SOUTH PACIFIC COMMISSION DEEP REEF SLOPE FISHERY RESOURCES OF THE SOUTH PACIFIC A summary and analysis of the dropline fishing survey data generated by the activities of the SPC Fisheries Programme between 1974 and 1988 by P.Dalzell and G.L. Preston Inshore Fisheries Research Project Technical Document No. 2 Printed with the financial assistance of the Government of the United Kingdom South Pacific Commission Noumea, New Caledonia 1992 465/92 it ©Copyright South Pacific Commission, 1992 The South Pacific Commission authorises the reproduction of this material, whole or in part, in any form, provided appropriate acknowledgement is given. Original text: English South Pacific Commission Cataloguing-in-publication data Dalzell, P. Deep reef slope fishery resources of the South Pacific: a summary and analysis of the dropline fishing survey data generated by the activities of the SPC Fisheries Programme between 1974 and 1988 / by P. Dalzell and G.L. Preston (Technical document / South Pacific Commission. Inshore Fisheries Research Project, no. 2) 1. Fishery resources - Oceania 2. Fisheries - Catch effort 3. Fishing surveys - Oceania I. Title II, Series III. Preston, G.L. 639.2 AACR2 ISBN 1018-3116 Prepared for publication and printed at South Pacific Commission headquarters, Noumea, New Caledonia, 1992 HI ABSTRACT An analysis is presented of data collected by survey fishing of deep reef fish stocks in the South Pacific between 1974 and 1988. The dominant species in the catch were the snappers (Lutjanidae) of which about 70 per cent were from two sub-families, Etelinae and Apsilinae. Other important catch components were the groupers (Serranidae) and the emperors (Lethrinidae). Catch composition was markedly different between low-lying atolls and high islands. Atoll catches contained proportionately less eteline and apsiline snapper species than high island catches. There were no significant differences between total catch and catch rates of teleosts around atolls and high islands. Catch rates around atolls, however, were far more variable than high island catch rates. Catch rates of eteline and apsiline species, emperors and barracudas (Sphyraenidae) appeared to increase with increasing island land mass, while those of jacks and tunas (Carangidae and Scombridae) and oilfish and snake-mackerels (Gempylidae) suggested an opposite trend. Mean catch rates by weight increased with sea depfli to about 250 m but declined markedly below that depth. Catch rates by numbers versus depth increased sharply in the first 100 m, then declined steadily for each 50 m depth interval below 100 m. Peak catch rates by numbers in shallow water occurred at midday and midnight. In terms of weight, catch rates increased after midday and were more or less constant until midnight, when they declined. Catch rates by weight and numbers for fishing in waters more than 50 m in depth showed a distinct peak during the early morning. Two other peaks in catch rate gradually became evident at or around midday and in late evening for fishing at depths greater than 200 m. The overall pattern of catch rate versus time of day for both weight and numbers, for all depths combined, showed three distinct peaks in the early morning (0300 hrs), midday (1200 to 1400 hrs) and late evening (2100 to 2200 hrs). Over 200 species offish, belonging to 93 genera, were caught by the SPC masterfishermen by dropline fishing throughout the South Pacific. There was a distinct decline in the number of species captured by dropline fishing at each location from the western limit of fishing around the islands of Belau to the eastern limit of French Polynesia. This decline in species number is consistent with biogeographic trends in other fishes and invertebrate groups within the region. Attempts were made to estimate possible catch rates at the optimum level of fishing effort, since the survey results presented here pertain mainly to virgin stocks. The standing stock biomass of deep slope fishes at several different locations was determined from two depletion models. The results were then used to estimate empirically the biomass of deep slope fishes for every nation in the South Pacific region. These estimates were then used in conjunction with catch data from survey fishing to produce a summarised profile of the resource potential for each country and territory in the region. ACKNOWLEDGEMENTS The authors are indebted to the work of the SPC masterfishermen and others associated with the Soulh Pacific Commission's Outer Reef Artisanal Fisheries Development Project and the Deep Sea Fisheries Development Project during the period 1974-1988. These individuals (Paul Mead, Lindsay Anderson, Pale Taumaia, Tevita Fusimalohi, Archie Moana and Paxton Wellington) were responsible for the collection and reporting of the fishing data on which this document is based. We are also grateful to our colleagues and friends who assisted in the data analysis and preparation of the document. Tim Lawson wrote and continually modified the database and associated reporting procedures which were used to carry out most of the initial data analysis. Helene Ixeko and Natalie Baillon carried out the laborious task of data entry. Tony Lewis, Peter Cusack, Mike McCoy, David Itano, Paul Mead and Lindsay Chapman commented on the draft manuscript and suggested modifications. Caroline Nalo and Roslyn Sharp patiently edited and proofread the text. Jean-Pierre Le Bars assisted with the figures and Kay Legras assisted with the final layout of maps and tables. This document was prepared with the generous financial support of the Government of the United Kingdom. iv RESUME L'auteur prdsente une analyse des donnees recueillies entre 1974 et 1988 dans le cadre d'une campagne devaluation des stocks de poissons de r£cif qui vivent en profondeur, dans le Pacifique Sud. Panni les poissons captures, les vivaneaux (Lutjanidae) dominaient et 70 pour cent d'entre eux appartenaient a deux sous-families : Etelinae et Apsilinae. Panni les autres especes capturees en quantitds importantes, il y a lieu de citer les me*ous (Serranidae) et les bees de cane (Lethrinidae). La composition des prises 6tait tres sensiblement difKrente selon qu'elles avaient &6 nSalis^es pres d'atolls au relief bas ou d'fles montagneuses. Paraii les prises effectuies pres des atolls, les especes de vivaneaux appartenant aux sous-families Etelinae et Apsilinae dtaient proportionnellement moins nombreuses que celles effectudes pits d'fles montagneuses. D. n'y a pas de difference marquee entre les taux de prises totales et les taux de prises de tel£ost6ens nMis£es dans les eaux qui baignent les atolls et les ties aux sommets elevds. Toutefois, les premiers varient beaucoup moins que les seconds. S'agissant des blinds et des apsilin^s, des mgrous et des barracudas (Sphyraenidae), il semble que les taux augmentent en proportion de l'importance de la masse de Tile, alors que pour ce qui est des carangues et des thonid^s (Carangidae et Seombridae), ainsi que des poissons-huile et des maquereaux serpents (Gempylidae), la tendance semble opposee. Les taux de prises moyens en fonction du poids augmentent avec la profondeur jusqu'a 250 metres, mais baissent nettement au-dessous de cette profondeur. Les taux exprimds en nombre en fonction de la profondeur augmentent en Heche dans les premiers 100 metres, pour diminuer de fa§on constante pour chaque intervalle de 50 metres au-dessous de ce niveau. Les taux de prises maxima exprim£s en nombre, en eaux peu profondes, sont enregistre's a midi et a minuit. Quant au poids, les taux font apparaitre une augmentation apres midi pour se stabiliser plus ou moins jusqu'a minuit et diminuer par la suite. C'est au petit matin que se situe la p6riode de pointe pour la pe'che rgalisde a des profondeurs d6passant les 50 metres tant pour le poids que pour le nombre d'individus. Deux autres p6riodes de cr6te deviennent progressivement £videntes aux environs de midi et en fin de soiree, pour la pe"che r£alise*e a des profondeurs ddpassant les 200 metres. Le profil gdn&al des taux de prises exprimis en poids et en nombre d'individus en fonction de l'heure, toutes profondeurs confondues, fait apparaitre trois p£riodes de pointe, au petit matin (3 heures), a midi (12 a 14 heures) et en fin de soirde (21 a 22 heures). Les mattres-pScheurs de la CPS ont pSche" a la ligne dormante plus de 200 especes appartenant a 93 genres differents dans le Pacifique Sud. On enregistre une baisse nette du nombre d'especes captur&s a la ligne dormante sur tous les lieux de pSche, a mesure qu'on se deplace de la limite occidental des operations de pSche r6alis6es autour des lies de Belau a la limite orientale de la Polyn6sie franchise. Cette diminution graduelle du nombre d'especes est conforme aux tendances biog^ographiques observers chez les autres poissons et invertebrds matins de la region. Des tentatives sont faites pour estimer les taux de prises que Ton pourrait atteindre au niveau optimal de reffbft de p6che, puisque les rfisultats de l'enquete presentee ici concement essentieUement les stocks vierges. La biomasse des stocks permanents de poissons vivant en eaux profondes pres du tombant du rdcif a €ti determined a plusieurs endroits diffiSrents grSce a deux modeles d'dpuisement. Les rdsultats ont ensuite 6t6 utilises pour estimer de fa§on empirique la biomasse des poissons vivant en eaux profondes pres du tombant du r6cif de chaque pays oc^anien. lis ont finalement £x& utilises en parallele avec les donnfies relatives aux captures obtenues lors de la campagne devaluation