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Fish Ladder (fish + ladder)

Distribution by Scientific Domains

Life Sciences	66%

Selected Abstracts

Influence of seasonal, diel, lunar, and other environmental factors on upstream fish passage in the Igarapava Fish Ladder, Brazil

ECOLOGY OF FRESHWATER FISH, Issue 3 2009
P. M. Bizzotto
Abstract,,, Upstream fish passage was evaluated during 12 months in the vertical-slot Igarapava Fish Ladder constructed around Igarapava Dam, in the heavily dammed Grande River, Southeast Brazil. A video monitoring system was used to observe 61,621 fish that passed the ladder, of which 93.5% were identified to 15 taxa. Among the migratory species, the most abundant were Pimelodus maculatus (33.6% of all fish), Leporinus octofasciatus (31.4%), Leporinus friderici (4.5%), and Prochilodus lineatus (3.1%). Seven taxa were classified as nonmigratory, and of these taxa, the small Bryconamericus stramineus was the most abundant (12.7%) of all fishes. Passage of the ,nonmigratory' taxa upstream in the ladder shows they are migratory in this system and have a strong behavioural drive to move to upstream habitat. Passage of most taxa had a strong seasonal pattern. While some species passed primarily during the day, others showed a distinct nocturnal pattern. Lunar phase and water temperature also strongly affected passage of some taxa. Rainfall and dam discharge had a small or null influence on most taxa; perhaps due to the fairly small catchment area of the reservoir and the highly regulated discharge at Igarapava Dam. [source]

Effect of river fragmentation and flow regulation on occurrence of landlocked brown trout in a fish ladder

JOURNAL OF APPLIED ICHTHYOLOGY, Issue 1 2009
O. Slavík
Summary The movement pattern of brown trout Salmo trutta (L.) in a fish ladder on the heavily fragmented Oh,e River, Czech Republic was observed for 16 months. Some individually-tagged fish repeatedly occurred in the ladder. A total of 1640 fish represented captures of 595 S. trutta in the fish ladder; 247 fish were caught once and 348 individuals were caught repeatedly. Repeatedly-caught (348) individuals represented 1393 (84.9%) of the 1640 captures. The likelihood of repetitive occurrence decreased with the increase in fish body length. The number of individuals in the ladder was inversely related to temperature, and positively correlated with increasing water flow in the main channel. Fish abundance in the ladder was density-dependent, as the number of individuals was inversely related to fish size and time of residency in the ladder. Spawning migrations were not the best predictor of maximum fish occurrence in the ladder, suggesting that repetitive capture of individuals in the ladder was significantly affected by other factors influencing fish behaviour. Repetitive fish occurrence in ladders can be expected, particularly in rivers with numerous lateral obstructions. [source]

Effects of Habitat Fragmentation by Damming on the Persistence of Stream-Dwelling Charr Populations

CONSERVATION BIOLOGY, Issue 5 2002
Kentaro Morita
We assessed the effect of habitat fragmentation by damming on the population persistence of a stream-dwelling fish, the white-spotted charr (Salvelinus leucomaenis), in streams of southwestern Hokkaido, Japan. We sampled for charr at 52 dammed-off sites by electrofishing or snorkeling and measured five habitat characteristics: isolation period, watershed area, gradient, elevation, distance from sea. Of the 52 study sites above dams, white-spotted charr were absent at 17 sites and were present at 35 sites. Because the charr occupied all undammed upstream reaches, the damming would cause the absence of charr upstream. Among five habitat characteristics examined, stepwise logistic-regression analysis showed that disappearance was promoted with increasing isolation period, with decreasing watershed area (i.e., habitat size), and with decreasing gradient. The resulting logistic model explained 82.7% of the present white-spotted charr occurrence and forecasted that 12 of 35 extant populations will disappear after 50 years. Our findings imply that extirpation of small, dammed-off populations is inevitable unless efficient fish ladders are installed or dams are removed. Resumen: La construcción de presas tiene serias consecuencias sobre los ecosistemas acuáticos y uno de los mas serios es el "efecto de barrera" ( la prevención de que un organismo migre a través del sistema). Evaluamos los efectos de la fragmentación del hábitat ocasionados por la construcción de presas en la persistencia de un pez morador de arroyos, la trucha de montaña de manchas blancas ( Salvelinus leucomaenis), en arroyos del suroeste de Hokkaido, Japón. Muestreamos en 52 sitios con represas empleando electropesca o buceo con esnórquel y medimos cinco características del hábitat ( periodo de aislamiento, área de la cuenca, gradiente, elevación y distancia al mar). De los 52 sitios de estudio ubicados arriba de las represas las truchas de montaña estuvieron ausentes en 17 sitios y presentes en 35 sitios. Debido a que las truchas de montaña ocupaban todos los rangos sin represas arroyo arriba, la creación de represas pudo causar la ausencia de truchas de montaña arroyo arriba. Dentro de las cinco características del hábitat examinadas, el análisis de regresión logística mostró que la desaparición era promovida por un incremento en el periodo de aislamiento, con una disminución en el área de la cuenca (i.e. tamaño del hábitat) y con una disminución del gradiente. El modelo logístico resultante explicó 82.7% de la presencia de truchas de montaña y pronosticó que 12 de la 35 poblaciones actuales desaparecerían después de 50 años. Nuestros resultados implican que la extirpación es pequeña y que la exclusión por construcción de represas es inevitable a menos que se instalen desvíos para peces o que se remuevan las presas. [source]

Threatened obligatory riverine fishes in human-modified Polish rivers

ECOLOGY OF FRESHWATER FISH, Issue 1-2 2000
T. Penczak
Abstract , The fate of obligatory riverine fish species (rheophils), which are the objects of anglers' exploitation (chub ,Leuciscus cephalus, nase ,Chondrostoma nasus, barbel ,Barbus barbus, gudgeon ,Gobio gobio), and brown trout (Salmo trutta m. fario) and grayling (Thymallus thymallus) (in the Gwda River basin only), were investigated in large alluvial rivers (Pilica and Warta) and in the medium-sized Gwda River basin. The Pilica (1973) and the Warta (1986,1987) were divided by large dams without fish ladders in their middle courses. The Gwda River was divided by only a few dams along its course, but its tributaries carrying pure water had numerous small dams that supplied water for fish farms. Other stresses influencing fish populations in these rivers were: pollution, overfishing, hydroelectric plants and bank revetments. Because the listed stresses occurred alternately and at various periods of time in these rivers, this enabled attributing the cause for extinction and reduction of the abundance and distribution. In the salmon Gwda River basin, a drastic decrease in spatial distribution and reduction of occurrence ranges of brown trout, grayling and barbel was evident in respect to the first study period (1980s) in the 1990s. In the large, alluvial Pilica River, nase, barbel and dace are on the edge of extinction and chub and gudgeon are vulnerable. In the Warta's tailwater, barbel is an extinct species, and chub, dace and gudgeon are vulnerable ones. In a site in the backwater, none of the above mentioned species became extinct, but their abundance and occurrence frequency decreased a bit in respect to the pre-impoundment period. Roach-generalist, which was used in this research as a "control" species, increased in abundance in all 3 rivers. These investigations univocally proved that the dams cause catastrophic stress for obligatory riverine species., [source]