Lodge. 1993. Species replacements among Orconectes crayfishes in Wisconsin lakes: the role of predation by fish. Can. 1. Fish. Aquat. Sci. 50: 1484-1488 To test the role of size-and species-selective predation by fishes in species replacements among congeneric crayfishes in northern Wisconsin lakes, we tethered the same three sizes of each of three species of Orconectes at six sites in the littoral none of Trout Lake, Vilas County, Wisc. Small crayfish (1 5-18 rr-prm carapace length) were removed by fish at significantly higher rates than medium (23-25 mm) and large (33-35 mm) crayfish.Orconectes virilis was removed at significantly higher rates than 0. propinquus and 0. rusticus. These speciesselection results suggest that predation by native fishes contributes to the previously documented replacement of the native crayfish 0. viriIis by the exotic crayfishes 0. propinquus and 0 . rusticeis. In combination with the observations of others that adult sine of 0. rusticus is typically larger than that of 0. propinquus in northern Wisconsin lakes, our size-selection results suggest that fish predation may also hasten the ongoing replacement of 0. propinquus by 63. rusticus. Thus, fish predation is probably an important mechanism driving the replacement of 8. virilis by 0. propinquus and the replacement of both congeners by 0. rusticus.Afin de tester Itinfluence de la predation, selon la taille et selon I1esp6ce, exercke par des poissons, sur la succession des esp6ces chez des kcrevisses appartenant au meme genre dans les lacs du nor$ du Wisconsin, nous avons fix6 des sarjets de trois grosseurs et de trois espPces dlOrconectes 2 six stati~ns dans la zone littorale du lac Trout, Vilas County, Wisc. Les petits ecrevisses (longueur de carapace 15-48 mm) ont 6t6 enleves par le poisssn a des taux significativement sup6rieurs 5 ceux des kcrevisses de taille moyenne (23-25 mmB et de grdnde taille (33-35 mm). Les sujets d'dlrconectes virilis ont 6tk enlevks j: des taux significativement superieurs ceux observes chez 0. propinquuc et 8. rusticus. Ces r6sultats, qui pointent vers une selection par espPce, indiquent que la prkdatisn exercke par des poissons indigbes cosltribue au rernplacement d6ja 6tudi6 de l'kcrevisse indigene 0. virilis par les ecrivisses exotiques 0. propinquus et 0. rusticus. En tenant cornpte de l'observation faite par d'autres chercheurs, h I'effet qu'a l'etat adulte, 0. rusticus est normalement plus gros que 0. propinquus dans les lacs de~ nord du Wisconsin, les r6sultats de nstre etude qui decrivent la s6lection par la taille indiquent que la predation exercke par le poisssn peut aussi accelerer le rernplacement en cours de 0. propinquus par 0. rusticus. Bref, Fa predation exercee par les poissons est probdbiernent un mecanisme important du remplacement dfO. virilis par 0. propinquus et de leur rernplacement par 0. rusticus.Received jirly 2 I , f 992 Accepted japruary 28, 5 993 (JB569 j ange changes are a natural phenomenon for most species, but humankind has dramatically increased the global rdte and ...

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Increasing utilization and human population density in the coastal zone is widely believed to place increasing stresses on the resident biota, but confirmation of this belief is somewhat lacking. While we have solid evidence that highly disturbed estuarine systems have dramatic changes in the resident biota (black and white if you will), we lack tools that distinguish the shades of grey. In part, this lack of ability to distinguish shades of grey stems from the analytical tools that have been applied to studies of estuarine systems, and perhaps more important, is the insensitivity of the biological end points that we have used to assess these impacts. In this study, we will present data on the phenotypic adjustments as measured by transcriptomic signatures of a resilient organism (oysters) to land-use practices in the surrounding watershed using advanced machine-learning algorithms. We will demonstrate that such an approach can reveal subtle and meaningful shifts in oyster gene expression in response to land use. Further, the data show that gill tissues are far more responsive and provide superior discrimination of land-use classes than hepatopancreas and that transcripts encoding proteins involved in energy production, protein synthesis and basic metabolism are more robust indicators of land use than classic biomarkers such as metallothioneins, GST and cytochrome P-450.

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Upland areas of southeastern U.S. tidal creek watersheds are popular locations for development, and they form part of the estuarine ecosystem characterized by high economic and ecological value. The primary objective of this work was to define the relationships between coastal development, with its concomitant land use changes and associated increases in nonpoint source pollution loading, and the ecological condition of tidal creek ecosystems including related consequences to human populations and coastal communities. Nineteen tidal creek systems, located along the southeastern United States coast from southern North Carolina to southern Georgia, were sampled during summer, 2005 and 2006. Within each system, creeks were divided into two primary segments based upon tidal zoning: intertidal (i.e., shallow, narrow headwater sections) and subtidal (i.e., deeper and wider sections) and then watersheds were delineated for each segment. Relationships between coastal development, concomitant land use changes, nonpoint source pollution loading, the ecological condition of tidal creek ecosystems, and the potential impacts to human populations and coastal communities were evaluated. In particular, relationships were identified between the amount of impervious cover (indicator of coastal development) and a range of exposure and response measures including increased chemical contamination of the sediments, increased pathogens in the water, increased nitrate/nitrite levels, increased salinity range, decreased biological productivity of the macrobenthos, alterations to the food web, increased flooding potential, and increased human risk of exposure to pathogens and harmful chemicals. The integrity of tidal creeks, particularly the headwaters or intertidally-dominated sections, were impaired by increases in nonpoint source pollution associated with sprawling urbanization (i.e., increases in impervious cover). This finding suggests these habitats are valuable early warning sentinels of ensuing ecological impacts and potential public health and flooding risk from sprawling coastal development. Results also validate the use of a conceptual model with impervious cover thresholds for tidal creek systems in the southeast region.