Environmental Biology of Fishes最新文献

Hatching corresponds to the moment an individual leaves its egg envelope. Yet, hatching has scarcely aroused the interest of biologists, and the question posed here, ‘why do larvae hatch when they do?’ appears to have been rarely asked. In this proof-of-concept study, we tested the hypothesis that fish larvae hatch when a specific ratio between egg surface area (ESA) and larval surface area (LSA) is reached, irrespective of egg diameter and abiotic factors. An estimated mean ratio of 1: 1.52 (CI = 1.39–1.63) was obtained from the eggs of 33 species of teleosts, with diameters ranging from 0.63 to 5.7 mm. We assume that this ratio has a value beyond which the oxygen supply through the egg surface cannot cope with the oxygen requirements of the embryo. The detailed ecological consequences are unknown but can be expected to impact fisheries and aquaculture negatively.

The distinct origin and hydrological characteristics of reservoirs, shaped by fluctuating water levels and seasonal variations, play a crucial role in determining aquatic species assemblages across diverse limnological zones. This study aimed to analyze fish and crayfish assemblages in the nearshore area of a canyon-shaped Mediterranean reservoir, seeking to identify seasonal and spatial convergent patterns and infer the factors influencing them. Samplings were conducted at five stations along the longitudinal profile of the reservoir at depths around 7 m using gillnets and hoops nets. A seasonal pattern emerged regarding species abundance and biomass, with higher values recorded during the warmer period. Additionally, a spatial trend was observed, indicating higher species abundance in the middle part of the reservoir and lower abundance near the dam, particularly during the colder period. Water transparency, temperature, and the distance from the dam were identified as the most significant factors affecting species assemblages in terms of abundance and biomass. This research provides valuable insights into the intricate interplay between environmental factors, seasonal changes, and the assemblages of aquatic species in a Mediterranean reservoir, contributing to our understanding of its ecological dynamics.

Yellow Perch (Perca flavescens) inhabit both nearshore and coastal wetland habitats of the Laurentian Great Lakes throughout their lifetime and are known to exhibit different movement life histories. However, uncertainty persists in the spatial extent of this variation and in the duration of habitat use. To explore these uncertainties, we used a multi-metric approach that included water and otolith microchemistry and tissue stable isotope ratios (δ¹³C, δ¹⁵N). The ratio of manganese to calcium in otoliths was used to identify transitional movements between nearshore Lake Ontario and wetland habitats while carbon and nitrogen tissue isotope ratios revealed variable duration of wetland inhabitance. Our research suggests that the multi-metric approach was useful for addressing questions that could not be answered by one method alone. Our results demonstrate individual differences in duration of coastal wetland habitat residence among Yellow Perch, which may influence their susceptibility to recreational harvest. As Yellow Perch are an important species of consideration for management agencies such as the Great Lakes Fishery Commission, exposing such diversity is important when considering the potential for differential contributions of individuals with variable movement life histories to overall population stability and resilience over time.

Sandy beaches have experienced substantial human modifications worldwide for centuries. Yet, sandy beaches are known as nursery areas for coral reef fishes. Due to global and local stressors, the degradation of nurseries such as the sandy beaches may have wide reaching consequences for the resilience of reef fishes. In our study, the impact of erosion vs. accretion phenomena was highlighted on coral reef fish community in Guadeloupe in comparing the abundance and diversity of juvenile fish between two nearby beach sites (one that undergoes accretion and the other one that undergoes erosion since the 1950s). The main result showed that a significant retreat of sandy beach along the entire coastline, by bringing out an old reef, could create new habitats, favorable to the settlement of fish juveniles. This result is surprising when considering that erosion negatively affects coral reefs through the sedimentation, deterioration of water quality, and loss of habitat.

The striped mullet Mugil cephalus is a species of high commercial value with a spawning season that spans from autumn to winter in coastal areas of the northern Gulf of Mexico. The objective of this project was to study an annual cycle of monthly stages of M. cephalus sexual maturity in two southern Gulf of Mexico localities during 2018, to compare results with those reported for the rest of the Gulf of Mexico, and to analyze the spawning temporality vs. tidal oscillations. Specimens were obtained monthly (January–December 2018) from commercial captures collected in Alvarado Lagoon, Veracruz and Puerto Ceiba, Tabasco. Total length, standard length, and total weight were recorded after the fish were eviscerated and the gonads were separated, and sex, eviscerated weight, gonad weight, and the stage of sexual maturity were recorded. A Gonadosomatic Index was obtained, and the gonads with vitellogenetic development were observed to determine the spawning season. M. cephalus spawns simultaneously in both localities, together with virtually synchronous spawning throughout the Gulf of Mexico, from October to March in northern localities and from December to January in southern areas of the Gulf of Mexico. Meteorological tides produced by the “northers” throughout the Gulf of Mexico seem to trigger spawning migrations. The synchronous spawning of M. cephalus supports the evidence that this is a panmictic population in the Gulf of Mexico.

The Mediterranean region stands as a prominent biodiversity hotspot for the full spectrum of its habitats. However, it ranks among the most extensively invaded regions globally. This characterization aptly applies to the Balkan Peninsula, an expanse renowned for its elevated levels of biodiversity and endemism concerning freshwater fishes. Among the most frequently introduced fauna in the Balkans is the rainbow trout Oncorhynchus mykiss (Walbaum, 1792). Among the regions with very limited information available concerning the species’ distribution in Greece is Mount Olympus. The current study reports the first record of several Oncorhynchus individuals from upstream of Enipeas River. The specimens in view are the first ichthyofauna record for the region. Also, this manuscript discusses the potential introduction vectors. Two different methodologies were used. The first was the use of citizen-science and the second was the use of underwater cameras and systematic surveys at Enipeas River. The estimated depth at sampling stations ranged from 0.5 to 2 m. Trout individuals were found in all sampling stations, estimated at 7–10 cm in length.

As aquatic invasive species spread, their impacts on native systems are variable and important to understand from a management perspective. DNA sequencing and morphological analysis of stomach contents can provide insight into the diet of invasive opportunistic feeders, such as smallmouth bass (Micropterus dolomieu). Since their illegal introduction in 2017, smallmouth bass have proliferated in Cultus Lake, British Columbia and potential impacts on two species-at-risk (sockeye salmon and pygmy sculpin) are currently unknown. Bass (n = 204) were sampled in the spring/summer of 2020–2021 in Cultus Lake. DNA barcoding (n = 145) and visual analysis (n = 204) of diet were completed. Diet composition, factors influencing the predation of species-at-risk, and dietary shifts were analyzed. DNA analysis identified 32 more taxa at the family level than morphological analysis. Multiple logistic regression showed that bass were more likely to predate on Oncorhynchus nerka within the bass spawning grounds, and over 90% of bass had sculpin in their diets. Diet composition did not shift as bass size changed, demonstrating sustained predation on fish from 100 to > 300 mm total length. These results highlight the importance of understanding the potential impacts of an invasive species before investing in suppression to create effective plans and leverage funding opportunities.

Abstract

Freshwater drum (Aplodinotus grunniens Rafinesque, 1819) are found from Canada, through the central United States, and in Atlantic drainages of Mexico and Guatemala. Although populations are broadly distributed, locally abundant, and can produce individuals over 23 kg, the species is often not considered desirable among recreational anglers and, as such, not often studied by researchers. To inform future management of the species, populations occurring at the center of the species latitudinal range, Kansas, United States, were examined. Freshwater drum up to 600 mm were distributed across the eastern 2/3 of the state in variable abundance. Angler surveys at large impoundments from 2015 to 2022 indicated 4.4% of all fish captured were freshwater drum and the species comprised 1.2% of total fish harvest estimated from those surveys. Individual ages were assessed from two populations suggesting individuals as old as age 42 in Glen Elder and age 28 in Tuttle Creek. Instantaneous natural mortality estimates were 0.161 and 0.207 for Glen Elder and Tuttle Creek populations, respectively. Recruitment was variable in both populations but demonstrated similar multiyear cyclical patterns. Harvest modeling suggested recruitment overfishing may start to occur at 10 to 15% angling exploitation under liberal minimum length limits but 20 to 40% under more conservative minimum length limits. Results from this study highlight the status of freshwater drum populations and fisheries at the center of their latitudinal range and provide information that could inform development of species management plans rangewide. Additionally, this study provides a template that can be applied to similar underutilized native species that may be capable of supporting recreational fisheries in a changing future.

In this study, we have examined the effect of hesperidin on rats fed on an experimental high-fat diet. Male Wistar rats were given a high-fat diet orally for one month for developing an HFD (High fat- diet) model. Rats were also supplemented with hesperidin (100 mg/kg body weight) for one month. We determined serum LDL (Low-density lipoprotein) oxidation, Paraoxonase-1 (PON-1) activity, and histopathological profile of the liver. Inflammatory cytokines levels were also measured in serum. HFD induced significant changes in LDL oxidation and PON-1 activity. Liver tissue histopathology and gene expression of inflammatory markers (Il-6(Interleukin-6), TNF- alpha (Tumor necrosis factor alpha), NF-KB (Nuclear factor kappa B) show that significant changes occur in the hyperlipidemic model of rats. We also show that hesperidin can effectively improve plasma antioxidant, LDL oxidation, and inflammatory cytokine expression in rats already subjected to hyperlipidemic stress. We conclude that hesperidin may protect the liver from oxidative stress by improving hepatic function.

Fish communities of tropical lakes are commonly predicted by local environmental variables, including depth, temperature, oxygen concentration, and substrate composition. Increasingly, however, lacustrine fish communities are being impacted by invasive species. In the state of Quintana Roo, on the Caribbean versant of the Yucatan Peninsula in Mexico, inland aquaculture production has resulted in the widespread establishment of African tilapia (Oreochromis sp.). However, there are still limited quantitative data on their abundance relative to indigenous species, or their influence on native fish diversity. Here, we quantified the ichthyofauna of six lakes from this region, alongside physical and chemical environmental variables. Overall, we observed that greater dissolved oxygen concentration and shallower depths were associated with the highest fish biodiversity across lakes. Moreover, spatial comparisons additionally highlighted the importance of substrate heterogeneity and lake area as influential in determining native fish community structure. Notably, in all lakes, tilapia were relatively uncommon, comprising less than 3% of all fish captured, and their presence was not a significant predictor of indigenous fish biodiversity. Based on these results, we suggest that tilapia may have strong limitations on their population size, plausibly due to the presence of predatory native fish species, or scarce suitable ecological resources (food, breeding habitat). Conservation-focussed lake-wide management of native species via protection of core habitat characteristics may be key to promoting environmental resistance against negative effects of tilapia regional expansions.