Linkages between reef fish demographics and benthic habitat characteristics in Tutuila, American Samoa and Main Hawaiian Islands

Benthic habitats play vital roles in the distribution and abundances of marine resources. Understanding how fish populations respond to variability of benthic habitat characteristics is essential for effective coral reef management and monitoring. A pilot study was conducted by NOAA Pacific Islands Fisheries Science Center (PIFSC) Coral Reef Ecosystem Program (CREP) to examine the relationships and linkages between the geomorphological benthic characteristics and fish demographics in Tutuila, American Samoa and the analysis was later expanded to the main Hawaiian Islands.

Geomorphological metrics characterizing benthic habitats including slope, rugosity, curvature, and convexity were derived using best available bathymetry for each area. The fish assemblages and abundance data were collected during Rapid Ecological Assessment (REA) surveys from 2010 to 2016. These fish data were collected according to a stratified random survey design using depth as an environmental correlate. Based on the analysis for Tutuila, American Samoa, preliminary evidence was found that using both depth and convexity to define strata may result in more precise estimates of fish biomass. This analysis was expanded to the main Hawaiian Islands for the subsequent year of the project, and found that including several other metrics in CREP's sampling design can enhance the estimates of fish biomass.

Results and data from the analysis for Tutuila, American Samoa can be accessed online via the Pacific Islands Benthic Habitat Mapping Center website at http://www.soest.hawaii.edu/pibhmc/pibhmc_documentation.htm#other_pubs.

The PIFSC administrative report from the analysis for the main Hawaiian Islands is in review as of Aug 2017 and will be available on the PIFSC website once published at https://www.pifsc.noaa.gov/library/staff_publications.php.

This multi-year project is funded by NOAA Coral Reef Conservation Program (CRCP) and the analysis informs efforts to improve reef monitoring and management, and determines which geomorphological characteristics are most effective for predicting fish populations. It also supports the operational needs of NOAA Coral Reef Ecosystem Program’s field data collection.

Gorospe K, Acoba A. In Review. A sampling design performance analysis examining linkages between reef fish assemblages and benthic morphologies in the main Hawaiian Islands. Pacific Islands Fisheries Science Center Administrative Report H-17-##, ## p. <DOI URL>

The zip file that contains the downloadable data includes all the data (CSV files) used for carrying out the analysis detailed in the final report for the Tutuila pilot analysis. The name of each CSV file includes a geomorphology metric and a number (0, 30, 50, or 100), corresponding to the radius of the spatial averaging buffer (i.e., four different spatial scales) used to generate the metric.

The following geomorphology metrics were examined as part of this study: aspect, convexity, profile curve, rugosity, slope, and surface area. Each CSV file includes site-specific fish survey data reported as biomass (grams per meter squared) of all fish; piscivores, primary consumers, secondary consumers; parrotfishe; and three different size classes (0-20 centimeters, 20-50 centimeters, and greater than 50 centimeters). Site-specific field data such as depth and benthic cover are also included.

Included with the downloadable data is a ReadMe.txt file that includes the definitions for the following columns that are included in the data files: SITE, SITEVISITID, METHOD, OBS_YEAR, REGION, ISLAND, DATE_, REEF_ZONE, DEPTH_BIN, geomorphology metric, PISCIVORE, PLANKTIVORE, PRIMARY, SECONDARY, TotFish, 0_20, 20_50, 50_plus, Parrotfish

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. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

Initial pilot study for Tutuila, American Samoa

Expanded study to the Main Hawaiian Islands

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Coral Reef Ecosystem Program (CREP) Data Sharing Recommendations, version 9.0 updated August 12, 2015:

CREP welcomes the opportunity to collaborate on research issues contributing to the scientific basis for better management of marine ecosystems. CREP has a very diverse set of field activities that generates large volumes of data using an array of data collection protocols.

The following recommendations are for your consideration as you use this data:

1) Data analyses should take all field exigencies into account. The most effective way to do this would be active collaboration with CREP principal investigators.

2) In all presentations, product releases, or publications using data generated by CREP, proper acknowledgement of both CREP and the individuals responsible for data collection is expected. Citing the DOI (if available) is preferred, a non-DOI example is listed below.

3) If you collect or generate data for the same study areas, CREP requests that you share relevant information on complimentary data collections.

4) Those receiving data are strongly urged to inform the CREP Data Management Team of any errors and discrepancies that are discovered during the course of using these data. They are further urged to bring to the attention of the Team all problems and difficulties encountered in using these data. This information is necessary in order to improve the collections and to facilitate more efficient and economical data processing and retrieval. The users are asked to supply copies of any missing data that may be located, and to provide information as to significant subsets and special aggregations of data that are developed in using the material provided.

Example citation:

"This publication makes use of data products provided by the Coral Reef Ecosystem Program (CREP), Pacific Islands Fisheries Science Center (PIFSC), National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), with funding support from the NOAA Coral Reef Conservation Program (CRCP). The analysis and interpretations presented here are solely that of the current authors”

Data can be accessed online via the Pacific Islands Benthic Habitat Mapping Center website.

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Please cite NOAA Coral Reef Ecosystem Program (CREP) when using the data.

Example:

Pilot study for Tutuila: Coral Reef Ecosystem Program; Pacific Islands Fisheries Science Center (2015). Linkages between reef fish demographics and benthic habitat characteristics in Tutuila, American Samoa. Pacific Islands Benthic Habitat Mapping Center. http://www.soest.hawaii.edu/pibhmc/pibhmc_documentation.htm#other_pubs.

Main Hawaiian Islands: Gorospe K, Acoba A. In Review. A sampling design performance analysis examining linkages between reef fish assemblages and benthic morphologies in the main Hawaiian Islands. Pacific Islands Fisheries Science Center Administrative Report H-17-##, ## p. <DOI URL>

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Data streams were compiled and analyzed by CREP researchers using MS Excel, ArcGIS 10.3, Benthic Terrain Modeler (BTM) 3.0 ArcGIS Extension, System for Automated Geoscientific Analyses (SAGA) 2.1.4, R version 3.1.2.

Two datasets collected by NOAA Coral Reef Ecosystem Program (CREP) were used for Tutuila, American Samoa. Gridded bathymetry compiled from multibeam data collected in 2004 and 2006 was used to derive geomorphological data including aspect, slope, rugosity, curvature, and convexity. The other dataset is in-situ fish demographic data collected under the Pacific Reef Assessment and Monitoring Program and the NOAA National Coral Reef Monitoring Program between 2010 and 2015. Gridded bathymetry and geomorphological data were then spatially correlated to the fish demographic data.

For the main Hawaiian Islands, LiDAR (Light Detection and Ranging) collected by U.S. Army Corps of Engineers (USACE), JALBTCX (Joint Airborne Lidar Bathymetry Technical Center of eXpertise) in 2013 were used to derive geomorphologic data. In addition to the metrics generated for Tutuila, slope of slope was also derived for the main Hawaiian Islands. The in-situ fish demographic data were collected between 2010 and 2016.

Geomorphological data inherit the accuracy of the source gridded bathymetry. The attribute and positional accuracies of the gridded multibeam bathymetry for Tutuila, American Samoa are reported in the metadata which can be found at http://www.coris.noaa.gov/metadata/records/html/tutuila_5m.html. The accuracies of the gridded LiDAR data can be found for each island in the main Hawaiian Islands at https://coast.noaa.gov/htdata/lidar1_z/geoid12a/data/. For the fish demographic data, researchers are trained to identify and estimate/measure the size of fish. Both classroom and field training and tests must be completed for all researchers before each round of surveys begins. This training ensures that the surveys are conducted consistently by all researchers within survey efforts and also across periodic survey efforts.

Fish demographic data used for this analysis were collected in 2010, 2012, and 2015 for Tutuila, American Samoa, and 2010, 2012, 2013, 2015 and 2016 for the main Hawaiian Islands. The target precision for these surveys is large enough (e.g., Coefficient of Variation less than 20%) that inter-annual change would likely only be detectable on a decade timescale. Therefore, all survey years used in this analysis are likely comparable, but could easily be addressed by running the analysis separate for all years.

For Tutuila, American Samoa, multibeam bathymetry data were not available for shallow areas where the NOAA Ship Hi'ialakai (a 218-foot research ship) or R/V Acoustic Habitat Investigator (a 25-foot survey launch) were not able to access. Bathymetry derived from multispectral IKONOS satellite imagery was investigated for shallow areas to fill gaps; however, bathymetry derived from IKONOS imagery was not included in the analysis due to uncertainty of the attribute accuracies. Therefore, the fish demographic data collected in areas where multibeam bathymetry data is not available (i.e., shallow areas generally less than 6 meter depths) were omitted from the analysis.

For the main Hawaiian Islands, LiDAR data were not available for Niihau and Kahoolawe islands, and parts of Lanai and Big islands. The fish sites surveyed in the areas where there is no LiDAR data available were removed from the analysis.

The target Coefficient of Variation (CV) for fish demographic data reported at the island-level is 20%.

This is only a preliminary analysis of the relationship between geomorphological data and fish biomass. For Tutuila, American Samoa, Convexity was chosen for further analysis based on a qualitative assessment. Due to the incompleteness of the bathymetry data in Tutuila, American Samoa described in the “Completeness Measure” section, ideally the analyses should be conducted for a location where bathymetry data is available for shallow areas. For the main Hawaiian Islands, Rugosity, Slope, Slope of Slope and Profile Curvature were chosen for the further analysis.

All geomorphological data were derived using SAGA. Some data were cross-checked with data derived using ArcGIS and the Benthic Terrain Modeler (BTM) ArcGIS extension. Sanity checks were performed to examine the process of spatially correlating the gridded bathymetry and geomorphological data with fish demographic data.

University of Hawaii School of Ocean and Earth Science and Technology, NOAA IRC and NOAA Fisheries ITS resources and assets.

This project involves two primary analyses: one is to derive geomorphological data from gridded bathymetry, and the other is to examine the linkage between derived geomorphological data and fish demographic data from in-situ biological surveys. The analysis was performed for Tutuila, American Samoa during first year of the project, and then for Main Hawaiian Islands during the second year of the project.