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The genetic diversity of the Mediterranean swordfish (Xiphias gladius Linneus) has not been explored extensively at its easternmost range so far. In this study, modern X. gladius samples from the eastern part of the Mediterranean basin, north of the Aegean Sea (Aegean-2013, n = 26) and the Mediterranean coast of Turkey (N.Levantine-2013, n = 42) were studied genetically, along with ancient samples from Yenikapi excavation (n = 6). Partial mitochondrial DNA control region sequences (entire sequences, clade I and clade II) were evaluated spatially and temporally together with previously published sequences (Alvarado Bremer et al., Molecular Phylogenetics and Evolution, 2005, 36, 169-187; Vinas et al., ICES Journal of Marine Science, 2010, 67, 1222-1229; Righi et al., Diversity, 2020, 12, 170) from the rest of the Mediterranean Sea. Pair-wise F-ST and pair-wise AMOVA tests showed that, in general, groups of eastern populations and western Mediterranean populations have not genetically differed from each other significantly nearly in the past 20 years. Therefore, the results direct reconsideration of previous descriptions of population sub-structure within the Mediterranean and support high gene flow throughout the region. On the contrary, the results of this study confirmed the existence of genetic diversity differences between western and eastern Mediterranean, with eastern being low. One-tailed permutation tests revealed that theta, which is directly proportional to long-term female effective population size (Ne), decreased significantly (P < 0.05) in both regions over the past two decades. On the Turkish coasts, theta is not significantly different from that of the nearly contemporary eastern Mediterranean population. Nonetheless, theta of the ancient sample was consistently and significantly (P < 0.001) higher than those of the eastern and western Mediterranean populations in clade I and clade II. Furthermore, it contains two mitochondrial haplotypes that are not observed in modern samples, suggesting that the Ne of X. gladius in the eastern was high in Byzantium times. Eight microsatellite loci were also genotyped in modern samples. The microsatellite-based present Ne estimate of the pooled Aegean-2013 and N.Levantine-2013 populations was lower than 1000 according to the upper limit of 95% c.i. and possibly even lower than 100 according to the mean of posterior distribution of the present Ne estimate calculated by the software package MSVAR. These alarming genetic signals for the sustainability of X. gladius on the coasts of Turkey are in agreement with the nearly collapsing X. gladius fisheries as depicted also in the fisheries statistics. Overall, congruent with the previous studies, the data presented here show that sustainability of the X. gladius population in Mediterranean is under major threat. Therefore, X. gladius around the Turkish coasts need an immediate stringent action and management plan.

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Bu çalışmada, Batı Karadeniz dip trol balıkçılığının genel karakteriile çekim süresi, hedef, ıskarta ve toplam av miktarı gibi bazı parametrelerarası ilişkiler regresyon ve korelasyon analizi ile incelenmiştir. Çalışmaverileri İğneada ve Rumeli Feneri bölgelerinde 2012-2014 yılları arasında 66geçerli dip trol çekiminden elde edilmiştir. Sonuç olarak 2010-2014 yıllarıarasında dip trol balıkçılarının denize çıktıkları gün sayısı 99 ile 167arasında değiştiği tespit edilmiştir. Çekim süresi arttıkça toplam av artarkenıskarta av miktarı da artmaktadır. Karadeniz demersal kaynaklarınınsürdürülebilir kullanımının sağlanması için yalnızca karaya çıkan av üzerindendüzenlemeler yapmak yerine balıkçılık girdi kontrollerinin de (denize çıkılangün sayısı ve çekim süresi gibi) balıkçılık yöneticileri tarafından planlanmasıgerekmektedir., In this study, general characteristics ofbottom trawl fishery and relationships of inter parameter such as haulduration, total and discard catch were defined by regression and correlationanalysis. Data of study was obtained by 66 valid bottom trawl hauls in İğneadaand Rumeli Feneri regions between the years 2012-2014. Accordingly, days at seaof bottom trawlers varied between 99 and 167 days for between years of 2010 and2014. The total amount of catch increases as haul duration increases. In themeantime, however, discard amount increases as well. To be able to provide thesustainable exploitation of Black Sea demersal resources, controls of fisheryinputs (days at sea and haul duration etc.) should be planned by fisheryauthorities instead of regulations based on only landings.

Bu çalışmada,Batı Karadeniz dip trol balıkçılığında av kompozisyonun belirlenmesi vederinliğin av kompozisyonuna olan etkisinin belirlenmesi amaçlanmıştır. Çalışmaverileri İğneada ve Rumeli Feneri bölgelerinde 2012-2013 ve 2013-2014balıkçılık sezonlarında 66 dip trol çekiminden elde edilmiştir. Toplam 32 türelde edilen avcılık operasyonlarında 20-50 m ve 50-100 m derinlik konturlarındatür kompozisyonun ve av oranlarının farklı olduğu belirlenmiştir. Kemiklibalıklar iki derinlik konturunda da tür sayısı, birey sayısı ve toplam ağırlıkbakımından baskın gruptur. Hedef türler olan mezgit ve barbunya balıklarıtoplam avın ağırlıkça sırasıyla % 38.26 ve %22.88’ini oluşturmuştur. Çalışmasonuçları, ideal bir balıkçılık yönetiminin av kompozisyonunun ve korumaönceliklerinin iyi anlaşıldığı bir temele dayanması gerektiğini göstermektedir.Batı Karadeniz demersal kaynaklar bakımından en önemli balıkçılık alanlarındanbiridir ve uzun vadede bir sürdürebilirlik için derinlik gibi faktörleri gibidikkate alan uzun süreli izleme çalışmalarına ihtiyaç vardır., In thisstudy, the determination of catch composition in bottom trawling and effect ofdepth was aimed in the western Black Sea. Data was obtained by 66 bottom trawlhauls during 2012-2013 and 2013-2014 fishing periods in İğneada and RumeliFeneri fishing regions. A total of 32 species were obtained where the speciescomposition and catch rates were different between 20-50m and 50-100 m depthcontours. Bony fishes are dominant group for both depth contours in terms ofnumber of species, number of individuals, and total weight. Target species,whiting and red mullet, consisted of 38.26% and 22.88% of total catch byweight, respectively. The study results shows an optimal management shoulddepends on a good understanding of how catch composition and conservationconcern. Western Black Sea is one of the most important fishing ground in termsof demersal resources and long-term monitoring of trawl catch composition whichemphasize factors like depth is needed for long term sustainability.

Bu çalışmayla, İstanbul kıyı balıkçılığında kullanılan pelajik uzatma ağlarının teknik özellikleri tespit edilmiştir. Bölgede iki adedi fanyalı ve beş adedi sade olmak üzere toplam yedi tip pelajik uzatma ağı tanımlanmıştır. Bu uzatma ağlarının teknik planları FAO standartlarına göre ilk defa tanıtılmıştır

Bu çalışma, İstanbul Boğazı’nda kurulan kaldırma ağlarının mevkileri, ağların teknik özellikleri, balıkçılık durumlarını ve hedef türleri belirlemek amacıyla yapılmıştır. İstanbul Boğazı’nda iskele ve kıyılarda kurulan üç adet kaldırma ağı (Arnavutköy, Yeniköy ve Tarabya) bulunduğu tespit edilmiştir. Kurulan kaldırma ağları, taşıyıcı direkler veya kaldıraç sistemine göre çalışmaktadır. Araştırma süresince kaldırma ağlarında rastlanılan balık türleri; gümüş (Atherina boyeri), kefal (Mullet sp.) ve zargana (Belone belone)’dır

Bu çalışmayla, İstanbul kıyı balıkçılığında kullanılan dip uzatma ağlarının teknik özellikleri tespit edilmiştir. Bölgede altı adedi fanyalı ve yedi adedi sade olmak üzere toplam 13 tip dip uzatma ağı tanımlanmıştır. Bu uzatma ağlarının teknik planları FAO standartlarına göre ilk defa tanıtılmıştır

In this study, the stomach contents of 116 albacore specimens, Thunnus alalunga were examined from the eastern Mediterranean Sea. Fifty-five of the 116 stomachs examined were empty. The occurrence of major prey categories in stomachs were 95.1% cephalopods, 47.5% teleosts and 39.3% crustaceans with a total Of 633 individuals belonging to 14 species identified. Heteroteuthis dispar from the order Sepiolida constituted 56-40% of the main cephalopod prey followed by Onychoteuthis banksii from the order Teuthida.

The Atlantic bluefin tuna is a highly migratory species emblematic of the challenges associated with shared fisheries management. In an effort to resolve the species' stock dynamics, a genomewide search for spatially informative single nucleotide polymorphisms (SNPs) was undertaken, by way of sequencing reduced representation libraries. An allele frequency approach to SNP discovery was used, combining the data of 555 larvae and young-of-the-year (LYOY) into pools representing major geographical areas and mapping against a newly assembled genomic reference. From a set of 184,895 candidate loci, 384 were selected for validation using 167 LYOY. A highly discriminatory genotyping panel of 95 SNPs was ultimately developed by selecting loci with the most pronounced differences between western Atlantic and Mediterranean Sea LYOY. The panel was evaluated by genotyping a different set of LYOY (n = 326), and from these, 77.8% and 82.1% were correctly assigned to western Atlantic and Mediterranean Sea origins, respectively. The panel revealed temporally persistent differentiation among LYOY from the western Atlantic and Mediterranean Sea (FST = 0.008, p = .034). The composition of six mixed feeding aggregations in the Atlantic Ocean and Mediterranean Sea was characterized using genotypes from medium (n = 184) and large (n = 48) adults, applying population assignment and mixture analyses. The results provide evidence of persistent population structuring across broad geographic areas and extensive mixing in the Atlantic Ocean, particularly in the mid-Atlantic Bight and Gulf of St. Lawrence. The genomic reference and genotyping tools presented here constitute novel resources useful for future research and conservation efforts., This work was carried out under the provision of the ICCAT Atlantic-wide Research Programme for Bluefin Tuna (GBYP), funded by the European Union, by several ICCAT CPCs, the ICCAT Secretariat and other entities (see: http://www.iccat.int/GBYP/en/Budget.htm). Additional funds were provided by the MARES Joint Doctorate Programme Selected Under Erasmus Mundus and coordinated by Ghent University (FPA 2011-0016). Larvae from the Balearic Sea were provided by the ATAME project “Bluefin tuna abundance indices: towards recruitment estimators based on larval ecology” (CTM 2011-29525-C04-02) and the BLUEFIN project “Modelling bluefin spawning areas variability and population dynamics in the Western Mediterranean” (IEO-SOCIB agreement).

Two stocks of bluefin tuna (Thunnus thynnus) inhabit the north Atlantic; the western and eastern stocks spawn in the Gulf of Mexico and the Mediterranean Sea respectively. Trans-Atlantic movements occur outside spawning time whereas natal homing maintains stock structure. Commercial fisheries may exploit a mixed assemblage of both stocks. The incorporation of mixing rates into stock assessment is precluded by uncertainties surrounding stock discrimination. Otolith shape descriptors were used to characterise western and eastern stocks of Atlantic bluefin tuna in the present study and to estimate stock composition in catches of unknown origin. Otolith shape varied with length and between locations and years. Within a restricted size range (200–297-cm fork length (FL)) the two stocks were distinguished with an accuracy of 83%. Bayesian stock mixture analysis indicated that samples from the east Atlantic and Mediterranean were predominantly of eastern origin. The proportion assigned to the eastern stock showed slight spatial variation; however, overlapping 95% credible intervals indicated no significant difference (200–297cm FL: central Atlantic, 73–100%; Straits of Gibraltar, 73–100%; Morocco, 50–99%; Portugal 64–100%). Otolith shape could be used in combination with other population markers to improve the accuracy of mixing rate estimates for Atlantic bluefin tuna.