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Background. Roach, Rutilus rutilus, comprise a large proportion of the total catch in the Szczecin Lagoon, and are caught mainly as bycatch in gillnets targeting perch, Perca fluviatilis. The minimum landing length for roach and perch is 17 cm TL and the minimum mesh size is 30 mm bar length. However, little is known about the selectivity of roach, which may have implications for implementing effective regulations. Consequently, the aims of the study were to estimate roach selectivity curves and to compare the results with perch selectivity. Materials and Methods. The study was based on the length frequency of catch from standardized fishing practice with commercial gillnets of mesh sizes ranging from 25 to 35 mm (bar length) and modelled using various generalized linear models. The best model was selected using deviance criteria. Results. The log-normal selectivity model provided the best fit, with spread relevant to mesh size under the assumption of equal fishing power. The estimated parameters were 18.7 cm and 1.5 (mode and spread of selectivity curve for the smallest mesh size). Conclusion. Although the most efficient mesh size for roach was 26 mm, its use in the Szczecin Lagoon is limited by impact on perch. All the studied mesh sizes prevented catches of undersized roach, while mesh sizes from 28 mm prevented catches of undersized perch (MLL = 17 cm TL). The authors concluded that the current 30 mm minimum mesh size is likely effective at preventing the harvest of undersized perch and roach.
A new locality of the Asian thermophilic aquatic oligochaete Branchiura sowerbyi Beddard, 1892(Oligochaeta, Naididae) was recorded in the Upper Oder River. Until now, this species has been only noted in a few localities in Poland: in the Szczecin Lagoon at the mouth of Oder River to Baltic Sea, in the heated Konin lake system (West Poland) and in the middle course of the Oder River. In our study, B. sowerbyi was found on one site (108 km of the river course) that is located more than 400 km from its previous recordings in the Oder River. This finding may show that B. sowerbyi has spread upstream. It should be noted that, as a rule, low abundance of this species may be the reason for the small number of its recordings, so further studies related to distribution and impact of B. sowerbyi on native oligochaetes are needed.
The stonewort Chara connivens was rediscovered in the Vistula Lagoon in 2011, almost 35 years after its last record. In 2012, the species was recorded for the first time in the Szczecin Lagoon. Chara connivens occurred at shallow (0.5–1.2 m) sandy-muddy and muddy bottoms of small embayments. In the Vistula Lagoon, the stonewort was represented by single small specimens, while in the Szczecin Lagoon, it formed dense and extensive patches.
This paper presents the results of studies of the levels of heavy metals, organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in the gonads of pikeperch females from the Szczecin, Vistula and Curonian lagoons. This study determined that the levels of heavy metals such as Zn, Cu, Pb and Cd and those of organochlorine pesticides and polychlorinated biphenyls occur in pikeperch gonads in different quantities depending on the region studied. The highest level of zinc was recorded in pikeperch gonads from the Szczecin Lagoon, and the highest levels of copper were noted in those from the Vistula Lagoon. The highest levels of S HCH occurred in the gonads of Vistula Szczecin pikeperch.
seventeen early medieval sedimentary layers of the port of the town of Wolin, corresponding chronologically with the time period from the beginning of the 9th till the middle of the 13th century, the occurrence of 3 537 bone remains was stated, of which 2 784 pieces had their anatomy determined. In the identified archaeological material 33 types of bones were found, belonging to 15 species of teleost fishes, as well as 4 kinds of common sturgeon remains (Acipenser sturio). The bones of viscerocranium, mainly of zander (Stizostedion lucioperca), bream (Abramis brama), and perch (Perca fluviatilis), were dominant (57.23%).
The study involved analysis, performed with standard methods, of length and weight growth of 202 perch individuals caught in November 1999 from the Szczecin Lagoon. The verge coefficient was factored in both when determining the age distribution and when analysing length and weight growth by calculating mean values in age groups (when Kr > 0.50, the number of annual rings was increased by 1).
A newcomer to the Baltic Sea, the Chinese mitten crab is especially abundant in the Szczecin Lagoon (NW Poland), where it was first reported in 1927. Body weight, and carapace width and length, were studied in 647 individuals collected with fyke nets in the Szczecin Lagoon from 30 March – 18 April2001 and from 5–21 November 2001. 51.01% of the 543 autumn specimens were males, but only 30.97% of the 113 spring specimens were males. Body weight varied from 45.1 to 306.5 g, carapace length from 41.07 to 81.02 mm and carapace width from 46.68 to 88.85 mm. The autumn crabs were significantly heavier than the spring specimens.
Selected biological and morphometric characters of two populations of the nonindigenous Chinese mitten crab,one from the Szczecin Lagoon (SL) and the other from San Francisco Bay (SFB),b oth sampled in autumn, were analysed. The SL crabs showed a significantly higher individual weight,l ength and carapace width. Males accounted for 55% (87 individuals) of the 179 SL crabs,an d 62.9% (90 individuals) of the SFB crabs. Statistical analysis of metric characters,expr essed as a percentage of carapace width (X2),en abled four diagnostic characters to be identified: abdomen width (X11),carapace height (X3),left claw length (X7) and carapace length (X1). These jointly explain 71.75% of the differences between the SL and SFB crabs and are indicative of the distinctness of the populations.
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