A method for a qualitative analysis of sea urchin diet is based on the characterization of the photosynthetic pigment indices of the major algal groups in the sea urchin gut. The pigments were separated by reverse-phase high performance liquid chromatography (RP-HPLC). This study demonstrated that HPLC is a better method to estimate chlorophyll-a in the gut contents than the conventional spectrophotometric methods which overestimate the amounts by including chlorophyll-a breakdown products. Three sea urchins species, Paracentrotus lividus, Psammechinus miliaris and Sphaerechinus granularis, settled on the loose-lying coralline algae (maerl) in the Bay of Brest (France), were used in this study. The algal pigments identified within the gut contents included chlorophylls-a, -b, -c, fucoxanthin, lutein, βε-carotene and ββ-carotene. The presence of chlorophylls and carotenoid biomarkers was used to characterize the three algal groups: Rhodophyceae, Chlorophyceae, Phaeophyceae in estimating sea urchin diet. The pigment analysis reported here demonstrated that the three species of sea urchins investigated mainly consumed Rhodophyceae which dominate the epibenthic flora in the study area.

Seasonal variations in the gonad index and the biochemical composition of gonad and gut tissue of the sea urchin, Paracentrotus lividus (Echinodermata: Echinoidea) were determined. Samples were collected from Lorbé (Galicia, north-western Spain) between November 1994 and October 1995. The gametogenic cycle of the sea urchin was annual, with a long, single spawning period from May to August 1995. Most of the biochemical components in gonad showed clear seasonal variation, which was related to the gonad cycle. The main component was protein, which ranged between 36 and 60% of the dry weight, with maximum levels coinciding with the minimum levels of glycogen. Gonad glycogen therefore seemed to be the energy source employed for protein synthesis during gametogenesis. Seasonal variation in total lipids in the gonad was less evident; the main lipidic component was triacylglycerol (around 10% of the dry weight), whereas total cholesterol accounted for less than 1%. The gut does not seem to act as a storage tissue in P. lividus and seasonal variation in biochemical components may be a consequence of fluctuations in the availability of food.

The dynamics and feeding biology of a population of Marthasterias glacialis (Echinodermata: Asteroidea) was examined over a two-year period from 2000–2002 at Lough Hyne Marine Nature Reserve, Co. Cork, Ireland. A multivariate approach was used and both multiple factors and multiple interactions between factors were found to influence population structure. These included time of year, site, individual sea-star size, depth, and predator density. Individuals belonging to the smallest size-classes (0–50 mm and 51–100 mm) were most abundant amongst boulders in shallow water (0–1 m), while larger individuals were primarily found in water below 1 m in depth on finer grade substratum and shell debris. Dietary composition was also found to differ with depth; sea-stars in the immediate subtidal had an opportunistic diet, and fed on a variety of taxa, whilst those M. glacialis from 1–6 m were more selective and restrictive, feeding chiefly on bivalve prey. We propose that spatial partitioning of different size-classes and a generalist feeding strategy may account for the success of M. glacialis at Lough Hyne.

The diets of scaldfish Arnoglossus laterna, dab Limanda limanda, lemon sole Microstomus kitt, long rough dab Hippoglossoides platessoides, solenette Buglossidium luteum, thickback sole Microchirus variegatus, plaice Pleuronectes platessa, witch Glyptocephalus cynoglossus and Dover sole Solea solea in the Irish Sea were determined for March and October 1997 and 1998 and compared. Similarities in diets were examined using multivariate analyses. In general, there were differences in diet between species and generally the diets were similar within a species. Smaller individuals tended to have a similar diet. There were seasonal changes in the diets of individual species. Likewise, the overlap in diets between species changed between seasons and to a certain extent between sediment types.

Seasonal changes in the diet composition and trophic niche overlap were examined for the dominant members of the fish assemblage of the turbid low-salinity zone of the Scheldt estuary (Belgium). Samples of fish were taken in the cooling water of a power plant. Juveniles of eight species dominated the fish assemblage: two goby species, herring, sprat, bass, flounder, eel and pikeperch. Together, they had preyed upon 31 different prey taxa. Calanoid copepods and hyperbenthic mysids were the most important prey items with macrobenthic invertebrates being largely ignored. Pair-wise comparisons of trophic niche overlap showed that, in general, niche overlap between individuals of the same species was significantly higher than overlap between individuals from different species, suggesting that the available food resources were partitioned. The total annual prey consumption by the dominant fish species was estimated at 610 mg ash-free dry weight m−3.

Portuguese sole, Synaptura lusitanica, were collected from the Portuguese coast, between April 2001 and March 2002, to examine feeding habits, age and growth, and sexual cycle. Synaptura lusitanica fed on few prey items, its diet mainly composed of polychaeta, bivalvia and cephalochordata. Significant differences were found between the proportion of prey items according to season, length class of fish and coastal area. The main differences related to fish size were the higher ingestion of bivalvia by larger fish, in the west coast area, and the increase in the important cephalochordata for fish larger than 300 mm total length, in the south coastal areas. Polychaeta presented a lower importance in the spring–summer period while bivalvia increased its values in the autumn–winter period. Cephalochordata were more important in the autumn–winter period, but only for fish larger than 300 mm total length and in the south coastal areas. Vacuity was extremely high (mean value of 52%). Ages of S. lusitanica were determined from sagittae otoliths. The length of fish analysed varied from 157 mm to 480 mm, and the oldest fish was age 8. The von Bertalanffy growth equation parameters differed little between sexes, being the asymptotic length obtained for females higher compared to males. The highest values of the gonadosomatic index were obtained in summer, which was the period when the highest percentage of individuals in the spawning stage were recorded. Therefore, the spawning season seems to be from mid-spring (May) until the end of summer (September).

Polychaete prey were studied in the diet of 16 demersal fish species caught during an evaluation survey of demersal resources in the southern part of the Bay of Biscay during autumn, year 2000. A total of 27 prey taxa belonging to 17 families (21 of them at the species level) were found. Mullus surmuletus appeared as the main polychaete specialist. The consumption of polychaetes in other species, such as Pagrus pagrus, Chelidonichthys obscurus, Raja montagui, Scyliorhinus canicula, Trachyscorpia cristulata equinata and Pagellus acarne, was also important. Four species were analysed in more detail, M. surmuletus that preyed mainly on the families Nephtyidae, Sigalionidae and Goniadidae, P. acarne on Sigalionidae, R. montagui, on Sigalionidae, Arabellidae, Glyceridae and Aphroditidae, and S. canicula on Arenicolidae, Nephtyidae and Arabellidae. The most frequent species found in the stomachs were Nephtys hombergii, Aponuphis bilineata, Labioleanira yhleni, Arabella iricolor and Laetmonice filicornis. The predators had a clear preference for errant and carnivorous polychaete species, probably due to the more active behaviour of these prey, and also as a result of trawl fishing.

The interactions between beaugregory damselfish and ophiuroids, potential damselfish egg predators, were investigated using several field studies. A survey of back reef areas showed that the two most common ophiuroid species, Ophiocoma echinata and Ophioderma appressum, were significantly associated with the territories of beaugregory males within the coral rubble habitat where both ophiuroids and beaugregory's can be found. Feeding experiments showed that three ophiuroid species (Ophiocoma echinata, Ophioderma appressum and Ophiocoma wendtii) and Echinometra viridis consumed late development stage beaugregory eggs, whereas earlier stages were only consumed by Ophioderma appressum and Echinometra viridis. Manipulation of ophiuroid densities had no significant effect on the survival of beaugregory eggs and had no measurable impact on female mate choice. The aggressive response of male beaugregory damselfish towards three ophiuroid and one echinoid species showed significant differences among species but were lower than those shown to bluehead wrasse, Thallasoma bifasciatum; the principal daylight predator of eggs. The intensity of attacks by male beaugregory damselfish towards Thallasoma bifasciatum increased significantly if males were guarding eggs, but did not appear to change for the four echinoderm species. Male habitat selection was shown to be unaffected by the presence of ophiuroids.

Big-bellied seahorses, Hippocampus abdominalis (Chordata: Syngnathidae), feed predominantly on swarming mysids in southern Tasmania. We tested the possibility that kairomones mediate this predator/prey interaction. ‘Fish water’ was prepared by holding one seahorse in 4 l of seawater for 1 h and using this water within 1 h to test for presence of kairomones. One ml of this water pipetted into a tank containing five mysids, Paramesopodopsis rufa (Arthropoda: Mysidacea), induced a significantly increased number of tailflips (mysid escape response) compared with control seawater. The same effect was seen whether seahorses were fed or starved immediately before the experiment. This effect was not seen when realistic concentrations of excretory products, either ammonium hydroxide or urea, were used instead of fish water. When seahorses were kept in visual contact with mysid prey, but unable to capture them, subsequent testing of the ‘fish water’ in the same way as above did not produce a significant increase of tailflipping in mysids. Thus it appears that, when attacking, seahorses can suppress release of kairomones in order to remain chemically inconspicuous to their prey. This is the first demonstration of this phenomenon. When mysids in a cohesive swarm (65 or 100 individuals) were exposed to ‘fish water’, no significant anti-predator response i.e. decrease in swarm volume, could be detected. We interpret these results to indicate the greater vulnerability of mysids when not in social groupings (swarm or school) and the higher likelihood of an energetic response (particularly tailflipping) to a threat.

Like their counterparts at lower latitudes, many Antarctic midwater fish make extensive, diel vertical migrations. However, Antarctic species make these migrations in the absence of two of the three selective advantages generally ascribed to this behaviour. Because the water column is nearly isothermal, there is no metabolic bonus to be gained from thermal differences in habitat depth. Likewise, because their prey do not perform significant vertical migrations, the fish migrations act to diminish rather than enhance their feeding opportunities. For Antarctic midwater fish, the sole advantage of these migrations appears to be the avoidance of visually-cued predators in the upper part of the water column. An evaluation of the relative importance of the three selective factors supports the suggestion that predator avoidance may also be the principal driver of diel vertical migrations for midwater fish at lower latitudes.

The surface-swimming duration of basking sharks (Cetorhinus maximus) was determined in the western English Channel from May to July over a five-year period. Surface duration showed marked variation from 0·17 to 1·45 h over the short time period from late May to mid-June. Stepwise multiple regression was used to identify any relationships between surface-swimming duration and time of day, daily sea surface temperature (SST), and zooplankton density. There was no support for any effects of SST or two measures of zooplankton density (median and maximum densities). However, there were significant relationships for surface duration with time of day and minimum zooplankton density (r2=0·50) indicating basking sharks respond to the abundance of prey and its temporal availability. This suggests that the probability of sighting sharks at the surface will vary depending on the diel period and the surface abundance of zooplankton.

Data on the diets of harbour seals (Phoca vitulina) from two islands in the Inner Hebrides (Scotland, UK) based on collections of faecal samples made in 1993 and 1994 are presented. The diet included a range of fish and cephalopod species, of which the most important were gadoids, particularly whiting (Merlangius merlangus), along with pelagic scad (Trachurus trachurus) and herring (Clupea harengus). There were significant temporal and spatial (between-island) differences in diet. The relatively high importance of pelagic species and the low importance of sandeels (Ammodytidae) is consistent with previous studies on grey seals (Halichoerus grypus) in the Inner Hebrides but differs from studies based in other parts of Scotland.

This study reviewed published data on dietary preferences of beaked whales (Ziphiidae) from stomach contents analysis. Detailed data were only available for three of the six beaked whale genera (Hyperoodon, Mesoplodon and Ziphius). Stomach samples of these three beaked whale genera primarily contained cephalopod and fish remains, although some also contained crustaceans. Mesoplodon spp. were found to contain the most fish, with some species containing nothing but fish remains, while the southern bottlenose whale (Hyperoodon planifrons) and Cuvier's beaked whale (Ziphius cavirostris) rarely, if ever, contained fish. Of cephalopods identified, Histioteuthid, Gonatid, Cranchiid and Onychoteuthid species usually contributed most to prey numbers and biomass for all beaked whale genera. There was a wide range of species and families of cephalopods recorded from stomach contents, with no obvious preference for bioluminescent prey species, vertical migrating prey species or prey species with specific body compositions. Whales of the genus Mesoplodon generally contained smaller prey, such as cephalopods under 500 g in weight, compared with other beaked whales. Hyperoodon and Ziphius frequently contained much larger cephalopods with many important prey species having a mean weight of over 1000 g. This suggests that Mesoplodon occupies a separate dietary niche from Hyperoodon and Ziphius, which may be an example of niche segregation. In contrast, Hyperoodon and Ziphius appear to occupy very similar dietary niches but have geographically segregated distributions, with Hyperoodon occupying cold-temperate to polar waters and Ziphius occupying warm-temperate to tropical waters.

The stomach contents from a male sperm whale, Physeter macrocephalus, first located floating a short distance off the south coast of Crete were examined. The remains within the stomach consisted almost exclusively of cephalopod mandibles, or beaks, though other material was found including a piece of rigid plastic mesh. Of the beaks found, 1714 were upper beaks and 2178 were lower beaks, that were used to identify the species. A total of seven species was identified, all of which have been previously recorded in the eastern Mediterranean though are rarely caught by man. Of these Histioteuthis bonnellii was found to be the most important species in terms of both weight and numbers. Although it must be borne in mind that the whale may not have followed its normal feeding habits prior to its premature death, an important insight into its prey items can be revealed. This is the first documented account of the stomach contents of a sperm whale from the Mediterranean, and helps to complete a global record of sperm whale diets.