Environmental Biology of Fishes最新文献

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.

The population decline of the endangered bitterling species, Acheilognathus typus, following non-native bitterling invasion underscores the need to understand interspecific interactions among bitterling fishes. In this study, the dietary habits of A. typus, alongside introduced non-native bitterling species (Acheilognathus rhombeus and Rhodeus ocellatus ocellatus) and other omnivorous fishes (Oryzias latipes, Pseudorasbora parva, and Rhinogobius sp.), were investigated in a small pond in Japan using gut content and stable isotope analyses (δ¹³C and δ¹⁵N). Analysis revealed that microalgae, particularly diatoms with periphytic or benthic life forms, dominated the gut contents of the three bitterling species, which exhibited high dietary overlaps (Pianka’s index range 0.89–0.98). Although bitterling species displayed similar δ¹³C (mean range −18.4 to −16.1‰) and δ¹⁵N (12.1 to 12.6‰) values, the other omnivorous fishes exhibited distinct isotopic signatures: lower δ¹³C and higher δ¹⁵N values. Isotopic niche overlaps among the three bitterling species were limited (0–2.4%). Furthermore, A. typus and A. rhombeus showed no overlap in the corrected standard ellipse area. These findings suggest that the three bitterling species may forage on similar food items, primarily microalgae, with differing stable isotope ratios, enabling them to partition foraging sites within the confines of a small pond where competition may arise.

Abstract

Fish select habitat based on many abiotic and biotic factors, with some species having narrow habitat requirements due to morphological traits. Fish of the genus Ammodytes (sand lance) are small schooling pelagic forage fish that lack a swim bladder and burrow into sandy substrate when not actively feeding to avoid predation and reduce energy expenditure. Sand lance species in the Pacific and Northeast Atlantic show diel shifts in feeding in the water column and burrowing, but diel patterns for species in the Northwest Atlantic remain unclear. The objectives of this study were to investigate sand lance habitat characteristics and diel behaviour during July–August 2013–2021 on the northeast Newfoundland coast. Integrating underwater camera surveys, sediment grabs, and hydroacoustics, sand lance were found associated with fine sediment (0.5–4 mm) that were < 11˚C (typically ~ 2˚C). Acoustic sand lance biomass in the water column tended to decline between the morning (09:00 Newfoundland Daylight Time, NDT) and late evening (23:00 NDT), while fish densities in sediment grabs peaked during the evening (~ 19:00 NDT) when buried fish more commonly had non-empty stomachs. Findings suggest that sand lance primarily fed in the water column during the day and burrowed in the evening once stomachs were full. Diel patterns were size-dependent, with a higher proportion of larger sand lance (≥ 150 mm) caught in sediments throughout the night, when smaller sand lance (< 150 mm) were absent from sediments. Overall, sand lance species in the Northwest Atlantic appear to exhibit similar habitat requirements and diel patterns to those in other regions.

Lake sturgeon (Acipenser fulvescens), a potamodromous species, have been impacted by habitat fragmentation. Understanding the variation in population structure and spatial distribution in regulated and unimpeded rivers is valuable for recovery or rehabilitation purposes. The objectives of this study were to assess the relative abundance and spatial distribution of lake sturgeon in Rainy River and ascertain demographics of inhabitant juveniles. A standardized, index-netting study was conducted in the Rainy River to target juvenile and adult lake sturgeon. A total of 472 juvenile and 56 adult lake sturgeon were sampled. Juvenile and adult lake sturgeon were found throughout the river; however, juvenile relative abundance was greatest in the lowest river section close to the confluence with Lake of the Woods. Spatial clustering of juveniles and to lesser extent adults was also evident but adults were not necessarily segregated from juveniles. Juvenile annual survival rates were estimated to be approximately 75% and recruitment within this population was detected in all years but was variable in size. There were strong and weak year classes produced; however, they could not be explained by any of the environmental variables assessed.