5. COASTAL PELAGIC FISH FISHERIES AROUND JAPAN

The majority of coastal pelagic fish resources distributed in the waters around Japan are composed of nine major species. They include Japanese sardine, Japanese anchovy, Japanese chub mackerel,¹ Japanese Jack mackerel, Pacific saury, Japanese amberjack (yellowtail), Japanese Spanish mackerel, Japanese flying squid and Japanese round herring.² An overall review of the biological features of these species and their fisheries have already been well documented in other papers (Nagasaki, 1973, Chikuni, 1985, Yamanaka et al., 1988). The authors therefore discuss here a few important features closely related to the management of multispecies pelagic fish resources in the region.

The above-mentioned nine species can be divided into two groups: (1) the species of small size with a short lifespan and planktivorous to omnivorous food habits and (2) the species of larger size with a comparatively long lifespan and omnivorous to piscivorous food habits. Sardine, anchovy, chub mackerel, Jack mackerel, saury, flying squid and round herring make up the first group, and amberjack and Spanish mackerel in the second.¹

¹Strictly speaking, nominal catch statistics include the catch of a small amount of spotted chub mackerel, Scomber australasicus Cuvier, due to the difficulty in separating the species on board. They account for about 5 percent of the chub mackerel catch in the northern waters and about 15–25 percent in the southern waters.

²From the long-term point of view, Pacific herring is also one of the major coastal pelagic fish species of the region. From about 1910 to the early 1930's, herring predominated in northern waters of the region with annual catch of 500 to 700 000 tons, but these declined drastically during the 1940's and 50's. Recent annual catches remain low at several thousands tons only, this phenomenon being the complete reverse of what happened to Japanese sardine. It is possible that herring stocks will make a remarkable recovery in the future to become a part of major coastal pelagic fish resources in the region, as was the case with sardine. However, the authors exclude Pacific herring from discussion in this paper to focus on topics of current concern.

5.1 Small Pelagic Fish

5.1.1 Biological features

The distribution ranges and major habitats of the fish in the first group generally overlap, as do some of their spawning grounds and seasons. There is undoubtedly, therefore, severe competition among these species for common requisition. For instance, competition for food during both larval and adult stages and for space among adults must be common. Even predacity among them by omnivorous species has been frequently reported, e.g. (i) flying squid feeding on sardine, anchovy, Jack mackerel and saury, (ii) adult chub mackerel on juvenile sardine and anchovy, (iii) adult Jack mackerel on juvenile sardine and anchovy, etc. In addition, all the species in this group are important food items for the larger omnivorous and piscivorous pelagic species, i.e. amberjack and Spanish mackerel. They therefore form a highly complicated multispecies fish community in the upper layer of the sea in the region.²

Another distinguishable feature of the fish of this group is large fluctuations in stock abundance. The exact causes of this fluctuation are not yet known. However, scientists specializing in the subject recently agreed that the causes are mostly natural rather than to do with fishing (Csirke et al., 1984, Chikuni, 1985), and fluctuation in the survival rate for natural reasons during the early life stage of the fish is assumed to be one of the critical factors.

¹ (i) Skipjack tuna migrating annually into the coastal waters along the Pacific coast of Japan from early summer to autumn can also be placed in the latter group. Skipjack tuna are distributed widely in the Pacific Ocean beyond the region and are highly migratory fish. However, a large number of schools that migrate to the region to feed play a highly significant role in the predatory loss of coastal pelagic fish in the area, especially from the first group mentioned above. It is, therefore, an important element in the multi-species pelagic fish community in the region from a biological point of view. However, the authors exclude skipjack tuna from discussion here, as the management of skipjack tuna stocks raises issues that are beyond the framework of this paper.

(ii) Japanese sea bass has also acquired a pelagic nature, being caught by various kinds of surface gear including gillnets, setnets, purse seines, boat seines, hook-and-lines, etc. The fish can not, however, really be dealt with as a pelagic fish since it has a eurybath nature, while the trawl catch usually accounts for only 10–15 percent of the total. Sea bass is a highly neritic and sedentary fish inhabiting southern waters but a few biological features resemble those of Spanish mackerel or skipjack tuna, e.g. long lifespan and high trophic level. Stocks in the Seto Inland Sea will be discussed separately in a later section of this paper (see Subsection 6.3.3).

²Anchovy has a eurybath nature, inhabiting the sea from the surface to the bottom layer. Plenty of anchovy are found in the stomach contents of piscivorous and omnivorous demersal fish. The predatory loss of anchovy must therefore be quite large, since it is eaten by both pelagic and benthic predators. In fact, it has been estimated that the predatory loss of anchovy off the southern Pacific coast of Honshu far exceeds the catch taken by anchovy fisheries (Chikuni, 1985). Anchovy has acquired, therefore, a highly complicated multispecies nature not comparable with most other pelagic fish communities.

The natural mortality of these species during the early life stage is extremely high. For example, in sardine stock about 70 percent of eggs spawned are estimated to die during two- to three-day period before hatching, and about 96.5 percent of larvae hatched are lost during the 2 weeks before they reach the early post-larval stage at 17 mm body length. The total loss by the end of the post-larval stage (35 mm), 58 days after hatching, reaches about 99.93 percent. These figures are typical for pelagic fish, losses at the end of the post-larval stage being 99.9958 percent for chub mackerel, 99.9 percent for anchovy and 99.95 percent for amberjack. A change, even if a slight, in the natural mortality rate of these fish during their early life stages would therefore greatly affect first the magnitude of recruitment of the year-class born, and ultimately the total biomass of the entire stock in question.

The highly complicated oceanographic features of the region, which is prominent among the world's oceans, generally provides extremely favourable conditions for living resources, resulting in the formation of one of the most productive fishing grounds in the world (Nasu, 1975, Chikuni, 1985, Yamanaka, et al., 1988). On the other hand, changes in environmental conditions sometimes greatly affect the abundance of stock in both positive and negative ways. For instance, (i) the success or failure in spawning, embryonic development and/or hatching, (ii) magnitude of dispersion or concentration of eggs and larvae, (iii) the likelihood of finding enough suitable food at the critical stage (beginning of post-larval stage), and (iv) the likelihood of becoming the prey of other animals, including carnivorous zooplanktons are determined chiefly by environmental conditions. A change in one or a combination of these factors could result in a substantial change in the early survival (or mortality) rate (Chikuni, 1985).

Changes in stock abundance have led to large fluctuation in the catch of each species, except those of anchovy and round herring. Figure 4 shows the fluctuations observed for each from 1957 to 1981.

Japanese anchovy is the only species in this group which had not shown a drastic increase or decrease in its biomass over the years. It is assumed that the tolerant/resistant nature of the fish to (i) changes in the environment and (ii) large mortality (by predacity and heavy fishing) prevent large and rapid changes in its stock abundance (Chikuni, 1985). In the case of round herring too, species-specific biological features must have played an important role in keeping stock levels fairly stable (e.g. many small and separated local stocks confined to the southern region), although the details are not yet understood.

Pacific saury shows frequent short-term fluctuations with a one- to three-year interval, which may be more a result of annual changes in the catchability of fish schools than the changes in stock abundance (Chikuni, 1985).¹ However, a long-term change in stock abundance has been observed separately, which may have been caused by natural factors similar to those affecting other coastal pelagic fish.

¹Similar fluctuations can be observed in the annual catch of skipjack tuna in coastal waters along northeast Honshu. Again, the explanation may have more to do with the catchability of the fish schools (pole-and-line fishing is used) rather than with annual changes in exploitable stock biomass.

Figure 4. Annual change in the catch of major coastal small pelagic fish taken from the waters around Japan from 1957 to 1981 (Nagasaki, 1983).

Large changes in the catches of sardine, chub mackerel, Jack mackerel and flying squid are undoubtedly caused by fluctuations in stock abundance. Japanese sardine is the most extreme example. However, it is interesting to see that the total catch of this group (seven species combined) has shown a fairly stable trend over the years under review (see Figure 4). It can be seen that (i) a substantial increase in the catch of Jack mackerel from the mid-1950's to the mid-60's accompanied a large decline in that of sardine, (ii) a large increase in chub mackerel during the mid-1960's accompanied a sharp decline in Jack mackerel and a gradual decline in saury, and (iii) the recent rapid increase in the sardine catch since 1973 accompanied the further decline in Jack mackerel, and a gradual decline in catches of anchovy and flying squid.

The processes responsible for these changes are not yet understood. However, it is clear that the species composition of the pelagic fish community in the region is always changing dynamically, with dominance switching from one species to another (possibly through both the density-dependent and independent natural factors), which has compelled the fishermen to change their target species from one to another. In other words, the coastal pelagic fish fisheries in Japan have survived as a whole by employing flexible fishing over the years.¹

The total catch of Japanese sardine from the entire Northwest Pacific in 1985 was about 4.72 million tons, of which about 82 percent was taken by Japanese fisheries from the waters around Japan. This was the third largest single-species catch among the world's oceans, preceded only by the South American pilchard in the Southeast Pacific (5.81 million tons) and Alaska pollack in the Northeast Pacific (4.73 million tons). However, it is quite likely that the catch will decline again in the future, as a result of a decline in stock abundance caused by natural reasons, as has been experienced in the past. The catch was only about 9 000 tons from the entire Northwest Pacific in 1965, which is less than 0.2 percent of the current catch.

It is interesting to note the stable trend of the total catch (seven major pelagic species combined) as compared with fluctuations in catches for particular species. It is noticeable that even around 1965, which was the worst period for sardine stock, the lack of sardine production was offset by the production of other species, e.g. chub mackerel, Jack mackerel, saury and flying squid (see Figure 4). This is an important point that must be taken into account when a management scheme is established for coastal pelagic fish resources in a region as a whole.

5.1.2 Fisheries and management

Although small coastal pelagic fish in the region form a complicated multispecies resource, the fisheries harvesting these fish are simply structured compared with those for demersal multispecies resources, for which multi-gear fisheries are commonly employed. This is because of the species-specific availability of the fish to a specific gear/method, based on distribution and migratory pattern, shoaling and swarming nature, body shape, phototaxis, and feeding habits, etc. These features have determined the specific fishing method/gear for each of the target species. Table 5 shows the combination of the two.

¹The Japanese fisheries have so far experienced two extreme cases that almost caused the collapse of specific fisheries. These were the Pacific herring setnet fishery along the Hokkaido coast and the Japanese sardine fishery (purse seines, setnets and gillnets) all along the Japanese coast (see footnote ² in this Section).

('000 t)

¹ Sum of the listed species, not total catch by fishery.

² Total catch by species taken by all the fisheries.

1. Pacific saury and Japanese flying squid

   As shown in Table 5, saury and flying squid have been caught almost exclusively by a single gear fishery for each, namely, stick-held dipnet for the former species and mechanized jigging for the latter. Both use luring lights, taking advantage of strong phototaxis and the swarming nature of the fish.¹ In the case of flying squid, their greedy feeding habits also facilitate the jigging with artificial bait. Both are minister-approved fisheries, for which licences are granted on a national basis (see Section 2 and Table 2), but the management applied to these fisheries works on the basis that each is a single-species fishery.

2. Japanese anchovy

   Japanese anchovy has been caught mostly by medium/small purse seines and boat seines, and partly by setnets (Table 5). These fisheries are all governor-licensed fisheries. However, medium-size purse seine (all over the coast) and boat seine in the Seto Inland Sea are nationally registered fisheries for which the governor of each prefecture can issue licences within the limits set by the minister (see Section 2 and Table 2). They generally operate fishing almost exclusively for anchovy although the licences allow the fishermen to fish other species in some circumstances. The more severe regulations employed in the Seto Inland Sea aim to ensure harmonious operations in a relatively small and closed area of the sea (see Section 6 for details). The setnet fishery is one of the fishing right fisheries, which are subject to further strict regulations, as discussed in Section 2.

   A particular feature of the exploitation of anchovy in Japan is that the post-larvae (15–35 mm body length) and younger juveniles (35–50 mm) have been intensively harvested by the specialized boat seines that make up the “shirasu” fishery, strictly defined and subject to further regulations.² This implies that the high reproductive potential of anchovy does not require severe regulation on catching small-size, immature fish (Chikuni, 1985).

3. Japanese sardine, Japanese chub mackerel and Japanese Jack mackerel

   The majority of the catch of the other three major pelagic fish, sardine, chub mackerel and Jack mackerel, have been caught mostly by purse seine. The fisheries are composed of large/medium and medium/ small types of both one- and two-boat purse seines. The combined catch of the three species taken by these two fisheries accounts for about 77 percent of the total coastal pelagic fish catch. These fisheries are therefore characterized by being directed at a massive catch of species of low commercial value, resembling the offshore trawl fisheries in the northern region (see Section 4). This tendency can be seen more clearly with larger purse seines, whose catch of these three species accounts for more than 99 percent of the total coastal pelagic fish taken by that means, while more than 10 percent of the total catch of smaller purse seines is composed of other fish including anchovy, round herring and amberjack (see Table 5).

¹ Before the early 1950's saury was fished mostly by drift gillnet without luring lights, and flying squid by pole-and-line and handline with lights. However, the monospecies nature of the fishing was the same.

² The annual catch of “shirasu”, amounting to 60–90 000 tons, accounts for about 30 percent of total anchovy production by weight. However, the actual number of these taken is about ten times greater than that of the adult fish caught by the anchovy fishery (Chikuni, 1985).

The large/medium-type purse seine fishery (with vessels larger than 40 gross tons) is licensed by minister on a national basis (see Section 2 and Table 2). The number of vessels licensed is limited by sea area, within a total allowable number for the entire region: 377, of which 328 vessels actually operated in 1985 (304 one-boat and 24 two-boat seines). The maximum size of a vessel is also limited to 135 gross tons. The shallower zones of coastal waters around Japan are generally closed to the fishery to prevent conflicts with small-scale fisheries.

The medium-type purse seine fishery (with vessels of 5–40 gross tons) is licensed by local governor within the limit of the number of vessels¹ allocated to each of the prefectures by the minister (see Section 2 and Table 2). The total number of vessels licensed for the entire region in 1985 was 968, of which 778 actually operated.

Small purse seines (smaller than 5 gross tons) are licensed by the prefectural governor on a completely local basis. In 1985 about 1 000 vessels actually operated, fishing not only for the major coastal pelagic fish but also for other coastal pelagic fish including dolphin fish, Japanese flying fish and flathead mullet, etc.

From a legal point of view, there is no strict limitation on selecting a target fish species. The fishermen can therefore decide their fishing strategy on their own, which enables them to switch from one type of fishing to another according to the change in catchability or profitability of the fish. Operations, though, are subject to coordination and agreement with the fisheries cooperatives into which the fishermen are organized. This is an important factor to be taken into account for management purposes, which results in evening out the long-term trend of total pelagic fish catch in spite of the large and infinite changes in the abundance of different fish stocks and species composition of the fish community (see Figure 4). It should be noted that the management scheme employed in these fisheries is unable to regulate a single species catch separately from the combined fish catch, unless a sophisticated catch-quota system is enforced, which has not been adopted in Japan for practical reasons (see Section 2).

For stocks like sardine, chub or Jack mackerels, the yield curve against the fishing intensity generally becomes flat-topped beyond a certain level of fishing intensity, which is quite different from those for many demersal fish stocks, for which yield declines beyond an optimum level of fishing. This suggests a few important points for management of these fisheries: (i) when stock abundance is growing or at a very high level, reduction in fishing intensity does not result in a increase in total fisheries production; however, (ii) the catch rate (catch per unit effort) decreases (or increases) according to the increase (or decrease) of fishing intensity in such a phase; (iii) the optimum level of fishing is therefore decided mostly from an economic or social rather than a biological point of view; however, (iv) if the stock begins to decline for some natural reasons, the stock abundance and yield would continue to decline even if fishing intensity is reduced, (v) it would further decline precipitously if fishing intensity is increased or not reduced in such a situation (Chikuni, 1985).

¹The limit is generally defined by triple limitations: (i) total number of vessels, (ii) total gross tonnage and/or (iii) total engine power of all vessels.

There may be no need to impose strict regulation when stock is growing and/or very abundant. A fisheries forecasting service, if employed, would greatly facilitate the effective use of these resources in such situations (Chikuni, 1985, Yamanaka, et al. 1988). The forecasting service would also contribute a great deal to monitor the current status and to predict the probable future change of a specific stock.

Cautious fishing, however, is needed when the stock is declining. Probably an immediate reaction from the stock in question cannot be expected even if fishing intensity is substantially reduced, since no clear reversible relationship has been observed between stock abundance and fishing intensity as seen above. However, care should be taken to allow stock to maintain a certain level of reproductive potential (spawning magnitude) so that it can recover when favourable conditions arise during periods of decline or depletion. Even in this case a fisheries forecasting service would make a contribution, first by helping to achieve cautious fishing and second by helping the fisheries to stabilize by shifting target species (Chikuni, 1985, Yamanaka, 1988).

5.2 Larger Pelagic Fish

Japanese amberjack (yellowtail) and Japanese Spanish mackerel are included in this group. Both has acquired a higher trophic level in a fish community with omnivorous to piscivorous feeding habits.¹ The fish therefore behave as predators in the pelagic fish community, feeding intensively on sardine, chub and Jack mackerels, saury and flying squid, especially during their juvenile and adult stages. They are generally caught by gears specially directed at them, e.g. amberjack or Spanish mackerel gillnet, hook-and-line (troll) and setnet, etc. (see Table 5).

Amberjack was caught almost exclusively by setnet until the late 1950's. However, the catch using other gears (hook-and-lines, purse seines and gillnets) has gradually increased thereafter as the setnet catch has gradually declined. The recent catch by the other four types of gear far exceeds that by setnets (i.e. setnets, 12 000 tons: purse seine, 9 000 tons: angling, 7 000 tons: gillnets, 5 000 tons: for a total of about 33 500 tons in 1985). This has probably been caused by a change in the availability of the fish, especially to the setnet, while abundance and the total catch from the waters around Japan appear to have remained stable over the years (Chikuni, 1985).

A peculiar feature of the exploitation of amberjack in Japan is the quantity of fry and juveniles collected alive to be used as seedfish for aquaculture. The total number of seedfish supplied annually for aquaculture has been about 70–80 million in recent years, and the total annual production of aquaculture is about 150 to 155 000 tons, which is about 4.5 times that of the current catch of natural fish. However, no negative effect has been observed so far on natural stock abundance (Chikuni, 1985).

Spanish mackerel has been caught by various types of gear including gillnets, trolls, handlines and setnets, mostly along the southern coast of Japan. The catch taken in the Seto Inland Sea has been large, usually accounting for more than 50 percent of the total catch - (6 000 tons out of 11 000 tons in 1985), but this will be discussed in further detail in Section 6 of this paper.

¹See Footnote ³ (ii) of this section for some observations on the classification of Japanese sea bass, and Section 6 for details of the stock in the Seto Inland Sea.

The fisheries exploiting these two species are mostly of small scale, except for large-scale amberjack setnets in the fishing right-fishery, and all are categorized as governor-licensed fisheries (see Tables 2 and 5). The principles employed in licensing and managing these fisheries are those of a single species for each, again with the exception of amberjack setnets because of its large amount of by-catch of other species.

It is interesting to note the stable trend of the total catch (seven major pelagic species combined) as compared with fluctuations in catches for particular species. It is noticeable that even around 1965, which was the worst period for sardine stock, the lack of sardine production was offset by the production of other species, e.g. chub mackerel, Jack mackerel, saury and flying squid (see Figure 4). This is an important point that must be taken into account when a management scheme is established for coastal pelagic fish resources in a region as a whole.

A peculiar feature of the exploitation of amberjack in Japan is the quantity of fry and juveniles collected alive to be used as seedfish for aquaculture. The total number of seedfish supplied annually for aquaculture has been about 70–80 million in recent years, and the total annual production of aquaculture is about 150 to 155 000 tons, which is about 4.5 times that of the current catch of natural fish. However, no negative effect has been observed so far on natural stock abundance (Chikuni, 1985).

Spanish mackerel has been caught by various types of gear including gillnets, trolls, handlines and setnets, mostly along the southern coast of Japan. The catch taken in the Seto Inland Sea has been large, usually accounting for more than 50 percent of the total catch (6 000 tons out of 11 000 tons in 1985), but this will be discussed in further detail in Section 6 of this paper.

The fisheries exploiting these two species are mostly of small scale, except for large-scale amberjack setnets in the fishing right-fishery, and all are categorized as governor-licensed fisheries (see Tables 2 and 5). The principles employed in licensing and managing these fisheries are those of a single species for each, again with the exception of amberjack setnets because of its large amount of by-catch of other species.