Guam Long-term Coral Reef Monitoring Program Reef Fish Surveys since 2010

The Government of Guam's Long-term Coral Reef Monitoring Program (GLTMP), coordinated through the Guam Coastal Management Program until October 2013 and now coordinated through the University of Guam Marine Laboratory, involves the collection of data for a suite of coral reef ecosystem health parameters at several high priority reef sites around the island of Guam. The program currently utilizes a split-panel sampling approach, whereby a mix of permanent and non-permanent sampling stations (one sampling station = one transect) are visited within each site. The monitoring sites were selected by an advisory body comprised of reef managers, researchers, and technicians. The locations of the sampling stations within each site are generated randomly using GIS software. Various coral reef surveys are carried out on an annual basis along the seaward slope between 7 and 15 m depth in the Tumon Bay Marine Preserve and East Agana Bay sites. Surveys are carried out less regularly along the seaward slope between 7 and 15 m depth in the Piti Bomb Holes Marine Preserve, the Achang Reef Flat Marine Preserve, the eastern side of the Cocos Barrier Reef (Cocos-East), and along the seaward slope (5–8 m) in Fouha Bay. Surveys were also carried at along reef margin (1–2 m) and slope (2–15 m) of Western Shoals, in Apra Harbor, in 2011. The surveys, which are conducted by University of Guam Marine Lab and NOAA PIRO biologists currently include benthic photo transects, quadrat surveys for coral colony size and condition, stationary point count fish surveys, macroinvertebrate belt transects, and chain-length rugosity surveys. These surveys have been conducted at the Tumon and East Agana sites since 2010 and the Piti site since 2012. Data collection for the Achang and Cocos-East sites has occurred in 2014, 2018, and 2021, and at the Fouha Bay site in 2015, 2019, and 2021. Baseline data is available for the Western Shoals site from 2011 but this site has not been re-visited since its establishment due to shifting management priorities.

Fish are a culturally and economically valuable resource for the island of Guam (van Buekering et al., 2007). In recognition of the high value of this resource, reef fish surveys are a key component of the Guam Long-term Coral Reef Monitoring Program. Reef fish assessment surveys have been conducted at high priority reef sites around Guam since August 2010. The monitoring team uses a Stationary Point Count Method, adapted from Ault et al. (2006) and NOAA Fisheries, Coral Reef Ecosystem Division (Williams et al., 2011), to conduct the reef fish surveys. These monitoring data on reef fish communities provide results on fish density, biomass, and diversity; allow for exploration of community structure by functional group and size structure; and can be used to detect changes in fish communities over time.

IMPORTANT NOTE: Changes have been made to the fish SPC survey methodology since its first deployment in 2010. These changes, which are documented in the Data Quality and Lineage sections of this metadata record, must be considered in order to properly analyze these data. Also, please note that the results of a 2020 analysis of the fish SPC data conducted by Dr. Peter Houk of the University of Guam Marine Laboratory indicated that data collected in 2010 and 2011 by one observer, and data collected by another observer at single site in 2015, did not meet quality assurance standards. In response to the results of this analysis observations recorded by these two observers are not included in the dataset submitted to NCEI. However, these data can be made available upon request. More information regarding Dr. Houk's analysis can be found in the Data Quality section of the metadata record.

The reef fish data are collected as part of the Guam Long-term Coral Reef Monitoring Program, which documents a number of important parameters related to ecosystem health; these parameters are grouped into three categories: water quality, benthic habitat, and associated biological communities. Many of these parameters are indicators of stressors, and significant changes in these parameters will likely raise concern and possibly trigger management actions. Data collected for these indicators provide important information about the resilience of high priority reef areas around Guam. Monitoring these parameters allows resource managers to evaluate the effectiveness of specific management strategies, and inform the development of new management actions.

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The following FGDC sections are not currently supported in InPort, but were preserved and will be included in the FGDC export:

- Spatial Reference Information (FGDC:spref),

Reef fish SPC data have been collected at permanent and non-permanent sampling stations within multiple monitoring sites since 2010, including:

Tumon Bay: 2010 (belt: 10 perm, 10 non-perm; SPC: 10 perm, 10 non-perm); 2012 (2 perm, 2 non-perm); 2014 (0 perm, 5 non-perm); 2015 (12 perm, 10 non-perm); 2017 (12 perm, 10 non-perm); 2019 (12 perm, 10 non-perm); 2020 (12 perm, 10 non-perm); 2021 (12 perm, 10 non-perm)

East Agana Bay: 2010 (10 perm, 10 non-perm); 2015 (10 perm, 10 non-perm); 2017 (10 perm, non-perm surveys); 2019 (10 perm, 6 non-perm); 2020 (10 perm, 10 non-perm); 2021 (10 perm, 10 non-perm)

Western Shoals: 2011 (belt: 11 perm, 13 non-perm; SPC: 2 perm, 2 non-perm)

Piti Bay: 2012 (6 perm, 8 non-perm); 2014 (10 perm, 2 non-perm); 2017-2018 (10 perm, 10 non-perm); 2020 (10 perm, 10 non-perm)

Achang: 2014 (8 perm, 3 non-perm); 2018 (10 perm, 10 non-perm); 2021 (10 perm, 10 non-perm)

Cocos-East: 2014 (3 perm, 4 non-perm); 2018 (no fish data collected); 2021 (10 perm, 10 non-perm)

Fouha Bay: 2015 (10 perm); 2019 (10 perm); 2021 (10 perm)

Data entry and quality control are complete for surveys conducted through 2020; the entry and quality control of data collected in 2021 has not yet been completed. Please note that data collected by two observers did not meet the program's data standards, based on an in-depth examination of inter-observer bias carried out with the support of Dr. Peter Houk of the University of Guam Marine Laboratory. These observations, which include most of the observations from 2010, half of the observations from 2011, and a portion of the observations from the Tumon site in 2015, will not be submitted to NCEI for archival, but can be made available upon request.

Raw survey data includes metadata for each survey (where, when, who, area); site characteristics (depth, reef type, habitat, exposure); individual reef fish observations identified to the lowest taxonomic level possible (usually species) including size, count, and observation type; and parameters needed to calculate biomass and density.

While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. The Guam Coastal Management Program makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

Tumon Bay

East Agana Bay

Western Shoals

Piti (Tepungan) Bay

Achang

Cocos-East

Fouha Bay

Not applicable

Not applicable

Data can be accessed online via the NOAA National Centers for Environmental Information (NCEI) Ocean Archive.

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Please cite the Guam Coastal Management Program when using data collected prior to October 2013. Guam Coastal Management Program, Guam Bureau of Statistics and Plans, Government of Guam. Please cite the University of Guam Marine Laboratory when using data collected after (and including) October 2013.

Example citation:

For data collected from 2010 to 2012:

Guam Coastal Management Program (YEAR accessed). Guam Long-term Coral Reef Monitoring Program Reef Fish Surveys since 2010. NOAA's National Center for Environmental Information, https://www.fisheries.noaa.gov/inport/item/47783.

For data collected after 2012:

University of Guam Marine Laboratory (YEAR accessed). Guam Long-term Coral Reef Monitoring Program Reef Fish Surveys since 2010. NOAA's National Center for Environmental Information, https://www.fisheries.noaa.gov/inport/item/47783.

None

None

Observations recorded on data sheets are entered into a data management website that populations a Microsoft SQL Server administered by the University of Guam Office of Information Technology

Observations included in this dataset were made by divers who have been trained, and met minimum standards in identifying species present at the survey location. Small fishes and those cryptic during the day, such as apogonids and holocentrids, are likely undercounted. While some small and/or cryptic taxa, such as most gobies or blennies, are not given high priority in the survey and are usually not reported, some larger-bodied or otherwise notable representatives of those taxa, such as Exalias brevis, Plagiotremus spp., and Valenciennea strigata may be reported.

Observations, including species identification, counts, and cylinder size and fish length estimates were periodically checked for consistency between divers. A 2020 analysis carried out by Dr. Peter Houk of the University of Guam Marine Laboratory detected some interobserver biases involving the two observers who's observations are included in this dataset. These biases, which are described in the Bias and Comparability sections below, appear to be related to the detection of more cryptic taxa, such as holocentrids, by the more experienced observer, and the detection of a greater number of larger-sized fish species identification. The latter bias may be related to differences in the degree of accuracy each observer exhibited in estimating cylinder size, but it may also have been an artifact of the survey methodology. No significant differences in the accuracy of species identifications or size estimates were detected between the two observers whose data is included in this dataset. However, observations by two other observers were removed from the dataset following Dr. Houk's study, as it was determined that total biomass and individual size estimates for survey replicates conducted by a relatively inexperienced observer in 2010 and 2011 were consistently higher in comparison to survey replicates carried out by a more experienced observer, and sampling station biomass was consistently lower for survey replicates conducted in 2015 by another observer.

The results of an analysis of the fish SPC dataset (food fish only) carried out in 2020 by Dr. Peter Houk of the University of Guam Marine Laboratory indicated that the size estimates of one observer ("RD") who participated in data collection efforts at the Tumon Bay and East Agana sites in 2010 and at the Western Shoals site in 2011 were consistently different enough from the more experienced observer ("VB") to justify removing these observations from the archived dataset. The removed observations include observations made by RD in 2010 at all of the surveyed stations in the Tumon and East Agana sites, and in 2011 at most of the sampling stations in the Western Shoals site. The observations made by RD in 2010 comprised the vast majority of fish SPC data obtained at the Tumon and East Agana sites that year, with data collected by VB at these sites in 2010 only representing one SPC replicate each at the TUM-16, TUM-18, EAB-10, EAB-16, and EAB-20 sampling stations. The increased availability of VB for surveys at the Western Shoals site in 2011 allowed VB to carry out at least one SPC replicate at most of the sampling stations at that site that year. Dr. Houk's analysis also showed that the observations of another observer ("RS") who briefly assisted with surveys of the Tumon Bay site in 2015 were consistently smaller than those carried out by the fish team lead at the same sampling stations. These observations, which were obtained during one replicate SPC survey each at 11 sampling stations in the Tumon site in 2015, were also removed from the archived dataset. Data collected by observers RD and RS can be made available upon request.

Additionally, Dr. Houk's analysis of the fish SPC data indicated that VB's observations generally included a larger number of species each site, and a greater number of observations of larger-sized fishes, than were recorded by AH. VB, who was the more experienced observer, tended to detect more species of cryptic fishes, such as holocentrids than the less experienced observer (AH). VB's detection of a greater number of larger-bodied species that tended to be more wary of divers could potentially be an artifact of the survey methodology, or of differences in the accuracy of each observer's estimate of the cylinder size. With the departure of VB from the monitoring program in late 2019, and the resulting reliance on a single observer (AH) to carry out both replicates at each sampling station in 2020 and 2021 will eliminate inter-observer bias for recent data collection efforts. However, any comparisons of fish SPC data collected before and after 2020 should account for the interobserver bias between VB and AH detected in Dr. Houk's analysis.

As mentioned in the Bias section above, the results of an analysis of the fish SPC data by Dr. Peter Houk indicated that a more experienced fish observer (VB) consistently reported a greater of number of species, and a greater number of larger-bodied species, than the less experienced fish observer (AH). Any comparison of data collected during the same time period by these two observers must account for these biases, as does any comparison of data collected before 2020 (by both VB and AH) to data collected during and after 2020 (solely by AH).

Additionally, changes in the fish SPC survey methodology must be taken into account. These changes, which are described in more detail in the Lineage section of the metadata record, include the addition of non-instantaneous observations in 2012; the delineation of different types of non-instantaneous observations from 2015 to 2019; and a major change in methodology beginning in 2020 whereby 1) all species are still listed during the first 5 minutes, 2) only food fishes are counted and sized after 5 minutes, 3) some non-food fishes are counted but not sized after 5 minutes, and 4) non-instantaneous observations are not delineated by timing. While species lists generated during the first 5 minutes of each survey should generally be directly comparable across all years, the shorter total survey time for a single replicate SPC survey beginning in 2020 (~15-25 min compared to ~35-40 min before 2020) will likely include fewer species if additional species recorded after the first 5 minutes are included in the species list. The exclusion of non-food fishes from the counting and sizing portion of the survey beginning in 2020 will prevent direct comparisons of total reef fish biomass for sites surveyed before 2020 and those surveyed during and after 2020. However, abundance, biomass, and length data for those taxa and taxonomic groups surveyed across all years are still directly comparable (but note inter-observer bias described in the Bias section above).

Comparisons of fish data across years should also take into account differences in lunar and tide phase. In addition, it should be noted that beginning in 2015 fish surveys were sometimes carried out during different sampling periods than other surveys (e.g., benthic photo transect, coral quadrat, macroinvertebrate, and rugosity surveys) for a given year. These sampling periods can be found in the Extents section of the metadata for each dataset. Comparisons of data across sites or across years must also take into account differences in environmental and biological aspects of each site. Comparisons for a given site across time should consider any changes to the site boundaries over time. Please refer to the Extents section of this metadata record to for a description of how the Tumon site boundaries shifted after 2010.

Only hard-bottom habitats are surveyed. Surveys are conducted annually to biennially for the Tumon and East Agana sites, but are conducted on a less frequent basis at other sites. In addition, while all permanent sampling stations are generally surveyed each sampling period, surveys are not always conducted at the full set of non-permanent stations for each site during each sampling period. Below is a summary of the number of permanent and non-permanent sampling stations surveyed each year for each site:

Tumon Bay: 2010 (belt: 10 perm, 10 non-perm; SPC: 10 perm, 10 non-perm); 2012 (2 perm, 2 non-perm); 2014 (0 perm, 5 non-perm); 2015 (12 perm, 10 non-perm); 2017 (12 perm, 10 non-perm); 2019 (12 perm, 10 non-perm); 2020 (12 perm, 10 non-perm); 2021 (12 perm, 10 non-perm)

East Agana Bay: 2010 (10 perm, 10 non-perm); 2015 (10 perm, 10 non-perm); 2017 (10 perm, non-perm surveys still in progress); 2019 (10 perm, 6 non-perm); 2020 (10 perm, 10 non-perm); 2021 (10 perm, 10 non-perm)

Western Shoals: 2011 (belt: 11 perm, 13 non-perm; SPC: 2 perm, 2 non-perm)

Piti Bay: 2012 (6 perm, 8 non-perm); 2014 (10 perm, 2 non-perm); 2017-2018 (10 perm, 10 non-perm)

Achang: 2014 (8 perm, 3 non-perm); 2018 (10 perm, 10 non-perm); 2021 (10 perm, 10 non-perm)

Cocos-East: 2014 (3 perm, 4 non-perm); 2018 (no fish data collected); 2021 (10 perm, 10 non-perm)

Fouha Bay: 2015 (10 perm); 2019 (10 perm); 2021 (10 perm)

Data entry and quality control are complete for surveys conducted through 2020; the entry and quality control of data collected in 2021 has not yet been completed.

The same method of data collection was used at each of the stations surveyed between 2010 and 2019, with some minor changes over time to refine data collection as described below in the process description. While the core SPC method continues to be utilized, significant changes were implemented in 2020 in order to simplify and shorten the survey. These changes include the exclusion of non-food fishes from the counting and sizing portion of the survey (although certain non-food fishes are still counted but not sized) and the elimination of recording timing (e.g., 5-10 min, 10-15 min, etc.) for non-instantaneous observations of fish taxa that enter the cylinder after the 5 min listing phase of the survey.

All observations entered into the database through the online data entry system are compared against observations recorded on the raw data sheet. Once all database records are verified the quality control process is marked as complete for all observations associated with a given station/sampling period. It should also be noted that the data management system employs hard and soft validation to minimize data entry errors.

University of Guam Marine Lab resources and assets

The Stationary Point Count Survey methodology for reef fishes, employed by the Guam Long-term Coral Reef Monitoring Program since 2010.