Some Definitions of Overfishing Relevantto Coastal Zone Management in Southeast Asia

~ oastal zone management (CZM),~ a multidisciplinary activity parexcellence. involves branches of thenatural and social sciences in which theconcept of overfishing has no operationalmeaning. Thus, fishery biologistsworking alongside representatives ofother disciplines are often hard-pressed todefine this concept, which is of crucialimportance to fishery management.

This essay is an attempt to defineoverfishing in terms less technical thanthose generally used by fishery biologists.I staned from the classical definition,then quickly moved on to what I hope areconcepts that may be more relevant toCZM.

Overfishing is a single process, butmay be viewed as having five facets, ofwhich three are recognized forms ofoverfishing. The first well-known form isgrowth overfishing, which what happenswhen fish are caught before they havetime to grow. This form, which began tooccur in some Nonhero European fishinggrounds as early as the end of the lastcentury has been solved in theory by theRussian scientist F.I. Baranov just afterWorld War I. However, it is the work ofRJ.H. Beverton and SJ. Holt (of theLowestoft Laboratory, Britain) whichafter World War II presented methods bywhich growth overfishing could bediagnosed in practice and remedied byfishery management (for example,through the imposition of appropriatemesh sizes for fishing gears).

Research work related to overfishingnowadays conducted in various researchinstitutions throughout the world(including ICLARM) consists of esti-mating the ages, and the growth andmortality rates of fish and assessing the(mesh) selection characteristics of fishinggears, as well as adapting Beverton andHolt's and related models to the multi-species situation typical, e.g., SoutheastAsian coastal trawl fisheries.

The second recognized form of over-fishing is recruitment overjishing which

14

DANIEL PAULYICLARM

refers to fishery-induced reductions of thenumber of young fish entering the fishinggrounds. Recruitment overfishing can bebrought about by: (1) reduction of thespawning stock (which may become sosmall such as to produce a limitednumber of eggs and hence of recruits) and(2) coastal environmental degradation,which usually affects the size or suit-ability of nursery areas:

Note that preventing recruitment over-fishing is not, as lay persons often think, amatter of letting each female spawn atleast once (since less than one in athousand anchovy or shrimp larva reach amature age, even in the absence of afishery) but rather a question of notfishing too much. Models to express whattoo much is were first developed by theCanadian scientist W.E. Ricker. Thesemodels found little application in thetropics, however. Rather, it is surplus-production ("Schaefer" or "Fox") modelsthat are used to manage tropical fisheries.These models do not distinguish betweengrowth and recruitment overfishing butrather lump the two processes into asingle category of general biologicaloverfishing (Fig. 1).

__ Maximum SustainableY~~ IMSY) ~

Fig. 1 also defines economic over.fishing as a fishery at a level of effonhigher. than that which maximizes theeconomic rent, i.e., the differencesbetween gross returns and fishing costs.Note that this optimum level is less thanmaximum sustainable yield (MSY) andthat, therefore, maximum economic yield(MEY) is less than MSY (Fig. 1).

I have introduced in 1979 (ICLARMNewsl. 2(3): 3-4) the concept of eco-system overfishing to characterize theprocess which took place in the 1960s inthe Gulf of Thailand (and, at differenttimes, in other areas of Southeast Asia)where demersal trawling was so intensethat it altered the balance of species onthe fishing grounds, with some speciesincreasing, but failing to replace thedepleted ones.

This process implies that a part of thesystem's ecological production now goesinto side branches of the food webs, e.g.,into benthic invertebrates or largezooplankton, i.e., into nonresourcespecies. Examples of ecological over-fishing abound throughout the world, andresearch has been initiated at ICLARMon the dynamics of food webs in relationto ecosystem overfishing.

With this, . the three aspects ofoverfishing that are focused on what

Total fl.hlngcost. (In unit.of catch)

Fishing effort (f)

Fig. I. Schematic representation of a surplus-production model defining biological overfishing (due

to growth and recruitment overfishing) as any fish!n~ at a level of f beyond fMSY' (Schaefer and foxtype model differ only in shape of rightmost area.)

Tropical Coastal Area Management

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happens to tfie resource species are Area Management 2(3): 1-4).covered. I may now turn to Homo By all scientific standards, there aresapiens. too many small-scale fishermen in South-

Overfishing, at least as far as its first east Asia. Moreover, their numbers aretwo forms are considered, is well- rapidly growing (with a doubling time ofdescribed in textbooks, and the suggested less than 20 years), both because of theirremedies usually involve a mix of own children and because of increasingmanagement measures (e.g., mesh size landlessness among farmers, to whomregulations, closed areas or seasons, fishing becomes the occupation of lastlimits on gear sizes or on craft designs, resort.etc.). All of these measures imply that the I shall call the form of overfishingfishermen concerned are actually in a these fishermen produce "Malthusiansocial and financial position to either overfishing," after the Reverend I.R.implement or comply with those Malthus (1766-1834), the prophet ofmeasures. Usually they can, because the doom that would be so easy to refute iftextbooks are written in and for the real problems of humanity weredeveloped countries in which most tackled, rather than their ideologicalfishermen are the employees of well- shadows.financed corporations, or independent (if M lth

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Lingayen Gulf Profile, Tropical coastal) ness and generally in temporal sequence:April 1988

--

(1) use of gears and of mesh sizes notsanctioned by government; (2) use ofgears not sanctioned within the fisherfolkcommunities- and/or catching of fish"reserved" for a certain segment of thecommunity; (3) use of gears that destroythe resource base; and (4) use of "gears"such as dynamite or sodium cyanide thatendanger the fisherfolks themselves.

This sequence, generally misunder-stood by administrators and fisheryscientists alike as reflective of ignorance,or of putting the short-term gain ahead offuture benefit (or even as evidence of amoral decline) is in fact reflective ofnothing but the logical result of decliningcatch per effort (and hence incomes),

To put things bluntly: if I were afisherman, with no alternative employ-ment opportunities, and I had to feed mytwo children by blowing up a fishingground, I certainly would do so.

Thus, what I'm saying here is that"Malthusian overfishing" being quitesimply due to too many fishermenchasing too few fish can only be tackledby altering the fishermen/fish ratio. Noclever mesh size regulations or motoriza-tion scheme, no strict enforcement orlaments about dynamite fishing canreplace such change.

On the short run, some palliatives maybe found for this problem, however,Trawl bans, such as the one imposed in1980 in Indonesia, illustrate one of thesepalliatives, i.e., increasing the number offish available to small fishermen byeliminating their competitors.

This is not a long-term solution, how-ever, because, as mentioned above,fisherfolk populations in Southeast Asiaare likely to double in less than 20 years--especially in countries such as thePhilippines and Indonesianand theproblem of declining income to reappearwithin far fewer years than this.

The solution is clearly alternativeemployment opportunities, in villages andtowns and cities, for young and not soyoung, for literates and illiterates, andstabilization of populations. Withoutthese? Forget about coral reefs andmangroves, and forget about havingoptions for coastal resourcesmanagement. 0

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