Many countries have set up ministries or government departments, often named
Ministry of Fisheries or similar, controlling aspects of fisheries within their
exclusive economic zones. Currently, there are four core categories of management regulating either input (including investment), or output in a fishery or fishing area. These management mechanisms operate directly or indirectly: Technical measures may include: • prohibiting devices such as bows and arrows, and spears, or firearms • prohibiting nets • setting minimum mesh sizes • limiting the average potential catch of a vessel in the fleet (vessel and crew size, gear, electronic gear and other physical "inputs" • prohibiting bait • limiting
snagging • limits on fish traps • limiting the number of poles or lines per fisherman • restricting the number of simultaneous fishing vessels • limiting a vessel's average operational intensity per unit time at sea • limiting average time at sea
Catch quotas Systems that use
individual transferable quotas (ITQ), also called individual fishing quota limit the total catch and allocate shares of that quota among the fishers who work that fishery. Fishers or fishery firms may then buy, sell or trade their allocated shares in addition to use. A large scale study in 2008 provided strong evidence that ITQ's can help to prevent fishery collapse and even restore fisheries that appear to be in decline. Other studies have shown negative socio-economic consequences of ITQs, especially on small-sclale fisheries. These consequences include concentration of quota in that hands of few fishers; increased number of inactive fishers leasing their quotas to others (a phenomenon known as armchair fishermen); and detrimental effects on coastal communities.
Elderly maternal fish Traditional management practices aim to reduce the number of old, slow-growing fish, leaving more room and resources for younger, faster-growing fish. Most marine fish produce huge numbers of eggs. The assumption was that younger spawners would produce plenty of viable
larvae. However, 2005 research on
rockfish shows that large, elderly females are far more important than younger fish in maintaining productive fisheries. The larvae produced by these older maternal fish grow faster, survive starvation better, and are much more likely to survive than the offspring of younger fish. Failure to account for the role of older fish may help explain recent collapses of some major US West Coast fisheries. Recovery of some stocks is expected to take decades. One way to prevent such collapses is to establish marine reserves, where fishing is not allowed and fish populations age naturally. There are 8 principles that should be considered as a whole in order to best manage a fishery. The first principle focuses on the finite nature of fish stocks and how potential yields must be estimated based on the biological constraints of the population. In a 2007
marine science study, results indicate there are significant benefits to the health and size of both
stock biomass and yield under timely and well-enforced management regimes. Similarly, other studies find the sensitivity of stock to management regimes. In
North Sea fisheries finds that fishing at the top of the "acceptable" ranges is many times more risky than fishing near the bottom, but delivers only 20% more yield. In addition there is growing evidence – and growing recognition by both fishery scientists and small-scale fishermen – that coastal
marine protected areas do favor the biodiversity and resilience of ecosystems nearby, significantly enhancing the density, biomass and size of commercially exploited species in local waters.
Ecosystem based fisheries management (EBFM) According to
marine ecologist Chris Frid, the
fishing industry points to pollution and global warming as the causes of unprecedentedly low fish stocks in recent years, writing, "Everybody would like to see the rebuilding of fish stocks and this can only be achieved if we understand all of the influences, human and natural, on fish dynamics."
Overfishing has also had an effect. Frid adds, "Fish communities can be altered in a number of ways, for example they can decrease if particular sized individuals of a species are targeted, as this affects
predator and prey dynamics. Fishing, however, is not the sole perpetrator of changes to marine life –
pollution is another example [...] No one factor operates in isolation and components of the ecosystem respond differently to each individual factor." In contrast to the traditional approach of focusing on a single species, the
ecosystem-based approach is organized in terms of
ecosystem services. Ecosystem-based fishery concepts have been implemented in some regions. In 2007 a group of scientists offered the following "ten commandments": • Report to Congress (2009): The State of Science to Support an Ecosystem Approach to Regional Fishery Management National Marine Fisheries Service, NOAA Technical Memorandum NMFS-F/SPO-96.
Ecosystem modelling software Ecopath, with
Ecosim (EwE), is an
ecosystem modelling
software suite. It was initially a
NOAA initiative led by
Jeffrey Polovina, later primarily developed at the
UBC Fisheries Centre of the
University of British Columbia. In 2007, it was named as one of the ten biggest scientific breakthroughs in NOAA's 200-year history. The citation states that Ecopath "revolutionized scientists' ability worldwide to understand complex marine ecosystems". Behind this lies two decades of development work by
Villy Christensen,
Carl Walters,
Daniel Pauly, and other
fisheries scientists. As of 2010 there are 6000 registered users in 155 countries. Ecopath is widely used in fisheries management as a tool for modelling and visualising the complex relationships that exist in real world marine ecosystems. == Issues in fishery management ==