The Portuguese crustacean trawl fleet operates mainly off the Southwest and South coasts of Portugal, from 200 to 500 meters deep. This fishery started in 1983 with 35 vessels but since 1996 only 25 trawlers are still operating. These vessels range from 20 to 35 meters in size and 350 to 700 HP. A few of these vessels are freezer trawlers. A 55 mm mesh size has been used in this fishery. The crustacean species are also captured as by-catch of the bottom trawl fishery targeting fish, such as hake, horse mackerel, anglerfish and others (Anon., 1999).

Catch rates
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The Portuguese crustacean fishery has two main target species, the Norway lobster (Nephrops norvegicus) and the pink shrimp (Parapenaeus longirostris), hereafter designated only by Nephrops and Parapenaeus, respectively. These two species have an overlapping distribution. However, Nephrops is more abundant in deeper waters than Parapenaeus, as shown by Figueiredo (1989). Therefore, each fishing haul must be directed to one of these two species. The red shrimp, (Aristeus antennatus) is the third most important species caught by this fishery. Nephrops is the most valuable of the three species.

Nephrops norvegicus
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Reviews of the crustacean fishery, biology of Nephrops and the two other species (Parapenaeus and A. antennatus) were presented by Caramelo (1988) and Cascalho (1988), respectively. Cadima et al. (1995) presented a bio-economic study on this fishery. Recent relevant works on this fishery were also presented by Figueiredo (1989) and Figueiredo & Viriato (1989).

Parapenaeus longirostris
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Only Nephrops is under TAC regulation and has a minimum landing size of 20 mm carapace length. Nephrops stock assessment is conducted by the Nephrops Working Group (Anon., 1997), which meets under the auspices of the International Council for the Exploration of the Sea (ICES). In Portugal the two most important Nephrops stocks are distributed off the Southwest (Alentejo stock, ICES Functional Unit 28) and South coasts (Algarve stock, ICES Functional Unit 29).

The methods used by the Nephrops Working Group (NWG) to assess the current state of the stock, and to provide management options to ACFM (the Advisory Committee on Fishery Management), are analytical methods such as Virtual Population Analysis (VPA). These methods are based on pseudo-age data, and length cohort analysis (LCA), which rely heavily on fishery data (length compositions of the stock) (see e.g. Anon., 1997). However, these methods have been shown to be unreliable for some Nephrops stocks, particularly where there is a marked spatial heterogeneity in Nephrops growth Anon., 1995. The variability in Nephrops growth is strongly related to the heterogeneity on seabed sediments (Afonso-Dias, 1998). However, there are other hydrographic factors that affect the distribution and biology of Nephrops (Bailey et al., 1995).

Aristeus antennatus
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In Portugal, the crustacean fleet operates on the two stocks and the fishery statistics on landings and effort are given for the whole area (Alentejo and Algarve). Furthermore, fishing effort directed to Nephrops has been difficult to estimate. At the present, each vessel landing Nephrops is considered as being fishing for Nephrops. As a result of this the NWG has been assessing the two Portuguese Southern stocks (Functional Units, FU 28&29) as a whole stock (see e.g., Anon., 1997). A recent assessment of this stock showed that stock biomass and recruitment continue at a very low level, the fishing pressure is very high, affecting more intensively the male component of the stock (Anon., 1999). Independent surveys carried out by IPIMAR shows a continuous decline in Nephrops abundance since 1992 (Anon., 1999).

Landings of the three species since 1988
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As a consequence of Nephrops decline and due to the high abundance of Parapenaeus, in the past ten years there has been a shift of target species to Parapenaeus. During this period, and despite the state of overexploitation of the Algarve stock of Parapenaeus (Mattos-Silva, 1995), the landings did not decrease due to good recruitments. These changes are illustrated by the specific composition of the crustacean fleet landings (source of data: DGPA). Between 1983 and 1989, 47% (around 720 tonnes/year) of the total landings of the three main crustacean species were Nephrops. The Parapenaeus landings (620 tonnes/year) accounted for 40% of the total crustacean landings, whereas Aristeus landings (200 tonnes/year) only contributed with 13%. In 1993, 60 % of the crustacean landings were Nephrops (185 tonnes) and 30% were Parapenaeus (94 tonnes). In 1999, Parapenaeus landings represented 83% (1695 tonnes) of the total of the three main crustacean species landed, while Nephrops landings only contributed with 7 % (150 tonnes). A remarkable increase in Parapenaeus landings has occurred in the past five years, in particular in the last year where landings almost tripled.