Environmental Biology of Fishes最新文献

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.

Microplastics (MPs) are an emerging contaminant potentially impacting organisms and ecosystem functioning. Despite the high abundance of MPs in Guanabara Bay, studies on MP ingestion are lacking. Analyses of 272 stomachs of Micropogonias furnieri, a key estuarine species, revealed that ~ 50% of fish ingested MPs, with an average of 3.7 MPs per individual. Polyester and polyethylene fibers were the dominant types of MPs found in both stomachs and bay sediments. Comparisons of the MP types in the fish stomachs and those previously described in the sediment showed that M. furnieri ingested MPs according to the availability but also exhibited selectivity for some rare MPs (i.e., blue and red fibers). Analyses of M. furnieri stomachs indicated that higher MP ingestion was associated with a larger quantity of food ingested, low digested food items, larger fish, dry season, and two bay locations, suggesting that this species serves as a valuable indicator of feeding area quality. MPs occurred only in stomachs with food, and estimates of egestion rates showed short residence time of food and MPs, indicating no MP accumulation in fish stomachs. The results also revealed that juveniles had more MPs in their stomachs per gram of body weight. MPs did not appear to impact M. furnieri feeding, but the effects of adsorbed chemicals on fish health require further evaluation. As M. furnieri ingests more food, it becomes more exposed to the effects of MPs, highlighting the MP threat to the ecosystem services provided by the bay, such as fish feeding areas.