Global landings from marine capture fisheries in 2002 were 84.5 million tons (Figure 23) and remained relatively stable between the years 1999 until 2002

The discussion led by Watson and Pauly (2001,534) about overestimates of China’s marine capture fishery production between 1995-1999 and the resulting understating of the degradation of world fisheries and its consequences has been refuted by the FAO, which draws upon an analysis by Grainger and Garcia from 1996. This analysis pictures a dramatic progression of overfishing since 1950 and thus confirms, “ (…) despite likely errors in the data sets, the main global trends have not been masked (…)” (FAO 2002,3-4).

Figure 23. World capture fisheries production.

Source: FAO 2004,5

The rise of world marine fish catches coincided with the rapid growth of the commercial fishing fleets (Figure 24). The vast majority of the world fishing fleet is concentrated in Asia with about 85 percent of total decked vessels, 50 percent of powered undecked vessels and 83 percent of unmotorized boats (FAO 2004,6). The aggregate gross tonnage (GT)

The gross tonnage for ships of 24 meters in length and over refers to the volume of all ship’s enclosed space (from keel to funnel) measured to the outside of the hull framing (FAO 1998a).

Figure 24. Global fleet above 100 gross tonnage

It should be noted that only a small proportion of the Chinese fleet vessels are included in the Lloyd’s Maritime Information Services. Furthermore, changes in the measurement of tonnage, gross registered tonnage (GRT) to gross tonnage (GT), require caution in the interpretation of trends. (FAO 2004,24)

Between 1970 and 1995 the size of the world fishing fleet expanded by more than 400 percent, while fish catches increased by only 30 percent (Green et al. 2003,5). The overinvestment in the world’s capture fisheries has led to more harvesting effort than is appropriate (WTO 2002,3). Arnason (1998) compared several studies on the overcapitalization of world capture fisheries and its consequences. While the total value of world capture fishery harvests is fluctuating around 80 billion USD (Grainger 1999,21; FAO 2004,7; WTO 2002,3), an FAO study from 1993 estimated that global fisheries costs exceed revenues by 54.4 billion USD or 78 percent (FAO 1993, cited in Arnason 1998,1). Direct or indirect subsidies that Milazzo (1998, cited in Arnason 1998,1) estimated at between 14 and 20 billion USD annually or 17 to 25 percent of industry’s revenues has met the shortfall (cf. WTO 2002,3). Given the high level of subsidies in global capture fisheries it is not surprising that the fisheries are heavily overcapitalized (Arnason 1998,2). As a result this excess capacity is exported to previously undesirable fishing grounds of many developing countries consequently causing overfishing and preventing a successful development of these countries’ own fisheries (WTO 2002,3; FAO 1998b). However, my incentive is not to engage in the ongoing debate about global marine capture fisheries subsidies but to draw attention to the resulting overfishing of fishery resources (cf. FAO 2004,128; Grainger 1999,23; Froese and Pauly 2003,250).

A study undertaken by the FAO in 1996 based the world’s 200 most important fishery resources in terms of landings and grouped them into a few families to identify the stages of fishery development (Grainger and Garcia 1996). The results shown for 1994 indicated that about 35 percent of the 200 major fishery resources were senescent, about 25 percent mature, 40 percent were still developing, and zero percent remained at low exploitation level (Figure 25). In other words 60 percent of the major world fish resources were categorized as either mature or senescent and the authors proposed that urgent need of management action was required to halt the increase in fishing effort or rehabilitate overexploited resources (Grainger and Garcia 1996; Grainger 1999,23).

Figure 25. Major marine fish stocks in various phases of fishery development.

Source: Grainger 1999,23

A more recent study from the FAO (2004,32) estimated that in 2003 three percent of the stocks monitored were underexploited and 21 percent moderately exploited (Figure 26). About half of the stocks, namely 52 percent, were fully exploited i.e. producing catches close to their maximum sustainable limits (Figure 26). Further, 10 percent of stocks were overexploited, seven percent depleted, and one percent of stocks were recovering from depletion and needed rebuilding (Figure 26).

Figure 26. Level of exploitation of world’s main fish stocks.

Source: FAO 2004,32

Several forms of overfishing exist and have been described in the literature (Pauly, Saeger and Prein 1998; Pauly, Silvestre and Smith 1989; Green et al. 2003). The authors commonly use the Philippines to exemplify the nature of overfishing and its causes, since the once outstanding and productive marine ecosystem of the Philippines shows severe signs of overfishing nowadays (Green et al. 2003,6).

• Growth overfishing is the case, if the fish caught in fisheries simply did not have the time to grow to bigger size (Pauly, Saeger and Prein 1998,17). This somewhat mildest form of overfishing began to occur in some northern European fishing grounds and today is common in most fisheries worldwide yet is of particular importance in the marine capture fisheries of the Southeast Asian region (Pauly, Saeger and Prein 1998,17; Pauly, Silvestre and Smith 1989,310). Although growth overfishing can be remedied by fishery management, e.g. through the introduction of minimum mesh sizes for fishing gears, it is difficult to appoint an appropriate mesh size in multispecies fisheries that utilizes all species at their biologically optimum range (Pauly, Saeger and Prein 1998,17; Pauly, Silvestre and Smith 1989,310). The Southeast Asian coastal trawl fishery is a typical example for a multispecies situation, whereby 30 to 50 species usually dominate the landings (Pauly, Silvestre and Smith 1989,310). These species vary in size from very small (shrimp) to very big (sharks, rays). The common use of mesh sizes of 2.0 centimeters and less in these regions just as in Nha Phu Lagoon thus leads to considerable growth overfishing (Pauly, Silvestre and Smith 1989,310). Pauly, Saeger and Prein (1998,18) point out that the current statutory mesh size of 3.0 centimeters in the Philippines needs to be raised to at least 4.0 to 5.0 centimeters to maximize yields.

• Recruitment overfishing is the next step in overfishing and describes the phenomenon when the spawning stock is reduced to a point that it only produces limited numbers of eggs and thus recruits (Pauly, Silvestre and Smith 1989,315). Since a majority of the fish caught in a fishery showing recruitment overfishing are juvenile, as most of the adult fish have already been caught, the remaining fish are smaller, earlier maturing and less productive leading to the eventual depletion of the stock (Green et al. 2003,22).

• Ecosystem overfishing characterizes a situation where intensive fishing leads to an ecological imbalance, so that some species increase but fail to replace the depleted ones (Pauly, Saeger and Prein 1998,18). Basically, an increased part of the ecological production goes into side branches of the marine food web, e.g. into benthic invertebrates (squid, shrimp) or into large, inedible zooplankton such as jellyfish (Pauly, Saeger and Prein 1998,18). General indices of ecosystem overfishing in tropical regions are:
  - Increased abundance of squid, shrimp and triggerfish
  - Above-average decline of grouper and related species
  - Disappearance of sharks and rays (Pauly, Saeger and Prein 1998,18)
  This process of changes in the faunal composition associated with increased fishing pressure has also been described in Pauly et al.’s (1998) “Fishing Down Marine Food Webs” (Figure 27).

• Malthusian overfishing occurs when poor fishermen facing declining catches and lacking alternative livelihood strategies use illegal and destructive fishing gear (small mesh size, dynamite, cyanide) to improve their catch (Pauly, Silvestre and Smith 1989,315). This form of overfishing is often misunderstood by administrators and fishery scientists, since it only produces short term benefits, yet critics overlook that it is the logical result of declining catches and that it can only be tackled by providing alternative income strategies in the non-fishery sector (Pauly, Silvestre and Smith 1989,323; Pauly, Saeger and Prein 1998,18).

• Economic overfishing is referred to when fishery expenses are higher than the anticipated maximum economic yield (Pauly, Saeger and Prein 1998,18). Note that this optimum level of effort is lower than that which produces maximum sustainable yield (Pauly, Silvestre and Smith 1989,320). Based on the Philippine studies Pauly, Saeger and Prein (1998,18) estimate that effort levels in demersal and small pelagic fisheries are three times that, which would generate maximum sustainable yield. The implied dissipation in the form of excessive operating costs is estimated to be about 100 to 160 million USD annually for demersal fish and about 300 million USD per annum for small pelagic fish (Pauly, Saeger and Prein 1998,18).

Figure 27. Fishing down marine food webs.

“Wherein a fishery starts by catching abundant large fish high in the food web (upper left corner), then gradually shifts to smaller fish, lower in the food web, as the former resource becomes less abundant. This process, which occurs in virtually all fisheries of the world, usually goes along with habitat destruction, as illustrated here by the gradual disappearance of the bottom structure created by bottom organisms.” (Pauly and Chuenpagdee 2002,210)

In order to meet overfishing fishery management offers several approaches. The most common terms and concepts used in fishery management are:

Maximum sustainable yield, MSY is the largest long-term average catch (yield) that can be continuously taken from a stock without affecting significantly the reproduction process, i.e. threatening the existence of the population (FAO 2006). Maximum sustainable yield is the classical sustainability indicator in fisheries management with the longest history (Degnbol 2001,10). Maximum sustainable yield itself is no indicator of the state of the stocks or the sustainability of the fisheries and must be used in combination with a fishing effort indicator or fishing mortality to make sense (Degnbol 2001,10). The concept of maximum sustainable yield is subject to broad discussion and critique in fisheries biology partly because of the following shortcomings:

• In practice no data exist that estimate the maximum of the yield curve especially beyond maximum sustainable yield and with standardized effort measure (Degnbol 2001,11).

• Another problem of the concept, if used as a single indicator, is that exploitation and recruitment are decoupled and the term ‘sustainability’ implies that the stock remains at maximum sustainable yield and exploitation is sufficient to maintain reproduction, although the model does not acquire knowledge concerning the spawning stock (Degnbol 2001,11).

To a certain extent the shortcomings have been met by replacing the former surplus production model from Schaefer (1954) a logistic growth curve underlying the dynamics of the yield curve with an age structured population model following Beverton and Holt (1957) fisheries biology (Degnbol 2001,10). However, data requirements for the latter are much higher, which is why this model found little application in tropical fisheries (Pauly, Silvestre and Smith 1989,315). For better understanding I draw on the model of Schaefer (1954) as described by Pauly, Saeger and Prein (1998,17) that depicts in the form of a parable the effort and catch of a fishery (Figure 28). From the starting point of the coordinates (no effort = no catch) the curve rises rapidly and reaches a maximum that describes the maximum sustainable yield (Figure 28). Any further increases in effort decreases the catch, until the stock of fish eventually becomes extinct. From an economic point of view it would be best to maximize the resource rent, i.e. to approach the maximum sustainable yield until there is no increment in catch associated with an increment in effort. This point is called maximum economic yield (MEY) see Figure 28. For fishermen these concepts are of little relevance, since their incentive is their own catch which is supposed to be of more value than the associated fishing costs. To understand the behavior of fishermen it is necessary to look at total catches and total costs of effort. This factor can be depicted in a simple line (fishing effort = costs in monetary units) that crosses the yield curve in the point T_C (Figure 28).

Figure 28. The Schaefer model of the Philippine demersal fisheries.

Source: modified and adopted from Pauly, Saeger and Prein (1998,18)

It should be noted that yield levels around the point T_C also occur to the left of the yield curve, i.e. the quantity of fish caught in a situation involving overfishing can also be caught with considerably less fishing effort, less fishermen or boats, and at less expense (Konstapel and Noort 1995,16).

Catch per unit of effort, CPUE is the amount of catch that is taken per unit of fishing effort, e.g. weight of fish in tons taken per hour of trawling (FAO 2006). Catch per unit of effort is often used as a measure of the economic efficiency of fishing gear as well as an index of fish abundance (FAO 2006). Generally, a decline in catch per unit of effort against a background of stagnating catches implies overfishing and most likely overcapacity (FAO 2004,121). However, one needs to be careful using decline of catch rates as a direct indication of overfishing, since this would assume that fish stock and fishery are randomly and spatial distributed which is the exception rather than the rule (Degnbol 2001,12). In addition constant catchability of the fishery is also the exception due to the development in fishery technology (Degnbol 2001,12). Hence, this indicator of abundance itself is not sufficient to identify the reference points of fishery management (Degnbol 2001,12; FAO 2004,121).

Total allowable catch, TAC is the quantity of fish that can be taken from each stock annually (FAO 2006). The total allowable catch is usually allocated among resource users in the form of quotas. The management of fisheries resources by limiting catches through the imposition of catch quotas (TACs) has a long history (Morgan 1997). Nevertheless, several of the fisheries managed by catch quotas experienced declines or collapses at some point (Morgan 1997). One of the reasons is that discards - the unintended catch of non-target species which are returned to the sea - are not included in the total allowable catch, even though, depending on the type of fishery, discard rates can reach over 80 percent of the total landings (FAO 2004,34;121;123;127). In the North Atlantic the International Council for the Exploration of the Sea (ICES) advises the 19 member countries to set the total allowable catch of fish stocks. Despite the proposals from the International Council for the Exploration of the Sea fishing quotas are decided on the basis of political considerations and largely ignore scientific advice typically legalizing catches beyond sustainable levels (Froese 2004,87).