Tyler Hessler | USGS Science

USGS2025

Long-term surgery survival, body condition effects, and incision healing of Silver Carp and buffalo species comparing sedation methods across seasons

Objective Internal tagging for telemetry studies requires invasive surgery procedures, necessitating sufficient sedation to support animal welfare. Challenges with existing chemical sedatives have resulted in technological alternatives, including electrosedation, with these newer methods less extensively studied. Our primary objective was to understand long-term survival, body-condition effects, and incision healing after surgical implantation of an imitation telemetry transmitter under three different sedation techniques. Methods We collected Silver Carp Hypophthalmichthys molitrix and buffalo Ictiobus spp. from the Missouri River watershed in 2022 and 2023, during each of the four seasons. One of three sedation techniques was applied: electric fish handling gloves, tricaine methanesulfonate (MS-222), and eugenol. Additionally, we observed a group of fish that were unsedated but subjected to handling similar to that experienced during surgery. Fish were monitored to determine the effects of treatment, individual characteristics, surgery characteristics, and time-varying environmental factors on survival, body condition, and incision healing over 69- to 85-d holding periods. Results Long-term survival was higher for buffalo (86%) than Silver Carp (57%), with the fewest mortalities during the winter trial and most in summer, but sedation treatment did not affect survival. Smaller fish had a greater risk of mortality but better incision healing. Incision healing scores improved in warmer temperatures. Conclusions Difference in seasonal effects on survival and healing indicate a need to consider trade-offs when scheduling tagging for projects. However, a lack of difference in survival among treatments, including the group that was handled but did not undergo surgery, suggests no advantage of one sedative over another, but handling impacts may require more consideration.

Transactions of the American Fishery Society↗

USGS2025

Fish-assemblage evaluation in the lower Sandusky River, Ohio, following dam removal

The Sandusky River, Ohio, USA, has experienced more than a century of alterations, including dam implementation and removal, causing a cascade of habitat changes. The physical changes in the river led to establishment of several invasive species. Ten hoop-net sampling sites, spaced about 500 m apart were established in the river to monitor fish assemblage and their habitat preferences. Four 10-d sampling events were completed from April through October 2021. Ordination analyses were used to assess fish-assemblage structure seasonably, species-habitat relationships, and life-history strategies of 31 species. Generalized linear mixed-effects models were used to assess temporal factors that may drive diversity and community assemblage. Models indicated increased species richness after removal of the dam. Presence and proportion of catch data were compared to Ohio Environmental Protection Agency 2009 pre-dam-removal data to further assess changes in fish assemblage. Several species, especially catostomids, have begun to use the habitat downstream of the former dam, altering fish assemblage throughout the river. We expect shifts in assemblage structure to persist, making continued monitoring essential for understanding how non-native and recreationally important species continue to respond to dam removal.

Ohio↗