scholarly journals Combining selection models and population structures to inform fisheries management: a case study on hake in the Mediterranean bottom trawl fishery

2020 ◽  
Author(s):  
CHRYSSI MYTILINEOU ◽  
BENT HERRMANN ◽  
STEFANOS KAVADAS ◽  
CHRIS J. SMITH ◽  
PERSEFONI MEGALOFONOU
Keyword(s):  
Fisheries Management ◽  
Size Structure ◽  
Eastern Mediterranean ◽  
Selection Models ◽  
Trawl Fishery ◽  
Time Period ◽  
Fisheries Policy ◽  
Population Structures ◽  
The Mediterranean ◽  
Spatio Temporal

The reduction of juvenile catch and discards are important targets in fisheries policy. This work examines how selection models can predict the size structure (LFD) of discards and landings considering the effects of area, time period, gear and fisher behaviour. Additional exploitation indicators related to the gear used, fisher's selection pattern, and discards were also estimated. The approach is demonstrated in a study concerning hake in the Mediterranean trawl fishery, focusing on high (HRA) and low (LRA) recruitment areas in the Saronikos Gulf (Eastern Mediterranean) during two periods (June, September) using two codends (40 mm square-40S, 50 mm diamond-50D mesh). The predicted discards LFDs revealed generally higher percentages in the HRA in June when using the 50D. The predicted landings LFDs showed higher percentages in the LRA in September for both codends, but undersized hake were always included. LFDs and exploitation indicators indicated that both codends were inappropriate for sustainable fishing of hake in the HRA, where 50D performed worse than the 40S. Fishing with both codends in the LRA in September revealed the lowest discards rates and minimum sizes of landings close to MCRS (minimum conservation reference size). These results can provide information to fisheries management aiming to protect juveniles and reduce discards through spatio-temporal fishing closures.

The importance of scale for fishing impact estimations

2009 ◽  
Vol 66 (5) ◽  
pp. 829-835 ◽  
Author(s):  
G. J. Piet ◽  
F. J. Quirijns
Keyword(s):  
Life History ◽  
Spatial Scale ◽  
Bottom Trawl ◽  
Spatial Processes ◽  
Temporal Scales ◽  
Fishing Impact ◽  
Trawl Fishery ◽  
Time Period ◽  
Spatio Temporal ◽  
The Impact

The impact of a bottom trawl fishery on fish or benthos is often determined by multiplying the frequency of the passing of the trawl by a factor for the effect (i.e., % mortality) of the singular passing of the gear. As fishing intensity in an area is not homogeneously distributed, it is necessary to determine the proportions of the area that are fished with different trawling frequencies, as these subareas together contribute to the overall species’ mortality. In this study, we show that the perceived proportion of the area fished with a specific trawling frequency depends upon the spatial and temporal scale used. A smaller spatial scale results in an increased perceived patchiness of the fishing intensity, while a longer time period does the opposite. The implication is that to determine the fishing-induced mortality of a particular species, the trawling frequency needs to be determined at those spatio-temporal scales that are appropriate considering the species’ spatial processes (e.g., dispersion) or temporal processes described by life history characteristics.

scholarly journals MEDLEM database, a data collection on large Elasmobranchs in the Mediterranean and Black seas

2020 ◽  
Author(s):  
CECILIA MANCUSI ◽  
ROMANO BAINO ◽  
CATERINA FORTUNA ◽  
LUIS GIL DE SOLA ◽  
GABRIEL MOREY ◽  
...  
Keyword(s):  
Size Structure ◽  
Eastern Mediterranean ◽  
Public Awareness ◽  
Conservation Status ◽  
Shortfin Mako ◽  
Thresher Shark ◽  
Elasmobranch Species ◽  
The Mediterranean ◽  
By Catch ◽  
Mediterranean And Black Seas

The Mediterranean Large Elasmobranchs Monitoring (MEDLEM) database contains over 3000 records (more than 4000 individuals) of large elasmobranch species from 20 different countries around the Mediterranean and Black seas, observed from 1666 to 2017. The main species included in the archive are the devil fish (1 813 individuals), the basking shark (939 individuals), the blue shark (585 individuals) and the great white shark (337 individuals).In the last decades other species such as the shortfin mako (166 individuals), the spiny butterfly ray (138) and the thresher shark (174 individuals) were reported with an increasing frequency. This was possibly due to an increased public awareness on the conservation status of sharks, and a consequent development of new monitoring programmes. MEDLEM does not have a homogeneous reporting coverage throughout the Mediterranean and Black seas and it should be considered as a database of observed species presence. Scientific monitoring efforts in the south-eastern Mediterranean and Black seas are generally lower than in the northern sectors and the absence in our database of some species does not imply their actual absence in these regions. Some considerations are made on the frequency and spatial distribution of records, size structure of the observed individuals for selected species, general area coverage and species involved as by-catch by fishing gear.

The morphology and behaviour of Cercaria lata Lespés, 1857 (Digenea, Faustulidae) from the Mediterranean clam Tapes decussata (L.)

2009 ◽  
Vol 83 (1) ◽  
pp. 69-76 ◽  
Author(s):  
L. Gargouri Ben Abdallah ◽  
N. Trigui El Menif ◽  
F. Maamouri
Keyword(s):  
Comparative Study ◽  
Digestive Gland ◽  
Multivariate Analyses ◽  
Eastern Mediterranean ◽  
Temporal Distribution ◽  
Gulf Of Gabes ◽  
Donax Trunculus ◽  
The Mediterranean ◽  
Spatio Temporal ◽  
First Time

AbstractCercaria lata (Digenea, Faustulidae), discovered by Lespés (1857) in Tapes decussata (L.) in the basin of Arcachon, was found for the first time, from the eastern Mediterranean, in the same lamellibranch from Tunisia (Bizerte and Tunis lagoons and Gulf of Gabes). These cercariae develop in daughter sporocysts, which develop in mother sporocysts in the gonads. Daughter sporocysts are observed in the gonads and sometimes in the digestive gland. A redescription and the behaviour of the naturally emerging cercariae and spatio-temporal distribution of the sporocysts are reported. A comparative study using multivariate analyses associated with morphology, biology and seasonality confirm the distinctness of Cercaria lata and the cercaria of Cercaria pectinata from Donax trunculus.

scholarly journals Mitogenomics of the endangered Mediterranean monk seal (Monachus monachus) reveals dramatic loss of diversity and supports historical gene-flow between Atlantic and eastern Mediterranean populations

2020 ◽  
Author(s):  
Alba Rey-Iglesia ◽  
Philippe Gaubert ◽  
Gonçalo Espregueira Themudo ◽  
Rosa Pires ◽  
Constanza De La Fuente ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
North Atlantic ◽  
Marine Mammals ◽  
Eastern Mediterranean ◽  
The Black Sea ◽  
Mediterranean Populations ◽  
Geographic Ranges ◽  
Western Sahara ◽  
The Mediterranean

Abstract The Mediterranean monk seal Monachus monachus is one of the most threatened marine mammals, with only 600–700 individuals restricted to three populations off the coast of Western Sahara and Madeira (North Atlantic) and between Greece and Turkey (eastern Mediterranean). Its original range was from the Black Sea (eastern Mediterranean) to Gambia (western African coast), but was drastically reduced by commercial hunting and human persecution since the early stages of marine exploitation. We here analyse 42 mitogenomes of Mediterranean monk seals, from across their present and historical geographic ranges to assess the species population dynamics over time. Our data show a decrease in genetic diversity in the last 200 years. Extant individuals presented an almost four-fold reduction in genetic diversity when compared to historical specimens. We also detect, for the first time, a clear segregation between the two North Atlantic populations, Madeira and Cabo Blanco, regardless of their geographical proximity. Moreover, we show the presence of historical gene-flow between the two water basins, the Atlantic Ocean and the Mediterranean Sea, and the presence of at least one extinct maternal lineage in the Mediterranean. Our work demonstrates the advantages of using full mitogenomes in phylogeographic and conservation genomic studies of threatened species.

scholarly journals Detecting Tourism Typologies of Regional Destinations Based on Their Spatio-Temporal and Socioeconomic Performance: A Correlation-Based Complex Network Approach for the Case of Greece

2021 ◽  
Vol 2 (1) ◽  
pp. 113-139
Author(s):  
Dimitrios Tsiotas ◽  
Thomas Krabokoukis ◽  
Serafeim Polyzos
Keyword(s):  
Network Analysis ◽  
Complex Network ◽  
Community Detection ◽  
Optimization Algorithm ◽  
Spatial Dimension ◽  
Economic Dimension ◽  
Complex Network Analysis ◽  
Time Period ◽  
Time Patterns ◽  
Spatio Temporal

Within the context that tourism-seasonality is a composite phenomenon described by temporal, geographical, and socio-economic aspects, this article develops a multilevel method for studying time patterns of tourism-seasonality in conjunction with its spatial dimension and socio-economic dimension. The study aims to classify the temporal patterns of seasonality into regional groups and to configure distinguishable seasonal profiles facilitating tourism policy and development. The study applies a multilevel pattern recognition approach incorporating time-series assessment, correlation, and complex network analysis based on community detection with the use of the modularity optimization algorithm, on data of overnight-stays recorded for the time-period 1998–2018. The analysis reveals four groups of seasonality, which are described by distinct seasonal, geographical, and socio-economic profiles. Overall, the analysis supports multidisciplinary and synthetic research in the modeling of tourism research and promotes complex network analysis in the study of socio-economic systems, by providing insights into the physical conceptualization that the community detection based on the modularity optimization algorithm can enjoy to the real-world applications.

Assessing broad life cycle impacts of daily onboard decision-making, annual strategic planning, and fisheries management in a northeast Atlantic trawl fishery

2015 ◽  
Vol 23 (7) ◽  
pp. 1357-1367 ◽  
Author(s):  
Friederike Ziegler ◽  
Evelyne A. Groen ◽  
Sara Hornborg ◽  
Eddie A. M. Bokkers ◽  
Kine M. Karlsen ◽  
...  
Keyword(s):  
Decision Making ◽  
Life Cycle ◽  
Strategic Planning ◽  
Fisheries Management ◽  
Northeast Atlantic ◽  
Trawl Fishery

Upper-plate structural controls on the segmentation of the Kefalonia Fault (Ionian Sea, Greece)

2021 ◽  
Author(s):  
Emmanuel Skourtsos ◽  
Haralambos Kranis ◽  
Spyridon Mavroulis ◽  
Efthimios Lekkas
Keyword(s):  
Eastern Mediterranean ◽  
Source Parameters ◽  
Plate Boundary ◽  
Temporal Distribution ◽  
Western Coast ◽  
African Plate ◽  
Plate Structure ◽  
The North ◽  
Macroseismic Effects ◽  
Spatio Temporal

<p>The NNE-SSW, right-lateral Kefalonia Transform Fault (KTF) marks the western termination of the subducting Hellenic slab, which is a part of the oceanic remnant of the African plate. The inception of the KTF, described as a STEP fault, is placed in the Pliocene. KTF is considered to be the most active earthquake source in the Eastern Mediterranean. During the last two decades, four significant earthquakes (M>6.0) have been associated with the KTF. These events are attributed to the reactivation of different segments of the KTF, which are (from North to South) the North Lefkada, South Lefkada, Fiskardo, Paliki and Zakynthos segments: the North Lefkada segment ruptured in the 2003 earthquake, the 2014 Kefalonia events are associated with the Paliki segment and the 2015 Lefkada earthquake with the South Lefkada (and possibly the Fiskardo) segments.</p><p>The upper plate structure in the islands of Lefkada and Kefalonia is characterized by the Ionian Unit, thrusted over the Paxi (or Pre-Apulian) Unit. The Ionian Thrust, which brings the Ionian over the Paxi Unit, is a main upper-plate NNW-SSE, NE-dipping structure. It runs through the island of Lefkada, to be mapped onshore again at the western coast of Ithaki and at SE Kefalonia. Two other major thrusts are mapped on this island: the Aenos thrust, which has a WNW-ESE strike at the southern part of the island and gradually curves towards NNW-SSE in the west and the Kalo Fault in the northern part. These Pliocene (and still active) structures developed during the late-most stages of thrusting in the Hellenides, strike obliquely to the KTF and appear to abut against it.</p><p>We suggest that these thrusts control not only the deformation within the upper plate, but also the earthquake segmentation of the KTF. This suggestion is corroborated by the spatio-temporal distribution and source parameters of the recent, well-documented earthquake events and by the macroseismic effects of these earthquakes. The abutment of the Ionian thrust against the KTF marks the southern termination of the Lefkada earthquake segment, which ruptured in the 2003 earthquake, while the Aenos, (or the Kalo) thrust mark the southern end of the Fiskardo segment. The spatial distribution of the Earthquake Environmental Effects related to the four significant events in the last 20 years displays a good correlation with our interpretation: most of the 2003 macroseismic effects are located in the northern part of Lefkada, which belongs to the upper block of the Ionian thrust; similarly, the effects of the 2014 earthquakes of Kefalonia are distributed mainly in the Paliki Peninsula and the southern part of the island that belong to the footwall of the Aenos thrust and the 2015 effects are found in SW Lefkada, which is part of the footwall of the Ionian thrust.</p><p>We suggest that correlation between upper-plate structure and plate boundary faulting can provide insights in the understanding of faulting pattern in convergent settings, therefore contributing to earthquake management plans.</p>

The role of brush encroachment in Mediterranean ecosystems: a review

2021 ◽  
pp. 1-12
Author(s):  
Zalmen Henkin
Keyword(s):  
Eastern Mediterranean ◽  
Soil Nutrient ◽  
Fire Risk ◽  
Mediterranean Ecosystems ◽  
Climatic Conditions ◽  
Past Century ◽  
Great Success ◽  
Management Interventions ◽  
The Mediterranean ◽  
Efficient Option

Abstract Encroachment of woody plants into grasslands and subsequent brush management are among the most prominent changes occurring in arid and semiarid ecosystems over the past century. The reduced number of farms, the abandonment of marginal land and the decline of traditional farming practices have led to encroachment of the woody and shrubby components into grasslands. This phenomenon, specifically in the Mediterranean region, which is followed by a reduction in herbage production, biodiversity and increased fire risk, is generally considered an undesirable process. Sarcopoterium spinosum has had great success in the eastern Mediterranean as a colonizer and dominant bush species on a wide variety of sites and climatic conditions. In the Mediterranean dehesa, the high magnitude and intensity of shrub encroachment effects on pastures and on tree production were shown to be dependent on temporal variation. Accordingly, there are attempts to transform shrublands into grassland-woodland matrices by using different techniques. The main management interventions that are commonly used include grazing, woodcutting, shrub control with herbicides or by mechanical means, amelioration of plant mineral deficits in the soil, and fire. However, the effects of these various treatments on the shrubs under diverse environmental conditions were found to be largely context-specific. As such, the most efficient option for suppressing encroachment of shrubs is combining different interventions. Appropriate management of grazing, periodic control of the shrub component, and occasional soil nutrient amelioration can lead to the development of attractive open woodland with a productive herbaceous understory that provides a wider range of ecological services.

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