Food-web traits of the North Aegean Sea ecosystem (Eastern Mediterranean) and comparison with other Mediterranean ecosystems

Tsagarakis, Konstantinos; Coll, Marta; Giannoulaki, Marianna; Somarakis, Stylianos; Papaconstantinou, Costas; Machias, Athanassios

doi:10.1016/j.ecss.2010.04.007

Cited by 97 publications

(163 citation statements)

References 70 publications

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“…It is important to highlight the possible effect of the mixture of Levantine Intermediate Water and Black Sea Water between 20 and 100 m depth in the northeastern Aegean Sea, where high nutrient concentration and production in the upper layers has been described (Pazi 2008). This high productivity can increase the abundances of small pelagics, which have been identified as the main trophic source of M. merluccius in this area (mainly sardine and anchovy, Tsagarakis et al 2010, Harmelin-Vivien et al 2012. Moreover, the spill over from the nearby protected area in Saros Bay, where bottom trawling has been banned since 1993, could also increase the abundance of M. merluccius.…”

Section: Discussionmentioning

confidence: 99%

Preliminary evaluation of landings and discards of the Turkish bottom trawl fishery in the northeastern Aegean Sea (eastern Mediterranean)

Keskin¹,

Ordines²,

Ateş³

et al. 2014

Sci. Mar.

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Summary: This short-term study on commercial discards was carried out in fishing grounds around Gökçeada Island in the northeastern Aegean Sea, a geographic area where fisheries information is rather limited. A total of 28 bottom trawls were performed between 70 and 410 m depth from December 2009 to February 2010. All the samples were collected on board a commercial trawler under commercial fishing conditions. A total of 3143 kg of biomass was caught in 28 valid hauls. Landings accounted for about 67% of the total catch while the remaining 33% was discarded. Fish species comprised 85% of the total catch and their composition could be divided into four main groups related to depth: shallow shelf (70 to 88 m), deep shelf (155 to 180 m), shelf break (196 to 276 m), and upper slope (307 to 410 m). Fish dominated the abundance and biomass of both landings and discards in all bathymetric strata. Echinoderms also accounted for a large proportion of the discards. Mean total catches varied between 78.4 kg/h on the shallow shelf and 38.1 kg/h on the shelf break with no differences in the landing biomass between groups, but with slightly higher discards over the shallow shelf. Taking into account the preliminary nature of the findings, based on a short-term analysis, the minimum mesh size and minimum landing size currently applied in the Turkish bottom trawl fishery are not sufficient to reduce discards and to protect juveniles of commercially important species in the northeastern Aegean Sea.Keywords: bottom trawl; catch composition; landings; discards; length-frequency; eastern Mediterranean. Evaluación preliminar de los desembarques y descartes de la pesquería de arrastre de fondo de Turquía en el mar Egeo nororiental (Mediterráneo oriental)Resumen: Este estudio a corto plazo sobre los descartes de la flota comercial de arrastre se llevó a cabo en las zonas de pesca alrededor de la isla Gökçeada en el noreste del mar Egeo, una zona geográfica en la que la información sobre las pesquerías es bastante limitada. Se realizaron un total de 28 pescas de arrastre de fondo entre 70 y 410 m de profundidad de diciembre 2009 a febrero de 2010. Todas las muestras se recogieron a bordo de un embarcación de pesca de arrastre siguiendo las mismas condiciones de pesca comercial. Se capturaron un total de 3143 kg de biomasa en 28 lances válidos. Los desembarques comerciales representaron alrededor del 67% de la captura total, mientras que el resto (33%) se descartó. El 85% de la captura total estuvo compuesta por especies de peces. La composición específica se pudo separar en cuatro grupos principales relacionados con la profundidad : la plataforma poco profunda (70 a 88 m), la plataforma profunda (155-180 m), el borde inferior de la plataforma (196 a 276 m) y el talud superior (307-410 m). Los peces dominaron la abundancia y biomasa tanto de los desembarques comerciales como de los descartes en todos los estratos batimétricos. Además los equinodermos también fueron un grupo importante de los descartes. La media de las capturas totales v...

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Section: Discussionmentioning

confidence: 99%

Preliminary evaluation of landings and discards of the Turkish bottom trawl fishery in the northeastern Aegean Sea (eastern Mediterranean)

Keskin¹,

Ordines²,

Ateş³

et al. 2014

Sci. Mar.

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“…Considering the seasonal succession of the plankton community, the ciliates are efficient predators of phytoplankton (Schweizer, 1997;Pauleto et al, 2009). Ciliates are the main grazers of phytoplankton since mesozooplankton is unable to consume small-sized cells belonging to the pico-and nano-fractions, which dominate in oligotrophic environments (Siokou-Frangou et al, 2002;Tsagarakis et al, 2010). Ciliates also serve as a link between the microbial loop and the classical food-web, and contribute significantly to the transfer of energy to higher predators (Pitta et al, 2009).…”

Section: Composition Of the Ciliate Communitymentioning

confidence: 99%

Space-time variation of ciliates related to environmental factors in 15 nearshore stations of the Gulf of Gabes

et al. 2014

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Diversity and structure of ciliate communities in the Gulf of Gabes (Tunisia) were investigated based on a survey of 15 nearshore stations along 237 Km, by monthly sampling over a year. Ciliated protozoa were identified to genus and/or species level and enumerated. Statistic tools were used to explain ciliate assemblage. High ciliate species richness from 63 taxa was recorded, including new records of several species. This study showed a longitudinal distribution of ciliate communities, which are organized at northern (from Tabia to Port of Gabes) and southern stations (from Zarrat to Jabiat Haj Ali). The number of taxa increased significantly at northern stations but decreased at the southern ones. This distribution was mainly influenced by salinity and phytoplankton abundance. Ciliate taxa were grouped into five size-classes: 15-30 µm, 30-50 µm, 50-100 µm, 100-200 µm and >200 µm. In terms of abundance, most abundant size groups were small ciliates (15-30 μm), accounting for 15 to 79 %, while the greatest biomass contribution came from the 50-100 μm size classes. Thus, we conclude that there is a high diversity of ciliate communities with a geographical distribution that is influenced by abiotic and biotic factors along the coast of the Gulf of Gabes.

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“…IgnaIgnatiades et al (2002) reported that phytoplankton population structure and dynamics are influenced by the different hydrographic conditions in the area, and picoplankton predominated during spring and late summer, accounting for more than 50% of Chl-α. Previous studies in the area have underlined the strong impact of this frontal structure on the zooplankton community (Isari et al, 2006;Zervoudaki et al, 2006;Siokou-Frangou et al, 2009;Siokou et al, 2013) and fisheries productivity (Tsagarakis et al, 2010). A large part of the fixed carbon is channelled through the microbial food web (Siokou-Frangou et al, 2002;Zervoudaki et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Temporal variability of the microbial food web (viruses to ciliates) under the influence of the Black Sea Water inflow (N. Aegean, E. Mediterranean)

et al. 2014

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Τhe entire pelagic microbial food web was studied during the winter-spring period in the frontal area of the North Aegean Sea. Abundance of viruses, heterotrophic bacteria, cyanobacteria, auto- and hetero-trophic flagellates, and ciliates, as well as bacterial production, were measured at three stations (MD1, MD2, MD3) situated along a N-S transect between the area directly influenced by the inflowing Black Sea water and the area covered by the Levantine water. Samples were collected in December 2009, and January, March, April, and May 2011. Station MD1 exhibited the highest values of abundance and integrated biomass of all microbial groups and bacterial production during all months, and MD3 the lowest. Bacteria dominated the total integrated biomass at all stations and months, followed by cyanobacteria, auto-, hetero-trophic flagellates and ciliates. On a temporal scale, the microbial food web was less important in March as all microbial parameters at all stations showed the lowest values. After the phytoplankton bloom in March, the heterotrophic part of the microbial food web (mainly) strongly increased, though the intensity of the phenomenon was diminished from North to South. Pico-sized plankton was found to be heterotrophic whereas nanoplankton was autotrophic. It seems that the influence of the Black Sea water on station MD1, permanent throughout the study period of early winter to late spring, was reflected in all microbial populations studied, and produced a more productive pelagic food web system, with potential consequences for the upper trophic levels.

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Food-web traits of the North Aegean Sea ecosystem (Eastern Mediterranean) and comparison with other Mediterranean ecosystems

Cited by 97 publications

References 70 publications

Preliminary evaluation of landings and discards of the Turkish bottom trawl fishery in the northeastern Aegean Sea (eastern Mediterranean)

Preliminary evaluation of landings and discards of the Turkish bottom trawl fishery in the northeastern Aegean Sea (eastern Mediterranean)

Space-time variation of ciliates related to environmental factors in 15 nearshore stations of the Gulf of Gabes

Temporal variability of the microbial food web (viruses to ciliates) under the influence of the Black Sea Water inflow (N. Aegean, E. Mediterranean)

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