This study concerns the cephalopod species that are part of the diet of the small-spotted catshark Scyliorhinus canicula and the longnose spurdog Squalus blainville sampled by commercial trawlers in the Aegean Sea from 2005 to 2012. Based on the examined cephalopod beaks, 15 species were identified belonging in six families of Teuthida, one of Sepiida and two of Octopoda. The diversity of cephalopod prey species was higher for S. canicula (N = 15) than for S. blainville (N = 10). Nektonic cephalopods comprised the majority (>72%) of the preyed species by both sharks, among which about 55% inhabit the demersal zone and 45% the mesopelagic. In the diet of S. canicula, the demersal squid Illex coindetii and the pelagic sepiolid Heteroteuthis dispar were equally represented composing 20% of prey specimens, followed by the small-sized squid Abralia veranyi and the demersal sepiolid Rossia macrosoma. The latter species was substituted in the diet of S. blainville by the demersal medium-sized octopod Scaeurgus unicirrhus, which with the equally represented three other species, composed 50% of the cephalopod prey. Differences observed between S. canicula and S. blainville in the condition of beaks retained in their stomach contents and in the variation of prey species diversity by predator specimen size, may imply differences in their foraging tactics (hunting for prey vs scavenging on the bottom), habitats and stomach evacuation frequency.

Data on life history aspects of two species of Squalus genus were collated from five different studies carried out in the Eastern Ionian Sea from 1995 to 2014. Data were collected from 948 longnose spurdogs Squalus blainville (Risso, 1827) and 65 spiny dogfish Squalus acanthias Linnaeus, 1758 caught by trawl and longlines. The mean length of both species increased with depth. Sexual segregation was observed for S. blainville, whereas a segregation of immature and mature individuals was detected for S. acanthias. The length–weight relationship for S. blainville indicated positive allometry (b > 3) for both sexes, whereas a negative allometry (b < 3) was found for S. acanthias for the combined sexes. The sex ratio of both species was in favour of males. For S. blainville, the gonadosomatic and hepatosomatic indices differed significantly between sexes but not between seasons with the maturity data supporting the hypothesis of continuous reproduction throughout the year. Length at first maturity (L50) for female and male S. blainville was 603 and 413 mm respectively. For S. acanthias, males collected in autumn had finished their spawning activity; the single specimen caught in summer was reproductively active. Females, caught only in summer, were all gravid. Prey identified in the stomachs of S. blainville belonged to three major groups: fish, cephalopods and shrimps. Other groups such as echinoderms and ascidians were also found. Identified prey in the stomachs of S. acanthias belonged to two main groups, fish and cephalopods, although other groups (including echinoderms and polychaetes) were also present.

Of the three species of the genus Squalus that occur in the Mediterranean Sea, S. blainville and S. megalops are very difficult to distinguish. This study assesses the variability in morphological features that have been used to differentiate between these species. Squalus were collected from stations within the 25-nautical mile Fisheries Management Zone around the Maltese Islands; 349 specimens were dissected and categorized into male and female, mature and immature, and individuals were randomly selected from each category to make up a sample of 169 specimens. For each individual, total length and first dorsal fin parameters were measured, and morphology of denticles isolated from the laterodorsal area, of the upper and lower teeth and of the chondrocranium was analysed. The first dorsal spine was shorter that the fin base in 93% of the specimens, which is typical of S. megalops; this character was not related to either gender or maturity. Chondrocrania with one lateral process (typical of S. blainville) and two lateral processes (typical of S. megalops) were present. Teeth from the same individuals showed morphological features that overlap between S. blainville and S. megalops. Both unicuspid (typical of S. megalops) and tricuspid denticles (typical of S. blainville) were observed on the same individuals. Twelve specimens (six having one and six having two lateral chondrocranial processes) were analysed genetically by sequencing of the mtDNA marker Cytochrome Oxidase Subunit I (COI). All resulted to be S. blainville showing that intraspecific variability in supposedly diagnostic morphological features is large enough to render these unreliable to tell apart these two species, especially in the field.