F. Saadet Karakulak

Cephalopods in the diet of albacore, Thunnus alalunga, from the eastern Mediterranean

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.

Molecular Identification of Atlantic Bluefin Tuna (Thunnus thynnus, Scombridae) Larvae and Development of a DNA Character-Based Identification Key for Mediterranean Scombrids.

The Atlantic bluefin tuna, Thunnus thynnus, is a commercially important species that has been severely over-exploited in the recent past. Although the eastern Atlantic and Mediterranean stock is now showing signs of recovery, its current status remains very uncertain and as a consequence their recovery is dependent upon severe management informed by rigorous scientific research. Monitoring of early life history stages can inform decision makers about the health of the species based upon recruitment and survival rates. Misidentification of fish larvae and eggs can lead to inaccurate estimates of stock biomass and productivity which can trigger demands for increased quotas and unsound management conclusions. Herein we used a molecular approach employing mitochondrial and nuclear genes (CO1 and ITS1, respectively) to identify larvae (n = 188) collected from three spawning areas in the Mediterranean Sea by different institutions working with a regional fisheries management organization. Several techniques were used to analyze the genetic sequences (sequence alignments using search algorithms, neighbour joining trees, and a genetic character-based identification key) and an extensive comparison of the results is presented. During this process various inaccuracies in related publications and online databases were uncovered. Our results reveal important differences in the accuracy of the taxonomic identifications carried out by different ichthyoplanktologists following morphology-based methods. While less than half of larvae provided were bluefin tuna, other dominant taxa were bullet tuna (Auxis rochei), albacore (Thunnus alalunga) and little tunny (Euthynnus alletteratus). We advocate an expansion of expertise for a new generation of morphology-based taxonomists, increased dialogue between morphology-based and molecular taxonomists and increased scrutiny of public sequence databases.

Otolith shape variation provides a marker of stock origin for north Atlantic bluefin tuna (Thunnus thynnus)

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.

Potential health risks due to heavy metal uptake via consumption of Thunnus thynnus from the northern Levantine Sea

Abstract The potential human health risks of copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb) in Thunnus thynnus from the northern Levantine Sea were assessed. The mean concentrations (mg/kg) of metals were found as 0.819 for Cu, 8.344 for Zn, 2.102 for As, 0.002 for Cd, 0.001 for Hg and 0.115 for Pb. Even though these values were below the permitted levels, 11% of the samples contained Pb above the limits. Estimated weekly intakes were conspicuously lower than the PTWI values. The target hazard quotients (THQs) of each metal and total THQ of combined metals remained well below 1, showing no public health risk for an average consumer.

Toxic Metals and Omega-3 Fatty Acids of Bluefin Tuna from Aquaculture: Health Risk and Benefits

The share of Bluefin Tuna (BFT) has gained in importance in world fishing and trade for the last 50 years. Particularly in the Mediterranean region, this capture-based aquaculture (farming and fattening) activity has reached an important potential. This study examined the effects of toxic metals and omega-3 fatty acids from BFT fish captured in the Mediterranean Sea and cultured in the Aegean Sea on human health. The results of the current research revealed that the different groups of BFT (medium and large) fishes in general were rich in omega-3 fatty acids (especially from EPA and DHA) and hypocholesterolemic/Hypercholesterolemic potential ( h / H ) is higher than 3. The consumption of BFT products will reduce the cardiovascular risks. However, due to THQ (≥ 1), it has been found that mercury may cause serious health problems to the community in the long term.

General characteristics of bottom trawl fishery and effect of haul duration and total catch on discard in the Western Black Sea

Bu calismada, Bati Karadeniz dip trol balikciliginin genel karakteri ile cekim suresi, hedef, iskarta ve toplam av miktari gibi bazi parametreler arasi iliskiler regresyon ve korelasyon analizi ile incelenmistir. Calisma verileri Igneada ve Rumeli Feneri bolgelerinde 2012-2014 yillari arasinda 66 gecerli dip trol cekiminden elde edilmistir. Sonuc olarak 2010-2014 yillari arasinda dip trol balikcilarinin denize ciktiklari gun sayisi 99 ile 167 arasinda degistigi tespit edilmistir. Cekim suresi arttikca toplam av artarken iskarta av miktari da artmaktadir. Karadeniz demersal kaynaklarinin surdurulebilir kullaniminin saglanmasi icin yalnizca karaya cikan av uzerinden duzenlemeler yapmak yerine balikcilik girdi kontrollerinin de (denize cikilan gun sayisi ve cekim suresi gibi) balikcilik yoneticileri tarafindan planlanmasi gerekmektedir.

From Ocean to Farm: Capture-Based Aquaculture of Bluefin Tuna in the Eastern Mediterranean Sea

Abstract Atlantic bluefin tuna (ABFT) fattening activities began in the eastern Mediterranean (Cyprus, Greece, and Turkey) in 2002. The total potential production is estimated at 11,240 tons. However, the actual production fluctuates depending on catch quota. ABFT farming in the region uses traditional methods of catching tuna with purse seiners and transferring them to grow-out cages, where they are fed small pelagic fishes until they reach the size and fat level required by the high-end market. ABFT farming in the region has had some conflicts with other human activities such as tourism. The boom in tuna farming in the Mediterranean over a relatively short period of time has caused overfishing, which in turn has led to a decreasing spawning stock. The ABFT has disappeared from the Black Sea, and their spawning ground in the eastern Mediterranean needs to be regulated and protected to ensure the long-term sustainability of the stock. Illegal, Unreported and Unregulated (IUU) fishing practices should be strictly regulated by the International Commission for the Conservation of Atlantic Tunas (ICCAT) members and nonmember countries. The development of hatchery and sustainable aquaculture technologies will decrease the pressure on wild stocks and in the future may enable stock enhancement, mitigating overfishing, and decreasing the high market price of the ABFT in the eastern Mediterranean and elsewhere.