Fishing technology
A wide range of vessels and equipment are used to extract an even wider range of marine organisms from the waters of the Australian Fishing Zone (AFZ). Technological advancements have increased the efficiency of fishing and expanded the environments that may be fished. Such advancements relate to the design of fishing vessels and the fishing gear being utilised, as well as the variety of electronic equipment used to locate and target fish.
The Australian fishing zone (AFZ)
(note the area adjacent to the Australian Antarctic Territory is not part of the AFZ)
Vessels and fishing gear
As the various components of fishing vessels and their equipment have been improved over time, so has the vessels' efficiency, expressed as their ability to catch more fish in a shorter time. As an example, consider the demersal (bottom) trawling off the southeast coast of Australia (now part of the South East Fishery - SEF), which began early this century. For most of this century the trawlers were large, steam-driven vessels with high capital and running costs. Steam trawlers had all but disappeared by the early 1970s when the diesel-engined trawler, along with cheap hydraulic winch systems running from the single power plant, began to predominate. From that time, the trawl fleet underwent an explosive increase in terms of both numbers of vessels and their efficiency. The light, powerful diesel engine and hydraulic winch allowed the use of reasonably large trawl nets on a vessel that was relatively small and inexpensive to run. A raft of other technological advances have been implemented in this fishery over the past few decades, including improvements in hull shape, propeller efficiency, efficiency and versatility of the trawl gear, netsondes to provide information on the position and status of the trawl gear, satellite navigation (GPS) and a wide range of acoustic equipment (see Sounders and Sonar). Thus the 'fishing power' of a trawler in 1997 may be several times that of a trawler from the early 1970s.
Similar advances have taken place in other fisheries—such as in tuna longlining where enhanced freezer technology, new line materials and line-handling systems, and the availability of oceanographic-sensor equipment and satellite-derived sea-surface temperature imagery have greatly improved the fishing power of longline vessels.
In many fisheries, technological advances have steadily allowed access to resources that were previously beyond the ability of vessels to target. For example, demersal trawlers in the SEF now regularly trawl at depths well in excess of 500 metres, exploiting fisheries resources on the continental slope and sea mounts. However, while the technology may be available to exploit such fisheries resources, the capital investment required may be high, and the venture relatively high-risk. In some cases this may render the potential fishery economically unviable or beyond the reach of an individual vessel owner. In the developing Western Australian tuna and billfish fishery, for example, the target species are the valuable bigeye tuna that occur well offshore. The majority of the vessels participating in the fishery were small Western Australian rock-lobster-style aluminum craft that were weather dependent and, for the most part, unable to access the bigeye grounds. The introduction of larger purpose-built longliners has expanded the fishing capacity of the fleet significantly.
Another increasingly important aspect of fishing-gear technology and design relates to reducing bycatch and the impact of fishing on non-target species. This refers to unwanted fish and other organisms caught by the gear (e.g. fish, seabirds, turtles) and also to the impact of the gear on the marine environment (e.g. the impact of trawl gear on bottom living organisms). Recent work in Australia has centered on developing bycatch reduction devices (BRDs) for sea turtles in the northern prawn trawler fleets. However, as has been found by trawlers in the northern prawn fishery, the usefulness of BRDs can go well beyond the avoidance of a specific species, and be used to exclude a range of unwanted organisms, producing a significantly 'cleaner' catch. Because the nature of the catch and bycatch is highly specific to the fishery or area, development of bycatch reducing technology is an ongoing process involving extensive experimentation and testing within different fisheries. Reducing bycatch and the effect of fishing on the marine environment will most likely remain a priority for the management of the AFZ in the foreseeable future. Technological developments have the potential to provide solutions.
Targeting of highly localised aggregations of orange roughy has greatly benefited from the use of GPS navigation, advanced sonar location and a variety of trawl gear monitoring technologies.
Sounders and sonar
The use of sonar and sounding equipment is commonplace in many fisheries vessels. Modern sonar gives the ability to locate schools of fish in the water column and then to position the fishing gear accurately to target the school. The technology is now commercially available to classify the bottom type (e.g. rock, sand, silt) by processing the signal from a depth sounder. This, in conjunction with Global Positioning Systems (GPS), digital charts and personal computers, allows an operator to build a highly detailed three-dimensional model of their fishing grounds over time. When further integrated with information on catches, weather, time and tide, such systems can incorporate much of the information and experience an operator gains over time. Improvements in commercially available sounder and sonar technology will likely continue with the incorporation of more frequencies, higher levels of resolution and a better ability to detect and discriminate fisheries resources for targeting.
For some decades acoustic techniques have been used as a survey tool in estimating the abundance or biomass of fish stocks. Only recently has it been possible to determine, with some confidence, the identity of the fish schools being detected. The CSIRO's multi-frequency towed device (MUFTI) technology is capable of discriminating both fish species and size, and has been used in trial surveys of deep-water species such as orange roughy and blue grenadier. Acoustic biomass-surveys are particularly suited to species were the population aggregates into a small area, such as during spawning. In the case of orange roughy the multi-frequency system has significantly reduced the uncertainty surrounding biomass estimates, and generally improved the assessment of the stocks' condition. Whilst not directly applicable at present, this sort of technology is under continuous development and will eventually flow through to the fishing industry in the future.
The other main acoustic device that will have an increasingly marked affect on fisheries development is the sidescan sonar with its ability to produce detailed maps of the seabed. Sidescan sonar maps the seafloor in a swath either side of the vessel—hence the term 'swath mapping'. Despite the comprehensive look of broad-scale bathymetric charts, most Australian waters are very poorly mapped, with large areas virtually unknown. The directed use of high-resolution swath mapping over the past few years has had spectacular results in the waters around, and to the south of, Tasmania. Examination of swath mapping of the Chatham Rise (east coast of New Zealand) almost doubled the estimated area suitable for orange roughy in the area. Geoscience Australia (GA) is currently undertaking the Seabed Mapping and Characterisation project, which is expected to provide detailed seabed mapping of the entire Exclusive Economic Zone (EEZ). The project will provide data to support Australia's UNCLOS claim to seabed beyond the EEZ and assist in Regional Marine Planning.
Satellites and remote sensing
The development of various satellite systems has provided fishers and fisheries managers with a variety of significant advancements and tools, and will continue to do so in the foreseeable future. One of the biggest advances in recent times has been the widespread availability of Global Positioning System (GPS) receivers. GPS allows vessels to be positioned within an accuracy of a few tens of metres, anywhere in the world. GPS has allowed previously inaccessible areas to be precisely targeted, and the positions of fishing spots or topographic features to be accurately marked. Inexpensive and accurate positioning has allowed the development of computer systems that associate depth, bottom type, catch and time information with location to provide onboard fishing-information systems.
Vessel Monitoring Systems (VMS) using INMARSAT and ARGUS satellites allow the position of vessels, fitted with an appropriate transceiver and GPS, to be determined at regular intervals from shore. VMS is used to gauge the distribution of effort in a fishery and as a compliance tool. Within the AFZ, VMS is currently used in various Commonwealth and Queensland fisheries, where it has gained industry acceptance; it is also used for secure ship-to-shore communications. Worldwide, VMS is viewed with deep reservation by the fishing industry and moves for its broad introduction to fishing fleets are often contentious.
Remote-sensing and remote-imaging satellites produce a wide range of oceanographic and biological information useful in research and as a tool for locating fish schools. Near-real-time imagery of ocean temperature is used by tuna longline fleets to identify temperature fronts associated with high catch rates of tuna. Similarly, ocean colour may be used to monitor the movement of water bodies and to map the primary productivity of the ocean surface. Existing and future remotely-sensed imagery has substantial potential benefits for fishing fleets in both the inshore and offshore environments, but remains largely unused by industry in Australia.
Chlorophyll in surface waters around Australia (4 Sept - 31 Dec 1997). Chlorophyll is determined by sensing ocean colour with satellite imagery and is an indicator of primary production. Ocean-colour and sea-surface temperature satellite imagery is used to target tunas and other pelagic species (provided by the SeaWiFS Project, NASA/Goddard Space Flight Center).