SPC/Inshore Fish. Mgmt./BP 27 1 June 1995

ORIGINAL : ENGLISH

SOUTH PACTFIC COMMISSION

JOINT FFA/SPC WORKSHOP ON THE MANAGEMENT OF SOUTH PACIFIC INSHORE FISHERIES (Noumea, New Caledonia, 26 June - 7 July 1995)

A REVIEW ON THE RESEARCH AND FISHERIES OF BARRAMUNDI, REEF FISH, DUGONGS, TURTLES AND SPANISH MACKEREL IN THE PAPUA SIDE OF THE TORRES STRAIT

by

B.D. Kare Dept. of Fisheries & Marine Resources Port Moresby, A Review on the Research and Fisheries of Barramundi, Reef fish, Dugongs, Turtles and Spanish mackerel in Papua New Guinea side of the Torres Strait.

Barre D.Kare

Department of Fisheries and Marine Resources Research and Surveys Branch Kanudi Fisheries Research Station P. 0. Box 165, Konedobu, Papua New Guinea.

Introduction

The Torres Strait Treaty between Australia and Papua New Guinea was signed on 18 December 1978. The Treaty establishes the Protected Zone within which both countries have rights and responsibilities. The main purpose of the Protected Zone is to protect the traditional way of life and livelihood of the traditional inhabitants, including traditional fishing.

Several marine species in the area are common to both Papua New Guinea and Australia. Barramundi are fished throughout northern Australia and southern Papua New Guinea. Prawn stock occur within the area and extent into the Gulf of Papua arid the Gulf of Carpentaria. The migration of tropical rock lobsters provides an example of a common stock that must be fished and shared. Dugongs and turtles occur throughout the area and these are important to the traditional way of life of the inhabitants.

The purpose of this review is to update our understanding on the current status of the commonly used or shared resources of the Torres Strait from the PNG side of that region and to brief on this to the Australian and PNG scientists and officials in a technical meeting scheduled to review the Torres Strait Region fisheries in the later part of 1995.

The review concentrates on the five fisheries (barramundi, reef fishes, dugongs, turtles and Spanish mackerel) that are currently been exploited by the local fishermen.

Barramundi (Lates calcarifer) Research and Fishery

Past history - Research

The early history and development of the barramundi research andfishery has been described by Dunstan (1961, 1962) ; Reynolds and Moore (1973, 1982); Moore (1982) Anon (1979, 1980) and Opnai

VOL 1/630 2 1 and Tenakanai (1987). These studies were conducted to understand the biology and ecology of the species as a result of a major i commercial enterprise in Western Papua. i When the Division of Fisheries was established in 1954, under the then Department of Agriculture, Stock and Fisheries, a series of | surveys were undertaken to estimate the density of the population : (Dunstan 1961, 19S2) . After 1961, further surveys were conducted I in the area to further gain information on the commercial quantities. The results of these have not been published, due to ' incomplete records and in many cases the information gathered was lost. In 1970, detailed investigation commenced and considerations were given to such factors as movements, growth, mortality, reproduction, commercial yields, economic viability and conservation measures (Reynolds and Moore, 1973; and Anon, 1979 and 1980) . The aspects of the fishery has been reviewed by Opnai and Tenakanai (1987).

Distribution and Abundance

The species distribution and abundance is confined to the southern part of the country's coast and has been described by Dunstan (1961 and 1962); Reynolds (1972, 1978) and Moore (1980). It ranges from the Mullins Bay in the east to the Irian Jaya border in the west. It is most abundant in rivers with substantial lake and swamp systems and with extensive deltas. A high concentration of the population exists in the Gulf of Papua, with it's deltaic system to the Fly, Kikori and Purari Rivers. It is less abundant on the east coast which lacks extensive swamps or deltaic systems. The eastern rivers are short and fast flowing.

Age and growth

Reynolds and Moore (1982) used length frequency analysis and I length increment data from tagging to determine growth rate of ; barramundi. They seined extensively in the coastal waters of western Papua New Guinea (P.N.G).Such an extensive seining has , , provided the unbiased length frequency distributions needed to determine year classes from modal progression. From their data analysis, they calculated mean lengths at age 1, 2, 3, 4 and 5 (years)of barramundi in Papua New Guinea to be 328, 454, 566, 663 and 750 mm respectively and suggested that this represents the whole population. The life history of this fish is complex and the growth rates vary considerably between age classes. Reynolds and Moore (1982) showed that growth is apparently slower between 3

February and September and varies considerably during different life stages. Fish in freshwater have a much higher condition factor than those in salt water and are thus likely to grow much faster.

Mortality rates

The population dynamics of barramundi was studied by Reynolds (1978). He estimated the mortality rate using the Ricker/Beverton Holt model and divided the population into four cohorts according to the biological stages. He suggested that the 4th cohort makes up the commercial fishery (fish > 55 cm fork length). However, he showed that the fishing mortality was highest in the first cohorts (i.e fish < 35 cm fork length). This is surprising, as this group does not feature in the commercial catches. The most likely reason that appear to contribute to such a high mortality (fishing mortality) in the first cohort (~ 1 year old fish) is the high exploitation of this size fish in the coastal waters by the local artisanal fishermen.

Spawning migration

The spawning migration from inland waters to the coastal waters (catadromous species) is from September to January, corresponding with the dry season in the area (Moore and Reynolds 1982). Most fish that take part in this spawning migration are 3-4 years old. Moore (1982) indicated that spawning migration is subject to substantial lowering of inland water level. Post-spawning migrations back to freshwater also occur and some fish may repeat the spawning cycle but not every year. The fish that move from inland waters to the coastal waters for spawning, do not become resident in the coastal waters, but return to the same general area from which they migrated.

Reproduction

Moore (1982) identified a major spawning site between Sigabaduru and Jarai with a minor one at the Kiwai Island. The species is a protandrous hermaphrodite, that is it matures first as male and later changes to a functional female. The fish becomes sexually mature in the 4th year (590 to 690 mm fork length), at this stage they are male and at the age of 8 to 9 years the majority become females. There are some primary females which mature at 73 cm or 6 years. Fecundity is high, increasing with fish size. Moore (1982) sampled from fish lengths of 110 cm and 115 cm (fork length) which gave an estimates of 10,000,000 and 32,200,000

VOL I / 632 4 respectively. Spawning occurs in the coastal waters, where the eggs hatch and the larvae (< 5 mm fork length ) move into neighbouring coastal swamps during the months of November to February with the floods and spring tides. The swamps begin to dry in June - July and by August - September they are completely dry. Most juvenile barramundi ( about 200 mm fork length) leave the swamps at this time and migrate to the coastal waters and move eastward stopping for periods around the mouths of creeks, but do not enter. By the end of the first year, some have entered the estuary of the Ply River. The recruitment to the freshwater regions is by 1 + year old fish. This recruitment is not uniform as some move into the freshwaters after 1 or 2 years later. Not all fish move into the inland waters as there seems to be aresident population of all ages that remains in the coastal waters.

Recent history - Research

The distribution, biology and ecology of this most valuable resource are reasonably well understood (Reynolds and Moore 1973 and 1982; Reynolds 1978; Moore 1979, 1980 and 1982; and Anon 1979 and 1980). No adequate information however, is available on the dynamics of the fishery and the total fishing effort involved in the fishery. During the period 1989 to 1990,two research projects were conducted, particularly to (1) . gain information on the total fishing effort involved in the fishery, both in the coastal and inland waters and (2) .estimate seasonal abundance of juvenile barramundi in the coastal water. The former project was completed in 1989 and this involved interviewing of individual fishermen in the inland and coastal fisheries (Mobiha and Murri 1993) . They estimated that a total of 200 fishermen are engaged in the coastal fishery and that each have approximately one barramundi gill net. The largest concentration of the fishermen and nets appear to be located at the Torro Pass, in the southern bank of the Fly estuary (Katatai and Sui villages). This narrow channel is believed to be the migration route for barramundi to and from the spawning ground. In the inland fishery, most of the barramundi fishing occurred in the lower Lake Murray villages (Mobiha and Murri 1993) . This is due to easy access for the fishermen to sell their catch to the freezer boats or to the land based fish factory at Boboa.

The second study concentrated on the seasonal abundance of juvenile barramundi in the coastal water. Samplings were conducted by setting gill nets in the area west of ; from

VOL 1/633 5

Daru island to the mouth of Binaturi River, to the west. This study was instigated to monitor the catch of the 10 - 15 cm fork length size of fish, which appears to be the dominant size composition in the Daru market. Furthermore, the sale of juvenile barramundi (10 - 50 cm fork length) is banned at the Daru market. Estimated individual juvenile fish sold at the market ranges from 20 to 60 per day. With this current rate of exploitation, the estimated annual catch for these size fish would amount to 15,000 fish (DFMR, Fisheries annual report, 1993). This rate is believe to be high and this could have negative effects on the stock of adult fish (Mobiha 1993). The management measure (ban on sale of juveniles at Daru market) has not been effectively enforced, and enforcement should be implimented as a matter of urgency.

Mobiha (1993) has shown that there are two seasonal peaks in abundance per year for the juvenile fish in the coastal waters, one in March - May period and the other in August - September period. The former peak coincides with a peak of monthly rainfall in the area and the latter with the driest period of the year in the area (Mobiha 1993). The results of this study have further demonstrated a need to review the prohibition notice of 6th October 1983 (management measure No. G67). This notice prohibits the taking, selling and exporting of barramundi, which are between 10 to 50 cm in fork length and also restricts the use of gill-nets that are less than 15 cm mesh sizes within the coastal waters between Sui village to the east and the mouth of Binaturi River to the west between the months of January and July. However, it is recommended that the notice should be changed to accommodate only the peak periods of juvenile barramundi recruitment and not just a general ban for the months of January to July.

Further research on barramundi has been currently halted, due to staff being assigned to other priority research projects.

Barramundi Fishery

Past history - Fishery

The history of the development of the fishery has been reviewed by Opnai and Tenakanai (1987). The Division of Fisheries of the then Department of Agriculture, Stocks and Fisheries began the investigation in 1957, in the vicinity of Port Moresby. By 1961, the survey extended to the areas of the Gulf of Papua, with a shore base at Daru, in the Western Province.Commercial fishing areas were identified at , Galley Reach, Lake Murray,

3L.I / 634 6 Daru, Morehead and Bensbach. Processing facilities were set up near these fishing grounds at Port Moresby, Yule Island, Lake Murray and Daru. The only records of the catch in 195 9 and 1970 are for the Daru based fishery, which produced 206.00 t and 134 t of whole fish respectively (Opnai and

Tenakanai 1987). In 1979, the fishing operations expanded to include (1) Daru coastal fishery; (2) refrigerated fishing vessels and (3) village based freezers (Opnai and Tenakanai 1987).

The coastal based fishery (Daru) was based on the annual spawning migration (September to January). The local fishermen were engaged in the fishing operations and the catch was either taken to the land based factory at Daru or to the freezer boats anchored close to the fishing grounds.

The freezer boats (14 - 16 m) with freezer capacities of 5 - 12 t fished at the mouth of the during the spawning migration. This operation moved up to the Middle Fly and the Lake Murray areas during the non spawning migration. Catches were usually lower in the inland waters than the coastalwaters, but sometimes this was reversed when the water level dropped.

In the Middle Fly at Bosset and at Samari in the Fly estuary, approximately 5 t capacity freezers were established. The catch to these freezers were supplied mainly from outboard - powered dinghies and dug out canoes, using 160 - 200 mm mesh gill nets. The products (filleted and packed) were sold either to the freezer boats or to the factory at Daru.

Recent history - Fishery

In the 1980's, four freezer boats were operating, two Australian and two Papua New Guinean. During this period, the average estimated catch for local fishermen ranged from 15 to 20 kg/100 m net/days in the Daru area (Moore 1982). Barramundi fishery operations in Baimuru (northern Gulf) have collapsed and the past description of that fishery is given by Opnai and Tenakanai 1987) . In the Middle Fly fishery, which is part of the Daru based fishery (Bosset, Obo and Lake Murray areas), no description of the facilities and their operations were available during the course of writing this paper. Currently, there is one fishing operation in the Western Province; and that is at Dairu, which includes the village based freezer facilities in the Middle Fly

VOLI/63S 7 area. The Daru based fishery has been described by Opnai and Tenakanai (1987). This fishery exploits the area in the Middle Fly (Inland Fishery) and along the coast from the Fly estuary to the mouth of the Binaturi River, west of Daru. Monofilament and multifilament gillnets, with 178 mm mesh size and 100 m long by 4 m or 25 meshes deep are being employed. These nets are set at right angles to the shore and are cleared every S - 8 hours. Catches are landed directly to the land based facility at Daru or the freezer boats anchored at the fishing ground.

Table 1 shows the past and current annual landings for the years 1971 to 1994 for the Daru based fishery. These catch statistics are inconclusive, as no records were received from the Inland fishery for some years. The Daru based fishery experienced a period of fluctuation until 1984/1985 period when the total catch was at its lowest (Table 1). Figure 1 shows the first approximate estimation of the long-term M.S.Y of 120 tonnes per year for the Daru based fishery, based on the data provided by Opnai and Tenakanai (1987) for the period 1980 to 1985. However, according to Mobiha (per. comm.), at the current rate of exploitation and population size of the species, the M.S.Y could be in the vicinity of 50 tonnes. Moore (1982) has estimated that the average production is in the vicinity of 270 tonnes per year. Catch and effort data has not been consistently available since the commencement of the fishery. Accurate estimation of catch and effort data is currently a problem, as information on this aspect of the fishery is not easy to gather. The reluctance of the fishermen and commercial operators to provide these data has been a problem. No such calculations have been done so far at the current status of the population. Figure 2 shows the regression analysis of catch by years from 1971 to 1994, with a line of best fit. There is a high significant negative correlation between the catch and the years (P < 0.0001) . This indicates that the commercial catch has declined drastically, although there maybe inconsistency in the fishing operations of the commercial operators. This decline began to appear in 1984. Landings in that year in Daru had fallen to 8 7 tonnes, compared with an average annual landing over the previous ten year period of about 23 0 tonnes. The reasons for this decline are unknown, but it could relate to an extensive market developed in the Daru area for juvenile barramundi. These size (10 cm - 15 cm) have being heavily exploited since 1982 by use of small seine nets (see barramundi research section) along the coastal areas, west of Daru. The predominant sizes in the commercial catches of barramundi consist of > 4 year old (> 65 cm). However, Reynolds (1984) estimated from his work on the population dynamics of this

OLI / 636 8 species, that the highest fishing mortality occurred in the sizes < 35 cm or 1 year olds. This is surprising as this group does not feature in the commercial catches. One factor that contributes to the high mortality in yearling barramundi is the high rate of exploitation. In the early 1980's juvenile barramundi were targetted and it is suggested that, this is the key factor in the current decline of the adult stock.

Table 1. Annual landings of barramundi at the Daru based fishery (whole weight, metric tonnes) for 1971 to 1994 (Sources: Opnai and Tenakanai 19 87; and Fisheries Research Annual Report 1979 and 1993) . Most records are incomplete (e.g. 1989 period)

Years Inland Coastal Tot,

1971/1972 146 248 394 1972/1973 56 185 241 1973/1974 97 187 284 1974/1975 31 321 352 1975/1976 28 151 179 1976/1977 26 184 210 1977/1978 55 115 170 1978/1979 34 173 207 1979/1980 221 1980/1981 308 1981/1982 328 1982/1983 187 1983/1984 139 1984/1985 87 1985/1986 32 1986/1987 67 1987/1988 37 1988/1989 63 1989/1990 1990/1991 11 1991/1992 43 1992/1993 7.8 38 45 1993/1994 19 17 36

Anecdotal evidences have suggested that the catch has also declined in the main river channel (Fly River) in the Middle Fly (B. Shackles, a licenced commercial operator per. comm.). He further mentioned that there has been a loss of habitat for the 9 species, because of an increase in the sediment loads of the main river channel, caused by the operations of the Ok Tedi copper mine. He stressed that the fish tend to avoid the main channel and migrate into the off-river waters bodies (i.e oxbows and lakes) and tributaries. No fishing licences have been issued to fish the oxbows and lakes, apart from Lake Murray to make a comparison. Concentrated research work has to be conducted inorder to highlight the reasons for the current decline in the catches and that strict enforcement of the current ban on the catch of juvenile fish in the coastal waters has to be enforced. Because of this the fishing boats have being forced to venture into other fishery.

Recommendations for the improvements of the current measures

* That the restriction on the use of nets of mesh sizes of less than 15 cm between the period of January to July be changed to accommodate only the peak months (March to May and August to September) of juvenile recruitments to the coastal waters. Beside these months, fishing would still be conducted by the fishermen, but the closure or net restriction period would enable the major juvenile barramundi migrating into the freshwaters.

* That the enforcement branch of the Division of Licensing and Enforcement of the Department of Fisheries and Marine Resources based at Daru should work in collaboartion with the coastal village councils. Enforcement of the regulations should be given to the local village Councils. Fishermen caught harvesting these size fishes should be prosecuted. Money collected from court proceedings should than be channelled to the councils as this would become one of their revenue making venues.

Reef Fish Research and Fishery

Reef Fish Research

There have been no stock assessments of reef fish in the PNG side of the Torres Strait. A survey in 1993 by the Research and Surveys Branch, Department of Fisheries and Marine Resources produced interesting results. This survey employed two commonly used methods; (1) handlining and (2) spearf ishing, and was conducted within the Warrior reef complex. A total of 915 man hours of handlining produced 187 fish, comprising 23 species, with a weight of 103 kg. The composition of the catch was

3L I / 638 10 dominated by Lethrinus fletus, with 43% by number, Choerodon schoeleini (23%), Lutjanus carponotatus (7%) and the remaining 27% comprised the other species.

A total of 181 fish, belonging to 17 species were captured by spearfishing, with a total weight of 89.4 kg. The catch was dominated by Plectorhinchus flavomaculatus, with 49% by number, Sigahus lineolatus (15%), P. nigrus (8%), Lutjanus carponotatus (8%) and the remaining 20% comprised the other species. The estimated catch rate for this method was 1.02 kg/man - hour, compared to 0.113 kg/man - hour by the handlining method.

More research work is needed to estimate the abundance and distribution of the commonly exploited fish species(Table 2). This fishery appears to be under exploited and there should be emphasis on encouraging local barramundi fishermen to venture into this fishery.

Reef Fish Fishery

A survey of catch records obtained from the Daru reef fish operators indicates that catch has fluctuated with the lowest occurring in 1991 (Table 2) . This has not resulted from of the overexploitation of the resources, but could relate to the inconsistency of fishing operations.

In 1989 and June of 1991 no catch data were recorded. As this fishery is an artisanally based, there is a problem of reaching the fishing grounds (reefs) during the rough seas by small fishing craft (dinghies with out board motors). These small fishing craft are used in this fishery.

Table 2. Annual catch (metric tonnes) for all reef fish species landed at the Daru artisanal based fishery (Sources: P. Polon pers. comm. and Fisheries Research Annual Report 1993)

Years 1986 1987 1988 1989 1990 1991 1992 1993

Catch 18.7 19.9 5.9 nd* 3.1 3.38 21.7 13 .6 * no data recorded

The fishery is based on Lethrinids/ Lutjanids, Haemulids, Siganids and Hemiramphids. It is mainly carried out by the local people living on . Annual landings since 1986 are presented in Table 2.

VOL 1/639 11 Dugongs {Dugong dugon) Research and Fishery

Dugong Research

The dugong (Dugong dugon) which is restricted to the sea is the only extant marine herbivorous mammalian. Dugong populations have been seriously reduced by hunting in most of their extensive tropical Indo-Pacific range (Marsh 1985). This species is now being regarded as an endangered species in the world. Dugong populations in the Torres Strait have been hunted by the local hunters since the nineteenth century (Johannes and McFarlane 1991). The Torres Strait supports the remaining major stocks of dugongs (Johannes and McFarlane 1991) . However, these stocks are subjected to heavy exploitation, because of the increased efficiency of hunting techniques (Hudson 1985 and Prescott 1985) .

The safe future of this animal is not guaranteed. Because of this and it's significance to the local inhabitants of the area, a series of surveys were conducted by the scientists from Australia and Papua New Guinea. The primary aim was to gain information on the animal's distribution and abundance. An aerial survey of the Torres Strait was conducted by Marsh et al (1984) and Marsh (1985) . These surveys estimated a population of 1455 +/- 276 SE, with a density of 0.11 +/- 0.02 SE dugongs per square kilometer,' including all the dugong hunting grounds in the region. These estimates were based on the survey blocks on a map scale of 1:250,000. It was not possible to obtain more precise population estimates, because the proportion of dugongs sighted in various aerial survey conditions were not calibrated. They have also documented the biological aspects of the dugong, including such factors as life history, growth, movements and population dynamics. Hudson (1985) carried out a survey of dugongs that were sold at the Daru market between 1978 - 1982 (discussed below).

The current research and management of this species comes under the P.N.G Department of Environment and Conservation. However, since the initial studies (Marsh et al 1984; Hudson 1985) on the fishery and biology of the species in the P.N.G side of the Torres Strait, no further work has been conducted until now.

Dugong Fishery

The first indication of dugong stock being overfished in the area came from the data landed at Daru (Hudson 1985). Before the World War 2, about 25 dugongs were caught per year, according to the Papuan Kiwai fishermen, Hudson interviewed. In the 1950's and 12 1960's the Kiwai fishermen were encouraged to kill dugongs, turtles and fish to supply the newly established hospital, schools and jail and to supply the local market. This resulted in an increase in the dugong kills to 75 per year (Johannes and MacFarlane 1991) .

In the 1970's when the barramundi and lobster fisheries (which are high export price species) were introduced, there were unfortunate implications for the dugong population (Hudson 1985) .

Strong monofilament gill nets were introducted for catching barramundi along the west coast. The fishermen soon discovered that the nets could also be used also to entangle dugongs. Because of this reason, the number of dugong kills increased again. Hudson (1985) has estimated the number of dugongs passing through the Daru local market. She mentioned that the number rose and declined during the period the official statistics were collected; 68 dugongs were measured in the last six months of 1978, 218 over all months in 1979, 97 in 1980 and 70 in 1981. In the first three months of 1982, 17 animals were landed at the Daru market. Since then, no data has been collected. It became very difficult to obtain a reliable estimate of the number of dugongs caught on the Papuan side of the Torres Strait through informal interviews. However, there was general agreement that the number declined further in 1983 (Hudson 1985) . This decline occurred despite an increase in the availability of motorized canoes and dinghies and an extension of hunting grounds (see Hudson and Prescott 1985 for hunting methods used). Because of this decline, in 1978 the Maza Wildlife Management Committee was formed, comprising the dugong hunting villages.

The Government of PNG has declared this animal as a "national animal" under the Fauna Protection Act (details are found in Hudson 1985 and Johannes and McFarlane 1991) .

The restriction on hunting by only traditional means and on the sale of the animal at present at the Daru market has made it impossible to collect accurate catch statistics. Between 1992 and 1994, a total of 17 individuals were butchered and sold at Daru market, with a strong warning from the Maza Wildlife Authorities about the killings. Obviously, this estimate is inconclusive, as the Kiwai fishermen catch them for their own consumption and are rarely seen by the Government officers based at Daru. The consumption of the meat is kept secret. Locals know that the dugong is endangered animal and as well as protected by the Maza Wildlife Committee and the Government of PNG and so they are not 13 willing to co-operate and provide information. Dugong hunting takes place all year.

Recommendations

* That the efficacy of the Dugong Management developed by the P.N.G Department of Environment and Conversation, Division of Wildlife at Daru be reviewed, with close collaboration with the local hunters themselves.

* That the awareness compaign both on the local radios and public notices be carried out to the local hunters in regards to the importance of conserving the species for future generations. This has to be done, as most catch landings and consumptions are done in secret, without the knowledge of the government officers.

* That a survey be conducted on the dugong kills since 1978 (i.e collect specimens, bones or tusk or interview local hunters) to estimate the number caught during the past and current period of the Maza Wildlife Management. These data should concentrate on the sex, data of capture, area of capture, method of capture, and reasons for'the capture.

Turtles Research and Fishery

Past Research

There are seven extant species of marine turtles in the world (Spring 1980) . Of these number, only six are found in P.N.G, including the Torres Strait (Limpus and Parmenter 1985). Table 3 lists the species that occur in this region. The comprehensive biological aspects of each species has been reported elsewhere (e.g. Limpus and Parmenter, 1985). In the Daru area, past work include that of Prescott (1985), who carried out preliminary observations on the biology of the green turtle {Chelonia. mydas) .

Detailed analysis of the green turtle has been documented by Kwan (1991), concentrating on the fishery, biology and implications for management of this species, as partial fulfilment of the requirements for an MSc degree, James Cook University. Her comprehensive description of the turtle fishery was conducted between October 1984 to December 1987. Information was gathered by interviewing the local fishermen. Results indicated that there was an increase in the number of fishermen who caught turtles and that this was contributed by an increasing proportion

OL I / 642 14

of these fishermen who had no traditional history of turtle hunting. High number of turtles, particularly females were taken between September and December, when a large seasonal migration of turtles transit through the area to rookeries on the Great Barrier Reef (Kwan, 1991) . Over 60% of the females examined were preparing for breeding.

Spring (1980) carried out general survey of the turtles in P.N.G (including the Daru area). All species are experiencing serious survival problems and all are currently considered to be one of those endangered animals on the global basis (P. Polon per. comm.).

Recent Research

Research into the monitoring of the Daru turtle fishery comes under the P.N.G Department of Environment and Conservation. No extensive work has been done in relation to the harvesting and management of this resource, since the early studies of Spring (1980) and Prescott (1985). The Fisheries Research staff based at Daru have began to gather information from fishermen, including such factors as date of capture, species, sex, carapace length, area (reef) captured and method of capture. The preliminary indications of their work are that the traditional method of harpooning (see details in Hudson, 1985 and Prescott, 1985) is fast being replaced by the use of motorized dinghies or canoes and monofilament gill nets. This transition from traditional hunting to westernized methods of hunting has significantly increased the catch landings in 1993 and 1994 (Table 4).

Table 3. List of sea turtles found in the Torres Strait region (Sources: Spring 1980 and Limpus and Parmenter 1985)

Common names Family Scientific names

Green turtle Cheloniidae Chelodia mydas Flatback turtle " C. depressa Loggerhead turtle " Caretta caretta Hawksbill turtle " Eretmochelys imbricata Olive ridley turtle " Lepidochelys olivacea Leatherback Dermochelyidae Dermochelys coriacea 15 Turtle Fishery- Table 4 summarises the annual catch landings for the Daru fishery. The dominant species caught is the green turtle (C. mydas), followed by Flatback turtle {N. depressus) and Hawkbill turtle (B. imbricata) . The green turtle contributes the highest proportion of the catch by number per annum (~ 98%) (P. Polon per. coram.) . This species is most favoured in the artisanal fishery. Prescott (1985) calculated that this fishery provides a gross return of K 63.68 per day in turtle sales. Most of the turtles are taken from the Warrior Reef complex. Females are favoured over males. Prescott (1985) mentioned further that there is a taste preference for meat and the fishermen select females that are in the breeding stage, carrying large amount of body fat and eggs. Hunting occurs year-round, but fishing effort increases during the mating season, when male and female turtles are joined together. Pairs of turtles are easily hunted at this time, as they are more likely to remain on the surface.

The total turtle catch recorded for the Daru market does not represent the total turtle catch landings (Table 4). A problem is now seen in the turtle market, in that the turtles are now taken directly to the settlements and are butchered there and sold. Sometimes the fishermen take the turtles to the villages, where they are butchered and the meat only is taken to Daru for selling.

Table 4. Annual turtle landings at the Daru market by species and sex

Years Males Female unidentified Total

1991 16 149 7 172 1992 5 109 1 115 1993 11 242 6 259 1994 17 339 5 361 Total 49 839 19 907

Recommendations

* That the sea turtles are particularly difficult to manage on a sustained yield basis because their biology is poorly understood (Limus and Parmenter 1985) and that they are migratory species. The apparent harvest of large proportion of the females during the seasonal migration to the

^OL I / 644 16 rookeries in Northern Great Barrier Reef must be addressed urgently for the continual survival of this resource as turtles from the same stock are also harvested on their foraging grounds in Indonesia, Solomon Islands and Vanuatu (Limpus and Parmenter 1985) .

* That the proportion of adult female turtles being harvested be reduced.

* That the total protection of courting females be introduced and that egg harvest be restricted, especially for E. imbricata as this species is in a depleted state throughout its range (Limpus and Parmenter, 1985).

* That the illegal catching of turtles by the lobster and prawn fishermen should be monitored and the fishermen should be made aware of the consequences of their illegal practices.

* Traditional methods should be applied to harvest this resource and that catching of turtles during their breeding migration (i.e during the months of September and December) be prohibited.

* That a permanent full - time biologist and a technician be recruited and their responsibilies should not only include work on turtles but also undertake other research projects. Funding for such projects should be sought from outside sources such as SPREP.

Spanish mackerel (Scomberomorus commerson) Research and Fishery

Spanish mackerel Research

A preliminary survey conducted in 1993 by the Research staff based in Daru indicated a potential for a fishery. The National Fisheries Council in 1994 resolved that a further comprehensive survey would be done before recommending for a fishery to be open. A prosposal for further research has been drafted and main field activity would involve trolling and night handling.

There has not been any comprehensive work done on the species' with regard to it's biology. 17 Spanish mackerel Fishery

P.N.G has no fisery. However, the P-.N.G industry indicated interest in the' catch sharing of this' resource. Research has indicated the viability of the resource within the' P.N.G side of the Torres Strait area. Market factors may have being the main factor on the lack of participation by P.N.G in the fishery for the past years."

References

Anon, (1979). Fisheries research arinual report 1978. Department of Primary Industry, Fisheries Division, Port Moresby, 98p.

Anon, (1980) . Fisheries research annual report 1978. Department of Primary Industry, Fisheries Division, Port Moresby, 103 PP.

Dunstan, D.J. (1961) . Giant perch in Papuan waters, Aust. Fis. New. 20: 15.

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VOL I / 64G 18

ni-ive of information on dugong life history purvey in the perspective o Australian National Parks and and current catch levels. Report Wildlife Service, Queensland. d aonq in tne Torres Strait. In-. e B Marsh, H (1985). f . ^^r I K. Haines, C. G. Willams and Torres Strait Fisheries Semin^ ^^^ Service, Canberra and D. coates "(edB.) • ^tr 53 _ 76_ Fisheries Division, Port

. p (1993) Preliminary estimates of the and Mu X Mobiha, A.M. . " ' „" rcial barramundi (Lates calcarifer) c effort involved m the °™ papua New Guinea. Department fishery in the Western " ' Fisheries Research and Surveys of Fisheries and Marine ^ourceB Branch Technical Paper No. 93 stimates of juvenile barramundi Mobiha, A.M. (1993). ^f^ of western Province, Papua NeW alo g (Lates calcarifer) * < ie8 and Marine Resource, Fisheries Guinea. Department of Fisher &]_ paper No. 93 - 04. Research and Surveys Branch,

1 life history of barramundi Lates Moore, R- '19^) " f^Zua New Guinea. Aust. J. Mar. Freshw. calcarifer (Bloch) m Papua

Res. 33: 647 - 61. (1987) Review of the barramundi Opnai, L.J. ^^f^'inea' ACIAR " Proceedings No. 20. pp. M fishery in Papua^New ^ f "^ for green turtles, Chelonia '210.Prescott, J USHsj . ^ biology: preliminary report. ot mydas in Daru, with * ^J °minar. A. K. Haines, C. G. Williams Fl in: Torrs Strait fieri Fisheries Service, Canberra and andD. ^ates (edS.).Austr ^ _ Fisheries Division, Port R (1973) Barramundi research in Reynolds, L.F. _ and Moore^ ^^ Report ig?1 _ ig72_ pp Papuan waters. Fisherles stock and Fisheries, Port 21 - 28, Department of Agric Moresby. „ M978) The population dynamics of barramundi 1978) Reynolds, L.F. < " } irf papua New Guinea. MSc. Thesis, T = *-P<3 calcarifer \o Universit• a^vy oOfE Papuea.^a New Guinea. R (1982) • Migration patterns of Reynolds, L.F. and Moo«^ (Blooh) in Papua New Guinea. Aust. barramundi Lates cai. j. Mar. Freshw. Res. 33.

, „oM Turtles men and magic. Department of Spring, C.S. ^^t±aai Wildlife Division, P. 0. Box 2583, Environment ana ^"ilD Konedobu. Figure 1. First approximation of barramundi optimum yield, Daru

5 1.5x10 1 • . i 2 1 y = -0.00202X +30.9X +465,R:5386, maxdev:1.96E4

1982 5 2 1.0x10 . A/-"" /A 1984 sz o oCO 75 5 1980/j983 Estimated M.S.Y = | 0.5x10 A /A 120 metric < A 1981 /A / 1985

/

2000 4000 6000 8000

Fishing effort (100 m net days) Figure 2. Regression analysis on the barramundi landings for the years 1971 to 1994

400 y = -15.2x +3.04E4, R:66.2, maxdev:157 r = - 0.864 'OL I / 650