Abstract.-Seasonal differences in glochidial maturity, substrate, and diet were studied to determine how these factors affect the survival and growth of juvenile freshwater mussels. Comparisons were made between juveniles produced in the fall and spring of the year; cultured in sediment, sand, or without substrate; and fed either of two species of small (5-10-m) green algae. The survival and growth of endangered juveniles of oyster mussel Epioblasma capsaeformis were compared with those of a common, seemingly more robust species, the rainbow mussel Villosa iris. The growth of rainbow mussel juveniles was significantly greater than that of oyster mussel juveniles (P Ͻ 0.001). The survival and growth of oyster mussel juveniles were significantly greater when propagated in the spring, that is, when glochidia were mature and would normally be released, than in fall (P Ͻ 0.001). Survival and growth of juveniles of both species were significantly greater when they were cultured in a sediment substratum rather than sand or no substratum (P Ͻ 0.001). No differences (P Ͼ 0.05) were observed in survival and growth of juveniles fed algal species Neochloris oleoabundans or Nannochloropsis oculata. In the spring of the year, juvenile oyster mussels achieved a survival of 29.6% and mean length of 664 m at 60 d of age, whereas at the same age rainbow mussel juveniles exhibited a survival of 25.1% and a mean length of 1,447 m.

Who Should Attend Biologists interested in freshwater mussel biology and freshwater mussel culture techniques. Course Length 4.5 days College Credit 2 semester hours Tuition Tuition for FWS, NPS, and BLM is prepaid. Tuition is $1,195.00 for participants from other agencies and organizations. To Register DOI employees: Log In to DOI Learn, enter the course title in the search box, click scheduled classes, click submit request. Non-DOI employees: If you do not have a DOI Learn account, please contact Matthew Patterson for instructions on how to create an account.

Abstract-Chlorine (Cl) is a highly toxic, widely used halogen disinfectant that is present in point-source pollution discharges from wastewater treatment plants and industrial facilities. The U.S. Environmental Protection Agency freshwater criteria for Cl are 19 g total residual Cl (TRC)/L as a maximum 1-h average concentration and 11 g TRC/L as a maximum 4-d average; however, toxicological data for unionids were not used in these calculations. To address this void in the data, we conducted acute tests with glochidia from several species and 21-d bioassays with three-month-old Epioblasma capsaeformis and three-, six-, and 12-monthold Villosa iris juveniles. The 24-h lethal concentration 50 values for glochidia were between 70 and 220 g TRC/L, which are 2.5 to 37 times higher than those reported in other studies for cladocerans. Significant declines in growth and survivorship were observed in the 21-d test with E. capsaeformis at 20 g TRC/L. Lowest-observed-adverse-effects concentrations in bioassays with juvenile V. iris were higher (30-60 g TRC/L) but showed a significant trend of declining toxicity with increased age. Although endpoints were above water quality criteria, the long life spans of unionids and potential implications of chronic exposure to endangered juvenile mussels still warrant concern.

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