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.

 

A Fish That Shapes The Reef

By Andrew E. Gray

Every three years, scientists from NOAA’s Coral Reef Ecosystem Program (CREP) visit Wake Atoll to survey corals, assess the fish populations, and collect oceanographic data for a long-term monitoring effort—the Pacific Reef Assessment and Monitoring Program (Pacific RAMP). Wake Atoll has clear water, healthy coral reefs, and is managed and conserved as part of the expansive U.S. Pacific Remote Islands Marine National Monument. It has a healthy reef fish community with plentiful sharks, jacks, and groupers. As a fish research diver, it’s my kind of paradise. Sitting in the middle of the subtropical North Pacific Ocean, 1,500 miles east of Guam and about 2,300 miles southwest of Honolulu, it may be the most remote place I’ve ever been. But for me, and a few other scientists lucky enough to visit the island, there is one thing that makes Wake a special place: Bolbometopon muricatm, the Bumphead parrotfish.

Bumphead parrotfish

Bumphead parrotfish (Bolbometopon muricatm) at Wake Atoll (Photo: NOAA Fisheries/Andrew E. Gray)

Bumphead parrotfish are an incredible and unique reef fish, differing from other parrotfish by their large size, appearance, diet, and by their ecological impact on coral reef ecosystems. There are a number of other parrotfish that sport a bump on their head, and these may be mistaken for a Bumphead parrotfish—that is until you actually see one. Bumpheads have a presence like no other fish on the reef and when they are around I can’t take my eyes off of them. The first thing I notice is their sheer size: growing to 4.2 feet long and up to a 100 pounds (that’s 130 cm and 46 kg for you scientists). Bumpheads are the world’s largest parrotfish and among the largest of all reef fish. When I get a little closer, I can’t help but focus on their incredible beaks. On coral reefs, all parrotfish species are tasked with the important job of keeping algae from overgrowing reef-building corals.

Corals chomped

Bumphead parrotfish chomp corals and help maintain the health and diversity of the reef ecosystem, Wake Atoll (Photo: NOAA Fisheries/Andrew E. Gray)

Parrotfish bite and scrape algae off of rocks and dead corals with their parrot-like beaks; grind the inedible calcium carbonate (reef material made mostly of coral skeletons) which is excreted as sand back onto the reef. Larger parrotfish species can take small chunks out of the reef, removing algae and the occasional piece of coral. Bumphead parrotfish are unique in that they are continuously crunching large bites out of the reef, about half of it from live coral. In fact, that’s what they do most of the day. Bite the reef. Excrete sand. Repeat. Over the course of a year a single fish can remove over 5 tons of calcium carbonate from the reef! But by selectively eating fast growing coral species over slower growing species, they help maintain a more diverse coral reef ecosystem. Also, by munching down tons of dead corals every year each fish makes room for young corals to settle, grow and build up the reef. This means breaking down “dead reef” into sand rather than it breaking off in a storm and damaging other parts of the reef. And since Bumpheads often travel in groups, sometimes numbering into hundreds and traveling multiple kilometers in a day, this species can have quite an impact on the reef ecosystem. Bumphead parrotfish literally shape the reef.

Bumphead

Large bump on the head of a Bumphead parrotfish (Photo: NOAA Fisheries/Andrew E. Gray)

Then, of course, there is the fish’s namesake, its bump. All Bumphead parrotfish sport a large protrusion on their forehead which is similar in function to a pair of horns on a bighorn sheep. The largest males have the biggest bumps and will occasionally use them as battering rams around spawning time, smashing headfirst into rivals in an attempt to show their dominance and retain territorial and breeding rights. This incredible behavior was observed by CREP scientists in 2009 and first documented and filmed by researchers at Wake in 2011. During these mating events, the parrotfish gather or aggregate around a spawning site and can number into the hundreds, an uncommon site anywhere in the world and one that I hope to see sometime at Wake.

Historically, Bumphead parrotfish were plentiful throughout much of the Western Pacific, Indian Ocean, and Red Sea. In recent decades, fishing led to sharp declines in abundance and they are now only common in protected or very remote areas. Bumpheads have a few traits that make them particularly vulnerable to overfishing, which has led to local disappearances in many parts of their range. Bumphead parrotfish can live to be 40 years old; they do not reach sexual maturity until 5-8 years old and likely have low natural mortality as adults so there is not high natural turnover in the population. However, most detrimental to their survival in a human-dominated world is their aggregating behavior and preference for shallow water. Groups of Bumpheads could be easily netted, as they feed during the day, and at night sleeping parrotfish are easy targets for spear fishermen. With the introduction of scuba gear in the 1960’s and 1970’s there was a steep decline in Bumphead abundances as entire schools could be removed in a single night while they slept. Juvenile Bumpheads are also hard to find or study throughout much of their range and raises concerns that some adult populations are too far from juvenile habitats. This distance prevents new youngsters from entering the population to replace adults that have been caught. In areas where juveniles can be commonly found, such as Papua New Guinea and the Solomon Islands, they are associated with mangrove, rubble, and sheltered lagoon habitats. And this is why Wake Atoll may be such a hotbed of Bumpheads.

Reef at Wake Atoll

Coral reef at Wake Atoll in the Pacific Remote Islands Marine National Monument (Photo: NOAA Fisheries/James Morioka)

In addition to having a sizable healthy coral reef around the island, Wake Atoll has an expansive, sheltered lagoon. This may be the perfect habitat for the juvenile parrotfish and allows Wake to have a healthy, self-supplying population of Bumpheads. And since Wake is protected from fishing, it may be as close to a pristine home as the Bumphead parrotfish are going to encounter in today’s world. Wake actually has the highest concentration of Bumphead parrotfish in U.S. waters and possibly the world (although certain areas of the Great Barrier Reef in Australia also have very healthy adult populations). During my time at Wake Atoll, I had a number of chances to see them, from loose groups of just a few individuals, to a school of thirteen.

School too

School of Bumphead parrotfish at Wake Atoll (Photo: NOAA Fisheries/Andrew E. Gray)

As I write this, the NOAA Ship Hi‘ialakai heads west to Guam, our next survey site where I’ll be spending 8 days surveying reef fish. Bumpheads were once thought to be extinct around Guam due to overfishing, but there have been a few sightings by CREP and partners in the past few years, of both adults and juveniles. So while my expectations of encountering these giant bulbous-headed, coral-chomping fish are low, I sure hope I do, given how important they are to the natural function of coral reef ecosystems.

References
  1. Bellwood, D., & Choat, J. (2011). Dangerous demographics: the lack of juvenile humphead parrotfishes Bolbometopon muricatum on the Great Barrier Reef. Coral Reefs, 30(2), 549-554.
  2. Bellwood, D. R., Hoey, A. S., & Choat, J. H. (2003). Limited functional redundancy in high diversity systems: resilience and ecosystem function on coral reefs. Ecology Letters, 6(4), 281-285.
  3. Bellwood, D. R., Hoey, A. S., & Hughes, T. P. (2011). Human activity selectively impacts the ecosystem roles of parrotfishes on coral reefs. Proceedings of the Royal Society B: Biological Sciences. doi: 10.1098/rspb.2011.1906
  4. Donaldson, T. J., & Dulvy, N. K. (2004). Threatened fishes of the world: Bolbometopon muricatum (Valenciennes 1840)(Scaridae). Environmental Biology of Fishes, 70(4), 373-373.
  5. Green, A. L., & Bellwood, D. R. (2009). Monitoring functional groups of herbivorous reef fishes as indicators of coral reef resilience: a practical guide for coral reef managers in the Asia Pacific Region: IUCN.
  6. Kobayashi, D., Friedlander, A., Grimes, C., Nichols, R., & Zgliczynski, B. (2011). Bumphead parrotfish (Bolbometopon muricatum) status review. NOAA Technical Memorandum NMFS-PIFSC-26. NOAA.
  7. Muñoz, R. C., Zgliczynski, B. J., Laughlin, J. L., & Teer, B. Z. (2012). Extraordinary Aggressive Behavior from the Giant Coral Reef Fish, Bolbometopon muricatum, in a Remote Marine Reserve. PLoS One, 7(6), e38120. doi: 10.1371/journal.pone.0038120
  8. Munoz, R. C., Zgliczynski, B. J., Teer, B. Z., & Laughlin, J. L. (2014). Spawning aggregation behavior and reproductive ecology of the giant bumphead parrotfish, Bolbometopon muricatum, in a remote marine reserve. PeerJ, 2, e681.
  9. Sundberg, M., Kobayashi, D., Kahng, S., Karl, S., & Zamzow, J. (2015). The Search for Juvenile Bumphead Parrotfish (Bolbometopon muricatum) in the Lagoon at Wake Island.

Creating a “Community” for the Pacific Remote Islands Marine National Monument

by Hoku Johnson

How do managers effectively spread the word about the natural splendors of a large, extremely remote place?  Who is the “community” of people that will provide advice to NOAA and U.S. Fish and Wildlife Service managers on development of a management plan for this place?  Why should anyone care about the Pacific Remote Islands Marine National Monument (PRIMNM)?

Wading toward the small boats after a day of manager-expert discussions.

Wading toward the small boats after a day of manager-expert discussions.

Sean Russell, Susan White, Callum Roberts and Leanne Fernandes discuss marine conservation while wading through the water at Palmyra Atoll.

Sean Russell, Susan White, Callum Roberts and Leanne Fernandes discuss marine conservation while wading through the water at Palmyra Atoll.

Last week, a small group of four experts and four marine managers set out to discuss these questions on Palmyra Atoll, a National Wildlife Refuge located within the PRIMNM, approximately 1,100 miles south of Honolulu.  Their main task: develop a community steering committee comprised of stakeholders that will be able to provide advice to managers on everything ranging from prioritizing research to figuring out creative ways to bring the wonders of these remote protected atolls and islands to the world.

Before diving into discussion, the group had the opportunity to dive into the ocean surrounding Palmyra Atoll to connect with the place and experience a kaleidoscope of corals, fishes, sharks, and turtles. The diving and snorkeling was amazing and reminded the group of why a community of advocates is important to such a remote area.

The group discusses building a community steering committee for the Pacific Remote Islands Marine National Monument.

The group discusses building a community steering committee for the Pacific Remote Islands Marine National Monument.

Once everyone dried off, the group–consisting of Dr. Callum Roberts, Dr. Leanne Fernandes, Mr. Sean Russell, Ms. Hoku Johnson, Mr. Matthew Brown, Ms. Samantha Brooke, Ms. Heidi Hirsh, Ms. Susan White, and facilitator Ms. Deanna Spooner–delved into topics including: sorting through relevant stakeholder groups, discussing the Presidential Proclamations that established and expanded PRIMNM, different ways a community steering committee might be convened, and priority topics this group would discuss in the future.

Juvenile coconut crab

Juvenile coconut crab

By the end of the week, the group finalized a draft framework for a community steering committee (dubbed the “PRIMNM CSC”) that will be fleshed out further by the NOAA and Fish and Wildlife Service managers over the next few months. The group celebrated their achievement by participating in a Palmyra Atoll Research Consortium beach barbecue and an evening “crab walk” looking for numerous species of crabs that live on Palmyra Atoll.

Refuge Manager Stefan Kropidlowski talks with the group about the native Pisonia tree behind him.

Refuge Manager Stefan Kropidlowski talks with the group about the native Pisonia tree behind him.

Scientists complete coral reef ecosystem monitoring work around the U.S. Phoenix Islands

By Kelvin Gorospe

The Pacific Islands Fisheries Science Center’s (PIFSC) Coral Reef Ecosystem Division (CRED) recently completed the Phoenix Islands portion of their Pacific Reef Assessment and Monitoring Program (Pacific RAMP) research cruise. The areas they surveyed included: Johnston Atoll, Howland Island, and Baker Island. All three islands are part of the Pacific Remote Islands Marine National Monument, which is co-managed by NOAA and the U.S. Fish and Wildlife Service (USFWS), as well as the National Wildlife Refuge System administered by the USFWS. These areas are among the most remote locations under U.S. jurisdiction and offer a unique opportunity to study and better understand coral reef ecosystems removed from direct human impacts.

Figure 1: Launching and recovering teams of scientists from NOAA R/V Hi‘ialakai. Photo credit Kelvin Gorospe.

Figure 1: Launching and recovering teams of scientists from NOAA R/V Hi‘ialakai. Photo credit Kelvin Gorospe.

Figure 2: Group photo of scientific divers on the fantail of the ship. Photo credit Jim Bostick.

Figure 2: Group photo of scientific divers on the fantail of the ship. Photo credit Jim Bostick.

During the expedition, small boats were launched from NOAA ship Hi‘ialakai carrying teams of scientists to survey reef fishes, benthic and microbial communities, and study the effects of ocean acidification and warming on reef ecosystems (Fig 1). A total of 17 scientific divers, one data manager, and two terrestrial biologists participated in operations (Fig 2). For the U.S. Phoenix Islands portion of the cruise, fish data are highlighted below. Blog posts from the upcoming legs of this 103-day research expedition will highlight information from other reef assessment surveys.

Over the course of 13 diving days, the fish team surveyed a total of 102 rapid ecological assessment (REA) sites (31 at Johnston Atoll, 35 at Howland Island, and 36 at Baker Island). The team used a stratified random survey design, whereby the reefs around each island are divided into three depth zones (0-6 m; 6-18 m; and 18-30 m) and the total number of sites surveyed in each depth zone is proportionate to the total amount of reef area found in that depth zone. Site locations are then spatially randomized around the island. Click here for more details on the methodology of fish REA surveys.

Figure 3: Total fish biomass (all species) at all sites surveyed around Howland Island.

Figure 3: Total fish biomass (all species) at all sites surveyed around Howland Island.

Figure 4: Total fish biomass (all species) at all sites surveyed around Baker Island.

Figure 4: Total fish biomass (all species) at all sites surveyed around Baker Island.

At Howland and Baker Islands, the subsurface eastward-flowing Equatorial Undercurrent encounters the submerged portions of these undersea mountains to create areas of intense upwelling of nutrient-rich waters that help sustain high biomasses of reef fishes. This is clearly shown in the bubble plots above (Fig 3 and Fig 4), depicting high levels of fish biomass around both islands. Each circle on the graph is centered on a dive site.

Figure 5: Manta rays swimming through a fish survey at Howland Island. Photo credit Louise Giuseffi.

Figure 5: Manta rays swimming through a fish survey at Howland Island. Photo credit Louise Giuseffi.

Figure 6: Fish REA diver collecting data on fish species ID, sizes, and abundance at Johnston Atoll. Photo credit Louise Giuseffi.

Figure 6: Fish REA diver collecting data on fish species ID, sizes, and abundance at Johnston Atoll. Photo credit Louise Giuseffi.

Among other large-bodied species, schools of manta rays were frequently reported around both Howland and Baker Islands (Fig 5). At each site, two fish divers collected replicate data on the sizes and numbers of fish species that swam through their survey area over the course of five minutes (Fig 6). The size of the circle is proportionate to the calculated total biomass of fish (g per m2) at each site. These graphs demonstrate the high reef fish biomasses in these upwelling areas of the Pacific Remote Islands Marine National Monument.

Figure 7: Total fish biomass (all species) at all sites surveyed around Johnston Atoll.

Figure 7: Total fish biomass (all species) at all sites surveyed around Johnston Atoll.

In contrast, Johnston Atoll, which doesn’t experience this strong upwelling of nutrients (Fig 7), sustains lower levels of reef fish biomass than Howland and Baker. However, its importance is highlighted by the fact that it is known to be an important genetic stepping stone between the central Pacific and the Hawaiian Islands, maintaining evolutionary connectivity between these areas. During our time at Johnston on this cruise, CRED scientists spotted three coral species (Acropora speciosa, Acropora retusa, and Pavona diffluens) recently listed as threatened under the Endangered Species Act.

In addition, CRED scientists reported frequent sightings of overturned Acropora table corals and observed that much of the coral on the northwest side of the atoll experienced recent damage, likely as a result of the large ocean swell from the northwest that came through as we were leaving Oahu at the end of January. Protection of these areas from the degrading effects of fishing and extraction is important to ensuring that the reef can recover from natural environmental impacts such as these large ocean swell events.

The CRED team will remain at sea until May 3, 2015, continuing to conduct coral reef ecosystem monitoring surveys throughout American Samoa (Tutuila, Ofu, Olosega, Ta‘u, and Swains Islands and Rose Atoll) as well as the U.S. Line Islands (Jarvis Island, Palmyra Atoll, and Kingman Reef). Stay tuned for more updates from the field.

Reef monitoring at Wake Island: preliminary results from fish surveys

By Dione Swanson

After departing Honolulu on March 5, the NOAA Ship Hi’ialakai arrived at Wake Island on March 14. It was the first stop for PIFSC cruise HA-14-01, a Pacific Reef Assessment and Monitoring Program (Pacific RAMP) expedition that also recently visited Guam and is currently focused on the southern islands of the Commonwealth of the Northern Marianas Islands. At Wake Island, staff members of the PIFSC Coral Reef Ecosystem Division (CRED) and partners conducted surveys of reef fish assemblages, coral populations, and benthic communities as well as deployed instruments and collected water samples to monitor effects of climate change and ocean acidification on coral reef ecosystems.

Our first 2 planned operational days on Wake Island were canceled because of poor weather conditions (strong winds and high seas). Relatively good weather returned by March 16, and we then were able to complete 4.5 days of small-boat operations before leaving for Guam on March 20. Over the course of our time at Wake Island, scientists accomplished the following field activities during a combined 229 dives: reef fish surveys at 45 Rapid Ecological Assessment (REA) sites; benthic surveys at 20 REA sites; collection of 12 water samples and 1 benthic sample for analysis of microbial communities; retrieval of 7 subsurface temperature recorders (STRs), 6 autonomous reef monitoring structures (ARMs), 15 calcification accretion units (CAUs), and 1 sea-surface temperature (SST) buoy; installation of 4 National Coral Reef Monitoring Plan climate stations—each of which includes 3 ARMs, 5 CAUs, 5 bioerosion monitoring units, and 3 STRs; and collection of 20 water samples for analysis of dissolved inorganic carbon; and completion of 11 shallow-water conductivity, temperature, and depth (CTD) casts.

Highlights of our research dives at Wake Island included incredible water visibility (>45 m), high coral cover that consisted of abundant large colonies with low partial mortality, overall low prevalence of coral disease and bleaching, and large patches of soft corals. There were only a few sightings of bumphead parrotfish (Bolbometopon muricatum) and Napoleon wrasse (Cheilinus undulatus).

Preliminary results from the surveys of reef fishes conducted by scuba divers at Wake Island (depth range: 0–30 m) during this cruise are provided in the below fish monitoring brief, which was issued on March 25 as PIFSC Data Report DR-14-007 (click here, to download a PDF file of this report). Wake Island is 1 of 7 islands, atolls, and reefs that make up the Pacific Remote Island Areas and, under the jurisdiction of the United States, are protected as the Pacific Remote Islands Marine National Monument.

Pacific Reef Assessment and Monitoring Program
Fish monitoring brief: Pacific Remote Island Areas 2014

By Adel Heenan

About this summary brief

The purpose of this document is to outline the most recent survey efforts conducted by the Coral Reef Ecosystem Division (CRED) of the NOAA Pacific Islands Fisheries Science Center as part of the long-term monitoring program known as the Pacific Reef Assessment and Monitoring Program (Pacific RAMP). More detailed survey results will be available in a forthcoming annual status report.

Sampling effort

  • Ecological monitoring took place in the Pacific Remote Island Areas from March 16 2014 to March20 2014.
  • Data were collected at 45 sites. Surveys were conducted at Wake Island.
  • At each site, the fish assemblage was surveyed by underwater visual census and the benthic community was assessed.

Overview of data collected

Primary consumers include herbivores (which eat plants) and detritivores (which bottom feed on detritus), and secondary consumers are largely omnivores (which mostly eat a variety of fishes and invertebrates) and invertivores (which eat invertebrates).

Figure 1. Mean total fish biomass at sites surveyed.

Figure 1. Mean total fish biomass at sites surveyed.

 

Figure 2. Mean hard coral cover at sites surveyed.

Figure 2. Mean hard coral cover at sites surveyed.

Figure 3. Mean consumer group fish biomass (± standard error). Primary consumers are herbivores and detritivores, and secondary consumers are omnivores and invertivores.

Figure 3. Mean consumer group fish biomass (± standard error). Primary consumers are herbivores and detritivores, and secondary consumers are omnivores and invertivores.

Figure 4. Mean fish biomass per size class (± standard error). Fish measured by total length (TL) in centimeters (cm).

Figure 4. Mean fish biomass per size class (± standard error). Fish measured by total length (TL) in centimeters (cm).

 

Spatial sample design

Survey site locations are randomly selected using a depth-stratified design. During cruise planning and the cruise itself, logistic and weather conditions factor into the allocation of monitoring effort around sectors of each island or atoll. The geographic coordinates of sample sites are then randomly drawn from a map of the area of target habitat per study area. The target habitat is hard-bottom reef, the study area is typically an island or atoll, or in the case of larger islands, sectors per island, and the depth strata are shallow (0–6 m), mid (6–18 m), and deep (18–30 m).

Sampling methods

A pair of divers surveys the fish assemblage at each site using a stationary-point-count method (Fig. 5). Each diver identifies, enumerates, and estimates the total length of fishes within a visually estimated 15-m-diameter cylinder with the diver stationed in the center.

These data are used to calculate fish biomass per unit area (g m-2) for each species. Mean biomass estimates per island are calculated by weighting averages by the area per strata. Island-scale estimates presented here represent only the areas surveyed during this cruise. For gaps or areas not surveyed during this cruise, data from this and other survey efforts will generally be pooled to improve island-scale estimates.

Each diver also conducts a rapid visual assessment of reef composition, by estimating the percentage cover of major benthic functional groups (encrusting algae, fleshy macroalgae, hard corals, turf algae and soft corals) in each cylinder. Divers also estimate the complexity of the surface of the reef structure, and they take photos along a transect at each site that are archived to allow for future analysis.

Figure 5. Method used to monitor fish assemblage and benthic communities at the Rapid Ecological Assessment (REA) sites.

Figure 5. Method used to monitor fish assemblage and benthic communities at the Rapid Ecological Assessment (REA) sites.

About the monitoring program

Pacific RAMP forms a key part of the National Coral Reef Monitoring Program of NOAA’s Coral Reef Conservation Program (CRCP), providing integrated, consistent, and comparable data across U.S. Pacific islands and atolls. CRCP monitoring efforts have these aims:

  • Document the status of reef species of ecological and economic importance
  • Track and assess changes in reef communities in response to environmental stressors or human activities
  • Evaluate the effectiveness of specific management strategies and identify actions for future and adaptive responses

In addition to the fish community surveys outlined here, Pacific RAMP efforts include interdisciplinary monitoring of oceanographic conditions, coral reef habitat assessments and mapping. Most data are available upon request.

For more information

Coral Reef Conservation Program: http://coralreef.noaa.gov

Pacific Islands Fisheries Science Center: http://www.pifsc.noaa.gov/

CRED publications: http://www.pifsc.noaa.gov/pubs/credpub.php

CRED fish team: http://www.pifsc.noaa.gov/cred/fish.php

Fish team lead and fish survey data requests: ivor.williams@noaa.gov