FAO/CECAF WG on the assessment of demersaal resources-North-2013

BIOLOGICAL INFORMATION ON DEEP WATER ROSE SHRIMP PARAPENAEUS LONGIROSTRIS AND SOUTHERN PINK SHRIMP NOTIALIS IN MAURITANIAN WATERS

Eva García-Isarch, Zeneida Romero, Pablo Expósito, Sergio Barro and Ignacio Sobrino Instituto Español de Oceanografía. Centro Oceanográfico de Cádiz. 11006 Cádiz, Spain

FAO/CECAF Working Group on the Assessment of Demersal Resources- North Fuenngirola, Spain, 18 -27 November 2013

1.-INTRODUCTION

The deep-water rose shrimp Parapenaeus longirostris (Lucas, 1846) and the southern pink shrimp Farfantepenaeus notialis (Pérez Farfante, 1967) have traditionally been the target for the shrimper Spanish fleet operating in the Mauritanian fishing ground. In spite of their commercial interest, there is a general lack of knowledge about biological aspects referring to stock identification, growth, reproduction, alimentation, length structure, and natural mortality of these species. However, population and biological information is needed for stock assessment and management measures aiming a proper exploitation pattern and conservation of the exploited species. The first difficulty encountered for assessment refers to the accurate identification of biological stocks, which are currently assessed on a national basis whereas many of them are supposed to be transboundary. The scarcity of available biological information about the species in the area makes that stocks of P. longirostris and F. notialis, evaluated into the framework of the CECAF Working Group of Demersal Resources (North) have to be defined arbitrarily for assessment purposes, within the geographical limits of the countries where they are exploited. Therefore, one stock of P. longirostris and one stock of F. notialis are considered in , without any biological base. This could be an error source in the assessments carried out for these species. This work aims to collect and analyze the available information about different population and biological aspects of P. longirostris and F. notialis, the main target shrimp species in Mauritanian waters. This will contribute to a better knowledge of the biology of the species for assessment and management purposes.

2.-MATERIAL AND METHODS Three main sources of information were used in order to provide biological information on P. longirostris and F. notialis: i) literature; ii) scientific observations onboard Spanish shrimper vessels carried out by the Spanish Institute of Oceanography (IEO) in Mauritanian waters during 2010 and iii) research surveys carried out in Mauritanian waters by the Spanish R/V Vizconde de Eza (2007-2010).

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And exhaustive literature revision was made to compile all the available biological information in the area. The IEO scientific observations onboard Spanish shrimper vessels in Mauritanian waters during 2010 (García-Isarch et al., 2011a, b; 2012a, b) were the main source for new information on the biology and population structure of both species. Four scientific observation fishing trips (one per quarter) were carried on board Spanish shrimper vessels operating in Mauritanian waters in 2010 (“LANGAMAU” fishing trips) (Table I). This information was used to analyse (both spatially and temporally) abundance, distribution, and biological and population parameters of the target species. However, a total annual cycle could not be completed, because of the fishing restrictions during 4 months, due to the two closed seasons: May-June and October-November. In spite of the autumn closed season, information from November could be obtained from a selectivity trial onboard a EU shrimper vessel carried out by the IEO and the Mauritanian Institute for Oceanographic Research and Fisheries (IMROP) during this month “Mauritania 1110” (Sobrino et al., 2011). Data from this experimental survey were used to complete the analysis of biological and population parameters of the target species.

Table I.- Scientific observations fishing trips carried out on Spanish shrimper vessels operating in Mauritanian waters in 2010.

SCIENTIFIC OBSERVATION DATES FISHING DAYS FISHING TRIP

LANGAMAU-0110 22 JanuaryÆ9 March 47

LANGAMAU-0210 14 MarchÆ12 April 30

LANGAMAU-0310 3 JulyÆ4 September 63

15 NovemberÆ20 November* LANGAMAU-0410 24 1 DecemberÆ 18 December

TOTAL-2010 164

*Observation from the selectivity trial “Mauritania 1110”

The sampling methodology used by the onboard observers is explained in detail in García- Isarch et al. (2011a). Results and main conclusions of these observations are reported in García-Isarch et al. (2011b, 2012a). Biological parameters were sampled as follows. For length frequency distributions, cephalotorax lengths (CL) were measured with calibre, separately for males and females. Parameters registered in biological samplings were: sex, length and maturity stage. For maturity, a key of 4 stages was used for females: I: Immature, II: in development, III: maturing, IV: mature. Males were classified as immature (I) or mature (II) (see García-Isarch et al., 2011 for maturation scales). All the length and biological information was analysed in order to study: i) the population structure of target species and its temporal variation; ii) identification of length groups or cohorts through Modal Progression Analysis (MPA)- Bhattacharya method (FiSAT II); iii)

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FAO/CECAF WG on the assessment of demersal resources-North-2013 biological characteristics of the target species (sex-ratio, spawning season and first maturity length, when possible). Finally, part of the spatial distribution of P. longirostris could be explained by the information collected during the research surveys carried out in Mauritanian waters by the Spanish R/V Vizconde de Eza (from 2007 to 2010). These four multidisciplinary cruises of one month’s duration (November-December) were carried out to sample the continental margin (from 80 to 2000 m) (Hernández-González et al., 2010; Ramos et al., 2010). Data from these surveys were analysed to study the spatial distribution and abundance of P. longirostris.

3.- RESULTS AND DISCUSSION

Deep water rose shrimp (Parapenaeus longirostris)

Spatial distribution The deep water rose shrimp, P. longirostris is one of the three species in this genus inhabiting the Atlantic Ocean (Pérez-Farfante and Kensley, 1997). The species shows a wide geographic distribution, from the eastern Atlantic in the north of Spain to the southern waters of , as well as in the Mediterranean and its adjacent seas (Sobrino et al., 2005). It inhabits muddy or muddy-sandy bottoms. The bathymetric range of this species changes with latitude. In four research surveys carried out in Mauritanian waters by the Spanish R/V Vizconde de Eza (from 2007 to 2010), the presence of P. longirostris was detected in a wide depth range, from 84 m to 473 m. The bathymetric distributions of these shrimps are linked to the specimen’s size, in a way that biggest individuals (females) are distributed at deeper waters. Thus, there is segregation by size (sex-related) in relation to depth. After the larval dispersion phase in shallow waters, the shrimps move towards deeper waters throughout their life. Juveniles settle at around 100 m depth, although they can be detected up to 300 m, whereas larger individuals (which correspond to females) are always found at depths over 350 m (Sobrino et al., 2005). Besides these ontogenetic migrations, P. longirostris also performs vertical daily migrations and other migrations related to the moon phases. In fact, maximum daily yields are obtained during full moon periods (Crosnier and Tanter, 1968). The highest densities in terms of biomass have generally been recorded in different regions between 100 and 300 m depth (Sobrino et al., 2005). In the Spanish surveys carried out from 2007 to 2010 onboard the R/V Vizconde de Eza (Figure 1), P. longirostris was more or less evenly distributed south to 20º 30’ N. Main abundance concentrations were located at 20º 10’ N and 19º 40’ N (in front of Tidra Island), both in deep waters of the northern area1, around the Arguin Bank. In the southern area, the distribution is more homogeneous (although with lower abundances) from Cape Timiris to the Senegalese border, and deep-water rose shrimps are found up to the 500 m isobath. It should

1 North and South area have been arbitrarily divided by the latitude 18.5ºN. North: 21ºNÆ 18.5ºN. South: 18.5ºNÆ16ºN

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FAO/CECAF WG on the assessment of demersal resources-North-2013 be noted that these surveys were always carried out in the same season (November- December) and do not reflect any eventual seasonal variation of the species’ distribution.

Figure 1.- Spatial distribution of abundance (number of individuals per trawl hour) of Parapenaeus longirostris in Mauritanian waters during the Spanish research surveys carried out in 2007, 2008, 2009 and 2010.

In order to study possible temporal variations of P. longirostris distribution, yields obtained from the IEO observations onboard the shrimper fleet in 2010 were analysed. Annex 1a and 1b shows spatial distribution of yields during the four fishing trips. However, it should be noted that the registered spatial abundance is highly dependent on the fishing strategy of one single vessel. Therefore, this information can only give an idea of possible temporal variations, which should be confirmed by further analysis. The fishing strategy deployed by these vessels can be inferred in Figure II, which shows the percentages of hauls corresponding to each type of fishing hauls (LAN, GAM or ALI, when targeting F. notialis, P. longirostris or Aristeus varidens, respectively). This strategy follows the abundance of the resources through the year (Figure 3). The observations from 2010 are in agreement with the general seasonal pattern followed by the Spanish shrimp fishery in Mauritanian waters. In general, deep-water rose shrimps are targeted during the winter months (from January to April, until the spring closed season), when the resource is more abundant (Figure 3). The length of the “gamba” season depends, indeed, on the abundance of this species that can be very variable from one year to another. Although the fleet usually targets F. notialis during the summer

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FAO/CECAF WG on the assessment of demersal resources-North-2013 months (Figure 2), very high yields of P. longirostris were obtained in the small number of GAM fishing trawls conducted in July and August.

100%

80%

60% ALI

40% LAN CLOSED CLOSED SEASON SEASON GAM 20%

0% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2010 Figure 2.- Percentage of hauls targeting F. notialis (LAN), P. longirostris (GAM) and A. varidens (ALI) by month, during the fishing trips carried out by IEO observers on board Spanish shrimper vessels operating in Mauritania in 2010.

P. longirostris F. notialis 100 hour) 80

60 (kg/trawl

40 CLOSED SEASON CLOSED SEASON yield

20 Mean 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2010 *November data from the selectivity trial “Mauritania 1110” Figure 3.- Mean monthly yields (kg/trawl hour) of P. longirostris and F. notialis in the fishing trips carried out by IEO observers on board Spanish shrimper vessels operating in Mauritania in 2010.

With this spatial and temporal information obtained from the onboard observations, we could think that P. longirostris was more abundant in the southern area during the first semester of 2010, as this area was the main fishing ground used by the shrimper vessels where the observations were made during this period (Annex Ia). However, the analysis of fishery information coming from Vessel Monitoring System (VMS) and logbooks of all the Spanish fleet operating in Mauritania during 2011 does not show the same pattern (Sobrino, pers. comm.) Therefore, the spatial and temporal patterns observed from the onboard observations in 2010 should not be considered as the general pattern of the all the fleet every year. Higher yields (>100kg/h of fishing trawl) were registered at depths between 155 and 247 m in all this fishing area (16ºN to 17.5ºN). During the second semester, P. longirostris was exclusively

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FAO/CECAF WG on the assessment of demersal resources-North-2013 fished in the North, probably due to the fact that the fleet is targeting F. notialis in this area. In the third quarter (LANGAMAU-0310) yields were the highest of the year (Figure 3) and they were especially high north Cape Timiris, in front of Tidra Island; where also greater abundances were detected in the Spanish surveys onboard the R/V Vizconde De Eza. Maximal yields during this fishing trip were obtained at a depth range of 183-201 m. Only 13 fishing hauls targeting deep water rose shrimp were carried out during the last fishing trip (LANGAMAU-0410). This were conducted south Cape Timiris, around 19ºN and at shallower depths (93-161 m). Yields obtained were the lowest in the year.

Reproduction P. longirostris is a short-living species with high growth rates. The life span of each generation is of two or three years, with males growing more slowly than females (Sobrino et al., 2005). The eggs, kept under the abdomen, are released into the water at the time of spawning which occurs at depths between 200-300 m, mostly on the edge of the continental slope. The young shrimps migrate towards the coast and are concentrated at depths of 50-150 m. Once they reach adulthood they migrate to depths between 200 and 300 m to reproduce. In absence of biological studies that could confirm the identity of P. longirostris stocks in West African waters, a single stock is considered for Mauritania. Taking into account that the species is found in different geographical zones, the FAO/CECAF Working Group has adopted three different stock units in North West African waters corresponding to the country limits: Morocco, Mauritania and -The Gambia (FAO, 2010). While the existence of two different stocks in Morocco and Mauritania seems quite clear, biological studies are needed to confirm the identity of different stocks in Mauritania and Senegal-The Gambia.

Table II.- Spawning periods of Parapenaeus longirostris in West African coastal countries.

AREA SPAWNING PERIOD REFERENCES Two peaks: * Summer (June) Sobrino and García, 1994 * Autumn (October) MOROCCO Two peaks: *Winter (January-February) Laghmari et al., 2001 *Autumn (October)

Two peaks: 1 *Summer (June-July-…?) García-Isarch* (pers.comm.) *Winter (December-February) MAURITANIA December-January EU/RIM WG, 1997 June-October Diop (pers.comm.) October FAO, 2006a Two peaks: CONGO Spring (April-May) Crosnier et al., 1970 Autumn (September-October) *1 Based on the sampling (from 2003 to 2008) of P. longirostris landed by the Spanish shrimper fleet operating in Mauritanian fishing ground.

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The reproduction period of shrimps should be estimated on the basis of the proportion of mature females, as males mature very young. Currently, there is a lack of clear information about the shrimp maturation season in Mauritanian waters. In other areas of the West African coast, two spawning peaks have been described: June and October (Sobrino and García, 1994) or October and January-February (Laghmari et al., 2001) in Moroccan waters; one spring peak (April-May) and a second weaker autumn peak (September-October) in Congolese waters (Crosnier et al., 1970) (Table II).

Males‐Parapenaeus longirostris n=6257

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov* Dec

% Mature males % Immature males

Females‐Parapenaeus longirostris n=6508

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov* Dec

% Mature females % Immature females

*November data from the selectivity trial “Mauritania 1110” Figure 4.- Monthly proportion of mature and immature males (top) and females (bottom) of Parapenaeus longirostris sampled by IEO observers on board Spanish shrimper vessels operating in Mauritania in 2010.

A new attempt to study the spawning period of the species was tried by IEO, through the analysis of the biological data registered in the onboard observations carried out in Mauritania in 2010. Monthly variations of the proportion of maturity stages of males and females were analyzed (Figure 4). As most males are mature during the sampled months, the proportion of mature females is used to identify the spawning season of this species. However, the

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FAO/CECAF WG on the assessment of demersal resources-North-2013 percentage of mature females was very low during all the sampled months or even zero (in April and July), although the number of sampled specimens was very high (> 6500 individuals). A slight increase of the proportion of mature females was recorded in August, but still lower than 20% of the total females, and therefore not significant in order to estimate the first maturity size of the species. The little number or absence of mature females could be associated to the small size of the individuals fished through the sampled months (in this year see Annex III and Figure 5). It is also worth mentioning the lack of information of 5 months (4 of them due to the closed season).

Population structure Length frequency distributions (length=cephalotorax length CL) obtained from the IEO onboard samplings were analyzed in order to study the population structure of P. longirostris in Mauritania in 2010. This analysis was performed in a monthly basis and separately for males and females, as this species shows different growth rates by sex.

Table III.- Maximum, minimum and mean length (CL in mm) and number of specimens of P. longirostris, by sex, sampled in the IEO scientific observations on board Spanish shrimper vessels operating in Mauritania in 2010.

CL min CL max CL mean Number P. longirostris (mm) (mm) (mm) specimens

Male 12 29.5 22.2 6257

Female 11 36 23.5 6508

Histograms of length frequency distribution of P. longirostris catches (including discards) in Mauritania (2010) are showed in Annex 3. Figure 6 shows the evolution of monthly mean lengths through the sampled year. Monthly variations of sex proportions are shown in Figure 7. It is worth remembering the lack of samplings either due to the cease of the fishery during the closed seasons or to the lack of catches during September and December. Samples could be obtained in November during the experimental selectivity trial “Mauritania 1110”. A total number of 12765 specimens were sexed and measured during the scientific onboard observations. As mentioned before, there are clear sex-dependent differences in size, females being bigger than males (Table III). Length (CL) ranged between 12-29.5 mm (males) and between 11-36 mm (females) during the sampling year. In spite of the great differences in maximal CLs, mean CLs were not so different between males (22.2 mm) and females (23.5 mm). The proportion of males and females was quite equal during the sampling months, with a slight higher presence of females (51%). Only during the summer months (July and August), the proportion of females was clearly higher (Figure 8). Bigger individuals of P. longirostris were caught during the winter-spring months, when the fleet especially targets this species (Figure 2). Modes increased from 22.5 mm and 24 mm CL (males-females) in January and February to 23 mm (males) and 25 mm (females) in March- April. Mean sizes of the total population were quite stable during the winter months, with a slight increase (22.7Æ23.3) from January to April (Figure 5). The smallest individuals were caught after the closed season, during the summer (July-August), with modes of 19-19.5 mm

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(males) and between 20 and 22 mm (females) and when the smallest mean CLs were estimated (18.1 mm and 19.9 mm in July and August, respectively, see Figure 6). No samples of this species were obtained during September and December (due to the fact that all the fishing operations targeted F. notialis) and October (due to the autumn closed season). Sampling in November showed a higher percentage of small individuals. Therefore, the analysis of the length distributions of the deep water rose shrimp showed a possible recruitment period of the species during the summer that could last at least until November. This recruitment period of P. longirostris would be coincident with the F. notialis fishing season (Figure 2).

Parapenaeus longirostris‐2010 29 27 25 23 21 (mm) 19 CL 17 15 13 11 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov* Dec

*November data from the selectivity trial “Mauritania 1110” Figure 5.- Monthly evolution of mean cephalotorax length (CL in mm) of P. longirostris sampled by IEO observers on board Spanish shrimper vessels operating in Mauritania in 2010.

Parapenaeus longirostris‐2010 n=12 236 100 90 80 70 60 50 40

Perecnetage 30 20 10 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Male Female

Figure 6.- Monthly evolution of male and female proportion in the P. longirostris population sampled by IEO observers on board Spanish shrimper vessels operating in Mauritania in 2010.

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Sex ratio Sex-ratio obtained from the IEO observers’ sampling programme onboard Spanish shrimpers showed the same percentages of males and females in the whole population (F:M=1:1). This equality may be associated to the scarcity of big individuals in catches, that would have increased the females proportion, as it is well known that P. longirostris has a differential growth by sex, with females reaching bigger sizes than males. The sex-ratio varies among the different CL classes: for samples of CL>24 mm, more than 50% of the sampled specimens were females; for samples CL>31 mm, 100% of the sampled specimens were females (Figure 7). Practically all individuals bigger than 26 mm CL were females.

Parapenaeus longirostris‐ 2010 100 90 80 70 60 50 40

Percentage 30 20 10 0 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Male Female

Figure 7.- Females and males proportion by length class (CL in mm) in the P. longirostris population sampled by IEO observers on board Spanish shrimper vessels operating in Mauritania in 2010.

Growth The Modal Progression Analysis (MPA), performed by the Bhattacharya method showed to age groups or cohorts by sex (Figure 8 and Table IV). However, these results should be considered with caution, as they only correspond to the analysis of six months data. In addition, the small values of mean sizes suggest that at least one age class of bigger individuals could be missing, as they were not collected in the catches of these six months. Group 1 of males and females belong to the recruitment peak detected during the summer months.

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FAO/CECAF WG on the assessment of demersal resources-North-2013

Parapenaeus longirostris- Males

Parapenaeus longirostris- Females

Figure 8.- Length frequency distribution of males (top) and females (bottom) of P. longirostris, with lines indicating the cohorts identified by the Bhattacharya method. Mauritania-2010.

Table IV.- Mean length (cephalotorax length CL in mm) and associated standard deviation, and population (number of individuals) by age group for males and females of P. longirostris caught by Spanish shrimper vessels operating in Mauritania in 2010.

Mean P. longirostris Groups s.d. Population (CL in mm)

1 18.16 0.93 276 Male 2 22.35 1.49 5782

1 17.53 2.33 311 Female 2 23.60 2.12 5874

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Abundance fluctuations The deep water rose shrimp exhibits great interannual fluctuations, mainly attributed to recruitment strength. Long-term changes in the abundance of P. longirostris in the Mediterranean Sea were found to correlate significantly with identified environmental and anthropogenic factors. The increasing abundance of the species was correlated to a rise of sea surface temperature, a corresponding decrease of wind circulation and to the reduction of fishing effort (Ligas et al., 2011). The availability of suitable information on environmental characteristics, such as appropriate sea-floor topography, sediment composition, hydrographical characteristics, and trophic webs (prey availability, presence and abundance of predator species) is necessary to better understand the temporal change in this species abundance, distribution and biology.

Southern pink shrimp Farfantepenaeus () notialis

Spatial distribution The southern pink shrimp F. notialis is found in intertropical and subtropical areas, both in the West and East Atlantic Ocean. In the Eastern Atlantic, its distribution areas extend from Cape Blanc in Mauritania (northern limit) to Cape Frio, in southern Angola (southern limit) (Lhomme, 1981). F. notialis is a short-living species, with high growth rate and a life span of around 20 months (Caverivière, 2002). Life cycles of all Penaeus species are related to estuarine and coastal waters, since most of the time, they inhabit in areas under the influence of deltas, estuaries and lagoons, on muddy or muddy-sandy bottoms, rich in organic matter. The sediment nature is considered as a major factor influencing the geographical distribution of this species and partially responsible of the upper bathymetric limit of the species distribution (Lhomme and Vendeville, 1993). A total of 14 stocks of F. notialis have been identified along the West African coast (Garcia and Lhomme, 1979; Lhomme, 1981). Two different unities have been identified in the northern region of the West African coast, one in Mauritania and another in Senegal. In Mauritania, the species is found from the Arguin Bank (in the north) to the Senegal River mouth (in the South) and these two areas have been suggested to correspond to 2 different stocks: (i) the North stock located in the Arguin Bank (between 18º 50’ N and 20º 00’ N), with some dispersion zones as far as the Levrier Bay (probably coming from a nursery area in the Arguin Bank or, more specifically around Tidra Island); and (ii) the South stock, located between Nouakchott and Saint Louis related to the Senegal River, this shared between Mauritania and Senegal. Furthermore, two subpopulations have been defined in the northern area (North stock): one in the Arguin Bank and another south of Cape Timiris. The southern pink shrimp is distributed in a depth range between 2 and 100 m. Its highest abundance is found at different depths, depending on the area. In nearer West African coasts, maximal abundance has been found at 50 m (Saint-Louis), and 35 m (Roxo), in Senegal. The Spanish surveys carried out in Mauritanian waters during the period 2007-2010 prospected depths over 84 m that did not bring any information about the species distribution. Therefore, the information on spatial (and temporal) distribution of F. notialis comes from the IEO scientific observations onboard the Spanish shrimper fleet in Mauritanian waters during 2010. Annex 2a and 2b shows spatial distribution of F. notialis yields during the four fishing trips carried out in 2010. The Southern pink shrimp was caught in a depth range of 13-69 m.

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Greatest yields (>100kg/h trawl) were obtained between 15 and 44 m, and at latitudes between 19º-20ºN. There were seasonal variations on abundance. Higher yields were recorded during the second semester of the year, from July to the November-December (Figure 3), the period when the fleet especially targets this species (Figure 2). Spatial variations of the fishing operations targeting F. notialis could be observed, depending the season of the year. During the first semester, when the fleet was mainly targeting P. longirostris, low yields of F. notialis were registered in the South area (16.2-17.3ºN). However, no comparisons can be made with the North area, as most of the trawls were conducted in the South, where P. longirostris was probably more abundant during that period. The southern pink shrimps catches of the first semester could correspond to the South unity between Nouakchott and Saint Louis described above. During the third quarter (LANGAMAU-0310), F. notialis was fished in two main fishing grounds: one in the North area (19ºN-20ºN), and another in the South area, mostly southern Nouakchott (17.3ºN-17.8ºN). The depth range in the South area was slightly deeper (33-52 m) than in the North. Greatest yields were obtained in the North area. During the fourth quarter (LANGAMAU 0410), the species was exclusively caught in the North area, between 18.9ºN-20.0ºN with the higher yields recorded between 19.5 ºN (in front of Tidra Island) and 19.9ºN. Thus, during the second semester, both F. notialis unities were exploited: the North unity (Arguin Bank) with its possible two subpopulations (Arguin Bank and south Cape Timiris) and the South unity (southern Nouakchott). The life cycle of F. notialis is quite complex, being composed of a juvenile phase, that takes place in estuaries or coastal lagoons, and an adult phase that is developed at sea (Garcia and Le Reste, 1981; Lhomme, 1981; Lhomme and Garcia, 1984 ; Lhomme and Vendeville, 1993; Lhomme, 2001). This life cycle can be summarized as follows: Spawning takes place in the open sea. Larvae and first postlarvae are planktonic. At the end of their planktonic phase at sea (around 3 weeks), larvae develop into postlarvae and move to coastal and brackish zones (estuaries and coastal lagoons) by a semi-active process in which they displace themselves by using the tide floods. This migration is explained because the juveniles search the fresh water. Juveniles remain into the estuaries for approximately 3 months, before they migrate back to the sea. Juveniles use again the tide floods to their seawards migration, but in this case, the night descendent tides. Once at sea, juveniles acquire benthic habits and continue their growing, which is maximum at 3-4 months. At this moment, the females start their maturation processes, as male maturation is much more precocious and usually has occurred previously, in coastal areas. Southern pink shrimps continue their maturation while they grow and expand to deeper areas, already into the fishing grounds. After reaching their first maturity size, and when the environmental conditions are favourable, the spawning takes place and a new cycle begins. The more precocious individuals can spawn at 6-7 months, although massive maturation (when most of the individuals of the same cohort spawn), takes place at around age 1 year (Garcia, 1977). Nevertheless, the above explained life cycle of F. notialis, which is similar for all the species of the Genus Penaeus worldwide, surprisingly is not the same for the Northern stock of this species in Mauritania. Its life cycle occurs around the Arguin Bank, which constitutes an important reproduction and nursery area for this stock. However, there are not any estuaries, coastal lagoons, river mouths or, in general, brackish waters in the Arguin Bank, where juvenile phase develops, as it occurs in other areas. Therefore, the Arguin Bank stock constitutes a great exception in relation to the biological behaviour of F. notialis, whose biological explanation remains unclear.

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Reproduction As explained above, two main unities, belonging to two possible different stocks of F. notialis have been described in Mauritania: one in the Arguin Bank (North stock) and another in the Senegal River mouth (South stock), the last being shared between Mauritania and Senegal. As F. notialis males develop very early and are mature through all the year, the reproductive seasons of F. notialis should be identified following the proportion of the mature females in the female population. The IEO programme of scientific observers onboard Spanish shrimper vessels in Mauritanian fishing grounds during 2010 showed that although mature females were present during all sampled months (Figure 8), a spawning peak may occur between July and October, as higher proportions were found during August and September. However, no data can confirm that the spawning peak lasts until October, as this month could not be sampled due to the closed season (as previously explained for P. longirostris).

Males Farfantepenaeus notialis n=5211

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov* Dec

% Mature males % Immature males

Females Farfantepenaeus notialis n=7585

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov* Dec

% Mature females % Immature females

*November data from the selectivity trial “Mauritania 1110” Figure 8.- Proportion of mature and immature males (top) and females (bottom) of Farfantepenaeus notialis sampled by IEO observers on board Spanish shrimper vessels operating in Mauritania in 2010.

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Other studies of this species carried out in Senegal (Lhomme and Garcia, 1984) and in Côte d’Ivoire (Lhomme and Vandeville, 1993), showed a continuous reproductive period all year round, although the existence of 2 spawning peaks by year is very frequent, even if their timing varies depending on the concerned area. In Senegalese waters, the reproductive periods of the Saint-Louis and Roxo-Bissagos stocks have been described (Lhomme and Garcia, 1984). In Saint-Louis, (which probably is the same Mauritanian South stock, shared by Mauritania and Senegal), the spawning period of F. notialis extends from August to December, with a peak between September and November. These reproductive peaks are related to the start and the end of the warm season. Although the spawning peak defined by the IEO observations could not be temporally limited due to sampling constrictions, we could think that this period was more or less coincident with the spawning period defined for the Saint-Louis stock. Relative abundance of mature females of F. notialis has been related to the moments with highest planktonic abundance, both in Senegal (Lhomme, 1981) and in Côte d’Ivoire (Lhomme and Vandeville, 1993). This adjustment of the southern pink shrimp reproductive cycle and the primary production cycle ensures a higher larval survival, due to the planktophagous feeding habits of the larvae (Garcia, 1977). Therefore, primary production plays a very important role in the reproduction of the species. There is not any published information about size at first maturity of F. notialis in Mauritania. Males mature very early and throughout the year, and therefore, females’ first maturity length should be the significant information for the establishment of any management measures related to the minimal catch size.

Size (CL) at first maturity (L50) for females was estimated considering that the spawning peak occurs in August and September, by using a Generalized Linear Model (GLM) with binomial errors (logistic regression), through the R package Inbio (Sampedro et al., 2005). The CL at first maturity estimated for females was 28.4 mm (c.v.= 0.012) (Figure 9).

Farfantepenaeus notialis-Females 2010

% Maturity % Predicción Original Predicción Bootstrap 0.0 0.2 0.4 0.6 0.8 1.0

20 30 40 50 CL (mm)

Figure 9.- Maturity curve of Farfantepenaeus notialis (females). Mauritania 2010.

This first maturity size of F. notialis in Mauritania (28.4 mm CL) is in agreement with other estimations in near areas as: 28-29 mm for the stock Roxo-Bissajos of Senegal (Lhomme, 1981; Lhomme and Garcia, 1984), 28 mm in (De Vries and Lefévere, 1969); but lower than the L50 of 30-31 mm estimated for the same species in Cote d’Ivoire (Lhomme and

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Vendeville, 1993) and higher than 25 mm of the stock Saint Louis in Senegal (Lhomme, 1981; Lhomme and Garcia, 1984) (Table V).

The L50=28.4 mm could be considered as the first valid estimation of the first maturity size of F. notialis in Mauritania. However, further studies should be carried out to confirm the possible existence of two stocks in Mauritanian waters: a North stock, in the Arguin Bank and a South stock, in the Senegal River mouth, this last between Mauritanian and Senegalese waters.

Table V.- First maturity size (CL, in mm) of Southern pink shrimp Farfantepenaeus notialis in West African waters. L ♀ AREA 50 REFERENCE (mm CL) Mauritania 2010 28.4 García-Isarch et al., 2011 Senegal (Saint Louis)1 25 Lhomme, 1981

Senegal-G. Bissau (Roxo-Bissagos)2 28-29 Lhomme, 1981; Lhomme & Garcia, 1984

Côte d’Ivoire 30-31 Lhomme and Vendeville, 1993 Nigeria 28 De Vries and Lefévere, 1969

1Probably corresponds to the South Stock of Mauritania 2 Probably corresponds to the Stock of Guinea-Bissau

The mean age at first maturity has been estimated in 7.7 months for the Senegalese stock of Saint-Louis, based on the age of the individuals during the spawning peak (Lhomme, 1981). The maximal age of the Senegalese F. notialis has been estimated in approximately 23 months, corresponding to females of 50 mm CL.

Population structure A total number of 12 798 southern pink shrimps were sampled for sex and length (CL) during the IEO scientific observations onboard the Spanish shrimpers in Mauritania, 2010. F. notialis growth rates are highly sex-dependent and females reach bigger sizes than males. Males CLs ranged between 14 and 47 mm CL. Females reached CLs as big as 58 mm. Mean sizes were 26.3 and 34.6 mm CL for males and females, respectively (Table VI). Female proportion was also higher in the total sampled population (59% females and 41% males). The histograms of Annex IV show the length frequency distributions of F. notialis by sex and sampled month. Monthly evolution of mean CLs through the sampled year and monthly proportion of males and females in the population are respectively showed in Figures 10 and 11. It is worth reminding the impossibility of having a complete sampled year due to the cease of the fishing activity during the closed seasons (spring and autumn). However, samples could be obtained in November, through the experimental survey “Mauritania 1011”.

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Table VI.- Maximum, minimum and mean length (CL in mm) and number of specimens of F. notialis by sex, sampled in the IEO scientific observations on board Spanish shrimper vessels operating in Mauritania in 2010..

F. notialis CL min CL max CL mean Number (mm) (mm) (mm) specimens

Male 14 47 26.3 5213

Female 15 58 34.6 7585

Length frequency distributions of the southern pink shrimp (Annex IV) show that male sizes were very similar all year round, with a mode of 27 mm cephalotorax length (CL). However, males dominated during winter and spring (December-April), when females were smaller and less abundant (mode between 30-34 mm of CL). Female’s mode increased along the year to reach maximum values (36-37 mm) during the summer months (July-September), when the fishing activity for this species increased. The southern pink shrimp is especially targeted during the summer months (from July to September, between the two closed seasons) and at the end of the year (Figure 2), when the yields are higher (Figure 3). Mean CLs were quite high during all the sampled months, ranging from 33.5 mm to 39.5 mm. However, mean sizes highly rose during the summer months (Figure 10) which logically meant an increase of the females in the population (Figure 11), as males do not reach the big sizes dominant during these months. A recruitment season cannot be exactly located on the basis of the length frequency distribution of F. notialis catches from the Spanish shrimper fleet. This is due to the fact that the Spanish industrial fleet does not catch the recruitment fraction of this species, as its distribution is much shallower than the operational area of the fleet. However, a sharp decrease of mean sizes identified in the November samples (mean CL=28.4) suggests that F. notialis recruitment may happen at least during the previous month. Previous studies in the same area confirm a recruitment season during the last months of the year (Sobrino and García, 1993). Greatest individuals were found during the summer, when the southern pink shrimp becomes the target species of the shrimp fishery. Farfantepenaeus notialis‐2010 50 45 40 35 (mm)

CL 30 25 20 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov* Dec Figure 10.- Monthly evolution of mean cephalotorax length (CL in mm) of F. notialis sampled by IEO observers on board Spanish shrimper vessels operating in Mauritania in 2010.

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Farfantepenaeus notialis‐ 2010 n=12 126 100 90 80 70 60 50 40 Percentage 30 20 10 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Male Female

Figure 11.- Monthly evolution of male and female proportion in the P. longirostris population sampled by IEO observers on board Spanish shrimper vessels operating in Mauritania in 2010.

Sex ratio The 2010 samplings of the IEO observers onboard Spanish shrimper vessels in Mauritanian fishing grounds showed that most of the specimens bigger than 30 mm CL were females (Figure 12). At sizes of approximately 36 mm CL, almost 100% of the specimens were females. The sex-ratio estimated from these samplings was 1:0.7 (F:M). This higher proportion of females in the population has also been described for the species in Guinea- Bissau (García-Isarch et al., 2009) and Côte d’Ivoire (Garcia, 1977). However, the proportions of both sexes are the same in estuarine environments (Garcia, 1977). Farfantepenaeus notialis‐ 2010 100 90 80 70 60 50 40

Percentage 30 20 10 0 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58

Male Female

Figure 12.- Females and males proportion by length class (CL in mm) in the F. notialis population sampled by IEO observers on board Spanish shrimper vessels operating in Mauritania in 2010.

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Growth Growth rates are very variable, depending on the different stages of the life cycle. The theoretical growth of the Saint-Louis stock (which may correspond to the South stock of Mauritania) ranges between 29 and 46 mm of total length (TL) per month, for juveniles with sizes between 10 and 100 mm TL (Lhomme, 1981). In general, juveniles’ growth, occurring in estuarine and brackish waters, is very fast. Adults’ growth, occurring at sea, is more difficult to study. There are important seasonal variations in growth, related to hydroclimatic fluctuations (Lhomme and Garcia, 1984). It has been generalized that monthly growth rate varies between 30 and 60 mm of TL during the juvenile stage and decreases with age since a certain moment. Furthermore, growth also varies depending on the population abundance and the temperature (Garcia and Le Reste, 1981): faster growth during the warm season and slowing down during both the cold season and, apparently, the spawning season (Lhomme and Garcia, 1984). Three annual cohorts of males and four cohorts of females of F. notialis were detected through the MPA (Bhattacharya method) of the population sampled by the IEO scientific observers onboard the Spanish shrimper fleet in Mauritania during 2010 (Figure 13 and Table VII).

Farfantepenaeus notialis- Males

Farfantepenaeus notialis- Females

Figure 13.- Length frequency distribution of males (top) and females (bottom) of F. notialis, with lines indicating the cohorts identified by the Bhattacharya method. Mauritania-2010.

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Table VII.- Mean length (cephalotorax length CL in mm) and associated standard deviation, and population (number of individuals) by age group, for males and females of F. notialis caught by Spanish shrimper vessels operating in Mauritania in 2010.

Mean F. notialis Groups s.d. Population (CL in mm)

1 22.71 2.07 1222

Male 2 27.14 1.65 3613

3 32.04 1.99 293

1 23.72 2.60 502

2 28.36 1.95 979 Female 3 35.74 3.45 5239

4 44.31 2.96 475

Mean cephalotorax lengths of groups 1, 2 and 3 of females are bigger than those groups of males, this indicating faster growth in females than in males. In addition, the presence of a fourth cohort in females is due to their higher growth rate. Thus, all individuals reaching this mode (44.31 mm) are only females. The existence of several cohorts through the year is related to a more or less continuous spawning process around the year, as it was showed to occur by the presence of mature females during all sampled months (Figure 8). The most important cohort (in terms of population size), which is Group 2 of males and Group 3 of females may correspond to that originated by the main spawning peak of the species.

Migrations Concerning the migratory features of the species, it can be said that F. notialis carry out three main migratory movements in the course of its life-cycle: 1) Larvae and postlarvae move from the open sea to coastal waters, entering into brackish waters of estuaries or coastal marshes (with the exception of the North stock in Mauritanian), searching for appropriate bottoms for their nursery and feeding. In this phase they are only available to the artisanal fishery that can be developed in coastal areas. 2) During the juvenile stage they move back to the sea, to deeper and more saline waters, where reproduction takes place. In this phase they become available to the industrial fishery. 3) Southern pink shrimps do not only move in the coast-open ocean axis, but also along the coast, searching for more favourable ecological conditions related to their requirements on bottom type, trophic richness, and hydrology.

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Abundance fluctuations The dynamics of penaeid shrimps populations worldwide have long been a subject of study for research scientists and obviously of interest to the industry because of the fluctuations in annual population size and the consequent variations in annual catch which characterize the fast growing- highly fecund organisms (Forbes and Demetriades, 2005). The catch is based on the generation of the year on the 0+ year class in fisheries terms. The biomass which contributes to the catch is therefore generated each year. Initial correlation analysis (Demetriades et al., 2000) developed in South supported the relation between summer rain and offshore catch of Farfantepenaeus indicus the following winter. Subsequent more detailed consideration of the possible interactions between this species and catchment runoff included the possible negative effect of very low salinities in the nursery areas which would make them inaccessible and secondly, the possibility of the introduction of terrestrially derived nutrients into inshore waters which would contribute to phytoplankton production and thereby potential enhance survival of the planktonic larval stages. Favourable conditions for larval development in combination with favourable nursery ground conditions for the juveniles would then be reflected in greater offshore catch in the following winter. Reductions in salinity in the nursery grounds would simply act as a trigger for earlier emigration.

4.- CONCLUSIONS The EU (Spanish) fishery has been traditionally carried out in Mauritanian waters and until its temporal closure in August 2012, it had been the main fleet operating in this fishing ground for many years. Its main target species were the deep-water rose shrimp P. longirostris, which is fished at depths around 150-300 m, followed by the Southern rose shrimp F. notialis, fished in shallower waters up to 60 m and, to a lesser extent by deep catches of A. varidens. While this last deep species is harvested by means of the typical bottom trawl (“baka” type), the fishing gears are changed to outriggers (“tangon” type) to fish the main two species. The ticker chain constitutes a gear element traditionally used by the Spanish shrimper vessels, which is towed on the seabed across the mouth of the net in order to help to disturb the shrimps from the muddy seabed, causing them to rise and be caught by the net. Biological information about the two main target species P. longirostris and F. notialis was compiled and analysed from several sources in order to gain a better biological base for assessment and management purposes. One of the main sources was the IEO scientific observations onboard Spanish shrimper vessels in Mauritanian waters during 2010. The biology of the main target shrimps species in Mauritania is quite unknown. The lack or discrepancy of several studies carried out in these waters does not allow the establishment of management measures as adequate closed season or areas, accurately based on the biological cycles of P. longirostris or F. notialis, or as minimum catch sizes. On the other hand, this lack of biological information also hampers the use of alternative assessment models that could be better adapted to short living species that the one currently used in FAO/CECAF Working Groups. Biological studies are also very important to identify stocks, which are currently assessed on a national basis whereas many of them are supposed to be transboundary. In the case of P. longirostris, the existence of one single shared stock between Mauritania and Senegal-The Gambia is suspected. Regarding the southern pink shrimp F. notialis, two main unities, that could be related to two different stocks, have been described in Mauritania: one in the Arguin

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Bank (North unity) and another one in the Senegal River mouth (South unity), the last being shared between Mauritania and Senegal. Further studies should be made to confirm, if these unities correspond to different spawning groups. If this was the case, genetic studies should be recommended in order to assess the genetic different among these two spawning groups. The possible existence of two different stocks of F. notialis in Mauritania, instead one, as it has been traditionally considered in CECAF WGs would have assessment and management implications. The traditional autumn closed season established for both the cephalopod and shrimper fleet, usually in September-October, was followed by a new spring closed season (usually in May- June) imposed by the Mauritanian authorities since 2008. It is worth mentioning that these closed seasons were established in order to protect the octopus resources, without considering the biological characteristics of the shrimp species. The studies carried out until the moments do not provide enough information regarding the reproduction period of P. longirostris. However, results from onboard observations may indicate a possible recruitment period during the summer, when the fleet is mostly targeting F. notialis. Therefore, the own strategy of the shrimper fleet that target F. notialis during the summer, would protect the recruitment fraction of the P. longirostris population. With the information available, it seems clear that at least, the spring closed season does not seem to have any ecobiological sense for shrimps. In the case of the autumn closed seasons, this could be more or less coincident with the spawning season of the South stock of F. notialis, which apparently peaks between September and November (Lhomme and Garcia, 1984). However, for short living and high fecundity species, as it is the case of both shrimp species, any management measure should be more addressed to protect the recruitment fraction. In the case of F. notialis, the recruitment fraction is not exploited by the Spanish shrimper fleet, as recruits have shallower distribution than the operational distribution area of the industrial fleet. First maturity size of F. notialis was estimated for the first time for Mauritanian waters. This estimation of 28.4 mm CL is in agreement with other estimations in near West African areas. Further studies are required to improve our knowledge on the biology of both shrimp’s species in Mauritanian waters. This will allow the establishment of correct management measures targeting the protection of these populations. Taking into account the great vulnerability of these short-living species to environmental changes, correct management measures should aim the protection of the recruit fraction of the species. The continuity of this program of observers onboard, together with the jointed analysis with the results obtained by other programs (i.e.: IMROP observers program) is essential to obtain biological and fishery information, aiming both the obtaining of biological parameters needed for assessments methods and the establishment of correct management measures.

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REFERENCES

Crosnier, A., A. Fontana, J. C. Le Guen et J. P. Wise, 1970. Ponte et croissance de la crevette Pénéide Parapenaeus longirostris (Lucas) dans la région de Pointe-Noire (République du Congo). Cah. ORSTOM, (Océanogr.) 8: 89-102. Crosnier, A. et J.J. Tanter, 1968. La pêche de crevettiers espagnols au large du Congo et l’Angola. Pêche maritime 1985: 539-541. Demetriades N.T., Forbes A.T., Mwanyama, N & Quinn N.E. 2000. Damming the Thukela River. Impacts on The Thukela Bank Shallow Water Prawn Resource. Report for Department of Water Affairs and Forestry’s Thukela Water programme. De Vries. J. y S. Lefévere, 1969. A maturity key for Penaeus duorarum of both sexes. In: Actes Symposium Oceanogr. ress. Halieut. Atlant. Trop. UNESCO. Abidjan, 1966.PP: 419-424. FAO, 2010. Report of the FAO/CECAF Working Group on the Assessment of Demersal Resource. Subgroup North. Agadir, Morocco, 8-17 February 2010. / Rapport du Groupe de travail FAO/COPACE sur l’évaluation des ressources démersaux- Sous- groupe Nord. Agadir, Maroc, 8-17 fevrier 2008. CECAF/ECAF Series. FAO. Rome (in edition). Forbes, A.T. and N.T. Demetriades, 2005. A review of the commercial, shallow water penaeid prawn resource of South Africa. Status, Fisheries, Aquaculture and Management. Specialist Report for Ezemvelo KZN Wildlife. Marine & Estuarine Reasearch. 64 pp. Garcia, S., 1977. Biologie et dynamique des populations de crevettes rose (Penaues duorarum notialis Perez Farfante, 1967) en Cote d’lvoire. Travaux et Documents de l'ORSTOM, No. 79. 271 pp + appendices I-V. Garcia, S. and L. Le Reste. 1981. Life cycles, dynamics, exploitation and management of coastal penaeid shrimp stocks. FAO Fish. Tech. Pap. 203-215 pp. Garcia, S. and F. Lhomme, 1979. Les ressources de crevette rose (Penaeus duorarum notialis). In : J.P. Troadec and S. Garcia, eds. Les ressources halieutiques de l’Atlantique Centre-Est. Première partie: Les ressources du Golfe de Guinée de l’Angola à la Mauritanie. FAO, FIRM/T186.1 (Fr.). Pp:123-148. García-Isarch, E., C. Burgos, I. Sobrino, A. Mendes, I. Barri, V. Assau, R. Gomes y M. Gomes, 2009. Informe de la campaña de evaluación de recursos demersales de la ZEE de Guinea Bissau a bordo del B/O Vizconde de Eza “GUINEA BISSAU 0810”. Instituto Español de Oceanografía y Centro de Investigaçao Pesqueira Aplicada de Guinea Bissau. García-Isarch, E., Romero, Z., Barro, S. y P. Expósito, 2011a. Plan de trabajo: Campañas de observación científica a bordo de la flota marisquera española en aguas de la ZEE de Mauritania. Reunión para estandarización de metodologías de observación a bordo de buques marisqueros IEO-IMROP. Tenerife, 28 April 2011. García-Isarch, E., Z. Romero and I. Sobrino, 2011b. Fishery and biological information obtained from scientific observations onboard Spanish shrimper vessels in the Mauritanian EEZ during 2010. 5th Joint Scientific Committee RIM-UE. Nouakchott (Mauritania), 12 -14 October 2011. García-Isarch, E., Z. Romero, I. Sobrino, P. Expósito y S. Barro, 2012a. Información biológica y pesquera obtenida en las campañas de observación científica a bordo de la

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flota marisquera española en aguas de la ZEE de Mauritania (año 2010). Informe del Instituto Español de Oceanografía presentado a la Asociación Nacional de Armadores de Buques Congeladores de Pesca de Marisco (ANAMAR). May 2012. García-Isarch, E., Romero Z., Expósito P., Barro S. y Muñoz I., 2012b. Biología del langostino blanco Farfantepenaeus notialis en aguas de Mauritania (NW África). V Foro Iberoamericano de los Recursos Marinos y la Acuicultura (FIRMA). Cádiz, Spain, 26-29 de noviembre de 2012. Hernández-González, C.L., M. Bouzouma, C. Burgos, E. Hernández y C. Sid, 2010. Informe de la campaña ‘Maurit-1107’ de prospección por arrastre de los recursos demersales profundos en aguas de la República Islámica de Mauritania. Inf. Técn. IEO-IMROP: 416 pp. Laghmari, H., A. Chentoufi, A. Chafik et A. Idelhaj, 2001. Reproduction et structures en taills de la crevette rose Parapenaeus longirostris (Lucas, 1846) du Nord Atlantique Marocain. J. Rech. Océanographique, 26 (4):42-49. Lhomme, F., 1981. Biologie et dynamique de Penaeus (Farfantepenaeus) notialis (Pérez Farfante 1967) au Sénégal. Thèse Doc. Etat Sciences, Université Pierre et Marie Curie, Paris VI: 1-248. Lhomme, F. y P. Vendeville, 1993. La crevette rose Penaeus notialis (Pérez Farfante, 1967) en Côte d'ivoire. In: P. Le Loeuff, É. Marchal, J.B. Amon Kothias (éd.), Environnement et ressources aquatiques de Côte-d'lvoire. 1- Le milieu marin. Paris, Orstom : 489-520. Lhomme F. y S. Garcia, 1984. Biologie et exploitation de la crevette Penaeide au Sénégal. In: Gulland J.A., Rothschild B.J. (Eds.). Penaeid shrimps: their biology and management. Fishing News Books, Farnham, UK, pp. 111-144. Ligas, A., Sartor, P. and Colloca, F., 2011. Trends in population dynamics and fishery of Parapenaeus longirostris and Nephrops norvegicus in the Tyrrhenian Sea (NW Mediterranean): the relative importance of fishery and environmental variables. Marine Ecology, 32: 25–35. Pérez Farfante, I. and B. Kensley, 1997. Penaeoid and Sergestoid shrimps and prawns of the world. Key and diagnoses for the families and genera. Mém. Mus. nat. Hist. nat., Paris, 175:1-233. Ramos, A., C. Alcalá, F. Fernández, L. Fernández, M. González-Porto, V. López, J.A. Moya, P. Pascual, C.Presas, M.A. Puerto, F. Ramil, F. Salmerón, J.L. Sanz, J. Rey, L. Viscasillas, J.O. Abed, S.O. Baye, B.A. Ciré,B.O. Mohamed, A.O. Samba y Y.O. Valy. 2010. Estudio de los ecosistemas de la plataforma y margen continental de Mauritania. Informe de resultados de la campaña ‘Maurit-0911’. Inf. Técn. IEO- IMROP: 161. pp. Sampedro, M. P., M. Saínza y V. Trujillo, 2005. Inbio (Software para el cálculo de la incertidumbre de parámetros biológicos). Instituto Español de Oceanografia. 25 pp. Sobrino, I., C. Burgos, M. Coján, M. Bouzouma et M. Bem Lemlil, 2011. Rapport de la campagne expérimentale pour l’étude de l’impact des chaînes « racleuses » sur les captures effectués par la flotte crevetière qui travaille dans les eaux de la République Islamique de Mauritanie. Informe técnico IEO-IMROP. Tenerife, abril de 2011. 15 pp.

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Sobrino, I. y T. García, 1992. Análisis y descripción de la pesquerías de crustáceos decápodos en aguas de la República Islámica de Mauritania durante el periodo 1987-1990. Inf. Téc. Inst. Esp. Oceanogr. 112: 38 pp. Sobrino, I. y T. García, 1994. Biology and fishery of the deepwater rose shrimp, Parapenaeus longirostris (Lucas, 1846) from the Atlantic Moroccan coast. Sci. mar., 58 (4): 299- 305. Sobrino, I., Silva, C., Sbrana, M., Kapiris, K., 2005. A review of the biology and fisheries of the deep water rose shrimp, Parapenaeus longirostris, in European Atlantic and Mediterranean waters (, , ). Crustaceana Vol. 78(10): 1153-1184.

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FAO/CECAF WG on the assessment of demersal resources-North-2013 ANNEX Ia.- Spatial distribution of yields (kg/h trawl) of Parapenaeus longirostris in Mauritanian waters during the onboard observations LANGAMAU-0110 and LANGAMAU-0210 (Mauritania 2010).

LANGAMAU-0110 LANGAMAU-0210

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FAO/CECAF WG on the assessment of demersal resources-North-2013 ANNEX Ib.- Spatial distribution of yields (kg/h trawl) of Parapenaeus longirostris in Mauritanian waters during the onboard observations LANGAMAU-0310 and LANGAMAU-0410 (Mauritania 2010).

LANGAMAU-0310 LANGAMAU-0410

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ANNEX II.a- Spatial distribution of yields (kg/h trawl) of Farfantepenaeus notialis in Mauritanian waters during the onboard observations LANGAMAU- 0110 and LANGAMAU-0210 (Mauritania 2010).

LANGAMAU-0110 LANGAMAU-0210

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FAO/CECAF WG on the assessment of demersal resources-North-2013 ANNEX II.b- Spatial distribution of yields (kg/h trawl) of Farfantepenaeus notialis in Mauritanian waters during the onboard observations LANGAMAU- 0310 and LANGAMAU-0410 (Mauritania 2010).

LANGAMAU-0310 LANGAMAU-0410

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ANNEX III- Length frequency distributions (by sex) of the deep water-rose shrimp Parapenaeus longirostris. Mauritania 2010. *November data from the trial “Maurit1110”.

February 2010 March 2010 10 10 male female n=3720 male female n= 4401 8 8

6 6 4

4 individuals individuals

% % 2 2

0 0 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 CL (mm) CL (mm)

April 2010 July 2010 August 2010 12 10 10 male female male female 10 n= 1519 male female n= 259 n= 723 8 8 8 6 6 6 4 individuals 4 individuals individuals

4

% % 2 2 % 2

0 0 0 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 CL (mm) CL (mm) SPRING CLOSE SEASON CL (mm)

November 2010 15 indeterminate n= 714 10 September- NO CATCH individuals

5 December- NO CATCH %

0 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 CL (mm) October CLOSE SEASON

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ANNEX IV- Length frequency distributions (by sex) of the southern pink shrimp Farfantepenaeus notialis. Mauritania 2010. *November data from the trial “Maurit1110”.

January 2010 February 2010 March 2010 24 18 10 male male n= 155 male n= 1776 20 n= 77 15 8 female female female 16 12 6 9 12 4 individuals

individuals individuals 6 % 8

% 2 % 4 3 0 0 0 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 CL (mm) CL (mm) CL (mm)

April 2010 August 2010 10 July 2010 10 10 male n= 903 male n= 3036 8 male n= 4359 8 female 8 female female 6 6 6 4

individuals 4 4 individuals

individuals

% % 2 2 % 2 0 0 0 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 CL (mm) CL (mm) SPRING CLOSE SEASON CL (mm)

September 2010 November 2010 December 2010 12 16 10 male n= 293 14 indeterminated male n= 1527 10 8 female 12 female 8 10 6 6 8 4 individuals individuals

individuals 4 6

% %

% 4 2 2 2 0 0 0 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 CL (mm) CL (mm) CL (mm) Ootober CLOSE SEASON

31