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Опыт выращивания сеголетков пиленгаса Planiliza haematocheila в поликультуре с сазаном Cyprinus carpio в пресноводных прудах
No full textThe results of the experiment on the rearing of so-iuy mullet fingerlings in polyculture with the European carp in the ponds with decreased mineralization, which has been conducted at the facilities of Rogozhkino Fish Farm, are presented. The so-iuy mullet juveniles were obtained artificially in a hatchery of the research facility “Zavetnoe” and reared on artificial feeds of two different formulations. In the first mode of rearing, the average weight of juveniles was 1.68 g, and in the second one it was 3.49 g. At the further stages, the juveniles were separated into different ponds based on the feeding mode. The juveniles in these ponds were reared under the controlled hydrochemical and hydrobiological conditions. The species composition of the zooplankton community was typical for pond ecosystems. In the experimental ponds, the biomass of the zooplankton on which the juveniles fed was low—2.2 g/m3 on average. Dietary analysis of the so-iuy mullet juveniles has shown that the detritus content in a food bolus was no less than 30 %. The dynamics of cultivation, biological, physiological, and biochemical parameters of the juveniles have been identified for different modes of rearing. The result obtained with the first mode of rearing was positive; growth characteristics and physiological status of the juveniles were on the normal level for the individuals of such age growing in natural water bodies. The quality and growth rate of the so-iuy mullet juveniles reared in the second mode were satisfactory; total lipid content in the tissues was relatively low. These results reveal the possibility of rearing healthy so-iuy mullet juveniles in fresh water. It is conducive to stock the freshwater bodies with the fingerlings which weight does not exceed 3–4 g; the juveniles of higher weight gain reared on artificial feeds adapt to the aquatic environment of a water body after their transition to the natural feed considerably longer.Представлены результаты эксперимента по выращиванию молоди пиленгаса в прудах с пониженной минерализацией в поликультуре с сазаном, проведенного на базе Рогожкинского рыбоводного завода. Молодь пиленгаса была получена заводским способом на НИБ «Заветное», при ее подращивании применяли искусственные корма двух разных рецептур. В первом варианте подращивания средняя масса молоди составляла 1,68 г, во втором — 3,49 г. В дальнейшем молодь была рассажена в разные пруды с учетом вариантов кормления. Процесс выращивания молоди в прудах сопровождался контролем гидрохимических и гидробиологических условий. Видовой состав зоопланктонного сообщества был типичным для прудовых экосистем. В экспериментальных прудах биомасса кормового зоопланктона была невысокой и в среднем составляла 2,2 г/м3. Анализ питания молоди пиленгаса показал, что в пищевом комке содержание детрита составляло не менее 30 %. Определена динамика рыбоводно-биологических и физиолого-биохимических параметров молоди в разных вариантах выращивания. Положительный результат был получен в первом варианте выращивания: ростовые характеристики и физиологическое состояние молоди соответствовали норме для рыб этого возраста из естественных водоемов. Темп роста и качество молоди пиленгаса при втором варианте выращивания были удовлетворительными, а содержание общих липидов в тканях — сниженным. Полученные результаты свидетельствуют о возможности выращивания полноценной молоди пиленгаса в пресной воде. Зарыбление пресноводных водоемов лучше осуществлять сеголетками массой не более 3–4 г, поскольку молодь большей навески, подращиваемая на искусственных кормах, дольше адаптируется к условиям водоемов при переходе на питание естественным кормом.PublishedReferee
Оценка эффективности нереста речного окуня (Perca fluviatilis L.) в Куйбышевском водохранилище
No full textThis article identifies the factors affecting the efficiency of its spawning in modern conditions of the Kuibyshev Reservoir, based on data on the number of perch larvae.В данной работе на основе данных по численности личинок окуня выявлены факторы, влияющие на эффективность его нереста в современных условиях Куйбышевского водохранилища.PublishedNon Referee
Evaluation of the fishing effort and catch regime for demersal fisheries in the western Mediterranean Sea – PART IX (STECF-22-11)
No full textCommission Decision of 25 February 2016 setting up a Scientific, Technical and Economic Committee for Fisheries, C(2016) 1084, OJ C 74, 26.2.2016, p. 4–10. The Commission may consult the group on any matter relating to marine and fisheries biology, fishing gear technology, fisheries economics, fisheries governance, ecosystem effects of fisheries, aquaculture or similar disciplines. This report is the ninth of a suite of STECF EWG reports dedicated to the evaluation of the implementation of the Western Mediterranean Sea Multi-Annual management Plan (hereafter, MAP), following EWG reports 18-09, 18-13, 19-01, 19-14, 20-13, 21-01, 21- 13, 22-01. The group was requested to implement mixed fisheries bio-economic models to run a number of scenarios up to 2030 with varying parameters, to evaluate a fishing effort reductions for trawlers, longliners and netters in association to vessel number reductions for trawlers, increase in mesh size for trawlers, existing closure areas and catch limits for deep water shrimps (ARA and ARS) through five scenarios and draft a mixed fisheries advice. For all mixed fisheries models applied during the EWG (TOR 3), the data from the DCF official data calls and from the western Mediterranean stock assessments, were updated using data from EWG 22-09 (Western Mediterranean stock assessments) and EWG 22-10 (FDI datacall). The same set of updated data were also used to answer TOR 1 and TOR 2. The exploration of effort data time series (TOR 1) highlighted that in GSA7 the French OTB fleet >18m showed a decrease in fishing days counteracted by an increase of the corresponding fleet segments of French OTT which could be potentially due to a shift in gear use, although experts did not suggest specific causes that would drive this shift. The comparison of fishing days for trawlers (OTB, OTM, OTT, PTB, PTM and TBB as per EU regulation 2019/2236) declared in the FDI official datacall and reported in the 2020 and 2021 regulations were reported this year as well. Discrepancies were found also between 2021 data and the 2021 regulation (as per 2020) with the values reported in the regulation being always higher (for all countries but not for all fleet segments) than the values declared in the FDI datacall. Results suggest that effort is decreasing faster than the regulation for most fleet segments and that the reference period 2015-2017 might not be representative anymore of the effort dynamics of the last few years. For Spain and Italy reductions by 2021 are suggested to be higher than the expected reduction by 2022, while this does not happen for France. From the data quality checks very minor issues were highlighted and there was no reporting in the DTMT of these issues. EWG 22-11 would like to ask for clarifications to MSs concerning the association of gear type with the upper level of aggregation fishing technique as it was observed that odd matching were found which could undermine the calculation of fishing days in the comparisons with the yearly regulations. Specifically the gear OTB was often found under the PGP fishing technique and experts present at the EWG were not able to explain this match. The estimated F by gear and GSA (TOR2) allowed updating the analysis of the linear relationship between F and E. As in previous years a linear relationship consistent across GSAs and stocks was not found. The HKE, MUT and ARA stocks showed a linear relationship with OTB in some cases. For HKE 1567 the relationship did not hold once observed by GSA (although this could be a modelling artefact from the assessment model) or in EMU 2. MUT showed a linear relationship in GSA 6 and 7 with OTB and OTT (but results for GSA 7 should be taken with caution as there is a very strong variation in F for a lower variation of effort). ARA in EMU 1 by GSA (and on the overall stock 6-7) showed a linear relationship with OTB. No relationship was found for gears as LLS, GTR (except for MUT in 9) or GNS, neither for the stocks of DPS or ARS. EWG 22-11 suggests that running the analysis at metier level would give more meaningful results, although it should be noted that the metier is a very unstable resolution of fisheries, therefore difficult to define as data sources. To the methodological section of models (Section 5) two subsections were added, one on the models behavior during mid and long term projections and one on the relationship between biomass increase and economic gain. All models at the moment are suggested to be used for mid-term projections but not for long-term projections as the population dynamics are led either by stock recruitment relationships (BEMTOOL), which are not robust at the moment due to the nature of the data or led by recruitment stochasticity (IAM, ISIS-Fish and SMART), based on a random resampling of the time series but not accounting for potential environmental effects. This year for EMU 1 new analytical assessments were available to EWG 22-11 such as ARA 5, DPS 1 and DPS 5-6-7. In EMU 2, instead, 2 stocks were lost as it was not possible to have an updated analytical assessment due to data issues for MUT 10 and ARA 8-9-10-11. As ARA is one of the stocks with a catch limit defined by the EU Regulation 2022/110, the limitations due to the lack of assessment for this species when running the models in EWG 22-11, should be noted. Based on the final draft report from EWG 22-09, stock assessment of Western Mediterranean, which will be presented to STECF in November 2022, but has not yet been endorsed by STECF, the EWG observed that in 2020, 94% and, in 2021, 79% of the stocks were not at MSY. In 2022, the EWG shows that 73% of the stocks are not at MSY and 53% remain severely overfished. Some of the stocks could be already responding positively to the MAP measures, although the MAP has been implemented only since 2020 and the data available are only up to 2021. 9 out of 14 assessed stocks have decreasing fishing mortality, however, there are 4 stocks still behind transition to MSY of which two have declining biomass and increasing fishing mortality. Some stocks need particular attention for their low biomass level. EWG 22-09 identified as below the biomass reference point (Blim): Hake in GSAs 1-5-6-7, Hake in GSAs 8-9-10-11 and Blue and red shrimp in GSAs 1-2. In addition, five stocks are also below Bpa. Despite progress towards MSY, high levels of overfishing remains in particular for hake and deep-water shrimps. Models results (Section 6) showed that for EMU 1 (result only from IAM) none of the proposed scenarios (5 scenarios + status quo) achieved the objective of reaching FMSY by 2025. Red mullet in GSA 6 (MUT6) never reaches its Fmsy range during the simulation period (2022-2030) under any scenario, and hake in GSA 1-5-6-7 (HKE1567) is still above Fmsy in 2025. The other stock that is slightly behind the objectives is red mullet in GSA 1 (MUT1) with all scenarios. However, the other stocks (ARA12, ARA5, ARA67, NEP6, MUT7, DPS1 and DPS567) reach their FMSY range in 2025 with scenarios A to D. Only with the status quo scenario (scenario F) the FMSY range is not reached in 2025 for some of those stocks. Globally, all scenarios foresee some important negative economic impact for French and Spanish trawlers in the short and medium term with a decrease in their Gross Value Added. Even with scenario F (i.e. status quo), French trawler GVA is negative from 2022. This is due to the fuel price used in the simulation in 2022 and beyond from AER 2022 projections, where prices increased a lot compared to their initial values. Due to time constraints, it was not possible to have results from the ISIS-Fish model for EMU 1. For EMU 2 the setting of a maximum catch limit on ARA and ARS allows to approach FMSY for ARS, but not for HKE, even when in combination with other measures such as reduction of fishing days and number of vessels and change in selectivity. For ARS 8-9-10-11, NEP 9 and MUT 9 all scenarios implemented allow to reach FMSY in 2025 except for the status quo scenario (F). ARS, ARA and NEP stocks would benefit of all the scenarios, due to the re-allocation of the effort from the deep-water metier (OTB_DWS and OTB_DES) to the demersal (OTB_DES). This reallocation produces an increase in the fishing pressure on demersal fishing grounds, contributing to partly reduce the underutilization of red mullet in GSA 10, red mullet in GSA 9 and Norway lobster in GSA 9, but also increasing the F of hake. The total revenues and gross value added for the overall fleet are predicted to slightly increase with respect to the lowest values of the time series reached in 2020-2021. For scenarios A, B and D total revenues across all fleets will decrease compared to the SQ scenario (F), remaining above the recent values. A similar pattern is observed for gross value added. Simulations on fuel price increase of 120% (of the average fuel price in 2022) in 2023 onwards in EMU 1 showed an exacerbation on the GVA of fleet segments that already suffered from the management implementation. It should be highlighted that already with the "fuel option 1" (with fuel price in 2022 and onwards from AER projections), the economic performances are already negative, especially for French fleets, as the fuel price has strongly increased compared to 2021. Estimations of GVA in 2022, when effort reductions are still quite limited, are already negative suggesting that the negative GVAs are mainly due to the 2022 fuel price peak. In EMU 2 as well the main effect is to observe a lower GVA; specifically, the difference between the best performing scenario, that is B, and the status quo (F) is smaller. Here as well, the increase in fuel costs impacts more importantly on the GVA, compared to the decrease in fixed costs imposed by the effort limitations. For the application of the bio-economic models for the assessment of the development regarding the implementation of the West Med MAP it was decided to follow the methodology of the AER and, therefore, subsidies are not included in the calculations for income. The financial situation which the bio-economic models present for the year 2022 and beyond depend a lot on the assumptions regarding the development of fuel prices but include no mitigation measures for the fishing companies (like de minimis payments to cover parts of the increase in fuel costs 2022). Therefore, the modelling results show a lower level of gross value added compared to the real situation of the fishing companies. EWG 22-11 suggests that from an economic standpoint, it would make sense to conduct a detailed impact assessment (IA) for the further implementation of the West Med MAP. With such an assessment it would be possible to calculate possible scenarios (including possible mitigation and adaptation measures) regarding the implementation of effort reduction and the possible economic performance of the fishing fleets. The EU MSs affected by the management plan could then discuss possible mitigation and adaptation measures for the fishing sector. As such an IA is not requested by the West Med MAP it would have not follow the usual procedure within DG Mare and can be limited to assessments within the STECF context. EWG 22-11 concludes that the EWG chair and the STECF bureau should discuss with DG MARE how far such an impact assessment would be possible for the next EWG meeting in March 2023. Concerning economic indicators (Section 7), EWG 22-11 suggests that all the different bio- economic modules should report the same economic indicators and specific reference points should be defined in order to evaluate the economic results of the different simulated scenarios in a consistent way. The selected economic indicators should be harmonized with the ones applied by STECF for the assessment of the economic performance of the fleet (AER) and the “balance” indicators. Also, in the STECF report 18-15 (STECF 2018) indicators are proposed which could be possibly applied. Additionally EWG 22-11 highlights that there are no indicators on sociological characteristics in the bio-economic models so far. Some of the models give “social” indicators, but in general these are closely related to the economic ones (gross value added, crew share, employment) and they do not actually produce detailed results on the social impact of fisheries policies. Additional sections (Section 7) were added to review available information on technological creep in the western Mediterranean in the last ten years, but no information seems to be available now to account for this parameter within the models. A new section was dedicated to the development of a standardized ad hoc datacall for VMS and logbook data for MSs involved in the West Med MAP. The aim is to ease communication with MSs on the submission of these data and obtain a standardized format for all MSs that would fasten the work of experts in future EWGs. Due to time constraints, the two spatial modeling groups (SMART and ISIS-Fish) could not fulfill the scenarios requested in the TORs. The parameterization of such models is complex and time consuming, therefore to be able to respond to all TORs EWG 22-11 suggested that it would be very helpful to have scenarios at list a month before the beginning of the working group as it was done for EWG 22-01. Finally, in order to ease the work of EWGs concerned with the evaluation of effort and catch limit regime in the Western Mediterranean, catch at age matrices, F at age matrices and LFDs by GSA and gear for HKE and MUT stocks should be prepared in advance of the EWGs. This work could be held either during the western Mediterranean stock assessment EWG (to be evaluated with the chair of the EWG) or by a short ad hoc contract.European UnionPublishedReferee
Sea surface temperature record (1778-2015) in Orbicella faveolata (Cnidaria: Scleractinia) from Cayo Santa María reef, Cuba
No full textLas señales climáticas preservadas en las bandas de crecimiento del esqueleto de corales masivos ofrecen una perspectiva a largo plazo que permite comprender los cambios de la temperatura superficial del mar a diferentes escalas de tiempo. En el área del mar Caribe y el Golfo de México, especies de corales como Orbicella faveolata, en aguas someras, presentan formas de crecimiento masivo que facilitan el fechado de su esqueleto, lo que ha permitido la realización de estudios paleoambientales en zonas costeras donde los registros instrumentales son escasos y abarcan cortos periodos de tiempo. El propósito de este estudio fue caracterizar los registros geoquímicos en el esqueleto de un coral herma- típico O. faveolata, recolectado en el arrecife de Cayo Santa María, Cuba, y reconstruir la temperatura superficial del mar (TSM), con resolución anual, para los dos últimos siglos. Se obtuvieron registros de 230 años de Li/Ca, Sr/Ca, Mg/Ca, U/Ca, Li/Mg y Sr-U. De los indicadores geoquímicos analizados, el Li/Ca permitió la reconstrucción de la TSM para el área de estudio e indicó un incremento de 0.77 °C en los últimos 50 años. Ade- más, Li/Ca corroboró con buena exactitud los periodos característicos de calentamiento y enfriamiento reportados para el mar Caribe y el Golfo de México desde 1778. Orbicella faveolata demostró contener un buen registro multidecadal de la temperatura anual y de la Variabilidad Multidecadal Atlántica. Los resultados son la primera reconstrucción a largo plazo de la TSM en la zona costera de Cuba y brindan información relevante para comprender el calentamiento global en la región.Climatic signals preserved in the skeletal growth bands of massive corals offer a long-term perspective that allows understanding sea surface temperature changes at different time scales. In the Caribbean Sea and the Gulf of Mexico, coral species such as Orbicella faveolata present massive growth forms in shallow waters that facilitate dating of their skeleton, allowing to perform paleoenvironmental studies in coastal areas where instrumental records are scarce and cover short time periods. This study aimed to characterize coral geochem- ical records in the skeleton of a hermatypic coral O. faveolata collected in the Cayo Santa María (Cuba) reef and to reconstruct seawater surface annual temperatures for the last two centuries. Records of 230 years for Li/Ca, Sr/Ca, Mg/Ca, U/ Ca, Li/Mg, and Sr-U were obtained. The Li/Ca indicator al- lowed the reconstruction of SST in the study area from 1778 to 2015, indicating an overall increase of 0.77 °C in the last 50 years. In addition, Li/Ca corroborated with high accuracy the characteristic warming and cooling periods reported for the Caribbean Sea and the Gulf of Mexico since 1778. Orbicella faveolata proved to contain a good multidecadal record of annual temperature and of the Atlantic Multidecadal Variability. These results are the first long-term reconstruction of SST in the Cuban coastal zone and provide relevant information to understand global warming in the Caribbean.PublishedReferee
Nuevos registros de moluscos marinos para la costa nororiental de Cuba
No full textRecently, several studies on Cuban marine molluscs have been developed. However, it is necessary to conduct studies on their distribution, particularly in the poorly studied eastern coasts. In the present work, we collected and identified marine molluscs from the northeastern coast of Cuba. A checklist with 88 species, which are new records to the area, is presented; 59 species are gastropods, 27 are bivalves and two are chitons. Considering previous studies, 375 species have been recorded from this region. The localities with the higher number of recorded species are Playa Esmeralda - Playa Guardalavaca (232 species, 46 new records) and Bahía de Naranjo (107 species, 17 new records). Further studies have to be conducted in other localities of the area, particularly in coral lagoons and bays, and focused on micromolluscs, sea slugs and families with a high number of local endemics (Columbellidae, Marginellidae, and Cystiscidae).Recientemente, numerosos estudios sobre los moluscos marinos de Cuba se han sido desarrollados. No obstante, es necesario conducir estudios sobre su distribución, particularmente, en las poco estudiadas costas orientales. En el presente trabajo, se recolectaron e identificaron moluscos marinos de la costa nororiental de Cuba. Es presentada una lista anotada de 88 especies, que son nuevos registros para el área; 59 especies son gasterópodos, 27 son bivalvos y dos son quitones. Considerando los estudios anteriores, 375 especies han sido registradas de esta región. Las localidades con mayor número de especies registradas son Playa Esmeralda - Playa Guardalavaca (232 especies, 46 nuevos registros) y Bahía de Naranjo (107 especies, 17 nuevos registros). Estudios fu- turos deben ser conducidos en otras localidades del área, particularmente en lagunas coralinas y bahías, y con énfasis en micromoluscos, babosas de mar y familias con alto número de endémicos locales (Columbellidae, Margine- llidae y Cystiscidae).PublishedReferee
Trial to visualize the distribution and seasonal variation of ALB-measurable areas estimated from remotely sensed diffused attenuation coefficient data
No full textEfficient Airborne Lidar Bathymetry （ALB） surveys involve elaborate prior adjustments and operation planning processes based on a consideration of various relevant conditions. We attempted to visualize the distribution and its seasonal variation of the ALB measurable areas around Japan using a remotely sensed dataset of diffused attenuation coefficients, which represents the optical characteristics of the seawater, to help reduce the burden of the operation planning. The results showed that the maximum measurable depth at a certain spot seasonally varies and, subsequently, the distribution of the measurable areas varies as well. The estimated maximum penetration depths have proved to make a useful index for operation planning, while its future verification is required.PublishedReferee
Ocean Decade Progress Report 2021-2022.
No full textProclaimed in 2017 by the United Nations General Assembly, the United Nations Decade of Ocean Science for Sustainable Development – the Ocean Decade – is a framework to identify, generate and use critical ocean knowledge that is needed to manage the ocean sustainably, and achieve global aspirations for climate, biodiversity, and human well-being. Through its vision of ‘The science we need for the ocean we want’, the Ocean Decade provides an inclusive, equitable and global framework for diverse actors to co-design and co-deliver transformative ocean science to meet ten Ocean Decade Challenges. Through a collaborative, solutions-oriented approach, the Ocean Decade will contribute essential knowledge to global, regional, and national policy frameworks, including the 2030 Agenda and the Sustainable Development Goals.1 The Intergovernmental Oceanographic Commission of UNESCO (IOC-UNESCO) leads the coordination of the Ocean Decade, in collaboration with numerous partners from the United Nations system, governments, philanthropy, industry, civil society and the scientific community. 2021 was the first year of implementation of the Ocean Decade – a watershed moment in ocean science globally – and the achievements since the launch have been significant. Although challenges remain, particularly in relation to investment in ocean science, a robust foundation is now in place for the next nine years of transformative ocean science.OpenASFA inputPublishedReferee
Tres nuevos registros de Porcellanidae (Decapoda, Anomura) para Cuba oriental
No full textThe diversity of marine crabs (Anomura and Brachyura) of Cuba is well known. However, the poorly-known species distribution represents a challenge for conservation. The Cu- ban porcellanid crabs have been recently checked, however, the knowledge of this group remains underestimated. In this work, three species of porcellanid crabs, Petrolisthes galathinus, P. jugosus, and P. tonsorius are recorded to Eastern Cuba. Furthermore, the distribution of P. quadratus in this area is revised because several specimens were mixed with P. tonsorius. With these new records, 12 porcellanid species are registered for this region.La diversidad de cangrejos marinos (Anomura y Brachyura) de Cuba es bien conocida. No obstante, el pobre conocimiento sobre la distribución de las especies representa un reto para la conservación. Los cangrejos porcelánidos cubanos han sido revisados recien- temente, sin embargo, el conocimiento sobre este grupo continúa subestimado. En este trabajo, tres especies de cangrejos porcelánidos, Petrolisthes galathinus, P. jugosus y P. tonsorius, son registradas para Cuba oriental. Además, la distribución de P. quadratus en esta área es revisada, dado que varios ejemplares estaban mezclados con P. tonsorius. Con estos registros, 12 especies de porcelánidos han sido registradas en esta región.PublishedReferee
Effects of the variability effect of the Malvinas Current on the abundances of fishery resources associated with the continental shelf-break front
No full textMuchas poblaciones marinas presentan fluctuaciones en sus abundancias y principalmente a nivel del reclutamiento, el cual se refiere a la incorporación anual de nuevos individuos a la población (o a la pesquería). Esta variabilidad tiene repercusiones sobre la ecología del ecosistema donde viven; y sobre la economía, en el caso de tratarse de recursos pesqueros, ya que el reclutamiento está estrechamente vinculado al éxito o fracaso de las pesquerías. Los niveles de reclutamiento están débilmente relacionados con la abundancia del stock parental y al esfuerzo pesquero sobre los adultos; y fuertemente asociados a una diversidad de forzantes físicos y biológicos que actúan durante las etapas iniciales de la ontogenia (huevos, larvas y juveniles). La vieira patagónica (Zygochlamys patagonica) y el calamar argentino (Illex argentinus) son recursos pesqueros asociados al frente del talud, que poseen ciclos biológicos con larvas planctónicas y exhiben marcadas fluctuaciones naturales en los niveles de reclutamiento. El objetivo de esta tesis es explorar los efectos de la variabilidad ambiental en el ecosistema del frente de talud sobre las fluctuaciones poblacionales de estas especies de interés económico.Oceanic circulation off the Argentine continental shelf is dominated by the opposing flows of the Brazil and Malvinas (CM) currents. The transition between the relatively warm and slightly saline waters of the shelf and the cold and higher salinity waters of CM creates a strong thermo-haline gradient known as the shelf-break front. This front constitutes one of the most productive ecosystems in the region and it has a great ecological and economic importance. The CM borders the continental slope, from Drake Passage to approximately 38º S latitude, where it collides with the Brazil Current, generating one of the most energetic regions of the global ocean: the Brazil-Malvinas Confluence. This region, which represents the northern end of the shelf-break front, is characterized by high primary productivity throughout the year and the generation of warm and cold core eddies that export shelf waters to the open ocean. The high contrast of the surface water properties in the frontal area makes satellite images of sea level, ocean temperature and ocean color a very useful tool for studying its variability over a wide range of a temporal and spatial scales. Many marine populations show fluctuations in their abundance, mainly at the recruitment level, which refers to the annual incorporation of new individuals to the population (or to the fishery). This variability has repercussions on the ecology of the ecosystem where they live; and economy in the case of fishing resources, since it is closely linked to the success or failure of fisheries. Recruitment levels are weakly related to parental stock abundance and fishing effort on adults; and strongly associated with a diversity of physical and biological forcing that act over the initial stages of ontogeny (eggs, larvae and juveniles). The Patagonian scallop (Zygochlamys patagonica) and the Argentine squid (Illex argentinus) are fishery resources associated with the slope front, which have biological cycles with planktonic larvae and exhibit marked natural fluctuations in recruitment levels. The objective of this thesis is to explore the effects of environmental variability in the ecosystem of the slope front on the population fluctuations of these species of economic interest.PhDTesis (doctorado
Spatio-temporal sedimentary evolution of the sandy rim of the Ghar El Melah lagoon (Gulf of Tunis)
No full textL’objectif de ce mémoire est d’étudier la dynamique sédimentaire et de comprendre l’évolution spatio-temporelle du cordon sableux de Ghar El Melah. La méthodologie s’appuie sur une approche multicritère: une analyse sédimentologique permettant une caractérisation texturale des sédiments du lido de la lagune, complétée par une analyse statistique modale qui identifie les Types Sédimentaires (ST) et une quantification du flux éolien Un total de 37 échantillons superficiel a été prélevés et 28 échantillons récoltés par les pièges à sables au niveau du cordon sableux (lido) de Ghar El Melah, golfe de Tunis, Méditerranée. L’étude sédimentologique révèle que la majorité des sédiments (97 %) sont types sableux et 3 % appartient au faciès silteux. Les sédiments récoltés sont principalement unimodaux (Mo= 0,16) montrant un facies sableux homogène avec des sables moyens à fins avec une valeur de Mz compris entre 1,96 et 2,97 Phi, bien à très bien classés avec une valeur de l’écart type variant entre 0,11 et 0,40 Phi. L’analyse statistique modale montre que les sédiments sableux sont formés par un mélange de quatre types sédimentaires STI 86 %, STII 9 %, STIII 3% et STIV 2%. Le mélange de ce type sédimentaire présents au niveau du lido de la lagune témoigne l’origine des sédiments de la plage. Ce qui prouve que les sédiments sont issus de l’apport terrigène de Medjerda et de l’action des forces hydrodynamiques (vagues, courants et houles). La quantification du flux éolien montre que le lido de Ghar El Melah est soumis à une forte turbulence et d’érosion, la méthode employée consiste à quantifier la masse des particules mise en mouvement par le vent. Elle est caractérisée par un vent de direction NNO qui dépassant le 10 m/s dans certains cas. La vitesse de seuil de mouvement la plus élevé qui a balayé le sol lors de mesure du flux est de 0,0022 Kg/m/min avec une vitesse de 0,639 m/s bien que la vitesse de vent entrainant le mouvement des sables soit freinée par divers facteurs tel que la largeur et la morphologie de la plage, la pente et la topographie la granulométrie des sédiments, etc. la validation de résultat expérimental avec les formules empirique et semi-empirique montre que la formule la plus adaptée en notre secteur est celle de Zingg (1953).The objective of this thesis is to study the sedimentary dynamics and to understand the spatio temporal evolution of the sand rim of Ghar El Melah. The methodology is based on a multi-criteria approach: a sedimentological analysis allowing a textural characterization of the sediments of the lido of the lagoon, completed by a modal statistical analysis which identifies the Sedimentary Types (ST) and a quantification of the wind flow A total of 37 samples surface was collected and 28 samples collected by the sand traps at the level of the sandy rim (lido) of Ghar El Melah, Gulf of Tunis, Mediterranean. The sedimentological study reveals that most of the sediments (97%) are sandy types and 3% belong to the silty facies. The collected sediments are mainly unimodal (Mo = 0, 16) showing homogeneous sandy facies with medium to fine sands with a value of Mz between 1.96 and 2.97 Phi, well to very well classified with a value of the standard deviation varying between 0.11 and 0, 40 Phi. Statistical modal analysis shows that sandy sediments are formed by a mixture of four sedimentary types STI 86%, STII 9%, STIII 3% and STIV 2%. The mixture of this type of sediment present at the level of the lido of the lagoon testifies to the origin of the sediments of the beach. This proves that the sediments come from the terrigenous contribution of Medjerda and from the action of hydrodynamic forces (waves, currents, and swells). The quantification of the wind flow shows that the lido of Ghar El Melah is subject to strong turbulence and erosion, the method used consists in quantifying the mass of particles set in motion by the wind. It is characterized by a wind direction NNW which exceeds 10 m/s in certain cases. The highest threshold speed of movement which swept the ground during the measurement of the flow is 0.0022 Kg/m/min with a speed of 0.639 m/s although the wind speed causing the movement of the sands is slowed down by various factors such as the width and the morphology of the beach, the slope and the topography, the granulometry of the sediments, etc. the validation of experimental results with the empirical and semi-empirical formulas shows that the most suitable formula in our sector is that of Zingg (1953).Master