16 August 2023

Kaur and colleagues 2023

Cover to Ecology and Evolution, Volume 13, Number 8

Kaur D, Iqbal A, Soto I, Kubec J, Buřič M. 2023. Effects of chemical cues and prior experience on predator avoidance in crayfish. Ecology and Evolution 13(8):e10426. https://doi.org/10.1002/ece3.10426


Multisensory stimuli provide organisms with information to assess the threat present in the surroundings. Olfactory cues show dominance over other sensory modalities in the aquatic environment. The impact of chemical predator cues combined with experiences gained (learning) in species without previous contact is not fully understood. We investigated the foraging and shelter-seeking behaviour of naïve and experienced marbled crayfish Procambarus virginalis juveniles in response to the chemical signals of pumpkinseed Lepomis gibbosus alone and in combination with alarm chemicals produced by preyed-upon conspecifics. Naïve and experienced (previously exposed to pumpkinseed predation) juveniles were stocked in an arena with shelter and feed and exposed (1) to water from a tank containing a predator actively feeding on conspecifics, (2) water from a tank with predator only and (3) water only as control. Crayfish exposed to the combined stimuli avoided the inlet zone and gravitated to shelter zone of the arena to a greater extent than did those exposed to predator-only cues and the control. Regardless of the treatment, experienced crayfish showed significantly reduced interest in feeding. Our findings imply that crayfish response to threat-associated odours with the greatest potency when visual or tactile cues are present, while previous encounters with predators may make them more cautious.  

Keywords: alarm cues • crayfish • fish • infochemicals • kairomones • predation

Open access

05 August 2023

Be on the lookout for Marmorkrebs, Ontario! Marmorkrebs finally found in North America

Marbled crayfish recovered from pond in Burlington, OntarioBurlington Today is reporting that Marmorkrebs have been found in Burlington, Ontario.

The details are hazy.


Marbled crayfish – an aquatic invasive species that is prohibited in the province – has been found in the Burlington area.


That’s the extent of actual reporting. The rest of the article is background information.

Edit, 6 August 2023: A Burlington Post article is a little more expansive.  It gives a general location (a city park).

Previously, another marbled crayfish was reported in the area on iNaturalist. (I actually went to where the iNaturalist sighting was to look around, but heard people had already looked and found nothing.) 


This Burlington marbled crayfish sighting is also on iNaturalist, from Premek Hamr, also known as “Dr. Crayfish.” Premek has extensive experience with Ontario crayfish, so it’s not as though this is an Ontario native being misidentified.


On Twitter, Hamr has been sharing pictures of multiple individuals, including juveniles. This indicates there is a breeding population at this location.


Ontario just banned marbled crayfish last year.

While this is a watershed moment in the worldwide invasive status of marbled crayfish, it is something that has been expected for a long time. It’s mostly surprising in that it didn’t happen a few years ago.

The map of Marmorkrebs introductions has been updated.

External links

Marbled crayfish sighting in iNaturalist


Premek Hamr on Twitter: Onetwo , three, four


Be on the lookout for marbled crayfish in the Burlington area (Burlington Today)


‘Capable of cloning’: Invasive crayfish found in Burlington pond (Burlington Post)

‘Capable of cloning’: Invasive crayfish found in Burlington pond (Hamilton Spectator

Ontario Natural Resources and Forestry on Twitter

Related posts

Ontario prohibits Marmorkrebs

01 August 2023

Musil and colleagues 2023

Scientific Reports

Musil M, Let M, Roje S, Drozd B, Kouba A. 2023. Feeding in predator naïve crayfish is influenced by cues from a fish predator. Scientific Reports 13: 12265. https://doi.org/10.1038/s41598-023-39406-w


In this study, we experimentally evaluated how the feeding behaviour of marbled crayfish Procambarus virginalis is influenced by cues from conspecifics and the round goby Neogobius melanostomus, a fish predator, in tanks that permitted chemical communication but not visual recognition. We used four experimental groups with different combinations in two sub-tanks. The first sub-tank always contained a crayfish and prey (40 individuals of the water louse Asellus aquaticus). The other sub-tanks were set up as follows: (i) empty, serving as a control (C); (ii) with a conspecific crayfish (Cr); (iii) with a round goby (G) to simulate predator-only odour; and (iv) a round goby and three small conspecific crayfish (G + Cr) to simulate the presence of a predator and/or the alarm odour. Two sub-treatments were defined for the fourth group, categorised as ‘injured’ or ‘not injured’ depending on whether prey crayfish were visibly injured or not, respectively. We observed a significant decline in the consumption of water lice in the G and G + Cr treatments compared to the C and Cr treatments (up to 47% on average). There were no significant differences in consumption between the G and G + Cr treatments, or C and Cr treatments. No significant differences in food consumption parameters were detected between sub-treatments with ‘injured’ and ‘not injured’ conspecific crayfish. Knowledge of modifications in the feeding behaviour of marbled crayfish in the presence of round goby (and fish predators in general) is essential for ecologists attempting to understand the changes and impacts occurring in invaded freshwater ecosystems.


Keywords: None provided.