The Atlantic cod (Gadus morhua L.) is one of the most ecologically and economically important marine fish species in the North Atlantic Ocean. Using Roche GS-FLX 454 pyrosequencing technique 962,516 reads, representing 379Mbp of the Baltic cod transcriptome, were obtained. Data was assembled into 14,029 contigs of which 100% displayed homology to the Atlantic cod transcriptome. Despite a high similarity between transcripts, evidence for significant differences between Baltic and Atlantic cod was found.

The Baltic is a semi-enclosed sea characterised by decreasing salinity in the eastern and northern direction with only the deeper parts of the southern Baltic suitable as spawning grounds for marine species like cod. Baltic cod exhibits various adaptations to brackish water conditions, yet the inflow of salty North Sea water near the bottom remains an influence on the spawning success of the Baltic cod. The eastern Baltic population has been very weakly studied in comparison with the western population. The aim of this study is to demonstrate for the first time genetic differentiation by the use of a large number of SNPs between eastern and western Baltic populations existing in differentiated salinity conditions. Two cod samples were collected from the Bay of Gdańsk, Poland and one from the Kiel Bight, Germany. Samples were genotyped using a cod derived SNP-array (Illumina) with 10 913 SNPs. A selection of diagnostic SNPs was performed. A set of 7944 validated SNPs were analysed to assess the differentiation of three samples of cod. Results indicated a clear distinctness of the Kiel Bight from the populations of the eastern Baltic. FST comparison between both eastern samples was non-significant. Clustering analysis, principal coordinates analysis and assignment test clearly indicated that the eastern samples should be considered as one subpopulation, well differentiated from the western subpopulation. With the SNP approach, no differentiation between groups containing 'healthy' and 'non-healthy' cod individuals was observed.

Anisakids of Scomber japonicus, Trachyrincus scabrus, Sardina pilchardus, Merluccius polli, Trachurus trachurus, and Hoplostethus cadenati from African shelf are reported. Parasites were extensively studied with respect to their morphology and sequence analysis of the rDNA fragment (containing internal transcribed spacer [ITS]-1, 5.8S subunit and ITS-2); all of them are approximately 1,000 base pairs. Digestion of the amplified region and its sequencing revealed the presence of a sibling species (A. simplex s.s. and A. pegreffii). Still other sequences represented closely related, but not sibling, species, i.e., Anisakis brevispiculata, A. ziphidarum, and A. physeteris; there were also 2 undescribed anisakid species. These species were temporarily described as Anisakis sp. HC-2005 and Anisakis sp. MP-2005 (found, respectively, in Hoplostethus cadenati and Merluccius polli). The study shows that the parasitic fauna of fishes reflects not only the geographic range of anisakid nematodes but also the feeding behavior of the hosts serving as links in the parasites' life cycles.

Kijewska, A., Burzyński, A., and Wenne, R. 2009. Molecular identification of European flounder (Platichthys flesus) and its hybrids with European plaice (Pleuronectes platessa). – ICES Journal of Marine Science, 66: 902–906.

Atlantic cod (Gadus morhua) occur in marine water of different salinities: from oceanic waters at salinity of 35 to Baltic Sea waters where the lowest level of salinity reaches 5–6. The stress response to different salinities in the eastern and western Baltic cod populations was examined. Two genes of Na+, K+ -ATPase 1a (atp1a) and heat shock protein 70 (hsp70) expression, plasma cortisol and osmolality were used as markers of osmotic stress to characterize the reaction profiles of two populations of G. morhua from the western and eastern parts of the Baltic Sea. Atlantic cod were sampled in November 2012 from western Kiel Bight (KIEL, salinity of 18) and eastern Gdańsk Bay (GDA, salinity of 8). Live fish were transported to the Marine Station of the University of Gdańsk in Hel and were settled in tanks (3500L). Cod were kept at 10°C in recirculated water, which simulated the natural salinities of the geographic source region of the fish. Results showed that in the reduced and elevated salinity water of the KIEL group, we observed no change in expression of atp1a and slightly increased expression of hsp70. In the GDA group, there were no significant changes of hsp70 expression but the level of atp1a was significantly increased in both salinities. In both groups, concentration of cortisol increased after exposure to elevated salinity, while in fish exposed to reduced salinity, a significantly higher concentration of cortisol was observed after 72h. The high expression of atp1a that observed in the eastern group (GDA) supports the thesis of a genetic background to the adaptation to variable salinity. This adaptation may protect this species against an osmotic stress caused by daily vertical migrations and long-distance migration to spawning areas. At the same life-time, salinity is a barrier maintaining the genetic and physiological separations between G. morhua stocks and affecting the structure of this fish subpopulation in the Baltic Sea