Search

The period of larval drift into a suitable nursery area is considered to be of great significance for recruitment variability in flatfish. Here, a hydrodynamic model coupled with a Lagrangian particle tracking technique was utilized to study the drift from the first feeding larval stage until time of settlement of Central and Eastern Baltic flounder (Platichthys flesus), originating from spawning in the Baltic Sea deep basins, the Arkona- and Bornholm basin (central Baltic Sea), and the Gdansk deep and Gotland basin (eastern Baltic Sea). We examined the spatio-temporal dynamics of the probability to settle in preferred nursery habitat by detailed drift model simulations. The study suggests that the majority of larvae (89% and 74% for Central- and Eastern Baltic flounder, respectively) drift towards coastal areas and settle at metamorphosis ≤20 km from a sandy habitat enabling further migration to a preferred nursery area, i.e. larval drift seems not to be a major bottleneck in recruitment of flounder spawning in the Baltic Sea deep basins. The drift model results suggest that Central Baltic flounder utilize nursery areas mainly in the central and western Baltic, and in the Kattegat, whereas Eastern Baltic flounder mainly utilize the coast in the central and eastern Baltic. Thus, the two stock components seem to use different nursery areas following settlement. Further, in accordance with the “nursery size hypothesis”, the model demonstrates that larvae from the Bornholm basin, utilizing areas with extensive distribution of preferred nursery habitat, display the highest relative successful transport to nursery grounds until settling (72% of successfully settled larvae), suggesting that spawning in the Bornholm Basin is of great importance for stock recruitment of deep basin spawning Baltic flounder.

In the Baltic, the first observation of the round goby (Neogobius melanostomus, Pallas 1814) was made in 1990. Within the past decade the species became invasive and spread rapidly throughout the Baltic Sea. Studies about the fishes potential impacts on resident species promote the need for an increasing knowledge of their basic stock structures such as growth rates, longevity and mortality, which all rely on accurate estimates of age. Former studies on the round goby have used several different age reading techniques. In this study, we compared three standard otolith preparation methods for ageing and present the best procedure for the invasive round goby. The results showed significant differences in age estimates of the same fish between the different preparation methods and between readers. The estimation of the first annulus, the first year, was the most problematic. The overall agreement was lowest when reading the whole otoliths while the best performance was achieved with sectioned and stained preparation method. Depending on method used the growth estimates also differed. The results question comparability between previous studies and highlight the importance of harmonised aging procedures for the round goby for obtaining correct estimates of population parameters such as growth rate, age at maturity, and longevity.

Stocks of whitefish (Coregonus maraena) in the northern part of the Baltic Sea have in many areas declined drastically during recent years. Causes for the decline are yet not fully understood, but knowledge on the genetic population structure of the species is pivotal for future conservation measures. In this study we analyse the genetic variation at seven microsatellite loci for whitefish from 18 different sites along the Swedish coast of the Baltic Sea. We found a strong dependence of isolation by distance (R = 0.73), and a week but rather fine scaled genetic structure. In addition, there were differences between more northern and southern sites in the population genetic structure, where the degree of differentiation appears to be stronger in the north compared to the south. The results suggest that whitefish is a species suitable for local management with a regional context of the management strategy. In addition, the findings corroborate what is previously known for other coastal fish species in the Baltic Sea, such as perch and pike, suggesting that the majority of gene flow occurs between adjacent areas. Finally, our results highlight the potential for genetic subdivision even when the dependence of isolation by distance is strong., 5

In this study, the genetic variation of perch Perca fluviatilis from 18 different sites along the Swedish coast of the Baltic Sea was assessed. There was a relative strong support for isolation by distance and the results suggest an overall departure from panmixia. The level of genetic divergence was moderate (global FST = 0·04) and indications of differences in the population genetic structure between the two major basins (central Baltic Sea and Gulf of Bothnia) in the Baltic Sea were found. There was a higher level of differentiation in the central Baltic Sea compared to the Gulf of Bothnia, and the results suggest that stretches of deep water might act as barriers to gene flow in the species. On the basis of the estimation of genetic patch size, the results corroborate previous mark–recapture studies and suggest that this is a species suitable for local management. In all, the findings of this study emphasize the importance of considering regional differences even when strong isolation by distance characterize the genetic population structure of species.

We review published records of laboratory experiments on peripatric and vicariance allopatric speciation to address the following three questions: (1) What was the true effect size of reproductive isolation? (2) Was the reproductive isolation persist

The Kaneshiro model proposes a role for sexual

Laboratory experiments designed to elucidate the mechanisms of sympatric and parapatric speciation may have been handicapped by too small population sizes, although this possibility has seldom been discussed. In this paper we review the published rec, Addresses: Odeen A, Uppsala Univ, Evolutionary Biol Ctr, Dept Anim Ecol, Norbyvagen 18 D, SE-75236 Uppsala, Sweden. Uppsala Univ, Evolutionary Biol Ctr, Dept Anim Ecol, SE-75236 Uppsala, Sweden.