AN UPDATE OF BY-CATCH ISSUES IN THE WESTERN AND CENTRAL PACIFIC

Peter G.~illiams'

ABSTRACT This paper reviews by-catch issues in western and central Pacifc tuna fuheries. By-catches fLom tuna fisheries in these sea areas include , billfih, carangidr, ; and more rarely, marine mammals, turtles, and sea fowl. The author stresses the importance of appropriate and timely data so that managers, researchers and fishers can make suitable analysis and responsible management decisions regarding non- target stocks. Indeed, ongoing and representative by-catch monitoring is put forward as the key to the management and conservation of non-target . To avoid over- or under reporting of by-catches, observer data collection 13 singled out as the most reliable means of monitoring non- target catches. An example of the positive application of such monitoring is the usefil data provided on cornercially valuable species, e.g., wahoo.

1. INTRODUCTION

1.1 Definition of 'by-catch'

The term by-catch has been used to describe non-target species catch in the western and central Pacific Ocean (WPO) tuna fisheries:

"Any catch of species @sh, sharks, marine mammals, turtles, seabirds, etc.) other than the target species. 'Incidental catch' can be regarded as s-ynonymous...... " (Bailey et al. 1996)

By-catch has two components, the non-target species catch that is retained and the non-target species catch that is discarded. By definition, by-catch is pre- determined, while the decision to retain or discard may occur during the catching process, at some time later during the vessel trip, or, at times, on return to port. There are also instances of target species discards in the WPO tuna fisheries. This subject has more relevance to the work on the status of target tuna stocks, and hence is not addressed by this paper.

1.2 Why monitor by-catch ?

During recent years, global attention has focussed on problems relating to the environment and development, with an important component being conservation and management issues in fisheries, for example by-catch. Such matters have been discussed and dealt with through a series of interpational meetings and initiatives, for

Oceanic Fisheries Programme, South Pacific Commission, B.P. D5 Noumea, New Caledonia. example the 1992 United Nations Conference on the Environment and Development (UNCED), and more recently, the request to the Food and Agricultural Organization of the United Nations (FAO) to develop an International Code of Conduct for Responsible Fishing.

Of relevance to the' WPO tuna fisheries is the Agreement for the Implementation of the Provisions of the United Nations Convention on the Law of the Sea of 10 December 1982 Relating to the Conservation and Management of Straddling Stocks and Highly Migratory , which was adopted by the Sixth United Nations Conference on Straddling Fish Stocks and Highly Migratory Fish Stocks on the 4~ August 1995. This agreement sets out significant responsibilities for coastal and flag states, with the assistance of sub-regional and regional organizations or arrangements, in assuring the conservation and management of straddling fish stocks and highly migratory fish stocks. It is also recognition that conservation and management involves all components of the ecosystem, not just target species.

Of importance to the subject of by-catch monitoring, is ANNEX 1 of this agreement dealing with the standard requirements for the collection and sharing of data. Article 1 (General principles) of ANNEX 1 states that:

1 .'% timely co:oflection,comptlation and analysis of data are firtvlomenml to( t?&cfhw c&e~vatiort and kgetnent of srr&ing &h stocks and highly migwry fish stpckr...... Dam collected show% also include i&m'on on no~t&wgetand mso~icrtsdand dsp81~i4rttspecks...... 'Assistme (to dtiveloping stotes) showld fmm on enhancing capacity to implement &a coJlecti6n and ver@cation, ~bserv~rpmgnamm%s,...... '

Article 3 (Basic data) of ANNEX 1 includes specific requirements for by-catch data collection by flag and coastal states: 'Sktres shdl colktf ...... dakjl in su$Wmt derail to facilitate @dwsmk nssesmnr in acco?'dunce with agreed pmhes:

(b) micatch in lljunber, ll~mimrlweigkt or both, by spec& fbcrth8~et and nsn.kYg8t)......

Article 6 (Data verification) provides the means for by-catch monitoring :

......

(b)scient~cCob8ewerpl.og~~s to monitor catch, em,catch composirion (target and nsndiwget)..,' The data collection requirements of this agreement clearly infer some obligation to monitor by-catch. This paper attempts to show how the by-catch monitoring requirements of this agreement are being addressed in the WPO tuna fisheries arid further provides insights into what is currently known from information already collected, and where future direction should be focussed.

2. OVERVIEW OF THE WESTERN AND CENTRAL PACIFIC OCEAN TUNA FISHERIES

The western and central Pacific Ocean currently supports the largest industrial tuna fishery in the world, with an estimated catch in 1995 of 948 863 t in the SPC statistical area alone (Figure 1; Lawson 1996). Skipjack is the most important of the four (target) tuna species in the fishery, accounting for 70 % of the catch by weight in 1995, followed by yellowfin (23%), bigeye (4%) and albacore (3%). Purse seine (80%) and longline (12%) account for most of the catch, with pole-and-line gear accounting for about 8 %. The other gear types utilized in the commercial WPO tuna fisheries, handline and troll, account for less than 1% of the catch.

The purse seine tuna fishery operates almost exclusively in the tropical waters (WTP) of the WO, from approximately 120°E to about 155"W (Figure I). Purse seine vessels set on skipjack and yellowfin schools that have formed 'associations' with floating objects, such as logs and other naturally occuring debris, man-made Fish Aggregation Devices (FADS), and dead whales; tuna schools swimming with live , such as whales and whale sharks, also occur. Sets are also made on tuna schools not associated with floating objects or other animals; these may be unassociated or free-swimming schools that are usually feeding on baitfish or schools associated with geographic features such as seamounts and islands, or with oceanographic features such as current interfaces and areas of upwelling. The breakdown of purse seine sets by school type based on catch logsheet data is: unassociated - 50%; log associated - 34%; FAD associated - 5%; associated - 1%; other and unspecified associations - 10% (Bailey et al. 1996).

The longline tuna fisheries are spread over most of the WPO, and consist of two basic categories of fishing vessel: the larger distant-water vessels that fish far from home ports forperiods typically from 1-3 months, but sometimes longer, and the smaller offshore vessels, which have established base ports in Pacific island countries and undertake trips which are usuaIly 1-2 weeks. The main distinction between these two categories is the method of catch storage: the distant-water vessels supply frozen fish for the normally low-priced markets, while the ofshore fleets supply fresh/chilled fish for the higher-priced sashhi markets. In the tropical waters, bigeye and are the target species; while in the sub-tropical waters, albacore are indluded as target catch.

The WPO tuna fisheries are described in more detail in a number of documents produced by the OFP, for example, Bailey et al. (1996) and Lawson (1996). WSPnl

WTP .

WSP

WTeP \

Fig. 1. The western and central Pacific Ocean (WPO), showing the SPC statistical area, the western and central tropical Pacific (WTP), the western and central sub-tropical Pacific (WSP and WSPn) and the western and central temperate Pacific (WTeP).

2.1 By-catch monitoring in the WPO tuna fisheries - a historical perspective

Past experiences, such as the now defunct albacore drift-net fishery which operated in the temperate waters of the South Pacific during the late 1980dearly 1990s (Bailey eh al. 1996), have focused attention on the effect that fishing methods in the region have, not only on the target species stock, but on the incidental capture of non- target species. As a consequence of concern expressed on the lack of knowledge of the exploitation of non-target species in the WPO tuna fisheries, the Oceanic Fisheries Programme (OFP) of the South Pacific Commission (SPC) was tasked to conduct a review of by-catch based on data holdings and literature (SPC 1991); the results of this study were peer reviewed at successive annual meetings of the OFF (Standing Committee on Tuna and held in 1993, 1994 and 1995), and the report has only now been made available for publication (Bailey et al. 19%).

The general conclusions of the OFP review of by-catch indicated that not enough information was available to accurately determine the levels of by-catch in the western and central Pacific tuna fisheries. The review further suggested mechanisms for improving knowledge on the levels of by-catch through appropriate data collection. With the closure of the driftnet fishery, and the low level of by-catch taken in the pole- and-line, troll and handline fisheries, it was suggested that efforts in data collection should concentrate on the longline and purse seine fisheries, which account for more than 90% of the target tuna catch in the WPO.

While the review noted that there was not enough information available fiom the purse seine fisheries to provide defiqitive estimates of by-catch, several significant conclusions were nonetheless provided:

Although, definitive estimates of by-catch were not possible, observer data suggest that by-catch may constitute between 0.35% and 0.77% of the total catch (by weight) for unassociated sets, and between 3.0% and 7.3% for log sets. Purse seine sets on floating objects (compared with unassociated sets) produce the largest amounts, highest incidence and greatest variety of fish and other species. There is no evidence to suggest that dolphins are deliberately set on or incidentally caught by purse seine vessels in the WTP. Marine turtles are occasionally caught, but there is some evidence that the majority can be released alive. Tuna schools associated with large baleen whales are occasionally set on in the WTP; observer reports indicate that these mammals are easily able to escape alive and unharmed.

Likewise, the review was able to provide several conclusions on by-catch in the longline fisheries, despite a general lack of information:

Observer data indicate that there are significant numbers of taken throughout the WPO longline fisheries, but overall estimates of their exploitation are impossible mainly due to non- and under-reporting on logsheets; Accidental marine mammal capture is a very rare occurrence in the WPO longline fisheries. Sea bird capture by longline vessels operating in the temperate waters bordering the WPO longline fisheries has been well documented and management measures have already been proposed. On the other hand, sea birds are very rarely taken in the sub-tropical and tropical tuna longline fisheries. Marine turtles are taken on occasion, but there is evidence that they are usually released alive.

The review noted predictable and ongoing problems in relying on catch logsheets to provide indications of by-catch levels. However, it also noted that the logsheet reporting for certain non-target species (i.e. the more valuable billfish species) was indicative, and would therefore continue to be referred to. As the level of compliance improves, there will no doubt be some improvements in the provision for by-catch reporting on the logsheet, and possiblyjn the education of the vessel operators in completing this information. However, problems with , for example, will always mean that complete and reliable data will never be realistically available. The review further identified observer data collection as the most reliable means for obtaining indications of by-catch in the WPO longline and purse seine fisheries. Established observer programmes in Australia and New Zealand have been collecting scientific data on longline operations in the more temperate waters of the region for more than 10 years. However, only two compliance-related observer programmes were operational in the tropical waters (WTP) during the 1980s, the observer programme established by Micronesian Maritime Authority (MMA) of the Federated States of (FSM) and the US Multilateral Treaty Observer Programme, established in 1988 and supervised by the Forum Fisheries Agency (FFA). Both programmes have become more involved in scientific data collection during the 1990s.

The establishment in 1995 of a five year EC-funded project operating under the work programme of the OFP, entitled the South Paci$c Regional Tuna Resource Assessment and Monitoring Project (SPRTRAMP) has seen an increase in observer activities throughout the region. With assistance from SPRTRAMP, national observer programmes have been established in Papua New Guinea, Palau and the Solomon Islands in recent years and further national programmes are expected to be set up in the future.

The most significant achievement in by-catch monitoring during the past year has been the introduction of standardized data collection forms for use by regional and national observer programmes (SPC 1996).

2.2 Current indications of by-catch levels

The main problem with attempting to obtain indications of by-catch via observer programmes is the current low coverage of fishing activities. Table 1 shows the estimated 1995 activity for the purse seine and longline fisheries, and the observer coverage for that year (4.3% and 0.3%, respectively). Even a moderate observer coverage of 20% (i.e. approximately 44 000 sea days) would require about 220 full time observers (based on 200 sea days per year per observer). There are currently not enough (human and financial) resources available to attain to this level of monitoring, although it is hoped that, for example, the continued establishment of national programmes, with appropriate training from SPRTRAMP, will help to bridge this gap. It is thought that the possibility of a future regional management arrangement, involving fishing nations and coastal states, would also be beneficial in providing the necessary resources to increase the level of by-catch monitoring.

Purse seine and longline observer data collected during the past 1-2 years provide a useful update to the findings of the OFP review on by-catch, conducted several years earlier. However, it remains impossible to provide definitive estimates of by-catch in the region due to the low coverage of observer activities.

Tables 2 and 3 provides some indication of the occurrence of by-catch species in purse seine and longline sets, respectively. These tables originate from the OFP review of by-catch (Bailey ef al. 1996) and have been derived primarily fkom observer data collection. No changes have been made to the purse seine species list after reviewing recent data, ahd only a few updates have been made to the longline species list. Table 1. Estimated longline and purse seine activity in the western and central Pacific Ocean during 1995.

~ted,E~RIJDB~~~ Numbrot Yumber d Number of Numberd Observer Coverage

Korea (distant-water) Marshall Islands New Caledonia Papua New Guinea Solomon Islands

Taiwan (distant-water)

Western Samoa

otes

I. Derived from Lawson (1996), logsbeet and observer data provided to the OFF. 2. This table dois not include logsheet and observer data collected for activities in the waters of Australia and New Zealand.

Tables 4 and 5 show a breakdown of catch by species observed on longline vessels operating in the WTP and western and central sub-tropical Pacific (WSP), respectively, during 1994-1996. Despite the low coverage of observer data collection (Table I), these summaries provide some initial insight into the species composition of the catch taken by longline vessels in the region, for example:

Target tuna account for nearly half (46.7%) of the observed catch (by number) in the WTP, and more than half (55.5%) in the,WSP. Skipjack, although rarely recorded on longline catch logsheets, were frequently observed in the catch of longline vessels operating in both the WTP (0.4 per 1,000 hooks) and the WSP (1.2 per 1,000 hooks). Shark species account for the next highest category of observed catch in both the WTP (27.2%) and the WSP (17.9%). The catch rate for shark species is higher in the WSP (14.5 fish per 1000 hooks) than the WTP (5.3 fish per 1000 hooks). Blue shark were, by far, the predominant shark species observed in the WSP catch. In the WTP, blue shark and silky shark were the most common shark species observed.

Blue marlin (3.3%) and swordfish (3.0%) were the predominant billfish species observed in the WTP longline catch. It is significant that most blue marlin (89%) were retained, while nearly half (49%) of the swordfish were discarded for this area. The proportion of retained swordfish to blue marlin is more in line with logsheet reported catch proportions of these species (Bailey et al. 1996). The reason for the apparent high discard is related to the size of the swordfish taken, as about 36% of swordfish sampled (where length measurement was possible) were less than 1OOcm from the caudal fork to the lower jaw. a Wahoo (0.4 per 1000 hooks) and mahi mahi (0.3 per 1000 hooks) were frequently observed in the catch of WTP longline vessels, but were more predominant in the catch of WSP longline vessels (3.0 and 1.0 per 1000 hooks, repectively). Bailey et al. (1996) notes that these species are sometimes commercially important enough to retain and supply local markets. The frequency of discard appears to be higher in the WTP than the WSP, which probably reflects the relative market size for these species in the respective areas.

Figure 2 describes the proportion of by-catch in the overall longline catch according to logsheets and observer records for the WTP and the WSP. According to this broad comparison, it is clear that shark and 'other species' catch is non- and under-reported on logsheets in the WTP, and to a lesser extent, in the WSP. The difference between logsheet and observer reported 'other species' catch in the WSP is not as pronounced as in the WTP, and is probably due to the fact that wahoo and mahi" mahi, for example, have a higher commercial importance and composition in the WSP catch, and are, therefore, usually included in logsheet reporting.

In summary, it is possible to gain further insights into by-catch from recdntly collected observer data, but it remains evident that the current levels of monitoring fall well short of providing the information required for the effective conservatibn and management of the species in question.

2.3 Future direction for by-catch monitoring

The coverage provided by observer programmes in the region is one of the main areas to address in ensuring the adequate monitoring of by-catch in the future. There is currently not enough information available to review individual by-catch species as there is with target tuna species, and as such, it would be difficult to suggest where (if any) management measures are required at this stage. There is some obligation by coastal and flag states, with appropriate assistance from sub-regional or regional fisheries management organisations or arrangements, to address this issue in Table 2. By-catch species from purse-seine sets on different school associations in the WTP (from Bailey et al. 1996).

Sharks and rays Blue shark (Prionuceglauca) Oceanic whitetip (Carcharhinus longimanus) Silky shark (C. falciformt) Tiger shark (Galeocerdo cuvier) Whale shark (Rhincodontypus) Manta ray (Mobulajapanica, Manta spp.) Pelagic stingray (Dasyatissp.) Soom&lds Frigate tuna (Auxis thazara') Kawakawa (Euthynnus &inis) Wahoo (Acanthocybium solandn) BUUL4h Black marlin (Makaira indica) Blue marlin (M.maznra) Broadbill swordfish (Xiphiasgladius) Sailfish (Istiophorusplatyptem) Shortbill spewlish (Tetrapturus angustirostris) Striped marlin (T. audar)

Carangib (Seriolarivoliana) Bar jack (Carangoidesferdau) Bigeye trevally (Caram sexfmiatus) Bigeye scad (Selar crumenophthalmus) Caranx spp. (ignobilis,lugubris. melMlp.vgus1 Golden trevally (Gnarhanodonspeciosus) Greater amberjack (Serioladumeril~] scad (Decaglerus macarellus) Pilotfish (Naucrates ductor) Rainbow runner (Elagafisbipinnulata) Other 5sh Badish (Plarm tetra) Bramid (Brama sp.) Drummer (Kyphosw cinermens) Filefish (Alutenrsmonoceros) Filefish (A. scnptus) Flutemouth (FistulariaSD.) Great bafia~uda(~~hya>na ) Mahimahi (Coryphaem hippurus) Man-o-war fish (Psenes cvanophrvs) Ocean anchovy (Stoleph& pun&$er) Ocean triggerfish (Canthidenis maculatus) Porcupine fi* (Diodonhystrir) Porcupine fish (Qdichthys echinarus) Rudderfish (Cenrrolophusniger) Sergeant major (Abudefdufsmtilis) Sea bream (Rhadosargus sarba) Seahorse (Hippocam&u sp.) Sharksucker (Renwra remora) Therapon perch (Theraponsp.) Tripletail (Loboressurinumensis) Marine reptues Green turtle (Chelonia m.ydas) Hawksbill turtle (Eremtochelysimbricata) Olive ridley turtle (Lepidochelysolivacea) Sea snake (Pelamis platurn) - -

Notes R : rare, <]/set; S : common in small numbers, 1-l01set; M: common in moderate numbers, 10-1001set; L : common in large numbers, > 100lse.t; - : not present. Table 3. Target and by-catch species taken by longline vessels fishing in the WPO (updated from Bailey st al. 1996).

Sharks and rays Black-tip reef shark (Carchurhinrrsmelut~opterrts) Black-tip shark (Carcharhinus limbatus) Blue shark (Prionace gluuca) Bronze whaler (Carcharinus brachyurus) Crocodile shark (Pseudocarcharuis kantoharaij Dogfish (Syrnnodon sp.: Squalidae) Great white shark (Curckarodon carcharias) (Carcharhinus amblyrhynchos) Hammerhead shark (Sphyrinus sp.) Mako shark (Isurus oxyrhinchus) Manta rays (Mobulidae) Oceanic white tip (Carcharinus longimcmusj Porbeagle shark (Lamna mus) School shark (Galeorhinus galeus) Silky shark (Carcharhinusfalclformis) Silvenip shark (Carcharinus albimarginatus) Smooth lanternshark (~n~opteruspusill~tsj Stingray (Dasyuris sp.) Thresher shark (Alopias sp) Tiger shark (Galeocerdo crrvier) Whitstip reef shark (Triaenodon obesus)

(Nonhern) bluefin tuna (Thunnus thynnus) Albacore tuna (Thunnus alalunnaj Bigeye tuna (Thunnus obesus) Butterfly tuna (Gasrerochisma melampus) (G.ymnosarda unicolor) Frigate tuna (Alcxis rhazar4 Kawakawa (Euthynnus aflrrisj Longtail tuna (7'hunnus ronggol) Skipjack tuna (Katsuwonrtspelatnis) Slender tuna ~4llothunnusfallai) Southern bluefin tuna (Thunnus mnuccoyii) Wahoo (Acanthocybium solandri) Yellowtin tuna (Thunnus albacares)

BiI1fb.h Black marlin (Mahira indica) Blue marlin (Makaira mazaral Broadbill swordfish (Xiphias $udius) Sailfish (Istiophorus platyprerus) Shortbill spearfish (Terrapturus angustirostris) Striped marlin (Terrapfurusaudnr)

Other fish Bmacouta (Thysires atuta) Barracuda (A~rioposphyraenubarracuda) Bass, Hapuka (Polyprion sp.) Blue eyes (Pseudomugilidae) Bluenose (Hyperoglyphe anrarctica) Bramids, Ray's bream, ponlfiets (Bramidae) Dealfish (Trachipterus sp.j Flying fish (Exocoetidae) Gemfish (Rexea solaruiti) Globefish, porcupine fish (Diodontidae) Hake (Merluccius australis) Hoki, blue grenad~er(Macruronus novaezelandiae) Kinafish ( SD.~ ~aketfish(~le~isduhs sp.) A A Table 3. (continued)

siprula wlrP ww ltaaiwll Lantern fish (Myctophidae) - - R N Mahimahi (Coryphaena h~ppuncr) C A R Y Moonfish I opah I mambo (Lampris sp.) C A S Y Odsh (Regalecur glesne) - R R N .Oilfish (Ruvetfuspretiosus) C C S N Ragtish (Icichthys australis) - - R N Rainbow runner (Elagatis hipinnulata) R S - Y Remora (Remora sp.) R R R N Rudderiish (Centrolophusniger) - R R N Trevally () R - - N Sea perches, gropers (Semnidae) - S - N . Escolar (Lepidoqb~utn A A S N flavobrunneum) Sunfish (Mola sp.) S S S N Warehou (Senolella brm) - R R Y

Marine reptiles Green turtle (Chelonia mydas) S - - N Hawksbill turtle (Eretmochelys imbricata) S - - N Leatherback (Dermochelys coriacea) - - - N Olive ridley (Lepidochelys olivacea) S - - N Turtles (unidentified) S R R N

Marine mmm& Common dolphin (Dephinus delphis) - R - N False killer whale (Pseudorca crassidens) - ? - N Killer whale (Orcinus orca) - - R N Marine mammal (unidentified) R R - N Pilot whale (Globicephala spp.) - - - N Seal (Pinnipedia) - - S ?

Birds Albatross (Diomedea sp.) - - C N Petrels (Procellaria sp.) - - C N Other seabirds R R S N

Notes: 'Y' - normally retained; 'N'-not retained, i.e. normally discardedlreleased. This does not take into account the differences in discarding practices that may exist between fleets or even vessels of the same fleet. The species retained may be sold commercially, kept for mwconsumption or given away on return to port. For shadc species, the hunks are often discarded after the fins have been removed. Most observations of turtles caught by longline vessels indicate that they were released alive (FSM observer reports). 2. Moonfish (Lampris gunatw) is sometimes referred to as MANDAI, which is the Ja anese Okinawan common name for this species. Oilfish (Ruvetfu pretiosus) is sometimes referred to as BA~MUTSU,which is the Japanese common name for this species (Izumi pen, comm.). 3. There are restrictions on the landing of certain billfish species in some areas of Australian and New Zealand waters. LEGEND A: Usually abundant in the longline catch for this area; at least I per set on average. C: Commonly taken; usually it would be expected that at least I of this species would be taken every 10 sets. R: Rarely taken; there may be only one taken per year for that area or. for some species, only one occurrence ever. S: Seldom caught; taken on few occasions but not considered common or rare in the catch; typically it would be expected.that at lea% 1 of this species would be taken every few months. or may only be taken at certain times of the year for that area (i.e. seasonal), or only in specific parts of that area. T: Usually a target species for fleets in this area; if not the target for all vessels, it is usually abundant in the longline catch; at least I per set on averpge. -: No evidence of longline catch of this species found. Table 4. Breakdown of catch by species observed on longline vessels operating in the western and central tropical Pacific (WTP), 1994-1996(N = 465 sets).

Bigeye Blue shark Sharks (unidentified) Silky shark Pelagic Sting-ray (other rays Blue Marlin Lancetfishes Swordfish Breams I Bramids Thresher sharks Skipjack Wahoo Oceanic white-tip shark Mahi Mahi Snake Mackerel Fish (Unidentified) Escolar Sailfish Marlin (unidentified) Oilfish Silver-tip shark Crocodile shark Black Marlin Striped Marlin Albacore Dogtooth tuna Short-billed Spearfish Marine Turtle Sunfishes Grey reef shark Tuna (unidentified) Mako sharks Opah Hammerhead shark Olive Ridley turtle White-tip reef shark Tiger shark Common Blacktip Shark Green turtle Pelagic Thresher shark Bigeye Thresher shark Black-tip reef shark Unidentified Bird Flying Manta Ray Rainbow Runner Unidentified Trevally

TARGET TUNA SHARK OTHER FISH BILLFISH OTHER SCOMBRIDS TURTLES BIRD Notes: 1. CPUE - number of species per 1,000 hooks. 2. Percentages for FATE, CONDITION and SEX do not include instances where no information was recorded. Table 5. Breakdown of catch by species observed on longline vessels operating in the westernd central sub-tropical Pacific (WSP), 1994 - 1996 (N = 97 sets).

Yellowfin Blue shark Wahoo Snake Mackerel Bigeye Lancetfishes Mahi Mahi Fish (Unidentified) Escolar Skipjack Short-hilled Spearfish Striped Marlin Barracudas Swordfish Opah Tuna (unidentified) Oceanic white-tip shark Sharks (unidentified) Silky shark Black Marlin Blue Marlin Oilfish Short finned Mako shark Sailfish Mako sharks Pelagic Sting-ray (other rays) BreamsIBramids Grey reef shark Tiger shark Hammerhead shark Thresher sharks Pelagic Thresher shark Sunfishes Bigeye Thresher shark Crocodile shark Dealfish Rainbow Runner Un-identified Trevally Manta Ray Marlin (unidentified) Silver-tip shark

TARGET TUNA

OTHER FISH OTHER SCOMBRIDS BILLFISH Notes: 1. CPUE - number of species per 1,000 hooks. 2. Percentages for FATE, CONDITION and SEX do not include instances where no information was recorded. the future. However, the main problem with the implementation and continuation of observer programmes will be the huge amount of human and financial resources required to cover the fishing activities in the region (Table 1).

Given that there will be problems with observer coverage in the future, the following re likely to have priority in the future :

The current sampling protocols used in observer data collection will probably continue to be peer reviewed to ensure the most representative and reliable methods are employed. This may take the shape of a more formal review, taking the lead of a recent, successful review on the Inter-American Tropical Tuna Commission (I-ATTC) purse seine observer programme. In the future, the OFP will continue to exchange relevant information with agencies that deal with tuna and billfish, and related by-catch, research throughout the world;

With the increase in sport fishing activities throughout the region during the past decade, some concern has been expressed over possible interaction with longline fisheries as a result of billfish capture. At this stage, there has been no analytical work of this kind for the tropical waters of the WPO, and careful attention to appropriate data collection will be necessary in order to enable any such analytical work in the future;

Global initiatives reviewing shark by-catch in various fisheries around the world (Le. the Convention on the International Trade in Endangered Species - CITES) will no doubt mean that further information on the exploitation of shark species in WPO tuna fisheries will be required in the future;

By-catch which has some commercial importance will also be reviewed in the future. For example, the OFP is currently involved in supervising a post graduate student with his work on the ecology and biology of wahoo. Most of the data for the age and growth work for this study are collected by observers.

3. CONCLUSIONS

A long time series of data exists for target tuna and some billfish species, but there are no comparable data available for most by-catch species. In order to make responsible management decisions in the future, it will be fundamental to have adequate data available for appropriate analytical work. For this reason, the monitoring of by-catch in the WPO tuna fisheries should be continuous and representative.

Observer data collection has been identified as the most reliable means of monitoring by-catch. The main problem to address is the current low observer coverage. Due to the nature of the work involved, substantial human and financial resources will be required. With the implementation of SPRTRAMP, an excellent basis for regional standardised observer data collection has been established. It remains to be seen, however, whether there-will be sufficient resources to provide the necessary coverage in the future.

The information collected for some of the commercially important by-catch species (e.g. wahoo) is one example of the positive aspects of by-catch monitoring. This will no doubt provide useful insights in the future, which will be of ultimate benefit to researchers, fishermen and managers.

REFERENCES

Bailey, K.N., P.G. Williams and D.G. Itano. 1996. By-catch and discards in the western Pacific tuna fisheries: A review of SPC data holdings and literature. Oceanic Fisheries. ~ro&amhe Technical Report 34. South Pacific Commission, Noumea, New Caledonia.

Lawson, T. 1996. South Pacific Commission 1995 tuna fishery yearbook. Oceanic Fisheries Programme. South Pacific Commission, Noumea New Caledonia.

SPC. 1996. Ad hoc meeting on tuna fisheries data collection forms, Brisbane, Queensland, Australia, 11-14 December, 1995. Report of the Meeting. South Pacific Commission, Noumea, New Caledonia. Forum Fisheries Agency, Honiara, Solomon Islands. Figure 2. Catch breakdown from longline vessels operating in the western and central tropical Pacific Ocean (WTP), as reported on LOGSHEETS (left) and by OBSERVERS (right), 1994-1996.

Figure 3. Catch breakdown from longline vessels operating in the western and central sub- tropical Pacific Ocean (WSP), as reported on LOGSHEETS (left) and by OBSERVERS (right), 1994-1996.