Illex Coindetii Research Articles

Biology and meso-scale distribution patterns of North Sea cephalopods

Between 2007 and 2009, 132,178 cephalopods were sampled in the North Sea during ICES International Bottom Trawl Surveys. Most abundant were the long-finned squids Alloteuthis subulata (124,751 animals) and Loligo forbesii (3415 animals). Short-finned squids such as Todaropsis eblanae, Todarodes sagittatus and Illex coindetii were rare (195 animals). During winter, A. subulata individuals, mostly immature and maturing, were concentrated in the central and northern parts of the North Sea. In summer, the abundance of A. subulata, mostly maturing and mature, increased in the southeastern part suggesting a southward migration to spawning grounds. L. forbesii individuals, some fully mature, were abundant in the northwestern part of the North Sea during winter indicating spawning areas in this region. In summer, L. forbesii individuals, mostly immature, occurred in lower numbers throughout the North Sea. Our data provide new information on abundance, distribution, migration, and possible recruitment areas of North Sea cephalopods.

The demersal faunal assemblage of the north-western Ionian Sea (central Mediterranean): current knowledge and perspectives

Data reported in this article were collected in the context of several trawl surveys carried out in the north-western Ionian Sea in the last 25 years. An overview of the available information on the demersal resources in the area and an historical analysis at population and community levels is reported with the aim of identifying eventual significant changes over time. During the study period 1985–2006, a total of 365 species (41 cephalopods, 76 crustaceans, 33 chondroichthyes and 215 osteichthyes) were collected in the investigated area from 10 to 4000 m, updating the faunal lists of this area with 18 new records and one alien species for the Mediterranean. An increase in the species richness was observed throughout the study period. The historical analysis showed a low abundance of chondroichthyes and significant increases over time for cephalopods, crustaceans and osteichthyes during the study period 1985–2006. An increasing trend in density over time was also detected for some target species (Illex coindetii and Nephrops norvegicus) and an inverse significant correlation with the fishing effort was also shown. Nevertheless, a significant decrease in the median lengths over time was depicted for N. norvegicus and Parapenaeus longirostris. A decreasing trend in the total mortality (Z) and exploitation rates (E) with time was only observed for Mullus barbatus. An overexploitation condition was shown by P. longirostris and Merluccius merluccius during time while a moderate overexploitation was detected for M. barbatus and Aristaeomorpha foliacea over time. A state of almost equilibrium and an optimal exploitation were observed for N. norvegicus and Aristeus antennatus, respectively. The authors give rise to discussion on the fishing effort-exploitation rate-recruitment process to explain the trends shown in the north-western Ionian Sea.

Selectivity of diamond, hexagonal and square mesh codends for three commercial cephalopods in the Mediterranean

Undersized and immature commercially important cephalopods are often inadvertently caught by trawlers in the eastern Mediterranean. To evaluate the effectiveness of different mesh codends (diamond, hexagonal and square) to reduce bycatch of juvenile commercially important Mediterranean cephalopods (European squid Loligo vulgaris, broadtail shortfin squid Illex coindetii and pink cuttlefish Sepia orbignyana), a series of selectivity experiments was undertaken with a modified bottom trawl. The covered codend technique was used to capture escapees. For the broadtail shortfin squid and the pink cuttlefish, the square-shaped mesh displayed the highest 50% retention lengths ( L 50) compared to diamond and hexagonal mesh. For the European squid, selectivity could only be measured by pooling the data from all hauls for each mesh shape. For all three species, the L 50 values of square and hexagonal mesh codends were significantly different ( p < 0.01). Beyond the mesh variability, species catch was found to have a significant impact in the selection range of the broadtail shortfin squid. Furthermore, for the cuttlefish, total catch and haul duration likely account for variability of L 50 attributed to mesh configuration. For all species, regardless of the mesh shape, L 50 values were substantially lower than the minimum landing size or length at first maturity. Therefore, the current legal minimum mesh size and codend configurations for demersal trawling are not suitable for the management of these species. As such, sustainability in Mediterranean cephalopod fisheries would profit from more selective gears. This could be achieved both by an increase in codend mesh size and change in codend shape; however, being part of a mixed fishery, when these changes are being practiced, the impact on the fish catches of target species will have to be taken into consideration.

Influences of environmental variability on the population structure and distribution patterns of the short-fin squid Illex coindetii (Cephalopoda: Ommastrephidae) in the Eastern Ionian Sea

Illex coindetii is the most common benthic ommastrephid squid exploited by bottom trawl in the Mediterranean Sea. A recent study examining trends in population metrics based on data from the International Bottom Trawl Surveys in the Mediterranean (MEDITS) has shown an increasing trend in average lengths of I. coindetii sampled in the eastern Ionian Sea, suggesting that this is possibly due to the thermoaline circulation reversal and the warming of the entire water column in this area after 1998 because of the Eastern Mediterranean Transient (EMT). In this study, spatial and inter-annual variability of the population structure and the distribution patterns of I. coindetii in the eastern Ionian is investigated in relation to environmental characteristics. Datasets used include demographical and biological data derived from the MEDITS surveys carried out during the summers of 1994–2006 and environmental parameters obtained through CTD sampling and remotely sensed imagery. Analyses performed include descriptive methods like the length frequency analyses and GIS mapping of standardized densities, as well as habitat modelling of presence data for different life stages of I. coindetii (based on generalized additive models and maximum entropy). An increasing trend in frequency of occurrence and density indices for all life stages has been detected during the studied period, being more evident after 1999. At the same time a temporal shift in seasonal maturation was also evidenced, coinciding to the warming of eastern Ionian waters due to EMT effects. Spawning aggregations occurred steadily on the upper slope of the relatively more protected area west of the Kefalonia Island, extending also over the lower shelf of the Patraikos Gulf in summers with lower upwelling activity. The inter-annual variability observed in the location of main recruitment areas could be related to mechanisms affecting post-hatching dispersal during late winter and spring, when maximum intensity of surface mesoscale activity has been observed. Depth was found the principal variable associated with the distribution of I. coindetii in the study area. Anomalies of surface temperature and chlorophyll-a, as well as distances from coast and thermal fronts were also selected for the final set of response variables without, however, showing any clear trend particularly in the case of recruits. The results of this study highlight the importance of a more comprehensive study of both environmental processes and I. coindetii life history in the Ionian Sea, in order to improve the understanding of its dynamics and the links with environmental variability.

Size selection by diamond- and square-mesh codends in multi-species Mediterranean demersal trawl fisheries

Mediterranean demersal trawl fisheries traditionally operate using small diamond-shape meshes in the codend, which tend to retain almost all animals. We investigated the effect of mesh configuration on the size selectivity of nine species (the scaldfish Arnoglossus laterna, the broad-tail shortfin squid Illex coindettii, the European hake Merluccius merluccius, the red mullet Mullus barbatus, the Norway lobster Nephrops norvegicus, the common pandora Pagellus erythrinus, the deepwater rose shrimp Parapenaeus longirostris, the Mediterranean horse mackerel Trachurus mediterraneus and the poor-cod Trisopterus minutus capelanus) commonly captured in the Mediterranean demersal trawls. Two codends having meshes with the same opening (ca. 38 mm) but different mesh configuration (DM38: diamond-mesh and SM38: square-mesh configuration) were fished daily and alternately on the same trawl. They demonstrated a substantial improvement in selectivity with square-mesh. Selectivity was measured using the covered codend technique, the cover being supported by circular hoops. The results were analysed taking into account the between-haul variation in selectivity. Two other important external variables were identified: the trawling depth and the codend catch, which for some species influenced between-haul variation, but there was no evidence of a coherent effect on selectivity parameters. The selectivity of 40 mm diamond-mesh codend has been reported to be rather poor because a large proportion of the codend catch is immature and smaller than the minimum landing size (MLS) or first maturity size. With the exception of the flatfish ( A. laterna), the effect of a change of mesh configuration from diamond- to square-mesh on size selectivity positively affected the retention length at 50% ( L 50). However, square-meshes were found to be unsuitable for flat and/or deep-bodied fish as these escape more readily from diamond-meshes. The Council Regulation (EC) No. 1967/2006, concerning management measures for the sustainable exploitation of fishery resources in the Mediterranean, establishes the MLS of marine organisms. However, the increase in L 50 with square-mesh would not avoid some of the existing contradictions in allowing the use of codend mesh which leads to lower L 50 than the MLS.

Diet of Tetrapturus belone (Istiophoridae) in the central Mediterranean Sea

The stomach contents of 69 Mediterranean spearfish Tetrapturus belone collected in the Strait of Messina, central Mediterranean Sea were examined. Of the total specimens, caught by harpoon, only three stomachs were empty. Their diet consisted mainly of pelagic fish and cephalopods. The most important piscine prey belonged to the families of Belonidae, Clupeidae and Scomberesocidae. Cephalopods were mainly represented by Tremoctopus violaceus in terms of per cent weight and by Illex coindetii in terms of per cent frequency of occurrence. Tetrapturus belone is an active predator on epipelagic fast-moving prey and school-forming species. Its ecological role is similar to that of other large pelagic species which share the same environment.

CEPHALOPOD DISTRIBUTION IN ISKENDERUN BAY (EASTERN MEDITERRANEAN-TURKEY)

Normal 0 false false false EN-US X-NONE X-NONE/* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}This paper is the first comprehensive work on the biology and distribution of cephalopods in the Iskenderun Bay area of Mediterranean Sea. Information on the distribution of Cephalopod fauna was collected through 45 deep-trawl surveys carried out on the commercial trawl fishery waters (between 20 and 200 m) between March 2004 and May 2005. During the study, a total of 1101 individuals belonging to eight species; two cuttlefishes, two squids and four octopods, were recorded. Mean value of dorsal mantle lengths and body weights of the captured species were; 10.74 ± 0.10 cm and 126.42 ±3.24 g for Sepia officinalis, 4.2 cm and 4.68 g for Sepia elegans, 15.3±0.42 cm and 87.68 ±6.35 g for Loligo vulgaris, 10.93 ±0.28 cm and 48.17 ±4.52 g for Illex coindetii, 8.08 ±0.13 cm and 99.17 ±4.01 g for Eledone moschata, 13.5 cm and 281.46 g for Eledone cirrhosa, 10.25±0.45 cm and 370.33 ±53.89 g for Octopus vulgaris, 12.71±0.64 cm and 405.59 ±51.69 g for Octopus macropus. In addition the present study also provides information on dorsal mantle length – body weight relationship and biology of the species found in this particular area.

Sensory, microbiological, physical and chemical properties of cuttlefish ( Sepia officinalis) and broadtail shortfin squid ( Illex coindetii) stored in ice

The objective of this study was to characterize whole raw cuttlefish ( Sepia officinalis) and shortfin squid ( Illex coindetii) during storage in ice through sensory, microbiological, chemical and physical analyses. The recently developed Quality Index Method (QIM) tables for these species were used for sensory analysis. Shelf-life of whole cuttlefish and shortfin squid were estimated as around 10 and 9 days, respectively, according to QIM, which is shorter than for most species, especially fish. The numbers of microorganisms found in cuttlefish and shortfin squid surfaces until rejection were lower than in fish, which suggest predominance of enzymatic (autolytic) degradation. H 2S-producing bacteria constituted a significant proportion of the spoilage flora. Physical analysis performed using the RT-Freshmeter and the Torrymeter showed these instruments can be applied to cuttlefish and shortfin squid, providing useful complementary information on the rates of change of electrical properties. Free tryptophan and VBN contents significantly changed during the first storage week indicating that low levels of these compounds could be used as indicators of fresh and high quality cuttlefish and broadtail shortfin squid. Urea can be useful as spoilage indicator for cuttlefish, as well as agmatine for broadtail shortfin squid. An overall look into data obtained shows, as expected, that spoilage of these cephalopod species can be considered a different phenomena when compared to fish and is not yet completely clarified.

A “Traffic” Light approach for the assessment of the Broadtail shortfin squid Illex coindetii Verany, 1839 in the Southern Adriatic Sea (Central Mediterranean)

A multi-indicator system and the Traffic Light methodology (TL) to provide the first description of the Illex coindetii (Verany 1839) stock in the GFCM geographical sub-area (GSA) 18 (southern Adriatic Sea; Central Mediterranean) were applied using independent fishery data (“Mediterranean Bottom Trawl Survey”, “Medits”, programme, years 1996–2004). The trajectories of nine population indicators of Frequency of Occurrence (F), Biomass (BI), Density (DI), Recruit Strength (RS), Spawner Strength (SS), Mean Body Weight (MBW), Mantle Length (ML), Mantle Length Excluding Recruits fraction (MLER), Mean mantle Length-Females Length at maturity ratio (MLLm), were analysed using statistical estimators as arithmetic and geometric mean, median, and 75th percentile. The TL methodology was applied to analyse the resulting multiple-indicator panel. Results describe a significant trend of the I. coindetii stock (in number) in the GSA 18 related to a shift within its structure due to a greater proportion of small specimens in the population. Factors that may be contributing to the observed changes are sea temperature, the reduction of possible predators, the recovery of some prey species mostly due to the fishing pressure occurring in the area, and the fast growth and short life span of I. coindetii. In a dynamic system like the Adriatic Sea, the capability to respond quickly to the “environmental” or “ecosystem” changes seem to give I. coindetii an advantage in competition with the long lived finfish species. Accordingly, there is potential to use squid population dynamics as recorders to track environmental and ecological changes, as well as overexploitation. The adopted methodology drew attention to changes occurring within the stock of I. coindetii, and could provide an opportunity for managers to consider action at an early stage. The multi-indicator system and the TL methodology are illustrated as means to follow dynamic changes within squid stock, and to provide useful information for the assessment of the resource.

Some information on the biology of Illex coindetii Verany, 1839 (Cephalopoda, Ommastrephidae) in the South-Western Adriatic Sea (Central Mediterranean)

Distribution, length frequency structure, sex-ratio, maturity and dorsal mantle length–total weight relationship for Illex coindetii (Verany, 1839) were described for the first time in the South-Western Adriatic Sea (Central Mediterranean). Samples came from six experimental bottom trawl surveys carried out within the framework of the Medits programme from 1997 to 2002. Although specimens have been collected at a wide depth range, I. coindetii concentrates between 50 and 200 m. The population had a smaller squid size and length at first maturity with respect to other Mediterranean and Atlantic regions, probably due to the interaction of some environmental factors (sea temperature and fishing pressure) and the biological characteristics of the species. There was no difference in males/females ratio by year, but there was a general dominance of females over males at larger sizes and of males over females at smaller sizes. The different proportion of juveniles and mature individuals in the catch suggested the possibility of a prolonged spawning season with a spring spawning peak. There was a pronounced sexual dimorphism, females mature at larger mantle length attaining larger size in respect of males. Length–weight relationship revealed a difference between sexes in maturing and mature individuals only, with males resulting heavier and more robust than females at the same size. There were no differences in body proportions between unsexed and immature individuals of both sexes, which were considerably slimmer than maturing and mature counterparts.

Isotopic reconstruction of marine food webs using cephalopod beaks: new insight from captively raised Sepia officinalis

Cephalopod beaks are a valuable source of material for stable isotope analysis to reconstruct the feeding ecology of cephalopods and their predators. We conducted a controlled captive-rearing experiment on the cuttlefish Sepia officinalis L., 1758 to 10 months of age. During the first and second months of life, animals were fed mysids ( Mysidopsis sp.) and shrimp ( Palaemonetes pugio Holthuis, 1949), but after 2 months, they were fed a homogeneous diet of shrimp ( Farfantepenaeus aztecus (Ives, 1891) and Litopenaeus setiferus (L., 1767)) until sampling. Soft tissues such as buccal mass, arm, and mantle were enriched in 15N over the shrimp diet by about 3.3‰, with little change in 13C, a result in keeping with previous findings for other marine predators. However, beaks showed little isotopic enrichment over the diets at the time of beak formation, with the beak rostral tips representing the neonatal diet and the remaining beak material representing the adult (shrimp) diet. Additionally, for four wild cephalopod species ( Todaropsis eblanae (Ball, 1841), Illex coindetii (Verany, 1839), Loligo vulgaris (Lamarck, 1798), and S. officinalis) obtained commercially in France, we measured δ13C and δ15N values in lower beaks and soft tissues. Similar to the results of our captive study, soft tissues were consistently enriched in 15N over beaks by an average of 4.8‰ (range 3.9‰–6.1‰) but were slightly depleted in 13C by 0.8‰ (0.7‰–1.2‰). The isotopic measurement of cephalopod beaks can thus be used to directly trace the isotopic composition of cephalopod diets and will be a powerful tool in the reconstruction of higher-trophic-level predators of cephalopods, since beaks are often the only material remaining for analysis from field samples.

Development of new quality index method (QIM) schemes for cuttlefish ( Sepia officinalis) and broadtail shortfin squid ( Illex coindetii)

This article describes the development of sensory schemes for freshness grading of cuttlefish ( Sepia officinalis) and broadtail shortfin squid ( Illex coindetii) based on the recent quality index method (QIM). As preliminary work, four storage experiments were performed to choose the relevant sensory parameters for building the schemes. From an initial large set of parameters, some were chosen to be attributes for the QIM scheme. For cuttlefish, appearance, odour and mucus of skin, texture of flesh, cornea and pupil transparency, odour of the mouth region and connection between bone and head tissues; and for squid, appearance, odour and mucus of skin, texture of flesh, appearance of the eyes and ocular tissue brightness and odour of the mouth region. Five storage experiments were then used to test the tables and to shelf-life studies. The shelf-life, as measured by sensory attributes, is considered to be 10 days in ice for cuttlefish and 9 days in ice for squid. Sensory and shelf-life differences between these two species can be explained by morphological and biological reasons that probably include higher rigidity of the cuttlefish caused by the presence of the internal bone. For both species a high correlation between the quality index and the storage time in ice was obtained.

Concentrations and composition of organochlorine contaminants in different species of cephalopod molluscs from the Italian waters (Adriatic Sea)

Persistent organochlorines, such as polychlorinated biphenyls including coplanar congeners and DDT compounds were measured in the liver of different species of mollusc cephalopods: broadtail squid ( Illex coindetii), horned octopus ( Eledone moschata) and spider octopus ( Octopus salutii) collected in two different areas of the Adriatic Sea (central and southern Adriatic Sea). The concentration of PCBs exceeded DDT ones in horned octopus (PCBs: 617.0 ng g −1 lipid weight, DDTs: 188.0 ng g −1 lipid weight) and in spider octopus (PCBs: 590.0 ng g −1 lipid weight, DDTs: 293.0 ng g −1 lipid weight), while in broadtail squid PCB load (748.0 ng g −1 lipid weight) was similar to those of DDTs (514.5 ng g −1 lipid weight). No significant difference in PCB levels was observed among species, while DDT concentrations were higher in broadtail squid than in horned octopus and spider octopus. DDTs composition showed slight differences in relation to species, thought p, p′-DDE was the predominant compound in all cephalopod species (broadtail squid: 88.1%, horned octopus 94.1%, spider octopus: 97.5%). PCB isomer profiles were similar among species being hexachlorinated isomers the most abundant, followed by penta- and heptachlorobiphenyls, while tri- and tetrachlorobiphenyls made up a small percentage of the total PCB residues. Regarding coplanar congeners, non- ortho PCBs were below the detection limit in all samples and the 2,3,7,8-TCDD toxic equivalent (TEQ) concentrations were very low. The influence of biological and ecological factors (size/weight and location) on the bioaccumulation of organochlorine compounds has been discussed.

Changes in Tissue Biochemical Composition and Energy Reserves Associated With Sexual Maturation in the Ommastrephid SquidsIllex coindetiiandTodaropsis eblanae

The aim of this study was to investigate the biochemical changes that occur during sexual maturation of the squids Illex coindetii and Todaropsis eblanae. In both species, amino acids and protein content increased in the gonad throughout maturation, but the allocation of these nitrogen compounds from the digestive gland and muscle was not evident. A significant (P < 0.05) increase in the content of lipids and fatty acids was observed in the gonad and digestive gland. It seems that both species take energy for egg production directly from food, rather than from stored products. Analyses for cholesterol revealed a significant (P < 0.05) increase in the gonad, and the lipid content differences between species are potentially related to different feeding ecologies. The glycogen reserves in the gonad increased significantly (P < 0.05), suggesting that glycogen has an important role in the maturation process. It was evident that sexual maturation had a significant effect upon the gonad energy content, but because the energy variation in the digestive gland and muscle was nonsignificant (P > 0.05), there was no evidence that storage reserves are transferred from tissue to tissue.

Allozyme analysis of geographical and seasonal variation of Illex coindetii (Cephalopoda: Ommastrephidae) from central Mediterranean and Iberian Atlantic

Previous morphological studies of Illex coindetii from the Mediterranean have shown both juvenile and mature individuals all year round suggesting an homogeneous population pattern, however, seasonal spawning variation seems to exist varying with geographical area. Present work analysed 240 individuals from the northern Tyrrhenian and Atlantic Iberian waters at the four year-round seasons using 33 presumptive enzyme-coding loci to compare geographical and temporal variances. Genetic variability was low (Ho=0·02–0·04). Moderate variation at some loci was found due to both temporal and geographical factors (12% of total genetic variance) and to temporal variance (FST=0·004–0·015). Unweighted pair-group method using arithmetric averages (UPGMA) and Multidimensional scaling–minimum spanning tree (MDS–MST) analyses after Cavalli-Sforza &amp; Edwards (1967) chord genetic distances showed the summer Italian and the spring Atlantic samples as the most divergent among the whole.

The recruitment of gill-infesting copepods as a categorical predictor of size-at-age data in squid populations

AbstractThe independent effects of host age and size on the recruitment of the gill-infesting copepod parasite Pennella sp. were examined in the short-finned squid (Illex coindetii) from Galician waters (ICES Areas VIIIc–IXa). Older and larger squid had larger parasite infrapopulations, but in general the age of squid described the parasite recruitment to the host population better than did mantle length or body weight of squid. Parasite infrapopulations were markedly clumped or overdispersed in those squid hatchling groups with greater parasite recruitment, indicating close adjustment of host/parasite life cycles. Moreover, the gill infestation did moderate the relationship between age and body weight of squid, though the strength or importance of the variation associated with the relationships is not known. The results show that infestation by pennellids contributes to the variability in squid growth, being one of the multiple categorical predictors of size-at-age data in several infested cephalopod species commercially exploited in European waters.

A critical habitat for Mediterranean fish resources: shelf-break areas with Leptometra phalangium (Echinodermata: Crinoidea)

This paper considers the potential role of the crinoid Leptometra phalangium as an indicator of highly productive areas along the shelf break that can sustain large biomasses of benthopelagic fish and recruits. The structure of fish assemblages in the central Mediterranean Sea (central-western coast of Italy), analysed on the basis of surveys carried out in summer and autumn from 1997 to 2001, revealed the presence of a well-defined group of species on the shelf break. This area, occurring at a depth of between 120 and 170 m, is characterised by detritic organogenic sediments colonised by the crinoid L. phalangium, a suspension-feeding macro-epibenthic species confined in the Mediterranean to the shelf-break area. Its abundance in the studied area can reach 12–15 ind. m−2. A total of 121 species belonging to 66 families of demersal organisms (crustacean decapods and stomatopods, cephalopods, selaceens and teleosteens) were caught at shelf-break stations from September to October. The species which typified the assemblage were the fishes Trisopterus minutus capelanus, Merluccius merluccius, Glossanodon leioglossus, Argentina sphyraena, Capros aper, Macroramphos scolopax and Lepidotrigla cavillone, the crustacean decapod Parapenaeus longirostris and the cephalopods Illex coindetii and Todaropsis eblanae. Detritic shelf-break stations showed a higher abundance of demersal organisms than stations distributed on muddy bottoms in the same depth range (100–200 m). Such differences appeared to be significant in September–October, when a clear increase in benthopelagic zooplanktivorus species, such as Glossanodon leioglossus, Trachurus trachurus, Trachurus picturatus, was found. The length structure of species occurring on the shelf break showed that for some of them the selection of this area is related to specific phases of their life cycle. Significant highest abundance of recruits and juveniles was observed for Merluccius merluccius, Helicolenus dactylopterus, Phycis blennoides, Parapenaeus longirostris and Capros aper in at least one of the two seasons. Similarly, an increased abundance of spawners of red mullet Mullus barbatus and four-spotted megrim Lepidorhombus boscii was observed on the shelf break. Results of this study may have important consequences for management of fish stocks and assemblages in the central Mediterranean. The co-occurrence of high densities of L. phalangium and benthopelagic fish, occurring mainly with juveniles and spawners, strongly indicates a potential role of L. phalangium as an indicator of highly productive areas around the shelf break. Such areas appear to play a major role in the production of some of the most abundant and commercially important fish species, such as the Mediterranean hake and red mullet.

Characterization and Functionality of Frozen Muscle Protein in Volador (Illexcoindetii), Pota (Todaropsis eblanae), and Octopus (Eledone cirrhosa)

ABSTRACT: Three species of cephalopods: volador (Illex coindetii), pota (Todaropsis eblanae), and octopus (Eledone cirrhosa) were classified according to sex, stage of sexual development, and anatomical zone for characterization and functionality of their muscle proteins. The 3 species exhibited very similar levels of total protein. Octopus mantles and arms contained the least proline and the most hydroxyproline. The highest solubility values in immature pota coincided with the lowest apparent viscosity and emulsifying capacity values. The highest insolubility values observed in octopus coincided with the highest viscosity and emulsifying capacity values. However, in volador which exhibited an intermediate solubility, viscosity was very high and emulsifying capacity was very low.

Vertical distribution and abundance of juvenile cephalopods in Aegean Sea

This study was carried out in northern (Saros Bay) and southern (Gokova Bay) parts of the Aegean Sea. In pelagic samplings, Hamburg Plankton Net (HPN) was used. Samplings were done out at four different periods of a 24 hour day; sunrise, noon, sunset and midnight. Horizontal hauls were carried out at depths of 100, 350 and 650 m. As the result of 24 hauls in both parts of the Aegean Sea, one hundred juvenile specimens were sampled and 14 species were determined. Juvenile cephalopods were mostly frequent at 350 m. Among the determined species, Chtenopteryx sicula (Verany, 1851), Brachioteuthis riisei (Steenstrup, 1882), Illex coindetii (Verany, 1839), Thysanoteuthis rhombus Trochel, 1857 and Argonauta argo Linnaeus, 1798 juveniles are being reported for the first time in the Aegean Sea. 28% of the catches were from the northern Aegean and the remaining 72% were from the southern Aegean. Heteroteuthis dispar (Ruppell, 1844) was the most common species.

Identification of Illex coindetii , I . illecebrosus and I . argentinus (Cephalopoda: Ommastrephidae) throughout the Atlantic Ocean; by body and beak characters

Shortfinned squid species of the genus Illex support commercial fisheries throughout the Atlantic Ocean and Mediterranean Sea. Previous identification of interspecific and intraspecific populations by morphological and size-at-maturity studies have not provided conclusive results. We analysed morphometric body and beak variables (24 characters) in three species of the genus (I. coindetii, I. illecebrosus and I. argentinus), using a geographic and seasonal series of 33 populations for 1,500 specimens of I. coindetii, I. illecebrosus and I. argentinus. Residuals of the regression between each morphometric body and beak variable and mantle length were used as input in a stepwise discriminant analysis. Species discrimination by body and hectocotylus characters required at least eight variables and resulted in high correct-classification percentages for I. coindetii and I. argentinus (75% and 90%, respectively), whereas the best identification resulted from beak characters (83% correctly classified). Size of the suckerless basal arm, sucker-bearing length and beak lateral wall discriminated best among I. coindetii from northern Iberia, northwest Iberia (year-1996) and Ireland in the Atlantic and western Mediterranean versus middle and eastern Mediterranean samples. Canadian shelf and American samples were discriminated from Canadian slope I. illecebrosus. Winter/shelf and winter/slope samples of I. argentinus seemed to form a single biological group separated from Falkland Island, 46°S/autumn spawners and 46°S/1996 specimens along the Patagonian Shelf. No significant sexual or maturity polymorphism was obtained. Discriminant analysis optimised population diagnosis on a morphometric basis of interest in fisheries strategies. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00227-002-0796-7.