Most fishing techniques in use today have their origin in an era when fisheries
resources were abundant, energy costs were much lower than current levels, and less
attention was paid to the negative impacts of fishing on aquatic and atmospheric
ecosystems. Current high energy prices and greater awareness of ecosystem impacts are now realities and present major challenges to the viability of fisheries, particularly in
developing countries where access to and promotion of energy-efficient technologies
have been limited. However, as illustrated in this article, which is largely based on
a paper by Suuronen et al., each type of fishing gear and practice has advantages
and disadvantages, and the suitability of each gear type depends considerably on the
operational conditions and on the species to be targeted.
The impacts of fishing gear on ecosystems vary widely. Overall, these impacts largely depend on: the physical characteristics of the gear; the mechanics of its operation; where, when and how the gear is used; and the extent of its use. Moreover, gear types that rank high for one kind of impact may rank low for another. Physical damage to the environment may also result from the inappropriate use of an otherwise acceptable gear. Only a small number of fishing methods are recognized as inherently destructive no matter how they are used, prime examples being explosives and toxins. It should also be kept in mind that in spite of the fact that many fisheries are highly selective, fishers are often not capable of catching only the desired target species. When poorly selective fishing occurs, it leads to the incidental catch of fish and invertebrates, part of which may consist of juveniles of ecologically important and/or economically valuable species. In addition, fishing can also result in the incidental mortality of non-target species of seabirds, sea turtles and marine mammals, as well as causing damage to vulnerable ecosystems, such as coldwater corals, which can take many decades to recover.
With regard to greenhouse gas (GHG) emissions, insufficient attention has been paid to the fisheries sector as a whole and to fishing operations in particular. Consequently, it is difficult to rank fishing gear and practices in terms of GHG emissions. However, using the consumption of fuel as a proxy for total GHG emissions can provide a good estimate. It is also a fact that, notwithstanding the provisions of existing international conventions, the quality of available fuel is not constant worldwide with regard to sulphur content.
It is noteworthy that life cycle assessments show that significant energy consumption and GHG emissions occur after the catch is taken on board and more so after landing, owing to fish processing, cooling, packaging and transport. Thus, minimizing the impacts and energy consumption throughout the whole product chain would be important to reducing the overall environmental costs of fishing.
The fishing sector should strive to further lower its fuel consumption and decrease ecosystem impacts. Despite a growing number of initiatives and experimentation with energy-reducing technologies, there is currently no viable alternative to fossil fuels for mechanically powered fishing vessels. However, it is well demonstrated that, through technological improvements, gear modifications and behavioural change, the fishing sector can substantially decrease the damage to aquatic ecosystems, reduce GHG emissions (which is a legal obligation for governments under existing international conventions) and lower operational costs for fuel without excessive negative impacts on fishing efficiency.
Solutions by fishing operation
Trawls are flexible gear and can be used on many types of areas and grounds, in
shallow and deep waters, and by small and large vessels for a wide range of target
species. These characteristics have made trawling the preferred method for many
fishers, and it may be the only short-term economic solution for capturing, for example,
certain shrimp species. However, bottom trawling has been identified as one of the
most difficult to manage in terms of bycatch and habitat impacts.
There are many techniques and operational adaptations available to reduce the drag and weight of the bottom trawl gear and, thereby, to reduce significantly fuel consumption and sea-bed impacts without marked decrease in the catch of the target species. Fuel savings of 2545 percent and gear-drag reductions of 2035 percent have been reported.
However, in general, further work is needed to improve the construction of
different components of trawl gear in order to minimize friction on the bottom
and to reduce overall gear drag. In this regard, there is further potential to develop
technologies in which the force of trawl doors and ground gear on the sea bed is
automatically measured and adjusted by instrumentation (Figures 38 and 39). In the
case of beam trawls, progress has been made in recent years by developing alternative gear designs. In essence, the objectives are to reduce the amount of tickler chains,
avoid excess weight in the beams, and use other stimuli (e.g. electric pulses) as an
alternative to chains to scare the target fish off the bottom and into the net. The use of
acoustics, light or any other additional stimuli to enhance encounters by target species
within the catching zone of trawl nets is worth exploring.
The use of improved location and targeting of fish with the help of electronic seabed mapping tools and integrated global navigation satellite systems has resulted in avoidance of sensitive bottom habitats and helped to minimize fishing effort and fuel consumption. Multibeam acoustic technology, widely used in sea-bed exploration, has been successfully applied, for example, to mapping scallop beds off the east coast of Canada, thereby substantially reducing the time required to locate the grounds and the actual fishing time.
Bottom seining (Danish, Scottish and pair seining) is generally considered to be a more environmentally friendly and fuel-efficient fishing method than bottom otter trawling. The gear is lighter in construction and the area swept is smaller than in bottom trawling. Moreover, because there are no trawl doors or heavy ground gear, there is less force on the sea bed. The light gear and low hauling speed mean that fuel usage can be significantly lower than for a comparable trawling operation. Bottom seine nets are generally also regarded as having low impact on benthic invertebrates. However, the high bycatch of both undersized individuals of the target species and individuals of non-target species can be a problem in some seine fisheries.
Trap-nets are passive fishing gear that are usually set on traditional sites in the path of migrating fish in relatively shallow coastal waters. Leader-netting herds and guides fish into a holding chamber or pound where they are entrapped. The pontoon trap is a more recent innovation and offers various advantages compared with traditional trap-nets such as being easy to transport, handle and haul, adjustable in terms of size, target species and capture depth, as well as being predator-safe. Future developments may include large-scale, ocean-based fish traps together with the technology to attract fish. Modern trap-net fisheries can be energy efficient, flexible, selective and habitat-friendly, providing catches of high quality as the catch is usually alive when brought aboard the vessel. Live capture provides the operator with a greater number of options to add value to the catch. However, designs and practices need to be developed to prevent the entangling of non-fish species in netting and mooring ropes of the trap.
A pot is a small transportable cage or basket with one or more entrances designed to
allow the entry of fish, crustaceans or cephalopods, and prevent or retard their escape.
Pots are usually set on the bottom, with or without bait. While pot fishing vessels in
general have low fuel use, some pot fisheries have high fuel use owing to the need
to tend fleets of many pots and lifting them more than once a day, necessitating
travelling at high speed over long distances.
Pots are extensively used in the capture of crustaceans such as lobster and crab. Although the use of pots for capturing finfish has a long tradition in many parts of the world, it has progressively declined. Nevertheless, pots are still an efficient and economically viable fishing method for finfish. They are also successfully used in fisheries targeting coral-reef species inhabiting areas where the use of active gear is banned or not practical.
Recent tests with collapsible pots have shown promising results for Atlantic cod in Canada and for pink cusk-eel (Genypterus blacodes) in Argentina. A floating pot developed in Scandinavia provides another example of an innovative pot design that has shown significant potential. Floating the pot off the bottom allows the pot to turn with the current so the entrance always faces down current, resulting in a higher catch rate of cod. It also avoids non?target catch of crabs and may also reduce the seabed impacts compared with a pot sitting on the bottom. The same type of floating pot has successfully been tested in the Baltic Sea as an alternative to the gillnet fishery for cod, where there are serious problems with depredation by seals.
Compared with many other types of fishing gear, pots, like trap-nets, possess several appealing characteristics such as low energy use, minimal habitat impact, high quality and live delivery. On the negative side, lost or abandoned pots may continue catching target and non-target species (ghost fishing) and contribute to marine debris with associated effects. Design features such as biodegradable materials may reduce ghost fishing, while delayed surface marker buoys and location aids may promote the recovery of lost gear. Understanding fish behaviour in relation to pots is essential in order to increase efficiency for those species that are currently not captured by pots in commercially viable quantities.
Hook and line
Hook and line refers to gear to which fish, squid or other species are attracted by natural or artificial bait or lures placed on a hook, on which they are caught. Wide variations in hook and line configuration and their mode of operation have made them an effective gear type for a wide variety of species. It is a versatile fishing method, employed by a wide range of vessels from artisanal boats to large mechanized longliners. Hook and line fishing is generally considered an environmentally friendly but labour-intensive fishing method that catches fish of high quality. Fuel consumption in these fisheries is comparatively low although it can increase significantly depending on the distances vessels have to travel to and from the fishing ground (e.g. coastal hook and line fisheries versus high seas tuna longlining). Longline fishing may cause the incidental mortality of seabirds, sea turtles and sharks, many of which are either protected or endangered. The lines can be set with a streamer67 in order to deter seabirds from seizing the baited hooks this system is reported to have led not only to a reduced mortality level of sea birds but also to higher catch rates of the target species. There are several other mitigation measures capable of reducing the likelihood of incidental bycatch of seabirds68 and sea turtles,69 such as the new circle hook and weak hook. While bottom-set longlines may snag and damage benthic epifauna and irregular objects on the bottom, longline fisheries do offer the potential to conduct fishing without severe habitat damage and to do so in a relatively energy-conscious manner.
Bottom-set gillnets, entangling nets and trammelnets are widely used, and improved
materials and techniques have allowed the expansion of such gear to rougher grounds
(including wrecks and reefs) and deeper waters. Gillnetting is a very versatile and
flexible fishing method but can also be labour-intensive. Except with trammelnets,
the size selectivity for finfish is generally good, but species selectivity can be poor. In
addition, fish are often injured and die during capture; accordingly, catch quality is
typically not as good as with pots, traps and longlines, although gillnets may also give
catch of good quality when the time the net is left in the water to fish is short.
Gillnet fishing operations in general can damage benthic epifauna during retrieval of the gear, at which time the nets and leadlines are more likely to snag bottom structures. Although the capture of seabirds, sea turtles and marine mammals by gillnets has received increased attention in recent years, more development work is required to develop mitigation measures further.
The impacts of ghost fishing by abandoned, lost or otherwise discarded gillnets are of concern as such nets may continue to fish for long periods depending on their construction, the depth, and prevailing environmental conditions. This problem can be addressed by increasing efforts to avoid losing gillnets and by facilitating the quick recovery of lost nets. Abandoned gillnets have been identified as a particular problem in deeper waters and where long lengths of gear are deployed.
Barriers to change
There are many barriers to the transition to low-impact and less fuel-intensive practices and gear. In summary, the most important seem to be:
- lack of familiarity with cost-effective and practical alternatives;
- limited availability of suitable technologies, especially in developing countries;
- incompatibility of vessels with alternative gear;
- risk of losing marketable catch;
- additional work at sea;
- concerns with safety at sea related to using unfamiliar gear or strategies;
- high investment costs;
- lack of capital or restricted access to capital;
- ineffective technology infrastructure support;
- inflexible fisheries management systems that include too rigid regulatory regimes.
With regard to inflexible management systems, regulatory regimes that are too
rigid can create a new set of problems to be solved and deny fishers the flexibility
required to innovate and adopt new technologies. In this regard, stakeholders should
be an integral part of the management process, particularly as and when amendments
to legislation are under consideration. Changes from high-energy high-impact fishing
methods or practices to ones with lower energy consumption and lower ecosystem
impacts offer opportunities for conserving fuel, preserving ecosystems and improving
food security. However, the transition from one gear type to another is seldom easy
or practical. First, the size and design of existing fishing vessels and their machinery
and equipment often limit the possibilities of changing the fishing method. Second,
fishing gear, fishing vessels, operations and practices have evolved around specific
fishing grounds and the behaviour of target fish species over a considerable period.
Accordingly, the evolved fishing gear and practices are tailor-made to catch specific
target species or species groups in a manner that is often perceived to be optimized
to the best technical and economic scenarios that will be encountered during fishing.
Moreover, where fishing practices are rooted in tradition there is a strong resistance to
Nevertheless, fuel consumption and ecosystem impacts can often be reduced through simple modifications in operational techniques and gear design without drastic changes in the gear and operational practices. This approach has shown promising results in many cases and is often preferred by the fishing industry over transitioning to a completely new gear type and fishing practice, which is an alternative that has many more uncertainties and higher economic risks.
International conventions include timetables for compliance regarding emissions of nitrogen oxides from diesel engines of over 130 kW and new fishing vessels are required to comply. Morevoer, as a consequence of research and development (R&D) on energy-saving technologies carried out by designers of machinery and fishing vessels and gear, there are signs that the fishing industry has begun to improve its fuel efficiency. Nevertheless, fuel continues to be the major cost of operation in capture fisheries and further refinements to fuel quality, such as lowering the content of sulphur oxides and particulate matter, could well lead to even higher fuel and lubricating-oil costs. This may have an even greater impact on the fishing industry in developing countries where mechanization continues to increase, although it will also strengthen the drive for fuel efficiency.
Bycatch and discards
The seriousness of the impacts related to bycatch and discards has been recognized
by the international community and in particular through the endorsement of the
International Guidelines on Bycatch Management and Reduction of Discards at the
Twenty-ninth Session of the FAO Committee on Fisheries in 2011. There is a range of
tools to manage bycatch and reduce discards, including technological measures to
improve the selectivity of fishing gear. The declines in the bycatches and discards in
many fisheries have mainly been the result of introducing effective gear modifications
and bycatch reduction devices.72 However, there remains concern about the impacts of
unaccounted fishing mortalities such as ghost fishing by abandoned, lost or otherwise
discarded fishing gear and the fact that such gear may also cause environmental
Furthermore, at the sixty-second session of the Marine Environment Protection Committee of the International Maritime Organization (IMO) in July 2011, Annex V of the International Convention for the Prevention of Pollution from Ships 1973/78 (MARPOL) was amended to provide a regulation for the loss of fishing gear that may be a substantial threat to the environment or the safety of navigation to be reported to the flag State, and, where the loss occurs in waters under the jurisdiction of another coastal State, to that State. This regulation is supported within guidelines for the application of Annex V currently under revision.
With continued exposure to rising fuel prices and little or no significant price increases
at the point of first sale for catches, capture fisheries will probably continue to suffer
declining profitability. Moreover, if resource abundance remains static, some bottom
trawl and dredge fisheries may become uneconomic (although passive gear and seine
net fisheries may be less affected). As demersal trawl fishing accounts for a significant
part of the total catch destined for direct human use, there could be an adverse affect
on global fish supply and food security, at least in the short term.
With medium-term forecasts indicating a high likelihood of further and steady increases in fuel prices, as indicated by the International Energy Agency, the future of the fishing industry is challenging. An increase in sulphur-oxide-emission control areas (the most recent being adopted by the IMO in 2011) would add to the cost of fuel for vessels operating in such zones.
The fishing sector will no doubt strive to lower its fuel consumption, reduce its carbon footprint, and decrease ecosystem impacts. Although the continuation or expansion of fuel subsidies would reduce immediate costs, this is less acceptable. To help the fisheries sector achieve significant and permanent reductions, governments will most probably strengthen their fisheries sector energy policy and create an enabling environment in which fishing industries can rapidly and comprehensively adopt low-impact fuel-efficient (LIFE) fishing technologies and practices. The development and adoption of such fishing techniques offer scope for maintaining the long-term profitability and sustainability of capture fisheries worldwide.
With fossil fuels remaining the dominant energy source, pursuing energy efficiency in capture fisheries may generate benefits by reducing operating costs, controlling GHG emissions and minimizing environmental impacts within the aquatic environment. However, the success of this transition will depend heavily on the response of governments to the implementation of international conventions together with a positive reaction from the engine manufacturing sector, fuel-oil and lubricating-oil producers and the fishing industry (including the manufacturers of fishing gear). This could lead to the development and application of suitable and acceptable measures to conventional fisheries and create an appropriate catalyst for change in the behaviour of fishers. Of equal importance are initiatives such as pursuing the modification of existing gear types and the development of lowresistance towed fishing gear with minimal impact within the aquatic environment. In some cases, it may be necessary to switch to completely new gear types or practices in order to enable LIFE fishing.
However, to be effective, this would require global R&D priorities to be established and work undertaken in support of the development and uptake of LIFE fishing. These include:
- promoting and funding studies of cost-effective gear designs and fishing operations, including the establishment of technology incubators and other publicprivate sector initiatives to commercialize economically viable, practical and safe alternatives to conventional fishing methods;
- analysis and review of best practice operations across fisheries;
- improvement of technical ability among fishers;
- establishment of appropriate incentives;
- industry compliance with international conventions;
- execution of robust but flexible fishery policies that support the transition to alternative technologies.
Finally, close cooperation between the fishing industry, scientists, fisheries managers and other stakeholders will be fundamental to the development, introduction and acceptance of LIFE fishing technologies.