Food and daily ration of the rock soleLepidopsetta bilineata (Pleuronectidae) in the eastern Bering Sea

A total of 129 specimens ofLepidopsetta bilineata (Ayres) were collected in the eastern Bering Sea (57°02–58°11N; 161°58–164°38W) between 28 August and 7 September 1984. Examination of its stomach and intestine contents revealed that polychaetes, gammarid amphipods and echiuroids constitute the bulk of its diet. Prey type is related to fish size. Juveniles consume more mobile prey, such as small crustaceans (gammarid amphipods, cumaceans, carideans), while adults, although still continuing to feed on gammarid amphipods, preferentially feed on infaunal organisms such as polychaetes, echiuroids and mollusks. Some prey, such as echinoderms, fishes and urochordates, were encountered only in stomachs, which resulted in a higher index of feeding diversity for this organ. Rock sole feeds primarily during daylight hours, peaking at dusk. Its daily ration was estimated as 0.49, 1.12, and 1.61% of fish body weight from contents of stomach, intestine, and stomach plus intestine, respectively.     

Diets of piscivorous fishes in a tropical Australian estuary,with special reference to predation on penaeid prawns

The diets of fish from the tropical Embley Estuary in the eastern Gulf of Carpentaria, Australia, were analysed with particular reference to piscivory and predation on juveniles of commercially important penaeid prawns from October 1986 until July 1988. Of the 77 species caught, 52 were piscivorous, and of these 37 ate penaeid prawns. The most numerous piscivores wereScomberoides commersonianus, Arius proximus, Lates calcarifer, Polydactylus sheridani andRhizoprionodon acutus, the first four of which accounted for over 90% of all prawns eaten. Twenty species are commercially important species of prawns. The proportions of penaeids in the diets varied seasonally, according to the density of penaeids in the estuary. The proportion was highest during the pre-wet period (November) and lowest during the dry period (July–August). Predation on prawns was highest in the lower and middle reaches of the river. Estimates of the rates of predation on the two most common juvenile commercial prawns,Penaeus merguiensis andP. semisulcatus, are presented and discussed.     

Hyperiid amphipods in the eastern part of the South Pacific gyre

Studies were made of Amphipoda Hyperiidea collected in 1987 with a pelagic trawl in the South Pacific anticyclonic gyre in the vicinity of the Nazca and Sala y Gómez ridges (17°35 to 26°01S, 80°10 to 100°50W), at depths ranging from 50 to 300 or 600 m. Forty-three hauls contained 7 198 specimens, comprised of 119 species within 43 genera. Two of the species appeared to be new for science; two others were found in the Pacific Ocean for the first time. A comparison with hyperiid collections from other tropical Pacific regions revealed great stability of oceanic faunal composion. However, the collections differed considerably in their dominant species. Furthermore, comparison of Hyperiidea from various parts within the investigated area of the South Pacific gyre also reflected differences in dominant species. The degree of these mesoscale spatial differences was comparable to that among the central regions of the northern and southern anticyclonic gyres.     

Capillary supply and mitochondrial volume density in the axial muscles of the mesopelagic teleost Argyropelecus hemigymnus

Quantitative measurements have been made on the ultra-structure and capillary supply to the axial muscles of the mesopelagic hatchet fish Argyropelecus hemigymnus (Cocco, 1829). Fish were collected at Eastern North Atlantic Ocean Station 10244, 32°48N; 31°15W during November 1980, from a depth of 480 to 550 m. Mitochondria with densely packed cristae occupy 44.3% of slow-fibre volume. Each myofibril is in direct contact with a mitochondrion. Compared with other fishes studied, the capillary supply to A. hemigymnus slow fibres is poorly developed. The average number of capillaries per fibre is 0.9, such that each m of capillary contact supplies 0.011 m² of fibre cross-sectional area. The capillary surface area (m²) supplying 1 m³ of slow-fibre mitochondria is 0.17 in anchovy (Engraulis encrasicolus), 0.14 in rat-fish (Chimaera monstrosa), 0.14 in tench (Tinca tinca), 0.16 in catfish (Clarias mossambica), and only 0.025 for A. hemigymnus. It is suggested that, relative to the former species, some modifications in factors determining tissue oxygenation (e.g. myoglobin concentrations, blood flow, perfusion distribution or haemoglobin) and/or mitochondrial respiration rate are required in order to match oxygen supply and demand to the slow muscle in A. hemigymnus.     

Feeding mechanism of Pelagia noctiluca (Scyphozoa: Semaeostomeae); laboratory and open sea observations

The behaviour of the oral arms of Pelagia noctiluca (Forsskål) has been investigated in open sea predation and in predation induced both in the laboratory and the natural environment. Specimens were first studied in the field and then collected from coastal aggregations in the Gulf of Trieste, North Adriatic Sea, in December 1985 (Lat. 13°40 E, Long. 45°42 N) and in June 1986 (Lat. 13°39 E, Long. 45°43 N). The results of laboratory experiments and in situ observations, recorded on videotapes and photographs, show that the marginal tentacles are utilized to: (1) paralyze the prey; (2) contract and bend inward towards the nearest oral arm. Occasionally the tentacle does not contract and the prey is released; thus prey selection may occur. The oral arms are therefore involved in the: (1) transport of prey from the tentacle to the gastric cavity; (2) catching of motionless prey; (3) anchoring the medusa to the substratum. A similar feeding pattern can explain the survival of several specimens of P. noctiluca near the bottom during the winter of 1985/1986 in the Gulf of Trieste (North Adriatic Sea) in spite of the severe climatic conditions.     

Food habits and intestinal parasites of deep demersal fishes from the upper continental slope east of Newfoundland,northwest Atlantic Ocean

Stomach contents and intestinal parasite faunas of 471 individuals of demersal fishes in 14 species were examined from the Carson Canyon region (Lat. 45°30N; Long. 48°40W) of the upper continental slope of the Grand Banks off Newfoundland, Canada. Individual species tended to feed either on benthic or on pelagic/benthopelagic organisms, but pelagic prey assumed the greatest importance overall. Data from stomach contents were supported by the parasite information. Prevalence of parasites was higher in benthic feeders (53.1%) than in pelagic feeders (28.9%), and relative abundance by major group was: Digenetic Trematoda 5.8% benthic vs 27.8% pelagic, Nematoda 53.1% vs 72.2%, and Acanthocephala 40.9% vs 0%. Of the dominant fishes, there were more species of benthic feeders (5) than pelagic feeders (3), but pelagic feeders were numerically more abundant (pelagic 70.9%, benthic 20.5%). Benthic feeders were on average larger (=270.6g) than pelagic ones (=130.6g), but pelagic feeders represented a larger proportion of the biomass (pelagic 43.3%, benthic 25.9%). The results of this study combined with those from other areas suggest that feeding from the pelagial by demersal fishes at upper continental slope depths is probably the general rule.     

The hearing of an avian predator and its avian prey

Summary Auditory tuning curves of a small songbird, the great tit (Parus major), and of its principal avian predator, the European sparrowhawk (Accipiter nisus), were determined by an operant positive reinforcement conditioning procedure, using the method of constant stimuli. Thresholds were measured by the criterion of a 50% correct response and a d of 1.5 for intra- and interspecific comparison, respectively. The best frequency of both species was 2 kHz, the hawk being 6.5 dB SPL more sensitive than the tit. Although the high-frequency cutoff was very similar in both species, at 8 kHz the great tit was about 30 dB more sensitive than the sparrowhawk. The hearing abilities of the prey and its predator are discussed with reference to the acoustic alarm communication of great tits confronted with sparrowhawks. Two alarm calls lie in the frequency range of the best hearing of both the hawk and the tits: the mobbing call and a call given in response to a nearby hawk when fleeing from it. In contrast, the seeet call, an alarm call given mainly in response to distant flying sparrowhawks, can only be heard well by the tit. The implications of these results for hypotheses concerning the evolution of alarm calls in small songbirds are discussed.     

Polychlorinated biphenyl (PCB) uptake by marine phytoplankton

The time-courses of uptake for 2,4,5,2,5-pentachlorobiphenyl (PCB) by 11 marine phytoplankton species were measured and found to be rapid, with equilibration occurring within 0.5 to 2.0 h. These data were described with the empirical Freundlich adsorption isotherm. The relationship between cell density and accumulation of PCBs was also investigated. Concentration factors on a volume per volume basis ranged from 1.23x10⁴ to 2.41x10⁶ for the 11 algal species examined. These values are comparable in magnitude to factors reported previously for phytoplankton in natural marine systems.     

Ammonium enhancement of dark carbon fixation and nitrogen limitation in zooxanthellae symbiotic with the reef coralsMadracis mirabilis andMontastrea annularis

The nutrient status (limitation vs sufficiency) of dinoflagellates (zooxanthellae) symbiotic with reef corals in Bermuda was assessed in 1989 and 1990 by measuring the enhancement of dark carbon fixation with 20 M ammonium by isolated symbionts. A colony ofMadracis mirabilis was kept in the laboratory and fed daily or starved for one month. Symbionts from fed portions of the colony had ammonium-enhancement ratios (NH _4dark ⁺ ; SW_dark;SW=seawater without added ammonium) similar to those of the original field population (1.2 to 1.3). Ammonium-enhancement ratios increased with starvation of the host (x1.7) as did values forV _D:V _L [(ammonium dark rate-seawater dark rate): light rate in seawater]. Both parameters indicated decreasing nitrogen sufficiency of the algae when the host was not fed, but starvation appeared to affect these algae less than symbionts of sea anemones. Field samples of zooxanthellae fromM. mirabilis (Three Hill Shoals and Bailey's Bay Flats) yielded results similar to those for fed corals, but those taken from Bailey's Bay Flats in May 1990 yielded exceptionally high values for enhancement (>3) andV _D:V _L indicating pronounced nitrogen limitation at the time of sampling. We sampled zooxanthellae from populations ofMontastrea annularis at 8 m (Three Hill Shoals) and 24 m (Soldier's Point) depths. Enhancement andV _D:V _L values for zooxanthellae from the 8 m corals were density-dependent: symbionts from corals with normal symbiont densities displayed the most nitrogen limitation (enhancement values=1.4 to 2.0), while those from bleached corals with lower density exhibited enhancement andV _D:V _L values typical of nitrogen-sufficient algae. Symbionts isolated from the 25 m corals yielded the highest values, and appeared to exhibit the least nitrogen-sufficiency for this species.     

Comparison of light- and SST-based geolocation with satellite telemetry in free-ranging albatrosses

Light-based archival tags are increasingly being used on free-ranging marine vertebrates to study their movements using geolocation estimates. These methods use algorithms that incorporate threshold light techniques to determine longitude and latitude. More recently, researchers have begun using sea surface temperature (SST) to determine latitude in temperate regions. The accuracy and application of these algorithms have not been validated on free-ranging birds. Errors in both geolocation methods were quantified by double-tagging Laysan (Phoebastria immutabilis Rothschild) and black-footed (P. nigripes Audubon) albatrosses with both leg-mounted archival tags that measured SST and ambient light, and satellite transmitters. Laysan albatrosses were captured and released from breeding colonies on Tern Island, northwestern Hawaiian Islands (23°52N, 166°17W) and Guadalupe Island, Mexico (28°31N, 118°10W) and black-footed albatrosses from Tern Island. Studies were carried out between December 2002 and March 2003. For all birds combined, the mean ± SD great circle (GC) distance between light-based locations and satellite-derived locations was 400±298 km (n=131). Errors in geolocation positions were reduced to 202±171 km (n=154) when light-based longitude and SST-based latitude (i.e. SST/light) were used to establish locations. The SST/light method produced comparable results for two Laysan albatross populations that traveled within distinctly different oceanic regions (open ocean vs more coastal) whereas light-based methods produced greater errors in the coastal population. Archival tags deployed on black-footed albatrosses returned a significantly higher proportion of lower-quality locations, which was attributed to interference of the light sensor on the tag. Overall, the results demonstrate that combining measures of light-based longitude and SST-based latitude significantly reduces the error in location estimates for albatrosses and can provide valid latitude estimates during the equinoxes, when light-based latitude measurements are indeterminate.Communicated by J.P. Grassle, New Brunswick     

Dynamics of zinc-65 specific activity and total zinc in benthic fishes on the outer continental shelf off Central Oregon

The dynamics of ⁶⁵Zn specific activity and total zinc in benthic fishes on the outer continental shelf off central Oregon (USA) were examined. A differential equation that relates specific activity of ⁶⁵Zn in fish to that in fish food was used to estimate 's (zinc uptake-rate coefficients) for 3 different size classes of the flounder Lyopsetta exillis, a small predator of pelagic Crustacea, and for 1 size class of the flounder Microstromus pacificus, a large predator of infauna. The 's obtained for L. exilis were very close to the obtained in the laboratory for the flounder Pleuronectes platessa. The estimated for M. pacificus was very much smaller than the 's estimated for the other two species. A model that related to predicted weight-specific feeding rates suggested that the smaller of M. pacificus was caused by a low absorption efficiency of zinc from its prey. Sensitivity studies indicated that time histories of specific activity in the fishes are not sensitive to moderate changes in . The negative correlation between specific activity in the diet and in the weight of L. exilis was the major cause of the negative correlative between specific activity and weight in this species. In M. pacificus, where composition of diet does not vary with size, specific activity was independent of weight. The time history of specific activity in M. pacificus was very much lower than those in the different size classes of L. exilis, a result caused mainly by the much lower specific activity of the prey of M. pacificus. Differences in specific activity among other benthic fishes were also correlated with differences in specific activity of their prey. The food-web dynamics responsible for these patterns are discussed. Variation in total zinc concentrations among species was small. Within species of flounder, zinc concentration varied only slightly or not at all with weight.     

Observations of planktonic bioluminescence in the euphotic zone of the California Current

The distributions of bioluminescence, temperature, salinity, oxygen. pH, and chlorophyll a were measured at 10 m intervals, to a depth of 100 m at a station (33°46N; 119°36W) in the California Current from 17 to 20 July 1982. The distribution of bioluminescence showed a marked day-night change which was consistent over the sampling period. The nighttime maximum was at the surface, and the daytime maximum was between 30 and 40 m. The shapes of the day and night distributions were independent of the absolute intensity of bioluminescence and were also insensitive to advection, as inferred from changing temperature-salinity relationships. The nighttime depth distribution broadened during a period of high wind Day to night differences in the color spectrum at the depth of maximum bioluminescence suggest that the luminescent organisms differed from day to night.     

Transformation of soft coral (Coelenterata: Octocorallia) terpenes by Ovula ovum (Mollusca: Prosobranchia)

The faecal pellets from specimens of the prosobranch mollusc Ovula ovum found feeding on the soft coral Sarcophyton sp. at Eclipse Island, Palm Island Group (18°46S; 146°33E) in November 1980 were analysed. The only terpene present in the faeces, 7,8-deoxysarcophytoxide, differed from the major constituent of the soft coral, sarcophytoxide, suggesting that the latter had been transformed into the former within the cowrie. This transformation is not trivial, and could not be produced simply by acid catalysis. Subsequent analysis of tissues dissected from different regions of O. ovum indicates that the transformation is probably effected by enzymes in the digestive diverticula stomach region of the prosobranch. The transformed compound is significantly less toxic to the mosquito fish Gambusia affinis Baird and Girard than the ingested compound.     

A comparison of strike and prey capture kinematics of three species of piscivorous fishes: Florida gar ( Lepisosteus platyrhincus), redfin needlefish ( Strongylura notata), and great barracuda ( Sphyraena barracuda)

Ram feeding is the process by which a predatory fish uses a high-velocity lunge or chase to overtake its prey. This study compares the strike and prey capture behaviors and kinematics of three species of ram-feeding fishes: Florida gar Lepisosteus platyrhincus, redfin needlefish Strongylura notata, and great barracuda Sphyraena barracuda. These ram-feeding piscivores are morphologically similar with fusiform bodies, posteriorly placed dorsal and anal fins, and large, conical teeth. Strike and prey capture kinematics for five individuals of each species were recorded with high-speed video. Pre-strike behavior in L. platyrhincus consists of a slow stalk, resulting in the close, lateral positioning of the predators head relative to the prey. Lepisosteus employ a sideways lunge of the head during the strike, which lasts only 25–40 ms and is the most rapid strike among these three species. Strongylura notata and Sphyraena barracuda exhibit longitudinal orientation to the prey before the strike, followed by a high velocity, head-on lunge, initiated by an s-start in Sphyraena barracuda. Prey capture in adult L. platyrhincus and Strongylura notata is characterized by the jaws closing on the prey, with the prey held orthogonal to the jaws. This is followed by manipulation using the inertia of the prey to reposition the prey head first, and then suction transport into the buccal cavity. Prey capture in juvenile Sphyraena is accomplished by closing the jaws after the prey has entered the buccal cavity, resulting in possible ram transport of the prey with no oral manipulation under these experimental conditions. Although these three species all employ ram feeding for prey capture of elusive prey, each species has a unique repertoire that appears to minimize hydrodynamic constraints and prey response, utilize locomotory capabilities, and may be suited to each species specific habitat.Communicated by P.W. Sammarco, Chauvin     

Response of a soft-bottom harpacticoid community to stingray (Dasyatis sabina) disturbance

The recolonization by harpacticoid copepods of patches disturbed by stingrays [Dasyatis sabina (LeSeur)] feeding in a subtidal (2–3 m depth) site off the Florida gulf coast (Lat. 29°54.55N, Long. 84°31.45W) was followed. Samples from disturbed patches could no longer be distinguished from control samples in terms of numbers of harpacticoids 29 h after disturbance. No species became significantly disproportionately abundant during the recovery suggesting that small-scale natural disturbances are not an important organizing force in this community.     

Identification of Amazon River water at Barbados,W. Indies,by salinity and silicate measurements

Salinity and silicate concentrations were studied at about fortnightly intervals for 21 months at a station near Barbados, W. Indies; latitude 13°15 N, longitude 59°42 W. A sensitive inverse correlation was found to exist at 5 and 25 m, but not at greater depths. Salinity near the surface varied between 33.5 and 36.0, and silicate between a little less than 1 and 4 g at/l. Low salinity water, rich in silicate, was found from February to July; salinity increased and silicate decreased from September to December. It is argued that the low salinity water at Barbados can be identified with the areas of reduced salinity found by Ryther et al. (1967) about latitude 8° to 10° N, longitude 50° to 55° W, and that this water originates from the Amazon River. Local precipitation does not seem to be a significant factor.     

What is the sex ratio of harpacticoid copepods in the deep sea?

The sex ratios of deep-sea harpacticoids have been thought to be greatly skewed toward females. The representation of males is notably more equitable (approximately 1:2) at three deep-sea sites (San Diego Trough: 32°52.4N, 117°45.5W, 1 050 m, January 1987; Porcupine Seabight: 51°36.85N, 12°57.30W, 1 369 m, August 1984; northwest Atlantic, 40°27N, 62°20W, 4 820 m, July 1982, June 1983). This ratio conceals extensive variation at the species level. For some species, males are unknown. For other species, males are more numerous than females. Sampling bias against males can occur and may explain the more extreme reports of male rareness in the literature.     

Metabolism of a nonylphenol isomer by Sphingomonas sp. strain TTNP3

For elucidation of the metabolism of the endocrine disruptor nonylphenol by Sphingomonas sp. strain TTNP3, the degradation of an isomer of nonylphenol, 4(2,6-dimethyl-2-heptyl)-phenol, has been studied. As in the case of 4(3,5-dimethyl-3-heptyl)-phenol, the metabolism of this nonylphenol isomer leads to the formation of the NIH-shifted product 2(2,6-dimethyl-2-heptyl)-1,4-benzenediol (NIH: National Institute of Health), but also to the alkoxy derivative 4(2,6-dimethylheptan-2-yloxy)phenol as additional metabolite. To the best of our knowledge, this is the first report describing the formation of alkoxyphenol as a degradation product of nonylphenol. Additionally, these results provide for the first time evidence for slight differences in the biodegradation of the isomers of nonylphenol.     

Algal overgrowth of alcyonacean soft corals

Colonies of the soft coral Lobophytum pauciflorum (Ehrenberg, 1834) (Coelenterata: Octocorallia: Alcyonacea: Alcyoniidae), some of which were heavily overgrown by the algae Ceranium flaccidum (Kuetzing) Ardissone and Enteromorpha sp., and other minor epizoites, were collected at Taylor Reef (17°50S; 146°35E) in the Great Barrier Reef. Overgrown colonies contained the diterpene 2-epi-sarcophytoxide as the major secondary metabolite, while conspecific colonies with clean polyparies contained two diterpenes in approximately equal amounts: 14-hydroxycembra-1,3,7,11-tetraene and 15-hydroxycembra-1,3,7,11-tetraene. By contrast, twenty conspecific pairs of overgrown and clean colonies of other alcyoniid soft corals collected from Pelorus Channel, Palm Island Group (18°34S; 146°29E), showed no chemical differences within in the pairs. Cultures of a common species of Ceramium [C. codii (Richards) Mazoyer] were incubated with different concentrations of nine soft-coral-derived diterpenes and significant algal growth inhibition was observed in many cases. It appears that terpenoids from soft coral may contribute to the lack of epizoic organisms on soft-coral polyparies.     

Feeding habits of the Madeira rockfish <Emphasis Type="Italic">Scorpaena maderensis</Emphasis> from central Mediterranean Sea

In order to assess diet composition and niche breadth of this species, we analysed the stomach content of 182 specimens collected monthly along the eastern coast of Sicily (Central Mediterranean Sea). Overall, 50 prey taxa belonging to five major groups (algae, gastropods, crustaceans, polychaetes, fishes) were identified in 102 full stomachs. Benthic or epibenthic crustaceans, such as decapods, amphipods and isopods were the most important prey, whereas algae, gastropods, polychaetes and fishes were only occasionally ingested. In terms of composition by species, the diet of Scorpaena maderensis was characterized by a variety of rare or unimportant prey, which was consumed by few individuals only, although sometimes in large amount. As a result, S. maderensis can be considered a generalized and opportunistic feeder. The feeding intensity followed roughly a seasonal trend, with a minimum food intake in summer. The individual fish size was the most important factor affecting diet. According to the observed ontogenetic shift, small-sized individuals fed primarily on small crustaceans (i.e. amphipods and isopods), whereas large-sized specimens consumed preferably bigger and more vagile prey, such as walking and swimming decapods. No significant differences in diet were observed in relation to sex of predator and sampling season.