Now showing items 1-20 of 5753

    • An estimate of the sea level trend along the Tunisia coasts

      Jabnoun, Rihem; Harzallah, Ali (2020)
      This study evaluates the sea level trend along the Tunisia coasts based on available historical and recent tide gauge observations for the period 1880-2018. The stations used are located in the Tunisia coasts and in the western side of the Strait of Gibraltar. Sea level series based on reanalyses and Mediterranean Sea model simulations are also used. First, a single series representing the western Strait of Gibraltar sea level evolution is constructed. Then, the sea level series along the Tunisia coasts is constructed based on the hypothesis that the observed sea level drop relative to that in the western side of the Strait of Gibraltar remains nearly unchanged when long term periods are considered. The constructed series for the Tunisia coasts shows an evident sea level rise superimposed on a decadal variability in connection with the North Atlantic Oscillation (NAO). For the whole period, the estimated sea level trend is +1.5 mm/year, whereas it is +3mm/y for the recent period 1980- 2015. In addition to the widely accepted of the sea level rise acceleration during the recent decades, this higher trend may also be attributed to the effect of the decadal variability. Projections for the future state of the sea level along the Tunisia coasts are given based on the trend estimates found in this study.
    • A zoomed 3d circulation model for the Monastir bay: comparison to operational analyses

      Chaouch, Sana; Harzallah, Ali (2020)
      The present work aims at developing a zoomed 3D hydrodynamic model that simulates the circulation of water masses for the Central-Eastern coasts of Tunisia (Nabeul to Chebba) with the bay of Monastir in the center. The resolution of the model gradually increases from the edges (~ 1100 m) towards the bay of Monastir where it is of the order of 300 m. The model is forced at the sea surface by atmospheric data from a neighboring weather station and by ocean re-analyses. We present here a comparison between the results of the model and the reanalyses for the simulated year 2008. The outputs of the model show a strong seasonal cycle with winter cooling and summer warming more accentuated near the coasts. The surface salinity is modulated by the penetration of the Atlantic water vein in the Gulf of Hammamet, more important in summer. Near shallow coastal areas, the salinity is relatively high especially in the bay interior and is more accentuated in summer. The circulation is characterized by currents directed towards the southeast in winter and the West and Northwest in summer. These simulation results are similar to those of the re-analyses. The re-analyses offshore currents are, however, oriented towards the southwest in summer. A comparison of vertical sections of temperature and salinity shows high agreement with the presence of the trace of the Atlantic water vein at a depth of about 50 to 60 m.
    • Changes in the trophic structure, abundance and species diversity of exploited fish assemblages in the artisanal fisheries of the northern coast, Senegal, West Africa

      Ndour, Ismaila (2014)
      This work investigates the effects of changes in both fishing pressure and the environment on the trophic dynamics, abundance and diversity of species in the artisanal commercial fisheries off the northern coast of Senegal. Using artisanal commercial fishing data (provided by the Centre for Oceanographic Research of Dakar-Thiaroye [CRODT] in Senegal), we identify changes in the catch per unit effort, mean trophic level, biomass trophic spectrum and species diversity between two fishing periods (1990–1999 and 2000–2009). Decreases in mean trophic level, the biomass of high trophic level species and indices of species diversity between 1990 and 2009 were observed in commercial catches. These decreases were then related to changes in fishing pressure, fishing strategy and the combined effects of fishing and environmental factors (as derived from satellite observations). This paper helps to better inform the management of fisheries resources by providing decision makers with more effective biological indicators that incorporate the effects of fishing pressure and environmental change and that are applicable at local, regional and global scales.
    • Report on the Spiny Lobster Fishery: Lobster Survey Report 2020.

      Seychelles Fishing Authority; Seychelles Fishing Authority (Seychelles Fishing AuthorityVictoria, Seychelles, 2020-12)
      The spiny lobster fishery has been conventionally managed by seasonal closures and limited access (license-limited) regulations implemented by the Seychelles Fishing Authority. These regulations have been in force to limit fishers primarily targeting coastal and shallow water stocks, where abundance is limited and easily accessible. In the past, assessments of fisheries dependent data have shown several significant declines in the coastal stocks when too many licenses are allocated or when the fishery remains open for 3 to 4 consecutive seasons. Consequently, the stock status is determined by assessing both fisheries dependent and independent (surveys) data. Results obtained are provided to managers with advice on whether the fishery should be opened or remain closed. The 2019-2020 lobster fishing season was opened after remaining closed for two consecutive seasons (2017-2018, 2018-2019, Figure 1). In October 2020, as part of the Participatory Lobster Monitoring Programme (PLMP) a fisheries independent survey was carried out to assess stock status at 20 sites around Mahé. The aim of this paper is to present the results of the PLMP survey and to present information on several stock indicators based on the combined data collected from the survey and the 2019-2020 fishing season. Moreover, it provides several recommendations and advice to managers on both fishery and survey to decision making on whether the 2020-2021 fishing season should be opened or remain closed.
    • Fish diversity of the wild and aquaculture water bodies in Singida Region

      Bwathondi, P.O.J. (Tanzania Fisheries Research Institute (TAFIRI)Dar es Salaam, Tanzania, 2002)
      Tanzania Fisheries Research Institute being currently the only fisheries research institute in Tanzania has sole responsibility of marking the presence and distribution of fish species in the country. This work is expected to be completed by the year 2005. In order that this work can be accomplished, both published works and field observations(including geographical location using GPS) have to be compiled. Since the institute has centers in all the Great Lakes and one along the Indian Ocean coast, it is expected that field observations and identifications will be obtained and incorporated into the document to be produced by 2005. (PDF contains 15 pages)
    • National report of IFMP catch assessment survey (CAS) for August 2005

      Mkusu, B.S.; Rwekaza, C.T.; Lyimo, E.; Tanzania Fisheries Research Institute (TAFIRI), Mwanza; Fisheries Department, Regional Fisheries Office, Mwanza; Fisheries Division, Headquarters, Dar es Salaam (Tanzania Fisheries Research InstituteMwanza, Tanzania, 2005)
      The first comprehensive CAS was carried out during the month of July 2005 This is the second report of CAS for the month of August 2005 following the July report. The design and methodology followed was the same as in July. This report highlights the results obtained in August catch assessment survey. The report gives estimates of mean catch rates in Kgs./boat/day, total catches in M.tons and values of the catch by species. The total catch for August was 31,633.0 M. tons. This is lower when compared with the July catch which was 39,745.1 M. tons. In August the catch composed of Dagaa (45%), Nile perch (33%), Haplochromines (16%), Tilapiines (5%) and all other species combined (1%). (PDF contains 14 pages)
    • Description and analysis of the value chain of the Lake Victoria Nile perch fishery May-July 2008. Consultancy report no. 42

      Pollard, I. (MRAG LtdLondon, 2008-07)
      The study 'Value chain analysis of the Lake Victoria Nile perch fishery' was undertaken as part of the EC-funded 'Implementation of Fisheries Management Plan (IFMP) project', as requested by the Lake Victoria Fisheries Organisation (LVFO) Council of Ministers in 2007. The purpose of the study is to determine the value and share of benefits from this value along the whole commodity chain of Nile perch, from capture to consumption in the export markets of Europe. The project has been conducted over May to July 2008 and comprises two parts; a) an investigation of European Nile Perch marketing; and b) a survey of exporters in Uganda, Tanzania and Kenya. The full TORs are attached in Annex 1. Itinerary in Annex 2 needed revision upon arrival in each EAC country to confirm visits and more accurate plan the logistics. Annex 3 plus appendices provide the value chain analysis proper. This study is not being conducted in isolation and shares data as well as findings with ISTTA studies currently being undertaken, in particular the IFMP Agents Study (Lwenya et aI., Luomba, Odongkara et al.), the RSTTA Study on sustainable financing of BMUs (Kazoora et al), the LVFO Business Plan (Macfadyen) and the Functional Analysis study (Peacock). This study was deemed necessary because despite the impressive benefits from the Nile perch fishery, there is an image of this fishery which is very negative and potentially harmful to future investment and support. As well as the ecological damage, there have been repeated complaints, especially in the media, that the wealth from this fishery is unfairly distributed and that poor fishermen are exploited by rich, foreign factory owners. These complaints reveal a lack of understanding of the distribution of benefits derived from the fishery. Although draft reports were received from Luomba, Lwenya, Odongkara and Macfadyen, the Functional Analysis and cost-benefit analysis were not available and have not been included in this study.
    • New record of giant devil ray (Chondrichthyes: Myliobatidae) from Oran Bay (Western Meditteranean Sea)

      Hussein, Kais Boumedienne; Bensahla Talet, Lotfi (2019-06-01)
      The present paper reports a new record of Giant devil ray Mobula mobular (Bonnaterre, 1788)from western Algerian waters that is encountered for the first time in that coast since its firstdescription in 1901 and last observation in late 80’s. This elasmobranch is categorized asendangered on the IUCN Red List (Endangered A2d ver 3.1) and is likely to be the rarest of the ninespecies of Mobula genus. Occasionally it is captured in Mediterranean Sea by purse seines,bottom and pelagic trawls, pelagic nets, bottom longlines, drifters and harpoons. The specimenstranded in “la Madrague Beach” in Western Algerian coasts. Its disc length was measuring108.96 cm and disc width was 226.02 cm. This Myliobatidae is rarely seen with daily landed fish atOran fishery. Up to date no explicit reason can be given for the strand of M. mobular but ghostfishing and important maritime traffic stay the most plausible cause of this incident.
    • Reproductive biology of Pagellus acarne (Risso, 1927) (Teleostei: Sparidae) off western Algerian waters (Western Mediterranean)

      Bensahla Talet, Lotfi; Gherram, Malika; Dalouche, Fatiha; Bensahla Talet, Ahmed; Boutiba, Zitouni (2017)
      The reproduction of Pagellus acarne caught in Oran Bay was studied. The samples used were sorted monthlyfrom commercial catches of coastal trawlers operating in this area from April 2008 to July 2009. The overall sex ratio wasin favor of females 1:1.27 and length frequency distribution according to sex revealed that the females were highlyrepresentative beyond 20.5 cm of total length presuming a sexual inversion already described for this sparidae. Theestimated lengths at maturity (Lm) were 12.8 cm for females and 16.0 cm for males. Two spawning periods were made outby the follow-up of the gonado and hepato somatic indexes: a spring period from April to June with a peak in May and anautumnal period, between November and January with a peak in December. The closed season in Oran Bay extends from 1stMay to 31th August, which is to our opinion insufficient to safeguard the renewal of the resource and its spawning stock.
    • On the fecundity of the seabream, Pagellus acarne (Risso, 1827) of the western Mediterranean Sea, Algerian coasts

      Bensahla Talet, Lotfi; Mouffok, Salim; Bensahla Talet, Ahmed; Boutiba, Zitouni (2013)
      The fecundity of the Seabream from the western Mediterranean (Algerian coast) was assessed by the volumetric methodusing 22 ovaries from females between 169 and 263 mm total length (206.62 ± 19.93). Estimates of total potential annualfecundity varied between 19875 and 49125 oocytes per female (29448.86 ± 8198.12). Relationships between total potentialfecundity (F) and total length (Lt), total weight (Wt), gonad weight (Wg) were established using the multiplicative regressionmodel and a significant correlation was found (ANOVA: P‹0.01).
    • Age, growth and mortality of the common carp (Cyprinus carpio) population in Merdja Sidi Abed Dam, Algeria

      Bensahla Talet, Lotfi; Bensahla Talet, Ahmed (2019)
      We tried to estimate age, growth parameters, condition factor, length-weight relationship and mortality rates (Z, M, and F) of the common carp in Merdja Sidi Abed dam. Cyprinus carpio specimens were captured by long line between April and June 2013 in Merdjea Sidi abed. 220 individuals were collected and weights ranged between 265.5 and 620.3 g while the total length ranged between 26.3 and 35.6 cm. Length-converted catch curve was used to estimate total annual instantaneous mortality rates (Z), natural mortality was calculated using Pauly formula [ln(M) = -0.0152 - 0.279 ln(L∞) + 0.6543 ln(K) + 0.463 ln(T)]. Recruitment patterns were determined from the routine implemented in FISAT II. For all individuals (n = 220) of the common carp, the relationship between total length and body weight was: W = 0.0384 L2.70 (r2 = 0.906) for females and W = 0.0467 L2.653 (r2 = 0.976) for males a minor allometry was found for this species, mean condition factor K was estimated at 1.41. The maximum value of recruitment was recorded in March-April period with 19.56 and 15.20% respectively. The Battacharya method was used to estimate age of individuals that was comprised between 1 and years 3. The equation of Von Bertalanffy growth was: L = 36.75 [1-e-0.46 (t + 0.33)] for all the population. Total mortality (Z), natural mortality (M) and fishing mortality (F) were as follows: Z = 1.08, M = 0.82, F = 0.26 yr-1 while exploitation ratio (E) was evaluated at 0.24 indicating an under exploitation of this local resource.
    • Weight-length relationships of seven fish species (Teleostei: Sparidae, Mullidae, Carangidae) of Western Mediterranean Sea (Oran Bay, Algeria)

      Bensahla Talet, Lotfi; Gherram, Malika; Bensahla Talet, Ahmed (2017)
      No information currently exists on the weight-length relationships of Sparidae:Axillary seabream Pagellus acarne (Risso, 1827), bogue Boops boops (Linnaeus, 1758);Mullidae: Red mullet Mullus barbatus (Linnaeus, 1758), surmulet Mullus surmuletus (Linnaeus,1758) and Carangidae: Atlantic horse mackerel Trachurus trachurus (Linnaeus,1758),Mediterranean horse mackerel Trachurus mediterraneus (Steindachner 1863), Blue jackmackerel Trachurus picturatus (Bowdich 1825), seven commercial fish species of Oran Bay inWestern Mediterranean Sea. Data are presented for the first time for that region of theMediterranean Sea to contribute and help comparative growth studies. Samples were collectedfrom commercial catches at Oran Bay fisheries in Algeria. The values of the slope b in the lengthweightrelationship, W=aLb ranged from 2.841 to 3.296. The coefficients of correlation r2 werecomprised between 0.85 and 0.97. “a” and “b” parameters were compared with other fishing sitesfor the same fish species with Froese plot [Log a=ƒ(b)].
    • First record of invasive green algae Caulerpa racemosa var. cylindracea in Oran Bay (Western Algeria)

      Hussein, Kais Boumediene; Bensahla Talet, Lotfi (NISCAIR-CSIR, India, 2019-03)
      Caulerpa racemosa var. cylindracea (hereafter Caulerpa cylindracea) was first reported in the Mediterranean Sea in1926 1 in Tunisian waters and then in Tripoli harbor in Libya, in 1990. In late 90s it invaded the southern shore of Europe. InAlgeria, this invasive species was reported for the first time in 20072, five years after it appeared about 450 km from the firstsite in the eastern part of the Oranian littoral. This situation required widespread monitoring of this invasive species all along124 km of the coastline. More than 10 stations were patrolled and monitored since then, studied by scuba diving between thesurface and 30 m depth.The observations devoted to the distribution of Caulerpa cylindracea in Oran showed that specimens presented the sameappearance with irregularly entangled branched stolons attached to the substrate by colorless rhizoids from which the nameof the variety cylindracea was derived. Chronologically, the invasion direction seems to move from the bottom to the surfacewith an orientation from east to west, in the Oranian coastline. In situ observations confirmed high propagation speed ofCaulerpe in the Oranian coastline where invasions were signaled in several stations. The seaweed was observed for the firsttime in late 2011 and early 2012 (pers.obs) in Arzew Gulf (Cap Carbon) at the extreme east of the littoral, where the firstfronds were noticed. Then it extended geographically to the center of the coastline, in Kristel, early 2013. In 2014, it wasobserved in Ain Turc and Cap Falcon. In 2015, it was observed in the western shoreline near Bousfer beach and in 2016 itreached the “Plane” island (Paloma).This alien species was encountered at depths ranging from a few centimeters in microcuvettes up to 37 m, on varioussubstrates (hard, sandy, muddy) between marine phanerogams rhizomes and, also between the lower mid-littoral and infralittoralssuperior algae, with Posidonia oceanica herbarium. The study suggested a strong need for scientific monitoring andmanagement program, using optimized methodslike biological control or manual eradication for controlling the invasion.
    • Fecundity of the blotched picarel, Spicara maena (Linnaeus, 1758) from Oran Bay (Western Mediterranean Sea)

      Dalouche, Fatiha; Bensahla Talet, Lotfi; Bensahla Talet, Ahmed; Abi Ayad, Sidi Mohamed El Amine (2019)
      The fecundity of the blotched picarel Spicara maena from the western Mediterranean (Oran Bay) was assessed by the volumetric method. Total length (TL) of studied females varied between 91 and 140 mm (mean ± SD: 111.9 ± 10.6 mm). Estimates of total potential annual fecundity varied from 16,750 to 28,125 oocytes per individual (mean ± SD: 21,404.7± 2,698.8). Relationships between total potential fecundity (F) and TL, total weight, gonad weight were established using the multiplicative regression model and a high significant correlation was found in all the cases.
    • Acrosymphyton purpuriferum (J. Agardh) Sjostedt et Balliella cladoderma (Zanardini) Athanasiadis, deux nouvelles espèces d’algues benthiques de la Méditerranée marocaine

      Riadi, H.; Salhi, G.; Bouksir, H.; Moussa, H.; Hassoun, M. (2014)
      The authors report two new species of benthic algae from the Mediterranean sea of Morocco : Acrosymphyton purpuriferum (J. Agardh) Sjostedt (Acrosymphytaceae, Rhodophyta) and Balliella cladoderma (Zanardini) Athanasiadis. The geographical distribution,description and illustration of macroscopic and microscopic characters and ecological characteristics of these species are presented.
    • Synthèse de la production des régions continentales statistiques de juillet 2018

      Ministère de la Pêche et de l’Economie Maritime. Direction de la Pêche Continentale (Ministère de la Pêche et de l’Economie Maritime. Direction de la Pêche ContinentaleDakar, Senegal, 2018)
      Le sous-secteur de la pêche continentale est une composante essentielle de l’activité halieutique et revêt une importance capitale pour l’économie des régions continentales (Source importante de protéine et de revenues). La Pêche continentale est pratiquée aussi bien au niveau des principaux fleuves qu’au niveau des mares et autres plans d’eau aménagés. Elle est une activité artisanale qui cherche à s’améliorer de jour en jour avec l’aide de l’Etat à travers des aménagements d’infrastructure et autres donations et subvention d’équipements.La Production de la continentale varie d’une région à une autre du fait de la configuration hydrographique, des écosystèmes et du professionnalisme des acteurs.