Population Structuring and Migration Pathway of Atlantic bonito Sarda sarda

Natural and Engineering Sciences 56 Volume 1, No. 3, 56-65, 2016 -RESEARCH ARTICLEPopulation Structuring and Migration Pathway of Atlantic bonito Sarda sarda Cemal Turan1*, Petya Ivanova2, Alen Soldo3 1 Molecular Ecology and Fisheries Genetic Laboratory, Marine Sciences and Technology Faculty, Iskenderun Technical University, 31220, Iskenderun, Hatay, Turkey. 2 Institute of Oceanology, Bulgarian Academy of Sciences, Department of Marine Biology and Ecology, Varna, Bulgaria. 3 University of Split, Department of Marine Studies, Split, Croatia Abstract Population structure of Atlantic Bonito Sarda sarda in the Mediterranean Sea and possible pathway of migration for spawning and feeding was discussed on the bases of genetic and morphological dataset. The effects of topographic and hydrographic factors on the connectivity and migration pattern of Atlantic Bonito in Turkish, Bulgarian and Croatian marine waters and fishery management implications of putative stocks were correspondingly referred. Keywords: Atlantic Bonito, Sarda sarda, genetic structuring, connectivity, migration pattern. Article history: Received 25 November 2016, Accepted 05 December 2016, Available online 07 December 2016 Introduction The Atlantic bonito Sarda sarda (Bloch 1973) is a commercially valuable small tunalike species, which occurs along the tropical and temperate coasts of the Atlantic Ocean, the Mediterranean Sea and the Black Sea and inhabit pelagic waters limited by the continental * Corresponding Author: Cemal Turan, e-mail: Natural and Engineering Sciences 57 shelf (Relini et al., 2005; Collette and Nauen, 1983; Turan et al., 2007). According to ICCAT 2013, the total catch of Atlantic Bonito is 10.019 t in Turkish Seas in 2011 and Turkey takes the first place in Mediterranean with this value (ICCAT, 2013). Atlantic Bonito mainly feed on anchovy, sprat, pilchard, horse mackerel, chup mackerel in Turkish marine waters. The fishery data of these species since 2002 obtained from DIE (2013) was investigated according to years that the catch amount of Atlantic Bonito was increased when anchovy stocks was being crushed in the fishing season 2005-2006 that Atlantic Bonito possibly cause the decline of anchovy stocks due to anchovy based feeding. Figure 1. The annual distribution of Atlantic bonito and other feed related species between 2002-2011 years in Turkish Seas. Little is known about Atlantic bonito migration patterns. Atlantic bonito migrates for feeding and spawning. Three separate spawning grounds are generally accepted to occur for the bonito in the Mediterranean Sea. The first and main spawning ground is the Black and Marmara Seas in the eastern Mediterranean (Yoshida, 1980; Rey et al., 1984). The area between Gibraltar, Balearic Islands and Algeria is the second spawning ground in the western Mediterranean (Rey et al., 1984). The third spawning ground is accepted to be in the northern Balearic Sea (Sabates & Recasens, 2001). Marine species usually reveal lower geographical differentiation than terrestrial species, as a result of lack of geographical barriers, large population sizes, high fecundity, wide range of distribution and long pelagic larval phase (Ward, 2000; Nielsen & Kenchington, 2001). Connectivity between populations is generally explained as the degree to which populations are considered to be open or close by gene flow and dispersal patterns (Hellberg et al., 2002; Palsbøll et al., 2007). Therefore, understanding the degree of connectivity and diversity are central issue for conservation, management and recovery of exploited stocks (Carvalho & Hauser, 1994; Schick & Lindley, 2007). There have been several population genetic and tag re-cupture studies for understanding degree of connectivity between populations of Atlantic Bonito in the Mediterranean Sea (Rey et al., 1984; Vinas et al., 2004; Turan et al., 2015). Turan et al. (2015) investigated population genetic structure and connectivity of Atlantic Bonito using mtDNA sequencing analysis in Turkish, Bulgarian and Croatian marine waters in the Adriatic Sea (Figure 2). Natural and Engineering Sciences 58 Figure 2. Sampling locations of S. sarda. The abbreviation of the samples as: BS1, the Black Sea Bulgarian Coast (Varna); BS2, the Black Sea Igneada; the Black Sea Duzce (BS3); the Black Sea Samsun (BS4); the Black Sea Trabzon (BS5); Istanbul Bosporus (BP); MS, Marmara Sea Bandırma; AS, the Aegean Sea Izmir; NMS1, the northeastern Mediterranean Sea Antalya Bay; NMS2, the northeastern Mediterranean Sea Iskenderun Bay; ADS, Adriatic Sea Croatian Coast. Taken from Turan et al. (2015). MtDNA analysis revealed that populations of Atlantic Bonito in Turkish coastal waters were divided into two genetically different two populations that Sarda sarda in the Black Sea and Marmara Sea comprise one genetic unit, and S. sarda in the Aegean and Mediterranean coast of Turkey constitute the genetically different second unit. On the other hand, the Adriatic Sea population from the Croatian coast was genetically different from the two genetically different populations in the Turkish coastal waters. This pattern of differentiation was also shown by multi-dimensional scaling analysis of the genetic distance between populations (Figure 3). Natural and Engineering Sciences 59 Figure 3. Multi-dimensional scaling plot of pairwise mtDNA D-loop sequencing differences between S. sarda populations. Taken from Turan et al. (2015). Turan (2015) also used microsatellite analysis to investigate population genetic structuring and connectivity between the geographically isolated Atlantic Bonito populations from Turkish, Bulgarian and Croatian marine waters, and found two genetically different population in Turkish coastal waters, first constitute the Black Sea and Marmara Sea population and the second comprise the Aegean and Mediterranean Seas populations. This pattern of differentiation according to microsatellite data was also shown by multidimensional Scaling analysis of the genetic distance between populations (Figure 4). Figure 4. Multi-dimensional scaling plot of pairwise microsatellite differences between S. sarda populations. Taken from Turan (2015). Natural and Engineering Sciences 60 We analysed also morphological characters such as morphometric and meristic o the same sample set. The Truss network system was used for morphometric analysis (Figure 5). Numbers of unbranched and branched rays in the first and second dorsal, first and second anal, pectoral, ventral fins and gill rakers on the upper limb and lower limb of the first gill arch, vertebrate numbers were obtained under a binocular microscope for the meristic characters. Figure 5. The Truss network system and eleven landmarks on Atlantic bonito for morphometric analysis. Only the Adriatic Sea sample from Croatian coast revealed morphological differences based on morphometric characters (Figure 6). Meristic analysis of the Atlantic bonito populations did not s (...truncated)