Fisheries Resource Management Principles_rev

8/13/2019 Fisheries Resource Management Principles_rev

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Source: NSAP Training Module_NBA

Fisheries Resource Management Principles

1.1 EXPLOITATION OF THE FISHERY RESOURCES AND THE NEEDFOR MANAGEMENT

The utilization of aquatic organisms for food is probably as old as the human history itself. It

could have started with small groups or tribes that at first gather fishes or invertebrates drifted toshore. Then later, spear or harpoons and later hook-like utensils were discovered. In fact manyof the primitive methods of catching or entrapping aquatic organisms are still being practicedtoday especially in developing countries like the Philippines. We likewise have our share ofdevelopment. We have learned from industrialized countries the use of technology to improveefficiency in catching these organisms. Some of them are the deployment of long range fishingvessels, the use sonar and airplanes in detecting the prey, development of efficient catchinggears, and use of satellite technology.

The deficiency in this expensive technology is also overcome by deployment techniques suchas fleet operation. In the Philippines, for example, most fishing companies have continued toincrease their catching efficiencies by compartmentalizing their fleet operation. There are

assigned vessels to do the task of fish searching alone. This search boats are the only onesequipped with sophisticated electronic equipment. Once schools of fish are detected thecatcher boats are contacted and guide towards the school. Carrier boats are the only onesplying the fishing ground and the homeport carrying ice and food supply to the fishing groundand the catch to the homeport. In this manner the movements of the vessels are very limited,reducing overhead cost and increasing profit.

Not all aquatic organisms are directly used as food, rather some of them are utilized in the formof fish meal, refined into or mixed to become animal food or in extreme cases as plant fertilizer.

A significant amount of the products from the water are likewise used in technology, cosmetics,and pharmaceuticals. Products used by humans from the sea are normally of animal origin.The direct use of phytoplankton has been tried but were found to be not yet economically

feasible. The humans, therefore, are using mainly the secondary consumers.

We will learn later that exploiting our aquatic resources is not bad at all. What is unacceptableis overexploiting them. Human history has shown that we have formerly regarded our aquaticresources, especially the marine or ocean resources, as inexhaustible. We have allowed ourseas to be accessed by almost everyone. We have improved on the simple hunting techniquesof our ancestors and constantly developed our catching methods to access bigger and alwaysbigger aquatic resources. Although the consequences were expected by many, no concertedeffort was exerted to limit the catching rates or simply manage the remaining resources. Ourreaction may be a bit delayed but we are still in a position to mitigate the effects and preventfurther damage.

The need for fisheries resource management has been recognized even during the middle ofthe last decade. Manuals, books and short articles have pointed to various causes ofoverexploitation and recommended methods to evaluate their effects and offeredrecommendations to improve the situation. The focus has always been on the catch and how tolimit the harmful effects of catching on the resources. And most often than not, the aim wasalways to further increase or at least maintain production. Though the need for managementwas recognized, the approach was focused on the fish as commodity. It is only recently, whenthe focus has somewhat changed and was more on the fish as part of the ecosystem. It is on


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this context that we will try to learn the different approaches and strategies of managing thefishery resources.

1.2 GOALS AND OBJECTIVES OF FISHERY RESOURCESMANAGEMENT

The overall goal of fishery resources management is the sustained use of marine and fishery

resources. However, in practice, what we have achieved so far are just reaching decisions thatare mere reaction to problems created by inappropriate use or even misuse of these aquaticresources. Cochrane (2002) suggested that this goal can be subdivided into four subsets. Thesustained use of the fishery resources can be attained by maintaining the target species at orabove the levels necessary to ensure their continued productivity (biological) and minimizingthe impacts of fishing on the physical environment and on non-target associated and dependentspecies (ecological). Optimum benefit from the fishery is attained by maximizing the netincomes of the participating fishers (economic) and maximizing employment opportunities forthose dependent on the fishery for their livelihoods (social).

We see obvious conflicts among these goals. We know that maximizing net income will lead todepletion of commercially valuable species. This was what happened when mechanization and

employment of electronic equipment to efficiently capture fishes has increased fishing pressureand harvested world fish stocks at a very fast rate. It ended up with the collapse of many of theworlds large fish stocks. By maximizing employment opportunity from the fisheries we run therisk of reducing the individual income of each fisher. This is basically what happened to thesustenance fisheries in many of the third world fishing nations.

Striking a balance among these goals may not even be the best solution. The resource systemmay in fact dictate the preference. Biological and ecological goals may take the center stage fora community managing a marine habitat resource dedicated to tourism. Economic goal may bethe prime intention for a group of fishers exploiting a predominantly pelagic fisheries. And socialgoal may be the main consideration for a community managing a marine protected area. Inshort, all the four subsets may be present but one or two among them may be given preference.

By realizing and envisioning the reference a more precise operational objective can beformulated. This may be in the form of a target, say a certain percent increase in the catch byhook in line fisher in two years, or a decline in the incidence of illegal fishing in one year, or anincrease in the income of municipal fishers after five years. FISH Project has an operationalobjective of increasing the fish stocks by 10% from year 2004 to year 2010. An operationalobjective has both the element of a measurement and a reference point. It thus becomes asimple foundation for developing fisheries management strategies.

1.3 SOME BASIC FISHERIES RESOURCE MANAGEMENTCONCEPTS

1.3.1 THE STOCK AS A MANAGEMENT UNIT

To manage any resource it is obvious that the management unit is known and the processesare identified and can be quantified. For living resources found on land, the simplest way to dothis is to define the boundaries and deal only with processes and events that occur within theconfines of these boundaries. Definitely, it is difficult even just to imagine a management unit


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for a body of water and much more to single out the processes involved. Thus it is almost animpossible task to quantify these processes.

Russel (1931) came up with a simple idea to define the management unit. In the process, hewas also able to explain the factors causing the management unit to increase or decrease.Russel used a rectangle to depict the stock, his term for the management unit. The stock maybe used to define a group of aquatic organisms, say a particular species of fish. It may also beused to define a group of organisms composed of different species of fish or all organisms

constituting a particular ecosystem. Stock, therefore, may be used to designate a school ofgalunggong in Manila Bay. It may also be used to collectively describe the entire living aquaticorganisms in Tubbataha Reef in Palawan.

First of all, Russels idea is for us not to worry about the boundaries of our chosen stock but tofocus more on the processes that influence the stock. And second, it allows us to just focus ourattention to the major processes and, for the time being, forget about the complexities of theminor processes involved.

1.3.2 RUSSELS AXIOM

A stock may be confined to a specific body of water, say a lake, a bay, or an ocean. Its size or

biomass will depend upon a number of factors. The factors can be divided into two majorcomponents. One component will cause the stock to increase and another will cause it todecrease.

Obviously, a stock increases in biomass because each individual member is growing. Added tothis, the stocks biomass will further increase because new individuals are born. On the otherhand, death of individuals may cause the stock to decrease.

In nature, these reciprocating components can usually strike a balance. The concept can besimplified by a diagram which depicts what we call Russels Axiom :

Figure 1. Russels axiom applied to an unexploited system.

Increase in the stocks biomass is brought about by growthand also through the birth of newindividuals, from hereon to be called recruitment. On the other hand, decrease in stocksbiomass is caused by natural death. Fishes and other water organisms will die of old age,ailment or be eaten by others.

This specific example applies to lakes and natural ponds, which we can call as closedsystems. A closed system refers to a body of water that is physically isolated from other bodiesof water

Most of the time we will be dealing with an open system. As the name implies, they are waterbodies physically connected to other bodies of water providing opportunities for the swimmingorganisms to move from one to another. On both sides of the diagram we can, therefore,

Growth

Recruitment

Natural death


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introduce migration, and assign immigration to indicate increase and emigration to indicatedecrease.

However, for our purpose let us chose to deal with what we call a steady stateand assume thatimmigration and emigration are equal. Both will cancel each other out, thus we canconveniently eliminate them from our equation.

It was mentioned earlier that in nature the reciprocating components tend to reach a balance.

Let us imagine a scenario wherein one subgroup of the stock becomes out of control andincreases its population at a very fast rate. Of course this population can not increaseindefinitely. In any environment, the available space and the amount of food are limited.Overpopulation, in all cases, will be checked by the lack of space and food. So a balance isalways maintained. Although the balance may be upset from time to time due to naturaloccurences such as big climate change, the tendency is, after coping up with those changes,the stock will again be able to recover and establish a balance. Of course, some big climaticchanges in the past have caused the extinction of some species.

If you notice, we have not yet included the human activities into the system. We thus call it theunexploited phase. One big influence to balanced state of our stock is the human exploitationitself. Some scientists consider this an outside influence while others believe that this is a

natural part of the entire system. The most evident human activity is fishing, or in our new foundlanguage, the exploitation of the aquatic resources. Russels Axiom can be modified to depictthis exploited phase.

The balance state of our stock is further influenced by another component we call fishing, ordeath due to capture by humans for consumption. This component contributes to furtherreduction of our stock. Initially, we may logically speculate that this component will surely causean imbalance of our system. However, living organisms have their own ways of coping up withpressures exerted on them, in this case, an added pressure due to fishing by humans. In fact,these organisms have not existed this far and survived had they succumbed to pressuresexerted on their being in the different phases of their existence. Fish or invertebrate stockshave their ways of standing up to pressure due to fishing by humans as long as the fishing

intensity is within bounds.

Figure 2. Russels axiom applied to an exploited system.

Fishing will cause the further decrease in the stocks biomass. However, if the intensity of

fishing is low, exploited fishes and other aquatic species have natural ways of coping up withthe situation. They will adapt to the situation and compensate losses by growing faster, matureearly, and reproduce more frequently. In this case, a new and secondary balance is attained.Obviously, this secondary balance can not be attained if the rate of exploitation is very high andthe natural coping up mechanisms of aquatic species can not compensate for the lossesincurred. This means that the sustainable utilization of aquatic stocks is very much dependentupon fishing intensity.

1.3.3 SURPLUS PRODUCTION

Growth

Recruitment

Natural death

Fishing


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The volume or amount of harvest from any living aquatic resource depends on the amount ofeffort put forth to attain the harvest. Therefore, the yield from any given stock will depend onthe fishing effort exerted. Say, a body of water like Manila Bay that is fished only by threefishermen will yield a corresponding volume of fish everyday or every year. Of course, this yieldwill be smaller compared to the same body of water being fished by say 200 fishermen. Try toimagine the scenario when Manila Bay is now being fished by 20,000 fishermen. What comesto your mind is the question: will there be enough fish for all those fishermen? This is where the

idea of maximum sustainable yield came about. Surplus production model was introduced byGraham (1935), but made to practical use and popularized by Schaefer (1954) and Fox (1970)

The yield will continue to increase as the number of fishermen or fishing boats, or the measureof effort, generally called fishing effort, likewise increases. But this is to a certain limit. Therewill come a point when yield will no longer increase even if we continue to increase the fishingeffort. This is the point where we have our maximum sustainable yield(MSY). Beyond this,the yield will even start to decrease even if we continue increasing the fishing effort. At MSY,the balance between the addition to and removal from the stock is still attained. Beyond this,however, the balance is disrupted, which means, there is more removal than addition to thestock.

Figure 3. Yield-effort curve of a surplus production model

By uncontrolled removal from the stock through fishing beyond sustainable yield the stock willbe subjected to extreme pressure to which it can no longer cope up with. At MSY the removal isstill within bounds such that there are enough parent stock left capable of reproducing thedesired number of young individuals and compensate for the losses due to fishing. Withunabated removal, in this case exemplified by overfishing, the stock will continue to decreasesuch that the number of individuals left will not be enough to reproduce the desired number ofyoung and compensate for the losses. And there are other losses to think about. For example,through unabated fishing even young and, therefore, smaller individuals are caught. There is

Yield

Fishing effort

MSY Maximum Sustainable Yield


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biomass loss in this case since the total weight of the same number of individuals caught atmuch larger sizes could have been much bigger. Imagine the loss in revenue by the fishermenthemselves. If you have observed this during marketing, a kilo of smaller fish will cost muchless than a kilo of the same fish at bigger sizes. Actually, the issue boils down to what we havealready known, the problem of overfishing.

1.3.4 TYPES OF OVERFISHING

Fisheries biologists though deeper of the problem of overfishing in the tropics in and realizedthat one way of analyzing the problem is to understand the root of the problem as well as theconsequences. Taken as overfishing all alone, the problem appears enormous. So thebreaking up overfishing into various components was proposed by Pauly (1988). Actually,overfishing was not resolved into its various elements but rather break them up into componentsthat are more or less consequences of each other. But still the understanding of overfishing hasimproved from hereon and the approaches to find solutions have likewise improved.

Accordingly, overfishing may be segregated into growth overfishing, recruitment overfishing,ecosystem overfishing and economic overfishing. Segregating overfishing into thesecomponents may help resolve some of the issues in the use of our aquatic resources especiallythe overexploitation of many resources.

Growth overfishinghappens when fishes are caught before they are given the chance to grow.This is usually the effect of using small meshed nets and inappropriate fishing gears. Throughthe use of small meshed nets young fishes are caught. These fishes could deliver more flesh orbiomass were they given the chance to grow. Our fishing history will reveal that fishermencontinue to design their fishing gears to catch the maximum volume of fish. The thought of if Idon not catch them others will seems to have always prevailed. As the stocks are overfishedand the individual become smaller and smaller the fishermen adopt by using smaller andsmaller meshes. The end effect is that the stock becomes depleted. Again the fishermen willsearch for other stocks and the cycle is repeated until almost all accessible stocks becomedepleted. Then the search for less accessible stocks begins. Because they are lessaccessible, the amount required to extract them sometimes becomes prohibitive that the fishingventures cease.

Another common scenario in the country is the use of fine meshed nets to catch fishes andinvertebrates that do not grow bigger than a few centimeters. These organisms already reachmaturity and adult stage at this size. They are usually present in abundance during a particularperiod of the year. Some common examples are theAcetes sp., or our common alamang, andsome species of gobies or tabios. The problem lies in the fact that some larvae and juvenilesof other species and invertebrates that can grow several inches and more than a foot also mixup with these small organisms. In the process of catching them the larvae and juvenile of theselarger species are also caught. The real problem occurs when the catching of organisms usingfine meshed nets extend beyond the season when these species appear. The end effect is thatmost of the catch will then contain larvae and juvenile of large species.

Recruitment overfishing occurs when so few adults are left that the production of eggs andlarvae is extremely reduced to the extent that addition of new individuals or recruitment to thefishery is impaired. It can also be caused by low survival of eggs and larvae when theirhabitats, especially their nursery grounds, are destroyed. In effect, recruitment overfishing isprimarily caused by extremely high fishing effort that tend to reduce the parent stock and also bygrowth overfishing, when fishes are not given the chance to grow and, therefore, not also giventhe chance to reproduce. The reduction of parent stock can mean the equal reduction of bothmale and female or the reduction of one of the sexes. Try to imagine when there are too few


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males for a stock with plenty of females. The number of females that can be fertilized can notgo beyond the number of males. Therefore, recruitment overfishing is also in effect in this case.

The destruction of natural spawning and nursery grounds such as the lagoons, estuaries,mangrove forests, seagrass beds and coral reefs has extremely contributed to the depletion ofstocks in general and to recruitment overfishing in particular. Even if the fish extraction isregulated or properly managed, there is still no guarantee that the fish resource exploitation canbe sustained if the natural spawning and nursery grounds of the exploitable stocks are

destroyed.

Ecosystem overfishing takes place when the decline in the multispecies stock is not fullycompensated for by the rise in other exploitable animals. A tropical fishing ground in goodshape can offer a variety of species of fishes and invertebrates. The species mix can bemaintained if the stocks are properly exploited. However, depleting one or several stocks mayaffect other stocks because of their interdependence, one as predator or prey of the other. Theend effect is a change in the composition of the species mix. In most instances, the speciescomposition changes from a mix of large species to a mix of relatively smaller species. It is notuncommon to hear old fishermen tell stories of the larger species fishes they used to catch andlament on the size of the current species found in their catch. This problem is compoundedsince the smaller the individuals in the species mix the more individuals have to be caught to

maintain production. In the case of ecosystem overfishing the current species mix composed ofsmaller individuals can not compensate for the loss of larger species.

All of those mentioned above can lead to another form of overfishing called economicoverfishing. This comes about when the economic yield can no longer be realized from thecurrent fishery. It always happens that the change in the species mix is from large to smallerspecies. Also, due to growth and recruitment overfishing the sizes of individuals of the samespecies mix will also reduce. Those doing marketing are aware that a kilo of larger fishes isalways more expensive that a kilo of smaller fishes. This loss in market value is tantamount toeconomic overfishing.

1.4 SUSTAINABLE EXPLOITATION

Let us take this opportunity of putting together what we have learned so far in this module byvisualizing how we can sustain exploitation. Our biggest problem is that we have no choice butto exploit our fishery resources since it is one of the major sources of food especially protein.Our biggest challenge is how to sustain exploitation.

We are aware by now that for a given stock, fishing will decrease in the stocks biomass. Wehave likewise learned that if the intensity of fishing is low, exploited fishes and other aquaticspecies have natural ways of coping up and recover the loss. They will adapt to the situationand compensate losses by growing faster, mature early, and reproduce more frequently.Obviously, this can not be sustained if the rate of exploitation is very high and the natural coping

up mechanisms of aquatic species can no longer compensate for the losses incurred. Whichmeans to say that the sustainable utilization of aquatic stocks is very much dependent uponfishing intensity. Obviously, there is a need to regulate fishing pressure at a certain level tosustain the use of the aquatic resources. Here will come in the maximum sustainable yield orMSY concept also learned before. We all know that at MSY, the balance between the additionto, due to reproduction, and removal from the stock, due to exploitation, is still attained. Beyondthis, however, the system is disrupted, which means, there is more removal than addition to thestock.


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Sustainable exploitation comes in different forms. Regulated fishing pressure is one. Ideally,the number of fishermen and number of fishing boats deployed in a fishing ground should not gobeyond the fishing effort that delivers the maximum yield. This is usually done throughlicensing, wherein the number of boats allowed to operate are given permits for a specificperiod. Another is through catch quota. Together with the issuance of permit to fish, a specifiedvolume of fish is likewise allowed a certain fishing outfit for a specified period of time, say oneyear. The allowable catch is based on estimates of surplus production. This is usually divided

equally or proportionately among the fishing outfits allowed to catch fish.

Regulating the size of fish that can be caught is another. This is usually put into operation byregulating the mesh size being used. Mesh size regulations are usually incorporated in fisherylaws and regulations. To ensure compliance, penalties to violators are likewise specified.

We have also learned earlier that even if the fish extraction is regulated or properly managed,there is still no guarantee that the fish resource exploitation can be sustained if the naturalspawning and nursery grounds of the exploitable stocks are destroyed. Current initiatives in thisregard include declaration of protected areas for aquatic organisms. The protected areas areusually categorized into no take zones and limited access zones. In the no take zone thehabitat is totally protected, meaning, no human activity is allowed in the protected zone. This

total protection will enable the nursery or spawning grounds achieve its purpose. However,fishermen operating in the area will likewise need to perform their livelihood. For this purpose, alimited access zone is provided for allowing specific fishing activities. Normally these fishingactivities were previously identified and presumed to be sustainable.

1.5 CONTROL MECHANISMS

Worldwide trends in capture fisheries decline are an indication that fishery resources are limited.The previous section on overfishing has shown us that uncontrolled exploitation patterns willlikely bring about potentially irreversible undesirable outcomes in our fisheries resources, suchas stock collapse, species shifts and loss in biodiversity, and disrupted marine ecosystem

functions, eventually making the fishery economically non-viable. Fisheries resourcemanagement aims to reverse this trend through measures that will conserve fish stocks andpromote sustainable means of harvesting fishery resources. However, responsible andeffective fisheries resource management requires information regarding the resource or stock tobe managed. This includes, among others, information on aspects of its biology, its behavior,its interactions with other species or groups, and its role in the ecosystem. In addition,information on the rates and patterns of exploitation of the particular resource and the social andeconomic characteristics of the resource users are equally critical. Unfortunately, theseinformation are not always available. In cases where information on fisheries resources isavailable, this may be incomplete and/or distorted owing to the complexity and unpredictabilityof aquatic ecosystems. Technological constraints, errors, and potential biases in data collectionfurther compromise the accuracy and reliability of information generated. Does the lack of

accurate and reliable information suggest fisheries resource management to be unfeasible?

Principle 15 of the Rio Declaration of the UN Conference on Environment and Developmentstates,

"In order to protect the environment, the precautionary approach shall be widelyappliedWhere there are threats of serious or irreversible damage, lack of fu ll


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scientific certainty shall not be used as a reason for postponing cost-effectivemeasures to prevent environmental degradation."

The Code of Conduct for Responsible Fisheries embraces the precautionary approach andprescribes it in fisheries management (FAO Fish.Tech.Pap., 350/1, reissued as FAO TechnicalGuidelines for Responsible Fisheries. No.2. Rome, FAO. 1996. 54p.). Likewise, Section 3.1 ofFAO Precautionary Approach to Fisheries Part 1 also reiterates that fisheries management(according to the precautionary approach) should exercise prudent foresight to avoid

unacceptable or undesirable situations, taking into account that changes in fisheries systemsare only slowly reversible, difficult to control, not well understood, and subject to change in theenvironment and human values. In other words, the precautionary approach to fisheriesresource management assumes that all fisheries activities have impacts on the resource (eitherdirect or indirect, wheteher obvious or not), and some of these outcomes can be potentiallydangerous in the long run that there is a need to take action despite the lack of information orwith minimal information available.

Control mechanisms are applications of the precautionary approach in fisheries resourcemanagement. These include all management tools that aim to limit the proportion of fisheryresources harvested in order to protect fishery stocks from overexploitation and to encouragethe recovery of already heavily-exploited stocks. In most cases, however, these mechanisms

are established to pursue the latter aim, that is, they are seen more as curative measures ratherthan instruments to promote sustainable exploitation. Control mechanisms can be either INPUTor OUTPUT controls depending on the aspect/s of the fishery that they endeavor to constrain.Furthermore, they can be classified as either quantitative or qualitative. Descriptions on thetypes of control mechanisms will be discussed in the following sections. Some examples willalso be provided.

1.5.1 INPUT CONTROLS

Input controls are measures in fisheries resource management that constrain directly anyaspect of the fishing effort. Following Morison (2004), they prescribe WHO does the fishing,WHEN they can fish, WHERE they can fish, and HOW they can fish. For example, control of

access to the fishery through issuance of fishing licenses regulates the number of participants inthe fishery. Establishment of temporal and spatial controls through closed seasons andprotected areas limit the duration and extent of fishing activities, thus regulating fishing effort.Similarly, enforcing technological controls on the fishing vessel through tonnage limits, forexample, and on the gear through specific requirements in gear specifications andcharacteristics also control the fishing effort.

Quantitative input controls limit fishing effort in terms of number or quantity of effort. Issuance ofa specific number of fishing licenses or permits, regulating the total number of gillnet panels perunit, and allowing only a fixed number of fish corrals to be operated in an area are just a fewexamples. A temporal closure can be classified as a quantitative control when it prescribes aspecific number of days when fishing is not allowed. When the closure is prescribed for a type

of day or season, such as during the week of the new moon, it then becomes qualitative.Qualitative input controls, therefore, put limits on the characteristics of the fishing effort. Otherexamples include mesh size regulations, limits on vessel tonnage, and prohibiting the use ofactive gear types in municipal waters.

1.5.2 OUTPUT CONTROLS


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Output controls are measures in fisheries resource management that constrain directly anyaspect of the catch or that which is to be harvested. These controls prescribe WHAT is allowedto be fished (Morison 2004). When an output control is designed to limit the amount of fish tobe harvested through catch quotas and total allowable catches (TACs), it is classified as aquantitative output control. On the other hand, when the restriction is imposed on the variouscharacteristics of the catch other than the amount, then it becomes a qualitative output control.

An example is prohibiting the harvest of individuals in specific critical life or maturity stages,such as the juveniles and spawners. In relation, enforcing minimum and maximum size limits

on individual fish caught is a qualitative control that aims to allow smaller individuals to grow andto protect the mega-spawners. Prohibitions on the harvest of endangered and rare species arealso forms of qualitative output controls.


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1.6 ASSESSMENT AND MANAGEMENT APPROACHES

The approach in the assessment of the fishery resources is also reflective of the managementapproach to be instituted. The management of fish stocks has gained momentum during thesepast five decades. It started with the need to manage large marine fish stocks exploited by bigfishing fleets. The focus is on specific fish groups and follows a single-species approach.Management interventions were based on information about the dynamics of the population of aspecies of fish. Other information and parameters, including its interactions with other speciesas well as with the ecosystem are just peripheral. This interaction, however, proved to becrucial for many fish stocks. This prompted fishery biologists and scientists to look into themulti-species approach. It was realized that exploiting a particular species will have directconsequences on its predator or prey species. The more knowledge gained about theinteraction the more new questions arise. From these gained knowledge, it was also realizedthat an ecosystems approach to the management of fish stocks and other aquatic resourcesprovides more comprehensive array of management options than the single species or even theintegrated species approach. Overexploiting a species or a group of species changes thepopulation structure and not just of the target species themselves. This is recognized byresource managers as very important inputs to formulation of fishery resources managementmeasures and, in many cases, is deemed the key to success of management initiatives

Management of stocks from the single-species and multi-species level was likewise tried usingan integrated approach. Production models were used to determine the limit to fishing effort toachieved maximum yield from a single species stock or stocks of multi-species mix. Theapproach does not require information about the age and size structures as well as composition.However, a time series of catch and effort data is needed and since fishing effort are lumpedtogether, an elaborate standardization procedure is required. This proved, however, not easilyapplicable to multi-gear and multi-species fisheries in the tropics.


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REFERENCES

Cochrane K.L. 2002. Chapter 1: Fisheries Management, pp.1-20. In: Cochrane, K.L. (ed.) Afishery manager.s guidebook. Management measures and their application. FAO FisheriesTechnical Paper. No. 424. Rome, FAO. 231p.

FAO Fishery Resources Division and Fishery Policy and Planning Division. 1996. Fisheries

management. FAO Technical Guidelines for Responsible Fisheries. No. 2. Rome, FAO. 54 p.

FAO. 1995. Precautionary approach to fisheries. Part 1: Guidelines on the precautionaryapproach to capture fisheries and species introductions. Elaborated by the TechnicalConsultation on the Precautionary Approach to Capture Fisheries (Including SpeciesIntroductions). Lysekil, Sweden, 613 June 1995 (A scientific meeting organized by theGovernment of Sweden in cooperation with FAO). FAO Fisheries Technical Paper. No. 350,Part 1. Rome, FAO. 52 p.

Fox, W.W. Jr., 1970. An exponential surplus-yield model for optimizing exploited fishpopulations. Trans.Am.Fish.Soc., 99:80-88

Morison, A.K. 2004. Input and output controls in fisheries management: a plea for moreconsistency in terminology. Fisheries Management and Ecology11: 411-413.

Pauly, D. 1988. Some definition of overfishing relevant to coastal zone management inSoutheast Asia. Trop. Coast. Area Management. Vol. 3, No. 1, 14-15.

Pope, J. 2002. Chapter 4: Input and output controls: the practice of fishing effort and catchmanagement in responsible fisheries, pp.77-93. In: Cochrane, K.L. (ed.) A fishery manager.sguidebook. Management measures and their application. FAO Fisheries Technical Paper.No.424. Rome, FAO. 231p.

Russell, E.S., 1931. Some theoretical considerations on the "overfishing" problem.J.Cons.CIEM,6:1-20

Schaefer, M., 1954. Some aspects of the dynamics of populations important to the managementof the commercial marine fisheries. Bull.I-ATTC/Bol. CIAT,1(2):27-56

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Fisheries Resource Management Principles_rev