Ecology of Freshwater Fish最新文献

Metacommunity theory seeks to explain how local and regional processes contribute to the organisation of biological communities. Recent conceptual frameworks of this theory indicate that the dynamics of populations and communities are jointly established by dispersal, species responses to environmental conditions and biotic interactions dependent on species density. Here, we use hierarchical joint species distribution modelling to verify the effects of environmental factors (at multiple spatial scales), drainage network configuration, spatial autocorrelation and interspecific interactions on the structure of fish assemblages in terra-firme streams in the Eastern Brazilian Amazon. Thirty streams were sampled in two field surveys, and 89 species were collected in total. Our results confirm the effects of limited dispersal, environmental conditions (at multiple scales) and the configuration of the drainage network on the dynamics of these assemblages. Furthermore, our results suggest that interspecific interactions are less relevant for the structuring of fish metacommunities in small Amazonian headwater streams. Abiotic factors like drainage networks and environmental heterogeneity were better predictors of species distributions than co-occurrence patterns with potential competitors or predators.

Diet plasticity is often studied in Eurasian perch (Perca fluviatilis), a species commonly described as having generalist populations composed of specialised individuals. Perch diet was examined using gut content analysis (GCA) and stable isotope analysis (SIA), and individual specialisation was calculated in two study lakes within 2 years. Mostly only one diet category was present in the perch stomach, with more variation in the diet in the Most lake compared to the Milada lake between 2013 and 2014. The calculated degree of individual specialisation indicated higher specialisation in the Most lake. Interestingly, despite the different or almost uniform diet composition between the years, the total niche width (based on SIA) of the population remained similar in both lakes. This suggests that the overall variation in the sources utilised by the entire population remained consistent between the years. GCA mostly indicated zooplankton as the prevailing food source, whereas SIA indicated significant utilisation of YOY fish earlier that year, an information that was completely missed by the GCA of fish caught in September. The differences between GCA and SIA results could be attributed to the different time intervals reflected by the methods, but possibly to the conversion of the diet into the body tissues that is reflected by SIA and may depend on the diet's nutritional values rather than the proportion of different prey consumed.

In partially migratory species, individuals either migrate at some point(s) in life or reside within their natal habitat throughout life. For salmonid fish, migration creates opportunities for feeding and growth, but it is also associated with increased mortality risk. Such trade-offs likely differ between the sexes, since reproductive output is more closely tied to body size in females than males. However, testing hypotheses on sex-specific migratory behaviour in would-be first-time migratory salmonids is difficult, since sexes are generally morphologically indistinguishable prior to maturation. Previous studies have evaluated the influence of sex on migration based on dissection of migratory juveniles or the sex ratio of returning adults. However, both approaches are potentially biased by differential survival during migration. Here, we utilise advances in minimally invasive genetic sex-determination methods for salmonids to investigate sex-specific, spring out-migration propensity in potamodromous brown trout (Salmo trutta) in a pre-Alpine, central European lake. We show that there are marked differences in migratory behaviour between males and females, with small (~10 cm) females being approximately twice as likely to migrate out of their natal river in spring compared to similarly sized males, which generally migrate for the first time at larger sizes (in similar proportions to larger females). This study highlights how novel genetic sex-determination techniques can provide insight into the sex- and size-specific life-history trade-offs that shape migration propensity. Moving forward, these techniques should become useful tools for ecologists and fisheries managers.

We compared abundance patterns and developed resource selection models for imperilled native southwestern (USA) fishes in the presence and absence of Black Bass (Micropterus spp.) to evaluate how fishes alter their selection for habitats when sympatric with a nonnative piscivore. We collected data using snorkel surveys and in-stream habitat sampling in Fossil Creek (AZ), upstream (native fish only) and downstream (native and nonnative fish) of a fish barrier. The abundance of all Roundtail Chub (Gila robusta), small (≤127 mm total length [TL]; vulnerable to predation) Sonora Sucker (Catostomus insignis) and Speckled Dace (Rhinichthys osculus) was significantly reduced, but the abundance of both small and large (>127 mm TL; invulnerable to predation) Desert Sucker (Catostomus clarkii) was similar in sampling reaches with and without Black Bass. When sympatric with Black Bass, small Roundtail Chub increased their selection for riffles by 2.57 times and small Desert Sucker reduce their selection for pools by 6.90 times while also selecting for faster flow velocity and finer substrates in lotic mesohabitats. Large native fishes altered selection least, notwithstanding an increased selection for canopy cover in sampling reaches with Black Bass. Observed shifts in resource selection are consistent with predator avoidance strategies. Our study highlights the behavioural consequences of nonnative piscivores on native fish communities and stresses the importance of maintaining lotic mesohabitats as potential refugia for vulnerable native fishes when nonnative piscivores are present.

Bull trout (Salvelinus confluentus) research has historically focused on highly impacted systems or occurred in a reactionary manner following overharvest. Here, we used telemetry and multi-state capture–recapture modelling to inform management decision-making for this highly migratory, conservation-listed species in British Columbia's upper Fraser River watershed (UFW). Our work reduced critical information gaps surrounding the seasonal migration patterns, distribution, and survival rates of fluvial bull trout within the region. By using results of an existing microsatellite DNA analysis, we were able to assign each tagged individual to one of five spawning populations. This assignment allowed us to investigate potential differences in migratory behaviour and seasonal habitat use among the different spawning populations. We identified that the majority of tagged UFW fluvial bull trout made repeated, long-distance migrations (>300 km one direction) to appropriate spawning, overwintering and foraging habitats. The five populations did not vary in their seasonal transition probabilities at the spatial scale investigated, suggesting key habitats are important to multiple populations. We also detected post-spawning migration and distribution patterns that suggest UFW bull trout exploit seasonal resource pulses during salmon smolt outmigration. Our results highlight the importance of protecting, restoring and maintaining a diverse assemblage of complex habitats and the natural connections between them (e.g. between tributary spawning habitats and larger rivers) at a spatial scale that supports migratory bull trout life histories. This work provides valuable information for prioritizing conservation actions and identifying restoration opportunities both in the UFW and across the species' range.

Studies relating to fish trophic ecology provide important insights regarding their life history. However, there is a lack of information linking fish diet composition with riparian cover in small streams. To investigate whether diet composition varied between streams with pristine and logged forests, I compared the food items consumed by four characid species: Bryconops melanurus, Moenkhausia collettii, Moenkhausia dichroura, and Moenkhausia oligolepis. I sampled 18 first-order streams in the eastern Amazon: six with pristine forest, six with conventional logging, and six with selective logging. All fish species were classified as omnivorous, with diverse food categories recorded in their diets: mainly terrestrial insects for Moenkhausia species and aquatic insect nymphs for B. melanurus. However, the relative importance of each category varied only in streams with conventional logged forests. In these streams, all fish species consumed mainly autochthonous items, especially aquatic insect nymphs. In addition, terrestrial insects and seeds were absent in these streams with reduced riparian cover. In summary, this study highlighted that fish diet in conventional logged forests strongly differed from areas with pristine and selective logged forests. This finding states that managed forests may support a diverse diet for fish community, similar to that found in pristine forests. Therefore, management and conservation strategies of riparian vegetation in Amazonian streams are important to maintain habitat and food quality, which may be associated with a diverse diet for fish species.

Fish movement in freshwater streams is often tied to patterns of flow, especially when the stream is intermittent, flashy, or some combination thereof. Relationships between flow and fish movement are exacerbated in small urban streams in impervious surface-dominated watersheds that lead to extreme flow conditions. Here we examined the response of Creek Chub (Semotilus atromaculatus), a common pioneer fish species in eastern North America, to flow events of various sizes in a small intermittent urban headwater stream. Our primary goals were to determine (1) the level of Creek Chub movement occurring in an intermittent headwater stream, (2) the influence of flow on movement direction and magnitude, (3) the degree of variation in individual movement behaviour, and (4) mortality rates in the system. The study used PIT tagging and telemetry surveys to monitor Creek Chub movement over a six-month period. We found that individual Creek Chub in our study system were generally mobile (71%), but usually moved short distances only; however, a few individuals moved much farther, with a maximum single movement of 521 m. Moderate or major flow events increased the probability and magnitude of Creek Chub movement, but there was no detectable asymmetry towards upstream or downstream directionality. Movement was variable among individual fish and fish were able to respond to large and small flow events to move among habitats. Finally, we observed relatively high, but episodic, mortality in our study site, potentially related to pollution events. Evidence of elevated mortality points to the potential importance of movement in highly disturbed streams, as it may enable recolonization after local extirpation.

The distribution of Phalloceros species is generally allopatric and restricted; however, Phalloceros harpagos has a wide distribution and exhibits morphological variation among populations from different Brazilian river basins. Different species delimitation tests using cytochrome C oxidase subunit I gene sequences indicated that P. harpagos is a species complex that comprises between 7 and 9 phylogroups. The separation of the Paraná and Paraíba do Sul River basins most likely caused the diversification of these phylogroups in the Miocene period. The majority of phylogroups have a narrow distribution; however, one phylogroup has a broad distribution, being found primarily in the Paraná, Ribeira de Iguape, and Iguaçu River basins. This distribution can be attributed to possible headwater capture events caused by the reactivation of faults and erosion in the quaternary. Estimates about the times of divergence based on molecular data could be used to infer the biogeographic processes related to the diversification of South American freshwater fish.

The diel distribution of early juvenile fish communities from two temperate freshwater reservoirs that differed in cover of submerged aquatic vegetation was investigated. In the daytime, about 99.9% of the juvenile fish community from the plant-rich Žlutice Reservoir was found in the nearshore belt of submerged aquatic vegetation reaching an average abundance of ~7982 inds. 1000 m⁻³. In contrast, in the pelagic habitat, few fish were found at day. In the plant-poor Římov Reservoir, 98.9% of juveniles occupied the pelagic habitat during daytime and reached an average abundance of ~333 inds. 1000 m⁻³. Vertical distribution of fish in the pelagic habitat in both water bodies was affected by steep thermal and oxygen stratification and no individuals occurred below 6 m depth. At night, 88.8% of the juvenile fish community from the plant-rich Žlutice Reservoir was in the pelagic habitat with an average abundance of ~1423 inds. 1000 m⁻³. Their diel horizontal shifts were much more pronounced compared to the community from the Římov Reservoir that reached an average nighttime pelagic abundance of ~523 inds. 1000 m⁻³. Only 1.1% of the juvenile fish community in the Římov Reservoir was found in the littoral during the daytime and 0.7% at night reaching an average daytime abundance of ~1688 inds. 1000 m⁻³ and average nighttime time abundance of ~1664 inds. 1000 m⁻³. This study indicates that if a well-developed littoral zone with abundant aquatic vegetation is present, early juvenile fish will perform diel horizontal movement in temperate stratified reservoirs.