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Fishery Bulletin 92(3), 1994 



tribution patterns are to a large extent still unknown 

 in deep-water species of the latter genera. 



Moreover, recently published data on the distri- 

 bution and abundance of deep-water shrimps in the 

 western Mediterranean (Aristeus antennatus , Acan- 

 thephyra eximia, Nematocarcinus exilis) indicate 

 relatively high biomass levels for these species at 

 depths down to 2,200 m ( Abello and Valladares, 1988; 

 Cartes and Sarda, 1992, 1993; Sarda and Cartes, 

 1993a). Fishing pressure in shallow waters has re- 

 sulted in a shift of effort to deeper regions, making 

 the study of deepwater species extremely important, 

 while exploitation of these resources is still low (King, 

 1981; Demestre, 1990; Demestre and Lleonart, 1993). 

 Growth, reproductive biology and morphometry of 

 Aristeus antennatus in particular has been studied 

 by several authors (e.g. Bas, 1965; Relini Orsi and 

 Relini, 1979; Arrobas and Ribeiro-Cascalho, 1987; 

 Sarda and Demestre, 1987; Demestre and Fortuno, 

 1992; Sarda et al., in press). In contrast, the only 

 available information on population structure (sex- 

 ratio, size distribution, proportion of juveniles) and 

 spatio-temporal migrations has been compiled from 

 commercial fisheries data (Relini and Orsi Relini, 

 1987; Tobar and Sarda, 1987, 1992). 



The objective of the present study is to examine 

 the relationship between fisheries exploitation and 

 the distribution and spatio-temporal structure of a 

 population of A. antennatus in the three different 

 habitats occupied by this species: submarine canyons 

 on the upper slope, the middle slope, and lower slope. 

 The study attempts to integrate our basic knowledge 

 of the biology and population structure of this spe- 

 cies with the pattern of fishing activity in the region. 

 We provide a basis for interpreting catch fluctuations 

 observed during the year and for managing this fish- 

 ery consistent with the general ecology of the species. 



Materials and methods 



Sampling was designed to survey spatio-temporal 

 features in two different habitats (one station in each) 

 where commercial catches of A. antennatus were com- 

 mon: the submarine canyon known as "La Meren- 

 guera" located on the upper slope (US) at a depth of 

 approximately 450 m (41°07'75"N, 02°04'43"E) and 

 the area known as the "Abisinia" fishing grounds on 

 the middle slope (MS) at a depth of 600-650 m 

 (41 06'34"N, 02°12'05"E). A third station was located 

 on the upper portion of the lower slope ( LS ) at a depth 

 of about 1,200 m (41°54'63"N, 0206'90"E), where no 

 fishing activity takes place (Fig. 1). Habitat nomen- 

 clature follows Peres (1985). Three replicate tows 

 were carried out within a period of less than 12 hours 



at each sampling station in summer, autumn, win- 

 ter, and spring (Table 1). The trawl gear was a 

 "Maireta system" (Spanish patent: 9200614, Inst. 

 Ciencias del Mar [CSICJ, consisting of a semi-bal- 

 loon otter trawl with square panels and wings and a 

 25-m headline. The gear was towed by a single warp 

 line attached to a V-shaped backstrop, which was in 

 turn connected to two 450-kg iron doors. The hori- 

 zontal gear opening (the wing-end spread of 14 m) 

 was measured by using a SCANMAR system. Codend 

 stretch mesh size was 2 mm (Sarda et al., 1993). 

 Trawls were conducted by the Research Ship Garcia 

 del Cid. 



Towing speed was 2.5 knots for all trawls. Start- 

 ing and ending positions of each tow were recorded 

 by using a GPS system. Specimens of A. antennatus 

 were weighed and sexed (M=males; F=females), and 

 short carapace length (CL) in mm was measured 

 (rear edge of ocular orbit to rear edge of carapace). 

 Male and female individuals smaller than 23 mm CL 

 were classified as juveniles (J) (Sarda and Demestre, 

 1987; Demestre, 1990). Smaller individuals 

 (CL <15 mm) were uncommon in the samples; such 



Figure 1 



Map of the study area showing the location of sam- 

 pling stations. US=upper slope; MS=middle slope; 

 LS=lower slope (see text for explanation). 



