116 



Abstract — Goldband snapper {Pristi- 

 pomoides multidens) coWccted (Tom com- 

 mercial trap and line fishermen off the 

 Kimberley coast of northwestern Aust- 

 raHa were aged by examination of sec- 

 tioned otoliths ( sagittae I. A total of 3833 

 P. multidens, 80-701 mm fork length 

 (98-805 mm total length), were exam- 

 ined from commercial catches from 1995 

 to 1999. The oldest fish was estimated 

 to be age 30+ years. Validation of age 

 estimates was achieved with marginal 

 increment analysis. The opaque and 

 translucent zones were each formed 

 once per year and are considered va- 

 lid annual growth increments (the 

 translucent zone was formed once per 

 year between January and May). A 

 strong link between water tempera- 

 ture and translucent zone formation 

 was evident in P. multidens. The von 

 Bertalanffy growth function was used 

 to describe growth from length-at-age 

 data derived from sectioned otoliths. 

 No significant differences in length- 

 at-age were found between sexes and 

 growth parameters were L^, = 598 mm, 

 K = 0.187/yr, t„ = -0.173 (r2=0.76). Re- 

 gression models of estimated age as a 

 function of otolith and fish measure- 

 ments indicated a significant relation- 

 ship between estimated age and otolith 

 weight (r^=0.94). Total instantaneous 

 mortality (Z) estimates generated from 

 catch-at-age data off! multidens from 

 the northern demersal scalefish fishery 

 INDSF) were 0.65 for 1995-96, 0.87 for 

 1996-97, and 0.71 for 1997-98. Esti- 

 mates of the annual instantaneous rate 

 of natural mortality (M) were 0.10-0. 14. 

 The NDSF population of P. multidens 

 is considered to be exploited above opti- 

 mum levels on the basis of these mortal- 

 ity estimates. The protracted longevity, 

 moderately slow growth and low natural 

 mortality rates of P. multidens predis- 

 poses this species as one vulnerable to 

 overfishing, thus cautious management 

 strategies will be required. Furthermore, 

 capture of P. multidens from depths of 60 

 meters or greater results in a high mor- 

 tality of fish because the physoclistous 

 ruptures causing internal hemorrhaging 

 and hence there is a low probability of 

 survival of any fish returned to the sea. 

 Thus traditional harvest strategies in- 

 volving size limits will bo inappropriate 

 for these fish. Conversely, hai"vest strate- 

 gies that include appropriately targeted 

 spatial fishery closures may provide a 

 useful additional means of preserving 

 the spawning stock biomass of these fish 

 and protect against recruitment over- 

 fishing. 



Manuscript accepted 21 August 2002. 

 F'ish. Bull: 116-128 12003). 



Age validation, growth, mortality, and additional 

 population parameters of the goldband snapper 

 iPristipomoides multidens) off the Kimberley coast 

 of northwestern Australia 



Stephen J. Newman 

 lain J. Dunk 



Western Australian Marine Researcti Laboratories 



Department ol Fishenes 



Government of Western Australia 



P.O Box 20 



North Beach, Western Australia 6920, Australia 



E-mail address (for S J Newman) snewmanm'fish wagovau 



The goldband snapper iPristipomoides 

 multidens. Day), known also as gold- 

 banded jobfish. Day's jobfish and large- 

 scaled jobfish, is widely distributed 

 throughout the tropical Indo-Pacific 

 Ocean region from Samoa in the Central 

 Pacific to the Red Sea in the Western 

 Indian Ocean and from southern Japan 

 south to Australia (Allen, 1985). Along 

 Western Australia, P multidens is found 

 as far south as Cape Pasley (34°S) and 

 is landed in commercial quantities from 

 the Ningaloo Reef area (23°30'S) north- 

 wards (Kailola et al., 1993; Newman, 

 unpubl. data). They inhabit hard bot- 

 tom areas and areas of vertical relief 

 and large epibenthos from depths of 60 

 to at least 245 m and are concentrated 

 in depths from 80 to 150 m (Allen, 1985; 

 Newman and Williams, 1996). 



Pristipomoides multidens is a com- 

 mercially important species throughout 

 much of its range, forming an important 

 part of the landed catch in both arti- 

 sanal and developed fisheries (Dalzell 

 and Preston, 1992; Newman, 2001). In 

 Western Australia this highly valued 

 resource is marketed whole, usually 

 fresh on ice, and transported by road 

 from regional ports to markets in most 

 state capital cities. It is occasionally ex- 

 ported. In the Kimberley region, within 

 the northern demersal scalefish fishery 

 (NDSF), P. multidens has composed on 

 average 37.7% of the landed catch from 

 1995 to 1999 (contributing on average 

 255 metric tons (t)/year). In terms of val- 

 ue to fishermen, it is second only to the 

 red emperor snapper (Lutjanus sehcw). 



Information on the biology of P. mul- 

 tidens is limited. The juvenile habitats 



of P. multidens have not been identi- 

 fied, although Newman (unpubl. data) 

 obtained juveniles from uniform sedi- 

 mentary habitat with no relief. In pre- 

 vious studies, several age determina- 

 tion techniques were used to determine 

 the age of P multidens but there were 

 limited attempts at age validation (Ed- 

 wards, 1985; Mohsin and Ambak, 1996; 

 Richards'). The accurate determina- 

 tion of fish age is the key to estimat- 

 ing growth rates and mortality. Errors 

 in determining fish age can result in 

 ambiguous demographic parameters 

 and provide misleading impressions of 

 the production potential of fish stocks 

 (Newman et al., 2000a). There is a lack 

 of reliable information on the longevity, 

 growth parameters, mortality rates, 

 and population characteristics of P. 

 multidens, despite its ecological and 

 commercial importance. 



This work represents the first com- 

 prehensive study of age, growth, and 

 mortality of a population of P. mul- 

 tidens based on age estimates from 

 sectioned otoliths and contributes to 

 the management of these stocks. The 

 objectives of this study were to validate 

 aging and to provide age, growth, mor- 

 tality and population characteristics of 

 P. multidens from the Kimberley region 

 of Western Australia that are based on 

 age estimates from sectioned otoliths. 



• Richards, A. H. 1987. Aspects of the bi- 

 ology of some deep water bottomfish in Pa- 

 pua New (Guinea with special reference to 

 Pristipomoides multidens (Day). Report 

 87-01, 31 p. Fisheries Research and Sur- 

 veys Branch, Department of Primary In- 

 dustry, Port Moresby, Papua New Guinea. 



