Environmental Biology of Fishes最新文献

Abstract

A mountain mass from which multiple river basins originate is a possible determinant of genetic structure of freshwater fishes. In this study, subspecies composition and genetic structure were examined for Japanese white-spotted char comprising of two subspecies, Salvelinus leucomaenis imbrius (Jordan and McGregor), “Gogi,” and S. l. pluvius (Hilgendorf), “Nikkoiwana,” collected in the 19 river basins originating from 6 mountain masses in the Chugoku Region, Japan, based on mitochondrial DNA sequences. In the western mountain masses, only Gogi was collected, while in the eastern mountain mass, only Nikkoiwana was collected. A total of 27 haplotypes were detected, among which only seven were shared by two subspecies and three were detected only in Nikkoiwana whereas 17 were detected only in Gogi. As many as 11 haplotypes were distributed only in the Oyorogi Mountain mass in the middle region. In the network, one group was exclusively constructed by the samples from the Oyorogi Mountain mass. Furthermore, in a tree of river basins based on average genetic distance of char, the Gono River basin originating from the Asa Mountain mass, situated in the western region, participated in a clade constructed by the rivers originating from the westernmost Sukegatake and the adjacent Asa Mountain masses, whereas the Gono River basin originating from the Oyorogi Mountain mass participated in a different clade constructed by the rivers originating from the Oyorogi to the easternmost Hyonosen Mountain masses. These results suggest that a mountain mass is a determinative factor to subspecies composition and genetic structure of char, with an implication of invasion of fish taking advantage of some geological events or conditions.

Water pollution imperils the Neosho madtom (Noturus placidus), which is threatened federally and in Kansas. Within Kansas, madtom densities were historically lower in the Spring River compared to the Cottonwood and Neosho Rivers, especially within the Spring River below tributary inputs that delivered cadmium, copper, lead, and zinc pollution from the Tri-State Mining District of Missouri, Kansas, and Oklahoma. Neosho madtom are less numerous in waters containing elevated metal concentrations because of direct toxicity and lower benthic macroinvertebrate (i.e., food) availability. Long-term reductions in metal concentrations in the Spring River have occurred, but no study has examined whether madtom and macroinvertebrate densities have responded to improved water quality. We addressed this question by comparing madtom and macroinvertebrate abundances between the Neosho-Cottonwood system and the Spring River above and below metal pollution inputs. However, madtoms are influenced by environmental factors and anthropogenic stressors beyond mining-derived metal pollution, so we also examined if food availability, local habitat variables, and watershed characteristics were related to madtom densities. We found that madtom and macroinvertebrate population densities in the Spring River below metal pollution were similar to those in the Spring River above metal pollution and the Neosho-Cottonwood River system. Furthermore, macroinvertebrate availability and watershed characteristics were not associated with madtom abundance. However, two local habitat variables (turbidity and depth) were associated with madtom densities, such that an increase in turbidity or decrease in depth resulted in higher madtom densities. Our results highlight the benefits that water quality improvements can have on imperiled stream organisms.

Balanced ecosystems benefit meso and top predators, which help to maintain the quality of the habitat. Thus, the presence of sharks can be considered an indicator of environmental health. Baited remote underwater stereo-videos (BRUVs) were used to assess the relative abundance of sharks in the Alcatrazes Archipelago, Southwestern Atlantic, after an important no-take zone expansion from 12 to 675 km² with the creation of the Wildlife Refuge and enhanced enforcement, comparing our findings with previous BRUV surveys. This study observed sharks in 16 (10.7%) of the 150 stereo-BRUV deployments and recorded seven species (Squalus cf. albicaudus, Carcharias taurus, Carcharhinus plumbeus, Carcharhinus falciformis, Rhizoprionodon porosus, Sphyrna lewini, and Sphyrna zygaena). These data, combined with the perception of frequent and experienced divers (management staff and diving operators) about the increase in shark sightings, suggest a recent positive effect of the no-take zone for these predators and a healthier ecosystem. Results also show that long-term monitoring and effective enforcement of the Alcatrazes Wildlife Refuge are crucial to maintain and enhance the positive effects in the area.

Movement is an important eco-evolutionary process that can shape population and ecosystem structure and function. Accordingly, a firm understanding of species movement ecology is often foundational to effective management and conservation. However, despite movement being an inherently individual-level behavior, there remains a tendency to describe dispersal and migration patterns using simple population-level processes and effects. Overlooking within- and among-individual variation in movement risks incomplete understanding of the intrinsic and extrinsic factors that govern dispersal dynamics and could potentially result in inadequate management of critical behavioral phenotypes. In this study, we monitored movement of over 100 brook trout (Salvelinus fontinalis) and quantified the effect of individual-level traits, season, and their interactions to better understand factors that influence vagility. Our results suggest that movement was higher in fall than in summer, particularly for fish in poor condition. But we found no significant main effects for sex, providing no evidence for sex-biased dispersal. To better understand sources of individual variation, we also allowed for sex- and season-specific residual standard deviations. In doing so, we found that, on average, movement was more variable in fall compared to summer, and that females were more variable than males in vagility. Taken together, these results demonstrate how intrinsic, individual-level traits can interact with abiotic environmental conditions to determine movement. They also highlight the potential for simple explanations of movement ecology to overlook important traits that may help predict individual-level behaviors.

Predation, and the risk of predation, shape the ecology, behavior, and evolution of many species. Small fishes navigate a perilous landscape of risk in the shallow waters of the littoral zone. Moreover, in small lakes, the predator community can be dynamic due to stochastic colonization and extirpation events. These conditions select for the ability by small fish to acquire recognition of novel predators through associative learning. Chemical cues associated with predation events, such as damage-released chemical cues from conspecifics, and the odor of predators, inform prey of the presence of risk, and facilitate acquired recognition of novel predator odor. Deming Lake, MN, is a small meromictic lake with intermittent connections to neighboring lakes in the watershed. Annual sampling of the littoral fish community between the years 2000 and 2023 reveals a history of colonization and extirpation by relatively large-bodied species such as yellow perch Perca flavescens and pumpkinseed sunfish Lepomis gibbosus. Ice cover data, combined with limnological depth profiles of dissolved oxygen, confirm that dissolved oxygen is limiting during the winter and consistent with the hypothesis that extirpation of large-bodied species in Deming Lake is likely due to winter anoxia. These data set the stage for an experimental demonstration of acquired recognition of the odor of allopatric rock bass Ambloplites rupestris by bass-naïve northern redbelly dace Chrosomus eos from Deming Lake. Rock bass have been absent from Deming Lake since at least the year 2000. Predator-recognition learning allows redbelly dace, and many other small-bodied fishes that face variable predator species over ontogenetic, spatial, and temporal scales, a mechanism to adapt quickly to indicators of predation risk.

Abstract

Freshwater ecosystems play a vital role in sustaining human populations; however, these environments are increasingly subject to human interference, driven by land use modifications, species introductions, pollution, and habitat loss. We sampled the ichthyofauna and collected environmental variables from 24 coastal streams in northeastern Brazil. Fish composition, abundance, and biomass served as the response variables, while physicochemical data, hydrological attributes, riparian characteristics, and substrate composition were considered as predictor variables. Our main objective was to evaluate the impact of a riparian land use gradient, ranging from conserved to degraded scenarios (i.e., forested, grassy, and urban streams), on the structure of fish assemblages. To achieve this, the graphical relationship of ABC plots and their W values between the three sets of streams was evaluated, and a Hellinger transformation-based Redundancy Analysis (tb-RDA) was conducted and we compared fish composition among the stream categories using a PERMANOVA test. We identified that the W values of forested and urban streams were significantly different, indicating a shift from k to r-strategists; the tb-RDA revealed three stream categories: (i) forested streams and their association with Anablepsoides bahianus and Parotocinclus cf. jumbo, (ii) grassy streams and their association with Poecilia vivipara and Astyanax cf. bimaculatus, and (iii) urban streams and their relationship with Poecilia reticulata and Oreochromis niloticus. We also found important differences between fish composition along the riparian land use gradient, with urban streams showing a significant divergence from grassy and forested streams. We observed a loss of native species and an introduction of exotic species in the evaluated gradient, consistent with the premises of niche theory.