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Spawning Migration (spawning + migration)

Distribution by Scientific Domains

Earth and Environmental Science	66%
Life Sciences	33%

Selected Abstracts

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]

Effect of habitat fragmentation on spawning migration of brown trout (Salmo trutta L.)

ECOLOGY OF FRESHWATER FISH, Issue 3 2006
C. Gosset
Abstract , Human-induced habitat alteration is one of the main causes of the decline of freshwater fish populations. The watershed of the River Bidasoa (Spain) is an example of heavily fragmented habitat. The local brown trout (Salmo trutta L.) population is disturbed, with evidence of poor recruitment as well as low adult densities in the main stem. Forty male and female adult migratory trout were tagged with external or internal radio transmitters and released. Fixed stations with data loggers and mobile antennae were used with daily surveys to track fish movements during the migration and spawning period (3 months). Migration distances did not exceed 10 km, and half of the fish never entered a tributary in the study area. Fragmentation because of weirs on the main stem apparently prevented fish from reaching their spawning destination. Fish that entered the tributaries were first confronted with an accessibility problem because of low discharge. However, each fish chose one tributary, without making attempts to run up in other tributaries. Once in the tributary, fish were restrained in their upstream movements by dams. The study area appeared to be isolated from the vast upper part of the watershed. Within the study area, upper parts of tributaries also seemed strongly disconnected from the main stem. This study illustrates the negative impact of river fragmentation on S. trutta migration pattern. Population sustainability can be directly affected through the low availability of spawning grounds for migratory fish. Long-term effects of fragmentation may cause reproductive isolation within watersheds, which in the case of trout also means isolated phenotypic population units. [source]

Migration of landlocked brown trout in two Scandinavian streams as revealed from trap data

ECOLOGY OF FRESHWATER FISH, Issue 3 2004
J. Carlsson
Abstract,,, Anthropogenic barriers that may interfere or prevent fish migration are commonly found in streams throughout the distribution of salmonids. Construction of fish passages in streams is a common solution to this problem. However, the goal with fish passages is often, at least in Scandinavia, to allow Atlantic salmon (Salmo salar L.) and migratory brown trout (S. trutta L.) to get access to spawning areas above these barriers. Hence, the fish passages may often only be open during the spawning migration of salmonids (late summer to autumn). We present data, on wild brown trout migration, from two trapping systems in two Scandinavian streams showing that intra- and interstream migrations are common throughout the summer and autumn. Moreover, differences in size were found between trap-caught trout and electrofished trout where trapped trout were generally larger than electrofished trout. We suggest that the current regime with fish passages only open parts of the year can have negative effects on populations by depriving trout from the possibility to perform migrations throughout the year. Resumen 1. Barreras de origin antrópico que pueden interferer o prevenir las migraciones de los peces son frecuentes a lo largo de las áreas de distribución de los salmónidos. Una solución común a este problema es la construcción de pasos. Si embargo, el fin general de estos pasos es, por lo menos en Escandinavia, permitir el acceso a las áreas de reproducción por encima de las barreras tanto a salmones (Salmo salar L.) como a truchas migratorias (S. trutta L.). Frecuentemente, estos pasos están solamente abiertos durante el período de migración reproductiva (final del verano y otoño) porque se piensa que este régimen no tiene consecuencias negativas ya que estas especies muestran movimientos muy limitados en otros periodos del año. 2. Presentamos datos sobre migraciones de truchas colectados en dos sistemas de trampas de dos ríos escandinavos. Un río localizado por encima de una catarata inaccesible. El segundo, con una población migratoria de truchas. Los datos indicaron claramente migraciones intensivas a lo largo de todo el período en el que las trampas estuvieron operativas. Ambos ríos mostraron un pico de migración aguas arriba a mediados de Julio. Migraciones aguas abajo fueron raramente observadas en la población por encima de la catarata aunque migraciones aguas abajo en la población del río fueron intensivas al final del otoño. 3. Sugerimos que el régimen actual de pasos de peces que abren solamente partes del año puede tener efectos negativos sobre las poblaciones, al privar a las truchas de la posibilidad de migrar a lo largo del año. Esto puede extenderse a otros sistemas con barreras ya que observamos también migraciones intensivas en la población localizada por encima de la catarata. [source]

Time series analyses reveal transient relationships between abundance of larval anchovy and environmental variables in the coastal waters southwest of Taiwan

FISHERIES OCEANOGRAPHY, Issue 2 2009
CHIH-HAO HSIEH
Abstract We investigated environmental effects on larval anchovy fluctuations (based on CPUE from 1980 to 2000) in the waters off southwestern Taiwan using advanced time series analyses, including the state-space approach to remove seasonality, wavelet analysis to investigate transient relationships, and stationary bootstrap to test correlation between time series. For large-scale environmental effects, we used the Southern Oscillation Index (SOI) to represent the El Niño Southern Oscillation (ENSO); for local hydrographic conditions, we used sea surface temperature (SST), river runoff, and mixing conditions. Whereas the anchovy catch consisted of a northern species (Engraulis japonicus) and two southern species (Encrasicholina heteroloba and Encrasicholina punctifer), the magnitude of the anchovy catch appeared to be mainly determined by the strength of Eng. japonicus (Japanese anchovy). The main factor that caused the interannual variation of anchovy CPUE might change through time. The CPUE showed a negative correlation with combination of water temperature and river runoff before 1987 and a positive correlation with river runoff after 1988. Whereas a significant negative correlation between CPUE and ENSOs existed, this correlation was driven completely by the low-frequency ENSO events and explained only 10% of the variance. Several previous studies on this population emphasized that the fluctuations of larval anchovy abundance were determined by local SST. Our analyses indicated that such a correlation was transient and simply reflected ENSO signals. Recent advances in physical oceanography around Taiwan showed that the ENSOs reduced the strength of the Asian monsoon and thus weakened the China Coastal Current toward Taiwan. The decline of larval anchovy during ENSO may be due to reduced China Coastal Current, which is important in facilitating the spawning migration of the Japanese anchovy. [source]

Spatial distribution of the Japanese common squid, Todarodes pacificus, during its northward migration in the western North Pacific Ocean

FISHERIES OCEANOGRAPHY, Issue 2 2006
ATSUSHI KAWABATA
Abstract The spatial distribution of Todarodes pacificus in and near the Kuroshio/Oyashio Transition Zone during its northward migration was examined by comparative surveys using two types of mid-water trawl net and supplementary squid jigging from June to July 2000. The vertical and horizontal distribution patterns varied for different body sizes in relation to the oceanographic structure. Todarodes pacificus of 1,20 cm dorsal mantle length (ML) were widely distributed from the coastal waters of Japan to near 162°E longitude, probably due to transport by the Kuroshio Extension (KE). Todarodes pacificus smaller than 10 cm ML were mainly distributed in temperate surface layers at sea surface temperatures (SSTs) >15°C near the KE meander probably because of their poor tolerance to lower temperatures and limited swimming ability. Squid of 10,15 cm ML were distributed in the offshore waters of 10,15°C SST and in the coastal waters of northern Honshu, and underwent diel vertical migrations between the sea surface at night and deeper layers during the daytime. Squid larger than 15 cm ML were distributed in the coastal feeding grounds of northern Honshu and Hokkaido until they began their southward spawning migration. They also underwent diel vertical migrations, but remained deeper at night than the squid of 10,15 cm ML; this migration pattern closely matched that of their main prey such as euphausiids. We concluded that as T. pacificus grow, they shift their distribution range from the temperate surface layer around the KE toward the colder deeper layers, above 5°C, in the Oyashio and coastal areas. [source]

Oceanic migration and spawning of anguillid eels

JOURNAL OF FISH BIOLOGY, Issue 9 2009
K. Tsukamoto
Many aspects of the life histories of anguillid eels have been revealed in recent decades, but the spawning migrations of their silver eels in the open ocean still remains poorly understood. This paper overviews what is known about the migration and spawning of anguillid species in the ocean. The factors that determine exactly when anguillid eels will begin their migrations are not known, although environmental influences such as lunar cycle, rainfall and river discharge seem to affect their patterns of movement as they migrate towards the ocean. Once in the ocean on their way to the spawning area, silver eels probably migrate in the upper few hundred metres, while reproductive maturation continues. Although involvement of a magnetic sense or olfactory cues seems probable, how they navigate or what routes they take are still a matter of speculation. There are few landmarks in the open ocean to define their spawning areas, other than oceanographic or geological features such as oceanic fronts or seamounts in some cases. Spawning of silver eels in the ocean has never been observed, but artificially matured eels of several species have exhibited similar spawning behaviours in the laboratory. Recent collections of mature adults and newly spawned preleptocephali in the spawning area of the Japanese eel Anguilla japonica have shown that spawning occurs during new moon periods in the North Equatorial Current region near the West Mariana Ridge. These data, however, show that the latitude of the spawning events can change among months and years depending on oceanographic conditions. Changes in spawning location of this and other anguillid species may affect their larval transport and survival, and appear to have the potential to influence recruitment success. A greater understanding of the spawning migration and the choice of spawning locations by silver eels is needed to help conserve declining anguillid species. [source]

Previously spawned Atlantic salmon ascend a large subarctic river earlier than their maiden counterparts

JOURNAL OF FISH BIOLOGY, Issue 4 2006
E. Niemelä
Spawning migration timing of maiden Atlantic salmon Salmo salar and previous spawners was analysed in the catches in 1989,2004 in the large subarctic River Teno in the northernmost parts of Finland and Norway. The hypothesis was that the migration timing of previous spawners and their maiden counterparts is similar, with the migration timing similar between sexes. In most cases, however, previous spawners were observed to migrate into the River Teno and its tributaries earlier than their maiden counterparts. The difference in run timing was especially evident between maiden one-sea-winter (1SW) Atlantic salmon and the corresponding group of previous spawners [1S1, 1 year at sea (1) followed by first spawning (S) and reconditioning period of 1 year (1) at sea and second spawning run] for both sexes in the River Teno and in its two tributaries. The same was also evident between 2SW maiden and 2S1 previous spawning female Atlantic salmon in the River Teno. Females showed earlier spawning migration than males both in previous spawners and maiden Atlantic salmon. Different maiden sea-age classes also showed differences in run timing as multi-sea-winter fish (2,4SW) ascended earlier than 1SW fish but the timing of 1S1 and 2S1 previous spawning females coincided. The results suggest that run timing of Atlantic salmon may not be strictly genetically fixed as previous spawners ascend earlier than they did on their first spawning migration as maiden fish, and indicated that the closeness of the reconditioning area of postspawners to the river of origin resulted in an early ascent. Run timing of different sea-age groups has major management implications if the populations are heavily exploited with numerous fishing methods in different periods of the fishing season, as in the River Teno system. [source]

Effects of temperature on disease progression and swimming stamina in Ichthyophonus -infected rainbow trout, Oncorhynchus mykiss (Walbaum)

JOURNAL OF FISH DISEASES, Issue 10 2009
R Kocan
Abstract Rainbow trout, Oncorhynchus mykiss, were infected with Ichthyophonus sp. and held at 10 °C, 15 °C and 20 °C for 28 days to monitor mortality and disease progression. Infected fish demonstrated more rapid onset of disease, higher parasite load, more severe host tissue reaction and reduced mean-day-to-death at higher temperature. In a second experiment, Ichthyophonus -infected fish were reared at 15 °C for 16 weeks then subjected to forced swimming at 10 °C, 15 °C and 20 °C. Stamina improved significantly with increased temperature in uninfected fish; however, this was not observed for infected fish. The difference in performance between infected and uninfected fish became significant at 15 °C (P = 0.02) and highly significant at 20 °C (P = 0.005). These results have implications for changes in the ecology of fish diseases in the face of global warming and demonstrate the effects of higher temperature on the progression and severity of ichthyophoniasis as well as on swimming stamina, a critical fitness trait of salmonids. This study helps explain field observations showing the recent emergence of clinical ichthyophoniasis in Yukon River Chinook salmon later in their spawning migration when water temperatures were high, as well as the apparent failure of a substantial percentage of infected fish to successfully reach their natal spawning areas. [source]

Ichthyophonus -induced cardiac damage: a mechanism for reduced swimming stamina in salmonids

JOURNAL OF FISH DISEASES, Issue 9 2006
R Kocan
Abstract Swimming stamina, measured as time-to-fatigue, was reduced by approximately two-thirds in rainbow trout experimentally infected with Ichthyophonus. Intensity of Ichthyophonus infection was most severe in cardiac muscle but multiple organs were infected to a lesser extent. The mean heart weight of infected fish was 40% greater than that of uninfected fish, the result of parasite biomass, infiltration of immune cells and fibrotic (granuloma) tissue surrounding the parasite. Diminished swimming stamina is hypothesized to be due to cardiac failure resulting from the combination of parasite-damaged heart muscle and low myocardial oxygen supply during sustained aerobic exercise. Loss of stamina in Ichthyophonus -infected salmonids could explain the poor performance previously reported for wild Chinook and sockeye salmon stocks during their spawning migration. [source]

Habitat suitability analysis for lacustrine brown trout (Salmo trutta) in Lake Walchensee, Germany: implications for the conservation of an endangered flagship species

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2010
Marco Denic
Abstract 1.The lacustrine brown trout (Salmo trutta) is endangered and of high conservation importance. In the only spawning habitat of the population in the Bavarian Lake Walchensee, the River Obernach, a substantial decrease in spawning runs has been reported. In this study, the present ecological state of the spawning stream was analysed with the objective of identifying life-stage specific limitations to successful recruitment attributable to deficiencies in (i) spawning migration, (ii) spawning habitat quality, and (iii) habitat quality for juveniles. 2.Structural stream analysis showed that discharge and several migration barriers , particularly near the river outlet into the lake , prevent successful spawning migrations at normal water levels. Migration barriers are probably the main limiting factor for reproduction of lacustrine brown trout, whereas structural variability of the Obernach meets the habitat requirements of both spawners and juveniles. 3.Spawning site quality was suitable for trout, as indicated by stream substratum texture and high exchange rates between free-flowing water and the interstitial zone in physico-chemical parameters (redox potential, dissolved oxygen, pH, temperature and conductivity). 4.Analyses of fish community structure revealed dominance of lithophilic species, in particular of riverine brown trout (Salmo trutta). Its density and intact demographic population structure suggest that spawning and juvenile habitat quality for salmonids is not limiting. Recapture of stocked lacustrine trout juveniles also indicates habitat suitability for the juvenile stage. 5.In conclusion, the results show that the methodology used in this study is suitable for the identification of life-stage specific habitat deficiencies in lacustrine brown trout and other fish species. Availability of habitat data throughout the species' distribution range is a first crucial step for the development of an effective recovery plan. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Visualisation of standardized life-history patterns

FISH AND FISHERIES, Issue 4 2001
Dirk Zeller
Abstract The life-history patterns of fish and invertebrate species are complex. But much of this complexity can be captured in simple diagrams of coastal transects, where juveniles usually occur in larger numbers in shallow waters, while adults generally inhabit deeper, offshore waters. Iconographic representations of generalized life-history patterns and depth profiles, with specific key life-history parameters can capture much of these standardized patterns, including spawning areas, nursery/juvenile distributions, adult distributions and spawning migrations. Several examples presented here from a wide range of habitats and ecosystems (temperate and tropical waters, demersal, deep water, pelagic and coral reefs), including an example of different stocks of the same species, illustrate some general patterns with regard to water depth and distance from shore. The present approach should be viewed as a first step towards obtaining standardized patterns about key life-history parameters, and will hopefully lead to incorporation into management of life-history interconnectivity between different fishery sectors or gears. This may contribute to sustainable, ecosystem-based approaches to management by informing policy options when faced with decisions to rationalize overcapitalized fisheries. [source]

Oceanic migration and spawning of anguillid eels

Energetics and morphology of sockeye salmon: effects of upriver migratory distance and elevation

JOURNAL OF FISH BIOLOGY, Issue 3 2004
G. T. Crossin
Depending on population, wild Fraser River sockeye salmon Oncorhynchus nerka travel distances of <100 km to >1100 km and ascend elevations ranging from near sea-level to 1200 m to reach spawning areas. Populations embarking on distant, high elevation migrations (i.e. Early Stuart, Chilko and Horsefly populations) began their upriver spawning migrations with higher densities of somatic energy (c. 9·2 to 9·8 MJ kg,1) and fewer eggs (c. 3200 to 3800) than populations making shorter, low elevation migrations (i.e. Weaver and Adams; c. 7·1 to 8·3 MJ kg,1 gross somatic energy and c. 4300 to 4700 eggs). Populations making difficult upriver migrations also had morphologies that were smaller and more fusiform than populations making less difficult migrations, traits that may facilitate somatic energy conservation by reducing transport costs. Indeed, fish travelling long distances expended less somatic energy per unit of migratory difficulty than those travelling shorter distances (2·8 to 3·8 kJ v. 10,1400 kJ). Consistent with evolutionary theory, difficult migrations appear to select for energy efficiency but ultimately fish making more difficult migrations produce fewer eggs, even when differences in body length have been accounted for. Despite large among-population differences in somatic energy at the start of upriver migration, all populations completed migration and spawning, and subsequently died, with c. 4 MJ kg,1 of energy remaining, a level which may reflect a threshold to sustain life. [source]

Habitat suitability analysis for lacustrine brown trout (Salmo trutta) in Lake Walchensee, Germany: implications for the conservation of an endangered flagship species

Post-release movements and habitat use of robust redhorse transplanted to the Ocmulgee River, Georgia,

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2009
Timothy B. Grabowski
Abstract 1.Robust redhorse Moxostoma robustum is an imperiled, potadromous fish in the south-eastern USA. Initial recovery efforts have focused on supplementing existing populations and establishing refugial populations through extensive stocking programmes. However, assessment of the success of these programmes has not yet been conducted, and there are few reports evaluating the effectiveness of such programmes with other potadromous species. 2.Radio telemetry was employed to assess the effectiveness of a stocking programme aimed at addressing whether stocked individuals would remain in an area free of introduced predators and ascertaining the ability of stocked fish to integrate into a resident population. 3.Hatchery-reared robust redhorse were captured from refugial populations established in other river systems and were transferred to the Ocmulgee River, Georgia where a population of hatchery-reared individuals and an unknown number of wild fish reside. 4.These transferred robust redhorse exhibited an exploratory phase for the first 3 months before adopting behaviour patterns, including spawning migrations, that were consistent with those reported for wild fish in other systems. However, some individuals seemed unable to locate suitable spawning habitat. 5.Approximately half of the radio-tagged fish remained within the area free of introduced predators. 6.At least some radio-tagged robust redhorse fully integrated into the resident population as evidenced by their presence in spawning aggregations with resident individuals. 7.The effectiveness of a stocking programme is dependent upon the ability of stocked individuals to integrate into an existing population or replicate the behaviour and functionality of a resident population. Evaluations of stocking programmes should incorporate assessments of behaviour in addition to surveys to estimate abundance and survivorship and genetic assessments of augmentation of effective population sizes. Published in 2008 by John Wiley & Sons, Ltd. [source]