2 Acoustic data collection
The acoustic database is designed for the storage of acoustic data. The data were collected using an echosounder either mounted on a vessel, towed by a vessel, or in a fixed location. The performance and characteristics of the echosounders used vary
widely but generally involve sophisticated electronic equipment and associated software. A detailed description of how and why acoustic data are collected is available [MacLennan & Simmonds 1992]. The echosounders used to collect the acoustic data have changed considerably over the years, driven mainly by advances in electronic and computer technologies. However, the basic data have remained the same.
An echosounder periodically emits a pulse of sound (it ‘pings’) and then listens for echoes of this pulse. The range and amplitude of the echoes are measured and stored. Associated data such as the date, time, and vessel position are also stored.
The acoustic database contains data collected from acoustic surveys starting in 1984 through to the present day. Species on which acoustic data have been collected include hoki, hake, smooth and black oreos, orange roughy, and southern blue whiting. Areas from which these data have been collected include the Chatham Rise, the Campbell Plateau, the west coast of the South Island, Cook Strait and various inshore regions around New Zealand. The data are used primarily to estimate the biomass of fish species for the Ministry of Fisheries.
Aside from the acoustic data, this database also stores various ancillary data that provide context to the acoustic data. This includes such data as vessel position, speed, and direction of travel. Details on the echosounder equipment and software settings are also stored, as are the results of any equipment calibrations.