Nearshore fisheries in the Main Hawaiian Islands encompass a diverse group of fishers using a wide array of gears and targeting many different species. Communities in Hawaii often rely on these fisheries for economic, social, and cultural services. However, the stress from overfishing can cause ecosystem degradation and long-term economic loss. This layer represents the average annual catch of reef fish by non-commercial boat-based fishing methods. Average annual catch at the island scale from 2004-2013 was estimated from Marine Recreational Information Program (MRIP) combined fisher intercept and phone survey data (McCoy, 2015; McCoy et al., in prep). These island-scale estimates were spatially distributed offshore using distance to boat harbors and launch ramps while accounting for marine protected areas (MPAs) and de facto MPAs (e.g., military danger zones) where access is restricted. A Gaussian decay function assumed the majority of the catch occurs within 10-20 km of each harbor. Additionally, the Ocean Tipping Points (OTP) project weighted boat harbors by the human population present within 30 km. This layer's spatial footprint aligns with the inshore commercial reporting blocks for commercial fish catch reporting to the State of Hawaii Department of Aquatic Resources (DAR). This layer is the sum of the three final gear-specific non-commercial boat-based OTP rasters (line, net, and spear).

Point data for boat harbors and launch ramps were combined from two datasets available from the Hawaii Statewide GIS Program website (Harbors.shp and BoatingFacilities.shp) (http://planning.hawaii.gov/gis/download-gis-data/). Data were checked for quality to ensure only operational boat harbors and launch ramps were included and geographic positions were accurate. Anchorages, fishing piers, historic, and disused ramps/harbors were removed prior to analysis. Boat facility weighting factors were calculated based on total human population within 30 km of each boat harbor or ramp. Human population was mapped based on 2010 census data and LANDFIRE land use/land cover data using the USGS Dasymetric Mapping Tool to gain a more accurate representation of population distribution. A 30-km buffer was then created around each boating facility and a Zonal Statistics tool was used to sum the human population within each buffer. These population values were then used to assign weights to each boating facility in order to allocate a proportion of total island catch estimates to each boat harbor or ramp. These weights sum to 1 for each island.

In order to allocate catch proportionally to each boat harbor/ramp, estimated annual catch at the island scale and the human population-based weighting factor were joined to the attribute table of each boating facility's cost allocation footprint and used in a Gaussian decay function with each distance surface. This decay function assumes the majority of catch occurs within 10-20 km of a harbor or ramp and declines more rapidly with increasing distance. Catch in full no-take MPAs were set to zero and other areas with restricted access were reduced according to expert input and local knowledge. Pixel values within each boating facility's footprint were then rescaled such that the sum in each footprint was equal to the respective boat facility's weighting factor times the MRIP catch estimate for that island in units of kg per pixel. Finally, all raster layers for each boat harbor/ramp were summed together.

Final pixels values are in units of kg/ha such that the sum of all pixels for each island is equal to the estimates of average annual catch from McCoy et al. (in prep). Units, pixel size, and grid alignment are consistent with all other OTP fishing layers so that they can be compared directly or added together for various uses.

See also:

McCoy, K. 2015. Estimating nearshore fisheries catch for the main Hawaiian Islands. Thesis. University of Hawaii at Manoa.

McCoy, K., Friedlander, A., Kittinger, J., Ma, H., Teneva, L., Williams, I.D. In prep. Estimating nearshore fisheries catch for the main Hawaiian islands. PLoS One.