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The use of pots in the north Atlantic finfish fisheries is negligible because this fishing method typically has a low capture efficiency. Large numbers of individuals encounter baited pots, but the proportions of fish that enter the pot and become caught are low. Krill, which constitutes an important prey for cod (Gadus morhua), is attracted by light. The catching efficiency of baited cod pots with three light sources with different colours and intensities (white: 9744 mW m−2, white: 23 mW m−2, green: 8 mW m−2) were tested in coastal waters in northern Norway. Pots with the light source of highest intensity gave a 17 times higher catch rate of cod than that of control pots (with bait only). The light source of medium intensity gave about a five times higher catch rate, whereas the weakest light did not influence the catch. Cod caught in pots with light had more krill and arrowworms in their stomach and were observed feeding on these preys inside the pot. We concluded that light sources of increasing intensity attract more krill, and that cod were attracted into the pot by the dense swarms of prey and not the light per se. [ABSTRACT FROM AUTHOR]

Until recently many oceanic zooplankton species have been considered as cosmopolitan organisms. At present it became evident that some of them comprise many distinct molecular operational taxonomic units (MOTUs) that often are regarded as cryptic species. As they can significantly change our perceptions of large-scale biogeographic patterns, it is important to characterize the true diversity within common and ecologically important groups. We have analysed the molecular and morphological diversity of the cosmopolitan mesopelagic chaetognath Pseudosagitta maxima throughout the Atlantic Ocean from 60° S to 85° N and its position within the genus Pseudosagitta. Three distinct mitochondrial clades within P. maxima were revealed with phylogenetic analyses (Maximum Likelihood, Bayesian Inference) and were geographically separated. The subsequent analyses of nuclear markers (H3, ITS1) have shown that P. maxima most likely comprises two distinct MOTUs, tropical and bipolar, that also have some morphological differences. The latter MOTU consists of two genetically slightly divergent populations: southern and northern. The morphological examination allowed the determination of a character (type of hook coloration) that accurately distinguishes juveniles of the P. maxima complex from the other congeneric species. Molecular data have shown that evolutionary P. lyra and P. gazellae are more closely related to each other than to P. maxima. Number of hooks, number of anterior and posterior teeth and the arrangement of ova in the ovary were proposed to be the most useful morphological characters to distinguish between tropical and bipolar MOTUs within the P. maxima complex. The first three characters should be determined for each maturity stage separately. [ABSTRACT FROM AUTHOR]

A real-time PCR based method involving a species-specific probe was applied to detect Engraulis encrasicolus eggs predation by the macrozooplankton community during the 2011 spawning season. Three locations along the shelf break presenting contrasting but high prey densities were sampled. A total of 840 individuals from 38 taxa of potential macrozooplankton predators were assayed for E. encrasicolus DNA presence and 27 presented at least one positive signal. Carnivorous copepods were responsible for the most predation events (66%) followed by euphausiids (16%), chaetognaths (5%), and myctophid fish (4%). Macrozooplankton predation on anchovy eggs followed a type-I functional response with daily mortalities <4% of available prey abundance suggesting a negligible impact on the species recruitment at the shelf break spawning centre. [ABSTRACT FROM AUTHOR]

Noblezada, M. M. P., and Campos, W. L. 2012. Chaetognath assemblages along the Pacific Coast and adjacent inland waters of the Philippines: relative importance of oceanographic and biological factors. – ICES Journal of Marine Science, 69: 410–420.When studying plankton distribution, it is necessary to investigate the biology of the target organisms and the surrounding physical environment. Station and species groupings are only useful if they provide insight into the environmental associations of the species in the group. The study covers two geographic regions: the Pacific Coast (Bicol Shelf) and inland waters (San Bernardino Strait, Ticao Pass, Sibuyan, and Visayan Seas) of the Philippines. Comprehensive information is provided on chaetognath assemblages and distribution within the regions. The findings are integrated with oceanographic conditions and phenomena that define the characteristics of the subareas and consideration given to how these conditions affect chaetognath ecology. A comparison is also provided of the community structure of the two regions, and the possible use of chaetognaths as indicator species of water mass movement and oceanographic phenomena explored. In all, 28 284 specimens were examined, and 33 species from 17 genera were identified. Chaetognath distributions, abundance, and community structure were analysed using dissimilarity indices and multiple regression. The results show that the distribution of chaetognaths agrees well with the movement of oceanic water from the Pacific into the central part of the archipelago. [ABSTRACT FROM PUBLISHER]

Noblezada, M. M. P., and Campos, W. L. 2008. Spatial distribution of chaetognaths off the northern Bicol Shelf, Philippines (Pacific coast). – ICES Journal of Marine Science, 65: 484–494.The composition, abundance, and distribution of chaetognaths off the northern Bicol Shelf, Philippines (Pacific coast), from 31 stations along transects perpendicular to the coast were analysed. Samples were collected in April, 2001. In all, 26 species belonging to 14 genera were identified. Flaccisagitta enflata was the most abundant and frequently captured species at all stations, and constituted 41.9% of the total specimens. Most of the smallest diversity values were observed from areas affected by upwelling, although the greatest densities were observed at stations located within the upwelling zones. The occurrence of mesopelagic and bathypelagic species (Decipisagitta decipiens, Caecosagitta macrocephala, and Eukrohnia fowleri), in samples collected from upper water layers, could be explained by vertical transport caused by upwelling. [ABSTRACT FROM PUBLISHER]

The life cycle of Sagitta friderici, a neritic species from Pacific, Atlantic, and Mediterranean waters, has been poorly studied. Aiming at increasing our knowledge of this species in the Argentine Sea, the size structure, dry weight, distribution of maturity stages (ovarian, testicular, and seminal vesicles development), and life-cycle duration were studied from samples obtained at a permanent station (EPEA STATION, 38°28′S 57°41′W) from 9 March 2000 to 10 April 2001. The almost permanent presence of juveniles and the extended period during which mature adults (stage III) were detected suggest that reproduction occurs continuously with two main peaks, the main one in the summer (December–February) and a lesser one in the fall (April–May). Significant (p<0.05) inverse correlations between water temperature and the mean size of stages 0 (juveniles), I, and II were found in this data set. Owing to the influence of temperature, those individuals that develop during the warm season and mature in the fall attain smaller sizes (7.6–12.4 mm) than those that develop during the coldest period of the year and mature in the spring (10.0–15.2 mm). The life-cycle duration is approximately 15 months, and the growth rate ca. 0.03 mm d-1. The weight increase as a function of individual size was similar in the fall and in the spring (Fisher Test, p>0.05). [Copyright &y& Elsevier]

Fuzzy classification was used to analyse hydroacoustic survey data (Sv, an acoustic volume backscattering strength index of biomass) and oceanographic data (temperature, salinity, water density, and chlorophyll a fluorescence) collected from the waters of the southern East China Sea off northeastern Taiwan. Four types of water masses were identified. Type A water mass corresponded to warm continental-shelf mixed water and had a high acoustic volume backscatter (Sv>−59.37 dB). Type D corresponded to cold upwelling Kuroshio subsurface water with Sv<−65.24 dB, i.e. about 6 dB lower than that of Type A. Type B and C waters were intermediate between Type A and D waters. Twenty-two IKMT (net) samples were taken, and their estimated biomasses showed a significant relationship to corresponding average Sv values. Copepoda were most dominant in the zooplankton community. Decapoda, appendicularia, and chaetognatha were abundant in Type A waters, and proportionally rarer in the other three types of water masses. Conversely, the percentage contribution made by ostracoda and gastropoda was greater in Type D waters than in Type A waters. The combination of IKMT net sampling and hydroacoustic measurements was found to be useful for assessing the biomass distribution and species composition of zooplankton. We also conclude that the fuzzy classification method used here can usefully be applied to hydroacoustic data for the classification and identification of water masses and zooplankton composition in the ocean, particularly in an upwelling area. [ABSTRACT FROM PUBLISHER]

The chaetognaths Sagitta enflata, S. serratodentata atlantica and S. bipunctata were caught in six sampling periods from September 1988 until July 1989 during both day and night in Kisamos Gulf (Cretan Sea, Eastern Mediterranean) in the upper layers (0–50 m). Gut content analysis showed that copepods were the predominant food organisms in the diet of these three predators. Positive electivity indices were found for Corycaeus spp. and Oncaea spp. but negative for Clausocalanus spp. copepodites and Clausocalanus furcatus females, which were the most numerous among copepods. Cannibalism was observed mainly in S. bipunctata while S. serratodentata atlantica was found to be less cannibalistic. The size of the predator was reflected in the size of prey. Feeding intensity indicated by Food containing ratio (FCR) and Number of prey per chaetognath (NPC) increased just before the reproductive period of each chaetognath species. Differences between day and night feeding were only found in S. enflata. [ABSTRACT FROM PUBLISHER]