Pimelodus maculatus abundance in the tailrace of the Machadinho hydroelectric power plant during drought conditions.

Fish presence in tailraces is a remarkable management concern in operating hydroelectric power plants (HPP) in Brazilian rivers. Fish get blocked during upstream migration for spawning, and large shoals can last for days in the tailrace; however, the circumstances that attract fish throughout the year to this region are uncertain, especially during drought conditions. To unravel this uncertainty, we modeled the relationship between Pimelodus maculatus abundance and environmental and operational variables (N = 26) in monthly fishing campaigns at the Machadinho HPP (N = 18).

Changes in external osmolality and ionic composition affect Megaleporinus obtusidens sperm motility.

Understanding the effects of environmental factors on sperm motility characteristics can increase artificial reproduction efficiency in species that do not spawn naturally in captivity, such as Megaleporinus obtusidens. This study evaluated the effects of the osmolality (25, 85, 145, 205, 265, and 325 mOsm kg) and composition of activating solutions (NaCl, KCl, or fructose) on the percentage of motile sperm, and the swimming velocity and path straightness of M. obtusidens spermatozoa.

Gonadorelin increases semen production and does not affect its quality in Leporinus obtusidens.

Use of carp pituitary extract (CPE) as a hormone inducer for Leporinus obtusidens is cost-prohibitive; moreover, CPE contains unknown concentrations of gonadotropins. We evaluated the efficacy of gonadorelin as a substitute by analyzing its effect on sperm characteristics of L. obtusidens and cost-effectiveness (20, 40, 60, 80, and 100μgkg).

Winter is coming: Food web structure and seasonality in a subtropical freshwater coastal lake.

Food web studies provide a useful tool to assess the organization and complexity of natural communities. Nevertheless, the seasonal dynamics of food web properties, their environmental correlates, and potential association with community diversity and stability remain poorly studied. Here, we condensed an incomplete 6-year community dataset of a subtropical coastal lake to examine how monthly variation in diversity impacts food web structure over an idealized time series for an averaged year.