Effects of oxazepam concerning on social behavior in guppies are still unknown. The purpose ofthis thesis is to investigate if the benzodiazepine oxazepam has effects on fish behavior in terms ofsocial preferences and responses to predation risk using an olfactory cue mixture. After anexposure period of 15 days to 100 μg/l of oxazepam, behavioral experiments were performed overtwo days. Results indicate that oxazepam exposed fish were more social at the beginning of theexperiment, which differ from what was expected and from previous social preferences studies.Moreover, less social behavior was found as a result of combining oxazepam treatment andolfactory cue mixture (predator cues and guppy skin extract) treatment.

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Predator cues can influence how aquatic organisms respond to anthropogenic contaminants. This study examined the effects of predator cues on behavior, metabolic rate, and sulfate (as Na2SO4) toxicity in amphipods (Gammarus minus). Predator cues included alarm cue (macerated conspecifics) and kairomone from mosquitofish (Gambusia affinis). Amphipods decreased activity and increased time in refuge when exposed to alarm cue, and increased time in refuge when exposed to kairomone. While median lethal concentrations (96-h LC50) were not influenced by predator cues, analysis of dose response curves indicated that kairomone exposure increased amphipod sensitivity to mid-range concentrations of sulfate (500-1,000 mg/L). Amphipods increased oxygen consumption in response to kairomone but not alarm cue. The influence of predator cues on contaminant lethality can be dependent on the type of cue, and physiological endpoints such as metabolic rate may help explain the basis of observed interactions.

The ability of prey to detect and respond appropriately to predator risk is important to overall prey fitness. Many aquatic organisms assess risk through the use of chemical cues that can change with predator diet. Two variable characteristics of diet are: 1. prey type and 2. prey mass. To assess the effect of these two characteristics on the assessment of risk by the mud crab Panopeus herbstii, I exposed mud crabs to the urine of the blue crab Callinectes sapidus fed one of 5 diet treatments: 10g of oyster shell free wet mass, 5g of oyster shell free wet mass, 10g crushed mud crabs, 5g crushed mud crabs, and a mix of 5g of oyster shell free wet mass and 5g crushed mud crab. Effects on P. herbstii foraging were tested in a previously developed bioassay by measuring shrimp consumption over a 4 hour period. I hypothesized that P. herbstii would have a larger magnitude response to urine from C. sapidus fed a diet of crushed mud crabs than to urine from C. sapidus fed a diet of oysters. I further hypothesized that P. herbstii would have a larger magnitude response to urine from C. sapidus fed a high mass diet relative to a lower mass diet. Contrary to expectations there was no observed effect of urine on P. herbstii foraging in any of the treatments. Results suggest that bioassay protocol may be unreliable suggesting further replication to determine the difference between this study and previous results. Future studies examining how P. herbstii varies with urine concentration will aid in understanding the ecological scale of this predator cue system. Determining the role of other potential cue sources will improve the predictive abilities of these studies.

Biological invasion is a strong threat to native biodiversity, with limnic systems being especially vulnerable due to historical separation and resulting prey naivety. The prey naivety hypothesis states that native species may not be able to recognize novel predators due to a lack of common evolutionary background and, therefore, become easy targets. In a laboratory experiment, we added cues of native European bullhead (Cottus gobio Linnaeus, 1758) and invasive round goby [Neogobius melanostomus (Pallas, 1814)] to Ancylus fluviatilis Müller, 1774 originating from two different populations within the same river (one naive, one experienced towards round goby) and compared their predator avoidance behavior. Individuals from both populations recognized cues from the known predator C. gobio and reduced their locomotive activity. To round goby cues, however, naive individuals did not respond, thereby supporting the prey naivety hypothesis. Experienced individuals, in contrast, reduced their activity, suggesting a learning effect due to the co-occurrence of invasive predator and prey. At fast moving invasion fronts of highly invasive species like N. melanostomus, prey naivety can, hence, enhance their negative impact on ecosystems. Behavioral adaptation of native species resulting in predator avoidance reactions could, therefore, play an important role in ecosystem resilience and temporal invasion dynamics.