Survey Results for Spain: from the Alboran Sea to the Catalan Sea
by Maria Gonzalez and Luis Gil de Sola

1.     Introduction

A total of 94 hauls were carried out in May 1998 with the R/V ŦCornide de Saavedraŧ, of which 92 were valid. A total of 361 species were identified: 144 fishes, 80 crustaceans, 72 molluscs among which 24 were cephalopods, 40 echinoderms and 25 other invertebrate species. Fishes represented 67.7% of the total weight, crustaceans 6.9%, cephalopods 7.8%, other molluscs 2.7%, echinoderms 10.7% and other invertebrates 4.2%. In number, fishes represented 22.2% of the total catch, crustaceans 34.8%, cephalopods 1.8%, other molluscs 2.3%, echinoderms 36.9% and other invertebrates 2.0%. Leptometra phalangium is the species which caused the high proportion in number of echinoderms.

The most frequent species in the total of hauls (in terms of presence/absence) were (in decreasing order) Merluccius merluccius (it appeared in 69% of the hauls), Eledone cirrhosa, Alloteuthis media, Phycis blennoides, Liocarcinus depurator, Trachurus trachurus, Conger conger, Boops boops, Lophius budegassa, Mullus barbatus and Helicolenus dactylopterus, which were present in more than 40% of the hauls.

In the Alboran Sea, the species of the reference list which presented a high biomass index (more than 15 kg/kmē) were (in decreasing order) Pagellus acarne, Phycis blennoides, Helicolenus dactylopterus, Octopus vulgaris and Eledone cirrhosa. The species with the highest densities (more than 200 N/kmē) were Phycis blennoides, Pagellus acarne, Parapenaeus longirostris and Illex coindetii. Eutrigla gurnardus. Lepidorhombus boscii and Raja clavata were not caught.

Biomass and density indices in the Alicante area were very low in general. In the Catalan Sea, Merluccius merluccius, Eledone cirrhosa, Mullus barbatus and Trachurus mediterraneus were the most abundant species and Merluccius merluccius, Trachurus trachurus, Trisopterus minutus capelanus, and Pagellus acarne have the biggest index of density (more than 500 N/kmē). Raja clavata, Solea vulgaris and Loligo vulgaris were not caught in the Alicante area and Solea vulgaris and Aristeus antennatus were not caught in the Catalan Sea. Aristaeomorpha foliacea was not caught in the total area.

2.     Global comments for Fish, Crustaceans and Cephalopods

2.1     Fish

2.1.1     Argentina sphyraena

This species was irregularly caught on the survey. The catches were very scarce in the Alboran sea and in the Alicante area, but it presented high biomass and density indices (74.0 kg/kmē and 6325 N/kmē) on the shelf of the Catalan sea. Argentina sphyraena is a gregarious species, locally abundant. A very high number of them was caught in two hauls. The sizes ranged between 9 and 17 cm. Modal class was 12 cm.

2.1.2     Boops boops

Boops boops was captured on the continental shelf. The highest biomass and density indices were observed in the coastal stratum in the Alboran sea (95.4 kg/kmē, 1134 N/kmē) and between 50-100 m in the Alicante area (171.3 kg/kmē, 3835 N/kmē). The modal class was found between 15-17 cm.

2.1.3     Capros aper

This species was generally fished at depths less than 500 m, with a maximum of its biomass and density indices in the stratum 100-200 m in the three sectors: Alboran sea (26.9 kg/kmē, 8989 N/kmē), Alicante area (25.9 kg/kmē, 5251 N/kmē) and the Catalan sea (18.5 kg/kmē, 3920 ind/km). Its abundance decreased from year to year. Modal class: 5 cm.

2.1.4     Citharus linguatula

This species was observed up to 200 m depth in the three sectors. Catches were very low and mainly composed of juvenile individuals: 70.9% of them were smaller than 16 cm of length.

2.1.5     Engraulis encrasicolus

This pelagic species lives near the bottom during the day on the continental shelf. It was occasionally caught in the Catalan Sea, but the yield was high because of its gregarious behaviour. Highest biomass and density indices were found in the 3rd sector (Catalan Sea): 47.8 kg/kmē and 4656 N/kmē between 50-100 m. Modal class was 11 cm.

2.1.6     Eutrigla gurnardus

Absent from the samples made on the Alboran Sea, Eutrigla gurnardus appeared sporadically in the coastal shelf. Biomass index was low, of the order of 1 kg/kmē.

2.1.7     Galeus melastomus

Its abundance was more important in the Alboran sea, like other slope species: Etmopterus spinax, trachyrhynchus trachyrhynchus, Nezumia aequalis, Phycis blennoides. In this region it showed between 500-800 m a biomass and density indices of 363.9 kg/kmē and 2344 N/kmē. The sizes ranged from 11 cm to 62 cm.

2.1.8     Helicolenus dactylopterus

This species was captured only deeper than 100 m. The highest biomass index was found in the Alboran Sea: 41.7 kg/kmē between 500-800 m and 9.5 kg/kmē between 100-200 m. However, the density was greater in the stratum 100-200 (398 N/kmē) than in the stratum 500-800 m (174 N/kmē) because sizes increased with depth. 72.0% of the individuals were juveniles, with a length below 18 cm. The length distribution showed two modal classes, the first one at 4 cm and the second one at 24 cm.

2.1.9     Lophius budegassa

The catch values of this species were more important in weight that in number. It appeared in 42.5% of the hauls. The lengths ranged from 6 to 66 cm and a clear modal class did not appear. The highest biomass indices were 37.6 kg/kmē in the Alboran sea (stratum 50-100 m) and 37.6 kg/kmē in the Catalan sea (stratum 100-200 m).

2.1.10     Lophius piscatorius

This species presented very low catches (10 individuals in the survey). It appeared between 50-200 m and the greatest value of the biomass index was 11.2 kg/kmē in the Alboran sea between 100-200 m.

2.1.11     Merluccius merluccius

Merluccius merluccius was caught in 65% of the hauls of the Medits-ES 98 survey. It presented a wide distribution over the whole studied area. In the Alboran sea it appeared in all strata, and the largest catch in biomass occurred in the shallowest stratum: 52.0 kg/kmē. In the other areas this species was caught down to 500 m depth, being more abundant in the Catalan sea from 100 to 200 m: 94.1 kg/kmē.

2.1.12     Micromesistius poutassou

Micromesistius poutassou was observed at depths below 100 m in all sectors. The highest biomass and density indices were reported between 100 and 200 m in the Catalan sea with values of 44.6 kg/kmē and 2029 N/kmē respectively. However, the catches presented a high variability due to its condition of mesopelagic species that constitutes important shoals and makes daily migrations. Most of the individuals captured were juveniles (77% under 17 cm length).

2.1.13     Mullus barbatus

Species of the shelf, it was fished down to 200 m. General biomass indexes increased from the Alboran sea to Catalan sea. By stratum, the highest biomass and density indices were found in the Catalan sea between 100-200 m: 49.5 kg/kmē and 1287 N/kmē. The lengths of the captured individuals were comprised between 10-24 cm. The modal class was 13 cm, and most of the individuals fished exceeded the length of first maturity.

2.1.14     Mullus surmuletus

In general, its distribution was similar to Mullus barbatus, but its catches between 10-50 m were very low. Contrary to the previous species, M. surmuletus had a higher biomass index in the Alboran sea (30.3 kg/kmē in the stratum 100-200 m) than in the Catalan sea (4.3 kg/kmē in the 50-100 m stratum).

2.1.15     Pagellus acarne

This species presented important catches in the three shallowest strata in the Alboran sea and up to 100 m in the other two sectors. Pagellus acarne showed very high biomass and density indices in the Alboran sea: 945.2 kg/kmē in the first stratum, 137.2 kg/kmē in the stratum 100-200 m. In the Alicante zone and Catalan sea the biomass index was down to 30 kg/kmē in all strata. The length frequencies showed that the majority of fish were mature: 82.8 % of the individuals were larger than 15 cm length (size of first maturity). The mean length was 21 cm.

2.1.16     Pagellus bogaraveo

It was relatively abundant in the Alboran sea at depths of between 100-200 m (87.8 kg/kmē, 1396 N/kmē) and less so in the other areas. No large specimens were caught. The length distribution ranged from 10 to 27 cm.

2.1.17     Pagellus erythrinus

Pagellus erythrinus was caught in limited number down to 100 m depth with a relatively high biomass index in the Catalan sea: 9.79 kg/kmē in the first stratum and 9.10 kg/kmē in the second one.

2.1.18     Phycis blennoides

Phycis blennoides was distributed on the shelf and the upper slope. The juveniles appeared between 100-800 m, but the adults only were present in the slope. The population showed two cohorts with a modal class in 7-9 cm and 22-25 cm. As in the majority of slope species, the catch of Phycis blennoides was greatest in the Alboran sea: 45.0 kg/kmē between 500-800 m.

2.1.19     Sardina pilchardus

The highest catches were made in the stratum A in the Alicante area: 53.3 kg/kmē and 5815 N/kmē.

2.1.20     Scyliorhinus canicula

Scyliorhinus canicula showed a wide bathymetric distribution in the Alboran sea, where it appeared in all strata. The highest biomass indices were 67.3 kg/kmē between 100-200 m and 31.4 kg/kmē between 200-500 m.

2.1.21     Solea vulgaris

Only four specimens were caught in the survey, all of them in the Alboran sea down to 50 m depth. The biomass index for this stratum was 36.0 kg/kmē.

2.1.22     Spicara flexuosa

This species was found in shallow waters (10-100 m) in all sectors. The biomass index was particularly high in the Alboran sea, especially in the stratum 10-50 m with values of 46.2 kg/kmē. The length ranged from 10 to 23 cm. The modal class was 11-12 cm.

2.1.23     Trachurus mediterraneus

This coastal species had a very low abundance in the Alboran sea. The most important catches were made between 50 and 100 m depth in the Alicante area (55.8 kg/kmē) and in the Catalan sea (35.9 kg/kmē). 87% of the individuals caught were juveniles, and the modal class was 14-15 cm. Several adult individuals were caught near the coast.

2.1.24     Trachurus trachurus

The bathymetric distribution of Trachurus trachurus was wider than that of Trachurus mediterraneus. It reached the upper slope. The highest biomass index were 34.7 kg/kmē in the Alicante sector and 28.4 kg/kmē in the Alboran sea in the 3rd and 4th stratum, respectively. However, the highest density indexes were 2187 N/kmē in the 50-100 m stratum and 1615 N/kmē between 100-200 m in the Catalan sea, since the catch of small individuals in this sector was very high. The adults were caught in the deepest stratum of its distribution. Two modal classes were apparent: 8 cm (juveniles) in the shelf and 19-20 cm (adults) in the upper slope.

2.1.25     Trisopterus minutus capelanus

This species presented two cohorts, the first one with one modal class in 7-8 cm length (juveniles) and the second one with a modal class in 15-16 cm (adults). The juveniles were more abundant and they appeared in the same strata that the adults. Trisopterus minutus capelanus increased its biomass and density indices from the Alboran sea to the Catalan sea. In this last region the highest values were 18.9 kg/kmē and 1492 N/kmē between 100-200 m depth.

2.2     Crustaceans

2.2.1     Aristeus antennatus

Aristeus antennatus was caught in the three areas between 500-800 m depth. Biomass and density indices of the Catalan sea are not correct because only one haul was performed in this area in this stratum. In the other areas the species appeared in fair numbers: 5.1 kg/kmē and 443 N/kmē in the Alboran sea and 7.4 kg/kmē and 555 N/kmē in the Alicante area. The sizes ranged from 17 to 62 mm (Carapace Length).

2.2.2     Geryon longipes

Geryon longipes was the crustacean species with the highest biomass. It was captured in deep waters: 23.0 kg/kmē in the Alboran sea and 25.3 kg/kmē in the Alicante waters deeper than 500 m.

2.2.3     Nephrops norvegicus

Nephrops norvegicus was found on the slope deeper than 200 m. Biomass and density indices of this species were very low in this survey, of around 2 kg/kmē in all strata, except for the stratum 200-500 m in the Alicante sea (11.7 kg/kmē and 425 N/kmē). The modal class was 34-36 mm CL.

2.2.4     Parapenaeus longirostris

Its catch was only important in the Alboran sea on the continental shelf and slope. High numbers (1523 N/kmē) were found between 100-200 m in this region. The size increased with depth.

2.3     Cephalopods

2.3.1     Alloteuthis media

This small cephalopod was captured down to 200 m, but it presented its maximum density values between 10-100 m. Alloteuthis media is a mesopelagic species that constitutes shoals near the bottom. The highest density index was obtained in the Catalan sea: 2302 N/kmē in the first stratum and 2019 N/kmē in the second one.

2.3.2     Eledone cirrhosa

Eledone cirrhosa was widely distributed over the whole area. However, its highest biomass indices were reported on the shelf between 50-200 m: 79.1 kg/kmē in the second stratum in the Alboran sea, 71.9 kg/kmē between 100-200 m in the Catalan sea. The catch of juveniles (recruitment) was very important.

2.3.3     Eledone moschata

The biomass indices for this coastal species never exceeded 3 kg/kmē in the total area. It was more abundant between 30-100 m.

2.3.4     Illex coindetii

This species was generally captured on the shelf and the upper slope. During this survey, the catches were mainly constituted of i mmature individuals with a dorsal mantle length between 5.5 and 10 cm. The juveniles were the more coastal fraction of the population. The highest biomass values were recorded in the second and third stratum in the Alboran sea: 14.0 kg/kmē and 19.6 kg/kmē respectively. The highest density value was recorded in the stratum 50-100 m in the Alboran sea: 1220 N/kmē.

2.3.5     Octopus vulgaris

Octopus vulgaris was only found at depths shallower than 200 m in all sectors, and its greatest abundance occurred shallower than 100 m in the Alboran sea and shallower than 50 m in the other areas. The total abundance value decreased from Alboran sea to Catalan sea. Sizes ranged from 35 to 190 mm (Mantle Length). One modal class was evident at 90 mm.

2.3.6     Sepia officinalis

This coastal species was only caught in the first stratum in the Alicante zone and Catalan sea. In the Alboran sea it was also caught in the second stratum. The catches of Sepia officinalis were low because the bottom trawl gear is not appropriated for its fishing.

3.     Comments by stratum

3.1     Stratum 10-50 m

In this stratum 20 species of the reference list were caught: 14 fishes, 1 crustacean and 5 cephalopods. Three types of catches were evident:

Species with coastal distribution patterns: Octopus vulgaris, Spicara flexuosa, Boops boops.

Species that live in deeper waters but the distribution of its juveniles is more coastal: Pagellus acarne, Merluccius merluccius.

Pelagic species that constitute shoals near the bottom during the day: Engraulis encrasicolus, Sardina pilchardus, Alloteuthis media.

Generally, the abundance indices of the most coastal species decreased from the Alboran sea to the Catalan sea, with the exception of pelagic species, very more abundant in the Catalan sea. The catches of Sepia officinalis and Loligo vulgaris (coastal species) were low because the bottom trawl gear is not appropriated for its fishing.

 

 

Alboran

Alicante

Catalan

 

 kg/kmē

N/kmē

 kg/kmē

N/kmē

 kg/kmē

N/kmē

Alloteuthis media

3.1

1229

4.6

1143

7.2

2302

Boops boops

95.4

1134

0.3

11

3.7

128

Engraulis encrasicolus

-

-

-

-

14.7

1849

Merluccius merluccius

52.0

200

12.2

566

10.2

474

Octopus vulgaris

96.6

137

116.0

133

46.1

49

Pagellus acarne

945.2

6091

2.1

22

24.6

239

Sardina pilchardus

-

-

53.3

5815

21.2

2681

Spicara flexuosa

46.2

924

1.0

33

7.6

325

Trachurus trachurus

7.5

777

0.7

178

0.7

140

 

3.2     Stratum 50-100 m

 

 

Alboran

Alicante

Catalan

 

 kg/kmē

N/kmē

 kg/kmē

N/kmē

 kg/kmē

N/kmē

Alloteuthis media

1.1

447

5.6

1927

5.0

2019

Boops boops

42.3

478

171.3

3835

14.5

365

Eledone cirrhosa

79.1

258

17.0

40

32.8

116

Engraulis encrasicolus

0.04

7

2.0

251

47.8

4656

Merluccius merluccius

9.5

230

22.6

1386

29.0

1898

Octopus vulgaris

79.4

120

14.6

14

0.5

1

Pagellus acarne

86.3

1107

28.2

172

23.7

107

Sardina pilchardus

0.2

17

25.4

4228

35.3

2203

Trachurus mediterraneus

1.9

82

55.8

1880

35.9

941

Trachurus trachurus

4.6

234

3.4

367

12.1

2187

 

A total of 23 different target species were fished in this stratum: 16 fishes, 1 crustacean and 6 cephalopods.

The distribution of the most abundant species coincides with that of the most abundant species in the first stratum: Pagellus acarne, Octopus vulgaris, Merluccius merluccius, Boops boops, Alloteuthis media, Engraulis encrasicolus and Sardina pilchardus. The abundance of juveniles of Trachurus trachurus and Trachurus mediterraneus is important, as well.

3.3     Stratum 100-200 m

 

 

Alboran

Alicante

Catalan

 

 kg/kmē

N/kmē

 kg/kmē

N/kmē

 kg/kmē

N/kmē

Capros aper

26.9

8989

25.9

5251

18.5

3920

Eledone cirrhosa

13.1

112

41.9

164

71.9

345

Lophius budegassa

11.5

27

9.9

25

37.6

47

Merluccius merluccius

5.5

506

20.9

2080

94.1

9828

Mullus barbatus

5.4

81

1.5

29

49.5

1287

Munida iris

1.3

1914

0.4

273

48.7

9094

Pagellus bogaraveo

87.8

1396

-

-

0.4

6

Scyliorhinus canicula

67.3

333

6.7

59

7.9

35

 

26 of the 31 target species were caught in this depth range: 19 fishes, 2 crustaceans and 5 cephalopods.

In this stratum the most abundant species was Leptometra phalangium, a Crinoidea species: 46.87 kg and 117125 individuals in one haul only. In density, Merluccius merluccius (9828 N/kmē in the Catalan sea), Munida iris (9094 N/kmē in the Catalan sea) and Capros aper (8989 N/kmē in the Alboran sea) were the most notable species. In biomass they were Merluccius merluccius (94.1 kg/kmē in the Catalan sea), Pagellus bogaraveo (87.8 kg/kmē in the Alboran sea) and Scyliorhinus canicula (67.3 kg/kmē in the Alboran sea). Like in other years, the survey coincided with the main period of hake recruitment.

3.4     Stratum 200-500 m

 

 

Alboran

Alicante

Catalan

 

 kg/kmē

N/kmē

 kg/kmē

N/kmē

 kg/kmē

N/kmē

 

Parapenaeus longirostris

4.7

551

1.0

79

-

-

 

Phycis blennoides

18.1

2178

18.5

864

-

-

 

Scyliorhinus canicula

31.4

147

8.8

175

-

-

 

Trachurus trachurus

-

-

34.7

561

-

-

 

 

It was not possible to perform all the seven hauls planned in the sampling scheme for the Catalan sea due to technical problems. In the other two sectors, 17 species of the reference list were found: 11 fishes, 3 crustaceans and 3 cephalopods. The most abundant species in biomass were Phycis blennoides (18.1 kg/kmē in Alboran, 18.5 kg/kmē in Alicante sector), Scyliorhinus canicula (31.4 kg/kmē in Alboran) and Trachurus trachurus (34.7 kg/kmē in Alicante). In number, Phycis blennoides (2178 N/kmē in the Alboran sea) and Parapenaeus longirostris (551 N/kmē in Alboran as well). In general, the catches in this stratum were lower than in the other strata.

3.5     Stratum 500-800 m

 

 

Alboran

Alicante

Catalan

 

 kg/kmē

N/kmē

 kg/kmē

N/kmē

 kg/kmē

N/kmē

Aristeus antennatus

5.1

443

7.4

555

-

-

Galeus melastomus

363.9

2344

18.0

164

-

-

Lampanyctus crocodilus

2.8

156

60.8

6175

-

-

Nezumia aequalis

49.8

1822

1.8

95

-

-

Phycis blennoides

45.0

444

10.0

242

-

-

 

Only one haul was carried out in the Catalan sea between 500-800 m. Therefore, the abundance indices of this stratum are not presented. For the other regions, 13 species of the reference list were captured: 8 fishes, 3 crustaceans and 2 cephalopods.

The most important species in biomass were Galeus melastomus (363.9 kg/kmē in the Alboran sea), Lampanyctus crocodilus (60.8 kg /kmē in Alicante) and Nezumia aequalis (49.8 kg/kmē in Alboran). In number, they were Lampanyctus crocodilus (6175 N/kmē in Alicante), Galeus melastomus (2344 N/kmē in Alboran) and Nezumia aequalis (1822 N/kmē in Alboran).