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Vimba Vimba vimba (L.) from the Rega River - support of natural spawning in 2004-2008 and the natural population

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Tanski A. , Czerniejewski P. , Keszka S. , Pender R. , Pilch E.

Baltic Coastal Zone. Journal of Ecology and Protection of the Coastline

2011

tom 15

The paper reports results of a study on the population of vimba in the Rega River aimed at localisation of the spawning sites and support of the natural reproduction by stocking. The spawning sites were localised with the help of electric catching and the coordinates were determined by GPS units. The fish caught to be used for artificial spawning (145 individuals) were measured (l.t. and l.c.) using an electronic calliper coupled with a PC unit. The sex of the fish was identified and on the basis of scale analysis the age and rate of length and mass increase were estimated. The backcalculation readings were made using the Rosa Lee method. The model of growth was established on the basis of the von Bertalanffy formula. Comparisons of groups of fish were drawn with the help of the nonparametric Mann Whitney U test. Correlations between variables were evaluated by analysis of regression, while the significance of the correlation coefficient was checked by t test. The rate of vimba mass increase was calculated using the modified von Bertalanffy formula was found to be described by Wt = 1215.103[1-e-0.133609(t+0.57322)]2.7559. The spawning sites of vimba localised in the Rega River section between Gryfice and Trzebiatow were concluded to be good sources of spawners for artificial spawning and the number of spawners caught in this section of the river ensures continuation of vimba restitution in the Rega River. The hitherto stocking measures aimed at restoration of vimba population have brought satisfactory results as evidenced by the age structure of the fish caught in the electric fishing in 2008.

Characteristics of brown trout [Salmo trutta m.fario L.] redds in selected streams of the Rudawa River basin

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Mikolajczyk T. , Witkowski G. , Gawlyta R. , Tyrcha K. , Mrozkiewicz S. , Sokolowska-Mikolajczyk S. , Epler P.

Archives of Polish Fisheries

2003

tom 11

nr 2

The quantity and characteristics of brown trout redds located in four streams of the Rudawa River basin in the Cracow Valleys Park (Park Dolinki Krakowskie) were investigated. The study was performed in late fall 2001 in the Będkówka, Kluczwoda, Racławka and Rudawka streams, all of which are left bank tributaries of the Rudawa River. A total of 328 redds were noted. The characteristics of twelve redds from each stream were described in detail, including water depth above the dome, water speed above the dome and the surface area of the redd. The contribution of certain gravel sizes in the composition of the domes was also investigated. There were no differences among the streams with reference to the surface areas of the redds or the water speed above the domes. The surface area of the redds ranged from 2081 to 3044 cm², while water speed above the dome varied from 73 to 82 cm s⁻¹. Significant differences in the water depth above the dome were noted among the different streams (from 12.58 cm in the Kluczwoda to 33.62 in the Rudawka). The contribution of fine gravel fraction (= 1 mm) also varied significantly among the streams. The highest sediment content was recorded in the Rudawka and Kluczwoda streams at 14.22 and 13.28% of the total weight of the gravel sample, respectively. This indicates that, despite the large number of redds in these watercourses, the final results of spawning could be very poor because of the probability of the asphyxiation of embryos by sediments. The Będkówka Stream is the most productive and promising trout spawning ground in the whole basin, and, as such, should be put under special protection.

Zewidencjonowano oraz scharakteryzowano gniazda tarłowe pstrąga potokowego zlokalizowane w potokach Parku Krajobrazowego „Dolinki Krakowskie". Obserwacji dokonano późną jesienią 2001 w potoku Będkowka, Kluczwoda, Racławka i Rudawka. Stwierdzono obecność 122 gniazd w Rudawce, 93 gniazda w Będkówce oraz 91 i 22 gniazda odpowiednio w Kluczwodzie i Racławce (tab. 1). Z każdego potoku wybrano losowo 12 gniazd, na których dokonano szczegółowych pomiarów. Zmierzono długość i szerokość gniazda, w celu obliczenia jego powierzchni, zmierzono głębokość i szybkość prądu wody nad kopcem gniazda. Ponadto pobrano próbki żwiru z gniazd, w celu określenia procentowej zawartości poszczególnych frakcji grubościowych żwiru w materiale skalnym tworzącym gniazdo. Powierzchnia gniazd wahała się od 2081 do 3044 cm² i nie stwierdzono różnic odnośnie powierzchni gniazd pomiędzy potokami (rys. 1). Nie stwierdzono również różnic pomiędzy potokami pod względem szybkości nurtu wody nad gniazdem, który wynosił od 73 do 82 cm s⁻¹ (rys. 3). Istotne różnice pomiędzy poszczególnymi potokami dotyczyły głębokości wody nad gniazdem (od 12.58 cm w Kluczwodzie do 33,62 cm w Rudawce, rys. 2) oraz udziału frakcji mulistych (< 1 mm²) w materiale skalnym tworzącym gniazdo: stwierdzono wysoką ich zawartość (ponad 13%) w gniazdach usytuowanych w potoku Rudawka i Kluczwoda (rys. 4), co wskazuje na możliwość obumarcia złożonej tam ikry z powodu upośledzenia wymiany wody w gniazdach i braku tlenu. Najlepsze parametry żwiru wykazywały gniazda z Będkówki. Z tego względu oraz z powodu obecności w nim dużej ilości gniazd, potok ten powinien być otoczony szczególną opieką.

Environmental conditions of common sturgeon [Acipenser sturio L.] spawning in River Rioni [Georgia]

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Kolman R. , Zarkua Z.

Electronic Journal of Polish Agricultural Universities. Series Fisheries

2002

tom 05

nr 2

Environmental conditions in River Rioni (Georgia) were studied in two seasons, during purported spawning migrations of the common sturgeon. Water temperature and flow velocity were measured in the vicinity of Poti (downstream section of the river) and in the potential spawning areas. At comparable times, water temperature in the spawning grounds was by a few degrees lower than that downstream, the flow velocity being higher and ranging within 1.5 - 2.1 m s-1. As shown by the observations, the area suitable for the sturgeon spawning had shrunk, possibly as a result of river damming. In the areas suitable for the common sturgeon spawning, the river bed was covered by coarse gravel and flattened stones, those measuring up to 30 mm in diameter being most abundant.