Multi beam bathymetry and backscatter synthesis for the Main Hawaiian Islands (5 meter resolution)

The Hawaii deep-slope bottomfish fishery preferentially targets seven high value species (i.e. six snappers and one grouper, hereafter referred to as Deep7) and represents the major insular commercial fishery in the state. The NOAA Pacific Islands Fisheries Science Center (PIFSC) Stock Assessment Program (SAP) is responsible for regularly assessing this stock.

To augment and improve the data used in the Deep7 assessment, PIFSC began developing a multi-gear Bottomfish Fishery-Independent Survey (BFISH) for the Deep7 stock in the Main Hawaiian Islands (MHI) in 2011 (Richards et al., 2016). Benthic habitat has been shown to play a key role in determining the spatial distribution of demersal living marine resources (Richards et al., 2012). The BFISH survey employs a stratified random sampling design based on depth and habitat.

Prior to the work presented here, the lack of usable backscatter data across the entire MHI domain was a major impediment to the development of a properly stratified operational fishery-independent survey covering the full domain of the stock. While backscatter data had been collected throughout the MHI, these data were collected using various platforms and sensors such that numeric backscatter values from disparate areas did not represent similar levels of substrate hardness. This precluding development of a comprehensive survey stratification across the MHI domain of the Deep7 stock.

To remedy this situation, the NOAA Pacific Islands Fisheries Science Center conducted a one-year project to create comprehensive, high-resolution, synthesized depth, slope, and seafloor hardness maps and GIS layers for the Main Hawaiian Islands. This paper describes that effort in two parts:

1. Part I: Methods and results pertaining to the development of a 5-meter resolution Main Hawaiian Islands bathymetric and backscatter synthesis covering depths of 75 to 400 m;

2. Part II: Novel methods and results associated with the use of these newly created synthesis data in quantitatively defining effective habitat strata ratification for the NOAA PIFSC Bottomfish Fishery-Independent Survey in Hawaii (BFISH).

These data products will be used for experimental design and stratification of teh Pacific Islands Fisheries Science Center (PIFSC) Bottomfish Fishery-Independent Survey in Hawaii (BFISH) as well as to investigate physical factors correlated with distribution of Hawaiian bottomfish species.

This is a rescaling and synthesis of existing multi beam data products to create seamless and single scale products for the MHI.