Common garden experiments were undertaken to test the hypothesis that the genetic capacity for growth of striped bass (Morone saxatilis) varies inversely with length of the growing season across a latitudinal gradient (i.e., countergradient variation (CnGV) in growth). Newly hatched larvae were obtained from six native anadromous stocks spanning most of the natural range of striped bass (Florida to Nova Scotia). Growth experiments were conducted under conditions of unlimited food at three temperatures (17, 21, 28°C) and commenced after larvae had exhausted maternal energy resources (i.e., yolk and oil) and had begun to metamorphose. Mixed-model nested ANOVA demonstrated that length and dry weight growth differed significantly among latitudes in most comparisons. South Carolina fish ranked consistently as the slowest growing group in virtually all comparisons, but the rank order of the other latitudes differed among trials. North Carolina and Gulf of Mexico fish generally had intermediate rates of growth whereas New York, Maryland, and Nova Scotia fish generally had the highest growth. Overall, the average growth rate of progeny from the 28 mothers tested in this study had a strong positive correlation with latitude of origin, strongly indicating CnGV in growth.

Pylodictis olivaris (flathead catfish) is a large, obligate carnivore native to drainages of the central United States that has been introduced widely beyond its native range. We report on the introduction of flathead catfish into the Delaware and Susquehanna River drainages, which represents the northernmost occurrences among Atlantic drainages. In the Delaware Basin, flathead catfish have been found in the Schuylkill River and the mainstem of the Delaware River. Recent sampling activities in the Schuylkill River suggest successful reproduction and establishment of a viable population there. In the Susquehanna basin, the fish has been found in the lower and central portion of the river mainstem. As in the Delaware Basin, recent sampling indicates that reproduction is occurring in the Susquehanna River. The introduction of this species has the potential to adversely affect ongoing anadromous fish restoration programs and native fish conservation efforts in the Delaware and Susquehanna basins. A cooperative effort will be required to mitigate the effects of this introduction.

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Eighty striped bass Morone saxatilis were obtained from Delaware Bay using commercial gill nets set adjacent to Woodland Beach (n = 70) and Bowers Beach (n = 10) in December 2003. Fish were examined for gross lesions. Total lengths (TLs) and eviscerated weights were determined to calculate condition factors (K). Portions of spleens were aseptically harvested for bacterial culture, and portions of spleens, kidneys (anterior and posterior), livers, and gonads were obtained for histological examination. The size distribution of the striped bass was relatively homogeneous; the mean TL was about 600 mm for all samples. Mean K exceeded 0.95 in all samples and was not significantly different (P > 0.05) among samples. Significant differences in mycobacterial infection prevalence (P < or = 0.05) were observed among samples; samples obtained at Woodland Beach (WB) on December 10 (53.8%, n = 13) and December 17 (7.1%, n = 42) exhibited the most striking differences in prevalence. Mycobacterial infection intensity ranged from 1 X 10(2) to 1 X 10(7) colony-forming units per gram of spleen. Acanthocephalan infection prevalence and intensity, non-acid-fast bacterial infection prevalence, and fish sex ratio were also significantly different among the samples (P< or = 0.05). Similar to the mycobacterial infections, differences in sex ratio, acanthocephalan infection, and non-acid-fast bacterial infection were observed between the WB samples taken on December 10 and 17. However, no significant associations (P > 0.05) were observed between sex ratio or these infections and mycobacterial infection. The differences in bacterial and parasite infection prevalence and intensity and fish sex ratio in some samples indicate that these fish had a different history and that the epizootiology of mycobacterial infection in striped bass from Delaware Bay may be relatively complex.