Influence of geographic origin on post-stocking survival and condition of European grayling (Thymallus thymallus) in a small river

The post-release survival and condition of 1+ year old European grayling Thymallus thymallus reared in a local (Husinec) and two 250–300 km distant, hatcheries (Pardubice and Hynčice) were evaluated by the recapture of tagged fish five months after release into the Blanice River, Czech Republic, the fish population of which was depleted by cormorant predation during several previous winters. The fish were marked using Visible Implant Elastomer tags and released into six sites along the river in May 2014: 100 locally sourced fish and 100 of a strain from a distant source per site. Significantly higher recapture of Husinec (33%) than Pardubice (20%) was found at one site but was offset by results in the remaining two sites into which they were stocked. Significantly higher site fidelity was shown by Husinec (12%) than Hynčice (7%) fish in the three sites. Lower initial weight and condition factor of the Husinec fish was equal to or higher than fish from the distant hatcheries at recapture. Some differences in final weight, length, and condition factor were found among groups regardless of release site. Lower recapture rate, growth, and condition were displayed in fish released into the three downstream sites (Husinec 1 and Hynčice). The results indicated the potential for successful use of non-autochthonous stock for grayling population recovery

Influence of geographic origin on post-stocking survival and condition of European grayling (

The post-release survival and condition of 1+ year old European grayling Thymallus thymallus reared in a local (Husinec) and two 250–300 km distant, hatcheries (Pardubice and Hynčice) were evaluated by the recapture of tagged fish five months after release into the Blanice River, Czech Republic, the fish population of which was depleted by cormorant predation during several previous winters. The fish were marked using Visible Implant Elastomer tags and released into six sites along the river in May 2014: 100 locally sourced fish and 100 of a strain from a distant source per site. Significantly higher recapture of Husinec (33%) than Pardubice (20%) was found at one site but was offset by results in the remaining two sites into which they were stocked. Significantly higher site fidelity was shown by Husinec (12%) than Hynčice (7%) fish in the three sites. Lower initial weight and condition factor of the Husinec fish was equal to or higher than fish from the distant hatcheries at recapture. Some differences in final weight, length, and condition factor were found among groups regardless of release site. Lower recapture rate, growth, and condition were displayed in fish released into the three downstream sites (Husinec 1 and Hynčice). The results indicated the potential for successful use of non-autochthonous stock for grayling population recovery

Response of Parasite Community Composition to Aquatic Pollution in Common Carp (<i>Cyprinus carpio</i> L.): A Semi-Experimental Study

The response of parasite communities to aquatic contamination has been shown to vary with both type of pollutant and parasite lifestyle. In this semi-experimental study, we examined uptake of pharmaceutical compounds in common carp (Cyprinus carpio L.) restocked from a control pond to a treatment pond fed with organic pollution from a sewage treatment plant and assessed changes in parasite community composition and fish biometric parameters. The parasite community of restocked fish changed over the six-month exposure period, and the composition of pharmaceutical compounds in the liver and brain was almost the same as that in fish living in the treatment pond their whole life. While fish size and weight were significantly higher in both treatment groups compared to the control, condition indices, including condition factor, hepatosomatic index, and splenosomatic index, were significantly higher in control fish. Parasite diversity and species richness decreased at the polluted site, alongside a significant increase in the abundance of a single parasite species, Gyrodactylus sprostonae. Oviparous monogeneans of the Dactylogyridae and Diplozoidae families and parasitic crustaceans responded to pollution with a significant decrease in abundance, the reduction in numbers most likely related to the sensitivity of their free-living stages to pollution

Evaluation of large-scale marking with alizarin red S in different age rainbow trout fry for nonlethal field identification

Fry of rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), was subjected to one-hour and four hours immersion in Alizarin red S (ARS) bath 150 mg · L–1. The experiment involved seven age groups (40, 50, 60, 70, 80, 90, and 100 days) and was conducted to estimate the minimal age of salmonids for mass marking with ARS bath enabling subsequent effective, simple field nonlethal identification, based on fin rays checking. The fish were examined at the ages of 200 and 300 days. The results showed a high retention level of ARS traces in caudal fin rays ensured satisfactory visibility and quick detection. A success rate of marking detection was >90% at 200 and 300 days of age and the fish were immersed in ARS solution from 60 days of age (685°D). This treatment provided better results in fish bathed for four hours. Recognition of marks using a laser pointer and protective glasses was successful even in fish, with a 3.5–5.0 times length increase compared to the marking time. The results indicate a high potential for ARS marking and its field identification for juvenile salmonids, which can significantly expand the possibilities of field experiments

Cardiac and Locomotor Responses to Acute Stress in Signal Crayfish Pacifastacus leniusculus Exposed to Methamphetamine at an Environmentally Relevant Concentration

Methamphetamine (METH), a central nervous system stimulant used as a recreational drug, is frequently found in surface waters at potentially harmful concentrations. To determine effects of long-term exposure to environmentally relevant levels on nontarget organisms, we analysed cardiac and locomotor responses of signal crayfish Pacifastacus leniusculus to acute stress during a 21-day exposure to METH at 1 &mu;g L&minus;1 followed by 14 days depuration. Heart rate and locomotion were recorded over a period of 30 min before and 30 min after exposure to haemolymph of an injured conspecific four times during METH exposure and four times during the depuration phase. Methamphetamine-exposed crayfish showed a weaker cardiac response to stress than was observed in controls during both exposure and depuration phases. Similarly, methamphetamine-exposed crayfish, during METH exposure, showed lower locomotor reaction poststressor application in contrast to controls. Results indicate biological alterations in crayfish exposed to METH at low concentration level, potentially resulting in a shift in interactions among organisms in natural environment