Effects of Seining Or Purse Seine Fishing in Marine Biodiversity
Princess Ganapin Cahilig
Bataan Peninsula State University(Bagac Campus)'
Abstract
Seining or fishing uses a seine or mesh is commonly used to determine species distributions and to estimate species richness of small fishes in littoral zones of lentic habitats. However, little guidance exists on the seining effort requires to properly estimate species richness for lentic habitats. Captured efficiency of a beach seine varies greatly depending on aspects of the littoral zone habitats and fish communities. Seine fishing in a two-species fishery is viewed as a semi-Markov process. Activities of a vessel during a fishing day are assigned to five states: searching, successfully setting on either species, and unsuccessfully setting on either species. Searching for fish schools is assumed to be a Poisson process. Transition probabilities are defined in terms of species densities in the fishing area, the chance that a sighted school is captured, and the chance of relocating an escaped school. Waiting time in the search state is determines by school density in the fishing area and search rate of the vessel. Waiting times in the remaining states depend on numerous factors such as vessel characteristics and weather. With results from renewal theory, expectations of the number of successful sets on each species during a time interval of arbitrary length are approximated. Numerical comparison with exact results from a simpler fishing model indicates the approximation from renewal theory for the expectations to be excellent. Several examples are given to demonstrates the model's utility. It can be used to develop abundance measures for the two species which account for temporal changes in efficiency of the vessels, dead time after a school is encountered while the vessel is not searching, and the fact that two species are being exploited simultaneously. Our objective was to determine the seining effort needed to estimate species richness for three Wyoming reservoirs. We conducted a simulation study based on seining data collected from three reservoirs to define the sampling effort needed to estimate species richness. Eighteen to thirty-eight seine hauls were needed to attain a 90% probability of detecting approximately 90% of the species present, and 42'66 seine hauls were needed to attain a 90% probability of detecting all of the species present. Seining appears to be an effective tool for estimating species richness in Wyoming reservoirs, even though considerable effort is required for precise estimates. We specifically evaluated whether seining was sufficient for fish community assessment.
Keywords:Purse Seine,Gears,mesh,Seiners
Introduction
Seine fishing or Seine haul fishing is a method of fishing that employs a seine or dragnet.Such gears include all kinds of trawl like(galadgad,Norway),purseine (pangulong),Danish seine (hulbot-hulbot,pahulbot-hulbot,likisan,liba-liba,patangko ,palisot,bira-bira,buli-buli,lampornas and many others.).A seine is a fishing net that hangs vertically in water with its bottom edge held down by weights and its top edge buoyed by floats.Seine nets can be deployed from the shore as a beach seine ,or from a boat.Boats deploying seine nets are known as seiners.Seines have been used widely in the past,including by stone age societies.For example,with the help of large canoes,pre European Maori deployed seine nets which could be over thousand meters long.The nets were woven from green flax,with stone weights and light wood or gourd floats and could require hundreds of men to haul.American native Indians on the Columbia river wove seine nets from spruce roit fibers or wild grass, again using stones as weights.For floats they used sticks made of cedar which moved in a way which frightened the fish and helped keep them together.The effects of removing too many fish can dramatically alter the populations of other predator species in the marine food web.Many species of marine wildlife are threatened by the competition with fishing operations,sharks,seals,dolphins,whales,seabirds,turtles,and many more.Millions of animals become the victims of entanglement,incidental capture and death in fishing gear.Food availability is a critical factor which limits the distribution and numbers of animal populations in the seas.The relationship between predator and prey can be disturbed by intensive commercial fishing.This can affect marine biodiversity in ways that may be irreversible.Population crashes in some seabird populations,for instance have associated with changes in abundance and availability of fish stocks.The tendency to fish further down the food food web could be indicative of the possible collapse of more fishing grounds.There is great difficulty nowadays in sustaining global fisheries production at around 82 million tons.In resppnse to declines of commercially valuable stocks of bigger,slower growing species,commercial fishing fleets have turned to "fishing down the food chain",targeting increasingly large quantities of smaller species of fish with less commercial value.Such fish ,called small-pelagic fish,are highly mobile shoaling fish that dwell near the ocean's surface and they play critical role in the marine foodweb.Purse seine or Danish Seine fishing also has a potential to indirectly change ecosystems such as coral reefs ecosystems.When plant-eating fish are removed from the coral reef ecosystems,grazing is reduced,allowing the algae that coexists with corals to flourish and potentially take over,especially if the water contains high levels of nitrogen.Despite the blatant warning signs,new industrial-scale fishing vessels are rolling out of shipyards equipped with more efficient ways to find,catch,process fish and adding to the collosal armada of big boats that are still fishing using nets.Due to the overfishing amount of trash fish catches increase and which is very important for fish processing industry to produce fish meal for that they are releasing more fishing fleet in sea and which are capable to catch fish from deep sea and the fleets are very much modernized for that they can go to the distant water.Over-capitalization of the industry which has led to thr buildup of excessive fishing fleets,particularly of the larger-scale vessels catching too many fish.This has led to widespread overfishing (with many fish stocks at historic lows and fishing effort at unprecetended highs).Fish are harvested at an average size that is smaller than the size that would produce the maximum yield per recruit.The total yield on fishery is therefore less than it would be if the fishing mortality rate,or percent of the stock removed each year,was lower.Fish are found to be smaller than it's known size maturity.Fishing using nets is indiscriminate.Any fish which get in the way of the net will be caught in it if they are too big to get through the mesh.For every one tonne of prawns caught,three tonnes of other fish are killed and thrown away.Twenty thousand porpoises die each year in the net of salmon fishermen in Atlantic and Pacific oceans and tens of thousands of dolphins are killed each year by tuna fishermen.Some sea fish live in the upper parts of the water.They are called "pelagic"fish,and they are caught by drift netting.This is where a net suspended from floats are stretched fron two boats so that fish swim into it.Fish are unable to swim backwards,so once they are caught in the net there is no escape unless they are too small to fit through the net's mesh.Many population of marine wildlife species are threatened or have become endangered,to such an extent that some,like the albatross,are sliding toward extinction.After a catch is hauled aboard,the non commercial marine life,is culled out and thrown back,known as "bycatch".Bycatch is not limited to unwanted fish species.It can be fish with no commercial value,juveniles of marketable species,all types of marine life including whales,dolphins,porpoises,fur seals,albatrosses and turtles are killed as baycatch.The Instute of Marine and Antarctic Studies (IMAS),which advises the Government on stock sustainability matters,has not indicated any concerns for the sustainability of flathead.The main potential negative impact of Danish seining on living resources is when too many small sized organisms and non-target species are caught and sometimes discarded.Such impact can be mitigated by using larger meshes in the bag and/or specific devices being installed on the seine for reducing the capture of small and unwanted organisms.Danish seine vessels have been operating in Tasmania since the mid 1930s and the method used today is largely unchanged from the original.Two species of fish are targeted,tiger flathead (Neoplatycephalus richardsoni) and southern school whiting (sillago flindersi).All catch is landed whole .Water depth fished are approximately between 10 to 90 meters.However,there's a plan to totally ban "hulbot-hulbot" considering that this is a dentrimental to the habitat of fishes and other aquatic resources.Likewise,such devices may only be used outside municipal waters if the permit is issued by the BFAR director,in consultation with the National Fishery Aquatic Resource Management (NFARMC) and the concerned local government executive to the same institutions fir research,educational and scientific purposes.Violators face a penalty of imprisonment from six months to two years or a fine of Php.5000.00 per superlight,or both,depending on the court's discretion,without prejudice to the confiscation of their devices including the fishing vessel,nets and other gears.
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Literature review
Seine fishing can be harm the aquatic area.As I research,the Seine fishermen works like this;first step they leave dhan pole and buoy and steam away fast,paying out the warp from the portside then when port side warp is almost out,then the net goes in the water.When the net is in the water and getting ready to attach to starboard side warp,steaming away from net paying out starboard side warp then pick up the dhan pole and buoy then both warps are secured to the vessel.Now they are steaming the net is towed along the bottom for a short time and the vessel is steaming slowly to close the net.The type of gear is very light and does not plough into the bottom,but rather skips over the substrate,scaring and herding the fish into the net. Maritime anthropologists often have argued that different fishing strategies or skipper skills partly account for variability in fishing success within a fleet, but statistical support for such strategies has been difficult to acquire. This article analyzes a mixed species, tropical seine fishery in south central Luzon, Philippines where boat size is similar and electronic fish-finding gear, mechanized hauling, and formal navigational training of skippers are absent. What does a seine catch?
Fishermen use purse seines to catch species that gather in large groups or 'schools' in surface or mid-ocean waters ' including sardines, anchovy, herring, mackerel, menhaden, squid, and tuna.
We review the qualitative and quantitative evidence for different fishing strategies in this fleet and then examine the degree to which these strategies account for differential fishing success. We suggest that one way to detect the existence of different seining strategies is to measure the locations fished, number of trips and type of species caught per time period. In fisheries where one is concerned to determine the degree to which fishing strategy accounts for variability in catch, we suggest that defining fishing success as mean catch per trip is more useful than conventional definitions of total catch over a season. The advantage of measuring fishing success as mean catch per trip rather than total catch is that it controls for effort, thereby allowing one to discern more clearly the variables that explain fishing strategy.Drawing in the net The warps are winched in simultaneously,resulting in the net being drawn to the vessel with the catch guided to the conded.Close up of the wing mesh,hauling the net.A small catch of whiting conded.Catch is mainly whiting…approximately 200 kilograms.The whole operation takes about 1-1.5 hours.Seine fishing pushed many commercially important fish populations into steep declines.Some commercially important stocks are in such a critical state that all fishing has been shut down or sharply curtailed.There are various causes of overfishing/Seine Fishing such as; the rapid increase in demand for fish and fishery products leading to increase fish price faster than prices of meat,rapid advance of fishing technology,the dramtic increase of use of destructive fishing technicques and gear,using smaller mesh net,more time effort and money in fishery sector,open access to fishing in most fisheries and non enforcement of modern management regulations,the common property nature of the fishery resources,resulting in unregulated access to many of the resources and subsidies from governments to fishing industry.During pass few decades,the large increase of demand especially for marine fish and marine fishery products leading to increase fish price faster than prices of meat. Our small mesh seines (for bait sized fish such as minnows, shiners, shad, etc.) are fully hung with a generous amount of soft non-abrasive nylon netting. Our superior netting is strong, yet soft enough to reduce injury to delicate fish. Our seines are completely assembled with floats and leads and are ready to use. Fish prices are increasing that encourages people to do fishing because of high technology,high price and high profit.As a result,fisheries investments have become more attractive to both entrepreneurs and governments,much to the detriment of small-scale fishing and fishing communities all over the world.Marine fish are the major source for fatty acids with other types of nutrients like ca,Vitamin A ,and Vitamin D that helps to improve human health with a human desirable flavor and reduce blood cholesterol level in human body.Hence day by day the demand for fish products is increasing remarkably and it leads to overfishing. Efficiency varies among gears, among habitats, among species, and even among sizes of the same species. Gears for which efficiency is highly variable among species or sizes of fish are termed selective. Gears that capture a wide range of species and sizes equally are referred to as non-selective. In practice virtually all gears/methods vary to some degree in efficiency among species and sizes of fish. Most of thr problems associated with overfishing have been caused in the last 50 years by the rapid advances in fishing technology Demand for seafood and advances in technology have led to fishing practices that are depleting fish and shellfish populations around the world. Fishers remove more than 77 billion kilograms (170 billion pounds) of wildlife from the sea each year. Scientists fear that continuing to fish at this rate may soon result in a collapse of the world's fisheries. In order to continue relying on the ocean as an important food source, economists andconservationists say we will need to employ sustainable fishing practices.. A small purse seine, 250 ft. long and 23 ft. deep, and two 14 ft. purse boats to fish it in shallow estuaries for menhaden (Brevoortia) are described. The seine is made of No. 6 nylon in the two wings and heavier No. 15 nylon in the center bunt. Mesh is 1 3/8 in. bar. Purse boats have a 7 ft. beam and 2 ft. of freeboard, and are built of 1/4 in. marine plywood and seasoned oak ribs. A 40 hp outboard motor mounted in a center well powers each boat. Boats and seine are portable (on trailers) and can be used any place where launching sites are available. Over 40,000 menhaden were caught and marked with internal ferro-magnetic tags over a 3-year period. Boats and seine also could be used to capture other schooling species. Consider the example of the bluefin tuna. This fish is one of the largest and fastest on Earth. It is known for its delicious meat, which is often enjoyed raw, as sushi. Demand for this particular fish has resulted in very high prices at markets and has threatened its population. Today's spawning population of bluefin tuna is estimated at 21 to 29 percent of its population in 1970.Thye fishing vessels are replaced by huge factory ships which are able to stay out at a sea for weeks at time.These factory boats have all the equipment necessary either to freeze or tin fish caught by their hunting ships,so that they need to return to base only when theirs holds are full.With the introduction of new factory boats,there was a 7 percent growth in catches every year .As catches have gradually become smaller,so the mesh sizes used in fishing nets have decreased,allowing smaller and smaller fish to be caught.Many of these are too small to be used as food so they are crushed to be made into either animal food ot fertilizer.The dramatic increase if use of destructive fishing technicques and ger worldwide destroys fisheries,marine mammals and entire ecosystem.Along with the growing fleet come more fishing nets in the water,some of which are very non selective.It is impossible to catch only the desired fish species,this harvest of non-target species is called bycatch.Bycatch constitute all of the animals that are caught but not wanted or used or acquired to be discarded by management regulation(SOMMA 2003).This includes endangered or protected species,fish that are legally too small to catch,or those that have to commercial value.It is estimated that bycatch makes up the quarter of the fish caught,but most of tge bycatch are dead before being thrown back to the water.Equipment such as purse seine net,longlines,gillnets and trawls are especially harmful to the environment.They tend to catch juvenile fish and other non target marine animals.Gill nets are also dangerous as many are discarded in the water,yet continue to kill fishing what known as ghost fishing.Trawls are especially dangerous,they produce significant bycatch while damaging the environment as they are dragged along the seafloor.Fishing using nets is indiscriminate.Any fish which get in the way of the net will be caught in it if they are too big to get through the mesh.For every one tonne of prawns caught,three tonnes of other fish are killed and thrown away.As the time goes by the number of fishermen has more than doubled.In most developing countries,the poor have no choice but to glean the last of the resource.Free and open access encourages overfishing as fishermen tend to catch as much fish as they can without taking care to maintain the fish stock.Today,there isn't a fishing region in the world that does not suffer from fisheries management decisions designed to satisfy short-term economic or political objectives rather than protecting the marine environment and conserving fish populations.Indeed,in many countries,governments have played an important part in fueling the expansion of execessive fishing capacity and over exploitation by providing lucrative subsidies,taxpayer funded handouts.A world bank study estimates that subsidies,although declining are still worth a total of up to $20 billion a year.Fisheries subsidies sometimes provide jobs in poor coastal regions and help countries expand their fishing industry.However,most of the time,the same subsidies encourage companies to develop high-tech fishing and thus overfishing.There are two types of overfishing the first one is growth overfishing. Since about that time, commercial fishers have caught bluefin tuna using purse seining and longlining. Purse seine fishing uses a net to herd fish together and then envelop them by pulling the net's drawstring. The net can scoop up many fish at a time, and is typically used to catch schooling fish or those that come together to spawn. Longlining is a type of fishing in which a very long line'up to 100 kilometers (62 miles)'is set and dragged behind a boat. These lines have thousands of baited hooks attached to smaller lines stretching downward.
Both purse seining and longlining are efficient fishing methods. These techniques can catch hundreds or thousands of fish at a time.Growth overfishing occurs when animals are harvested at an average size that is smaller than the size that would produce the maximum yield per recruit.The total yield from the fishery is therefore less than it would be if the fishing mortality rate or percent of the stock removed each year was lower.In such case less fishing would produce higher landings. Small-scale fisheries generally contribute about half to the amount of fish consumed directly by humans (FAO, 2003). Fisheries management includes different management measures. Among these are technical regulations on fishing gears in order to obtain the overall goal of high sustainable yield in the fisheries.Growth overfishing still reduces the potential yield from a fishery and thus the economic and other benifits that could be obtained from the stock.For example:Heavy fishing removes the larger animals and does not give young lobsters a chance to grow their potential size.The lower fishing pressure on the offshore fish stocks allows more fish to grow to a larger size,but even there the size range is much reduced from the early days of the fishery.The second type of overfishing is Recruitment overfishing,the rate of fishing above which the recruitment to the exploitable stock become significantly reduced.This is characterized by a greatly reduced spawning stock,a decreasing proportion of older fish in the catch,and generally very low recruitment year after year.Recruitment refers to the time when young fish become big enough to be caught.Recruitment overfishing means so many adults fish have been caught that there are no longer enough young adults fish to maintain the population.When fishing pressure is too heavy to allow a fish population to replace itself.Occurs in circumstances where an increase in fishing effort from current levels will cause a decline in recruitment to a fishery.Recruitment overfishing can be brought about by;reduction of the spawning stock (which may become so small as to produce a limited number of eggs and hence of recruits),and coastal environment degration,which affects recruitment through its effects on size and/or suitability of nursery areas.Preventing recruitment overfishing is not as some think a matter of letting each female spawn at least once. The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO in preference to others of a similar nature that are not mentioned. Sustainable fishing guarantees there will be populations of ocean and freshwater wildlife for the future. Aquatic environments are home to countless species of fish and invertebrates, most of which are consumed as food. (Others are harvested for economicreasons, such as oysters that produce pearls used in jewelry.)Seafood is respected all over the world, in many diverse cultures, as an important source of protein and healthy fats. For thousands of years, people have fished to feed families and local communities. There are ways to fish sustainably, allowing us to enjoy seafood while ensuring that populations remain for the future. In manyindigenous cultures, people have fished sustainably for thousands of years. Today's sustainable fishing practices reflect some lessons learned from these cultures. The number of fish available for capture must be known in order to calculate catchability or gear efficiency. Some studies estimate catchability by releasing a known number of marked fish into the sampling area prior to sampling. If the assumptions are made that catchability is equal for marked and unmarked individuals and that all of the marked individuals are available for capture, then catchability is equal to the proportion of the marked fish that are captured. Other studies employ some means of collecting the remaining fish following the sampling (i.e. poisoning or draining the area). Still others estimate abundance using removal or mark-recapture methods, that use the rate at which the catches decline, or that the proportion of unmarked fish in the catches decline, to estimate the size of the population.
Gill nets are highly selective and there is a large body of literature addressing the relationships between mesh size and fish size. There are two aspects to the selectivity of gill nets. First, like all passive gear, their efficiency is directly related to the probability that a fish will encounter them. Gill nets are not effective for catching sedentary fishes. Catchability increases as movement of the target species increases. In addition to behavioural differences (sedentary versus roaming), distance traveled can be influenced by swimming ability, which, for a given species, is often related to size. Consequently, some researchers have used fish size to estimate the relative probability that fish of various sizes will encounter the nets (Rudstam et al. 1984; Spangler and Collins, 1992). Seasonal differences in fish movement can be very important in determining the likelihood of encounter. Neumann and Willis (1995) reported that the catch-per-uniteffort of northern pike (Esox lucius) in gill nets was lowest in winter and highest in spring. Changes in movement in response to weather, or any other stimulus, can influence encounter probability. There is a high encounter probability for gear sets along spawning migration routes during spawning season. Overfishing is a major environmental problem and is discussed in reducing numbers. Some people often ask them to describe various types of fishing gear and explain which ones cause the most destruction to the ocean. Another frequent question is why our seafood ratings for a particular species differ depending on the fishing method used. To help answer these questions, we decided to create a Fishing Gear 101 blog series. In this series, we describe how common types of gear work, what they catch, how they affect ocean wildlife and habitats, what technologies or regulations can help lessen the gear's negative effects, and what we see as the path forward to ensure healthy oceans in the future. Floating object purse seining takes advantage of the fact that open-ocean fish, like tuna, will congregate around floating structures ' whether natural or artificial. In recent years, tuna fishermen are designing and strategically placing more and more artificial structures, called fish aggregating devices or FADs, in the ocean to attract tuna. They make the FADs from various materials, such as ropes, lines, and netting. Fishermen may anchor the FADs to the seafloor or let them drift in the water. The drifting FADs have location transmitters so that fishing vessels can find them. And often times they will have sonar devices that transmit information to the fishing vessel about the amount of fish gathered around the FAD. Once a significant amount of tuna has gathered around the FAD, fishermen will set the purse seine to capture everything underneath it2. While this is an efficient way to capture tuna, as you will learn below fish aggregating devices have many potential negative effects on the ocean. ECOLOGICAL ISSUES WITH PURSE SEINE FAD (AND OTHER FLOATING OBJECT) SET,Catch juvenile tunas, including juvenile bigeye which is overexploited in some regionsPurse seine associated sets, which are sets made on floating objects, including Fish Aggregating Devices (FADs), catch primarily skipjack tuna and also catch juvenile bigeye and yellowfin tunas. While removals of juveniles risks recruitment overfishing by reducing spawning potential, purse seine mortality of juvenile tunas is not an unstainable practice, per se. Instead, balancing fishing mortality across all age classes of a single stock might be a more sustainable practice than just removing the large older individuals. Harvest strategies[1]in theory can be designed to account for purse seine juvenile removals and longline adult removals to achieve ecological and socioeconomic stock-specific management objectives. There is no ecological basis to argue for allocating adult bigeye and yellowfin tuna resources to the longline sector, and minimizing juveniles of these species to purse seine sector, but there may be a socioeconomic basis for this.
In addition to a lack of controls on the number and density of drifting FADs, none of the four tropical tuna RFMOs currently obtain information on the number, locations and designs of FADs, including through observer data collection protocols and less-certain logbook records. Some have adopted requirements for their Parties to prepare FAD management plans.As a result, currently, FADs are largely unregulated and unreported (two of the three elements of IUU fishing). There is a need to expand the information collected in regional and domestic observer programs from purse seine vessels to include fields for FAD deployments, FAD recovery (rare), FAD loss, various fields for design elements, equipment and identification markings. And the tuna RFMOs should require each FAD to have a unique ID and unique electronic signature, to report the position of their FADs (companies should be required to track and control all their FADs), and all FADs should be required to be registered with the relevant RFMO. If these measures were required, then surveillance programs could remove FADs that lack requisite compliance with identification and unique electronic signature as they would constitute illegal fishing gear.
In addition to managing purse seine FAD sets ' such as through input controls (number of sets on FADs per year, bigeye TACs) and monitoring and controlling the number of drifting and anchored FADs (discussed above), there may be technological measures to reduce the juvenile tuna catch. Over the past few years ISSF has spearheaded allocating funding for this research area, primarily to members or colleagues of the ISSF science committee. To date, a viable gear technology solution has not been identified. Given sufficient investment, a change in gear design (e.g., reduce the depth of the appendage on FADs) or methods (reduce the depth of the seine, the BET and YFN tend to be at the bottom of the aggregation, or manage the time of day of sets if SKJ are in the aggregation at different time of day from BET) might work to avoid catching bigeye in FAD sets. Seine associated sets catch sharks, mainly oceanic whitetip and silky sharks ' about 1% of the catch is sharks. Sharks are also entangled in FAD appendages. Relative to other gear types, such as longline and gillnet, this is likely a relatively small source of shark fishing mortality. Use of FADs designed with non-entangling appendages (e.g., use sheets of material instead of webbing) should help. ISSF has been a primary funder of research to try to find ways to get sharks out of the seine, or avoid including them in the aggregation, and as with avoiding juvenile bigeyes in associated sets, so far no solutions have been defined, but perhaps a viable gear technology solution is around the corner, given additional investment in R&D. Free school sets catch a mix of skipjack and yellowfin, while associated sets catch predominantly skipjack, with relatively small volume of juvenile yellowfin and bigeye. As a result, reducing purse seine associated sets and increasing free school sets will increase pressure on yellowfin stocks. Reducing FAD fishing and replacing effort with free school sets should reduce pressure on bigeye stocks but likely will increase pressure on yellowfin tuna stocks. Robust stock-specific harvest strategies are needed for all three tropical tuna species to account for potential changes in purse seine fishing strategies. A ban on drifting FADs might result in many positive ecological and socioeconomic consequences ' turning canned light meat tuna into a lower volume, higher value product, and could avoid adverse effects from increased yellowfin pressure and a higher carbon footprint if adequate management measures were in place and compliance was high. A ban on anchored FADs might displace effort to more sensitive coastal systems. However, a drifting FAD ban is not the only route to address ecological sustainability issues. FADs are a fishing gear type that requires adequate management, just like any other fishing gear. It is possible that purse seine FAD fisheries could address known and potential ecological sustainability problems at some point in the future if appropriate management measures were adopted and compliance was adequate. It is possible that purse seine FAD fishing could unconditionally pass an assessment against the Marine Stewardship Standard (MSC) and be MSC certified, and strong supply chain traceability measures could prevent IUU product from entering the supply chain from these MSC-certified fisheries. Lots of ifs. But this is a similar situation for many other marine capture fisheries.
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Conclusion
This study describes that attempt to regulates the beach seine activities have met with little success. To face this situation, decisions making to seek supports from the sustainable fisheries program would be useful. Thus the involvement of the fisheries communities in the process of setting up regulations for the use of the beach seine is an appropriate way, especially in regard to the decreased the cost of such experiments which may have some financial limitations for researchers. Proper management measures could included gears selectivity and mesh size regulation. Selective fishing methods should be encouraged which include standardization of height and mesh sizes in beach seine nets. Based on the results from this research, we found that the height and mesh sizes of beach seines may have an important influence on catch properties. However, more research must be done in this regards.
Catching so many fish at a time can result in an immediate payoff for fishers. Fishing this way consistently, however, leaves few fish of a species left in the ocean. If a fish population is small, it cannot easily replenish itself through reproduction. Overfishing is a major environmental problem and is discussed in reducing numbers.
Taking wildlife from the sea faster than populations can reproduce is known as overfishing. Purse seining, longlining, and many other types of fishing can also result in a lot of bycatch, the capture of unintended species. Longlines intended to catch bluefin tuna, for instance, can ensnare birds, sea turtles, and other fish such as swordfish.
Another fish species that has been overfished is Chilean seabass, sometimes called Patagonian toothfish. In the 1990s, this fish became extremely popular in restaurants across the United States and other countries, causing an increase in demand. The fish is native to the South Pacific and South Atlantic Oceans, typically caught by longline in international waters. Fishing in this area is regulated by international agreements, which are very difficult to enforce. Illegal fishing'in this case catching fish in numbers high above internationally established limits'became widespread. The number of fish caught and the average size of the fish decreased, leading to even higher prices and greater incentive for illegal fishing. Chilean seabass is a long-lived (up to 50 years), slow-growing fish. Smaller seabass are likely younger, and may not have spawned yet. As fishers caught smaller seabass, healthy replenishment of the population became unlikely. When fishermen use seines to catch a tightly-knit school of a single fish species, they catch a low proportion of non-target species (or bycatch). And in most cases, purse seines do not contact the ocean bottom, so they cause no damage to ocean habitats. The purse seine fisheries for U.S. Atlantic Herring, Atlantic Mackerel and Pacific Sardine, for instance, cause minimal harm to other ocean animals or the environment. That's one of the reasons they are rated green. What can be done to lessen the negative effects of this fishing gear?
Many free-school purse seine fisheries cause minimal harm to non-target ocean animals and habitats, so they do not require measures to reduce negative effects.
In those purse seine fisheries that have bycatch concerns, currently, the best way for fishermen to minimize harm to non-target animals is to avoid fishing in areas where vulnerable ocean wildlife are spotted or likely to be, and to release the animals as carefully as possible, if they do catch them. Some scientists are researching possible gear modifications or technologies ' for instance, bycatch excluder devices, like those used in trawl fisheries ' that could help reduce bycatch in purse seine fisheries. Sometimes part of the catch (i.e. excess catch) is deliberately released from the tightened net instead of landing it, in a process called 'slipping'. Despite the fact that these fish are released alive, high death rates can occur following release as a result of injury and scale damage incurred. Possible ways to reduce these wasteful death rates are for fish to be released before the net is tightened and reducing the practice altogether.
Fish are likely to experience fear as they try to out-swim the net moving towards them, and as they are finally encircled. Sometimes fish are deliberately scared by, for example, high speed chase boats used to herd the fish. Once the circle is complete, the trapped fish are confined in a shrinking space of water and become increasingly crowded. At a certain point, the constriction of space will prevent the fish from swimming as a school, when instead they will move as individuals. This is likely to be very stressful, and fish are liable to incur injury and scale loss from collisions with other fish and with the net walls. Stress levels of sardine caught in purse seines have been observed to be similar to peak levels reported elsewhere for acute distress, according to one study. The same study found that stress levels continued to increase the longer the fish remained in the net.
Fish can also receive further injury as they are transferred to the fishing vessel. Pumps can break fins and damage scales. In ramping, the seine net is hauled aboard en mass, causing fish to get crushed. In brailing, fish are transferred using a smaller brail net. Lower death rates and lower levels of 'physiological disruption' have been found in salmon transferred by this method as compared with ramping.
References
http://www.nmfs.noaa.gov/pr/interactions/gear/purseseine.htm
http://www.thefreedictionary.com/purse+seine
http://archimer.ifremer.fr/doc/00042/15278/12664.pdf
http://www.hoitokalastus.com/nuottaus_en.htm
http://www.newworldencyclopedia.org/entry/Fishing_net
www.pikexperience.com/'
http://www.nmfs.noaa.gov/pr/interactions/gear/purseseine.htm
http://www.nmfs.noaa.gov/pr/interactions/gear/gillnet.htm
http://www.nmfs.noaa.gov/pr/interactions/gear/bottomtrawl.htm
http://www.nmfs.noaa.gov/pr/interactions/gear/poundnet.htm
xt in here…