52 
Fishery Bulletin 119(1) 
Cape Creus  , 
Catalan Sea 
Cape Palos 
Figure 1 
Map showing the locations where 7 species of Gadiformes were sampled between 
2011 and 2017 in the Mediterranean Sea off the coast of Spain from Cape Palos 
to Cape Creus, in the geographical subarea 06 (GSA-06) defined by the General 
during daylight, from 0800 to 1800, at 
depths of 40-730 m. 
For this investigation, we selected the 
species of the order Gadiformes that 
were most abundant in the study area: 
the silvery pout, Mediterranean bigeye 
rockling, Mediterranean ling, European 
hake, blue whiting, greater forkbeard, 
and poor cod. During the survey cruises 
in the study period, the contents of 
3192 stomachs were analyzed on board 
vessels (for details for these 7 species, 
see Table 1). After each trawl tow, 10 
RE individuals of each of the studied spe- 
cies were randomly sampled from the 
haul. For all specimens examined, total 
length (TL) in millimeters, sex, and 
maturity stage were recorded according 
to MEDITS guidelines (Bertrand et al., 
2002). Later, diet was assessed quan- 
titatively by measuring the volume of 
stomach contents with a trophome- 
ter, a calibrated device that consists of 
several semicylinders of different sizes 
(Olaso, 1990). The use of this instru- 
ment is helpful on board oceanographic 
vessels because it allows a large num- 
ber of stomachs to be examined in a rel- 
atively short period. 
Once a stomach was opened, its con- 
tents were analyzed under a binocular 
microscope (Leica MZ6”, Leica Microsys- 
tems, Wetzlar, Germany). Prey found in 
stomachs (prey items) were identified 
to the lowest possible taxon by using 
published guides (Zariquiey, 1968; 
Lombarte et al., 2006) and our own ref- 
erence collection. The degrees of diges- 
tion of all prey items identified were 
also noted, as fresh, partially digested, 
or fully digested. The stomachs that 
contained any items presumably con- 
Fisheries Commission for the Mediterranean. Dots indicate the positions of the sumed in the net during fishing opera- 
trawl tows conducted during surveys. The light gray shaded area indicates the tions (i.e., stomachs from individuals of 
area between isobaths of 40 and 800 m where specimens were caught. anglerfish species) were excluded from 
Stomach samples were collected from fish caught during 
bottom-trawl surveys conducted as part of the Mediterra- 
nean International Trawl Survey (MEDITS) program in 
GSA-06 in 2011-2017 (Bertrand et al., 2002). The surveys 
of this program take place yearly from May through June 
for the purpose of evaluating the demersal resources 
throughout the study area. The standard MEDITS sam- 
pling gear is a bottom trawl called the GOC 73, which has 
a net with a mesh size of 40 mm and a codend with a mesh 
size of 20 mm. This gear is specifically designed for exper- 
imental fishing. A total of 604 trawl tows were carried out 
the analyses. The presence of skeletal 
remains and other hard body parts was 
also recorded. Stomach samples from 
specimens that had regurgitated the contents of their 
stomachs were replaced with samples from individuals of 
a similar size class (Garcia-Rodriguez et al., 2020). Fol- 
lowing Robb (1992), the color and size of the gall bladder 
of European hake were used to determine if a specimen 
had an empty stomach or had regurgitated during the 
fishing operation. 
5 Mention of trade names or commercial companies is for identi- 
fication purposes only and does not imply endorsement by the 
National Marine Fisheries Service, NOAA. 
