Fish reproductions were studied in two river basins (Corumbataí and Jacaré-Pepira basins) in the State of São Paulo, southeastern Brazil. In the Corumbataí basin, four sites were sampled: Cabeça River, Lapa Stream, Passa-Cinco River, and Corumbataí River; in the Jacaré-Pepira basin, three sites were sampled: Tamanduá Stream, Jacaré-Pepira River, and Agua Branca Stream. A total of 12 bimonthly s...

Alternative transmission strategies are common in many parasitic organisms, often representing discrete phenotypes adopted in response to external cues. The facultative truncation of the normal 3-host life-cycle to a 2-host cycle in many trematodes provides an example: some individuals mature precociously, via progenesis, in their intermediate host and produce eggs without the need to reach a d...

The study object was an Odontesthes bonariensis (Valenciennes, 1835) population of a characteristically shallow lake from the pampasic region. Over one year, zooplankton and fish samples were collected monthly. As a function of time and gender, several indices were investigated (relative weight, mesentery fat index, gonadosomatic index, hepatosomatic index and somatic index) and were related to...

Abstract Kawakawa (Euthynnus affinis) is one of the economically valuable species for Mallaca strait fishermen. This study aims to determine level gonad maturity, size fish’s first ripe gonad, and maturity index (E. caught at Tanjung Beringin’s Auction Place, Serdang Bedagai Regency, North Sumatra. Three months sampling were conducted, from July September 2021. The maturation gonads was observe...

Objective- Acipenser persicus is one of the most important caviar producing fishes in the Caspian Sea and one of the endangered species of the sturgeon fishes. For breeding of sturgeons, large numbers of animals have to be captured and examined to obtain sufficient numbers of mature fishes that will spawn within a few months in captivity. Design- Original study Animals- A total of 66 adult Acip...

Climate change research is advancing to more complex and more comprehensive studies that include long-term experiments, multiple life-history stages, multi-population, and multi-trait approaches. We used a population of the barnacle Balanus improvisus known to be sensitive to short-term acidification to determine its potential for long-term acclimation to acidification. We reared laboratory-bre...

Knowledge of both sex and maturity stage without killing fish is important from many aspects. The establishment of accurate sex and maturity determination without external sexual dimorphism or when external characters are not developed has usually involved the use of either hormone radioimmunoassay or biopsy techniques. These methods are time and labor consuming as well as harmful to fish. Ther...