The inclusion of vertically-suspended environmental enrichment in circular tanks has produced substantial benefits during fish rearing. This study examined the tank water velocity profiles of four different vertically-suspended structures (rod array, extended rod array, single angle array, double angle array) and a control (no environmental enrichment) at two incoming water velocities (18.3 cm/s and 54.9 cm/s) in 1.8-m diameter circular tanks. At both of the incoming water velocities, overall water velocities throughout the tank were significantly reduced with the addition of any environmental enrichment in comparison to the control. In addition, the overall water velocities in the double angle array were significantly lower than the other three enrichment treatments.

The effects of premating light regimes on sexual reproduction and the production of spherical cells in Chloromonas sp.-D, a unicellular green snow alga, were studied using cross-mating strains 582C and 582D isolated from snowpacks associated with mixed hardwood-softwood forests in Whetstone Gulf State Park, Tughill Plateau, NY. Two preacclimation regimes were used, Vita-Lite as controls (530-700 nm peak) and blue light as experimentals (430-460 nm peak) prior to the mating experiments. In blue light, an increase in the number of matings and spherical cells (spheres) produced in the life cycle was observed as the photoperiod increased. This implies that longer photoperiods of blue light are more optimal for sexual reproduction in Chloromonas sp.-D than shorter ones. Under Vita-Lite, there was a significant increase in the number of matings and spheres with the extended 20 : 4 photoperiod compared with the shorter 14 : 10 photoperiod. Under blue light, significantly more matings and spheres occurred than under Vita-Lite using the same irradiance level of 95 µmol photons m 2 s 1 (photosynthetically active radiation [PAR] of 400-700 nm) for the 14 : 10 and 20 : 4 photoperiods. The results of these experiments suggest that Chloromonas sp.-D, known only from the Tughill Plateau, NY, is not reproducing optimally at this site where it grows and reproduces under an approximate 14 : 10 photoperiod in early April. However, in the upper 10 cm of snow in the Tughill Plateau, a blue light irradiance level of 95 µmol photons m 2 s 1 occurs, which is optimal for this species. When these conditions are combined with a 14 : 10 photoperiod, the Tughill Plateau appears to be sub-optimal for mating and production of spherical cells. Since Chloromonas sp.-D does not appear to have a dependence on a dark cycle, this would allow it to expand its geographical distribution. It may reproduce more optimally under blue light (95 µmol photons m 2 s 1 ) with an extended photoperiod (>20 : 4 h, light:dark) in high latitude field sites such as Lake Bienville, Québec, in eastern North America where other species of Chloromonas are known in snow associated with coniferous forests. Copyright

Vertically-suspended environmental enrichment has been shown to produce improvements in fish growth during hatchery rearing in circular tanks. This study documented the effects of a novel suspended structure on the velocity profile of a 3.63-m diameter circular tank containing juvenile landlocked fall Chinook salmon (Oncorhynchus tshawytscha) at two different densities (9.0 and 34.3 kg/m 3). The addition of vertically-suspended structure to the tank significantly decreased velocities at nearly every sampling point, with velocities typically dropping from 15 cm/s without structure to less than 6 cm/s when structure was present. Fish density also significantly impacted in-tank velocities, with an inverse relationship observed between the density of fish and water velocity. Significant interactions were present among the presence or absence of structure and fish density. When structure and fish were absent, the velocity at the edge of the tank was 15.63 cm/s, which was significantly higher than the 4.75 cm/s velocity when both structure and the lower fish density were added, which was in turn significantly higher than the 2.29 cm/s velocity observed with structure and higher fish density. Despite the potentially unique features of this study, vertically-suspended environmental enrichment and the presence of fish clearly alter circular tank water velocities, which may at least partially explain the improvements in fish rearing performance observed with the use of suspended structure.

Hatchery incubation of salmonid eggs typically requires the use of chemical fungicides that possess potential negative effects on human health or the environment. Strobiles from the hops Humulus lupulus plant have exhibited antimicrobial properties in nonaquaculture situations. This study investigated the use of hops as an alternative zoosporic fungal treatment with three experiments. In the first experiment, dried strobiles from wild variety hops were ground and placed at two concentrations in petri dishes containing sesame seeds and hatchery water containing Saprolegnia diclina. There was a positive relationship between the concentrations of hops and the amount of time elapsed before the observance of zoosporic fungal infestation. In subsequent experiments, the antimycotic activity of two concentrations of commercially available Summit variety hop pellets were evaluated using dead Chinook salmon Oncorhynchus tshawytscha eggs in vertical-flow incubation trays. In the second experiment, which involved static treatments of either 24 or 48 g of hop pellets wrapped in cheesecloth, zoosporic fungi appeared on the eggs in all the treatments at the same time and developed at the same rate. In the third experiment, the cheesecloth was eliminated and hop pellets were placed directly in the incubation trays at amounts of either 224 g for the entire duration of the experiment, or 112 g initially with 88 g of hops added after 3 d. Zoosporic fungi did not appear on the dead eggs in any of the hops treatment trays until 72 h after water mold was observed on the controls. Hops also delayed complete egg infestation by 72 h. Results from these experiments indicate for the first time the potential use of both wild and commercially available hops to control zoosporic fungi on incubating salmonid eggs.

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