Linas Ložys

Seasonal Migrations of Pikeperch (Sander Lucioperca L.) from the Curonian Lagoon to the Baltic Sea and Advantages of the Phenomenon

The Curonian Lagoon is a fresh water basin. Pikeperch is a common fish species in this water body. Part of pikeperch population after wintering and spawning migrates from the Curonian Lagoon to the brackish Baltic Sea, however the cause of those migrations has been unknown. The results of the study demonstrate beneficial effect of the brackish surroundings to the growth of pikeperch, despite lower water temperature and higher water transparency. According to other studies, higher water temperature, water turbidity and good feeding conditions are the predominant factors influencing pikeperch growth, while water salinity has actually been neglected in pikeperch ecology studies during the last decades. Beneficial effect of summer in brackish surroundings is a pattern of pikeperch seasonal migration phenomenon.

The Nutrition of Fish in the Curonian Lagoon and the Coastal Zone of the Baltic Sea

We investigated the nutrition of 13 fish species inhabiting the Curonian Lagoon. The research material was obtained in the areas of Ventė Cape, Dreverna and Kiaulės Nugara in the spring, summer and autumn of 1996, 1998 and 1999. Altogether, the intestinal tracts of 539 fishes were investigated. In the coastal zone of the Baltic Sea, the nutrition of 11 fish species was investigated. The research was carried out at the Klaipėda Strait and in the sea sections of Klaipėda-Giruliai and Klaipėda-Nida in April-August. The total number of 345 specimens was investigated. It was established that the main food components of roach and silver bream in the middle and northern parts of the Curonian Lagoon are molluscs (Dreissena), Chironomidae larvae, zooplankton and plants. The nature of nutrition of bream, vimba, pike-perch and perch depends on the biotope and various environmental conditions. In the Curonian Lagoon, the main food components of bream are molluscs, zooplankton and detritus. The main food components fo...

Seasonal dynamics in the diet of pelagic fish species in the southwest Baltic Proper

Egl_ e Jakubavi ci ut _ e*, Michele Casini, Linas Lo zys and Jens Olsson Nature Research Centre, Akademijos 2, Vilnius 08412, Lithuania Department of Aquatic Resources, Institute of Marine Research, Swedish University of Agricultural Sciences, Lysekil 45330, Sweden Department of Aquatic Resources, Institute of Coastal Research, Swedish University of Agricultural Sciences, Skolgatan 6, € Oregrund 742 42, Sweden *Corresponding author: tel: þ370 5 272 92 84; fax: þ370 8 5 272 93 52; e-mail: ejakubaviciute@ekoi.lt

Do otolith annular structures correspond to the first freshwater entry for yellow European eels Anguilla anguilla in the Baltic countries

To examine the relationship between freshwater entry and otolith annular structures, a total of 113 naturally recruited European eels Anguilla anguilla from Lithuania and Latvia that entered fresh water at least once were collected. In some individuals (8.3-11.3%), the first freshwater entry coincided with a dark check that was distinctly different from neighbouring annuli. In most individuals (81.7-84.9%), the first freshwater entry occurred on rings and increments indistinguishable from other annuli. For the remaining individuals (3.8-10%), the first freshwater entry did not correspond to any otolith ring, band or annulus. According to recent evidence, the observed high correspondence between the first freshwater entry and otolith annuli was more likely due to the movement into fresh water during winter when the annulus was deposited, rather than stress resulting from habitat change. Consequently, the age estimation based on otoliths might be less influenced by this habitat change during the yellow eel stage.

INVESTIGATION OF GENETIC VARIABILITY IN THE EUROPEAN EEL (ANGUILLA ANGUILLA (L.)) IN LITHUANIA USING MICROSATELLITE DNA MARKERS

To find out if native and introduced European eel (Anguilla anguilla) populations differ from one another genetically, we used five microsatellite markers and compared naturally recruited and introduced European eel populations at four different locations. Samples of naturally recruited eels were taken from the Baltic Sea and the Curonian Lagoon, while introduced eels were sampled from Lakes Dringis and Siesartis. Results of the study do not support the hypothesis on panmixia in the European eel, since low but significant genetic differentiation (FST = 0.0238, p = 0.0148) was found to exist among introduced eel groups. Significant genetic differentiation (FST = 0.0228, p = 0.0281) among the Baltic Sea, the Curonian Lagoon, Lake Dringis and Lake Siesartis populations was ascertained too.

Species Composition and Abundance of Fish in Shallow Waters of the Lithuanian Coastal Zone in the Baltic Sea

During the 1989–2001 investigations of fish communities in shallow waters of the Lithuanian coastal zone in the Baltic Sea there were approximately 19,000 fish individuals representing 22 species and belonging to 13 families caught with a beach seine. Catches were most often dominated by smelt, Baltic sprat, flounder, three-spined stickleback and small sand eel. Smelt, flounder, vimba, turbot, perch and pikeperch juveniles stood out because of their biomass. The highest fish concentrations in the coastal zone were observed in summer months, especially in August. In the Lithuanian coastal zone fish abundance and biomass are the greatest to the north of Palanga. That is mainly related to the extremely great concentration of smelt and Baltic sprat juveniles. Fluctuations in the abundance of fish juveniles (smelt, turbot, flounder etc.) observed in different years are most often linked to spawning conditions and ever-intensifying commercial fishing in the coastal zone. A reliable relation has been established...

Parameterization of European perch Perca fluviatilis length-at-age data using stochastic Gompertz growth models

Three stochastic versions of the Gompertz growth model were used to parameterize total length (L(T) )-at-age data for perch Perca fluviatilis, an important target species for commercial and recreational fishers and a food species for predatory fishes and aquatic birds. Each model addresses growth heterogeneity by incorporating random parameters from a specific positive distribution: Weibull, gamma or log-normal. The modelling outputs for each version of the model provide L(T) distributions for selected ages and percentiles of L(T) at age for both males and females. The results highlight the importance of using a stochastic approach and the logistic-like growth pattern for analysing growth data for P. fluviatilis in Curonian Lagoon (Lithuania). Outputs from this modelling can be extended to a stochastic analysis of fish cohort dynamics, incorporating all length-based biological relationships, and the selectivity-related interactions between fish cohorts and fishing gear.

Armed Bullhead (Agonus Cataphractus) – a New Fish Species in the Lithuanian Coastal Zone of the Baltic Sea

In February–April 2000 in the coastal zone of the Baltic Sea even three individuals of the new fish species, hitherto unregistered in Lithuania, were caught by commercial fishermen. These were specimens of armed bullhead (Agonus cataphractus) widespread in the area stretching from the coastal zones of La Manche (the English Channel) and the North Sea to the western part of the Baltic Sea. It is a common fish species in the littoral area of Iceland and Norway, found near Great Britain, the Faeroes Islands, the Shetland Islands, in the western part of the Baltic Sea and the White Sea. Several individuals have been registered in the coastal zones of Poland and the Kaliningrad Region, near Gotland island. One specimen of this fish has been preserved and handed over to us by fishermen.

Isoenzyme Analysis of Percids (Stizostedion Lucioperca, Perca Fluviatilis, Gymnocephalus Cernua) in LithuaniaCoastal Zone of the Baltic Sea, the Curonian Lagoon and Kaunas Water Reservoir

The isoenzyme analysis of percids in the Curonian Lagoon and coastal zone of the Baltic Sea was performed during 1999-2000. The liver tissue homogenate was used for the investigations. Isoenzyme analysis was carried out by electrophoresis in polyacrylamide gel (PAA) method. After investigating three populations of percids according to five enzyme systems it has been established that four (MDH, ME, XDH, G-6-PH) were monomorphic and only one (EST) polymorphic. Four loci (EST-1, EST-2, EST-3, EST-4) with 2-7 different alleles were found in esterase polymorphic system. The highest number of alleles and genotypes has been established for the four loci of the Curonian Lagoon populations, and only for ruffe population of EST-4 locus at Kaunas water reservoir. It is evident that the Curonian Lagoon populations distinguish by their high genetic diversity.