Miscellaneous Mollusc Resources of Pacific Islands
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SPC/lnshore Fish. Res./WP2 29 February 1988 ORIGINAL : ENGLISH ( Noumea, New Caledonia, 14-25 March 1988) HISCELLANEOUS MOLLUSC RESOURCES OF PACIFIC ISLANDS BY Dr A.D. Lewis Introduction l Molluscs (Phylum Molluscs) we a diverse array of "shellfish", which include bivalves (clams, cockles, oysters, mussels - Class Pelecypoda) ,gastropods ( snails, abalone, seahares- Class Gastropods) and cephalopods (squids, octopus, cuttlefish - Class Cephalopoda). These support large marine fisheries, world landings of molluscs exceeding 6 millions tonnes in 1985 (Anon, 1987) and dominated by cephalopods ( 1.67 million mt,), clams, cockles and arkshells ( 1.6 1 million mt.) and oysters ( 1.03 million mt). 2. Previous sessions at the workshop have considered in detail the molluscs of major commercial importance to Pacific Islands. This include molluscs harvested primarily for Industrial purposes (eg. trochus, green snail and pearl shell, for their nacreous shell interiors) as well as those harvested primarily for human consumption (giant clams). 3. There is in addition, however a wide range of molluscs harvested throughout the Pacific Islands for subsistence purposes and in some cases small scale commercial exploitation. Many are gleaned from a variety of inshore habitats, including mud flats, mangrove roots, sandy beaches, reef flats and rubble areas. These molluscs are commonly collected by women, and have traditionally served as important reserve food sources during times of bad weather or poor line fishing. In (tensely populated atolls, they may become a primary fooAsource, Zann ( 1985) noting that in South Tarawa (Kiribati), landings of three lagoon bivalves exceed that of all finfish combined. 4. Othermoreactivemolluscsaretakenwithluresorbaits(cephalopoda).whilstothers are trawled (scallops). Some additionally offer potential for mariculture (pi-, -, -, -, etc). Table 1 lists the main of molluscs exploited for food throughout the Pacific Islands. This does not include molluscs harvested for other traditional uses. eg. artefact manufacture (Pernetta and Hill, 1983) or as collectors items (Parkinson, 1982). SPC/lnshore Fish. Res.lWP2 Page 2 5. Richard ( 1983) provides estimates of mollusc productivity in French Polynesian high volcanic islands and atolls of 230 kg/ha/yr and 50 kg/ha/yr, respectively. Mollusc productivity on larger Islands further to the west Is likely to be even higher, underlining the potential importance of these resources to island ecosystems. This paper reviews available information on Pacific Island miscellaneous mollusc fisheries and their management requirements. Noatnal catches of miscellaneous molluscs 6. Data on inshore mollusc fisheries is not readily available for most Pacific Islands, a situation which extends to artisan81 and subsistence fisheries generally. Six countries record miscellaneous mollusc production for 1985 (Anon, 1987), as follows : The reliability of these figures is however uncertain. Cook Islands 236 mt (includes trochus) Fiji 2770 mt ( includes estimated subsistence) Kiribati 3286 mt New Caledonia 40 mt Western Samoa 48 mt 7. Fiji, where some relatively detailed data are available, provides a signal example of the importance of m inshore mollusc fishery in the lm river fishery for kai (-1 throughout the two main islands. This has provided commercial sales of approximately 1400 mt p.a. since 1983 (Lewis, 1985). Table 2 also lists sates volumes of other molluscs in Fiji which amounted to 144 tonnes, with an estimated value of F$ 1 12,000 In 1986. 8. Notwithstandingthe general lack of data on miscellaneous mollusc catches, the following sections consider the present status of mollusc fisheries, and their potential for further development. 9. In terms of current production, bivalves ore the single most important group of molluscs, and a very wide variety of species is ~~ed(Table l). &&&a genus generally restricted to mud/sanA/ mud habitat is pre-eminent amongst these, and there is evidence of depletion in some areas due to its heavy harvest, in some cases over centuries of exploitation (Swadling, 1982- Papua Coast; Zann, 1975- Tarawa). 10. The Twwa lagoon fishery for "te bun" (-8 maculoq) prwides a swle protein source for the rapidly increasing population of South Tarawa, particularly for those families outside the cash economy, and the annual harvest has been estimated to be as high as 1800 1. per year (Bolton, 1982). The resource appears to be in need of some management input and this issue is now being addressed (Mees, pers. mm.). SPC/lnshore Fish. ResJWP2 Page 3 1 l. In Fiji also, m (h--kaikw) prwides the larpt mwine mollusc sales volume (approx. 100 1- Table 2) and the genus is also harvested in Tonga. Techniques for the culture of m have bmwell developed in South East Asia (Broom, 1985) ancl Malaysia exported 40,000 t. of &w&a crm in 1982, based on coastal mudflat cultivation of collected natural seed (Wow and Lim. 1985). This species apparently occurs in Papua New Guinea (Swadling andChowning, 1983) where it is harvested for subsistence, and may occur elsewhere in Melanesia. A. mis alsu hurvested in Pqua New Ouinw. 12. In the coral sand Itgpm of Polynesia, m generally becomes of less importance, with and hhismore commonly harvested. 13, The Fijim kai (m)fishery has been mentioned ewlier. This species is found in rivers throughout Melanesia, in fresh water under tidal influence, but appears to be of only minor importance elsewhere. The relatively low price (approx. 20c/kg whole animal), ready availability and non-perishable nature of the product (it is sold live and can be kept for up to a week) establish it as possibly the cheapest available protein source in Fiji, Approximately 1400 tonnes are now marketed annually (this does not include a sizeable subsistence catch) and although production has essentially stabilised since 1983 ( Lewis, 1985), there are concerns that the resource may be harvested at close to its maximum sustainable level. Yield estimates are required with some urgency. 14. The sum scallop (v-,with the smaller /i elm, supports 8 scallop fishery off the coast of central Queensland (22.-26. S) (Dredge, I.P. 1, this workshop). Annual catches (meat weight) have been in the range 600- 1200 mt p.a. Recent trawl surveys in the north of New Caledonia at in a similar latitudinal range ( 19.-20. S) have revealed the presence of scallop beds there (Clavier and Laboute, 1 987) and It Is possible a small annmmial fishery for mw Welop. The standing bimass in m arm of approximately 700 km2 was estimated at 3000 mt. Quantities of ~leurcmec@are t&m incidentally in the Gulf of Papua trawl fishery, some of which is marketed. Scallop fisheries are vulnerable to over-exploitation because of the high product value and erratic recruitment Dredge ( I.P. 1) argues that recruitment over fishing may already be occurring in the Central Queensland fishery. 15. With the exception of the examples mentioned, it is unlikely that bivalve resources on most Pacific Islands are being exploited at even moderate levels. Their importance to subsistence consumption should however be borne in mind, as well as their susceptibility to depletion and to unfitness for human consumption through pollution or environmental degradation. 16. A similarly wide range of gastropods is exploited, mainly for subsistence purposes. With the exception of trochus and green snail, exploitation levels are generally believed to be tow (see, for example, Table 21, and abundant bivalves are generally harvested in preference. There are however a few cases where fishing pressure on particular species is increasing eg. lurkm (ariri) on Aitutaki (Cook lsl~),and sum8 assessment of the rmmw be required. SPC/lnshore Fish. Res./WP2 Page 4 17. The generally low levels of exploitation of gnstropods, other than trochus and green snail, isinmwkdmtr&btheWi~,whthe~~~(~is the second most valuable fishery resource after spiny lobster, and second only to finfish as a protein remm (Brwwnell andstevely, t 981 ), The red-lipped skmb (- together with the smaller -, is however prdxbly tk mast imporht gosbpod taken for subsistence usage inthe Pacific Islandregion. 18. Specimen or collectors shell, those taken for sale to tourists and to specialist shell collectors, provide a special case. Attractive shells, mostly gastropods of the genera Qw, m&!&&&,m,m, m, m &, but 81~biv81~ (P~kiflsOn, 1982). may have a value in the shell trade many times that as a food item. This can lead to intensive collection of species which nuy already be relatively rare. Parkinson ( 1982) outlines a series of simple conservation measures for a collectors shell industry, including minimising habitat damage during collection. All countries have some potential for specimen shell development. 19, Despiteaworldcatchofwer 1.6 million tonnesinrecentyears(Anon, 1987)andthe potential to increase this by many tirnes,cephalqmd fisheries are of minor Importance In the countries of the South Pacific, 20. Octopus, primarily cvrn, are collected in small quantities from reef flats, using lures. traps or hooks. Approx. 7mt was marketed in Fiji in 1986 (Table 2); Hawaiian landings averaged only 4.6 mt. between 196 1- 1979 (Kramer , 1986), and New Caledonian landings 8- 17 mt p.a. since 1983 (Palladin, pers. mm). 21. Lagoon squid (Sfiololfiuthis 1- are captured occasionally, as are cuttlefish (Amesbury et al. , 1986), and small quantities of squid are marketed as trawl by-catch in Papua New Guinea. Surveys of near-shore ommastrephid squid resources have been carried out in several countries eg. Fiji with generally disappointing results, the main species (m-) being of smmcbry market importance and used primarily 8s bait. This species, which Voss ( 1973) speculates to have a very large potential yield from the central eastern Pacific Is often common around FAD'S and in near-shore waters, and may have local potential as a bait species for individual fishermen operating vertical longllnes or ika shibi gm.An artkenal fishery exists for the endemic -us hawaiiensb off Hawaii, ancl may hove possibilities for expansion (Roper et al., 1984). The red ocean squid (mastrog6bartrmi) a species of grmt commercial importance, mrsin waters south of 20.