Biochemical composition of cephalopods with different life strategies,with special reference to a giant squid,<Emphasis Type="Italic"> Architeuthis</Emphasis> sp.

The present study is a comprehensive comparison of the biochemical composition (protein, lipid, glycogen and cholesterol contents, and amino acid and fatty acid profiles) of 14 species of cephalopods with different life strategies (benthic, nektobenthic, benthopelagic and pelagic) in distinct habitats (neritic, demersal, oceanic and deep sea), with special emphasis placed on a male Architeuthis sp. The giant squid showed a significantly lower protein and total amino acid content in the gonad and digestive gland. The major essential amino acids were leucine, lysine and arginine. The major non-essential amino acids were glutamic acid, aspartic acid and proline. The benthopelagic cirrate octopus Opisthoteuthis sp. showed a lower content of these nitrogen compounds in the muscle. In respect to lipid and fatty acid contents, the giant squid showed the highest values in the gonad and digestive gland and the lowest in the muscle. Most of saturated fatty acid content was presented as 16:0; monounsaturated fatty acid content, as 18:1 and 20:1; and polyunsaturated fatty acid content, as 20:4n-6, 20:5n-3 and 22:6n-3. The highest cholesterol content in the gonad was detected in Opisthoteuthis sp. and Architeuthis sp.; in the digestive gland. in Todarodes sagittatus; and in the muscle, in Sepia elegans. The highest glycogen value in the gonad was detected in Octopus vulgaris; in the digestive gland and muscle, the highest values were attained in Opisthoteuthis sp. The relationships between life strategies and biochemical composition were investigated and principal component analysis (PCA) was performed. The different cephalopod life strategies could be well separated on the basis of the first two principal components. The nektobenthic and pelagic strategies were clearly separated from the benthic, suggesting that these groups of species are characterized by lower lipid content and higher protein content in the gonad. A rather similar life-strategy distinction was obtained for the digestive gland. The benthopelagic strategy was also well separated from benthic and pelagic strategies and from Architeuthis sp. In the muscle, the results indicated lower nitrogen and carbon compound contents in Architeuthis sp. and Opisthoteuthis sp. The environmental conditions that possibly explain the Architeuthis sp. stranding, the relationships between biochemical compositions and the life strategies of the different cephalopod species studied are discussed.Communicated by S.A. Poulet, Roscoff     

Analysis of the structure of decapod crustacean assemblages off the Catalan coast (North-West Mediterranean)

We sampled the communities of decapod crustaceans inhabiting the depth zone between 3 and 871 m off the Catalan coast (North-West Mediterranean) from June 1981 to June 1983. The 185 samples comprised 90 species differing widely in their depth distributions. Multivariate analysis revealed four distinct faunistic assemblages, (1) littoral communities over sandy bottoms, (2) shelf communities over terrigenous muds, (3) upper-slope communitics, and (4) lower-slope or bathyal communities. The brachyuran crab Liocarcinus depurator is the most abundant species of the shelf assemblage, although L. vernalis dominates over the shallow sandy bottoms of the shelf. The dominant species of the upper-slope assemblage are nektobenthic species (Solenocera membranacea, Plesionika heterocarpus, Processa canaliculata), pelagic species (Pasiphaea sivado, Sergestes arcticus), and benthic species (Macropipus tuberculatus, Munida intermedia, Nephrops norvegicus). Aristeus antennatus comprise most of the biomass of the lower-slope community, which supports a greater diversity than the other assemblages. The main assemblages appear to be related to different hydrological characteristics, the extent of seasonal fluctuations, and to the changes in sediment structure associated with changes in the steepness of the bottom.     

Population structure in Banggai cardinalfish,<Emphasis Type="Italic"> Pterapogon kauderni</Emphasis>, a coral reef species lacking a pelagic larval phase

Previous studies on two reef fish lacking a pelagic larval phase (Acanthochromis polyacanthus and Embiotoca jacksoni) revealed features that may be characteristic of their lifestyle: (1) low levels of gene flow, (2) frequent population bottlenecks, and (3) strong phylogeographic breaks, all within their over 1,000 km coastal geographic ranges. The present study tested the predictive nature of these three characteristics in another species lacking a pelagic larval stage, but with a very restricted distribution (<10,000 km²). The Banggai cardinalfish, Pterapogon kauderni Koumans, 1933, is a mouthbrooding species occurring in the Banggai Archipelago (eastern Indonesia). Fish were captured in January and February (2001, 2002). The mitochondrial control region of 122 individuals from 22 locations was sequenced. P. kauderni individuals clustered in two reciprocally monophyletic clades corresponding to a southwestern population (restricted to the southwest of Bangkulu Island) and all northern and eastern populations, which included all the remaining samples. Data were compatible with reduced gene flow and the presence of severe bottlenecks; however, small sample sizes and limited genetic variability in P. kauderni prevented a definitive conclusion. Further studies using larger samples and more rapidly evolving molecular markers may provide enough power to conclusively test our hypotheses.Communicated by J.P. Grassle, New Brunswick     

Diets of clupeoid,stomiatoid and salmonoid fish of the Rockall Trough,northeastern Atlantic Ocean

The trophic interactions of species of fish of the continental slopes have not been investigated previously in detail. The present study examines the diets of the clupeoid, stomiatoid and salmonoid species occurring demersally and pelagically in the Rockall Trough to the west of Scotland and Ireland. Pelagic fish were collected between the surface and about 2 500-m depth between 1973 and 1978. Demersal fish were sampled at 250-m intervals of depths between 500- and 2 900-m depth during the years 1975 and 1981. Of the 28 species caught, 18 were strictly pelagic and dominated by the stomiatoids while five were strictly demersal. The remaining five species occurred in both the pelagic and demersal environment. The commonest clupeoid was Alepocephalus bairdii, which is a dominant species within the demersal fish associations at depths of 750 to 1 250m. This species, along with the deeper-living A. agassizi, and 3 other alepocephalid species feed primarily on benthopelagic prey but also exploit the epibenthos. The stomiatoid species, such as Cyclothone microdon, C. braueri, Maurolicus muelleri and Argyropelecus hemigymnus, dominate the associations of pelagic fish in the Trough. They feed on different proportions of ostracods, copepods and amphipods. Of the salmonoids, only Argentina silus and Bathylagus euryops occurred commonly and both feed on benthopelagic fauna, the latter at much greater depths than the former. The principal factor acting to prevent direct competition between species is the modal centres of bathymetric distribution of the species. Other contributing factors are briefly discussed.     

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 bathypelagic Decapoda,Lophogastrida, and Mysida of the eastern Gulf of Mexico

The Earth’s greatest living space is found in the bathypelagic zone of the oceans (depths >1,000 m), yet little research has been dedicated to these ecosystems. The micronekton of the bathypelagic zone in the eastern Gulf of Mexico (EGOM) was investigated with the goal of comparing its community structure with that of the well-studied mesopelagic micronekton. Herein is described a portion of that community, specifically species belonging to the orders Lophogastrida, Mysida, and Decapoda. A total of 46 species were collected, most of which have broad zoogeographic distributions. Seventeen of the species had not previously been collected above 1,000 m in the same location despite over 20 years of sampling. Compared to the mesopelagic zone, the bathypelagic community showed increased contributions to abundance and estimated biomass from the Oplophoridae and Eucopiidae, with a simultaneous decrease in the importance of the Dendrobranchiata. In addition, the bathypelagic zone was distinguished by a relatively high percentage of individuals that brood their eggs (77% vs. 15% in the mesopelagic zone). The results are interpreted as evidence that the bathypelagic zone contains a distinct pelagic community, with a biology and ecology fundamentally different from that of the mesopelagic zone.     

Feeding and swimming of lysianassid amphipods in a shallow cold-water bay

The potential for dispersal by lysianassid amphipods and their localization to carrion in a shallow cold-water bay in the Middle Saint Lawrence Estuary were assessed by means of endobenthic sampling, SCUBA observations, measures of swimming speeds, and by exposure of bait (50–100 g of fish) in traps. Seventy-five to 99.9% of animals attracted to traps were lysianassid amphipods belonging to five species. Lysianassid species were spatially segregated in the Bay at low tide but all were more or less dispersed at high tide. Second cohortAnonyx sarsi Steele and Brunel,Boeckosimus edwardsi andOnisimus littoralis (Krøyer) were more dispersed than the small first cohort individuals. Second cohortA. sarsi were crawlers or low (0–0.5 m off the bottom) suprabenthic swimmers in the day, but upper (0.5–2 m) suprabenthic swimmers at night. In contrast, first cohortA. sarsi were crawlers or low suprabenthic swimmers day-and-night, whileOrchomenella pinguis (Boeck) followed this swimming pattern at night but were generally akinetic in the day. Mean swimming speeds ofA. sarsi (13.6 cm s^-1) andOn. littoralis (12.1 cm s^-1) were 2 to 3 times greater than those ofOr. pinguis (7.4 cm s^-1) andPsammonyx nobilis (Stimpson) (4.4 cm s^-1). Catchability coefficients (i.e. ratio number of individuals per trap:endobenthic abundance) were 74 (A. sarsi), 8 (On. littoralis), 7 (Or. pinguis), and 0.7 (P. nobolis) m² of bottom. Gut content analysis indicated thatA. sarsi fed mostly on large carrion, whileOn. littoralis were markedly opportunistic, andOr. pinguis andP. nobilis relied on detritus, algae, and small crustaceans.     

Deep-sea bottom-living fishes at two repeat stations at 2 200 and 2 900 m in the Rockall Trough,northeastern Atlantic Ocean

Repeated sampling of deep-sea bottom-living fishes was conducted at two stations in the Rockall Trough at depths of 2 200 and 2 900 m. The 2 200 m station (M) was sampled 16 times by an Agassiz trawl between April 1978 and April 1985 and yielded 473 fish belonging to 17 species. The 2 900 m permanent station (PS) yielded 781 fish belonging to 11 species from 9 Agassiz trawls, 2 small box otter trawls, 4 semi-balloon otter trawls and 7 epibenthic sledges between March 1975 and April 1985. Macrourid fishes were numerically dominant at both stations with Coryphaenoides guentheri and Coryphaenoides (Nematonurus) armatus being the most abundant species at M and PS, respectively. In terms of biomass the morid, Antimora rostrata, was dominant at M but C. (N.) armatus was dominant at PS. The only species that showed clear evidence of a seasonal reproductive cycle was C. guentheri. Many species showed no indication of reproducing in the Rockall Trough. The diets of almost all the species are described and considered in relation to the food resources exploited. Investigations on the pelagic and benthic invertebrate faunas at these stations should reveal the extent to which the bottom-living fishes exploit the available resources.     

Recherches sur la situation trophique d'un groupe d'organismes pélagiques (Euphausiacea). III. Potentiel alimentaire du groupe

The position of a group of pelagic organisms among the food webs depends upon (1) its abundance in the biomass; (2) the factors allowing its utilization by predators; among these, the size distribution of animals and their bathymetric repartition appear to prevail. In the equatorial and southtropical Pacific Ocean, euphausiids represent 8% of the total macroplanktonic and micronektonic biomass, i.e., approximately 13 g/1000 m³ wet weight (somewhat less in oligotrophic tropical zones, a little more in the richer equatorial belt); Euphausia diomedae accounts for more than 50% of this biomass. Individuals measuring 9 to 18 mm in total length (4 to 37 mg wet weight) constitute 84% of the whole biomass of the group; the importance of each species in terms of size groups is discussed. Depth distribution is examined at the specific level. By night, 75% of the biomass concentrates in the 0 to 160 m water layer (ca. 10 g/1000 m³ wet weight; main species Euphausia diomedae), 22% between 160 and 300 m (3 g/1000m³ main species Nematoscelis spp.), and 3% (0.3g/1000 m³) in deeper layers. During the day, the only species abundant at depths less than 400 m belong to the genera Stylocheiron and Nematoscelis; specimens smaller than 15 mm and 20 mg remain at depths shallower than 200 m, individuals between 15 and 22 mm (20 to 65 mg) appear around 200 to 400 m, and larger animals are restricted to depths below 400 m.     

Anguilliform larvae collected off North Carolina

The distinctive larval stage of eels (leptocephalus) facilitates dispersal through prolonged life in the open ocean. Leptocephali are abundant and diverse off North Carolina, yet data on distributions and biology are lacking. The water column (from surface to 1,293 m) was sampled in or near the Gulf Stream off Cape Hatteras, Cape Lookout, and Cape Fear, North Carolina during summer through fall of 1999–2005, and leptocephali were collected by neuston net, plankton net, Tucker trawl, and dip net. Additional samples were collected nearly monthly from a transect across southern Onslow Bay, North Carolina (from surface to 91 m) from April 2000 to December 2001 by bongo and neuston nets, Methot frame trawl, and Tucker trawl. Overall, 584 tows were completed, and 224 of these yielded larval eels. The 1,295 eel leptocephali collected (combining all methods and areas) represented at least 63 species (nine families). Thirteen species were not known previously from the area. Dominant families for all areas were Congridae (44% of individuals, 11 species), Ophichthidae (30% of individuals, 27 species), and Muraenidae (22% of individuals, ten species). Nine taxa accounted for 70% of the overall leptocephalus catches (in order of decreasing abundance): Paraconger caudilimbatus (Poey), Gymnothorax ocellatus Agassiz complex, Ariosoma balearicum (Delaroche), Ophichthus gomesii (Castelnau), Callechelys muraena Jordan and Evermann, Letharchus aliculatus McCosker, Rhynchoconger flavus (Goode and Bean), Ophichthus cruentifer (Goode and Bean), Rhynchoconger gracilior (Ginsburg). The top three species represented 52% of the total eel larvae collected. Most leptocephali were collected at night (79%) and at depths > 45 m. Eighty percent of the eels collected in discrete depth Tucker trawls at night ranged from mean depths of 59–353 m. A substantial number (38% of discrete depth sample total) of larval eels were also collected at the surface (neuston net) at night. Daytime leptocephalus distributions were less clear partly due to low catches and lower Tucker trawl sampling effort. While net avoidance may account for some of the low daytime catches, an alternative explanation is that many species of larval eels occur during the day at depths > 350 m. Larvae of 21 taxa of typically shallow water eels were collected at depths > 350 m, but additional discrete depth diel sampling is needed to resolve leptocephalus vertical distributions. The North Carolina adult eel fauna (estuary to at least 2,000 m) consists of 51 species, 41% of which were represented in these collections. Many species of leptocephali collected are not yet known to have juveniles or adults established in the South Atlantic Bight or north of Cape Hatteras. Despite Gulf Stream transport and a prolonged larval stage, many of these eel leptocephali may not contribute to their respective populations.     

Density surface modelling with line transect sampling as a tool for abundance estimation of marine benthic species: the <Emphasis Type="Italic">Pinna nobilis</Emphasis> example in a marine lake

Density estimation of marine benthic fauna is most often conducted with fishery surveys using dredges or trawls. These estimates are often unreliable due to low and variable efficiency and are inappropriate when dealing with rare or endangered species. In the marine Lake Vouliagmeni, a density surface modelling (DSM) approach using survey data from line transects, integrated with a Geographic Information System (GIS), was used to estimate the population density of the endangered fan mussel Pinna nobilis. This is the first time that such an approach has been applied for a marine benthic species. DSM was beneficial in relation to traditional distance sampling. Apart from providing a more precise total abundance estimate, it related the density of the species to spatial covariates of interest, gave a depiction of the species dispersion in the study area, and provided abundance estimates in any sub-region of the study area. In Lake Vouliagmeni, a marked zonation of P. nobilis distribution was revealed, with the species being restricted in the shallow peripheral zone at depths <22 m. Two density peaks were observed, a major peak at depths between 12 and 13 m and a secondary peak at ∼4 m. A main hotspot of high density was also observed in the northeastern part of the lake. Total abundance of the species was estimated to be 6,770 individuals with a 95% confidence interval of 5,460–8,393 individuals.     

Genetic diversity in two barnacle species, <Emphasis Type="Italic">Chthamalus stellatus</Emphasis> and <Emphasis Type="Italic">Tesseropora atlantica</Emphasis> (Crustacea,Cirripedia), with different larval dispersal modes in the archipelago of the Azores

ISSRs (Inter Simple Sequence Repeats) were employed to compare the genetic structure of Chthamalus stellatus and Tesseropora atlantica in the Azores. The two barnacles differ as regards life cycle: the former conducting pelagic life for about 22 days, the latter for only 24 h. Thirty individuals of each species were analysed from four locations of three Azorean islands. Five ISSR primers produced, respectively, 117 and 79 polymorphic bands in C. stellatus and T. atlantica. Estimates of among-samples genetic diversity suggested extensive connectivity in the former species and isolation in the latter. AMOVA further supported these results by attributing 2% of genetic variance to the among-islands component of C. stellatus and 30% to T. atlantica. Results are consistent with expectations based on species life history and corroborate the importance of pelagic stages in determining the degree of genetic structuring in benthic marine invertebrates.     

Dispersal of phytoplanktotrophic shipworm larvae (Bivalvia: Teredinidae) over long distances by ocean currents

Shipworms or Teredinidae may be dispersed either as adults in floating wooden objects or as pelagic larvae drifting near the sea surface. Five shipworm species, i.e., half of those having an amphi-Atlantic geographical distribution, are known also to have pelagic phytoplanktotrophic larvae which can be carried by ocean currents. From a series of 742 plankton samples taken from throughout the temperate and tropical North Atlantic Ocean, it can be shown that shipworm larvae are not uncommon in the open sea. Teredinid veligers were found in 19% of all samples taken. One species of larvae, identical in all details to that described by Rancurel (1965), is particularly prevalent and is tentatively identified as Teredora malleolus (Turton). A definitive identification will be possible only after the pelagic larvae of the other Atlantic species are known. The larvae of Teredora malleolus are found throughout the North Atlantic Gyre and the adjacent temperate and tropical seas, and from scattered records in the South Equatorial Current. Larvae of other unidentified Teredinidae species were also found. The distance that larvae may be transported depends upon the length of pelagic larval development and the velocity of the currents. From the known current velocities it can be shown that, even in a few weeks, larvae may be dispersed many hundreds of kilometers. The geographical distribution of shipworm larvae suggests that they are carried along the coasts of continents and even across ocean basins, and that this dispersal must be an important factor in the geographical distribution of the adult forms and in the maintenance of genetic continuity between populations otherwise isolated from one another.Contribution No. 2555 from the Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA     

Diets of the demersal fishes on the shelf off Iwate,northern Japan

Diets of demersal fishes were determined on the shelf (ca. 130 m deep) off Iwate, Japan. Samples were taken in three different types of habitat, an artificial reef (AR) site, a natural reef (NR) site, and sandymud bottom (SB) site, from May 1987 to September 1991, mostly every two months. A total of 67 prey items were recognized in the stomachs of 45 predator fish species. The most important preys were the pelagic fishes Sardinops melanostictus and Engraulis japonicus, which comprised 37% wet wt of the overall stomach contents. The percentage of pelagic fishes was highest at AR site, where fish density was highest. The dominant ten species could be divided into five feeding types. The pelagic fish feeders Physiculus maximowiczi and Gadus macrocephalus fed mainly on S. melanostictus. The dietary breadth of P. maximowiczi was wide, while that of Gadus macrocephalus was narrow. The pelagic crustacean feeder Theragra chalcogramma mostly consumed Themisto japonica and euphausiids and showed the least dietary overlap with other fishes. Benthic fish feeders were Hemitripterus villosus and Liparis tanakai. The benthic crustacean feeders Alcichthys alcicornis and Hexagrammos otakii consumed benthic crustaceans as well as pelagic and benthic fishes and showed the largest dietary breadth. The benthic invertebrate feeders Gymnocanthus intermedius, Dexistes rikuzenius and Tanakius kitaharai fed mainly on polychaetes and benthic crustaceans. But Gymnocanthus intermedius consumed a significant proportion of pelagic fishes. Ontogenetic dietary shift was recognized for these fishes. Pelagic fishes were consumed more intensively by larger individuals, especially true of A. alcicornis, Theragra chalcogramma and Gadus macrocephalus. Predominancy of the two most adundant species, P. maximowiczi and A. alcicornis, may be supported by their wide dietary breadth and the significant proportion of pelagic fish in their diets. Interspecific dietary overlap was low in most cases suggesting that food resources were well partitioned, although some high overlap was observed among the pelagic fish feeders, A. alcicornis, and Gymnocanthus intermedius, and among the benthic invertebrate feeders. Interspecific competition seemed more likely in the benthic invertebrate feeders than in the pelagic fish feeders partly because of superabundance of the pelagic prey S. melanostictus.     

Population genetic structure of escolar (<Emphasis Type="Italic">Lepidocybium flavobrunneum</Emphasis>)

Escolar (Lepidocybium flavobrunneum) is a large, mesopelagic fish that inhabits tropical and temperate seas throughout the world, and is a common bycatch in pelagic longline fisheries that target tuna and swordfish. Few studies have explored the biology and natural history of escolar, and little is known regarding its population structure. To evaluate the genetic basis of population structure of escolar throughout their range, we surveyed genetic variation over an 806 base pair fragment of the mitochondrial control region. In total, 225 individuals from six geographically distant locations throughout the Atlantic (Gulf of Mexico, Brazil, South Africa) and Pacific (Ecuador, Hawaii, Australia) were analyzed. A neighbor-joining tree of haplotypes based on maximum likelihood distances revealed two highly divergent clades (δ = 4.85%) that were predominantly restricted to the Atlantic and Indo-Pacific ocean basins. All Atlantic clade individuals occurred in the Atlantic Ocean and all but four Pacific clade individuals were found in the Pacific Ocean. The four Atlantic escolar with Pacific clade haplotypes were found in the South Africa collection. The nuclear ITS-1 gene region of these four individuals was subsequently analyzed and compared to the ITS-1 gene region of four individuals from the South Africa collection with Atlantic clade haplotypes as well as four representative individuals each from the Atlantic and Pacific collections. The four South Africa escolar with Pacific mitochondrial control region haplotypes all had ITS-1 gene region sequences that clustered with the Pacific escolar, suggesting that they were recent migrants from the Indo-Pacific. Due to the high divergence and geographic separation of the Atlantic and Pacific clades, as well as reported morphological differences between Atlantic and Indo-Pacific specimens, consideration of the Atlantic and Indo-Pacific populations as separate species or subspecies may be warranted, though further study is necessary.     

Optimal Marking of Threatened Species to Balance Benefits of Information with Impacts of Marking

Abstract: Marking animals so that they are uniquely identifiable provides information that may assist conservation efforts. Nevertheless, some methods used to mark animals can be harmful. We used mathematical methods to assess the trade‐off between the impact of marking threatened species and the value of the information gained. We considered the case where 2 management strategies, each aiming to improve a species' survival rate, are implemented in an experimental phase. The results of the experiment were applied in a postexperimental management phase. We expressed the expected number of survivors in both phases mathematically, accounting for any mortality caused by the experiment, and determined the proportion of animals to mark to maximize this number. The optimal number of animals to mark increased with the number of individuals available for the experiment and with the number of individuals to be managed in the future. The optimal solution was to mark only 25% of the animals when there were 1000 individuals available for the experiment, the results were used to manage 2000 individuals, and marking caused mortality of 1%. Fewer animals were marked when there were fewer animals in either phase or when marking caused higher mortality. In the case of the Helmeted Honeyeater (Lichenostomus melanops cassidix), the optimal proportion to mark was <1 if the mortality rate was >0.15%–1%, with the threshold depending on the number of animals in the experimental and postexperimental phases. The trade‐off between gaining more information about a species and possibly harming individuals of that species by marking them is difficult to assess subjectively. We show how to determine objectively the optimal proportion of animals to mark to enhance the management of threatened species.     

The stomach contents of post-hatchling green and loggerhead sea turtles in the southwest Pacific: an insight into habitat association

Dietary information obtained from stomach contents can provide a wealth of information on an animal’s ecology. Where animals are cryptic, such as the post-hatchling life history stage of a sea turtle, the ecological insight that dietary analyses can provide, may be otherwise unobtainable. Investigations into post-hatchling turtle stomach contents have found planktonic organisms, dominated by pelagic molluscs and crustaceans, hydrozoans, Sargassum and fish eggs. The nature of these dietary organisms provides evidence for the widely accepted hypothesis that, with the exception of the flatback turtle (Natator depressus), the post-hatchling stage of a sea turtle’s life history is pelagic and oceanic. As the majority of studies that have investigated the stomach contents of post-hatchling sea turtles have been conducted on loggerhead turtles (Caretta caretta) in the northern Atlantic and Pacific Oceans, insight derived from dietary investigations into post-hatchling ecology is biased. This study investigates the diet of post-hatchling green turtles (Chelonia mydas) and loggerhead turtles in the southwest Pacific Ocean. Stomach contents were obtained from 55 green and loggerhead post-hatchling turtles that had stranded or been consumed by Coryphaena hippurus. Our findings demonstrate that loggerhead and green post-hatchlings in the southwest Pacific share similar feeding ecology and feed on a variety of neustonic items that are indicative of an oceanic and pelagic existence. The dietary items consumed by both species investigated belong to similar taxonomic groups as those found in previous studies with species level distinctions occurring owing to the different geographical location.     

<Emphasis Type="Italic">Tiburonia granrojo</Emphasis> n. sp., a mesopelagic scyphomedusa from the Pacific Ocean representing the type of a new subfamily (class Scyphozoa: order Semaeostomeae: family Ulmaridae: subfamily Tiburoniinae subfam. nov.)

Submersible observations off Japan, Hawaii, and California, USA, at depths of 645–1497 m, have revealed a previously undescribed species of large semaeostome scyphomedusa. These observations were made from 1993 to 2002. The medusa, Tiburonia granrojo n. sp. is sufficiently different from other species in the family Ulmariidae to justify the creation of a new subfamily (Tiburoniinae). This subfamily and species are distinct in overall bell morphology and color, lacking any marginal tentacles, and having four to seven short, thick oral arms that extend beyond the bell margin. The entire medusa, including the mesoglea, is a deep red. A new key to the subfamilies of the Ulmaridae and large subunit rRNA sequence information for T. granrojo are provided. That new species of this size and mass are still being discovered in the deep waters of the world suggests that deep-water species remain undescribed. Additional information is available at http://www.mbari.org/midwater     

Phylogeography of the Southwestern Atlantic menhaden genus <Emphasis Type="Italic">Brevoortia</Emphasis> (Clupeidae,Alosinae)

Among pelagic fish, the Southwestern Atlantic menhaden genus Brevoortia (Clupeidae, Alosinae) constitutes an important species model to investigate the patterns of genetic differentiation. It is abundant in the Río de la Plata estuary and in the Atlantic coastal lagoons system from Uruguay and Southern Brazil. To access in the taxa discrimination and population structure in Brevoortia we perform a phylogeographic approach based on mitochondrial cytochrome b (cyt-b) sequences including 240 individuals from 16 collecting sites. Among the 720 bp cyt-b sequenced, 199 correspond to variables and 88 to phylogenetically informative sites. High values of haplotype diversity (h = 1.000) and nucleotide diversity (π = 0.061), as well as an average of 0.084 polymorphic segregating sites and 46 different haplotypes were found. Maximum likelihood analysis based on the GTR + I + G model and Bayesian inference strongly support the idea that B. aurea is the only species of the genus inhabiting the Southwestern Atlantic region. Our analyses revealed a complex population pattern characterized by the existence of long-term highly structured genetic assemblages of mixed stocks. Each monophyletic entity included individuals from different collecting sites, different age groups and collected in different years. Our data also suggest that the recruitment of unrelated mtDNA haplotypes carried out by individuals within schools could be occurring in the same nursery areas revealing the existence of many different maternal lineages. A scenario where different simultaneously and successively mixed mtDNA lineages remain historically connected through basal haplotypes among different clades could explains more accurately the complex and ordered metapopulation dynamic found in this pelagic fish.     

Ciliated epibionts on the Arctic sympagic amphipod<Emphasis Type="Italic"> Gammarus wilkitzkii</Emphasis> as indicators for sympago–benthic coupling

In September 2003 specimens of the sympagic amphipod Gammarus wilkitzkii were sampled in drifting pack ice above 50 m water depth and in the pelagic/benthic environment beneath in the coastal waters off Svalbard (Norway). Abundance values ranged between 1.5 and 8 individuals m^–2 for the pelagic/benthic and the sympagic environments, respectively, and showed corresponding sex ratios of 1:1.4, favoring males. In the ice a significantly higher number of juveniles prevailed. In contrast, ovigerous females were more abundant among pelagic/benthic living specimens. Approximately 25% of the individuals hosted ciliated epibionts of the genera Ephelota, Cryptacineta, Acineta, Podophrya (all suctoria), and Epistylis (peritrichia). Cryptacineta and Ephelota were the most abundant epibionts on this amphipod species. Female specimens of G. wilkitzkii showed the highest degree of infestation (>2,100 individual epibionts per amphipod specimen: indE/A) followed by juveniles (>1,200 indE/A) and males (>220 indE/A). Highest densities of epibionts were found on anterior body parts with the antennae bearing up to 130 individuals. This is the first sighting of epibionts on crustacea from the sympagic environment. We interpret them as biomarkers that indicate the existence of sympago–benthic coupling processes between the ice and the underlying waters and the seafloor. The population structure and the proportion of infested specimens are equal for the amphipods sampled from both the sympagic and the pelagic/benthic environment, indicating the existence of exchange (coupling) processes between the two habitats. Considering the annual ice cycle, local ice drift patterns, and the shallow water depth in the sampling area, we hypothesize that ice amphipods spend ice-free periods near the seafloor where they may serve as basibionts for protozoans and eventually re-colonize the ice with the onset of ice formation. Our observations strongly emphasize that shallow coastal areas serve as both retention (rather than sink) areas for ice fauna during ice-free periods, and as stepping-stones for re-colonizing the ice when the ice is formed in winter.Communicated by M. Kühl, Helsingor