No abstract

A tube sampler and a Wisconsin plankton SLT **? I" * °' UaCrC hatCheiy ">»* for compS «on of zooplankton sampling efficiencies. Zooplankton samples taken with the tube sampler and a Wisconsui Plankton net showed the tube sampler to 4 moc ient u, captunng zooplankton. The tube sampler made t convenient to mcrease the number of sampling s£ tions, which should provide more accurate qualitative and quantitative data on pond zooplankton.

Survival of the fountain darter (Etheostoma fonticola), a U.S. federally listed endangered species, may depend on captive propagation. Studies were conducted to determine the effect of temperature on spawning and to develop methods for culture. The fountain darter spawned and produced viable offspring in aquaria at 27, 24, 21, 18, 15, 12, 9, and 6°C. The fish also spawned at 3 and 30°C but did not produce viable eggs. Daily egg production of individual fish held at 27, 21, 15, and 9°C was variable. The mean critical thermal maximum for the fountain darter was 34.8°C. Early life stages, 4-14 mm long, were offered a variety of live protozoans, rotifers, and microcrustaceans. Food selection varied with fish size and food size. Fountain darters reached sexual maturity in about 180 d when maintained at 21°C. Three-year-old darters produced viable offspring, and several lived longer than 4 years. Tricaine methanesulfonate was an effective anesthetic at 60 mg/L but was fatal to subadults at 100 mg/L.

Alligator Gar Atractosteus spatula numbers have declined throughout much of the species’ historic range due to anthropogenic effects (habitat alteration or loss, commercial fishing, and recreational fishing). As a result, many conservation agencies now rely on hatchery production of Alligator Gars to aid in recovery and reintroduction efforts. Because of difficulty in harvesting juvenile Alligator Gars from hatchery ponds, we evaluated the use of recreational‐grade swimming pools (4.6 m in diameter × 1.2 m deep) for spawning Alligator Gars, as this may result in increased production and more efficient harvest of juveniles. In May 2018, two recreational‐grade swimming pools were used to successfully spawn Alligator Gars, producing a total of approximately 159,000 fingerlings. Recreational‐grade swimming pools provided an efficient, low‐cost environment for the spawning of Alligator Gars. Alligator Gar fingerlings can be harvested from these pools with near 100% efficiency. Furthermore, this method reduced the need to use multiple males per female during spawning because they are confined to a small spawning environment. The use of recreational‐grade swimming pools for the culture of Alligator Gars resulted in refinement and increased efficiency in spawning this species, thereby offering a technique that should enhance Alligator Gar restoration efforts by increasing hatchery production capabilities.

A method for harvesting live zooplankton with a modified propellor-lift pump was tested in nine 0.1-acre unfertilized hatchery ponds. As judged by liveweight estimates of zooplankton harvested, collecting zooplankton at night with a light suspended over the pump intake was more effective than collecting them at night without the light or during the day. This method should be convenient and economical for collecting large quantities of live zooplankton from hatchery ponds.