Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Określenie wieku kozy (Cobitis taenia) i kozy złotawej (Sabanejewia aurata) z wykorzystaniem niektórych struktur twardych

Lampart-Kałużniacka M., Pietraszewski D., Marszał L., Heese T., Przybylski M.

Rocznik Ochrona Środowiska

2013

Tom 15, cz. 2

1041--1052

Age is one of the most important life history variables of fish used to estimate growth rate, mortality rate and production. Age determining is usually carried out by analyzing any of several calcified structures, such as scales, otoliths (more frequently) or fin rays (rather seldom). Scales are easy to collect and this is the reason why this structure has been widely used, but for several reasons annuli may be ambiguous to discern on scales, especially in the loaches. The material was collected in May 2010 in the Pilica River. A total of 29 fish individuals, including 16 spined loach and 13 golden loach, were examined. The range of total length (TL) of the fishes in the sample studied was 43–102 mm in the former and 35 do 70 mm in the latter species, respectively. The precision of ageing using the cross-sections of dorsal, caudal, anal, pectoral and ventral fins rays were compared with age determination on the basis of otoliths. The analysis of the annuli of the investigated structures revealed that individuals aged 2 to 5 years (golden loach) and aged 3 to 7 years (spined loach) occurred in the material (Table 1 and 2, respectively). The obtained results indicate that in natural water bodies older individuals than formerly presumed may occur. Microscopic slides of the cross sections of otoliths and fins are most reliable for ageing such structures. The anal fin (A) it the most reliable structure for ageing, i.e. the age obtained from the fin is least divergent from the age obtained from the otolith. While planning the investigations of the age structure of populations it is necessary to establish the periods of sampling in a way that will be most congruent with the period of annuli formation.

The food preferences of three-spined stickleback, Gasterosteus aculeatus L., downstream from a dam reservoir

Dukowska M., Grzybkowska M., Marszał L., Zięba G.

Oceanological and Hydrobiological Studies

2009

Vol. 38, No.2

39-50

Submersed plants appeared in the impounded section of the Warta River as a consequence of low discharge in summer and were colonized by epiphytic fauna dominated by Hydra sp., Simuliidae, and Chironomidae. The three-spined stickleback consumed it voraciously, and their diet composition closely reflected the available food resources. In May their alimentary tracts were filled with Cladocera drifting from the reservoir, and then by the dominant taxa associated with macrophytes, especially chironomid periphyton scrapers. A comparison of dipteran head capsule width in the food resources and in the alimentary tract proved the three-spined stickleback preference for the largest larvae (optimal foraging strategy).