During November 2002, 51 shovelnose sturgeon Scaphirhynchus platorynchus were sexed by ultrasound imaging using a portable ultrasonograph. We identified males with 96% accuracy (N = 25) and females with 80% accuracy (N = 25); one hermaphroditic individual was misidentified as a male. Overall, ultrasound imaging was 86% accurate. Sex in postspawned females was difficult to determine, 60% being misidentified as males (N = 5). Ultrasonography is an effective noninvasive method for sex determination that can be applied to other species of Acipenseriformes. Modern portable equipment expands its utility to field studies.

Aquaculture, especially fish farming, plays a vital role in ensuring food security in the United States and worldwide. However, for fish farming to be sustainable and economically viable, drastic improvements to the current labor-intensive and resource-inefficient operations are required. The hybrid aerial/underwater robotic system (HAUCS) aims to bring fundamental innovations to how pond-based farms operate. HAUCS is an end-to-end framework that consists of three principal subsystems: 1) a team of collaborative aero-amphibious robotic sensing platforms integrated with water quality sensors; 2) a land-based home station that can provide automated charging and sensor cleaning; and 3) a backend processing center that includes a machine-learning-based water quality prediction model and farm control center. HAUCS will be capable of collaborative monitoring and decision-making on farms of varying scales. The HAUCS platform, payload, and prediction model are discussed. The initial deployment of the HAUCS framework at a land-based aquaculture fish farm is presented.

Ichthyophthiriasis, or ich, is a disease of freshwater fish that is difficult to treat chemotherapeutically because the causative agent, Ichthyophthirius multifiliis, is protected by the host's epithelium during much of its life cycle. In our experiments, a modified standard formalin treatment (25 mg/L for 4 h, 4 d/week) conferred partial protection but failed to prevent 40–70% mortality among channel catfish Ictalurus punctatus. A water velocity of 20.3 cm/min in 5-m-long raceways and a turnover rate of 2.5/h reduced mortality of ich-infected channel catfish fingerlings to less than 10%. A water velocity of 36.5 cm/min and a turnover rate of 4.5/h held mortalities to 7% and eliminated ich from the raceways. When turnover rate fell below 1.9/h (water velocity < 75 cm/min) in 24.4-m-long raceways, ich outbreaks occurred, but higher water velocities reversed the epizootics. Prophylactic increases in water flow (> 85 cm/min, turnover rate > 2.1/h) resulted in no losses caused by ich during 2 years a...

Little is known about the habitat preferences and needs of pallid sturgeon Scaphirhynchus albus, which was federally listed as endangered in 1990. To learn more about habitat use and selection by pallid sturgeon, sonic transmitters were surgically implanted in 27 individuals from the middle Mississippi River. Study fish were located 184 times (1–23 times/individual) from November 1995 to December 1999. Of the seven macrohabitats identified, pallid sturgeon were found most often in main‐channel habitats (39% of all relocations) and main‐channel border habitats (26%); the between‐wing‐dam habitats were used less often (14%). Strauss's linear selectivity index (L_i) values indicated that study fish exhibited positive selection for the main‐channel border, downstream island tips, between‐wing‐dam, and wing‐dam‐tip habitats; they showed negative selection for main‐channel, downstream of wing dams, and upstream of wing dam habitats. Comparison of L_i values for four temperature ranges and three daily mean discharge ranges revealed little change in habitat selection due to temperature or discharge. Habitat use patterns also were similar across seasons and discharge regimes, except during spring months when between‐wing‐dam habitats saw greater use and main‐channel and main‐channel border habitat use declined. These changes may have been a response to high river stages associated with spring flooding, which may create favorable feeding areas in the between‐wing‐dam habitats. Enhancement and restoration of habitat diversity, particularly downstream island tip and between‐wing‐dam habitats, may be necessary for the recovery of pallid sturgeon in the middle Mississippi River.