Interpopulation variation in growth and life-history traits of the introduced sunfish, pumpkinseed Lepomis gibbosus, in southern England By F. Villeneuve 1 , G. H. Copp 2 , M. G. Fox 3 and S. Stak _ enas 2 1 Watershed Ecosystems Graduate Program, Trent University, Peterborough, ON, Canada; 2 CEFAS, Salmon & Freshwater Team, Lowestoft, UK; 3 Environmental and Resource Studies Program and Department of Biology, Trent University, Peterborough, ON, Canada Summary We examined attributes of growth and reproduction in 19 populations of pumpkinseed (Lepomis gibbosus) introduced into southern England in order to: (i) assess variability of these traits in a northern European climate; (ii) assess inter- relationships among these variables; and (iii) compare these attributes with populations from other parts of Europe where pumpkinseeds have been introduced. Growth rates varied considerably among populations, but juvenile growth rates and adult body sizes were generally among the lowest in Europe. Mean age at maturity ranged from 2.0 to 3.9, and was strongly predicted by the juvenile growth rate (earlier maturity with faster juvenile growth). Other population parameters that also displayed significant negative associations with mean age at maturity were gonadosomatic index, body condition, and adult body size (total length, TL at age 5). Mean TL at maturity and the adult growth increment showed no significant associations with any of the other growth or life-history variables. Pumpkinseed populations in England matured significantly later than those introduced into warmer, more southerly areas of the continental Europe. All of these data suggest that a combination of cool summer temperatures and resource limitation is the cause of slow growth, small adult body size and delayed maturity relative to introduced popu- lations on the European mainland. Introduction Adaptations in life-history traits and biogeographical pat- terns of growth and establishment are central themes in the application of invasion and colonization theory to the introduction of fish species to freshwater ecosystems outside their native range (e.g. Fausch et al., 2001). The pumpkin- seed sunfish Lepomis gibbosus (L.) is a good example. The speciesÕ native distribution in North America since the Miocene was restricted to eastern North America, but it has since been introduced to many parts of Europe as well as translocated to non-native parts of North America (Scott and Crossman, 1973; Fuller et al., 1999). Introductions of the pumpkinseed to European waters began in the late 19th century (Ku¨nstler, 1908), including a few small water bodies in southern England during the 1890s or early 1900s (Wheeler and Maitland, 1973; Lever, 1977). In Europe, most previous studies of pumpkinseed originate from the mainland (reviewed in Copp et al., 2004), with only a few published studies on northern European populations (Copp et al., 2002; Klaar et al., 2004). Prior to the 1994 assessment of a single English pumpkin- seed population in Cottesmore School Pond, River Mole catchment, West Sussex (Copp et al., 2002), the distribution of pumpkinseed in southern England was thought to be relatively restricted (Maitland, 1972; Lever, 1977). However, during the 1980s, pumpkinseed were accidentally introduced to new water bodies as contaminants of intentional fish transfers (of native species plus common carp Cyprinus carpio). During sorting of the fish, small pumpkinseed were observed under the opercula of some large cyprinids, and this is the suspected means by which pumpkinseed distribution in south-east England expan- ded (R. Horsfield, pers. comm.). As with Cottesmore School Pond (Copp et al., 2002), some of these still waters are continuously or intermittently connected to streams; in particular those in the upper reaches of the River Ouse of East and West Sussex (Klaar et al., 2004). The limited distribution of established populations (EA, 2002) makes them interesting from a dispersal and life-history perspective, in comparison with areas on the European mainland where it is already widely distributed, e.g. in southern France (Keith and Allardi, 2001) and the Iberian peninsula (Elvira and Almod- ovar, 2001). Although the current pumpkinseed distribution in England is relatively limited, many introduced species have been known to experience a lag phase prior to wider and more rapid (i.e. invasive) dispersal (Crooks and Soule, 1999; Mack et al., 2000). The possible spread of pumpkinseeds beyond their current English distribution (e.g. from the River Mole down into the River Thames and beyond) is a concern in the UK, where environmental managers are attempting to identify strategies to minimize the dispersal and impact of this species on native fishes. The recent report of pumpkinseed in the upper reaches of the Thames in Gloucester (G. Gerring, Environment Agency; pers. comm.) emphasizes this concern. Because particular life-history traits have been associated with the ability of exotic species to colonize and spread, the focus of the present study was on the life-history traits of non- native pumpkinseed populations in England. Our specific objectives were to: (i) assess the variability of growth and life- history traits of English populations; (ii) evaluate inter- relationships among these variables; and (iii) compare these attributes with populations from other parts of Europe where pumpkinseeds have been introduced. From life-history theory (e.g. Gadgil and Bossert, 1970) and from empirical relation- ships established in previous studies of pumpkinseed (Deacon and Keast, 1987; Fox, 1994; Fox and Crivelli, 2001), we hypothesized that age at maturity and reproductive allocation would be influenced by pre-maturational growth rates, and J. Appl. Ichthyol. 21 (2005), 275–281 Ó 2005 Blackwell Verlag, Berlin ISSN 0175–8659 Received: March 15, 2005 Accepted: June 25, 2005 U.S. Copyright Clearance Centre Code Statement: 0175–8659/2005/2104–0275$15.00/0 www.blackwell-synergy.com