Preliminary description of the overlap between squid fisheries and VMEs on the high seas of the Patagonian Shelf

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reliminary description of the overlap between squid fisheries and VMEs on theigh seas of the Patagonian Shelf

.M. Portelaa,∗, G.J. Piercea,b, J.L. del Ríoa, M. Sacaua, T. Patrocinioa, R. Vilelaa

Instituto Espanol de Oceanografía (IEO), Centro Oceanográfico de Vigo, PO Box 1552, 36200 Vigo, SpainOceanlab® , University of Aberdeen, Main Street, Newburgh, Aberdeenshire, AB41 6AA, UK

r t i c l e i n f o

rticle history:eceived 5 April 2010eceived in revised form 11 June 2010ccepted 15 June 2010

a b s t r a c t

Between November 2007 and April 2009, the Instituto Espanol de Oceanografía (IEO, Spanish Institute ofOceanography), together with the Spanish Secretaría General del Mar (SGM, General Secretariat for theSea), undertook a series of eleven multidisciplinary research cruises to study Vulnerable Marine Ecosys-tems (VMEs) on the high seas (HS) of the South West Atlantic. Two of these cruises, conducted during the

eywords:MEsisheriesouthwest Atlanticephalopods

austral late summer and early autumn of 2008 and 2009, focused on the status of the main commercialstocks and the interactions of fishing activities with VMEs. Two main cephalopod species (Illex argenti-nus and Loligo gahi) are targeted by the Spanish bottom trawl fishery in this area. This paper presentspreliminary results of those cruises, describing spatial distribution and abundance of both cephalopodspecies, geomorphologic, benthic and hydrographical characteristics of the study area, as well as possible

hropoarea

interactions between antis almost negligible in the

. Introduction

The southwest Atlantic (SW Atlantic), corresponding to FAOtatistical Area 41, includes the Patagonian Shelf, which is theargest shelf area in the southern hemisphere (approximately.96 million km2). A large portion of this area lies off the coast ofrgentina and extends beyond exclusive economic zones (EEZs) in

he region (FAO, 2005, 2008a) making up what is known as the higheas (HS) area, i.e. international waters beyond the 200-mile fishingones.

According to the Food and Agriculture Organization (FAO) stan-ards and criteria developed for identifying Vulnerable Marinecosystems (VMEs), “vulnerability is related to the likelihood that aopulation, community, or habitat will experience substantial alter-tion after disturbance, and the likelihood that it would recover andn what time frame. This is related to the characteristics of the ecosys-ems themselves, especially biological and structural aspects, wherehe most vulnerable ecosystems are those that are both easily dis-urbed and very slow to recover, or may never recover” (FAO, 2008c).s defined in the FAO workshop on vulnerable ecosystems and

Please cite this article in press as: Portela, J.M., et al., Preliminary descriptiof the Patagonian Shelf. Fish. Res. (2010), doi:10.1016/j.fishres.2010.06.009

estructive fishing in deep-sea fisheries (FAO, 2008b), VMEs aredentified according to the vulnerabilities of their components andefer, in technical terms, to ecotopes – the finest scale units used inapping ecosystems.

∗ Corresponding author. Tel.: +34 986492111; fax: +34 986498626.E-mail address: [email protected] (J.M. Portela).

165-7836/$ – see front matter © 2010 Elsevier B.V. All rights reserved.oi:10.1016/j.fishres.2010.06.009

genic activities and VMEs. The detected presence of vulnerable organismswhere fishing activities take place.

© 2010 Elsevier B.V. All rights reserved.

The European Commission has defined VMEs as “any marineecosystem whose specific structure and function is, according to thebest scientific information available and to the principle of precaution,likely to be compromised by stress resulting from physical contact withbottom gears in the course of fishing operations, including inter aliareefs, seamounts, hydrothermal vents, cold water corals or cold watersponge beds” (EC, 2007a).

The variety and abundance of fishery resources and fisheries inthe Patagonian Shelf are determined by the topography and otherphysical characteristics, including environmental conditions whichare dominated by the convergence of the warmer south-flowingBrazil Current and the colder north-flowing Falkland-MalvinasCurrent (FAO, 2005). The Patagonian shelf area is characterizedby the dominance of demersal finfish species, but cephalopodspecies such as the Argentine shortfin squid (Illex argentinus)and the Patagonian squid (Loligo gahi) are also present, theformer being the cephalopod species most frequently fishedby the Spanish bottom trawl fleet operating in the area since1983.

Regarding the assessment and management of these fisheries,a key point is that no multilateral regime is currently in placefor fisheries in the SW Atlantic (including the HS), this regionbeing the only significant area for HS fisheries not covered by any

on of the overlap between squid fisheries and VMEs on the high seas

Regional Fisheries Management Organisation (RFMO) (EC, 2007b;FAO, 2008a). The international community has agreed on thepressing need to adopt measures to protect vulnerable marineecosystems from the destructive effects of bottom fishing activities(EC, 2008). An additional issue is the fact that most of the finfish and

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Fig. 1. Study area of fishery

ephalopod stocks fished on the HS are straddling stocks (Maguiret al., 2006).

The Argentine shortfin squid and the Patagonian squid are bothhared and straddling stocks with a life cycle of about one yearHatfield, 1991; Agnew et al., 2000; Waluda et al., 2002), andheir biomass is greatly dependent on environmental conditionsWaluda et al., 1999, 2001; Arkhipkin et al., 2004; FAO, 2005). Thergentine shortfin squid is one of the main commercial fisheryesources of the SW Atlantic, extending over the Falklands (Malv-nas) fishery conservation zones and Argentinean EEZ, as well asccurring in the HS. Its short (annual) life cycle and its highlyariable migration and recruitment patterns result in considerablenterannual variations of its biomass, a major issue for stock assess-

ent and management (Barton et al., 2004; Agnew et al., 2005).Spanish flagged vessels make up the majority of the Commu-

ity’s fleet operating in the SW Atlantic bottom gear fisheries.etween 22 and 27 Spanish bottom trawlers operated in the SWtlantic over the period 2003–2006, with a high seas catch of4,967 tonnes of which over 80% consisted of Argentine hake andrgentine shortfin squid (FAO, 2008a).

The United Nations General Assembly (UNGA) adopted, inecember 2006, resolution 61/105 on Sustainable Fisheries, call-

ng on flag states and RFMOs to immediately act for the sustainableanagement of fish stocks and to protect VMEs from destructive

shing practices: (i) Through assessment of the impact of individ-al bottom fishing activities; (ii) By preventing significant adverse

mpacts on VMEs, closing areas of the HS to bottom fishing whereMEs are known or likely to occur; and (iii) Ensuring the long-termustainability of deep-sea fish stocks.

Consistent with the FAO International Guidelines for the Man-gement of Deep-Sea Fisheries in the HS (FAO, 2009), the approachgreed by the UNGA in Resolution 61/105 and the European Com-ission recommendations, the IEO conducted a series of elevenultidisciplinary cruises between November 2007 and March

009. These cruises aimed to map and identify VMEs and two ofhem, carried out during the Southern Hemisphere late summer-arly autumn of 2008 and 2009, assessed the status of the main

Please cite this article in press as: Portela, J.M., et al., Preliminary descriptiof the Patagonian Shelf. Fish. Res. (2010), doi:10.1016/j.fishres.2010.06.009

shed stocks on the HS of the SW Atlantic (Argentine shortfin squidnd Patagonian squid being among the target species).

The objectives of this paper are to describe spatial distribu-ion and abundance of both cephalopod species, geomorphological,enthic and hydrographical characteristics of the study area, as

ch cruises (2008 and 2009).

well as how fishing activities could interact with the vulnerableorganisms and ecosystems found.

2. Materials and methods

The research cruises encompassed five scientific disciplines:cartography, geology, benthos, hydrography and fisheries. Theywere carried out by the IEO and the SGM, on board the SpanishRV “Miguel Oliver” owned by the SGM.

The two surveys aimed at stock assessment (ATLANTIS 2008 andATLANTIS 2009) were conducted between 10th March–18th April2008 and 24th February–1st April 2009. Their main objectives wereto: (i) assess the fishery resources on the HS of the Patagonian shelfand slope, and improve knowledge of the demographic structureof their populations; (ii) sample megafaunal epibenthic communi-ties present in the catch; (iii) map the seabed and seismic profilesto complete bottom bathymetry and identify suitable places forbottom trawling; (iv) study the oceanographic conditions in thearea, and (v) study the interactions between fishing activities andVMEs.

The study area was the zone between parallels 44◦S and 48◦S,east of the Argentinean EEZ and north of the Falkland/MalvinasConservation Zones, down to the 1500 m depth contour (Fig. 1).

2.1. Geomorphology

Navigation during the survey was via a differential GPS Sim-rad GN33 using satellite corrections integrated in an inertial aidedSeapath 200 system for an accuracy of 0.7 R. The morphology ofthe seafloor was obtained with a Kongsberg Maritime AS SimradEM-302 (30 kHz) multibeam echo sounder.

The Kongsberg-Simrad EM302 recorded backscatter strengthvalues from each single beam. Morphological data were obtainedusing ArcGis (ESRI) and the Fledermaus software suite from Inter-active Visualization Systems (IVS) and were used to provide final3D images of the seafloor morphology. Applied Microsystems SVPlus equipment was used to make the necessary sound velocity

on of the overlap between squid fisheries and VMEs on the high seas

corrections to the multibeam bathymetry data.A very-high-resolution sub-bottom profiler seismic paramet-

ric system TOPAS 18 (TOpographic PArametric Sonar) was used,simultaneously with multibeam data to obtain very high resolutionseismic profiles able to provide vertical sub-bottom information to

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Table 1Main characteristics of the fishing gear rigged by the R/V “Miguel Oliver”.

Fishing gear LOFOTEN (bottom otter trawl)Float rope/foot rope 31.20/17.70 mRigging 27 steel bobbins 35 cm ØFloats 20 (mouth) + 2 × 16 (wings)Legs 8 m, 16 mmVertical opening 3.5 mBridles 200 m, 50 mmOtter boards Polyvalent, 850 kg

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- For each stratum, hauls were randomly allocated among all pos-

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Trawl warp 20 mm. Able to fish at a maximum 2000 m depthCodend mesh size 35 mm

maximum penetration of 200 ms Two-Way Travel Time (TWTT,f approx. 200 m below the sea floor).

.2. Benthos

Samples of epibenthic fauna collected with the Lofoten typeear were sorted on deck and preserved (70% ethanol or buffered% formaldehyde seawater solution) for further identification andnalysis.

Net collectors were used for sedimentological purposes duringshing cruises. In the laboratory, the granulometrical analysis of

Please cite this article in press as: Portela, J.M., et al., Preliminary descriptiof the Patagonian Shelf. Fish. Res. (2010), doi:10.1016/j.fishres.2010.06.009

he sediment was carried out by dry sorting of the coarse fraction>62 �m) and sedimentation of the fine fraction (<62 �m). The con-ent of organic matter in the sediment was assessed by calcinatinghe sample at 500 ◦C for 24 h, and drying at 100 ◦C for a further 24 h.

able 2haracteristics of depth strata and fishing operations (ATLANTIS 2008).

Depth stratum Depth range, m Surface, nm2

1 <200 11482 201–300 2723 301–400 3814 401–500 5185 501–700 15136 701–1000 19527 1001–1500 20078 <200 13949 201–300 11110 301–400 12111 401–500 7812 501–1000 93313 1001–1500 2507

Total 12,933

able 3haracteristics of depth strata and fishing operations (ATLANTIS 2009).

Depth stratum Depth range, m Surface, nm2

1 <200 11442 201–300 2793 301–400 3664 401–500 5385 501–700 14836 701–1000 19647 1001–1500 20378 <200 13959 201–300 11110 301–400 12311 401–500 7412 501–1000 97713 1001–1500 2547

Total 13,038

PRESSarch xxx (2010) xxx–xxx 3

2.3. Hydrography

A Sea-Bird Electronics (SBE) CTD Seabird 25, equipped withoximeter, fluorometer and PAR detector was systematicallydeployed at catch-points when depth was less than 500 m, but notalways when depth exceeded 500 m, due to vessel availability andthe time needed for deployment of CTD at such depths.

2.4. Fishing for biomass and abundance estimates

The two cruises used a stratified random design with stratumboundaries defined by latitude and depth ranges. Scheduled fishingstations (hauls of 30 min) were performed using a LOFOTEN-typenet fitted with a “Rockhopper” mix train with bobbins and rubberseparators, suitable for deep-water fishing over irregular bottoms.Table 1 summarizes the main characteristics of the fishing gear.The positions of the hauls were randomly chosen prior to surveyingeach stratum.

Thirteen depth strata were defined in the study area furthersubdivided into 2571 grids of around 5 nm2. Finally, hauls wererandomly allocated according to the following criteria:

- The number of hauls in each stratum was proportional to its sur-face area, with a minimum of two hauls per stratum.

on of the overlap between squid fisheries and VMEs on the high seas

sible grids, excluding those in adjacent squares.- When fishing was not possible in a selected grid due to bottom

characteristics, the haul was moved to the nearest square allow-ing bottom trawling.

No. of grids ∼5 nm2 Hauls performed

Valid Null

219 1251 471 3

119 7318 18349 20 3435 2 5254 15

24 221 226 2

170 12515 26 5

2571 125 13

No. of grids ∼5 nm2 Hauls performed

Valid Null

229 1356 373 4 1

108 6297 17 2393 21 1407 – –279 18 1

22 225 215 2

195 11509 28

2608 127 5

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In total, 147 and 149 hauls respectively were scheduled forruises carried out in 2008 and 2009 (Tables 2 and 3), of whichnly 138 and 132 respectively were accomplished in each cruises characteristics of the seafloor hindered bottom trawling, mainlyn stratum 7 (1001–1500 m depth). It is important to note that noauls were performed in this stratum during the cruise carried out

n 2009 (Table 3), due to the absence of suitable areas for bottomrawling, as observed in ATLANTIS 2008.

As can be seen in Tables 2 and 3, the total surface of the studyrea was slightly increased in 2009 (12,933 and 13,038 nm2 in 2008nd 2009, respectively). The cartographic data obtained during thereceding cruises enabled the updating of the bathymetry and theew data were incorporated to the previous sampling scheduleesigned using the GEBCO software.

Fig. 2 shows the location of the hauls made by depth stratumuring cruises ATLANTIS 2008 and ATLANTIS 2009, marked as validr null hauls.

Survey abundance and biomass indices were calculated using awept area model, i.e. a constant wing spread is used and multipliedy constant tow speed. The towing time was normally 30′ at a meanpeed of 3.05 knots (mean tow distance 1.52 nm). Hauls whicheceived net damage or with a tow duration of less than 20 min,ere excluded from analysis. Stratified abundance and biomass

stimates were calculated from catch-per-tow data using the stra-um area as weighting factor. The method to calculate the stratifiedalues is described by Saville (1977) and the equations used for esti-ation of abundance and biomass indices by tow (j) j = 1, . . ., N and

y stratum (i) i = 1, . . ., H were:

wept Areai =ni∑

j=1

Swept Areaj

Please cite this article in press as: Portela, J.M., et al., Preliminary descriptiof the Patagonian Shelf. Fish. Res. (2010), doi:10.1016/j.fishres.2010.06.009

Wi =ni∑

j=1

CWi,j, where CW is catch in weight

Fig. 2. Location of fishing operations by dept

PRESSarch xxx (2010) xxx–xxx

Biomassi = Surfacei × CWi

Swept Areai, i = 1, . . . , H

CNi =ni∑

j=1

CNi,j, where CN is catch in number

Abundancei = Surfacei × CNi

Swept Areai, i = 1, . . . , H

Biomass and abundance indices for the whole area, where H isnumber of stratum, are:

Biomass =H∑

i=1

Biomassi

Abundance =H∑

i=1

Abundancei

Besides its fishing objective, the LOFOTEN bottom trawl was alsoused as a benthic sampler, complementary to the more specificmega box-corer and rock dredge used in the other cruises with nofishing objectives.

3. Results

3.1. Geomorphology and hydrography

on of the overlap between squid fisheries and VMEs on the high seas

Sediment samples gathered with net collectors were dominatedby fine sands, with low contents of organic matter and sedimentsorting varying from poor to moderately good. The most relevantgeomorphological and geophysical results were:

h stratum (ATLANTIS 2008 and 2009).

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versally crossing the continental rise.

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Fig. 3. Submarine canyons trans

The outer shelf is dominated by sediment ridges aligned in aNNE–SSW direction, oblique to the shelf’s edge.The middle slope surveyed is cut through by 7 entrenched sub-marine canyons (Fig. 3).Scattered over the studied area, south of 45◦S, we found pock-marks, carbonate mounds formed by deep-water corals, andnorth trending furrows.

Areas of smooth topography and sediment waves were foundndicating that deposition on this segment of the middle slope isontrolled by bottom currents.

The CTD data obtained in the two cruises (2008 and 2009),howed no significant differences in the sea temperature (Fig. 4),onsistent with the analysis of remotely sensed sea surface temper-tures (SST) data in the area (Nigmatullin, pers. comm. September009).

.2. Benthos

In terms of biomass and diversity, the phyla Porifera andnidaria were dominant in the benthic megafauna catch (Fig. 5). A

arge part of the organisms considered as vulnerable by the UN andSPAR standards belong to these phyla, such as erect sponges, octo-orals, colonial scleractinian corals, calcified antipatharians andydrozoans (Stylasteridae).

Negligible catch rates of vulnerable organisms and low abun-ances of benthic biomass were found in shallower depth strata<400 m): the organisms considered vulnerable were practicallyegligible in strata 1 and 8 (<200 m), 2 and 9 (201–300 m) and 3nd 10 (301–400 m). Strata 2, 9, 3 and 10 had a low catch of benthiciomass, and also a predominance of detritivorous and opportunis-ic species was observed in strata 2 and 9.

Strata 4, 11, 5, 6 and 12 in intermediate depths (401–1000 m)howed a substantial increase in the number and biomass ofctocorals, sponges, colonial scleractinian corals (Bathelia candida)nd large hydrocorals compared with 2008. Octocorals includedolonies of various genera belonging to families Primnoidae andsididae.

Strata 7 and 13 (1001–1500 m) turned out to be the most prob-ematic for trawling due to seafloor characteristics. In those strata,higher proportion of benthopelagic crustaceans was observed.

Please cite this article in press as: Portela, J.M., et al., Preliminary description of the overlap between squid fisheries and VMEs on the high seasof the Patagonian Shelf. Fish. Res. (2010), doi:10.1016/j.fishres.2010.06.009

Tables 4–7 present details of the catch in number of individu-ls, weight, abundance, biomass, mean abundance per haul (MAH),ean catch per haul (MCH), abundance per unit effort (APUE) and

atch per unit effort (CPUE) for Illex argentinus and Loligo gahi in the008 and 2009 cruises.

Fig. 4. Sea temperature at 10 and 200 m depth during ATLANTIS 2008 and 2009cruises.

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Fig. 5. Geomorphological features and l

.3. Fishing for biomass and abundance estimates

.3.1. Illex argentinusDuring both cruises, biomass and abundance estimations were

Please cite this article in press as: Portela, J.M., et al., Preliminary descriptiof the Patagonian Shelf. Fish. Res. (2010), doi:10.1016/j.fishres.2010.06.009

ade by using the swept area method. In the 2008 cruise, shortfinquid were found to be the second most abundant of all speciesaught, with a total estimated biomass of 45,073 t and a MCH of3.9 kg (Table 4). Catches of this species were obtained throughoutll depth strata with the exception of stratum 13 (1001–1500 m).

able 4atch, abundance and biomass indices of shortfin squid (Illex argentinus) by depth strata

Stratum Surface, nm2 Catch, n Catch, kg Abundance × 1000

1 1148 16,559 1074.7 136,6372 272 3233 1032.8 17,3713 381 4663 609.1 49,3524 518 7138 3201 43,0595 1513 122 61.9 8256 1952 2 0.5 167 2007 – – –8 1394 975 207.9 73939 111 200 50.8 897

10 121 971 413.9 505411 78 26 10.1 8512 933 156 74.9 101313 2507 0 0 0

AH: mean abundance per haul, MCH: mean catch per haul, APUE: abundance per unit e

ns of vulnerable or sensitive organisms.

The highest yields corresponded to strata 4, 2, 10, and 3 with 915,516, 414 and 406 kg/h, respectively.

In 2009 a sharp decrease was observed in the estimated biomass(Table 5), reaching 22,149 t, less than half that obtained in 2008.

on of the overlap between squid fisheries and VMEs on the high seas

MCH was also reduced to 24.4 kg/haul.Distribution pattern of catches by depth strata was different to

that in the previous year with the exception of depth stratum 13,which, similarly to 2008 was the only one with no catches recordedfor this species. Maximum yields in order of decreasing impor-

(ATLANTIS 2008).

Biomass, t MAH, n MCH, kg APUE, n/h CPUE, kg/h

8868 1379.9 89.6 2760 179.15549 808.3 258.2 1617 516.46446 1554.4 203.0 3109 406.1

19,309 1019.8 457.3 2040 914.6419 6.8 3.4 14.0 6.9

4 0.1 0 0.2 0.1– – – – –

1577 65 13.9 130 27.7228 100 25.4 200 50.8

2154 485.6 207 971 413.933 13 5 26 10.1

487 13 6.2 26 12.50 0 0 0 0

ffort and CPUE: catch per unit effort.

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Table 5Catch, abundance and biomass indices of shortfin squid (Illex argentinus) by depth strata (ATLANTIS 2009).

Stratum Surface, nm2 Catch, n Catch, kg Abundance × 1000 Biomass, t MAH, n MCH, kg APUE, n/h CPUE, kg/h

1 1144 5010 1401.4 37,463 10,478 385 107.8 771 215.62 279 1255 415.0 9729 3216 418 138.3 837 276.73 366 224 82.5 1777 655 56 20.6 112 41.34 538 114 49.4 879 381 19 8.2 38 16.55 1483 24 11.6 183 88 1 0.7 3 1.46 1964 0 0.4 0 3 0 0 0 07 2037 – – – – – – –8 1395 4072 938.1 27,145 6254 226 52.1 452 104.29 111 329 124.7 1524 577 165 62.4 329 124.7

10 123 78 26.4 413 139 39 13 78 26.411 74 6 3.0 21 11 3 1 6 3.012 977 104 45.1 798 347 9 4.1 19 8.213 2547 0 0 0 0 0 0 0 0

MAH: mean abundance per haul, MCH: mean catch per haul, APUE: abundance per unit effort and CPUE: catch per unit effort.

Table 6Catch, abundance and biomass indices of long-fin squid (Loligo gahi) by depth strata (ATLANTIS 2008).

Stratum Surface, nm2 Catch, n Catch, kg Abundance × 1000 Biomass, t MAH, n MCH, kg APUE, n/h CPUE, kg/h

1 1148 11,861 188.0 97,871 1551 988.4 15.7 1977 31.32 272 68 1.9 366 10 17.0 0.5 34 0.93 381 1 0 11 0 0.3 0 1 04 518 0 0 0 0 0 0 0 05 1513 0 0 0 0 0 0 0 06 1952 0 0 0 0 0 0 0 07 2007 – – – – – – – –8 1394 5046 71.1 38,284 540 336.4 4.7 673 9.59 111 27 0.7 122 3 13.6 0.4 27 0.7

10 121 40 0.8 208 4 20 0.4 40 0.811 78 0 0 0 0 0 0 0 0

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12 933 1 0 613 2507 0 0 0

AH: mean abundance per haul, MCH: mean catch per haul, APUE: abundance per

ance (kg/h) were found in strata 2, 1, 9 and 10, while stratum 4as among the strata with the lowest CPUE values (only 16.5 kg/h

ersus 914.6 kg/h in 2008).Fig. 6 shows catch distribution and density maps of shortfin

quid in the ATLANTIS 2008 and 2009 cruises (maximum CPUEs450 and 450 kg/h, respectively). In 2008, the highest densityalues were obtained around latitude 47◦30′S, where hauls withaximum catches were located at about 400 m depth. In 2009, the

ighest density values were distributed more northerly. In 2009aximum catches were obtained for shallower depths in the con-

inental shelf (<200 m).

Please cite this article in press as: Portela, J.M., et al., Preliminary descriptiof the Patagonian Shelf. Fish. Res. (2010), doi:10.1016/j.fishres.2010.06.009

.3.2. Loligo gahiThe Patagonian squid fished on the HS of the SW Atlantic rep-

esents a part of the Falklands (Malvinas) population which haseen displaced northwards upstream with the Falkland-Malvinas

able 7atch, abundance and biomass indices of long-fin squid (Loligo gahi) by depth strata (ATL

Stratum Surface, nm2 Catch, n Catch, kg Abundance × 1000

1 1144 8393 163.9 62,7572 279 222 4.4 17193 366 19 0.4 1514 538 1 0 85 1483 0 0 06 1964 0 0 07 2037 – – –8 1395 5090 85.6 33,9359 111 396 7.2 1832

10 123 0 0 011 74 14 0.1 4912 977 0 0 013 2547 0 0 0

AH: mean abundance per haul, MCH: mean catch per haul, APUE: abundance per unit e

0 0.1 0 0 00 0 0 0 0

ffort and CPUE: catch per unit effort.

Current from its main feeding grounds (Arkhipkin et al., 2006). In2008, the main catches were obtained in stratum 1 and to a lesserextent in stratum 8, both shallower than the 200 m depth con-tour. Total estimated biomass for this species in the study area was2108 t (99% within strata 1 and 8) with a mean catch of 2.1 kg/haul(Table 6).

A slight reduction of the total estimated biomass was observedin 2009 compared with that of the previous year (2108 t in 2008versus 1867 t in 2009). Observed MCH remained the same as in2008 (2.1 kg). Catch by depth strata also followed the same patternas in 2008, with maximum CPUEs in strata 1 and 8. Biomass at less

on of the overlap between squid fisheries and VMEs on the high seas

than 200 m depth represented 96.3% of the estimated biomass forthe whole area (Table 7).

Catch distribution and density maps of Patagonian squid are pre-sented in Fig. 7. During the ATLANTIS 2008 cruise, the main catcheswere obtained around parallel 46◦30′S with maximum density val-

ANTIS 2009).

Biomass, t MAH, n MCH, kg APUE, n/h CPUE, kg/h

1226 646 12.6 1291 25.234 74 1.5 148 2.9

3 5 0 10 00 0 0 0 00 0 0 0 00 0 0 0 0– – – –

571 283 4.8 566 9.533 198 3.6 396 7.2

0 0 0 0 00 7 0 14 00 0 0 0 00 0 0 0 0

ffort and CPUE: catch per unit effort.

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Fig. 6. Distribution of catches and density maps of shortfin squid (Illex argentinus) during the ATLANTIS 2008 and 2009 cruises (note the different scale for CPUE in bothyears).

F uring

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ig. 7. Distribution of catches and density maps of Patagonian squid (Loligo gahi) d

es in waters shallower than the 200 m depth contour. During the

Please cite this article in press as: Portela, J.M., et al., Preliminary descriptiof the Patagonian Shelf. Fish. Res. (2010), doi:10.1016/j.fishres.2010.06.009

TLANTIS 2009 cruise, the highest densities of this species wereust over as large as half of those in the previous year (108 kg/hn 2008 versus 60 kg/h in 2009), although the distribution patternf the catches and densities were similar for both cruises (aroundarallels 46◦ and 47◦S).

cruises ATLANTIS 2008 and 2009 (note the different scale for CPUE in both years).

4. Discussion

on of the overlap between squid fisheries and VMEs on the high seas

The outer shelf is dominated by sediment ridges aligned in aNNE–SSW direction, while the middle shelf is covered by mud.The most important geomorphological feature in the middle slopeis the presence of 7 entrenched submarine canyons. Pockmarks,

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nd other seismic and morphologic evidences of gas/fluids seep-ge, were pervasive throughout the entire surveyed area, withore intensity in the southern middle part. The association of gas

eepage with deep-water corals led Sumida et al. (2004) to reporthat deep-water coral communities were found in association withockmarks off Brazil. If such an association also occurs on the Patag-nian margin, those communities may be quite extensive in ourtudy area. Sediments were dominated by fine sands, with lowontents of organic matter.

The hydrological studies concluded that the water of the stud-ed zone is characterised by the mixing of the subantarctic watersflowing northward) with those coming from the continentalischarges along the coast. CTD analysis showed no significantifference in the temperature of the water column between botharine expeditions.The study of benthic deep communities in the area revealed the

xistence of a highly diverse fauna, with dominance of the phylaorifera and Cnidaria, in terms of biomass and diversity. In shal-ower depth strata (less than 400 m) the presence of vulnerablerganisms was low or negligible, while the highest marine ben-hic biodiversity was found in depths ranging from around 800 to500 m. The biodiversity (standardized for total abundance) andotal abundance were both higher along the continental margins,ompared to those found along the continental shelves.

Regarding the abundance and distribution of cephalopodpecies, Argentine shortfin squid was found to be the more abun-ant of the two species, mainly distributed up to a depth of 400 m.bundance of short living species such Illex argentinus are veryependent on oceanographic conditions, but the a marked differ-nce in biomass between cruises, could not be explained by anyifferences in water temperature. According to fishery statistics ofhe Argentinean Agriculture, Livestock, Fisheries and Food Secre-ariat (Anon, 2009), commercial catches of this species reported byhe fishing sector for the first fishing season in 2009 confirmed the

arked reduction of biomass and of the catches observed duringhe ATLANTIS 2009 survey.

Loligo gahi occurs mainly further south, e.g. in Falklands (Malv-nas) waters. Yields of this species in the HS are very low comparedo those obtained within its main distribution area. Major concen-rations of Patagonian squid were found on the shelf, up to depthsf 200 m. In the Falklands (Malvinas), this species normally spawnsn shallow waters (20–50 m), while juveniles move offshore to feedn waters of 200–350 m depth (Arkhipkin et al., 2004).

. Conclusions

Regarding VMEs, the presence of seven submarine canyons wasbserved in the middle slope. Carbonate mounds formed by deep-ater corals were found scattered over the studied area.

The presence of organisms considered vulnerable by the UN andSPAR standards was low or negligible at depths lower than 400 m,here the majority of bottom trawling activities take place.

Nonetheless, some scattered areas within the continental shelf,ith the presence of rocky outcrops and carbonate mounds formed

y deep-water corals, were observed, as well as catches of vulner-ble organisms belonging to the order Alcyonacea (soft corals) andlasses Demospongiae and Hydrozoa. These species, considered asignificant in this study, were found on north easternmost partf the shelf, outside of the Argentinean EEZ. All of these could beecommended as marine protected areas (MPAs).

Please cite this article in press as: Portela, J.M., et al., Preliminary descriptiof the Patagonian Shelf. Fish. Res. (2010), doi:10.1016/j.fishres.2010.06.009

Current fishing activities aiming to catch cephalopod species onhe HS of the Patagonian Shelf probably have a small adverse impactn VMEs.

Considering the UN and FAO recommendations and thereliminary nature of these results and conclusions, more mul-

PRESSarch xxx (2010) xxx–xxx 9

tidisciplinary research effort is needed to reach a comprehensiveunderstanding of the biological, oceanographic, geomorphologicaland ecological features and interactions of the area.

Acknowledgements

Our great acknowledgement to the members of the AtlantisGroup, J. Acosta, S. Parra, J. Cristobo, A. Munoz, P. Ríos, B. Almón,E. Elvira, P. Jiménez, A. Fontán, C. Alcalá and V. López, for theircontribution to the geomorphological, hydrographical and benthicsections of this paper. We wish to thank the ship’s crew, led byits captain, for their professionalism and the courtesy extendedtowards us during the research cruises. We also wish to expressour gratitude to all the people involved in the five research sur-veys, namely the scientific and technical personnel who made thiswork possible. Guest editor Dr. João Pereira and the anonymousreferees provided helpful comments on the draft, for which we arevery grateful.

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