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Fishery Bulletin 101(2) 



▼. 



Equator 



Seychelles Bank 



D 



Saya De Maiha Bank 



SW Indian Ocean 



Figure 1 



The position of Saya de Malha Bank in the SW Indian Ocean and the location of 

 the hook-and-line fishing ground for demersal fishes (see small rectangular box 

 in map and enlarged inset). 



fishing operations may be limited because of confounding 

 effects from changes in target species, fishing depth, and 

 other factors that would normally be controlled within the 

 experimental design of a research cruise. Despite these 

 constraints, valuable management information may be 

 obtained from commercial fisheries data at a much lower 

 cost in cases where these factors have remained constant 

 or have not influenced catch rates of the target species (e.g. 

 Mees, 1996a). 



An intensive line fishing operation, consisting of a re- 

 frigerated cargo mothership and 12 catcher boats (dories), 

 targeted P. ftlamentosus on the dropoff at Saya de Malha 

 Bank in the southwest Indian Ocean during March 1993. 

 The operation had previously fished at locations in the Sey- 

 chelles archipelago and had been shown to rapidly deplete 

 reef fisheries resources (MeesM. 



The mode of operation was characteristic of a "hit and 

 run" fishery, where fishing would be conducted at a location 

 until catch rates dropped to a level where it was not longer 

 viable to continue. Daily catch and effort data are used in 

 the present study to determine the effect of intensive line 

 fishing on the initial virgin biomass of P. filamentosus at 

 Saya de Malha Bank in the southwest Indian Ocean. 



Mees, C. C. 1992. Pechcur litvlon: an analy.sis of data relating 

 to a mothership dory fishing operation in Seychelles waters from 

 March 1991^Iune 1992. Seychelles Fishing Authority Technical 

 Report (SFA/R&I)/023), 38 p. Seychelles Fishing Authority, Gov- 

 ernment of Seychelles, P.O. Box 449, Victoria, Mahe, Seychelles. 



Materials and methods 



Study area 



Saya de Malha Bank is located on the Mascarene Plateau 

 in the southwest Indian Ocean (Fig. 1 ). The bank consists of 

 three plateau areas, the periphery of which ranges in depth 

 from 15 to 200 m. The specific study area was 60.2 km of 

 the dropoff in the 55-130 m depth range between latitude 

 9°53'S, longitude 59°45'E and latitude 94°3'S, longitude 

 59°50'E. The area corresponds to the grounds fished by the 

 mothership-dory fishing operation over a 13-day period. 



The region has a tropical humid climate modified by the 

 NW monsoon from December to March and the SE trade 

 winds from May until October Intermonsoon periods of 

 light, variable winds and frequent calms occur during April 

 and November when equatorial troughs affect the region 

 (Walsh, 1984). 



Data collection 



During March 1993, 12 fiber glass dories equipped with 

 echo sounders and electric fishing reels were deployed at 

 Saya de Malha Bank from an 88-m refrigerated cargo ship. 

 Fishing was conducted during the day and catches were 

 landed to the mothership each evening. A daily log of the 

 activities of individual catcher boats per fishing trip was 

 maintained, which included the total weight by species, 

 fishing tri[) duration, fishing method, bait type, depth range 

 fished, number of men, and the number of lines used. In 



