click hereto download NOAA Technical Memorandum NMFS-PIFSC-33).

Figure 2. An example of the site-level data presented in the annual data report, this figure presents the following survey data from sites at Jarvis Island in 2010 and 2012 (top left) identified by depth strata, (top right) total fish biomass recorded at each site per year, (bottom left) hard coral cover (%) assessed by rapid visual assessment, and (bottom right) benthic substrate ratio (hard corals and encrusting algae to turf algae and macroalgae). The substrate ratio indicates the balance between the benthic components that contribute to reef accretion (corals and crustose coralline algae) and the fleshy macroalgae and turf algae that compete for space on the reef.

Figure 2. An example of the site-level data presented in the annual data report, this figure presents the following survey data from sites at Jarvis Island in 2010 and 2012 (top left) identified by depth strata, (top right) total fish biomass recorded at each site per year, (bottom left) hard coral cover (%) assessed by rapid visual assessment, and (bottom right) benthic substrate ratio (hard corals and encrusting algae to turf algae and macroalgae). The substrate ratio indicates the balance between the benthic components that contribute to reef accretion (corals and crustose coralline algae) and the fleshy macroalgae and turf algae that compete for space on the reef.

Figure 3. An example of the Pacific-wide data presented in the annual status report, this figure presents mean fish biomass per size class per U.S. Pacific reef area. Mean fish biomass (± standard error) per size class (0–20, 20–50, and >50 cm in total length [TL]) per reef area, pooled across survey years (2009–2013). Islands are ordered within region by latitude. NWHI=Northwestern Hawaiian Islands, MHI=main Hawaiian Islands, N.Mariana=northern Mariana Archipelago, S.Mariana=southern Mariana Archipelago, PRIA=Pacific Remote Island Areas, and Samoa=American Samoa.

Figure 3. An example of the Pacific-wide data presented in the annual status report, this figure presents mean fish biomass per size class per U.S. Pacific reef area. Mean fish biomass (± standard error) per size class (0–20, 20–50, and >50 cm in total length [TL]) per reef area, pooled across survey years (2009–2013). Islands are ordered within region by latitude. NWHI=Northwestern Hawaiian Islands, MHI=main Hawaiian Islands, N.Mariana=northern Mariana Archipelago, S.Mariana=southern Mariana Archipelago, PRIA=Pacific Remote Island Areas, and Samoa=American Samoa.

We welcome comments on how to improve the utility of our data and information products. Comments or suggestions on any of the above content can be submitted to nmfs.pic.credinfo@noaa.gov with the subject line of “For the Attention of the CRED Fish Team Lead.”

Again, to access the 112-page annual status report for 2012–2013, click here. Here’s the full reference for this report:

Heenan A, Ayotte P, Gray A, Lino K, McCoy K, Zamzow J, Williams I. 2014.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. Pacific Islands Fisheries Science Center, PIFSC Data Report, DR-14-003, 112 p.