Survey Results for Spain: from the Alboran Sea
to the Catalan Sea
by Maria Gonzalez and Luis Gil de Sola
A total
of 94 hauls were carried out in May 1998 with the R/V «Cornide de Saavedra», 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/km²) 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/km²) 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/km²). 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.
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/km² and 6325 N/km²) 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.
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/km², 1134 N/km²) and between 50-100 m in the Alicante area
(171.3 kg/km², 3835 N/km²). The modal class was found between 15-17 cm.
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/km², 8989 N/km²), Alicante area (25.9 kg/km², 5251 N/km²) and the
Catalan sea (18.5 kg/km², 3920 ind/km). Its abundance decreased from year to
year. Modal class: 5 cm.
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.
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/km² and 4656 N/km² between
50-100 m. Modal class was 11 cm.
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/km².
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/km² and 2344 N/km². The sizes ranged
from 11 cm to 62 cm.
This
species was captured only deeper than 100 m. The highest biomass index was
found in the Alboran Sea: 41.7 kg/km² between 500-800 m and 9.5 kg/km² between
100-200 m. However, the density was greater in the stratum 100-200 (398 N/km²)
than in the stratum 500-800 m (174 N/km²) 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.
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/km²
in the Alboran sea (stratum 50-100 m) and 37.6 kg/km² in the Catalan sea
(stratum 100-200 m).
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/km² in
the Alboran sea between 100-200 m.
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/km². 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/km².
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/km² and 2029 N/km²
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).
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/km²
and 1287 N/km². 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.
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/km² in the stratum 100-200 m)
than in the Catalan sea (4.3 kg/km² in the 50-100 m stratum).
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/km² in the first stratum, 137.2 kg/km² in the stratum
100-200 m. In the Alicante zone and Catalan sea the biomass index was down to
30 kg/km² 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.
It was
relatively abundant in the Alboran sea at depths of between 100-200 m (87.8
kg/km², 1396 N/km²) and less so in the other areas. No large specimens were
caught. The length distribution ranged from 10 to 27 cm.
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/km² in
the first stratum and 9.10 kg/km² in the second one.
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/km² between 500-800 m.
The
highest catches were made in the stratum A in the Alicante area: 53.3 kg/km²
and 5815 N/km².
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/km² between 100-200 m and
31.4 kg/km² between 200-500 m.
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/km².
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/km². The length ranged from 10 to 23 cm. The
modal class was 11-12 cm.
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/km²)
and in the Catalan sea (35.9 kg/km²). 87% of the individuals caught were
juveniles, and the modal class was 14-15 cm. Several adult individuals
were caught near the coast.
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/km² in the Alicante sector and 28.4 kg/km² in the Alboran sea in the 3rd
and 4th stratum, respectively. However, the highest density indexes were 2187
N/km² in the 50-100 m stratum and 1615 N/km² 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.
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/km² and 1492 N/km² between 100-200 m depth.
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/km² and 443 N/km² in the Alboran
sea and 7.4 kg/km² and 555 N/km² in the Alicante area. The sizes ranged from 17
to 62 mm (Carapace Length).
Geryon longipes was the crustacean species with the highest
biomass. It was captured in deep waters: 23.0 kg/km² in the Alboran sea and
25.3 kg/km² in the Alicante waters deeper than 500 m.
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/km² in all strata, except for the stratum 200-500 m in the Alicante
sea (11.7 kg/km² and 425 N/km²). The modal class was 34-36 mm CL.
Its
catch was only important in the Alboran sea on the continental shelf and slope.
High numbers (1523 N/km²) were found between 100-200 m in this region. The size
increased with depth.
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/km² in the first
stratum and 2019 N/km² in the second one.
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/km² in the second stratum in the Alboran sea, 71.9 kg/km² between
100-200 m in the Catalan sea. The catch of juveniles (recruitment) was very
important.
The
biomass indices for this coastal species never exceeded 3 kg/km² in the total
area. It was more abundant between 30-100 m.
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/km² and 19.6 kg/km²
respectively. The highest density value was recorded in the stratum 50-100 m in
the Alboran sea: 1220 N/km².
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.
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.
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/km² |
N/km² |
kg/km² |
N/km² |
kg/km² |
N/km² |
|
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 |
|
|
Alboran |
Alicante |
Catalan |
|||
|
|
kg/km² |
N/km² |
kg/km² |
N/km² |
kg/km² |
N/km² |
|
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.
|
|
Alboran |
Alicante |
Catalan |
|||
|
|
kg/km² |
N/km² |
kg/km² |
N/km² |
kg/km² |
N/km² |
|
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/km² in the Catalan sea), Munida
iris (9094 N/km² in the Catalan sea) and Capros aper (8989 N/km² in the Alboran sea) were the most notable
species. In biomass they were Merluccius
merluccius (94.1 kg/km² in the Catalan sea), Pagellus bogaraveo (87.8 kg/km² in the Alboran sea) and Scyliorhinus canicula (67.3 kg/km² in
the Alboran sea). Like in other years, the survey coincided with the main
period of hake recruitment.
|
|
Alboran |
Alicante |
Catalan |
||||
|
|
kg/km² |
N/km² |
kg/km² |
N/km² |
kg/km² |
N/km² |
|
|
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/km² in Alboran, 18.5 kg/km² in Alicante sector), Scyliorhinus canicula (31.4 kg/km² in
Alboran) and Trachurus trachurus
(34.7 kg/km² in Alicante). In number, Phycis
blennoides (2178 N/km² in the Alboran sea) and Parapenaeus longirostris (551 N/km² in Alboran as well). In general,
the catches in this stratum were lower than in the other strata.
|
|
Alboran |
Alicante |
Catalan |
|||
|
|
kg/km² |
N/km² |
kg/km² |
N/km² |
kg/km² |
N/km² |
|
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/km² in the Alboran sea), Lampanyctus crocodilus (60.8 kg /km² in Alicante) and Nezumia aequalis (49.8 kg/km² in
Alboran). In number, they were Lampanyctus
crocodilus (6175 N/km² in Alicante), Galeus
melastomus (2344 N/km² in Alboran) and Nezumia
aequalis (1822 N/km² in Alboran).