NIWA – seabed and habitat mapping

25 August 2009

Tags: productivity, economy, report, government

This case study has been taken from the Spatial Information in the New Zealand Economy - Realising Productivity Gains report, August 2009.

Advances in GPS technology have enabled the mapping of habitat, seabed, catch information, and fish stocks. These advances have helped transform spatial data into meaningful information that can be used to catch fish as well as manage stocks over time.

Computer programs that connect into a vessel's GPS, sounder and seafloor discrimination devices are, for example, being used to create databases of the seabed's topography in the area that a boat fishes. By creating 3D maps of the seafloor instantly, fishers are pinpointing hills on the sea floor on which to set and tow trawls. Programmes are also being used to mark the location and movement of long-lines, nets and pots in 3D in order to avoid foul ground where fishing gear becomes caught on the seafloor. This technology is outlined in Figure 12.

Recent progress with spatial technology has also enabled the mapping of marine species and their habitats at a smaller spatial scale. The National Institute of Water and Atmospheric Research (NIWA's) 'Marine Recreation' research programme in the inner Hauraki Gulf sought to better understand the inter-relationships between the recreational snapper fishery, snapper populations, and the underlying seafloor habitats, including the invertebrate animals living there. Habitat mapping used as part of this research programme involved a number of key steps:

• A geographic information system (GIS) used data to produce broad scale habitat maps of seafloor features such as plateaus, holes, ridges, slopes, and channels.
• An underwater video (DUV) towed along transects was used to create finer scale seafloor habitat types to determine what the different physical features from the remote mapping actually were.
• Estimates of snapper catch, and snapper abundance observed along the DUV was then related back to the different habitat types in which different abundances of snapper were observed. An assessment was also made of how the type of prey items snapper were targeting related back to the different kinds of seafloor habitats.

These various datasets can be used to create new maps that enable the rapid assessment of habitat features, and then predict the relative values of those places for fish and fishers, and likely threats to those values.[1]

Figure 12: Seabed topography

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References

[1]    Mark Morrison, Ude Shankar, Darren Parsons, Glen Carbines, and Bruce Hartill Snapper's-eye view of the inner Hauraki Gulf Water & Atmosphere 16(2) 2008