|
|
Struktura zooplanktonu v potravě cejna velkého (Abramis brama) v průběhu biomanipulace
Zapletal, T. ; Špaček, J. ; Jurajda, Pavel ; Všetičková, Lucie
The structure of zooplankton in diet of common bream (Abramis brama) was analysed in the Hamry water supply reservoir during the period 2011-2014. Fish were captured by gill netting, beach seining and electrofishing in the littoral part of reservoir. Minimum twenty specimens of each size group were taken for analysis on each sampling occasion. Zooplankton in the diet of adult bream SL 210-315 mm and subadult SL 124-186 mm made recedent proportion. Juvenile bream (0+) SL 18-51 mm consumed zooplankton only. Daphnia galeata was dominant there. We found that decrease of cladoceran communities in the water supply reservoir might to cohere (related) with this specific feeding activity of bream's fry and the feeding competition of bream's and perch's fry in it's habitats.
|
|
| |
|
|
Hlaváčovité ryby - potravní konkurenti našich původních druhů ryb?
Všetičková, Lucie ; Jurajda, Pavel ; Vašek, Mojmír ; Adámek, Zdeněk ; Roche, Kevin
To date, two species of the non-native Gobiidae family have been recorded in the Czech Republic: the tubenose goby (Proterorhinus semilunaris) and round goby (Neogobius melanostomus). The aim of this study was to assess the dietary habits of these two species, with the relationship between goby diet and that of native species (potential competition, predation) of particular interest. Early results suggest that the main dietary items of both gobiids are common benthic invertebrates such as Chironomidae, Trichoptera and Ephemeroptera. Fish eggs and fry were rarely taken by either species and, when taken, consisted almost exclusively of eggs and fry of their own species (cannibalism). In addition, the round goby was shown to be necrophagous, scavenging on large fish carcasses. This behaviour si relatively rare in the Czech fish assemblage. Our results suggest that tubenose and round goby, while not predating heavily on native benthivorous species, may still represent possible competitors.
|
|
|
Biomanipulační opatření na vodárenské nádrži Hamry - slabá odezva fytoplanktonu na redukci biomasy planktonofágních ryb
Jurajda, Pavel ; Adámek, Zdeněk ; Janáč, Michal ; Roche, Kevin ; Mikl, Libor ; Rederer, L. ; Zapletal, T. ; Koza, V. ; Špaček, J.
One measure commonly used for improving water quality in open waters is biomanipulation of fish stock. Previous studies in shallow lakes confirm the importance of reducing cyprinid populations for increasing zooplankton. Empirical results from reservoirs, however, are scarce. The aim of this study was to evaluate the effect of an intensive reduction of cyprinid fishes and perch fry density between 2009 and 2013 on water quality in the Hamry drinking water reservoir. The abundance of common bream broodstock decreased by around 12 000 individuals over the five years, and biomass dropped below 20 kg.ha-1. Stocking with pike and zander proved less effective. In reservoirs similar to Hamry, reduction of bream biomass can be a highly effective means of increasing filtering zooplankton biomass. Phytoplankton dynamics, however, appear to depend on additional factors, with nutrient loading (especially phosphorus) probably playing the primary role.
|
|
|
Populace sekavců na území České republiky
Halačka, Karel ; Vetešník, Lukáš ; Mendel, Jan
There are currently ongoing molecular genetic analysis specifies the characteristics of loachs in our territory. Monitored are individual populations in terms of their reproductive success and degree of threat. Significant are especially findings remains of the possible genome of C. taenia and C. tanaitica in some populations, whose presence will have to be clarified.
|
|
|
Růst značkované násady kapra obecného (Cyprinus carpio) ve vybraných údolních nádržích v povodí řeky Moravy
Prokeš, Miroslav ; Baruš, Vlastimil ; Habán, V. ; Mareš, J. ; Peňáz, Milan ; Halačka, Karel ; Krejčí, R. ; Vetešník, Lukáš
The project monitoring the growth of tagged two-season-old common carp (K2) being stocked into the selected reservoirs managed by the Moravian Angler Association was initiated in 2001 in the reservoir of Nové Mlýny. Few other reservoirs, namely the Dalešická, Brněnská, Vranovská and Letovická, were then also studied in course of the following period up today. The altitude of investigated reservoirs ranges 171-382 m a.s.l., the flooded area of water bodies 104-1600 hectares. The stocking series in every of reservoirs were performed in the course of subsequent five years and two thousands of tagged carps (K2) were always yearly stocked in every of reservoirs. In total, 50 335 (17.61 inds per hectare) tagged carps have been stocked and 1361 individuals (0.48 inds per hectare) were recaptured and reported by the anglers. The mean recapture rate of tagged fish reached thus 2.70 % (1.02 - 4.74 %). A significant negative relationship was also ascertained of altitude (in m a.s.l.) and growth indices. The maximum growth rate was found in the Novomlýnská reservoir (mean annual weight increment 1725 g). Gradually lower weight increments were found out in the Vranovská reservoir (1064 - 1200 g), Dalešická R. (1050 g), Brněnská R. (1070 g) and Letovická R. (630 g). A similar sequence existed also in growth of other parameters studied, i.e. total length (TL), specific growth rate (SGR), and weight condition expressed by means of the Fulton condition factor (FCF). On the basis of these results, some new, more convenient, rules were suggested for stocking of common carp.
|
|
|
Prostorová distribuce kaprů v polointenzivním rybníce
Mrkvová, Markéta ; Zukal, Jan ; Adámek, Zdeněk ; Šútovský, I. ; Jurajda, Pavel
In semi-intensive pond aquaculture, the dietary requirements of the species cultured (mainly carp Cyprinus carpio) are guaranteed through consumption of natural food organisms together with "supplementary" feed inputs. As a result, we hypothesise that carp will utilise the whole area of the pond in their search for those places where natural food is available. To date, there has been no in-depth study on fish behaviour and feeding habits in such ponds, despite the possibility of food competition where fish are stocked at high densities. Such competition could lead to decreased growth in younger fish cohorts, leading to poorer flesh quality. In this study, we use radio-telemetry to provide new information on carp behaviour in a 130ha pond under semi-intensive aquaculture. Our results indicate that fish distribution in the pond is uneven, with fish using approximately two-thirds of the pond area. This behaviour was partly influenced by size-class. Some fish tended to remain at localities where supplementary food was regularly provided, but some of them used both localities with supplementary and natural food. These results should prove useful for improving fish feeding regimes in ponds using a similar semiintensive system to our model pond.
|
|
| |
host ::
RSS.