The present study assessed the effect of different feed ingredients on nutrient apparent digestibility coefficients (ADC), nitrogen/energy balance and morphology changes in the intestine of Nile tilapia; using a control diet and six test diets, in which the following six ingredients were included at 30%: hydrolysed feather meal (HFM), soybean meal (SBM), rice bran (RB), rapeseed meal (RM), sunflower meal (SFM) and dried distillers grains with solubles (DDGS). The proximal, middle and distal intestine was processed for quantitative histology counting the number of goblet cells (GC), and measuring the thickness of lamina propria (LP) and submucosa (SM). The study showed that the ADC of protein in raw materials were highest in SBM (92.2%), followed by SFM (90.2%), DDGS (89.2%), RM (87.8%), HFM (86.9%) and RB (84.0%). The nutrient ADCs had no correlation with intestinal morphology changes. Only the SBM diet caused noticeable changes in intestinal morphology such as an increase the thickness of SM and LP and the number of GC. The diet composition, however, altered the protein efficiency and the maintenance energy requirement. Protein retention efficiency was the lowest in fish fed HFM and the highest in RB. The highest maintenance energy requirements were observed in HFM and SBM treatments.

In order to understand how marine ecosystems function, it is essential to study the trophic interactions among the community members, particularly from poorly known regions. In this study, the feeding ecology and diet of conger eels,Conger conger, an abundant fish species with commercial interest, was examined in the north-east Atlantic, off Algarve (southern Portugal) between May 2005 and August 2006. The diet was characterized by species composition, size and mass of prey. Conger eels are opportunistic feeders, cannibalistic, feeding on benthopelagic/pelagic prey (67% by mass and 71% by number) but also benthic prey (32% by mass and 29% by number). Fish (67.8±4.7% in mass) are the main prey of conger eels, followed by cephalopods (16.5±3.8%) and crustaceans (15.6±3.7%). The most numerous (identifiable) fish consumed wereCapros aper, occurring in 90% of the stomach samples that contained food and representing 1.4% in mass, andScomber japonicus, the most important fish in mass (21.1%), which occurred in 4.2% of the stomach samples that contained food. The present study shows that octopodids can play a more important role in the diet of conger eels than previously thought. Of the species preyed upon by conger eels, six species (21% of the total prey taxa) are caught commercially(Trachurus trachurus, Scomber japonicus, Micromesistius poutassou, Helicolenus dactylopterusandConger conger)by local fisheries. As discards by local trawl and longline fisheries do not correspond with the diet ofC. conger, it is likely that most prey ofC. congerin rocky areas were caught actively in that study region.

The diet of Sepia o⁄cinalis was studied by examining the stomach contents of 522 specimens caught o¡ the coast of the Algarve, Portugal. A total of 49 di¡erent prey items, belonging to six taxa (Polychaeta, Cephalopoda, Teleostei, Bivalvia, Crustacea and Gastropoda) was found, indicating opportunistic feeding behaviour. The diet was examined in relation to season, sex and size. The diet of males and females were similar. For small S. o⁄cinalis, crustaceans were more important in weight, whereas for larger specimens, ¢sh were dominant. Seasonal di¡erences in the diet were apparent but were shown to be possibly in£uenced by the cuttle¢sh size.

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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.