RESEARCH ARTICLE Spring mating period in Orconectes limosus: the reason for movement Milos ˇ Bur ˇic ˇ Æ Antonı ´n Kouba Æ Pavel Koza ´k Received: 9 March 2009 / Accepted: 18 May 2009 / Published online: 9 July 2009 Ó Birkha ¨user Verlag, Basel/Switzerland 2009 Abstract Thirteen adult Orconectes limosus males (car- apace length 32.5 ± 2.48 mm; weight 10.8 ± 2.63 g) were radio-tagged and tracked during and after the spring mating period, April–June 2008. Average distances moved per day were higher in the mating period (14.9 ± 21.4 m) due to mate searching activity. During the mating period, movement did not correlate with water temperature, and crayfish were active during daylight hours. They moved rapidly upstream and downstream, a maximum 118 and 95 m per day, respectively. When water temperature increased over 10°C, this initiated the end of mating and the start of spawning, and the spring migration abruptly ceased. An influence of water temperature on movements was observed during the non-reproductive period. Orco- nectes limosus was highly mobile in small watercourses, signifying a threat of penetration into native crayfish hab- itats, and potentially enabling the transmission of crayfish plague. This threat was increased during the mating period due to increased activity. Keywords Invasive species Á Radio-telemetry Á Reproduction Á Migration Á Crayfish Introduction Orconectes limosus (Rafinesque 1817), a temperate-water crayfish native to the north-eastern USA and south-eastern Canada, is now widespread in at least 20 European countries (Po ¨ckl et al. 2006). It is present mainly in large rivers and their tributaries of sixth or higher stream order. It can be found also in streams of a lower stream order that join larger rivers (Petrusek et al. 2006). Small brooks and rivulets are apparently not suitable habitats for O. limosus in Europe (Holdich et al. 2006), but such habitats are used by O. limosus in Canada (McAlpine et al. 1991). However, they may enter small watercourses temporarily in European habitats (Petrusek et al. 2006;Burˇic ˇ et al. 2009). Orconectes limosus is a small species, with an adult total length (TL) of 5–8 cm (Holdich et al. 2006; Holdich and Black 2007). The small size complicates locating and re-sampling individuals in the field (Burˇic ˇ et al. 2008). Radio-telemetry allows the study of movement and behaviour patterns of even very small aquatic animals over extended time periods and has been utilized successfully for crayfish (e.g. Robinson et al. 2000; Gherardi et al. 2000; Bubb et al. 2004), including a study of O. limosus (Burˇic ˇ et al. 2009). There are two mating periods for O. limosus, autumn and spring (Hamr 2002; Holdich and Black 2007; Koza ´k et al. 2007). Detailed data on the migratory activity linked to reproductive activities of O. limosus are lacking. It is possible that they exhibit increased movements similar to those seen in Procambarus clarkii (Girard 1852) that we related to its reproductive phase (Gherardi and Barbaresi 2000). This possibility is reinforced by Stucki (2002), who reported wandering O. limosus in early spring and recorded their daily activity. To gain information on migrations associated with reproductive activity, crayfish behaviour and movements during and after the spring mating period were observed and recorded. The present work addresses the following main questions: Does the reproductive period influence activity, behaviour and movements of crayfish? Does water M.Burˇic ˇ(&) Á A. Kouba Á P. Koza ´k Research Institute of Fish Culture and Hydrobiology, University of South Bohemia in C ˇ eske ´ Bude ˇjovice, Za ´tis ˇi 728/II, 389 25 Vodn ˇany, Czech Republic e-mail: buric@vurh.jcu.cz Aquat. Sci. (2009) 71:473–477 DOI 10.1007/s00027-009-0102-6 Aquatic Sciences